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Monitoring and mapping of atmospheric deposition can be achieved by use of chemical transport models, technical sampling devices and/or bio-accumulators such as mosses, lichens, etc. Within the European Moss Survey programme, since 1990 every 5 years mos specimens have been collected and analysed for heavy metals, nitrogen and persistent organic pollutants according a harmonised methodology. Calculation and geostatistical mapping of percentile statistics of element concentration in moss is in the focus of this paper. Thereby, element- and survey-specific as well as heavy metals and surveys integrating statistical evaluations and GIS-mapping were performed. Cr, Sb and Zn show contrary to Fe and Pb, no constant decrease of element concentrations, but an intermediate increase between 2000 and 2005, which did not continue until 2015. Cd, Hg, Pb and N which are of priority according to the Convention on Long-Range Transboundary Air Pollution are in focus in this paper. Additionally, Cr is regarded as representing those elements with an intermediate increase between the years 2000 and 2005 as is also true for Sb and Zn. Surveys integrating percentile statistics depict the spatial patterns of, in most cases, declining element concentrations across time. Survey-specific statistical analyses corroborate that the spatial patterns of element concentrations in moss are changing element-specifically across time. The long-term information on the percentile statistics of bioaccumulation of atmospheric deposition in moss is essential for further scientific evaluation as well as for measurements and reporting of nature protection and environmental management. [ABSTRACT FROM AUTHOR]

In this study, dry deposition samples were collected with both an aerodynamically smooth water surface (WSS) and a knife-edge surrogate surface (KSS) in Potsdam, NY, Solomons, MD, and at a farm in upstate NY intermittently between March 2000 and August 2001. The WSS and the citric acid-coated paper filter on the KSS were used to measure total ammonium deposition (NH3 and p-NH4+), while a greased Mylar disk on the KSS was used to measure particulate NH4+ (p-NH4+) deposition. An annular denuder system (ADS) was used to measure NH3 gas phase and particulate NH4+ concentrations. In side-by-side experiments with two WSSs, no statistical difference was found between simultaneously measured total ammonium deposition at any of the sites. Average total NH3 fluxes measured with the WSS in Potsdam, Solomons, and at the farm were 3.1, 2.1, and 310 mg NH4+ m−2 day−1, respectively. Similarly gaseous NH3 fluxes measured with the citric acid-coated paper on the KSS were 3.6, 2.1, and 500 mg NH4+m−2 day−1, respectively. The p-NH4+ fluxes to the KSS-greased strip were negligible at all three locations. Fluxes measured by the citric acid paper filters were slightly greater than those measured with the WSS suggesting that the acidic dry surfaces had a higher affinity for ammonia than the water in the WSS.The average gas-phase ammonia concentrations in Potsdam, Solomons, MD and at the farm were 0.60×10−3, 2.1×10−3, and 0.25 mg NH4+ m−3, respectively. The average ammonium concentrations were 0.50×10−3, 1.2×10−3, and 14×10−3 mg NH4+ m−3, respectively. [Copyright &y& Elsevier]

In a publication in Atmospheric Environment ( http://dx.doi.org/10.1016/j.atmosenv.2015.10.081 ), Gu et al. (2015) estimated that “the total nitrogen (N) deposition in 2010 was 2.32 g N m −2 yr −1 ” in China. This value is comparable with previous estimations based on a synthesized dataset of wet/bulk inorganic N deposition observations, which underestimates the total N deposition since their algorithm (equations (2) and (3) in their paper) does not account for dry deposition of NH 3 , HNO 3 , NO x and wet/dry deposition of HONO and organic nitrogen (e.g. amines, amides, PAN). Indeed, Gu et al. (2015) mixed the terminology of wet/bulk deposition and total deposition. Another flawed assumption by Gu et al. (2015) is that all inorganic N in precipitation estimated by their algorithm originates from fertilizer and coal combustion. This is incorrect and almost certainly causes biases in the spatial and temporal distribution of estimated wet/bulk inorganic N deposition (Fig. 5 in their paper), further considering the fact that they neglected important N sources like livestock and they did not consider the nonlinearity between various sources and deposition. Besides the input data on N deposition, the model validation (Sect. 2.3.2) described in their paper also requires clarification because the detailed validation information about the time series of observational dataset versus modeling results was not given. As a result of these combined uncertainties in their estimation of N deposition and the lack of detail for model-measurement comparison, their estimates of the impacts of N deposition on carbon storage in Chinese forests may need further improvement. We suggest the clarification of the terminology regarding N deposition, especially for wet deposition, bulk deposition, gaseous and particulate dry deposition or total deposition since the accurate distinction between these terms is crucial to investigating and estimating the effects of N deposition on ecosystems. [ABSTRACT FROM AUTHOR]

South Africa is the economic hub of southern Africa and is regarded as an important source region of atmospheric pollutants. A nitrogen dioxide (NO 2 ) hotspot is clearly visible from space over the South African Mpumalanga Highveld, while South Africa is also regarded as the 9th largest anthropogenic sulphur (S) emitting country. Notwithstanding the importance of South Africa with regard to nitrogen (N) and S emissions, very limited data has been published on the chemical composition of wet deposition for this region. This paper presents the concentrations of sodium (Na + ), ammonium (NH 4 + ), potassium (K + ), calcium (Ca 2+ ), magnesium (Mg 2+ ), nitrate (NO 3 − ), chloride (Cl − ), sulphate (SO 4 2− ) and water-soluble organic acids (OA) in the wet deposition samples collected between 2009 and 2014 at four South African IDAF (IGAC DEBITS Africa) sites, which are regarded as regional representatives of the north-eastern interior. Also, wet deposition fluxes of the ten ions are calculated and presented in this paper. The results show that the total ionic concentrations and fluxes of wet deposition were much higher at the two sites closer to anthropogenic emissions, while the pH of wet deposition at these two sites were lower compared to that of the two sites that were less impacted by anthropogenic emissions. . The major sources of the ten ions included marine, terrigenous (crust), fossil fuel combustion, agriculture and biomass burning. Significant contributions from fossil fuel combustion were determined for the two sites in close proximity to anthropogenic source regions. The results of back trajectory analysis, however, did indicate that the two remote sites are also affected by air masses passing over the source region through anti-cyclonic recirculation. The largest contributions at the two sites distant from the anthropogenic source regions were marine sources, while the impact of biomass burning was also more significant at the remote sites. Comparison to previous wet deposition measurements at the South African IDAF sites indicated increases in the wet deposition fluxes of S and N, and more wet deposition events with lower pH. This could be ascribed to a significant increase in anthropogenic activities and population growth in this part of South Africa with an associated increase in energy demand. [ABSTRACT FROM AUTHOR]

Deposition of pollutants by cloud water exceeds deposition by precipitation and dry deposition in many high elevation settings. This larger loading of pollutants in these environments is due to a combination of factors such as high frequency of cloud immersion, high wind speeds, orographic enhancement of precipitation, and large leaf area of tree species typical in these environments. Fog-impacted coastal ecosystems also experience increased pollutant deposition similar to cloud-impacted high elevation sites. Therefore, development of meaningful critical load values and total nitrogen budgets for high-elevation and fog-impacted sites requires reliable cloud and fog water deposition estimates. The cost and labor intensity of cloud/fog water sample collection have made it difficult to conduct long-term studies that would provide the data needed to develop accurate estimates. Current understanding of fog formation, transport, and the role of fog and cloud deposition in hydrogeological and biogeochemical cycles is incomplete due, in part, to lack of a concerted interdisciplinary approach to the problem. Historically, these obstacles have limited interest in and collection of cloud and fog water samples. In addition to measurements of cloud/fog chemical composition, documenting fog/cloud deposition fluxes of pollutant and nutrient species requires knowledge of cloud/fog physical properties, frequency and duration of fog/cloud interception with landscapes, properties of vegetation on those landscapes, and properties of the wind that drive droplet/vegetation interactions. Because drop deposition efficiency is dependent on drop size, it is also important to consider variations in fog/cloud drop composition with drop size as species enriched in larger/smaller drops will experience enhanced/reduced deposition rates. This paper presents summary results from a small U.S. cloud water monitoring network that operated from the mid-nineties through 2011, as well as a brief qualitative review of other cloud and fog water studies conducted in the United States (including Puerto Rico), Europe, South America/Pacific, and Asia. Current collection methods are also reviewed. Recent scientific efforts by the National Atmospheric Deposition Program's (NADP) Total Deposition Science Committee and NADP's Critical Loads of Atmospheric Deposition Science Committee have identified occult (cloud/fog) deposition as a "need" in developing critical loads for ecosystems that experience significant cloud and fog impaction. To this end, remaining knowledge gaps and suggestions for future research to investigate these gaps are explored. • At elevations above 800m cloud water samples are usually 5–20 times more acidic than rainwater. • Impacts of N deposition on alpine/subalpine regions are numerous and substantial. • Deposition loads of 10–40 kg N/ha/year in high-elevation areas in the eastern US are much higher than in the west. • Productivity and species shifts may have already occurred in eastern alpine ecosystems. • This paper is a qualitative summary of existing knowledge on cloud/fog water deposition. [ABSTRACT FROM AUTHOR]

Sixty rainwater samples were collected covering four seasons from July 2020 to April 2021 from the center of Chongqing, a metropolitan city of southwest China, using automatic deposition sampler. The samples were analysed for 17 targeted poly- and per-fluoroalkyl substances (PFASs) by HPLC-MS/MS. The concentration of PFASs ranged from 3.31 ng/L to 196.14 ng/L and dominated by perfluoro-n-octanoic acid (PFOA), perfluoro-n-hexanoic acid (PFHxA), perfluoro-n-butanoic acid (PFBA) and sodium perfluoro-1-octanesulfonate (PFOS). The seasonal variations of dissolved and particulate PFAS were distinct, with the highest level in summer and autumn, respectively. Positive matrix factorization (PMF) and a wet deposition model were performed to apportion the sources and estimate the wet deposition flux of the 17 PFASs, respectively. PMF analysis indicated that, based on yearly average, paper packaging production (37.4%) and aqueous film forming foam (AFFF) usage (29.8%) were the two major sources, followed by textile production (16.7%) and electronic product manufacturing (16.1%). The highest source contributor for PFASs in winter was AFFF usage (47.0%); while in the other three seasons, it was paper packaging production that contributed the most (50.1%, 39.8% and 34.8% respectively). Seasonal average wet deposition flux of PFASs was estimated to be 13.9 ng/m2/day. The dry deposition of PFASs was estimated to account for 15.8% of the total atmospheric deposition flux, suggesting a more important role for wet deposition. The results of this study provide important information for understanding of PFASs occurrence and atmospheric wet deposition in Chongqing, and other urban centers across China. [Display omitted] • The dissolved and particulate PFASs in rainwater was 20.3 ng/L and 4.39 ng/L, respectively. • PMF identified paper packaging production was the major sources. • The average wet deposition flux of PFASs was estimated as 13.9 ng/m2/day. [ABSTRACT FROM AUTHOR]

Abstract In the framework of the INDAAF (International Network to study Deposition and Atmospheric chemistry in AFrica) programme, part of the ACTRIS European Research Infrastructure for the long-term observation of Aerosols, Cloud, and Trace gases, this paper aims to study trends and seasonal variability of surface atmospheric NO 2 and HNO 3 concentrations, and OMI (Ozone Monitoring Instrument) NO 2 over 6 sites in tropical Africa. Sites are located in west and central Africa to represent the major African biomes: dry savanna (Banizoumbou, Niger and Katibougou, Mali), wet savanna (Djougou, Benin and Lamto, Côte d'Ivoire) and forest (Bomassa, Republic of Congo and Zoétélé, Cameroon). Ground-based NO 2 and HNO 3 concentrations were obtained over the period 1998–2015 using INDAAF passive samplers at a monthly basis, and NO 2 Vertical Column Densities (VCDs) from OMI for a 1° grid cell around each sites were obtained from 2005 to 2015. Mean annual NO 2 concentrations ranged from 2.3 ± 1.2 to 0.9 ± 0.4 ppb from dry savannas to forests, representing a north south gradient. In dry savannas, we observe two concentration peaks of NO 2 appearing at the beginning and the end of the wet season both for ground-based and satellite measurements, whereas at wet savannas and forest sites, NO 2 concentrations are highest in the dry season. The seasonality of surface NO 2 observations provide further evidence for a large role of microbial soil NOx emissions in dry savannas and of biomass burning NOx emissions in wet savanna and forest sites. Mean annual HNO 3 concentrations ranged from 0.4 to 0.5 ppb in dry and wet savannas to 0.2–0.3 ppb in forest. In dry ecosystems, higher HNO 3 concentrations are measured in the early wet season, consistent with NO 2 results. The analysis of a long-term dataset of surface O 3 concentrations indicates that HNO 3 production can mainly be explained by the photooxidation of NO x. Mann-Kendall and Seasonal Kendall statistical tests showed that NO 2 surface concentrations have a significant decreasing seasonal and annual trends at multiple sites (p-value < 0.05) ranging from −2.96% yr−1 (at Zoétélé) to −0.64% yr−1 (at Banizoumbou). HNO 3 results indicate no trends except at Bomassa (1.07% yr−1). The decreasing NO 2 ground-based concentration trends observed in wet savannas sites are correlated with OMI NO 2 decreasing trends at these sites. Trends obtained for NO 2 concentrations in wet savanna and forest ecosystems are consistent with trends of NOₓ biomass burning emissions. Highlights • Long term data of surface and column nitrogenous gases from major African biomes. • North-South latitudinal negative gradient in surface concentrations of NO 2 and HNO 3. • Microbial soil emissions of NOₓ are predominant in dry savannas. • Biomass burning emissions of NOx are predominant in wet savanna and forest sites. • NO 2 annual and seasonal decreasing trends at most of west and central Africa sites. [ABSTRACT FROM AUTHOR]

Abstract The Great Lakes Region of the US continues experiencing exceedances of the ozone (O 3) standards, despite years of emissions controls. In part, this is due to interactions between emissions from surrounding large cities (e.g., Chicago) and meteorology, which is heavily influenced by the presence of the Great Lakes. These complex meteorology-emissions interactions pose a challenge to fully capture O 3 dynamics, particularly near shores of the lakes, where high O 3 levels are often experienced. In a simulation with the Community Multiscale Air Quality (CMAQ) model, using inputs as typically constructed, the model tends to be biased high. A literature review indicated that NO x emissions from mobile sources, possibly overestimated in the 2011 National Emission Inventory (NEI), or the version of the Carbon Bond chemical mechanism used in CMAQ could be responsible for high biases of O 3. As such, a series of sensitivity tests was conducted to identify potential causes for this bias, including emissions biases (e.g., biogenic VOCs, anthropogenic NO x), chemical mechanism choice, and O 3 dry deposition to fresh water, for high O 3 periods in July 2011. The base model/emissions configuration used the following: Carbon Bond mechanism CB05, biogenic emissions using Biogenic Emission Inventory System (BEIS), and anthropogenic emissions from the 2011 National Emissions Inventory (NEI). Meteorological inputs were developed using the Weather Research and Forecasting (WRF) model (version 3.8.1). Simulated daily maximum 8-h average O 3 without and with a cutoff of 60 ppb (referred to as MDA8 O 3 and elevated MDA8 O 3 hereafter, respectively) were evaluated against measurements. The evaluation showed a high bias in MDA8 O 3 across the domain, particularly at coastal sites (by ∼6 ppb), while elevated MDA8 O 3 (i.e., greater than 60 ppb) was biased low, with exceptions centered along the shore of Lake Michigan. Using the CB6 chemical mechanism or 50% reduction of NO x emissions from on-road mobile sources led to substantial domain-wide decreases in O 3 from the base case, and the model performance improved, particularly along the Lake Michigan shoreline and for the western domain. However, elevated MDA8 O 3 was more biased against measurements, compared to the model performance in the base case, except at a few sites along the shoreline. Using the Model of Emissions of Gases and Aerosols from Nature (MEGAN) instead of BEIS to estimate biogenic emissions, or increasing dry deposition of O 3 to fresh water by a factor of ten (which is unrealistic), had minor impacts on simulated O 3 over land. But, combining MEGAN with CB6 resulted in improved elevated MDA8 O 3 simulation along the western coast of Lake Michigan. Finally, using CB6 combined with a 30% reduction of on-road mobile NO x emissions and MEGAN led to the best performance. Two companion papers investigate how meteorological modeling can be improved. Together, the recommended modeling system could serve as a starting point for future O 3 modeling in the region. Highlights • Daily maximum 8-h O 3 is significantly overestimated along Lake Michigan coast. • Elevated daily maximum 8-h O 3 (>60 ppb) is biased low except at coastal sites. • Uncertainties in on-road mobile NO x emissions impact simulated daytime O 3. • Carbon Bond 6 (CB6) mechanism leads to lower O 3 than Carbon Bond V (CB05). • Biogenic emissions and dry deposition over water had minor effects on simulated O 3. [ABSTRACT FROM AUTHOR]

Abstract: Wind-driven rain (WDR) is an important factor in the dry and wet deposition of atmospheric pollutants on building facades. In the past, different calculation models for WDR deposition on building facades have been developed and progressively improved. Today, the models that are most advanced and most frequently used are the semi-empirical model in the ISO Standard for WDR assessment (ISO), the semi-empirical model by Straube and Burnett (SB) and the CFD model by Choi. This paper compares the three models by applying them to four idealised buildings under steady-state conditions of wind and rain. In each case, the reference wind direction is perpendicular to the windward facade. For the CFD model, validation of wind-flow patterns and WDR deposition fluxes was performed in earlier studies. The CFD results are therefore considered as the reference case and the performance of the two semi-empirical models is evaluated by comparison with the CFD results based on two criteria: (1) ability to model the wind-blocking effect on the WDR coefficient; and (2) ability to model the variation of the WDR coefficient with horizontal rainfall intensity Rh. It is shown that both the ISO and SB model, as opposed to the CFD model, cannot reproduce the wind-blocking effect. The ISO model incorrectly provides WDR coefficients that are independent of Rh, while the SB model shows a dependency that is opposite to that by CFD. In addition, the SB model can provide very large overestimations of the WDR deposition fluxes at the top and side edges of buildings (up to more than a factor 5). The capabilities and deficiencies of the ISO and SB model, as identified in this paper, should be considered when applying these models for WDR deposition calculations. The results in this paper will be used for improvement and further development of these models. [Copyright &y& Elsevier]

Abstract: Water soluble organic nitrogen (WSON) compounds are ubiquitous in precipitation and in the planetary boundary layer, and therefore are a potential source of bioavailable reactive nitrogen. This paper examines weekly rain data over a period of 22 months from June 2005 to March 2007 collected in 2 types of rain collector (bulk deposition and “dry + wet” deposition) located in a semi-rural area 15 km southwest of Edinburgh, UK (N55°51′44″, W3°12′19″). Bulk deposition collectors are denoted in this paper as “standard rain gauges”, and they are the design used in the UK national network for monitoring precipitation composition. “Dry + wet” deposition collectors are flushing rain gauges and they are equipped with a rain detector (conductivity array), a spray nozzle, a 2-way valve and two independent bottles to collect funnel washings (dry deposition) and true wet deposition. On average, for the 27 weekly samples with 3 valid replicates for the 2 types of collectors, dissolved organic nitrogen (DON) represented 23% of the total dissolved nitrogen (TDN) in bulk deposition. Dry deposition of particles and gas on the funnel surface, rather than rain, contributed over half of all N-containing species (inorganic and organic). Some discrepancies were found between bulk rain gauges and flushing rain gauges, for deposition of both TDN and DON, suggesting biological conversion and loss of inorganic N in the flushing samplers. [Copyright &y& Elsevier]

This paper presents salinity data of marine aerosols in a Brazilian coastal area at sites closer to the shore and discusses the influence of wind regime. Results show that measurements of marine salt deposition are strongly influenced by wind speeds above the critical value of 3.0ms−1. Although there is no agreement in literature yet as to how much this threshold is, the level of 3.0ms−1 is similar to the one found in a study carried out in Spain. An exponential variation of salt concentration with wind speed is presented in previous published papers. However, in the studied case, another relationship is proposed, which is based on chloride deposition on the wet candle device and wind speeds higher than 3.0ms−1 weighted by the accumulated time in which these wind speeds are observed, what seems to be particularly useful when wind speed ranges around the critical value. [Copyright &y& Elsevier]

Abstract: Effectiveness of street sweeping and washing (S/W) for controlling ambient “total suspended particles (TSP)” was evaluated by TSP measurements and determining silt load from active traffic streets. A modified regenerative-air vacuum sweeper (RAVS) and a washer were used in this study. The sweeper made a pass followed by the washer. The S/W efficiencies were obtained based on the experimental data of silt loading and TSP. It was found that the direct impact of sweeping on ambient TSP emissions was short-lived lasting no more than 3–4h. When a vacuum sweeper and a washer, respectively, did a good job collecting or cleaning the visible fine particles on roads, the method of S/W tested in this work was effective at removing the sources of the road dust particles. This paper concludes that street sweeping followed by washing was found to offer a measurable reduction in TSP emission potentials. Typically, the reduction efficiency of ambient TSP is up to 30%. Finally, correlated with (based on silt loading), a useful equation is proposed to estimate the S/W efficiency, (based on TSP) with a standard error of ±20%. It seems feasible to predict the reduction efficiency of ambient TSP controlled by the regenerative-air vacuum sweeper and washer used in this work for engineering applications. Effects of traffic volume and wind velocity on the S/W efficiencies are also discussed in the paper. [Copyright &y& Elsevier]

Abstract: An air pollution index (API) reporting system is introduced to selected cities of China for public communication on air quality data. Shanghai is the first city in China providing daily average API reports and forecasts. This paper describes the development of an artificial neural network (ANN) model for the API forecasting in Shanghai. It is a multiple layer perceptron (MLP) network, with meteorological forecasting data as the main input, to output the next day average API values. However, the initial version of the MLP model did not work well. To improve the model, a series of tests were conducted with respect to the training method and structure optimization. Based on the test results, the training algorithm was modified and a new model was built. The new model is now being used in Shanghai for API forecasting. Its performance is shown reasonably well in comparison with observation. The application of the old model was only weakly correlated with observation. In 1-year application, the correlation coefficients were 0.2314, 0.1022 and 0.1710 for TSP, and , respectively. But for the new model, for over 8 months application, the correlation coefficients are raised to 0.6056, 0.6993 and 0.6300 for , , and . Further, the new algorithm does not rely on manpower intervention so that it is now being applied in several other Chinese cities with quite different meteorological conditions. The structure of the model and the application results are presented in this paper and also the problems to be further studied. [Copyright &y& Elsevier]

As potential carriers of hazardous pollutants, airborne particles may deposit onto surfaces due to gravitational settling. A modified Markov chain model to predict gravity induced particle dispersion and deposition is proposed in the paper. The gravity force is considered as a dominant weighting factor to adjust the State Transfer Matrix, which represents the probabilities of the change of particle spatial distributions between consecutive time steps within an enclosure. The model performance has been further validated by particle deposition in a ventilation chamber and a horizontal turbulent duct flow in pre-existing literatures. Both the proportion of deposited particles and the dimensionless deposition velocity are adopted to characterize the validation results. Comparisons between our simulated results and the experimental data from literatures show reasonable accuracy. Moreover, it is also found that the dimensionless deposition velocity can be remarkably influenced by particle size and stream-wise velocity in a typical horizontal flow. This study indicates that the proposed model can predict the gravity-dominated airborne particle deposition with reasonable accuracy and acceptable computing time. [ABSTRACT FROM AUTHOR]

This paper introduces a new parameter to characterize the random component in temporal variability of atmospheric pollutants and proposes a simple statistical technique for its evaluation. That parameter is the net decay time (or the time scale) of the local anomalies in concentrations of atmospheric pollutants, rather than the traditionally used chemical lifetimes of total amounts of the species. Using widely available data of hourly multi-year surface trace gas pollutant concentrations we demonstrate a simplified way to estimate the net decay time with an exponential approximation of lag-correlation functions. We assessed the decay times of fluctuations in observations of eight atmospheric pollutants (SO 2 , NO, NO 2 , NO y , O 3 , CO, NH 3 , and HNO 3 ) at two urban sites and one cleaner rural site in the Eastern US. The time scales of temporal fluctuations (net decay times) vary from about one hour to slightly more than one day. These scales are generally much shorter in urban environments than in remote regions. We also compared day- and night-time observations in warm and cold seasons. At night in the cold season, time scales of fluctuations in atmospheric pollutants are usually the longest. Such estimates should be useful to air quality prediction, public health, and satellite remote sensing research communities. [ABSTRACT FROM AUTHOR]

In the framework of the UNECE Task Force on Measurement and Modelling (TFMM) under the Convention on Long-range Transboundary Air Pollution (LRTAP), the EURODELTAIII project is evaluating how well air quality models are able to reproduce observed pollutant air concentrations and deposition fluxes in Europe. In this paper the sulphur and nitrogen deposition estimates of six state-of-the-art regional models (CAMx, CHIMERE, EMEP MSC-W, LOTOS-EUROS, MINNI and CMAQ) are evaluated and compared for four intensive EMEP measurement periods (25 Feb–26 Mar 2009; 17 Sep–15 Oct 2008; 8 Jan–4 Feb 2007 and 1–30 Jun 2006). For sulphur, this study shows the importance of including sea salt sulphate emissions for obtaining better model results; CMAQ, the only model considering these emissions in its formulation, was the only model able to reproduce the high measured values of wet deposition of sulphur at coastal sites. MINNI and LOTOS-EUROS underestimate sulphate wet deposition for all periods and have low wet deposition efficiency for sulphur. For reduced nitrogen, all the models underestimate both wet deposition and total air concentrations (ammonia plus ammonium) in the summer campaign, highlighting a potential lack of emissions (or incoming fluxes) in this period. In the rest of campaigns there is a general underestimation of wet deposition by all models (MINNI and CMAQ with the highest negative bias), with the exception of EMEP, which underestimates the least and even overestimates deposition in two campaigns. This model has higher scavenging deposition efficiency for the aerosol component, which seems to partly explain the different behaviour of the models. For oxidized nitrogen, CMAQ, CAMx and MINNI predict the lowest wet deposition and the highest total air concentrations (nitric acid plus nitrates). Comparison with observations indicates a general underestimation of wet oxidized nitrogen deposition by these models, as well as an overestimation of total air concentration for all the campaigns, except for the 2006 campaign. This points to a low efficiency in the wet deposition of oxidized nitrogen for these models, especially with regards to the scavenging of nitric acid, which is the main driver of oxidized N deposition for all the models. CHIMERE, LOTOS-EUROS and EMEP agree better with the observations for both wet deposition and air concentration of oxidized nitrogen, although CHIMERE seems to overestimate wet deposition in the summer period. This requires further investigation, as the gas-particle equilibrium seems to be biased towards the gas phase (nitric acid) for this model. In the case of MINNI, the frequent underestimation of wet deposition combined with an overestimation of atmospheric concentrations for the three pollutants indicates a low efficiency of the wet deposition processes. This can be due to several reasons, such as an underestimation of scavenging ratios, large vertical concentration gradients (resulting in small concentrations at cloud height) or a poor parameterization of clouds. Large differences between models were also found for the estimates of dry deposition. However, the lack of suitable measurements makes it impossible to assess model performance for this process. These uncertainties should be addressed in future research, since dry deposition contributes significantly to the total deposition for the three deposited species, with values in the same range as wet deposition for most of the models, and with even higher values for some of them, especially for reduced nitrogen. [ABSTRACT FROM AUTHOR]

We present measurements of atmospheric concentrations of ammonia and ammonium in the Netherlands over the period 1993–2014 and measurements of wet deposition of ammonium for 1985–2014. The various time series have been obtained at 16 monitoring stations from the Dutch National Air Quality Monitoring Network. The monitoring stations are geographically homogenously spread over the Netherlands and are equally distributed over regions with relatively low, moderate and high ammonia emission. During the period covered, changes in the monitoring have occurred. To obtain consistent time series, data are revalidated or corrected when necessary, according to current validation procedures or latest technical insights. The time series of ammonia concentrations are gap filled and time series corrected for meteorological influences are constructed. The course in the ammonia concentrations shows roughly two periods. For 1993–2004, the ammonia concentrations show a downward trend of 36%, which is statistically significant with a confidence interval (CI) of 99%. For 2005–2014, an upward trend of 19% (CI 90%) is reported. Correcting time series of ammonia concentrations for meteorological influences enhances the statistical reliability of the derived trends. This resulted in trends of −40% (CI 99%) and 24% (CI 95%) respectively. For the full period there exists no trend in ammonia concentrations due to a trend in atmospheric conditions. For 2005–2014 ammonia concentrations increased especially in springtime, while showing no change in winter months. After correcting for meteorological influences, all seasons in this period show an increase in ammonia concentrations although the increase in the spring months is still the largest. For 1993–2014 the reported ammonia emissions in the Netherlands declined in both periods with respectively 51% and 22%. The trends in emissions and ammonia concentrations correspond in the period 1993–2004 whilst over the period 2005–2014, the trends in emissions and concentrations of ammonia diverge. This divergence is for roughly a third accounted for by processes related to changes in chemical climate (see accompanying modelling paper by Wichink Kruit et al., 2016) but it is not clear what explains the remaining difference in trends. For 1993–2014, downward trends of wet deposition of ammonium and ammonium in aerosol are found to be 47% and 68%, respectively. A split into two periods is not found as is the case with the ammonia concentration. However, although statistically not significant, both wet deposition of ammonium and ammonium in aerosol show a leveling off in decline between 2005 and 2014. [ABSTRACT FROM AUTHOR]

In the last decades, in Europe a large effort was carried out to reduce sulphur and nitrogen emission in the atmosphere, in order to improve air quality and reduce the acidity of atmospheric deposition and the amount of nitrogen compounds it carries to terrestrial and aquatic ecosystems. This resulted in a sharp decrease in the deposition of sulphate and acidity, while until recently a decrease of the atmospheric load of nitrogen compounds was not evident. In this paper, we focus on the subalpine and alpine areas in North-Western Italy and Southern Switzerland (Canton Ticino), receiving high deposition of atmospheric pollutants transported from emission sources in the Po Valley, one of the most urbanised and industrialised areas of Europe. Long-term studies, covering a 30-year period (1984–2014), were carried out on the chemistry of atmospheric deposition in this area and its effects on surface water bodies through a cooperation between Swiss and Italian research institutions. A total of 14 atmospheric deposition wet-only sampling sites operate in this area, covering a wide latitudinal and altitudinal range (about 200–1900 m a.s.l.). A spatial gradient in the deposition of sulphate and nitrogen compounds was evident both in the 1990s and in recent times (2008–2012), with highest values in the south-eastern part of the area, close to the major emission sources. Deposition also varied depending on local topography. The analysis of long-term trends revealed a large proportion of significant decreasing trends in the concentration of both sulphate and nitrogen compounds. Deposition changes were less evident, due to the high interannual variability in the data, caused by the highly variable precipitation amount, ranging from 1200–1300 mm in dry years to 3000 mm in wet years. Sulphate concentrations and deposition decreased steadily since the 1980s, while ammonium and nitrate showed a widespread decrease only in the most recent period (after 2006). However, nitrogen wet deposition is still high with respect to critical loads: inorganic N deposition ranges from 60–70 meq m −2 y −1 (as the sum of ammonium and nitrate) at the alpine sites to 120–140 meq m −2 y −1 at the southern lowland sites. Deposition of ammonium has acquired an increasing importance in time, especially at the southern, more polluted sites: the relative contribution of reduced N to wet N deposition passed from about 50% in the early 1990s to 56–57% in recent years. The observed temporal changes in nitrogen deposition followed the emission decrease but with a delay. This aspect may be relevant in monitoring the effects of emission reductions as a result of the enforcements of international and national regulations. [ABSTRACT FROM AUTHOR]

Atmospheric emissions of reactive nitrogen have increased significantly on a global scale due to increases of the use of artificial fertilizer and the burning of fossil fuels. The Asian region has been identified as a high-risk area for nitrogen deposition effects on ecosystems. This paper describes a measurement-based assessment of nitrogen deposition carried out in cooperation with the Acid Deposition Monitoring Network in East Asia (EANET). The investigation aimed to understand the status and variability of dry, wet and total deposition of oxidized and reduced nitrogen over a 10-year period (2003–2012) at 8 remote sites in Japan (Rishiri, Tappi, Sado-seki, Happo, Oki, Yusuhara, Ogasawara and Hedo). Dry deposition amounts were estimated by the inferential method. All of the sites except Rishiri and Ogasawara had high mean annual total nitrogen deposition amounts of approximately 10 kg N ha −1 year −1 or more, over the 10-year period. The high contribution of oxidized nitrogen deposition in the central area is mainly caused by domestic emissions, especially for dry deposition processes. An increase in reduced nitrogen deposition originating from regional emissions was found, and is likely to result in a subsequent increase in the total nitrogen deposition in Japan. Since neither a clear increasing nor decreasing trend in total nitrogen deposition was found at any site during the 10-year period, the nitrogen deposition amounts remained high thorough the long period in Japanese remote area. The spatial distribution of nitrogen deposition was found to be significant when uncertainties were accounted for. [ABSTRACT FROM AUTHOR]

Dry deposition process is one of the important pathways for the removal of particles from atmosphere. It is the result of a combination of different environmental and physical factors as atmospheric conditions, particle properties, characteristics of the canopy. For this latter factor, urban canopy represents unevenly combinations of different types of surface elements that increases the complexity of deposition process phenomena. Therefore, particle dry deposition on urban surfaces is not easy to configure and, although empirical or semi-empirical models in literature have been developed to address this aspect, there is not standardized and commonly accepted criteria, especially for submicron particles. In this paper, comparisons of different dry deposition models and measurement data by experimental campaigns, covering for different surface roughness conditions, i.e. from four Italian cities and urban environments of other countries, are performed. Giardina et al. (2017b) model, by using a Brownian diffusion resistance as proposed in this paper, seems to capture the main dry deposition processes for the examined contexts. • A pathway to remove pollutants in atmosphere is the dry deposition process. • Modelling of dry deposition phenomena over urban canopies is performed. • Comparisons were performed between deposition velocity models and experiments covering for different surface roughness conditions. • The proposed Brownian diffusion resistance captures the main dry deposition processes for the examined urban canopies. [ABSTRACT FROM AUTHOR]

A large emission of air pollutants from the Asian continent has caused transboundary air pollution, especially in northeastern Asia. This paper evaluates sulfate deposition at a leeward area of Asian continent, i.e., the Nagaoka observation station located along the Sea of Japan. We have monitored atmospheric sulfate deposition and its sulfur isotopic ratio for 28 years at the station. The sulfur isotopic ratios of non-sea-salt sulfate (δ 34 Snss) ranged from 0.0 to +6.2‰. The isotopic ratios of local emission and Chinese coal sulfur showed negative and positive values, respectively. Several statistically significant trends were detected on the deposition of non-sea-salt sulfate (nss-SO 4 2− ) during the study period. The decrease of nss-SO 4 2− deposition since the middle of 1980s was considered to have been caused by local anthropogenic SO 2 emission that showed relatively low δ 34 Snss values during the period. The increase of nss-SO 4 2− deposition from the end of 1990s to the second half of 2000s was interpreted to have been caused by the change in SO 2 emission in China because the δ 34 Snss values increased during the period with the winter values getting closer to the averaged value of Chinese coal sulfur. The decreasing trend of nss-SO 4 2− deposition from the middle of 2000s was likely affected by reduction of Chinese SO 2 emission judging from the decrease in δ 34 Snss values in the period. Mass balance calculations suggested that sulfur released by coal combustion in China during 1990s contributed by about 40% of annual total sulfur deposition in Nagaoka, and its contribution increased up to 60% in the middle of 2000s. The contribution turned to decrease after that peak, which was in harmony with the temporal change of emission from China. [ABSTRACT FROM AUTHOR]

Understanding the characteristics of the size distribution of ambient black carbon (BC) in distinct environments is critical because the influence of BC aerosols on climate, visibility, and human health depends strongly on the distribution of BC aerosols over the particle size spectrum. In this study, a novel method for determining the mass size distribution of BC in atmospheric aerosols was developed. This size-segregation method relies on measuring BC in parallel using two aethalometers, one of which is used to measure the total BC (BC T ) mass concentration as a reference level and the other is used to measure the BC (BC i ) mass concentration for BC sizes below specific particle sizes that are selected using a size cut-off inlet. In this study, this method was applied to measure BC in atmospheric samples at an urban traffic site. The aethalometers were operated continually from December 15, 2012 to January 31, 2013, and from February 15, 2013 to March 31, 2013. The measurement results presented in this paper are for the diurnal variation patterns, average concentrations, mass fractions, and size distributions of BC aerosols. The results indicate that BC T mass concentration is approximately 2.8 μg m−3 in the Taipei urban area. The levels of BC at this sampling site were affected markedly by traffic emission levels and local wind speed. At the sampling site, the average BC2.5/BC T , BC1.0/BC T , BC0.5/BC T , BC0.25/BC T , and BC0.1/BC T were 0.96 ± 0.04, 0.92 ± 0.07, 0.89 ± 0.04, 0.73 ± 0.10, and 0.18 ± 0.08, respectively. The results indicate that approximately 90% of the BC aerosols were smaller than 0.5 μm, that most of the BC aerosols (55%) were in the size range of 0.1–0.25 μm, and that approximately 18% of the BC aerosols were ultrafine. Moreover, the daily average mass size distribution of BC exhibited a single accumulation mode at 0.16 μm at this sampling site. The mode of the BC mass size distribution at rush hour (9 AM) was only 0.14 μm, which is smaller than the daily average. Moreover, the mode of the BC mass size distribution at an early morning hour (3 AM) was 0.18 μm, and a minor coarse mode was also observed during this period. The results further revealed that the geometric diameter (D pg) of the BC aerosols varied between 0.14 and 0.22 μm and the geometric standard deviation (σ g ) of these BC aerosols ranged between 1.4 and 2.3 during the sampling period. Because BC exhibits extremely low chemical reactivity; the size distribution of BC in the atmosphere does not change substantially except through coagulation. [ABSTRACT FROM AUTHOR]

Abstract: The North Atlantic Oscillation (NAO) has been identified as one of the atmospheric patterns which mostly influence the temporal evolution of precipitation and temperature in the Mediterranean area. Recently, the Western Mediterranean Oscillation (WeMO) has also been proposed to describe the precipitation variability in the eastern Iberian Peninsula. This paper examines whether the chemical signature and/or the chemical deposition amounts recorded over NE Iberian Peninsula are influenced by these climatic variability patterns. Results show a more relevant role of the WeMO compared to NAO in the deposition of either marine (Cl−, Na+, Mg2+) or anthropogenic pollutants (H+, NH4 +, NO3 − and SO4 2−). A cluster classification of provenances indicated that in winter (December to March) fast Atlantic air flows correspond to positive WeMO indices, while negative WeMOi are associated to Northeastern and Southwestern circulations. The negative phase of WeMO causes the entry of air masses from the Mediterranean into the Iberian Peninsula, that are enriched with marine ions and ions of anthropogenic origin (NH4 +, NO3 − and SO4 2−). For these later, this suggests the advection over the Mediterranean of polluted air masses from southern Europe and the scavenging and deposition of this pollution by precipitation during the WeMO negative phases. This will carry transboundary pollutants to the NE Iberian Peninsula. However, local pollutants may also contribute, as precipitation events from the Mediterranean and the Atlantic (associated to both WeMO phases) may incorporate emissions that accumulate locally during the winter anticyclonic episodes typical of the region. [Copyright &y& Elsevier]

During the spring of 2010, comprehensive in situ measurements were made for the first time on a small atoll (Dongsha Island) in the northern South China Sea (SCS), a key region of the 7-SEAS (the Seven South East Asian Studies) program. This paper focuses on characterizing the source origins, transport processes, and vertical distributions of the Asian continental outflows over the region, using measurements including mass concentration, optical properties, hygroscopicity, and vertical distribution of the aerosol particles, as well as the trace gas composition. Cluster analysis of backward trajectories classified 52% of the air masses arriving at ground level of Dongsha Island as having a continental origin, mainly from northern China to the northern SCS, passing the coastal area and being confined in the marine boundary layer (0–0.5 km). Compared to aerosols of oceanic origin, the fine mode continental aerosols have a higher concentration, extinction coefficient, and single-scattering albedo at 550 nm (i.e., 19 vs. 14 μg m−3 in PM2.5; 77 vs. 59 Mm−1 in βe; and 0.94 vs. 0.90 in ω , respectively). These aerosols have a higher hygroscopicity (f at 85% RH = 2.1) than those in the upwind inland regions, suggesting that the aerosols transported to the northern SCS were modified by the marine environment. In addition to the near-surface aerosol transport, a significant upper-layer (3–4 km) transport of biomass-burning aerosols was observed. Our results suggest that emissions from both China and Southeast Asia could have a significant impact on the aerosol loading and other aerosol properties over the SCS. Furthermore, the complex vertical distribution of aerosols-coinciding-with-clouds has implications for remote-sensing observations and aerosol–cloud–radiation interactions. [ABSTRACT FROM AUTHOR]

Beryllium-7 is a potentially powerful tracer of soil erosion, but information on 7Be atmospheric deposition and associated soil inventories on the Loess Plateau of China is not readily available. In the study reported in this paper, we measured the 7Be inventories in undisturbed soil at different sampling times on the northern Loess Plateau of China for three years, between 2010 and 2012, and estimated the 7Be deposition fluxes and the daily 7Be inventories in undisturbed soil. The annual 7Be deposition fluxes during this period varied between 1303 ± 119 and 2222 ± 147 Bq m−2, with a mean of 1759 ± 416 Bq m−2. There is a marked seasonality for the 7Be deposition fluxes with the maximum in summer, approximately 50% to the annual deposition flux, and the minimum in winter, approximately 5% to the annual deposition flux. Precipitation amounts can explain more than 70% of the variation in 7Be deposition flux. 7Be deposition in the form of dustfall, dew and frost make a significant contribution to the 7Be deposition flux in the study region. The daily 7Be inventories in undisturbed soil varied markedly through time and ranged between 89.2 and 941.8 Bq m−2 with a mean of 392 ± 210 Bq m−2. They demonstrated a unimodal distribution over the year, with the highest values in August or September and the lowest in late winter or early spring. [ABSTRACT FROM AUTHOR]

Abstract: With the new air quality standards forthcoming in China, the Pearl River Delta region is facing new challenges to achieve its air quality goal. The success of the emission reduction measures introduced by local authorities in the run-up to the Guangzhou Asian Games demonstrated that the Pearl River Delta air quality can be improved by introducing integrated emission reduction measures. This paper combines observation data, emission reduction measures, and air quality simulations that were applied during the Asian Games (12–27 November 2010) to analyze the relationship between emissions and concentrations of pollutants in Guangzhou. The Asian Games abatement strategy totally reduced emissions of 41.1% SO2, 41.9% NO x , 26.5% PM10, 25.8% PM2.5 and 39.7% VOC. The concentrations of SO2, NO2, PM10 and PM2.5 were reduced by 66.8%, 51.3%, 21.5% and 17.1%, respectively. In Guangzhou, the main challenge to be overcome with the new air quality daily requirements is mostly for NO2, PM2.5, and hourly ozone maxima. If pollutants maintain the same concentrations before and after the Asian Games, there will be 47.4% and 31.6% non-attainment days for NO2 and PM2.5 respectively as a period average. Although PM10 concentration can meet the daily limits (150 μg m−3), it is quite difficult to meet the annual limit value (70 μg m−3). One important implication is that the long-term, step-by-step integrated measures of the past six years work better than the strict, intensive, short-term measures on SO2, NO2 and VOC control. Dust control by limiting construction sites and watering the roads can further reduce 12.8% of the PM10 concentration. However, to reduce ambient PM2.5, the abatement strategy should be more complex and extensive. On the contrary, ozone pollution was not improved during the Asian Games, indicating that alleviation strategies should be improved by scientific studies to determine the appropriate control ratio of NO2 and VOC in the Pearl River Delta region. [Copyright &y& Elsevier]

Abstract: Atmospheric deposition is one of the most important pathways of urban stormwater pollution. Atmospheric deposition, which can be in the form of either wet or dry deposition have distinct characteristics in terms of associated particulate sizes, pollutant types and influential parameters. This paper discusses the outcomes of a comprehensive research study undertaken to identify important traffic characteristics and climate factors such as antecedent dry period and rainfall characteristics which influences the characteristics of wet and dry deposition of solids and heavy metals. The outcomes confirmed that Zinc (Zn) is correlated with traffic volume whereas Lead (Pb), Cadmium (Cd), Nickel (Ni), and Copper (Cu) are correlated with traffic congestion. Consequently, reducing traffic congestion will be more effective than reducing traffic volume for improving air quality particularly in relation to Pb, Cd, Ni, and Cu. Zn was found to have the highest atmospheric deposition rate compared to other heavy metals. Zn in dry deposition is associated with relatively larger particle size fractions (>10 μm), whereas Pb, Cd, Ni and Cu are associated with relatively smaller particle size fractions (<10 μm). The analysis further revealed that bulk (wet plus dry) deposition which is correlated with rainfall depth and contains a relatively higher percentage of smaller particles compared to dry deposition which is correlated with the antecedent dry period. As particles subjected to wet deposition are smaller, they disperse over a larger area from the source of origin compared to particles subjected to dry deposition as buoyancy forces become dominant for smaller particles compared to the influence of gravity. Furthermore, exhaust emission particles were found to be primarily associated with bulk deposition compared to dry deposition particles which mainly originate from vehicle component wear. [Copyright &y& Elsevier]

Abstract: Tracking of an atmospheric release of pollution is usually based on measurements provided by stationary networks, occasionally complemented with deployment of mobile sensors. In this paper, we extend the existing concept to the case where the sensors are carried onboard of unmanned aerial vehicles (UAVs). The decision theoretic framework is used to design an unsupervised algorithm that navigates the UAVs to minimize the selected loss function. A particle filter with a problem-tailored proposal function was used as the underlying data assimilation procedure. A range of simulated twin experiments was performed on the problem of tracking an accidental release of radiation from a nuclear power plant in realistic settings. The main uncertainty was in the released activity and in parametric bias of the numerical weather forecast. It was shown that the UAVs can complement the existing stationary network to improve the accuracy of data assimilation. Moreover, two autonomously navigated UAVs alone were shown to provide assimilation results comparable to those obtained using the stationary network with more than thirty sensors. [Copyright &y& Elsevier]

Abstract: Real time measurements of Black Carbon (BC) in PM2.5 aerosols were performed during AMMA and POLCA programs, between 2005 and 2010 in Cotonou (Benin), Dakar (Senegal), Bamako (Mali), and Yaounde (Cameroon). Indeed, BC was chosen as a metric because of its interest as an urban pollutant. The instrumented sites are representative of the traffic source. At Dakar, BC concentrations are high from November to April (13,000±3500ngm−3) and lower from May to September (8000±3200ngm−3). In dry season (November–April), high BC concentrations occurred as a result of northeasterly long-range transport of polluted air masses over West Africa, in addition to local emissions. However, during wet season (May–September) reduced traffic levels, school vacations and wet deposition processes contribute to lower BC concentration levels. Measured diurnal BC peak concentrations, at all sites, mainly occur during morning and evening rush-hour periods, indicating the paramount role of traffic. Highest values are observed between 5–9 a.m. and from 5 p.m. to 9 p.m. depending on the site, while lowest are occurred at night time and middle afternoon when activities of the population are reduced. BC source apportionment from absorption measurements also confirmed the relative importance of traffic (88%) versus biomass burning (12%). Also, BC measurements were functions of days of the week, with highest values occurring on Fridays and lowest ones on Sundays. Spatial variations associated to BC levels are very different from one site to another, revealing different types of sources with strong variations at the regional scale. It appears that mean BC concentrations in Dakar are lower by a factor of two, compared to those observed in Bamako, but remain higher than in some other West African sites (e.g. Cotonou, Yaounde). Overall, BC concentrations in our different sites are comparable to reported European and Asian megacity levels. Finally, using measured BC/PM2.5 ratios, we have estimated PM2.5 mass concentrations in Dakar from June 2008 to June 2009 to be 44.4±14.3μgm−3, well above the threshold of 10μgm−3. This paper clearly highlights high pollution levels in West African large cities, with potential important impacts on the health of the regional population. [Copyright &y& Elsevier]

Abstract: Soiling results from the deposition of pollutants on materials. On glass, it leads to an alteration of its intrinsic optical properties. The nature and intensity of this phenomenon mirrors the pollution of an environment. This paper proposes a new statistical model in order to predict the evolution of haze (H) (i.e. diffuse/direct transmitted light ratio) as a function of time and major pollutant concentrations in the atmosphere (SO2, NO2, and PM10 (Particulate Matter<10μm)). The model was parameterized by using a large set of data collected in European cities (especially, Paris and its suburbs, Athens, Krakow, Prague, and Rome) during field exposure campaigns (French, European, and international programs). This statistical model, called NEUROPT-Glass, comes from an artificial neural network with two hidden layers and uses a non-linear parametric regression named Multilayer Perceptron (MLP). The results display a high determination coefficient (R 2 =0.88) between the measured and the predicted hazes and minimizes the dispersion of data compared to existing multilinear dose–response functions. Therefore, this model can be used with a great confidence in order to predict the soiling of glass as a function of time in world cities with different levels of pollution or to assess the effect of pollution reduction policies on glass soiling problems in urban environments. [Copyright &y& Elsevier]

Abstract: This paper focuses on 7Be concentration in the atmospheric surface aerosols of the Spanish city of Granada, in the southern Iberian Peninsula. We analyze the effects of meteorological conditions in the geographical zone over the period 2005–2009. A prediction model is suggested to describe the behaviour of atmospheric aerosols containing 7Be. The model was applied from January to May 2010 and shows that temperature, relative humidity and precipitation are the meteorological factors responsible for the behaviour of atmospheric aerosols. The statistical significance of the results was 99%. This study helps understanding of the atmosphere of Granada as well as the climate variables responsible for transportation and deposition of atmospheric aerosols. Moreover, in case of a massive release of radionuclides into the atmosphere, the results of this study will help predict behaviour in this city and other continental areas with a similar climate. [Copyright &y& Elsevier]

Abstract: Although they may have no direct health impacts, visible water vapour plumes can be of concern to the local population in the vicinity of major industrial plant developments. In this paper, prediction of the occurrence of visible plumes at proposed industrial sites is assessed using the case study of a planned major cement plant in New Zealand. The aim of the investigation was to use a simple but robust approach to estimate the frequency of occurrence of visible water vapour plumes emitted by a proposed plant, as well as their likely dimensions. Input data consisted of information relating to the raw materials used in the production process, as well as stack design parameters. The atmospheric mesoscale model TAPM (The Air Pollution Model) was run for the whole of 2007 to predict ambient conditions in the vicinity of the site. A simple model was then applied to predict visible water vapour plume development under a range of emission rates for the whole year, as well as by season. Predictions were provided for the whole year, allowing for the fact that visible plumes would not be a problem at night and during rain. Model results showed that with three different emission rates (design, intermediate and worst-case) the occurrence of visible plumes at the proposed stack site is likely to be infrequent (less than 0.1% of hours per annum at 20 m from the stack under design conditions). When they do occur, the plumes are expected to be relatively small (a few tens of metres in length/diameter). Visible plume occurrence in winter is predicted to increase to almost 0.2% of the time under the design emission rate of 8.6 kg s−1. The main effect is expected to be on visible plume development within 50 m of the stack, while further away from the stack any visible plume development is expected to be negligible. The sensitivity of visible plume development to varying stack water discharge rates is investigated, along with the specific meteorological conditions under which visible plumes are predicted to develop. [Copyright &y& Elsevier]

Abstract: Damage caused to objects of cultural heritage is one of the most serious detrimental effects of air pollutants. Within the 6th Framework Programme of the EU, the CULT-STRAT project is an inter-agency, multi-disciplinary project that has integrated research and monitoring information to provide answers to policy and management questions, which relate the effects of air pollutants on heritage and the management options available to mitigate them. The overall aim of the project has been to assess and predict the effects of different pollutants on materials and objects of cultural heritage in a multipollutant scenario and to identify indicators and thresholds levels of pollutants. These have been used for development of management strategies for sustainable maintenance and preventive conservation of European Cultural Heritage and air quality policy from continental to local scale. The present paper reports one of the studies carried out in the CULT-STRAT project at city level and focused on the town of Madrid (Spain). Different maps are shown for the present and possible future scenarios (2010 and 2020): inventory of stock of cultural heritage for each selected material, concentration of selected pollutants (SO2, NO2, O3 and PM10), corrosion (cast bronze) and recession (Portland limestone), exceedance of tolerable degradation thresholds for each material and corrosion-cultural heritage overlapped maps. [Copyright &y& Elsevier]

Abstract: The radiometric composition of bulk deposition samples, collected monthly in a 5 year period (1 January 2005 until 31 December 2009) at a site located 30m a.s.l in Málaga (4°28′ 8″W; 36° 43′40″N), are analysed in this paper. Measurement of gross alpha, gross beta, artificial and natural radionuclide activity concentrations were carried out in 60 bulk deposition samples. We analysed the time series of gross alpha, gross beta 7Be, 210Pb and 40K. The specific activities of gross alpha and gross beta measured in bulk deposition material are in the range from 0.012–0.32 and 0.045–1.81Bql−1 and theirs mean values are: 0.11 and 0.59Bql−1 respectively. The activity values of 7Be and 210Pb are in the range from 0.65–8.3 and 0.05–1.32Bql−1 with mean values of 2.5 and 0.41Bql−1 respectively. The highest specific activities of 40K in bulk deposition material were recorded in connection with high altitude Saharan dust intrusion. The time variations of the different radionuclide concentrations have been discussed in relation with various meteorological factors and the mean values have been compared to those published in recent literature for other sites located at different latitudes. To study the deposition, monthly deposition data from a funnel collector were compared from 2005 to 2009.The monthly range in deposition fluxes for gross alpha varied widely (0.40–11Bqm−2 month−1) and the average annual deposition is 21Bqm−2 y−1. The monthly fluxes for gross beta varied (1.3–33.8Bqm−2 month−1) and the average annual deposition is approximately 120Bqm−2 y−1. The total annual deposition fluxes of 210Pb varied between 64.9 and 160.8Bqm−2 y−1 with a mean of 120Bqm−2 y−1. The annual 7Be depositional flux varied between 432 and 1204Bqm−2 y−1 with a mean of 676Bqm−2 y−1. Observed seasonal variations of deposition data are explained in terms of different environmental features. The atmospheric deposition fluxes of 7Be and 210Pb were moderately well correlated with rainfall (r 2 of 0.72 and 0.76 respectively) and well correlated one with the other (r 2 of 0.79). [Copyright &y& Elsevier]

Abstract: This paper compares spatial and seasonal variations and temporal trends in modeled and measured concentrations of sulfur and nitrogen compounds in wet and dry deposition over an 18-year period (1988–2005) over a portion of the northeastern United States. Substantial emissions reduction programs occurred over this time period, including Title IV of the Clean Air Act Amendments of 1990 which primarily resulted in large decreases in sulfur dioxide (SO2) emissions by 1995, and nitrogen oxide (NOx) trading programs which resulted in large decreases in warm season NOx emissions by 2004. Additionally, NOx emissions from mobile sources declined more gradually over this period. The results presented here illustrate the use of both operational and dynamic model evaluation and suggest that the modeling system largely captures the seasonal and long-term changes in sulfur compounds. The modeling system generally captures the long-term trends in nitrogen compounds, but does not reproduce the average seasonal variation or spatial patterns in nitrate. [ABSTRACT FROM AUTHOR]

Abstract: Monthly nitrogen isotopes of ammonium and nitrate in wet deposition in the city of Guangzhou, and the causes of their variability, are reported in this paper. Nitrate δ15N showed nearly constant values around zero in the dry season (October to April), but oscillating values from negative to positive in the rainy season (May to September). By contrast, ammonium δ15N displayed lower values during the rainy season than in the dry season. The rural area north of the city was considered as the prominent source of ammonium and nitrate in spring and early summer (May and June), as suggested by their concurrent negative isotopic trends and higher NH4 +/NO3 − ratios. From July to September, different dominating sources from the city, i.e., fossil fuel combustion for nitrate, and sewage and waste emission for ammonium, caused disparate δ15N trends of the two species, showing positive nitrate δ15N, but still negative ammonium δ15N. During the cool dry season, the high values of ammonium δ15N and concurrently low NH4 +/NO3 − ratios suggested the decrease in NH3 volatilization and relatively important thermogenic origin of ammonium, but the intermediate nitrate δ15N values around zero may be a result of a balanced emission of NOx from the city and the rural areas. The isotopic effects of chemical conversion of NOx to nitrate and washout of nitrate were ruled out as significant causes of nitrate δ15N variability, but ammonium washout, during which 15N is assumed to be preferentially removed, may partly contribute to the ammonium δ15N variability. [Copyright &y& Elsevier]

Abstract: The contribution of vehicular traffic to air pollutant concentrations is often difficult to establish. This paper utilizes both time-series and simulation models to estimate vehicle contributions to pollutant levels near roadways. The time-series model used generalized additive models (GAMs) and fitted pollutant observations to traffic counts and meteorological variables. A one year period (2004) was analyzed on a seasonal basis using hourly measurements of carbon monoxide (CO) and particulate matter less than 2.5 μm in diameter (PM2.5) monitored near a major highway in Detroit, Michigan, along with hourly traffic counts and local meteorological data. Traffic counts showed statistically significant and approximately linear relationships with CO concentrations in fall, and piecewise linear relationships in spring, summer and winter. The same period was simulated using emission and dispersion models (Motor Vehicle Emissions Factor Model/MOBILE6.2; California Line Source Dispersion Model/CALINE4). CO emissions derived from the GAM were similar, on average, to those estimated by MOBILE6.2. The same analyses for PM2.5 showed that GAM emission estimates were much higher (by 4–5 times) than the dispersion model results, and that the traffic-PM2.5 relationship varied seasonally. This analysis suggests that the simulation model performed reasonably well for CO, but it significantly underestimated PM2.5 concentrations, a likely result of underestimating PM2.5 emission factors. Comparisons between statistical and simulation models can help identify model deficiencies and improve estimates of vehicle emissions and near-road air quality. [Copyright &y& Elsevier]

Abstract: This paper reports mercury (Hg) concentrations and fluxes in precipitation that was collected from 2006 to 2008 at three sites in Canada: sub-Arctic boreal forest, sub-Arctic coast, and southern Alberta, using cold-adapted precipitation collectors which operated reliably at temperatures below −30 °C during the study. The southern Alberta site (Crossfield) may be influenced by Calgary urban air, whereas the sub-Arctic coastal (Churchill, Manitoba) and boreal forest (Fort Vermilion, Alberta) sites are in more remote northern areas. Annual mean Hg concentrations in precipitation (5.0–9.2 ng L−1) at the study sites were in the lower half of the range reported for southern Canada and the USA by the Mercury Deposition Network (MDN). But owing to typically low precipitation rates, gross wet Hg fluxes (0.54–2.0 μg m−2 yr−1) were among the lowest reported by MDN, with Crossfield having about twice the flux in 2007 of the other two sites. Flux was significantly correlated with precipitation, and thus was highest in summer (June–August) and lowest during winter, a pattern typical of other temperate continental locations. There was no evidence of higher wet Hg fluxes or concentrations in springtime at Churchill where atmospheric mercury depletion events (AMDEs) occur. Measured gross deposition fluxes at the study locations were ∼2–8 times lower than estimated by GEOS-Chem and GRAHM atmospheric models. The largest discrepancy occurred for Churchill, which raises the question of how well Hg deposition from AMDEs is described by current models. Better agreement between measurements and models was obtained from MDN stations in Alberta and Alaska, where wet Hg fluxes were 2–10 times higher than the study sites either because of power plant emissions (Alberta), or because of high precipitation rates (Alaska). [Copyright &y& Elsevier]

The present experimental study aims to measure the deposition of fine particles on building internal surface coverings. A 125-liter experimental chamber has been built in order to evaluate the loss-rate coefficients of 0.35, 0.53, 0.7, 1 and 2μm particles on eight coverings commonly found in buildings (two sheet vinyl, two wallpapers, two woods, one custom- made plaster and one custom- made concrete) under three airflow intensity levels. Results show that, if particle deposition clearly increases with near-wall airflow velocity, the role of the surface three-dimensional roughness is less evident because of the complex topography of real coverings. [Copyright &y& Elsevier]

In complied data of atmospheric deposition of 210Pb and 7Be in the world, the data from China is of lack. In the present paper, atmospheric depositional fluxes of 7Be and 210Pb were simultaneously measured in semimonthly interval for 1 year (from November 2005 to October 2006) at Shanghai (31°13′39″N, 121°23′56″E), China, 50km from the coastal of East China Sea. The annual average flux of 210Pb and 7Be in 2006 is 4.79×102 and 2.07×103 Bqm−2 year−1, respectively. Compared with the published data, the highest flux of 210Pb in 2006 at Shanghai was clearly observed during studying periods. The possible reason for such high flux of 210Pb is discussed. Furthermore, deposition fluxes of both 210Pb and 7Be show varieties in seasons: highest flux of 210Pb in winter (November–August) and that of 7Be in spring (March–May). Moreover, the correlation between activity fluxes and precipitation are weak both for 7Be and 210Pb in whole of 2006; however, the high correlation are observed in autumn and spring for 7Be and that only in autumn for 210Pb. [Copyright &y& Elsevier]

Examination of model sensitivity to horizontal grid resolutions can help identify optimal compromise in accuracy and computational efficiency for regulatory and research-grade applications of 3-D atmospheric models. In this Part III paper, the performance and sensitivity of simulated precipitation and wet deposition amounts by the MM5/CMAQ model to three horizontal grid resolutions (4-, 12-, and 36-km) are evaluated over North Carolina (NC). In contrast with simulated O3, PM2.5, and some PM2.5 species such as NH4 +, simulated precipitation and wet deposition amounts are quite sensitive to grid resolutions. Compared with results at coarser resolutions, simulated precipitation amounts are lower in both August and December at 4-km, with the largest sensitivities to grid resolutions occurring in mountain and coastal regions of NC. For wet deposition predictions, the model performs the best for NO3 − at 4-km and for NH4 + and SO4 2− at 12-km in August, but the best for NH4 + and NO3 − at 36-km and for SO4 2− at 4-km in December. Such sensitivities and lack of clear trends in model performance at various resolutions can be attributed to seasonalities in meteorology and differences in characteristics of land use, emissions and concentrations of PM precursors, as well as nonlinear responses of chemistry and meteorology to grid resolutions. The overall performance trends demonstrate a high sensitivity in precipitation and wet deposition predictions over complex terrain and the fact that higher grid resolution does not always lead to improved model performance. [Copyright &y& Elsevier]

This paper presents a new approach for the modelling of aerosol dry deposition on vegetation. It follows a companion article, in which a review of the current knowledge highlights the need for a better description of the aerosol behaviour within the canopy [Petroff, A., Mailliat, A., Amielh, M., Anselmet, F., 2008. Aerosol dry deposition on vegetative canopies. Part I: Review of present knowledge. Atmospheric Environment, in press, doi:10.1016/j.atmosenv.2007.09.043]. Concepts from multi-phase flow studies are used for describing the canopy medium and deriving a time and space-averaged aerosol balance equation and the associated deposition terms. The closure of the deposition terms follows an up-scaling procedure based on the statistical distribution of the collecting elements. This aerosol transport model is then applied in a stationary and mono-dimensional configuration and takes into account the properties of the vegetation, the aerosol and the turbulent flow. Deposition mechanisms are Brownian diffusion, interception, inertial and turbulent impactions, and gravitational settling. For each of them, a parameterisation of the particle collection is derived and the quality of their predictions is assessed by comparison with wind-tunnel deposition measurements on coniferous twigs [Belot, Y., Gauthier, D., 1975. Transport of micronic particles from atmosphere to foliar surfaces. In: De Vries, D.A., Afgan, N.H. (Eds.), Heat and Mass Transfer in the Biosphere. Scripta Book, Washington, DC, pp. 583–591; Belot, Y., 1977. Etude de la captation des polluants atmosphériques par les végétaux. CEA, R-4786, Fontenay-aux-Roses; Belot, Y., Camus, H., Gauthier, D., Caput, C., 1994. Uptake of small particles by canopies. The Science of the Total Environment 157, 1–6]. Under a real canopy configuration, the predictions of the aerosol transport model compare reasonably well with detailed on-site deposition measurements of Aitken mode particles [Buzorius, G., Rannik, Ü., Mäkelä, J.M., Vesala, T., Kulmala, M., 2000. Vertical aerosol fluxes measured by eddy covariance methods and deposition of nucleation mode particles above a Scots pine forest in southern Finland. Journal of Geophysical Research 105, 19905–19916] and fog droplets [Beswick, K.M., Hargreaves, K.L., Gallagher, M.W., Choularton, T.W., Fowler, D., 1991. Size-resolved measurements of cloud droplet deposition velocity to a canopy using an eddy correlation technique. Quarterly Journal of the Royal Meteorological Society 117, 623–645] on coniferous forest, as well as with a broader data collection both on coniferous forest and grass. Finally, a sensitivity analysis emphasises the main parameters of deposition, which are specific of particle size. [Copyright &y& Elsevier]

This paper reviews the present knowledge of aerosol dry deposition, with respect to modelling and experimental aspects. In the first part, special attention is given to the existing mechanistic models, either with an analytical or a differential structure. Their predictions are compared against available measurements for grass and forest environments, obtained under controlled aerosol size and aerodynamic conditions. The observed differences are largely related to the parameterisation of the aerosol collection within the canopy. In the second part, existing experimental results are reviewed and a synthesis is provided through different inter-comparisons concerning: (1) the influence of atmospheric stability on fine particle deposition, (2) the evolution of coarse aerosol deposition with aerodynamic conditions and (3) the aerosol size dependence of deposition on grass and forest canopies. A wider compilation of measurements obtained on different canopies is finally proposed. [Copyright &y& Elsevier]

This paper focuses on the comparison of chemical deposition of eight regional chemical models used in Model Inter-Comparison Study for Asia (MICS-Asia) II. Monthly-mean depositions of chemical species simulated by these models, including dry deposition of SO2, HNO3, NH3, sulfate, nitrate and ammonium and wet deposition of SO4 2−, NO3 − and NH4 +, have been provided for four periods (March, July, December 2001 and March 2002) in this work. Observations at 37 sites of the Acid Deposition Monitoring Network in East Asia (EANET) are compared with SO4 2−, NO3 − and NH4 + wet deposition model results. Significant correlations appeared between the observation and computed ensemble mean of participant models. Also, differences among modeled sulfur and nitrogen dry depositions have been studied at the EANET sites. Based on the analysis of acid deposition for various species from different models, total depositions of sulfur (SO2 and sulfate) and nitrogen (nitrate and ammonium) have been evaluated as the ensemble mean of the eight models. In general, all models capture the observed spatial distribution of sulfur and nitrogen deposition, although the absolute values may differ from measurements. High deposition often occurs in eastern China, Japan, the Republic of Korea, Thailand, Vietnam, Philippines and other parts of Southeast Asia. The magnitude of model bias is quite large for many of the models. In examining the reasons for model–measurement disagreement, we find that differences in chemical processes, deposition parameterization, and modeled precipitation are the main reasons for large model disparities. [Copyright &y& Elsevier]

Abstract: Fireworks are one of the most unusual sources of pollution in atmosphere; although transient, these pollution episodes are responsible for high concentrations of particles (especially metals and organic compounds) and gases. In this paper, results of a study on chemical–physical properties of airborne particles (elements, ions, organic and elemental carbon and particles size distributions) collected during a fireworks episode in Milan (Italy) are reported. Elements typically emitted during pyrotechnic displays increased in 1h as follows: Sr (120 times), Mg (22 times), Ba (12 times), K (11 times), and Cu (6 times). In our case study, Sr was recognised as the best fireworks tracer because its concentration was very high during the event and lower than, or comparable with, minimum detection limits during other time intervals, suggesting that it was mainly due to pyrotechnic displays. In addition, particles number concentrations increased significantly during the episode (up to 6.7 times in 1h for the 0.5

This paper presents the results from a study conducted in two urban areas in Korea to compare the size distributions of atmospheric aerosols, focusing on carbonaceous and certain major inorganic compounds, after long-range transport between selected days in winter and summer. Size segregated aerosols were sampled for 3 consecutive days each in February and July, 2004, and were analyzed to obtain the 24-h averaged concentrations of total mass, elemental carbon, organic carbon, nitrate, and sulfate. Backward trajectories from the receptor site on the sampling days were calculated to estimate the elapsed time for the air parcel to travel between Wonju and the Seoul metropolitan area. The averaged elapsed time on the sampling days was 3–12h in the winter and 10–19h in the summer. The enrichment of fine particles as expressed in particulate matter (PM)2/(PM10–PM2) was higher in the summer as compared to that in the winter. Size-fractionized concentration ratios of the organic to the elemental carbon at Wonju were two times as high as those at Seoul except for the particles with size <0.5μm. This increasing trend was in proportional to the length of the elapsed time during the summer. Ultrafine particles in the summer were further enriched in carbon compounds, particularly in organic carbons and those in winter more enriched in the sulfates and nitrates. The mass fractions of organic carbon, elemental carbon, sulfate and nitrate became more significant with the decrease in the particle size. [Copyright &y& Elsevier]

Urumchi suffered serious air quality problem in recent years. Although the main air pollutants and wet deposition monitoring have been undertaken by Urumchi Environmental Monitoring Center for many years, researches on chemical composition and variations of wet deposition were not there till now. In this paper, wet deposition monitoring data in Urumchi from 2000 and 2005 were selected to perform this evaluation based on data quality and data integrity. The volume-weighted mean (VWM) concentrations of parameters of wet deposition, namely pH, conductivity, SO4 2−, NO3 −, F−, Cl−, NH4 +,Ca2+, Mg2+, Na+ and K+ concentrations, were 6.86 and 91.04μscm−1, 14.3, 1.63, 0.37, 3.78, 1.22, 4.79, 0.59, 1.05, 0.74mgL−1, respectively. Acid precipitation appeared only in wintertime in few cases, and its extreme value was 4.96; the maximum emerged during sand storm event in the non-winter season with the value of 9.35. Wet deposition and air pollution characteristics varied with seasons. In order to make a certainty of possible sources of ions in different seasons, principal component analysis was applied, and conclusions were drawn that in wintertime, the predominant contributor to the wet deposition was coal combustion for residential heating; however, in the non-winter season, the situation was more complicated, dust and soil from outside the urban, dust re-suspension, local industries process, motor vehicle emissions all played their roles. [Copyright &y& Elsevier]

Studies on the effect of NO x on zinc corrosion are scarce and their results are variable and at times seemingly contradictory. This paper reports laboratory tests involving the dry deposition on zinc surfaces of 800μgm−3 NO2, alone and in combination with 800μgm−3 SO2, at temperatures of 35 and 25°C and relative humidities of 90% and 70%. From the gravimetric results obtained and from the characterisation of the corrosion products by optical microscopy, scanning electron microscopy (SEM/EDX), grazing incidence X-ray diffraction (GIXD) and X-ray photoelectron spectroscopy (XPS), it has been verified that the corrosive action of NO2 alone is negligible compared with SO2. However, an accelerating effect has been observed when NO2 acts in conjunction with SO2 at 25°C and 90% RH. At 35°C and 90% RH, the accelerating effect is smaller, and at low relative humidities (70%), the synergistic effect is only slight, which suggests it may be favoured by the presence of moisture. In those cases where an accelerating effect has been observed, a greater proportion of sulphate ions has been found in the corrosion products, and nitrogen compounds have not been detected, indicating that NO2 participates indirectly as a catalyst of the oxidation of SO2 to sulphate. [Copyright &y& Elsevier]

The atmosphere is an important transient reservoir of selenium (Se). According to recent evaluations of the global Se budget, approximately 13,000–19,000tons of Se is cycled through the troposphere annually. Most studies suggest that atmospheric deposition is an important source of Se contamination and it is therefore critical to evaluate the source emissions and fate of Se in the atmosphere. This paper presents a broad overview of current state of knowledge and understanding of major aspects of atmospheric Se and its natural and anthropogenic sources. The significant physical and chemical species encountered in the atmosphere are examined and special attention is paid to atmospheric speciation and its atmospheric pathways and processes. In addition, thermodynamic and kinetic data for atmospheric Se speciation are provided, which aid our understanding and the modelling of Se behaviour in the atmospheric environment. We also document how Se isotopes might be useful for tracing atmospheric sources and pathways. Important gaps in our current knowledge of Se in the atmospheric environment are identified, and suggestions for future research are offered. [Copyright &y& Elsevier]

Trajectory source apportionment (TSA) methods have been used in many research projects to attempt to identify the sources of pollution. Hybrid Single Particle Lagrangian Integrated Trajectories (HYSPLIT) is a popular model for use in various TSA methods. One of the options in this model is to choose a starting height. Very little research is available to assist a user in making this choice. This paper evaluates starting heights of 10, 50, 100, 250, and 500m on the accuracy of the Multi-Receptor (MURA) method using artificial sources for three different simulations. It was found that using ensembles of trajectories in the MURA method appear to average out most of the biases found from different trajectory starting heights up to the 500m tested. [Copyright &y& Elsevier]