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The atmospheric mixing state and emission rates play decisive roles in public exposure to urban air pollution. This study utilizes atmospheric radon measurements taken with the SM200 “stability monitor,” which reflect changes in the atmospheric mixing state, to evaluate and forecast air quality. Using six months (March–August 2016) of atmospheric radon measurements in Jinhua, China, we classify the nocturnal atmospheric stability conditions into four distinct categories, “well-mixed”, “weakly stable”, “moderately stable”, and “most stable”, by applying a modified radon-based stability technique. We calculate the atmospheric self-cleaning ability index (ASI) and evaluate it with the four-category stability scheme, and the results confirm that the atmospheric radon measurements reliably represent the atmospheric mixing state. Analyzing PM2.5, PM10, SO2, NO2, CO, and O3 measurements from three nearby stations during the campaign, we find that the pollutant concentrations and air quality index (AQI) values assigned using the aforementioned stability scheme are consistent with the defined atmospheric mixing states. We subsequently demonstrate that the modified radon-based stability method is suitable for targeting the most unfavorable air quality conditions and determining where the emissions originated. Finally, we propose a simple ASI-based model for predicting regional severe air pollution.

A recently-developed radon-based technique is modified to quantify the seasonal influences of atmospheric stability on urban emissions in Lanzhou, China, based on 11 months of observations at three sites with contrasting pollution characteristics. Near-surface concentrations of primary (CO, SO 2 , NO x ) and secondary (O 3 ) gas phase pollutants responded to changing atmospheric stability in markedly different ways in winter and summer, primarily because monsoonal fetch changes strongly influenced the distance between measurement sites and their nearest upwind pollutant sources, but also due to mean diurnal changes in mixing depth. Typically, morning peak primary pollution concentrations increased by a factor of 2–5 from the most well-mixed to stable conditions, whereas nocturnal ozone concentrations reduced with increasing stability due to surface loss processes and the progressively reduced coupling between the nocturnal boundary layer and overlying free atmosphere. The majority of pollution exceedance events (cf. China National Air Quality Standard guideline values) occurred in winter, when all measurement stations were downwind of the city's main pollution sources, and were directly attributed to morning periods and stable atmospheric conditions. In the sheltered valley region of Lanzhou, extremes of winter nocturnal stability states represented a change in mean nocturnal wind speed of only 0.25 m s −1 (from 0.6 to 0.85 m s −1 ). Daily-integrated PM 10 concentrations increased by a factor of 2 in winter from the most well-mixed to stable conditions, and were usually above guideline values at the industrial and residential sites for all atmospheric stability conditions. In summer, however, daily mean PM 10 exceedances usually only occurred at the industrial site, under stable conditions. Finally, a simple model – based on mean radon concentrations between 1900 and 0400 h – is proposed to predict haze conditions in the city prior to commencement of the peak morning commuting time.

The transfer of acid gases and particles from the atmosphere to the earth's surface, where they exert adverse environmental effects, is called acid deposition. Relevant removal processes occur during dry weather conditions, during the formation of clouds or by scavenging of falling rain or other hydrometeors. The first removal process is called acid dry deposition while the last two, known as rainout and washout, respectively, are lumped together into the phenomenon of acid wet deposition.

The atmospheric concentrations of gaseous HNO3, HCl and NH3 and their relative salts have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China), as part of CAREBEIJING (Campaigns of Air Quality Research in Beijing and Surrounding Region). In this study, annular denuder technique was used with integration times of 2 and 24 h to collect inorganic and soluble PM2.5 without interferences from gas-particle and particle-particle interactions. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. Fine particulate Cl−, NH4+ and SO42− exhibited distinct temporal variations, while fine particulate NO3− did not show much variation with respect to season. Daily mean concentrations of fine particulate NH4+ and SO42− were higher during summer (12.30 μg m−3 and 18.24 μg m−3, respectively) than during winter (6.51 μg m−3 and 7.50 μg m−3, respectively). Instead, daily mean concentrations of fine particulate Cl− were higher during winter (2.94 μg m−3) than during summer (0.79 μg m−3), while fine particulate NO3− showed similar variations both in winter (8.38 μg m−3) and in summer (9.62 μg m−3) periods. However, the presence of large amounts of fine particulate NO3− even in summer are due to higher local and regional concentrations of NH3 in the atmosphere available to neutralize H2SO4 and HNO3, which is consistent with the observation that the measured particulate species were neutralized. Indeed, the composition of fine particulate matter indicated the domination of (NH4)2SO4 during winter and summer periods. In addition, the high relative humidity conditions in summer period seemed to dissolve a significant fraction of HNO3 and NH3 enhancing fine particulate NO3− and NH4+ in the atmosphere. All measured particulate species showed diurnal similar patterns during the winter and summer periods with higher peaks in the early morning, especially in summer, when humid and stable atmospheric conditions occurred. These diurnal variations were affected nearly by wind direction suggesting regional and local source influences. Indeed, the fine particulate species were also correlated with NOx and PM2.5, supporting the hypothesis that the traffic may be also an important source of secondary particles.

The atmospheric concentrations of gaseous ammonia have been measured during two field campaigns in the winter and in the summer of 2007 at Beijing (China). These measurements were carried out by means of diffusion annular denuders coated with phosphorous acid. The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. The daily average NH3 concentrations were in the range of 0.20–44.38 μg/m3 and showed regular temporal variations with higher concentrations during summer and with lower during winter. The temporal trends seemed to be largely affected by air temperature because of agricultural sources. No diurnal variability was observed for gaseous NH3 levels in both winter and summer seasons. The highest ammonia value of 105.67 μg/m3 was measured in the early morning during the summer period when stable atmospheric conditions occurred. The diurnal winter and summer trends of ammonia showed a weak dependence on the air temperature and they were affected nearly by wind direction suggesting regional and local source influences. Ammonia was also correlated with the atmospheric mixing in the boundary layer, and, with NOx, CO and PM2.5 air concentrations supporting the hypothesis that the traffic may be also an important source of ammonia in Beijing.

Within the Sino-Italian environmental protection cooperation framework established in 2002, a comprehensive air quality monitoring network has been developed in urban Suzhou, a medium-sized Chinese city, in compliance with European standards (Directive 96/62/EC). This paper is among the first attempts to present a systematic and scientific analysis of benzene, toluene, and xylenes (BTX) pollution in China. It presents our analysis of BTX space-related and time-related measurement results. Background BTX concentrations were investigated by passive sampler Analyst(R) in 2003. We depicted the spatial distribution of average BTX concentrations collected from three 15-day campaigns on isoconcentration maps. This is the first time such detailed BTX concentration maps have been developed in China in a city scale. Continuous measurement of BTX by automatic gas chromatography was carried out at two fixed monitoring stations, one in an urban residential zone and one in a heavy traffic zone, from April to December 2005. The results show similar seasonal trends at both sites, the similarities reaching their greatest level in December and their lowest level in August. The average daily profile of BTX shows greater fluctuation in spring and winter with clear morning and evening peaks. Daily average benzene, toluene, and m,p-xylenes concentrations for the study period were 2.64, 11.52, and 3.52 microg m(-3), respectively. The benzene/toluene ratio we found was lower in Suzhou than those published in studies of other worldwide cities, which indicates serious levels of toluene pollution from local stationary sources. The similarities in seasonal trend and spatial distribution in these manual and automatic measurement results were compared with each other, though the concentration values differed.

The concentrations of air pollutants such as nitrogen oxides and ozone characterised by very fast chemical reactions can significantly vary within urban street-canyon due to the short distances between sources and receptor. With the primary objective to analyse this issue, NO, NO2, NOx, O3, BTX, and wind flow field were continuously measured for 1 week at two heights (a street-level yard and a 25-m-high rooftop) in an urban canyon in Suzhou (China). The yard ozone concentrations were found to be up to six times lower than on the roof. Different frequency distributions (FD), dynamical and chemical processes of the pollutant variations from yard to roof are discussed to explain the findings. The predominant factors for the dissimilar pollutant vertical diffusion at the two measurement locations were associated to dissimilar fluid-dynamic and heterogeneous removal effects that likely induced dissimilar ozone chemical processes relative to NOx and BTX precursors.

Commercially-available “stability monitors” based on in situ atmospheric radon progeny measurements remain underutilised as a tool for urban pollution studies, due in part to difficulties experienced in relating their standard output directly to the atmospheric mixing state in a consistent manner. The main confounding factor has been a lack of attention to the fact that the observed near-surface atmospheric radon concentration includes large synoptic and fetch-related components in addition to the local stability influence. Here, a technique recently developed for stability classification using a research-quality dual-flow-loop two-filter radon detector is adapted for use with a commercially-available radon-based stability monitor. Performance of the classification scheme is then tested in Lanzhou, China, a topographically-complex region renowned for low mean annual wind speeds (0.8 m s −1 ) and winter stagnation episodes. Based on an 11-month composite, a factor of seven difference is estimated between peak NO x concentrations in the city's industrial region and a rural background location under stable conditions. The radon-based scheme is evaluated against the Pasquil-Gifford “radiation” (PGR) scheme, and assigns pollutant concentrations more consistently between defined atmospheric stability states than the PGR scheme. Furthermore, the PGR scheme consistently underestimates all peak pollutant concentrations under stable conditions compared with the radon-based scheme, in some cases (e.g. CO in the industrial region) by 25%.

Nitrous acid (HNO2) and a large variety of other components were simultaneously measured in the city centre of Rome (Italy) simultaneously during the NITROCAT ground based field experiment in May/June 2001. The highest HNO2 concentrations were found under high-pressure conditions with high nocturnal atmospheric stability and high values of pollutants. After night-time formation and accumulation up to 2 ppb HNO2 were observed. The measurements confirm that during the first hours after sunrise, when hydroxyl radical (OH) production rates from other sources (photolysis of ozone and formaldehyde (HCHO)) are slow, HNO2 photolysis is the most important primary OH source in the lowest part of the troposphere; up to 1-4 x 107 OH cm-3 s-1 were estimated for that time from this source. This contributes considerably to the initiation of the photochemistry for the day. The unexpected high daytime concentrations of few hundred ppt observed by DOAS as well as by the two in-situ wet collection techniques (wet denuder/IC, coil sampling/HPLC) possibly influence ozone chemistry during the entire day. The heterogeneous on-surface production of HNO2 (and consequently of HNO3) provides also a new-type acidity formation influencing directly the biosphere and the materials. About 20% of the total nitrite was found on atmospheric aerosols. The HNO2 measurements agree well for the different in-situ measurement techniques and the spatial integration DOAS simultaneously performed over several weeks in the real atmosphere and during reaction chamber experiments.

Vertical distribution of traffic-related pollutants inside an open street-canyon were observed in Suzhou, P.R. China, in 2005. The aim was to explore transfer and diffusion characteristics of vehicular exhaust emissions, as well as monitoring constraints associated with street canyons, courtyards and enclosed spaces. Vertical wind speed was found to strongly affect the fluctuation of all the pollutants. Daily average concentrations of NO x , NO 2 and NO, as well as NO 2 /NO x ratio, were found to vary significantly alongside the vertical, proportionate to different average daily trends. Oxidation processes and photochemical activity are discussed to explain these phenomena. Daily CO trends were found to track closely with both NO x and Benzene, while the corresponding ratios were different relative to other published works. Different emission factors and driving conditions, as well as other emission sources types (especially for Benzene) are used to explain this point.

A new diffusive sampler for ozone was tested and validated in the polar troposphere at Ny-Alesund–Svalbard Islands. Measurements from the ozone diffusive samplers were compared with those of a co-located ultraviolet analyser in Ny-Alesund. The O 3 measurements made with the diffusive sampler were in a very good agreement with the measurements from the analyser, giving a linear regression line with a slope of 1.00 and a correlation coefficient of 0.83. The ratio of a 4-weeks average concentration computed from the sum of 2 subsequent 2-weeks samples to the monthly sample were used to indicate the self-consistency of the method. Results obtained in 15 subsequent runs showed a very good agreement between the average of the fortnightly and the monthly samplers, giving an average ratio equal to 0.95 with a standard deviation of 0.11.

Gas and aerosol measurements were made during the Polar Sunrise Experiment 2000 at Alert, Nunavut (Canada), using two independent denuder/filter systems for sampling and subsequent analysis by ion chromatography. Twelve to forty-eight hour samples were taken during a winter (9–21 February 2000) and a spring (17 April–5 May 2000) campaign. During the spring campaign, samples were taken at two different heights above the snow surface to investigate concentration differences. Total particulate NO3− is the most abundant inorganic nitrogen compound during Arctic springtime (mean 137.4 ng m−3). The NO3− fluxes were calculated above the snow surface to help identify processes that control snow–atmosphere exchange of reactive nitrogen compounds. We suggest that the observed fluxes of coarse particle NO3− via snow deposition may contribute to the nitrogen inventory in the snow surface. Measurements of surface snow provide experimental data that constrain the contribution of dry deposition of coarse particle NO3− to

A large set of size-resolved aerosol samples was inspected with regard to their ion balance to shed light on how the aerosol acidity changes with particle size in the lower troposphere and what implications this might have for the atmospheric processing of aerosols. Quite different behaviour between the remote and more polluted environments could be observed. At the remote sites, practically the whole accumulation mode had cation-to-anion ratios clearly below unity, indicating that these particles were quite acidic. The supermicron size range was considerably less acidic and may in some cases have been close to neutral or even alkaline. An interesting feature common to the remote sites was a clear jump in the cation-to-anion ratio when going from the accumulation to the Aitken mode. The most likely reason for this was cloud processing which, via in-cloud sulphate production, makes the smallest accumulation-mode particles more acidic than the non-activated Aitken-mode particles. A direct consequence of the less acidic nature of the Aitken mode is that it can take up semi-volatile, water-soluble gases much easier than the accumulation mode. This feature may have significant implications for atmospheric cloud condensation nuclei production in remote environments. In rural and urban locations, the cation-to-anion ratio was close to unity over most of the accumulation mode, but increased significantly when going to either larger or smaller particle sizes. The high cation-to-anion ratios in the supermicron size range were ascribed to carbonate associated with mineral dust. The ubiquitous presence of carbonate in these particles indicates that they were neutral or alkaline, making them good sites for heterogeneous reactions involving acidic trace gases. The high cation-to-anion ratios in the Aitken mode suggest that these particles contained some water-soluble anions not detected by our chemical analysis. This is worth keeping in mind when investigating the hygroscopic properties or potential health effects of ultrafine particles in polluted environments.

Measurements of gaseous and particulate inorganic trace chemicals were made in the high Arctic during springtime of three consecutive years (1997–1999) using a combination of denuders and filters for sampling and subsequent analysis by ion chromatography. Here we describe the experimental method. The analytical method is shown to be adequate for measurements of clean background air. For example, median concentrations of HBr, HNO 3 , HONO, particle NO 3 − , and particle NO 2 − were 1.1, ∼6.0, ∼4.0, 22.9, and ∼4.0 pmol mol −1 , respectively. We find that particulate species make up ca. 20% of the nitrogen budget in the Arctic. No significant correlations appear in our data between the active nitrogen species in any one given year. Because of seasonal variations, correlations appear if data from all three years are considered together.

The results of the application of the annular denuder–filter pack technique coupled with ion chromatography to the determination of atmospheric pollutants in semi-polluted and background areas are reported. The coupling of these techniques reveals a viable solution for the precise and accurate measurement of atmospheric pollutants, with discrimination of the gaseous and the particulate phase and without any mutual interconversion during the sampling phase. The sensitivity is appropriate for the determination of pollutants related to both the acid deposition and the photochemical smog phenomenon, even in semi-remote and remote areas. An interpretation of the field results in terms of chemical properties of the atmosphere is given.

Mass size distributions of major inorganic ions in aerosol particles and their atmospheric precursor gases were studied at Terra Nova Bay in Antarctica (74° 41′ 42″S, 164° 05′36 ″E) between January 30 and February 18, 1995. The mass size distributions of sulphate, the major inorganic ion, had two submicron and two supermicron modes. The accumulation mode (average mass median diameter 0.285±0.016 μn) had a very stable concentration over the whole sampling period (238.8±39.7 ng/m3). The smaller submicron mode (Aitken mode) had an averaged mass median diameter at 0.069 μm (standard deviation 0.011 μm). The existence of an Aitken mode is an indirect indication of new particle formation in the Antarctic summer atmosphere. The coarse-particle sulphate is due to the emissions of sea salt particles and their subsequent absorption of and reactions with atmospheric SO2. Ammonium was found primarily in the accumulation mode, where it probably was associated with very acidic ammonium sulphate/hydrated sulphu...

Gold and silver production in North America (included United States, Canada and Mexico) released a large amount of mercury to the atmosphere until well into this century when mercury (Hg) amalgamation was replaced by cyanide concentration. Since then, emissions from industries have been the dominant anthropogenic sources of atmospheric Hg in North America as a whole. Past Hg emissions from gold and silver extractions in North America during the 1800s do not show a clear evidence of atmospheric deposition occurred at the coring sites considered in this study. Estimated atmospheric emissions of Hg in North America peaked in 1879 (at about 1708 t yr −1 ) and 1920 (at about 940 t yr −1 ), primarily due to Hg emissions from gold and silver mining. After the Great Economic Depression (1929) Hg emissions peaked again in the 1947 (274 t yr −1 ), in 1970 (325 t yr −1 ) and in 1989 (330 t yr −1 ) as result of increased Hg emissions from industrial sources, though improvements in the emissions control technology in United States and Canada have been substantial. Estimates of total atmospheric deposition fluxes of Hg to water and terrestrial receptors were in the range of 14.3–19.8 μg m −2 yr −1 in North America as a whole, and averaged 135 μg m −2 yr −1 (global background + local emissions) in the Great Lakes. These values were in good agreement with recent estimates reported in literature. The comparison of atmospheric Hg deposition fluxes with Hg accumulation rates in sediment cores suggests that atmospheric deposition was the major source of Hg entering the lakes system at coring sites, however, important contributions to Lake Ontario sediment cores sites from 1940 to 1970 were likely originated from local point sources (i.e. direct discharges).

The atmospheric concentrations of nitrous acid (HONO) have been measured during two field campaigns in the winter and summer of 2007 at Beijing (China). The results were discussed from the standpoint of temporal and diurnal variations and meteorological effects. The daily average HONO concentrations were in the range of 0.03-2.91ppb and didn't show temporal variation between the winter and summer periods. The temporal trends seemed to be largely affected by meteorological conditions. HONO concentrations showed very typical diurnal variations during intensive winter and summer periods. Nitrogen oxides were key precursors of HONO formation and the HONO/NO2 values were higher than those reported for direct emission (

Measurements of the atmospheric mixing ratio of nitrous acid have been carried out by means of the differential optical absorption system (DOAS) during a wintertime field study carried out in the urban area of Milan (Italy). Preliminary laboratory calibration of the DOAS was carried out by making use of a standard source of pure HONO which provided an interference-free UV absorption spectrum of HONG and recalculation of the absorption cross-section of this compound. Very high HONO mixing ratios, up to values exceeding 10 ppb, were measured during the campaign. DOAS results were compared with those obtained by using the annular denuder technique and good agreement was observed during the whole measurement period. On the basis of these measurements, a study on the relationship between the dynamic conditions of the lower boundary layer and the temporal trend of HONG mixing ratio can be carried out, in order to obtain indications about the sources of this species in urban atmospheres.

Simultaneous indoor and outdoor samples collected in the Church of San Luigi dei Francesi were analyzed for nitrous acid, sulphur dioxide, nitrogen oxides and ammonia in the gas phase and for ammonium, sulphate, and nitrate ions in the particulate matter. Indoor levels of nitrogen oxide, nitrous acid and ammonia were found to largely exceed those outdoors. For NO2, and SO2 lower indoor levels were always measured, while for nitrate and sulphate, the indoor/outdoor ratios ranged from 0.5 to 3.5. These results show that indoor production of nitrous acid could result from heterogeneous reactions indoors, on the walls and exposed surfaces. Furthermore, they demonstrate that non-reactive species such as nitrogen oxide and particles penetrate indoors, where they remain segregated and are very slowly depleted, due to their small deposition velocities.

A diffusion denuder for simultaneous collection of ambient nitrogen dioxide and peroxyacetyl nitrate (PAN), based on quantitative collection on an alkaline active carbon surface, has been developed. Nitrogen dioxide yields nitrite anion whereas PAN yields nitrate which are extracted after sampling with water and analysed by ion chromatography. Laboratory and field tests concerning sorption efficiency, effect of humidity and capacity were carried out. The pre-exponential and exponent for the first term of the Gormley-Kennedy equation applied to annular geometry were estimated. It was found that for PAN the agreement between the experimental and calculated values is quite good and compatible with a “perfect sink” behaviour of carbon, whereas, in the case of NO 2 , the experimental collection efficiency is lower than theory but still suitable for ambient sampling. Nitrogen oxide and ozone do not interfere in the determination. SO 2 , HONO and HNO 3 which could interfere can be removed by using two diffusion denuders placed in line before the carbon denuder: one coated with tetrachloromercurate (TCM), for the removal of SO 2 and HNO 3 , and the second, coated with carbonate, for the removal of HONO. The detection limit for 24 h sampling is better than 0.05 and 0.06 ppb for NO 2 and PAN, respectively. The response for NO 2 was compared during a field campaign in Milan with the corresponding integrated response of a chemiluminescence analyser, while data for PAN were compared with the integrated response of a GC-ECD technique. The results obtained are reported and discussed.

The measurement of atmospheric trace components relevant to atmospheric chemistry, in gas phase and particulate matter, was carried out in the Antarctica troposphere during the Antarctic summer 1990–91. The determinations were carried out by sampling air through a diffusion denuder/filter pack sampling system, followed by extraction and analysis by ion chromatography. Through the analysis of the mass distribution of anions, an accurate and sensitive method for the measurement of several important species was provided. Results show that sulfur dioxide, nitric acid, sulfates, nitrates and other significant compounds might be well characterized, even at concentration levels as low as a few parts per trillions, thus providing a highly significant and consistent data set for the study of polar atmospheric chemistry.

The relationship between tropospheric ozone and growth of radish plants during Summer 1991 in an urban and in a semi-rural site located in Central Italy are analyzed. Largest ozone concentrations and largest radish growth reductions are found n the semi-rural site. The importance of integrating the information on physico-chemical processes with biological monitoring to estimate the impact of photochemical oxidants on natural and cultivated vegetation in the Mediterranean area is discussed. Results from photochemical episodes are also reported in terms of physico-chemical evaluation of atmospheric pollutants.

A denuder technique for the determination of nitric acid and particulate nitrate is described. The technique relies on the use of four annular denuders set in series followed by a downstream filter-pack, and allows the reliable and accurate measurement of gaseous nitric acid, coarse nitrate and fine nitrate, even in the presence of high concentration levels of other nitrogen gaseous species and in case of high particulate to gaseous phase ratio. Field data collected by using the described system in extreme conditions, ranging from very polluted areas to extremely remote sites, are discussed. The data are analyzed in terms of mass distribution of the analyte on the different stages of the set-up; time resolution, minimum detectable concentration and precision of the measurements are also discussed.

Purpose This paper presents a novel approach to interpret ground-level O3with the measured atmospheric stability index (ASI). Methods O3 concentrations were monitored by automatic analysers at three types of stations: traffic site, residential site and regional background site in 2005, and the ASI was simultaneously measured by observing radon and its short-lived decay products. Results The observed results showed a clear annual variation of O3 concentrations with a maximum in spring, relatively high at the regional background site over 120 ppb, and lower at the residential and traffic sites at about 70 ppb. ASI gives information about the dilution properties of the lower boundary layer and allows to highlight the relevant role of the dilution factor in determining atmospheric pollution events. We demonstrated the analysis of O3 night peak episodes with vertical wind and ASI. Conclusions With the advantage of ASI and vertical wind profiles, it was possible to isolate particular photochemical pollution phenomena of O3 peaks from the free troposphere reservoir or formed by local reactions. This shows that the index constitutes a powerful and valuable tool for describing O3 night-peak episodes at background station.

A 5-day intercomparison of measurement techniques for nitric acid and particulate nitrate was carried out at the Area della Ricerca di Roma (Montelibretti, Rome, Italy) during September 18–24, 1988. Sixteen groups from eleven European countries participated in the experiment, intercomparing the performances of several denuder and filter pack systems. In order to obtain a better characterization of the performance of each technique, in addition to HNO 3 and NO 3 − field sampling, the protocol included HNO 3 determinations from a pure source and temporal self-consistency tests. Many ancillary measurements were also undertaken, which proved to be of help in the interpretation of the data. The evaluation of the results is not performed through a simple linear regression of the data, that is by assessing agreement or disagreement between pairs of methods, but by comparing the results obtained in both the additional tests and the field samplings with the predicted deposition pattern. Once the reliability of each single technique has been evaluated in the light of the potential interfering mechanisms, a comparison between the results yielded by groups using the same technique and, finally, different techniques is carried out. The application of these criteria to the data set gathered during the intercomparison shows that the diffusion techniques yield the most reliable results, while teflon-nylon filter packs do not allow a correct discrimination between nitric acid and nitrate, particularly in the presence of high ammonium nitrate concentrations. Filter packs using a cellulose prefilter are only able to measure total nitrate.

Indoor and outdoor pollutant concentrations were measured simultaneously in the Galleria degli Uffizi in Florence. SO2, HNO3, HONO and O3 in the gas phase and sulphate, nitrate and ammonium in particulate matter were measured. Indoor and outdoor values were similar. The indoor/outdoor ratios for all the pollutants, with the exception of HONO, were extremely variable ranging from 0.1 to 0.9. For HONO the indoor levels have been found to largely exceed those outdoor. The results show that indoor HONO production could result from heterogenous reactions on the walls and exposed surfaces which could include artworks giving rise to dry acid deposition of nitric acid.

Four different types of carbonaceous material (active carbon, graphitized carbon black, source samples from a power plant and from an urban heating boiler) were exposed to synthetic gas mixtures of SO2 and SO2 + NO2 in sub-ppm ranges at two different relative humidities (60 and 90% r.h.). The interaction of SO2 and NO2 with the carbonaceous materials led to sulfate and to three other products: NO, HONO and NO2−. Formation of NO and NO2− was observed only on active carbon while the other three materials yielded HONO. It was also found that NO2 enhances the deposition of SO2 only on the source sample from the power plant at 60% r.h., whereas the material from the urban heating boiler had no effect both at low and high r.h. The results obtained show that no general statements on the effect of NO2 on the heterogeneous reaction of SO2 on these carbonaceous materials can be made and also that NO2 reactions in the presence of SO2 on carbon-containing surfaces should be considered as a source for the production of HONO in the urban environment.

The environmental impact of Notte Bianca (White Night) holidays held during September 2007 in Rome, Italy, was investigated by measuring aerial concentrations of several genotoxic, psychotropic or source-dependent organic pollutants. Chemical characterization of airborne particulates collected concurrently at Montelibretti RM (semi-rural locality lying approximately 30 km NE of Rome centre) was used as a reference. n-Alkanes, polynuclear aromatic hydrocarbons (PAH) and nitrogen/oxygen-containing polyaromatic compounds (PAC) did not seem to undergo important enhancements during the holiday celebration, whilst recreational drugs peaked downtown (87 vs 41 pg m(-3), on the average, of cocaine, and 5.0 vs. 2.6 ng m(-3) of nicotine). By contrast, a simultaneous raising of aerial drugs was not detected at Montelibretti.

Air quality improvement in rapidly developing countries like China requires to generate valuable data with high-level of representativeness to be transformed into useful information about air pollution. However, the problem of monitoring representativeness has been overlooked. In this respect, a comprehensive methodology to monitor air quality has been developed by this Institute, engaged since 2001 in several projects in China dealing with air quality. The new approach requires rearranging the existing monitoring strategies. In short, saturation monitoring is employed to preliminary assess air pollution and provide spatial resolution over the study area. Automatic monitoring is reduced to a minimum to make time-related data available. The information so-measured with high degree of both spatial and temporal resolution, are completed by statistical and mathematical modelling to generate data interpretation schemes. This methodology extensively tested in China during these years has been found to be very useful for macro/micro-designing emission and air quality monitoring networks, apportioning emission sources, assessing spatial representativeness of measurements, and evaluating spatial frequency distributions of air pollutants. Case-studies of Suzhou, Lanzhou and Beijing are presented to discuss these findings.

Road transport has become by far the major source of environmental pollution and traffic congestion in urban areas. Though a lot of research has been done to investigate the functional relationship linking air quality and air pollution from transport, a further improvement in the knowing of this relationship is needed. The aim of this study was to analyze this relationship and to develop a more flexible framework to allow communication between transport emissions and air quality concentrations. This paper describes the development of this framework, suggests methodological tools to mitigate its problems and shows its application to the mega-city of Beijing, in P.R. China. The result of implementing this methodology would be a system providing high time/space resolution measurements of both air pollutant concentrations and traffic emissions data, as well as real-time transportation and dispersion modelling of those data. The key advantage of the system proposed would be the runtime integration of modelling, to interpret the data measured, with measurements, to validate the data modelled. The findings from the case-study of Beijing show that the integrated system can link traffic air pollution measurements through various modelling modules in order to automate transport-related air pollution assessment.

A field evaluation between two annular denuder configurations was conducted during the spring of 2003 in the marine Arctic at Ny-Alesund, Svalbard. The IIA annular denuder system (ADS) employed a series of five single-channel annular denuders, a cyclone and a filter pack to discriminate between gas and aerosol species, while the EPA-Versatile Air Pollution Sampler (VAPS) configuration used a single multi-channel annular denuder to protect the integrity of PM2.5 sample filters by collecting acidic gases. We compared the concentrations of gaseous nitric acid (HNO3), nitrous acid (HONO), sulfur dioxide (SO2) and hydrochloric acid (HCl) measured by the two systems. Results for HNO3 and SO2 suggested losses of gas phase species within the EPA-VAPS inlet surfaces due to low temperatures, high relative humidities, and coarse particle sea-salt deposition to the VAPS inlet during sampling. The difference in HNO3 concentrations (55%) between the two data sets might also be due to the reaction between HNO3 and NaCl on inlet surfaces within the EPA-VAPS system. Furthermore, we detected the release of HCl from marine aerosol particles in the EPA-VAPS inlet during sampling contributing to higher observed concentrations. Based on this work we present recommendations on the application of denuder sampling techniques for low-concentration gaseous species in Arctic and remote marine locations to minimize sampling biases. We suggest an annular denuder technique without a large surface area inlet device in order to minimize retention and/or production of gaseous atmospheric pollutants during sampling.

Atmospheric pollutants, whether man made or naturally occurring but released in greater concentrations due to man's activities, can now be found at all latitudes and longitudes throughout the boundary layer, and depending on their resistance to photolysis and photo-oxidants, within both the free troposphere and stratosphere. The key to pollutant transport is longevity of the compound concerned and the circulation patterns of the atmosphere. Pollutants that are relatively unreactive and volatile will, with time, be spread across the globe, eventually reaching even the most remote areas. Even semi-volatile pollutants can be transported by successive phases of volatilisation and deposition (multi-hop) until they too are spread across the globe. One of the implications of this world-wide distribution is that pollutants may reach areas where specific climatic, physical or chemical conditions occur that result in increased deposition fluxes to marine and terrestrial surfaces, with the consequence that pollution hot spots may be created at vast distances from the original pollution source. The Polar regions, particularly the Arctic because it is in the same hemisphere as the major industrialised nations, are a good example. Levels of persistent organic pollutants (POPs) and mercury (Hg) in polar wildlife, particularly larger predators, have been known for some time to be higher than the norm at lower latitudes. Mercury is deposited in the Arctic, not just because of its reduced volatility due to low temperatures, but also as a result of specific atmospheric chemical conditions related to the tropospheric ozone depletion events. These events, prompted by the so-called ‘Bromine Explosion,’ which releases reactive halogen compounds to the troposphere, create conditions in which the atmospheric oxidation of Hg(g)0 occurs with such rapidity that its concentration can fall below detectable limits in a matter of hours. The oxidation products that are much more soluble than elemental Hg are deposited along with particulate matter or dry deposited, and at a time (around polar dawn) when the Arctic ecosystem is entering an active phase with the return of sunlight. There is evidence that Hg released by coal-burning power stations in China can be deposited in rain along the Pacific coast of the U.S. Hg released in the U.S. could potentially be transported with other atmospheric pollutants across the Atlantic to Europe and the Mediterranean. Industrial emissions in northern Europe due to the general north to south flow of the boundary layer air in summer months have a negative effect on Mediterranean air quality (high O3 concentrations) and it seems, on atmospheric Hg deposition to the Mediterranean Sea. If the description above seems rather qualitative it is because as yet the tools with which to model (and to a certain extent measure) atmospheric transport, transformation, deposition and re-emission on such a scale are in their infancy. There is a great need for strategically situated monitoring stations, creating a network to sample within the major air mass trajectories, not only at ground level but also at altitude. This would allow models and the emission inventories of pollutant fluxes to be validated in a far more comprehensive manner than isolated measurement campaigns permit. From validated models, it would then be possible to evaluate the potential effects of changing emissions resulting from legislation or changes in, for example, the power generation industry towards renewable energy sources. Finally, it would be possible also to investigate changes in pollution transport and deposition that occur with changing atmospheric transport patterns resulting from climate change.

Measurements of atmospheric and snow mixing ratios of nitrates and nitrites and their fluxes above the snow surface were made during two intensive campaigns during spring time 2001 at Ny-Ålesund, Svalbard as part of the EU project "`The NItrogen Cycle and Effects on the oxidation of atmospheric trace species at high latitudes' (NICE). At this coastal site close to the unseasonably unfrozen fjord, of the measured nitrogen species, only HNO3 showed a significant flux on to the snow surface; a mean deposition of -8.7 nmol h-1 m-2 was observed in late April / early May 2001. These fluxes may be due to the reaction of HNO3 with sea salt, and especially NaCl, or may be simply uptake of HNO3 by ice, which is alkaline because of the sea salt in our marine environment. During snowfall periods dry deposition of HNO3 may contribute up to 10% of the N budget in the snow; however, the main source for N is wet deposition in falling snow. The surface snow at Ny-Ålesund showed very complex stratigraphy; the NO3- mixing ratio in snow varied between 65 and 520 ng g-1, the total NO3- content of the snowpack was on the order of 2700 ng cm-2. In comparison the atmospheric boundary layer column showed a NO3- content of only 8 ng cm-2. The limited exchange, however, between the snow and the atmosphere was attributed to low mobility of NO3- in the observed snow. Contrary to other Arctic sites (i.e. Alert, Nunavut or Summit, Greenland) deposition of sea salt and crustal aerosols in this marine environment made the surface snow alkaline; snow NO3- was associated with heavier cations and was not readily available for physical exchange or photochemical reactions.

Passive sampling technique was used to preliminary assess the spatial and temporal distribution of air pollution in Suzhou (P.R. China) in 2003, with the aim to determine the representativeness of zones where to monitor air quality. 100 sites were selected to measure 15-days average concentrations of SO2, NOx, NO2, O-3, NH3, Benzene, Toluene and Xylene in winter and summer. The distribution trend of NO and NO2, as well as the ratio of NO2/NOx was used to identify the heavy traffic polluted zones and design a network of monitoring stations (macrositing). NO2/NOx ratios varied throughout the two selected seasons and from site to site clearly demonstrating the different extent and completeness of NO -> NO2 oxidation processes in time and space. The exceedance frequencies of pollutants was used to design the type of monitoring equipment to be installed at each station (micrositing). An air quality monitoring network composed by 9 monitoring stations has been finally established in 2004 according to the result of this Survey and is now currently running.

Nitrogen oxides (NO 2 and NO x ), sulphur dioxide (SO 2 ), and benzene, toluene, xylene (BTX) in ambient air were preliminarily assessed, by diffusive sampling technique, in 2003 through three measurement campaigns at 100 locations in the Chinese city of Suzhou. Statistical analysis of space series so-generated was performed to infer source contributions and frequency distributions (FD). It was found that nitrogen oxides, benzene and xylene were mostly emitted from motor vehicles; in contrast, industrial sources were a major contributor to sulfur and toluene pollution. Normal FD (NFD) described significantly SO 2 in summer and NO 2 and NO x in autumn (95% confidence interval); on the contrary, BTX presented a most peculiar FD rather different to the NFD. Lognormal distribution was often unacceptable. Predominant factors influencing FDs and its normality were found to be associated to those elements conditioning air pollutant diffusion: meteorology (wind speed and direction), relevant emission sources (especially for toluene), emission seasonality (mainly for SO 2 and NO x ), and photochemistry (mainly for NO 2 and xylene).

Measurements of snow surface—atmosphere exchange fluxes of nitrous acid at Ny-Alesund, Svalbard during springtime confirmed earlier findings that no significant emissions occurred from alkaline snow surfaces at this marine high Arctic location. On 29 April 2004 air arriving from the North Pole brought both ozone depleted air and significant snowfall. On that day we observed HONO emission fluxes of up to 40...ese emissions were made possible by the combination of two independent phenomena. The acidic snow allowed the transport of NO3 ions to photochemically reactive areas and the release of produced HONO from the snow interstitial air; while the absence of ozone likely increased the HONO/NO fraction over that of NO2 in the snow interstitial air. r 2005 Elsevier Ltd. All rights reserved.