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Ammonia (NH 3) in the atmosphere affects both the environment and human health. It is therefore increasingly recognised by policy makers as an important air pollutant that needs to be mitigated, though it still remains unregulated in many countries. In order to understand the effectiveness of abatement strategies, routine NH 3 monitoring is required. Current reference protocols, first developed in the 1990s, use daily samplers with offline analysis; however, there have been a number of technologies developed since, which may be applicable for high time resolution routine monitoring of NH 3 at ambient concentrations. The following study is a comprehensive field intercomparison held over an intensively managed grassland in southeastern Scotland using currently available methods that are reported to be suitable for routine monitoring of ambient NH 3. In total, 13 instruments took part in the field study, including commercially available technologies, research prototype instruments, and legacy instruments. Assessments of the instruments' precision at low concentrations (< 10 ppb) and at elevated concentrations (maximum reported concentration of 282 ppb) were undertaken. At elevated concentrations, all instruments performed well and with precision (r2 > 0.75). At concentrations below 10 ppb, however, precision decreased, and instruments fell into two distinct groups, with duplicate instruments split across the two groups. It was found that duplicate instruments performed differently as a result of differences in instrument setup, inlet design, and operation of the instrument. New metrological standards were used to evaluate the accuracy in determining absolute concentrations in the field. A calibration-free CRDS optical gas standard (OGS, PTB, DE) served as an instrumental reference standard, and instrument operation was assessed against metrological calibration gases from (i) a permeation system (ReGaS1, METAS, CH) and (ii) primary standard gas mixtures (PSMs) prepared by gravimetry (NPL, UK). This study suggests that, although the OGS gives good performance with respect to sensitivity and linearity against the reference gas standards, this in itself is not enough for the OGS to be a field reference standard, because in field applications, a closed path spectrometer has limitations due to losses to surfaces in sampling NH 3 , which are not currently taken into account by the OGS. Overall, the instruments compared with the metrological standards performed well, but not every instrument could be compared to the reference gas standards due to incompatible inlet designs and limitations in the gas flow rates of the standards. This work provides evidence that, although NH 3 instrumentation have greatly progressed in measurement precision, there is still further work required to quantify the accuracy of these systems under field conditions. It is the recommendation of this study that the use of instruments for routine monitoring of NH 3 needs to be set out in standard operating protocols for inlet setup, calibration, and routine maintenance in order for datasets to be comparable. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) in the atmosphere affects both the environment and human health. It is therefore increasingly recognised by policy makers as an important air pollutant that needs to be mitigated. In order to understand the effectiveness of abatement strategies, routine NH3 monitoring is required. Current reference protocols, developed in the 1990s, use daily samplers with offline analysis but there have been a number of technologies developed since, which may be applicable for high time resolution routine monitoring of NH3 at ambient concentrations. The following study is a comprehensive field inter comparison held over an intensively managed grassland in South East Scotland using currently available methods that are reported to be suitable for routine monitoring of ambient NH3. In total 13 instruments took part in the field study. The instruments include: an online ion chromatography system (MARGA, Metrohm-Applikon, NL), two wet chemistry continuous flow analysis systems (AiRRmonia, Mechatronics, NL), a photoacoustic spectrometer (NH3 monitor, LSE, NL), two mini Differential Optical Absorption Spectrometers (miniDOAS; NTB Interstate University of Applied Sciences Buchs, now part of "Eastern Switzerland University of Applied Sciences, CH and RIVM, NL), as well as seven spectrometers using cavity enhanced techniques: a Quantum Cascade Laser Absorption Spectrometer (QCLAS, Aerodyne, Inc. US), Picarro G2103 Analyzer (Picarro US), Economical NH3 Analyser (Los Gatos Research, US), Tiger-i 2000 (Tiger Optics, US) and LaserCEM® gas analyser (AP2E, FR). Assessments of the instruments’ precision at low concentrations (< 10 ppb) and at elevated concentrations (maximum reported concentration of 282 ppb) were undertaken. At elevated concentrations all instruments performed well on precision (r² > 0.75). At concentrations below 10 ppb however, instruments fell into two distinct groups and the duplicate instruments, miniDOAS, AiRRmonia, LGR and Picarro were split across the two groups. It was found that identical instruments performed differently at low concentrations, highlighting the impact of the setup, inlet design and operation of the instrument used. Accuracy in determining absolute concentrations in the field was assessed using a calibration-free CRDS Optical Gas Standard (OGS, PTB, DE), serving as an instrumental reference standard. Accuracy was also assessed using well established metrological standards for calibration gases, i) a permeation system (ReGaS1, METAS, CH) and ii) Primary Standard gas Mixtures (PSMs) prepared by gravimetry (NPL, UK). This study showed that though the OGS good performance with respect to sensitivity and linearity with reference gas standards, this in itself is not enough for the OGS to be a field reference standard because a closed path spectrometer has limitations due to losses to surfaces in sampling NH3, which need to be taken into account. Overall, the instruments studied performed well against the standard gases but we note that not every instrument could be calibrated using gas standards due to incompatible inlet designs and limitations in the gas flow rates of the standards. This work provides evidence that though NH3 instrumentation have greatly progressed in measurement precision, there is still further work required to quantify the accuracy of these systems under field conditions. It is the recommendation of this study that the use of instruments for routine monitoring of NH3 needs to be set out in standard operating protocols for inlet set-up, calibration and routine maintenance, in order for datasets to be comparable. [ABSTRACT FROM AUTHOR]

Aerosol particles play an important role in the microphysics of clouds and hence in their likelihood to precipitate. In the changing climate already-dry areas such as the United Arab Emirates (UAE) are predicted to become even drier. Comprehensive observations of the daily and seasonal variation in aerosol particle properties in such locations are required, reducing the uncertainty in such predictions. We analyse observations from a 1-year measurement campaign at a background location in the United Arab Emirates to investigate the properties of aerosol particles in this region, study the impact of boundary layer mixing on background aerosol particle properties measured at the surface, and study the temporal evolution of the aerosol particle cloud formation potential in the region. We used in situ aerosol particle measurements to characterise the aerosol particle composition, size, number, and cloud condensation nuclei (CCN) properties; in situ SO2 measurements as an anthropogenic signature; and a long-range scanning Doppler lidar to provide vertical profiles of the horizontal wind and turbulent properties to monitor the evolution of the boundary layer. Anthropogenic sulfate dominated the aerosol particle mass composition in this location. There was a clear diurnal cycle in the surface wind direction, which had a strong impact on aerosol particle total number concentration, SO2 concentration, and black carbon mass concentration. Local sources were the predominant source of black carbon as concentrations clearly depended on the presence of turbulent mixing, with much higher values during calm nights. The measured concentrations of SO2 , instead, were highly dependent on the surface wind direction as well as on the depth of the boundary layer when entrainment from the advected elevated layers occurred. The wind direction at the surface or of the elevated layer suggests that the oil refineries and the cities of Dubai and Abu Dhabi and other coastal conurbations were the remote sources of SO2. We observed new-aerosol-particle formation events almost every day (on 4 d out of 5 on average). Calm nights had the highest CCN number concentrations and lowest κ values and activation fractions. We did not observe any clear dependence of CCN number concentration and κ parameter on the height of the daytime boundary layer, whereas the activation fraction did show a slight increase with increasing boundary layer height due to the change in the shape of the aerosol particle size distribution where the relative portion of larger aerosol particles increased with increasing boundary layer height. We believe that this indicates that size is more important than chemistry for aerosol particle CCN activation at this site. The combination of instrumentation used in this campaign enabled us to identify periods when anthropogenic pollution from remote sources that had been transported in elevated layers was present and had been mixed down to the surface in the growing boundary layer. [ABSTRACT FROM AUTHOR]

Aerosol particles play an important in role in the microphysics of clouds and hence on their likelihood to precipitate. In the changing climate already dry areas such as the United Arab Emirates (UAE) are predicted to become even drier. Comprehensive observations of the daily and seasonal variation in aerosol particle properties in such locations are required reducing the uncertainty in such predictions. We analyse observations from a one-year measurement campaign at a background location in the United Arab Emirates to investigate the properties of aerosol particles in this region, study the impact of boundary layer mixing on background aerosol particle properties measured at the surface and study the temporal evolution of the aerosol particle cloud formation potential in the region. We used in-situ aerosol particle measurements to characterise the aerosol particle composition, size, number and cloud condensation nuclei (CCN) properties, in-situ SO2 measurements as an anthropogenic signature and a long-range scanning Doppler lidar to provide vertical profiles of the horizontal wind and turbulent properties to monitor the evolution of the boundary layer. Anthropogenic sulphate dominated the aerosol particle mass composition in this location. There was a clear diurnal cycle in the surface wind direction, which had a strong impact on aerosol particle total number concentration, SO2 concentration and black carbon mass concentration. Local sources were the predominant source of black carbon, as concentrations clearly depended on the presence of turbulent mixing, with much higher values during calm nights. The measured concentrations of SO2, instead, were highly dependent on the surface wind direction as well as on the depth of the boundary layer when entrainment from the advected elevated layers occurred. The wind direction at the surface or of the elevated layer suggests that the cities of Dubai, Abu Dhabi and other coastal conurbations were the remote sources of SO2. We observed new aerosol particle formation events almost every day (on four days out of five on average). Calm nights had the highest CCN number concentrations and lowest κ values and activation fractions. We did not observe any clear dependence of CCN number concentration and κ parameter on the height of the daytime boundary layer, whereas the activation fraction did show a slight increase with increasing boundary layer height, due to the change in the shape of the aerosol particle size distribution where the relative portion of larger aerosol particles increased with increasing boundary layer height. We believe that this indicates that size is more important than chemistry for aerosol particle CCN activation at this site. The combination of instrumentation used in this campaign enabled us to identify periods when anthropogenic pollution from remote sources that had been transported in elevated layers was present, and had been mixed down to the surface in the growing boundary layer. [ABSTRACT FROM AUTHOR]

The Station for Measuring Ecosystem–Atmosphere Relations (SMEAR) II is well known among atmospheric scientists due to the immense amount of observational data it provides of the Earth–atmosphere interface. Moreover, SMEAR II plays an important role for the large European research infrastructure, enabling the large scientific community to tackle climate- and air-pollution-related questions, utilizing the high-quality long-term data sets recorded at the site. So far, this well-documented site was missing the description of the seasonal variation in aerosol chemical composition, which helps understanding the complex biogeochemical and physical processes governing the forest ecosystem. Here, we report the sub-micrometer aerosol chemical composition and its variability, employing data measured between 2012 and 2018 using an Aerosol Chemical Speciation Monitor (ACSM). We observed a bimodal seasonal trend in the sub-micrometer aerosol concentration culminating in February (2.7, 1.6, and 5.1 µgm-3 for the median, 25th, and 75th percentiles, respectively) and July (4.2, 2.2, and 5.7 µgm-3 for the median, 25th, and 75th percentiles, respectively). The wintertime maximum was linked to an enhanced presence of inorganic aerosol species (ca. 50 %), whereas the summertime maximum (ca. 80 % organics) was linked to biogenic secondary organic aerosol (SOA) formation. During the exceptionally hot months of July of 2014 and 2018, the organic aerosol concentrations were up to 70 % higher than the 7-year July mean. The projected increase in heat wave frequency over Finland will most likely influence the loading and chemical composition of aerosol particles in the future. Our findings suggest strong influence of meteorological conditions such as radiation, ambient temperature, and wind speed and direction on aerosol chemical composition. To our understanding, this is the longest time series reported describing the aerosol chemical composition measured online in the boreal region, but the continuous monitoring will also be maintained in the future. [ABSTRACT FROM AUTHOR]

We measured amine and guanidine emission rates from a boreal forest floor in Finland with 1-h time resolution, using an online ion chromatograph (instrument for Measuring AeRosols and Gases in Ambient air - MARGA) coupled with an electrospray ionization-quadrupole mass spectrometer (MS). MARGA-MS was connected to a closed dynamic flow-through poly(methyl methacrylate) chamber. Chamber recovery for the emission measurements was tested semi-quantitatively for monomethyl-, dimethyl- and trimethylamine (MMA, DMA and TMA), and the results were 19 %, 29 % and 24 %, respectively. MMA, DMA and TMA showed maximum emission rates in July, but the highest emission rates for guanidine were in April, when snow was melting. The MMA, DMA and TMA emission rates also clearly varied diurnally, especially in July with maxima at afternoon. Diethylamine (DEA) also showed higher emission rates, with clear diurnal cycles in July. Other amine emission rates were mostly below the detection limits. The temperature dependencies of the emissions were studied, and we noted a correlation between the emission rates and chamber temperature (Tchamber). Especially in July emission rates of DMA followed Tchamber measured two hours earlier and guanidine showed a similar pattern. On the other hand, the TMA emission rates correlated with Tchamber measured at the same time. This could be due to lower vaporizing temperature of TMA. Emission rates of DMA and TMA showed some air temperature (Tair) dependency, but for MMA dependency was not as clear. [ABSTRACT FROM AUTHOR]

The Station for Measuring Ecosystem Atmosphere Relations (SMEAR) II is well known among atmospheric scientists due to the immense amount of observational data it provides of the earth-atmosphere interface. Moreover, SMEAR II plays an important role in large European research infrastructures, enabling the large scientific community to tackle climate and air pollution related questions, utilising the high-quality long-term data sets recorded at the site. So far, the well-documented site was missing the description of the seasonal variation of aerosol chemical composition that is crucial for understanding the complex biogeochemical and -physical processes governing the forest ecosystem. Here, we report the sub-micron aerosol chemical composition and its variability utilising data measured between 2012 and 2018 using an Aerosol Chemical Speciation Monitor (ACSM). We observed a bimodal seasonal trend in the sub-micron aerosol concentration culminating in February (2.7, 1.6, 5.1 μg m-3 for median, 25th, 75th percentiles, respectively) and July (4.2, 2.2, and 5.7 μg m-3 for median, 25th, 75th percentiles, respectively). The wintertime maximum was linked to an enhanced presence of inorganic aerosol species (ca. 50 %) whereas the summertime maximum (ca. 80 % organics) to biogenic secondary organic aerosol (SOA) formation. During the exceptionally hot Julys of 2014 and 2018, the organic aerosol concentrations were up to 70 % higher than the 7-year July mean. The projected increase of heat wave frequency over Finland will most likely influence the loading and chemical composition of aerosol particles in the future. Our findings suggest strong influence of meteorological conditions such as radiation, ambient temperature, wind speed and direction on aerosol chemical composition. To our understanding, this is the longest time series reported describing the aerosol chemical composition measured online in the boreal region, but the continuous monitoring will be maintained also in the future. [ABSTRACT FROM AUTHOR]

New particle formation (NPF) provides a large source of atmospheric aerosols, which affect the climate and human health. In recent chamber studies, ion-induced nucleation (IIN) has been discovered as an important pathway of forming particles; however, atmospheric investigation remains incomplete. For this study, we investigated the air anion compositions in the boreal forest in southern Finland for three consecutive springs, with a special focus on H2SO4-NH3 anion clusters. We found that the ratio between the concentrations of highly oxygenated organic molecules (HOMs) and H2SO4 controlled the appearance of H2SO4-NH3 clusters (3 < no.S < 13): all such clusters were observed when [HOM] = [H2SO4] was smaller than 30. The number of H2SO4 olecules in the largest observable cluster correlated with the probability of ion-induced nucleation (IIN) occurrence, which reached almost 100% when the largest observable cluster contained six or more H2SO4 molecules. During selected cases when the time evolution of H2SO4-NH3 clusters could be tracked, the calculated ion growth rates exhibited good agreement across measurement methods and cluster (particle) sizes. In these cases, H2SO4-NH3 clusters alone could explain ion growth up to 3 nm (mobility diameter). IIN events also occurred in the absence of H2SO4-NH3, implying that other NPF mechanisms also prevail at this site, most likely involving HOMs. It seems that H2SO4 and HOMs both affect the occurrence of an IIN event, but their ratio ([HOMs] = [H2SO4]) defines the primary mechanism of the event. Since that ratio is strongly influenced by solar radiation and temperature, the IIN mechanism ought to vary depending on conditions and seasons. [ABSTRACT FROM AUTHOR]

We measured amines in boreal forest air in Finland both in gas and particle phases with 1 h time resolution using an online ion chromatograph (instrument for Measuring AeRosols and Gases in Ambient Air – MARGA) connected to an electrospray ionization quadrupole mass spectrometer (MS). The developed MARGA-MS method was able to separate and detect seven different amines: monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA), propylamine (PA), and butylamine (BA). The detection limits of the method for amines were low (0.2–3.1 ng m−3), the accuracy of IC-MS analysis was 11–37 %, and the precision 10–15 %. The proper measurements in the boreal forest covered about 8 weeks between March and December 2015. The amines were found to be an inhomogeneous group of compounds, showing different seasonal and diurnal variability. Total MMA (MMA(tot)) peaked together with the sum of ammonia and ammonium ions already in March. In March, monthly means for MMA were  <  2.4 and 6.8 ± 9.1 ng m−3 in gas and aerosol phases, respectively, and for NH3 and NH4+ these were 52 ± 16 and 425 ± 371 ng m−3, respectively. Monthly medians in March for MMA(tot), NH3, and NH4+ were  <  2.4, 19 and 90 ng m−3, respectively. DMA(tot) and TMA(tot) had summer maxima indicating biogenic sources. We observed diurnal variation for DMA(tot) but not for TMA(tot). The highest concentrations of these compounds were measured in July. Then, monthly means for DMA were  <  3.1 and 8.4 ± 3.1 ng m−3 in gas and aerosol phases, respectively, and for TMA these were 0.4 ± 0.1 and 1.8 ± 0.5 ng m−3. Monthly medians in July for DMA were below the detection limit (DL) and 4.9 ng m−3 in gas and aerosol phases, respectively, and for TMA these were 0.4 and 1.4 ng m−3. When relative humidity of air was  >  90 %, gas-phase DMA correlated well with 1.1–2 nm particle number concentration (R2 = 0.63) suggesting that it participates in atmospheric clustering. EA concentrations were low all the time. Its July means were  <  0.36 and 0.4 ± 0.4 ng m−3 in gas and aerosol phases, respectively, but individual concentration data correlated well with monoterpene concentrations in July. Monthly means of PA and BA were below detection limits at all times. [ABSTRACT FROM AUTHOR]

We measured amines in boreal forest air in Finland both in gas and particle phase with 1-hour time resolution using an online ion chromatograph (instrument for Measuring AeRosols and Gases in Ambient Air, MARGA) connected to an electrospray ionization quadrupole mass spectrometer (MS). The measurements covered about 8 weeks between March 2015 and December 2015. With MARGA-MS we were able to separate and detect 7 different amines: monomethylamine (MMA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA), propylamine (PA) and butylamine (BA). The amines were found to be an inhomogeneous group of compounds, showing different seasonal and diurnal variability. Total MMA peaked together with the sum of ammonia and ammonium ion already in March, possibly due to evaporation from melting snow and ground. In March monthly means for MMA were < 2.4 ng m-3 and 6.8 ± 9.1 ng m-3 in gas and aerosol phase, respectively, and for NH3 and NH4+, 52 ± 16 ng m-3 and 425 ± 371 ng m-3, respectively. Monthly medians in March for MMA, NH3 and NH4+, were < 2.4 ng m-3, 19 ng m-3 and 90 ng m-3 respectively. DMA and TMA had summer maxima indicating biogenic sources. We observed diurnal variation for DMA but not for TMA. The highest concentrations of these compounds were measured in July. In July monthly means for DMA were < 3.1 ng m-3 and 8.4 ± 3.1 ng m-3 in gas and aerosol phase, respectively, and for TMA 0.4 ± 0.1 ng m-3 and 1.8 ± 0.5 ng m-3. Monthly medians in July for DMA were < DL and 4.9 ng m-3 in gas and aerosol phase, respectively, and for TMA 0.4 ng m-3 and 1.4 ng m-3. When relative humidity of air was > 90%, gas phase DMA correlated well with 1.1-2 nm particle number concentration (R² = 0.63) suggesting that it participates in new particle formation. 0.63-EA concentrations were low all the time, July means were <0.36 ng m-3 and 0.4 ± 0.4 ng m-3 in gas and aerosol phase respectively, but they correlated well with monoterpene concentrations in July. Monthly means of PA and BA were all the time below detection limits. [ABSTRACT FROM AUTHOR]

We report flow tube measurements of the effective sulfuric acid diffusion coefficient at ranges of different relative humidities (from ~4 to 70%), temperatures (278, 288 and 298 K) and initial H2SO4 concentrations (from 1 × 106 to 1 × 108 molecules·cm-3). The measurements were carried out under laminar flow of humidified air containing trace amounts of impurities such as amines (few ppt), thus representing typical conditions met in Earth's continental boundary layer. The diffusion coefficients were calculated from the sulfuric acid wall loss rate coefficients that were obtained by measuring H2SO4 concentration continuously at seven different positions along the flow tube with a chemical ionization mass spectrometer (CIMS). The wall loss rate coefficients and laminar flow conditions were verified with additional computational fluid dynamics (CFD) model FLUENT simulations. The determined effective sulfuric acid diffusion coefficients decreased with increasing relative humidity, as also seen in previous experiments, and had a rather strong power dependence with respect to temperature, around ∝ T5.6, which is in disagreement with the expected temperature dependence of ~T1.75 for pure vapours. Further clustering kinetics simulations using quantum chemical data showed that the effective diffusion coefficient is lowered by the increased diffusion volume of H2SO4 molecules via a temperature-dependent attachment of base impurities like amines. Thus, the measurements and simulations suggest that in the atmosphere the attachment of sulfuric acid molecules with base molecules can lead to a lower than expected effective sulfuric acid diffusion coefficient with a higher than expected temperature dependence. [ABSTRACT FROM AUTHOR]

European Committee for Standardisation (CEN) Technical Committee 264 ‘Air Quality’ has recently produced a standard method for the measurements of anions and cations in PM2.5 within its Working Group 34 in response to the requirements of European Directive 2008/50/EC. It is expected that this method will be used in future by all Member States making measurements of the ionic content of PM2.5. This paper details the results of a field measurement campaign and the statistical analysis performed to validate this method, assess its uncertainty and define its working range to provide clarity and confidence in the underpinning science for future users of the method. The statistical analysis showed that, except for the lowest range of concentrations, the expanded combined uncertainty is expected to be below 30% at the 95% confidence interval for all ions except Cl−. However, if the analysis is carried out on the lower concentrations found at rural sites the uncertainty can be in excess of 50% for Cl−, Na+, K+, Mg2+ and Ca2+. An estimation of the detection limit for all ions was also calculated and found to be 0.03 μg m−3 or below. [ABSTRACT FROM AUTHOR]

The Pallas area in northern Finland has served as a meteorological monitoring site for 80 years and, more recently, as a platform for atmospheric, ecological and hydrological research. Currently, Pallas comprises one of the most important research infrastructures in Finland and in the wider circumpolar region. Moreover, it is a successful example of the benefits obtained from scientific cooperation and integration among disciplines. This paper is an introduction to a special issue that collates studies related to greenhouse gas fluxes and concentrations, atmospheric aerosols and air pollutants, which were presented at the Fourth Pallas Symposium held in 2013. We give an overview of the historical and current research activities within the Pallas area, outline the most important infrastructure projects and list the recent literature that has originated from the various scientific programs and projects. The results of these activities are illustrated in this paper with examples of long-term data sets on variations in soil, lake and river water, air quality and greenhouse gas concentrations. [ABSTRACT FROM AUTHOR]

In a boreal forest environment at Hyytiälä (SMEAR II station), Finland, from 21 June 2010 to 31 April 2011, concentrations of gases (HCl, HNO3, HONO, NH3, SO2) and inorganic ions (Cl-, NO3-, SO42-, NH4+, Na+, K+, Mg2+, Ca2+) in PM10 and PM2.5 particles were measured with an on-line ion chromatograph MARGA 2S. The MARGA data were compared with those of the filter samples and the Aerosol Mass Spectrometer. The linear-regression slopes derived from MARGA against the filter data were 0.98, 1.08, 0.50 and 1.31 for SO2, SO42-, HNO3 and NO3-, respectively. The respective coefficients of determination (r²) were 0.89, 0.90, 0.70 and 0.93. After installing a concentration column, improved values of cation slopes of 1.00, 1.19, 0.88, 1.00, 0.73 and 0.89 for NH3, NH4+, Na+, K+, Mg2+, and Ca2+, respectively, were obtained. The corresponding coefficients of determination (r²) were: 0.79, 0.83, 0.95, 0.90, 0.85 and 0.62. According to these results, traditional filter collection can be replaced with the MARGA instrument at background sites, if a concentration column is used at least for the cations. This would improve the temporal resolution of the observations. The average concentrations of nitrogen-containing gases were highest in the summer (NH3: 0.47 ppb, HNO3: 0.10 ppb and HONO: 0.11 ppb), which can be explained by the higher temperatures and increased amounts of sunlight followed by stronger agricultural and soil-related sources. In the summer, clear diurnal cycles were found in all N-containing gases, but in the winter the concentrations remained low most of the time and no diurnal cycles were observed. The concentration of ammonia was found to depend exponentially on the prevailing temperature, the increase with temperature being strongest in dry conditions. [ABSTRACT FROM AUTHOR]

Effect of four different base compounds [ammonia (NH3), monomethyl-(MMA), dimethyl- (DMA) and trimethylamine (TMA)] on sulphuric-acid-water nucleation was studied using a laminar flow tube. The concentration and size distribution of freshly-formed particles were monitored with an Ultrafine Condensation Particle Counters (UCPC) and a Differential Mobility Particle Sizer (DMPS) system. Two separate experiments were conducted. In the first experiment, the sulphuric acid concentration was measured using a mass spectrometer and the amount of base compound input was determined. In the second experiment, the concentration of base compounds in the flow tube was directly measured with an online ion chromatograph. All experiments were conducted at the constant temperature of 298 K and relative humidity of 30%, as well as constant sulphuric acid concentration. The concentration of the added base compounds was increased stepwise from 27 up to 25 000 pptv. An enhancement of the particle nucleation rate was observed only with TMA, and the maximum enhancement factor (EF) was approximately 5.5 at the TMA concentration of 2500 pptv. The possible nucleation enhancement by the other base substances was most probably saturated due to background contaminant levels of DMA, MMA and NH3. Detection of the base compounds was discussed, and the results obtained in this study were compared with those from other similar laboratory experiments found in literature. [ABSTRACT FROM AUTHOR]

The precipitation chemistry of nearly 30 acidifying compounds, base cations and several trace elements was monitored in the Valkea-Kotinen catchment in southern Finland during 1988-2011. Measurements of the atmospheric concentration of SO2, NO2 and O3 covered a shorter period. Temporal trends in the components are presented. A notable finding was an indication of a possible increase in the bulk deposition of Cd and NO3-. The effect of the changing nitrate deposition on the hydrological continuum of groundwater is also briefly discussed. The transport of air masses to the Valkea-Kotinen catchment was estimated and binds all the results presented in this issue to the development in the emission patterns in Europe. [ABSTRACT FROM AUTHOR]

Several studies have shown that combustion-derived fine particles cause adverse health effects. Previous toxicological studies on combustion-derived fine particles have rarely involved multiple endpoints and a detailed characterization of chemical composition. In this study, we developed a novel particle sampling system for toxicological and chemical characterization (PSTC), consisting of the Dekati Gravimetric Impactor (DGI) and a porous tube diluter. Physico-chemical and toxicological properties of the particles emitted from various combustion sources were evaluated in two measurement campaigns. First, the DGI was compared with the High-Volume Cascade Impactor (HVCI) and to the Dekati Low-Pressure Impactor (DLPI), using the same dilution system and the same sampling conditions. Only small differences were observed in the mass size distributions, total particulate matter (PM), and particulate matter with diameter smaller than 1 um (PM) concentrations and geometric mass mean diameters (GMMD) between these three impactors. Second, the PSTC was compared with the HVCI sampling system, which has been optimal for collection of particulate samples for toxicological and chemical analyses. Differences were observed in the mass size distributions, total PM and PM emissions, and GMMDs, probably due to the different sampling and dilution methods as well as different sampling substrates which affected the behavior of semi-volatile and volatile organic compounds. However, no significant differences were detected in the in vitro measurements of cytotoxicity between the samples collected with the PSTC and the HVCI systems. In measurements of genotoxicity, significant differences between the two sampling systems were seen only with the particles emitted from the sauna stove. In conclusion, due to compact size, PSTC is an applicable method for use in particle sampling as part of the toxicological and chemical characterization of particulate emissions from different combustion sources. It offers some advantages compared to the previously used high-volume sampling methods including compactness for field measurements, simple preparation of sample substrates and high extraction efficiency. [ABSTRACT FROM AUTHOR]

There is increasing demand for renewable energy and the use of biodiesel in traffic is a major option when implying this increment. We investigated the toxicological activities of particulate emissions from a nonroad diesel engine, operated with conventional diesel fuel (EN590), and two biodiesels: rapeseed methyl ester (RME) and hydrotreated fresh vegetable oil (HVO). The engine was operated with all fuels either with or without catalyst (DOC/POC). The particulate matter (PM1) samples were collected from the dilution tunnel with a high-volume cascade impactor (HVCI). These samples were characterized for ions, elements, and polycyclic aromatic hydrocarbon (PAH) compounds. Mouse RAW264.7 macrophages were exposed to the PM samples for 24 h. Inflammatory mediators, (TNF-α and MIP-2), cytotoxicity, genotoxicity, and oxidative stress (reactive oxygen species [ROS]) were measured. All the samples displayed mostly dose-dependent toxicological activity. EN590 and HVO emission particles had larger inflammatory responses than RME-derived particles. The catalyst somewhat increased the responses per the same mass unit. There were no substantial differences in the cytotoxic responses between the fuels or catalyst use. Genotoxic responses by all the particulate samples were at same level, except weaker for the RME sample with catalyst. Unlike other samples, EN590-derived particles did not significantly increase ROS production. Catalyst increased the oxidative potential of the EN590 and HVO-derived particles, but decreased that with RME. Overall, the use of biodiesel fuels and catalyst decreased the particulate mass emissions compared with the EN590 fuel. Similar studies with different types of diesel engines are needed to assess the potential benefits from biofuel use in engines with modern technologies. [ABSTRACT FROM AUTHOR]

The concentration of reduced nitrogen in the air declined in 1990-2007 at the Finnish background stations in the southern and central parts of the country. The annual mean values, the summer mean values and the winter mean values declined by 35%-60%. In 2007 the annual mean values were 0.1-0.14 μg N M-3. The data from Utö and Oulanka were analysed in transport sectors. At both stations, the foreign contribution from the southern, southwestern and western sectors was dominant in the reduced nitrogen concentrations. In Utö, the ammonium concentration decreased in the air arriving from the sectors extending from the south to the west and in the air transported from the east. In Oulanka, the concentration did not decrease in any of the transport sectors. However, the exposure of reduced nitrogen from the west declined at both sited. In Utö, this was due to the decline in both the ammonium concentration and the frequency of western transport. In Oulanka, the reduced exposure was due to a shift of air transport from the west to the north. [ABSTRACT FROM AUTHOR]

Residential wood combustion is a significant particulate emission source in many European countries. Especially for fine particle emissions in wood combustions, the lacking knowledge of emission factors (FE) makes assessment of their contribution to ambient concentrations difficult. One reason for the discrepancy between modeled and measured contributions is many variables involved in combustion process. In this study, the fine particulate matter (PM) emissions coming from batch combustion of birch wood in a small masonry heater were investigated. The experiments were carried out in the specified conditions (normal and smouldering combustion, NC and SC, respectively). To enable various chemical analytical techniques, two sampling combinations for PM2.5 (particle diameter < 2.5 um), and size-segregated sampling were used. The samples were analyzed for gravimetric mass, major ions, monosaccharide anhydrides (MA, including levoglucosan, galactosan and mannosan), trace elements, elemental carbon (EC) and water-insoluble and -soluble particulate organic matter (WISPOM and WSPOM, respectively). FE of PM2.5 based on gravimetric mass was three times higher for SC than for NC. Particulate organic matter (POM = 1.6 x OC) accounted for approximately 30% and 70% of FE of PM2.5 in NC and SC, respectively. The corresponding values for EC were 32% and 25%. About 30% of the OC was water-soluble. Ions constituted about 20% of the FE of PM2.5 in NC but only a few percents in SC. Potassium comprised around 60% of the analyzed ions. The fraction of trace elements consisting 94% of Zn was only about 1% of the total PM2.5 emissions. This study showed strong influence of combustion practice on emissions of the major chemical components from the small-scale wood combustion. [ABSTRACT FROM AUTHOR]