Weekly variation of atmospheric particle micromorphology and chemistry in Brussels urban environment

The purpose of this study was to measure the impact of urban activities on airborne particle dynamics during weekend periods in Brussels urban area. Differences in the granulometry and micromorphology between particles sampled on working days and weekends were studied. We quantified the area, size, number, and the chemistry parameters of the airborne particles and compared between Saturday, Sunday, and Monday. We report and analyze data on airborne particles up to PM10, measured in the Brussels region from October 2002 to September 2003. Our investigation reveals detailed information regarding chemical composition of the airborne particles over the weekend period in the Brussels urban area. Furthermore, the majority of the airborne particles in the Brussels region may belong to sources geographically outside the (in situ) Brussels area.     

Temporal variations of airborne particles concentration in the Brussels environment

We report and analyze data on the PM10 fraction of airborne particles measured at five recording stations in the Brussels region from October 2002 till September 2003. These stations are representative of the various activity sectors of the Brussels urban area. The objective was the determination of the origin of the PM10 particles (particles up to 10 μm) that are recorded in that region in order to follow the EU directives concerning tolerance level of airborne particles concentration. In order to evaluate the impacts of local and external factors that inject solid particles in the atmosphere of Brussels we compared concentration data from working and not working (holidays) periods. Moreover, we also compared concentrations from periods of agricultural activity and rest in the Brabant provinces surrounding the Brussels region for various crop types. The results lead to the conclusion that the impact or urban traffic is rather limited while that of the agricultural activities is important. Moreover, there appears a clear-cut distinction between different types of crops.     

Methodology for identifying particle sources in indoor environments

Growing concern about airborne particles in indoor environments requires fast source identification in order to apply remedial actions. A methodology for identifying sources emitting particles larger than 0.5 microm was designed and applied. It includes: (1) visual inspection of interior surfaces in order to identify deposited particles and inspection of potential sources (equipment, materials, activities etc.) of airborne particles. (2) Technical measurements of airborne particles at different positions in a building with simultaneous logging of activities. (3) Isolating potential activities/particle sources in a test chamber, initially free from particles, for controlled characterizations of the particles generated. The methodology was applied in a study of three houses in southern Sweden. The results show that source identification is facilitated by knowledge of concentration variations between different rooms, real-time measurements together with activity reports and information on particle characteristics that are comparable with results from laboratory simulations. In the houses to which the methodology was applied, major particle emissions from textile handling were identified, which were likely due to detergent zeolite residues.     

A comprehensive method for aeolian particle granulometry and micromorphology analyses

The aim of this study was to use a new approach to investigate aeolian particle granulometry and micromorphology. Taking total aeolian deposition into account, we used parameters such as, particle area, perimeter, shape analysis for particle roughness (area/perimeter) and elongation (long/short axis). These parameters were analyzed on temporal and spatial scales at four study sites in the eastern Negev Desert, Israel. The total collection of particles was sorted into three size groups based on particle area to facilitate comparison. The classic definition of particle size (equating particle length with particle diameter) produced relatively small variations among the three size classes (25-38.6%). Our proposed comprehensive method demonstrated significant variation among the three size classes (13.9-60.8%), e.g. the classic method placed 36.4% of the particles in size class two while the new method placed 60.8% of the particles in this size class; the differences were even more significant regarding size class 3 (38.6% vs. 13.9%, respectively). The classic method did not facilitate investigation of particle roughness and elongation. With this new approach, it was possible to clearly define the particles by size class, based on these characteristics. With roughness, the variation among size classes 2 and 3 was about 27%. With elongation, the variation among size classes two and three was about 21%. Applying similar investigation method to study the aeolian particle granulometry and micromorphology can better facilitate more detailed calculation of particle size distribution, roughness and elongation.     

Metal release from stainless steel particles in vitro-influence of particle size

Human inhalation of airborne metallic particles is important for health risk assessment. To study interactions between metallic particles and the human body, metal release measurements of stainless steel powder particles were performed in two synthetic biological media simulating lung-like environments. Particle size and media strongly influence the metal release process. The release rate of Fe is enhanced compared with Cr and Ni. In artificial lysosomal fluid (ALF, pH 4.5), the accumulated amounts of released metal per particle loading increase drastically with decreasing particle size. The release rate of Fe per unit surface area increases with decreasing particle size. Compared with massive sheet metal, fine powder particles (<4 microm) show similar release rates of Cr and Ni, but a higher release rate of Fe. Release rates in Gamble's solution (pH 7.4), for all powders investigated, are significantly lower compared to ALF. No clear trend is seen related to particle size in Gamble's solution.     

Particulate Matter Over A Seven Year Period in Urban and Rural Areas Within, Proximal and Far from Mining and Power Station Operations in Greece

Lignite mining operations and lignite-fired power stations result in major particulate pollution (fly ash and fugitive dust) problems in the areas surrounding these activities. The problem is more complicated, especially, for urban areas located not far from these activities, due to additional contribution from the urban pollution sources. Knowledge of the distribution of airborne particulate matter into size fraction has become an increasing area of focus when examining the effects of particulate pollution. On the other hand, airborne particle concentration measurements are useful in order to assess the air pollution levels based on national and international air quality standards. These measurements are also necessary for developing air pollutants control strategies or for evaluating the effectiveness of these strategies, especially, for long periods. In this study an attempt is made in order to investigate the particle size distribution of fly ash and fugitive dust in a heavy industrialized (mining and power stations operations) area with complex terrain in the northwestern part of Greece. Parallel total suspended particulates (TSP) and particulate matter with an aerodynamic diameter less than 10 μm (PM10) concentrations are analyzed. These measurements gathered from thirteen monitoring stations located in the greater area of interest. Spatial, temporal variation and trend are analyzed over the last seven years. Furthermore, the geographical variation of PM10 – TSP correlation and PM10/TSP ratio are investigated and compared to those in the literature. The analysis has indicated that a complex system of sources and meteorological conditions modulate the particulate pollution of the examined area.     

Size Distribution of Aerosols (PM10) and Lead (Pb) near Traffic Intersections in Mumbai (India)

The size distribution of aerosols was measured near traffic intersections of Marol link road in air quality control region (AQCR1), which is a moderately industrial area and Dadar Khodad circle in AQCR2, which is a heavily commercial core of the Mumbai City. The reason behind selecting the two unidentical regions was to study the contribution from vehicles to the size separated PM10 and that of Pb. It is recognised that particulates in urban air are responsible for serious health effects. As very small particles are assumed to be important for the adverse health effects, the particle size distribution is thus an important factor that needs to be addressed whenever the particulates pollution is concerned. The size measurements were done with a cascade impactor of eight stages with a back-up filter. It effectively separates the particulate matter into nine-sizes ranging from 0.0-0.4 to 9.0-10.0 microm. Samples were analysed in nine-particle size fractions with special reference to a toxic metal - lead (Pb) by atomic absorption spectrophotometry (AAS). It was found that PM10 and Pb at both the intersections could easily be classified by the size distribution. The fractions of the PM10 and that of Pb showing a tendency of trimodal distributions with the first peak at coarse mode approximately 9.0-10.0 microm, second at approximately 5.8 microm and the third at coarse mode approximately1.1 microm. The significant percentage of Pb was found in the range below 2.5 microm at both the intersections. However, Pb in AQCR1 is found in the coarser range as well, which could probably be the influence of various industrial activities in the area. PM10 concentration values in the coarser range in AQCR2 are associated with the resuspension of dust particles and mechanical erosions.     

Measurements of atmospheric aerosol size distributions by co-located optical particle counters

Ambient aerosol number concentrations and size distributions were measured in both indoor and outdoor environments using two identical co-located and concurrently operated optical particle counters (OPCs). Indoor measurements were performed in a research laboratory, whereas two different locations were used for outdoor measurements; the sampling duration exceeded 12 hours and one hour respectively. Results from the two OPCs have been presented for eight size classes between 0.5 and 20 [micro sign]m, represented by central value diameters 0.875, 1.5, 2.75, 4.25, 6.25, 8.75, 12.5 and 15 microm. Overall, for the six indoor and outdoor experiments conducted at different times of day, the mean particle count ratios from the two OPCs for the individual samples showed +/-20% variation for indoor experiments and +/-50% variations for outdoor experiments. Significant random departures of the mean ratios from unity at all size classes were noticed even for indoor sample periods exceeding 20 hours. However, the coefficient of determination (R(2)) for the plots of readings from the two OPCs indicated higher consistency for "fine" particles (0.5-3.5 microm) than for "coarse" particles (10-20 microm), with average R(2) > 0.8 and R(2) < 0.5 respectively. Poisson counting statistics help to explain the divergence in the latter case where number concentrations were very low for the outdoor experiments. However, it cannot explain the divergence for indoor measurements where the concentrations were much higher. Increasing the averaging period reduced the scatter, especially in size classes with low number concentration. However, this procedure may lead to over-smoothing of data for environments with rapidly changing number concentration. These results indicate that, when two such analysers are used for comparative studies, the divergence between their responses may generate significant values of source contribution or deposition flux, even for nominally similar aerosol populations.     

Attribution of Carbon Dioxide Fluxes to Crop Types in a Heterogeneous Agricultural Landscape of Argentina

The increasing proportion of agricultural lands worldwide makes it necessary to intensify the research concerning the carbon exchange at agricultural sites. In order to determine the Net Ecosystem Exchange (NEE) in an agricultural landscape in the province of Buenos Aires, Argentina, we carried out eddy covariance measurements with a flux tower, which was placed between two agricultural fields. Therefore, the measured CO₂ flux represents the accumulated flux from both areas, i.e., from different crop types. We here present an analysis method which attributes the flux to the two crop types. For this analysis, we applied the Hsieh footprint model to identify the contributing source area to the flux measurement. We then applied a multiple regression analysis to calculate the NEE in the growing season 2011/2012 for each field separately. The pronounced differences in the time courses of the CO₂ fluxes in the two fields can be explained by the different sowing times and different growth stages of both cultivations. The time courses furthermore show that the CO₂ uptake of the plants was strongly affected by the drought which lasted from December 2011 to January 2012. For the growth cycle of maize (216 days), the NEE was ?240 g C m^?2 and for the growth cycle of soybean (154 days) ?231 g C m^?2. In order to obtain the NEE of a complete agricultural cycle (from harvest to harvest), we also considered the NEE of autumn and winter 2011. Uncertainties of the spatially partitioned NEE are quantified and discussed.     

Chemical composition and physical features of summer aerosol at Terra Nova Bay and Dome C, Antarctica

During the 2002-2003 austral summer field season, aerosol samples were collected at a coastal (Terra Nova Bay--Northern Victoria Land) and an inland site (Dome C--East Antarctic Plateau). The sampling was carried out by stacked filter units made up of two filters at different porosity (5.0 and 0.4 microm at Terra Nova Bay and 3.0 and 0.4 microm at Dome C), able to roughly separate a coarse from a fine fraction. At Dome C, a further investigation on aerosol size distribution was performed by an inertial impactor able to collect aerosol particles on 8 size classes (from 10 to 0.4 microm). Atomic Force Microscopy was applied to the filter collecting the finer fraction in both sites in order to assess the real cut-off value of the filter sandwich apparatus and to reconstruct the volume size distribution. At the employed flow conditions, the real cut-off value was revealed to be about one third with respect to the filter nominal porosity in both stations. The size distribution plots showed a bimodal distribution with a mode centered around 0.22 microm in both the sites and a second broader mode which is centered between 0.3 microm and 1.2 microm diameter at Terra Nova Bay and shifted toward higher values (centred around 1.0 microm diameter) at Dome C. Each filter was analysed for the main and trace ionic components allowing evaluation of the contributions of primary and secondary aerosol sources at the two sites as a function of the particle size class. The coastal site is mainly affected by primary and secondary marine inputs: the sea spray contribution (Na+, Mg2+, Cl- and ssSO4(2-)) is dominant (77% w/w) in the coarse fraction whereas the biogenic source (methanesulfonate and nssSO4(2-)) prevails (67.5% w/w) in the fine fraction. In this fraction a significant contribution (15.5% w/w) is provided by ammonium likely to be related to surrounding penguin colonies. Dome C atmosphere is characterised by fine particles arising from secondary sources and long-range transport processes. The main component in the fine and coarse fractions at Dome C is sulfate whose nssSO4(2-) represents the 99.5% and the 92.3%(w/w) in fine and coarse fraction, respectively. The observed agreement between nssSO4(2-) and methanesulfonate temporal profiles in the fine fraction demonstrates that biogenic emissions dominate the inland background aerosol. Results from the sampling by the 8-stage impactor at Dome C are presented here: chloride and nitrate are mainly deposited on the 10-2.1 microm stages while the highest sulfate concentration was found in the submicrometric fraction which turned out to be the most acidic. Such a distribution is able to prevent nitrate and chloride re-emission as gaseous HCl and HNO3 in the 10-2.1 microm stages, arising from the exchange reaction between chloride and nitrate salts and sulfuric acid. Moreover, the concentration peak observed for nitrate in coarser fractions is probably related also to the formation of hygroscopic NH4NO3 particles and nitrate adsorption on sea salt particles.     

江苏泰州城市霾天和沙尘天气溶胶中细菌群落结构特征研究

近年来,空气污染已成为长三角地区最关键的环境问题之一,气溶胶颗粒物(PM)是最主要的污染物之一.生物气溶胶作为颗粒物的重要组成部分,可能对空气质量和人体健康产生不利影响.利用高通量测序方法研究了江苏省泰州2019年11月至2020年1月期间发生沙尘和霾污染时生物气溶胶中细菌群落结构组成特征.结果表明:冬季沙尘天和霾天气...     

Temporal variations of airborne particle concentration in an arid region

Airborne particle concentration (APC) measurements were carried out at the Sede Boker experimental station located in the northern Negev Desert, about 50 km south of Beer Sheva, during the years 1987--1997. The basic sampling period used in 1987--1993 was 12 h (day and night) and in 1994--1997 the sampling period was 24 h. For the entire study period, the average airborne particle concentration (APC) was 123.8 microg/m3, the highest value was 4204.2 microg/m3; and the lowest, near 5 microg/m3. For the 24 h average, about 90% of the cases were defined as normal situations (APC between 0-200 microg/m3) about, 8.5%, hazy periods (APC between 200-500 microg/m3), 1.4% dusty periods (APC between 500-1000 microg/m3) and about 0.7% were intense dusty periods (APC above 1000 microg/m3). Statistical analysis of the data showed significant seasonal and monthly fluctuations. The seasonal variation of the APC was further examined using different definitions of the seasons (astronomical, meteorological, and synoptic).     

不同土地利用对溪流大型底栖无脊椎动物群落的影响

2010年4月调查了钱塘江中游区域29个样点的水环境特征和底栖动物。聚类排序将样点分为参照、农业和城镇3组,相似性分析表明不同组间底栖动物群落有显著差异(r=0.863,P=0.001)。环境因子的主成分分析表明,研究区域主要的环境胁迫是农业和城镇用地及其引起的水质变化,并能较好解释组间物种差异的关键环境胁迫因子为农业用地比例、城镇用地比例、溶解氧、总氮和平均底质得分(Rho=0.568,P=0.001)。底栖动物参数(总分类单元数、Shannon-Weaver多样性指数、BI指数和丰富度指数)和k-优势度曲线显示农业和城镇组的生物完整性遭到很大程度的破坏,且农业组较城镇组严重。     

小尺度滴灌棉田土壤硝态氮空间异质性研究

以1 m×0.8 m网格布点采集的土壤样为研究对象,从统计特征值、半方差函数和等直线图几个方面,对比分析3个时期土壤硝态氮养分的空间和时间变异特性。结果表明,各时期的变异系数受棉花的生长、田间作业影响较大。播前和收获期土壤硝态氮的空间结构符合球状模型,初花期则为线性模型,表明硝态氮含量变异是结构性与随机性共同作用的结果。硝态氮的空间变异性播前主要受结构因素影响;初花期主要受随机因素影响;收获后硝态氮含量的空间异质性变化人为因素大于结构因素。     

Dust exposure in indoor climbing halls

The use of hydrated magnesium carbonate hydroxide (magnesia alba) for drying the hands is a strong source for particulate matter in indoor climbing halls. Particle mass concentrations (PM10, PM2.5 and PM1) were measured with an optical particle counter in 9 indoor climbing halls and in 5 sports halls. Mean values for PM10 in indoor climbing halls are generally on the order of 200-500 microg m(-3). For periods of high activity, which last for several hours, PM10 values between 1000 and 4000 microg m(-3) were observed. PM(2.5) is on the order of 30-100 microg m(-3) and reaches values up to 500 microg m(-3), if many users are present. In sports halls, the mass concentrations are usually much lower (PM10 < 100 microg m(-3), PM2.5 < or = 20 microg m(-3)). However, for apparatus gymnastics (a sport in which magnesia alba is also used) similar dust concentrations as for indoor climbing were observed. The size distribution and the total particle number concentration (3.7 nm-10 microm electrical mobility diameter) were determined in one climbing hall by an electrical aerosol spectrometer. The highest number concentrations were between 8000 and 12 000 cm(-3), indicating that the use of magnesia alba is no strong source for ultrafine particles. Scanning electron microscopy and energy-dispersive X-ray microanalysis revealed that virtually all particles are hydrated magnesium carbonate hydroxide. In-situ experiments in an environmental scanning electron microscope showed that the particles do not dissolve at relative humidities up to 100%. Thus, it is concluded that solid particles of magnesia alba are airborne and have the potential to deposit in the human respiratory tract. The particle mass concentrations in indoor climbing halls are much higher than those reported for schools and reach, in many cases, levels which are observed for industrial occupations. The observed dust concentrations are below the current occupational exposure limits in Germany of 3 and 10 mg m(-3) for respirable and inhalable dust. However, the dust concentrations exceed the German guide lines for work places without use of hazardous substances. In addition, minimizing dust concentrations to technologically feasible values is required by the current German legislation. Therefore, substantial reduction of the dust concentration is required.     

Particle size distribution of aerosols and associated heavy metals in kitchen environments

Mass size distributions of total suspended particulate matter (TSPM) was measured from Sep 2002 to April 2003 in indoor kitchen environments of five locations in Jawaharlal Nehru University (JNU), New Delhi, with the help of a high volume cascade impactor. Particulate matters were separated in five different size ranges, i.e. >10.9 microm, 10.9-5.4 microm, 5.4-1.6 microm, 1.6-0.7 microm and <0.7 microm. The particle size distribution at various sites appears to follow uni-modal trend corresponding to fine particles i.e. size range <0.7 microm. The contributions of fine particles are estimated to be approximately 50% of TSPM and PM10.9, while PM10.9 comprises 80% of TSPM. Good correlations were observed between various size fractions. Regression results reveal that TSPM can adequately act as a surrogate for PM10.9 and fine particles, while PM10.9 can also act as surrogate for fine particles. The concentrations of heavy metals are found to be dominantly associated with fine particles. However, the concentration of some metals and their size distribution, to some extent is also site specific (fuel type used).     

Groundwater geochemistry and identification of hydrogeochemical processes in a hard rock region, Southern India

Hydrogeochemical investigations were carried out in Chithar River basin, Tamil Nadu, India to identify the major geochemical processes that regulate groundwater chemistry. For this study, long-term (1991–1997) and recent water quality data (2001–2002) for 30 groundwater wells spread over the study area were used to understand the groundwater geochemistry and hydrogeochemical process regulating groundwater quality. Groundwater quality data obtained from more than 400 water samples were employed. Results of electrical conductivity and chloride express large variation between minimum and maximum values and high standard deviation, which suggests that the water chemistry in the study region is not homogeneous and influenced by complex contamination sources and geochemical process. Nitrate and depth to water table expose the influences of surface contamination sources, whereas dissolved silica, fluoride and alkalinity strongly suggest the effect of rock–water interaction. In the study region, weathering of carbonate and silicate minerals and ion exchange reactions predominantly regulate major ion chemistry. Besides, the concentrations of sulphate, chloride and nitrate firmly suggest the impact of agricultural activities such as irrigation return flow, fertiliser application, etc on water chemistry in the study region.     

Evaluation of the respicon as a personal inhalable sampler in industrial environments

The Respicon has been introduced as a sampler for health related measurements of airborne contaminants at workplaces. The instrument is aimed at simultaneous collection of three health related aerosol fractions: (a) the coarser inhalable fraction, defining the aerosol fraction that may enter the nose and mouth during breathing; (b) the intermediate thoracic fraction, defining the fraction that may penetrate beyond the larynx and so reach the lung; and (c) the finer respirable fraction, defining the fraction that may penetrate to gas exchange region of the lung. The instrument has a number of features attractive to occupational hygienists: in addition to providing the three aerosol fractions simultaneously, it is light and compact enough to be used as a personal sampler. yet can be a tripod mounted for area sampling, it can provide samples not only for gravimetric analysis but also microscopic and chemical analyses; and it is also available in a photometric direct-reading version. The instrument has previously been evaluated as an area sampler and, in this mode of operation, has shown reasonable accuracy in collecting respirable, thoracic and inhalable particles, the latter up to particle diameters of ca. 80 microm. Except for some scattered unpublished data there exist no systematic investigations in the Respicon's performance when used as a personal sampler in the industrial environment. In this paper, we will report on a study of side by side comparison of the Respicon with the IOM inhalable sampler, regarded as a reference instrument for the inhalable fraction. The main study was performed at six different workplaces in a nickel refinery. Statistical analysis of the gravimetrically-determined concentration data reveals consistently lower aerosol exposure values for the Respicon as compared to the IOM sampler. The data for the nickel workplaces are compared with findings from other studies. The results are interpreted in the light of the overall results and the possibility of introducing a correction factor is discussed.     

Relationship between different size classes of particulate matter and meteorology in three European cities

Evidence on the correlation between particle mass and (ultrafine) particle number concentrations is limited. Winter- and spring-time measurements of urban background air pollution were performed in Amsterdam (The Netherlands), Erfurt (Germany) and Helsinki (Finland), within the framework of the EU funded ULTRA study. Daily average concentrations of ambient particulate matter with a 50% cut off of 2.5 microm (PM2.5), total particle number concentrations and particle number concentrations in different size classes were collected at fixed monitoring sites. The aim of this paper is to assess differences in particle concentrations in several size classes across cities, the correlation between different particle fractions and to assess the differential impact of meteorological factors on their concentrations. The medians of ultrafine particle number concentrations were similar across the three cities (range 15.1 x 10(3)-18.3 x 10(3) counts cm(-3)). Within the ultrafine particle fraction, the sub fraction (10-30 nm) made a higher contribution to particle number concentrations in Erfurt than in Helsinki and Amsterdam. Larger differences across the cities were found for PM2.5(range 11-17 microg m(-3)). PM2.5 and ultrafine particle concentrations were weakly (Amsterdam, Helsinki) to moderately (Erfurt) correlated. The inconsistent correlation for PM2.5 and ultrafine particle concentrations between the three cities was partly explained by the larger impact of more local sources from the city on ultrafine particle concentrations than on PM2.5, suggesting that the upwind or downwind location of the measuring site in regard to potential particle sources has to be considered. Also, relationship with wind direction and meteorological data differed, suggesting that particle number and particle mass are two separate indicators of airborne particulate matter. Both decreased with increasing wind speed, but ultrafine particle number counts consistently decreased with increasing relative humidity, whereas PM2.5 increased with increasing barometric pressure. Within the ultrafine particle mode, nucleation mode (10-30 nm) and Aitken mode (30-100 nm) had distinctly different relationships with accumulation mode particles and weather conditions. Since the composition of these particle fractions also differs, it is of interest to test in future epidemiological studies whether they have different health effects.     

Correlations in the chemical composition of rural background atmospheric aerosol in the UK determined in real time using time-of-flight mass spectrometry

An aerosol time-of-flight mass spectrometer (ATOFMS) was used to determine, in real time, the size and chemical composition of individual particles in the atmosphere at the remote inland site of Eskdalemuir, Scotland. A total of 51,980 particles, in the size range 0.3-7.4 microm, were detected between the 25th and 30th June 2001. Rapid changes in the number density, size and chemical composition of the atmospheric aerosol were observed. These changes are attributed to two distinct types of air mass; a polluted air mass that had passed over the British mainland before reaching Eskdalemuir, interposed between two cleaner air masses that had arrived directly from the sea. Such changes in the background aerosol could clearly be very important to studies of urban aerosols and attempts at source apportionment. The results of an objective method of data analysis are presented. Correlations were sought between the occurrence of: lithium, potassium, rubidium, caesium, beryllium, strontium, barium, ammonium, amines, nitrate, nitrite, boron, mercury, sulfate, phosphate, fluorine, chlorine, bromine, iodine and carbon (both elemental and organic hydrocarbon) in both fine (d < 2.5 microm) and coarse (d > 2.5 microm) particle fractions. Several previously unreported correlations were observed, for instance between the elements lithium, beryllium and boron. The results suggest that about 2 in 3 of all fine particles (by number rather than by mass), and 1 in 2 of all coarse particles containing carbon, consisted of elemental carbon rather than organic hydrocarbon (although a bias in the sensitivity of the ATOFMS could have affected these numbers). The ratio of the number of coarse particles containing nitrate anions to the number of particles containing chloride anions exceeded unity when the air mass had travelled over the British mainland. The analysis also illustrates that an air mass of marine origin that had travelled slowly over agricultural land can accumulate amines and ammonium.