Assessing decadal changes in rainwater alkalinity at a rural Mediterranean site in the Montseny Mountains (NE Spain)

Annual volume-weighted mean (VWM) concentrations in rainwater collected at La Castanya (LC, Montseny Mountains, NE Spain) were analysed from 1983 to 2000 to study the temporal trends in precipitation chemistry, and the causes behind the changes. A significant positive correlation was found between annual rainwater SO₄²⁻ concentrations at LC and Spanish SO₂ emissions (r=0.73, P=0.0008) both decreasing remarkably during this period. Rainwater alkalinity increased during the period, shifting from negative values at the beginning (VWM in the 5 initial years=−2.7 μeq l⁻¹) to alkaline values in recent years (VWM in the 5 final years=18.0 μeq l⁻¹). Stepwise regression analysis indicated that 88% of the variation of alkalinity could be accounted for by the variability of non-marine Ca²⁺ and non-marine SO₄²⁻, with a more prominent dependence on Ca²⁺.Rains of African provenance were highly enriched in alkalinity and Ca²⁺, but no significant increases in their occurrence were found for the study period. Because of the reported higher dust updraft in northern Africa during years of high North Atlantic Oscillation (NAO) index, we also explored the relationship between rainwater variables associated with an African provenance and NAO. Annual precipitation was inversely related to NAO (r=−0.61, P=0.007). The annual wet deposition of African dust-related elements showed no correlation with NAO, probably because wet deposition of these elements depends on two factors (precipitation and dust updraft) which have opposite behaviour with respect to NAO. We hypothesise that dry deposition of African dust during dry spells (not sampled in this study) might be higher during high NAO-index years.     

Chemical and strontium isotope characterization of rainwater in karst virgin forest,Southwest China

Strontium isotope ratios and concentrations of Ca²⁺, NH₄⁺, Na⁺, K⁺, Mg²⁺, Cl^?, SO₄^2?, NO₃^? and Al³⁺, Sr²⁺ were measured for 52 rainwater samples collected in virgin forest in a rural region between May 2007 and Dec. 2008. The rainwater pH values vary from 4.1 to 7.2 with a volume weight mean (VWM) value of 5.40. 40 of 52 samples have pH value above 5.0, indicating that the regional rainwater was not acidic. Among anions and cations, sulphate concentration (40.4 μeq l^?1, VWM) is the highest in the rainwater, followed by ammonium and calcium (30.2 and 20.8 μeq l^?1, VWM). Rainwater quality is characterized by low salinity and neutralized pH.The chemical compositions and ⁸⁷Sr/⁸⁶Sr ratios of the rainwater samples vary considerably. Using Na⁺ concentration as an indicator of marine origin, the proportions of sea salt and crustal elements were estimated from elemental ratios. The ⁸⁷Sr/⁸⁶Sr ratios were used to characterize different sources base on the data sets of this study and those from literatures. Such sources include weathering of limestone (⁸⁷Sr/⁸⁶Sr = 0.7075), remote soil dust (⁸⁷Sr/⁸⁶Sr > 0.7135) and anthropogenic source (fertilizers: ⁸⁷Sr/⁸⁶Sr = 0.7079). The results of the present study suggest that one likely source for high ammonium and calcium concentration is local soil. Due to a large contribution of these cations to the sulphate neutralization action, the rainwater in this region displays non-acidity, and thus has not significant environmental impact. The wet precipitation in the karst virgin forest in Guizhou province is strongly influenced by natural sources rather than anthropogenic sources.     

Air concentrations and wet deposition of major inorganic ions at five non-urban sites in China, 2001–2003

Air and precipitation measurements at five sites were undertaken from 2001 to 2003 in four different provinces in China, as part of the acid rain monitoring program IMPACTS. The sites were located in Tie Shan Ping (TSP) in Chongqing, Cai Jia Tang (CJT) in Hunan, Lei Gong Shan (LGS) and Liu Chong Guan (LCG) in Guizhou and Li Xi He (LXH) in Guangdong. The site characteristics are quite varied with TSP and LCG located relatively near big cites while the three others are situated in more regionally representative areas. The distances to urban centres are reflected in the air pollution concentrations, with annual average concentrations of SO₂ ranging from 0.5 to above 40 μg S m⁻³. The main components in the airborne particles are (NH₄)₂SO₄ and CaSO₄. Reduced nitrogen has a considerably higher concentration level than oxidised nitrogen, reflecting the high ammonia emissions from agriculture. The gas/particle ratio for the nitrogen compounds is about 1:1 at all the three intensive measurement sites, while for sulphur it varies from 2.5 to 0.5 depending on the distance to the emission sources. As in air, the predominant ions in precipitation are sulphate, calcium and ammonium. The volume weighted annual concentration of sulphate ranges from about 70 μeq l⁻¹ at the most rural site (LGS) to about 200 μeq l⁻¹ at TSP and LCG. The calcium concentration ranges from 25 to 250 μeq l⁻¹, while the total nitrogen concentration is between 30 and 150 μeq l⁻¹; ammonium is generally twice as high as nitrate. China's acid rain research has traditionally been focused on urban sites, but these measurements show a significant influence of long range transported air pollutants to rural areas in China. The concentration levels are significantly higher than seen in most other parts of the world.     

Seasonal variability of formaldehyde production from photolysis of rainwater dissolved organic carbon

Photochemical production of formaldehyde (HCHO) was measured in rainwater from 13 precipitation events in Wilmington, North Carolina, USA under conditions of simulated sunlight. HCHO concentrations increased in all samples irradiated with no changes observed in dark controls. HCHO photoproduction rates were strongly correlated with dissolved organic carbon (DOC) suggesting HCHO was derived from direct or indirect photolysis of rainwater DOC. The higher photoproduction rates (0.03–2.9 μM h^?1) relative to those reported for surface waters suggests that rainwater DOC is more photolabile in terms of HCHO production than surface waters. HCHO photoproduction rates were higher in growing season (1.0 ± 1.0 μM h^?1) compared to non-growing season (0.08 ± 0.05 μM h^?1) even when rates were normalized for DOC (6.8 ± 3.6 μM h^?1 mM C^?1 versus 1.8 ± 1.0 μM h^?1 mM C^?1). The higher growing season rate may be related to seasonal differences in the composition of DOC as evidenced by differences in fluorescence per unit carbon of rainwater samples. Irradiation of C18 extracts of rainwater also produced HCHO, but at lower rates compared to corresponding whole rain samples, suggesting that hydrophyllic components of rainwater play a role in HCHO photoproduction. Our results indicate that photolysis of rainwater DOC produces significant amounts of HCHO, and possibly other low molecular weight organic compounds, likely increasing its reactivity and bioavailability.     

Isotopes as tracers of sources of lead and strontium in aerosols (TSP & PM2.5) in Beijing

Even after its being phased out in gasoline in the late 90s, lead (Pb) is still present at relatively high levels in the atmosphere of Beijing, China (0.10–0.18 μg m^?3). Its origin is subject to debate as several distinct sources may contribute to the observed pollution levels. This study proposes to constrain the origin(s) of Pb and strontium (Sr) in aerosols, by coupling both Pb and Sr isotope systematics. The characterisation of the main pollution sources (road traffic, smelters, metal refining plants, coal combustion, cement factories, and soil erosion) shows that they can unambiguously be discriminated by the multi-isotope approach (²⁰⁶Pb/²⁰⁴Pb and ⁸⁷Sr/⁸⁶Sr). The study of total suspended particulates (TSP) and fine particles (PM_2.5) from Beijing and its vicinity indicates that both size fractions are controlled by the same sources. Lead isotopes indicate that metal refining plants are the major source of atmospheric lead, followed by thermal power stations and other coal combustion processes. The role of this latter source is confirmed by the study of strontium isotopes. Occasionally, emissions from cement plants and/or input from soil alteration are isotopically detectable.     

Biogenic emission of dimethylsulfide (DMS) from the North Yellow Sea,China and its contribution to sulfate in aerosol during summer

Seawater, atmospheric dimethylsulfide (DMS) and aerosol compounds, potentially linked with DMS oxidation, such as methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO₄^2?) were determined in the North Yellow Sea, China during July–August, 2006. The concentrations of seawater and atmospheric DMS ranged from 2.01 to 11.79 nmol l^?1 and from 1.68 to 8.26 nmol m^?3, with average values of 6.20 nmol l^?1 and 5.01 nmol m^?3, respectively. Owing to the appreciable concentration gradient, DMS accumulated in the surface water was transferred into the atmosphere, leading to a net sea-to-air flux of 6.87 μmol m^?2 d^?1 during summer. In the surface seawater, high DMS values corresponded well with the concurrent increases in chlorophyll a levels and a significant correlation was observed between integrated DMS and chlorophyll a concentrations. In addition, the concentrations of MSA and nss-SO₄^2? measured in the aerosol samples ranged from 0.012 to 0.079 μg m^?3 and from 3.82 to 11.72 μg m^?3, with average values of 0.039 and 7.40 μg m^?3, respectively. Based on the observed MSA, nss-SO₄^2? and their ratio, the relative biogenic sulfur contribution was estimated to range from 1.2% to 11.5%, implying the major contribution of anthropogenic source to sulfur budget in the study area.     

Analysis of Hong Kong daily bulk and wet deposition data from 1994 to 1995

Results from a 1-year daily rainwater sampling program, employing both wet and bulk deposition samplers with replicate samples, from 1994 to 1995 in Hong Kong are presented and analysed. Analyte concentrations were found to vary over a wide range of several orders of magnitude, with [H⁺] for example, from 0.16 to 208.9 μeq dm^-3. Diurnal pH values less than 3.83 were measured on five occasions. A significant correlation between pH and lognormal windspeed has been found. This is taken to indicate the minor importance of long-range transport in determining rainwater acidity, since local pollutant emissions accumulate and react under conditions of atmospheric stability in the sub-tropical climate. The H⁺ wet deposition flux onto a polythene surface was 90 meq m^-2 yr^-1 during 1994–1995 at City University. Dry deposition exerts a neutralizing influence upon the acidity from this wet deposition. Although paired t-tests indicated significant differences between the bulk versus wet deposition datasets for cations, but not anions, the dataset means consequently showed such large standard deviations that t-tests indicated no significant differences. In rainwater, the charges from SO^2-₄ and NO^-₃ anions seldom balance the proton charges, implying that they are also derived from solubilization of primary and secondary airborne Ca²⁺, Mg²⁺ and NH⁺₄ particulate matter in rainwater. Use of the [SO^2-₄]/[NO^-₃] ratios in rainwater in fingerprinting pollutant origins has drawbacks, but is generally indicative of a predominantly regional contribution of these secondary pollutants to rainwater. Bulk deposition pH in Hong Kong would be in the region of 4.1 if basic Ca²⁺ compounds alone did not neutralize acidity. The regional rainout pH, inferred after exhaustive below-cloud scavenging, is about 5. The temporal trends in Hong Kong rainwater acidity are blurred.     

Relationship between precipitation chemistry and meteorological situations at a rural site in NE Spain

Bulk precipitation samples were collected at Montseny (Catalonia, NE Spain) from 1983 to 1994 and analysed for major cations and anions. The samples were classified for provenance based on meteorological synoptic maps and back trajectory analysis to identify the source areas of pollutants in precipitation. The meteorological classification was compared to an independent grouping based on multivariate data analysis (Clustering and Principal Component Analysis). Alkaline rain (mean pH=7.2) was associated to African trajectories. Local events produced neutral rains (mean pH=5.5). Acid rain was associated to rains of Atlantic origin (mean pH=4.8) and to European rains (mean pH=4.4), which also presented the highest mean concentrations of NH⁺₄ (57 μeq ℓ^-1), NO^-₃(49 μeq ℓ^-1) and SO^2-₄(103 μeq ℓ^-1). However, European events were only a small fraction of the total precipitation (10% of the cases). Marine rains accounted for 52% of the events, and African and Local for 20 and 18%, respectively. During the 11 year period there was a decreasing trend for the frequency of European events.     

Spatial and chemical patterns of PM10 in road dust deposited in urban environment

Recent research interest has been focused on road dust resuspension as one of the major sources of atmospheric particulate matter in an urban environment. Given the dearth of studies on the variability of the PM₁₀ fraction of road deposited sediments, our understanding of the main factors controlling this pollutant is incomplete. In the present study a new sampling methodology was devised and applied to collect PM₁₀ deposited mass from 1 m² of road pavement. PM₁₀ road dust fraction was sampled directly from active traffic lanes at 23 sampling sites during a campaign in Barcelona (Spain) in June 2007. The aim of the study was to gain more insight into the variability of mass and chemistry of road dust in different urban environments, such as the city centre, ring roads, and locations nearby demolition/construction sites. The city centre showed values of PM₁₀ road dust within a range of 3–23 mg m^?2, whereas levels reached 24–80 mg m^?2 in locations affected by transport of uncovered heavy trucks. The largest dust loads were measured in the proximity of demolition/construction sites and the harbor entry with values up to 328 mg m^?2.The city centre road dust profiles (%) were enriched in OC, EC, Fe, S, Cu, Zn, Mn, Cr, Sb, Sn, Mo, Zr, Hf, Ge, Ba, Pb, Bi, SO₄^2?, NO₃^?, Cl^? and NH₄⁺, but several crustal components such as Ca, Ti, Na, and Mg were also considerably concentrated. Locations affected by construction and demolition activities had high levels of crustal components such as Ca, Li, Sc, Sr, Rb and also As whereas ring roads, characterized by a higher load of uncovered heavy trucks showed an intermediate composition.Levels of PM₁₀ components per area were also evaluated to quantify the resuspendable amount of each element from 1 m². In the inner city environment mean values of 1363 μg Ca m^?2, 816 μg OC m^?2, 239 μg EC m^?2, 13 μg Cu m^?2, 12 μg Zn m^?2, 1.9 μg Sb m^?2 and 2.0 μg Pb m^?2, in PM₁₀ in all cases, were registered.Moreover the deposited PM load at demolition/construction sites acts as a reservoir or trap for traffic-related particles, which gives rise to large amounts of hazardous pollutants, available for resuspension.     

Wet deposition of low molecular weight mono- and di-carboxylic acids,aldehydes and inorganic species in Los Angeles

About 60 rainwater samples were collected at west Los Angeles, California in 1981–1984 and were analyzed for C₁–C₉ monocarboxylic acids (0.33–79 μM, average (av.) 13±15 μM), C₂–C₁₀ dicarboxylic acids (2.9–51 μM, av. 7.5±14 μM) and C₁–C₄ aldehydes (0.85–28 μM, av. 9.2±11 μM). Distributions of monocarboxylic acids show a predominance of formic (average concentration: 6.5 μM) and acetic (av. 5.6 μM) acids followed by propionic acid (av. 0.44 μM). Oxalic acid is the dominant diacid (av. 3.9 μM) followed by succinic acid (av. 1.0 μM). Formaldehyde (av. 6.9 μM) is the dominant aldehyde, with the next most abundant, acetaldehyde, being minor (av. 0.65 μM). For select rain samples described in this paper, were found to comprise monocarboxylic acids 0.9–12.3% (av. 4.4±3.4%), diacids comprise 1.2–9.5% (av. 4.2±3.3%) and aldehydes comprise 0.2–6.2% (av. 2.1±2.2%) of total organic carbon (TOC, 2.0–18.6 mg C l⁻¹; av. 9.8±5.4 mg C l⁻¹). Annual rain fluxes of monocarboxylic acids and aldehydes during 1982–1983 were calculated to be 0.24 and 0.11 g m⁻² yr⁻¹, respectively, with an annual estimated wet deposition in the Los Angeles Basin of 3120 and 1430 tons, respectively. These fluxes are equivalent to 2500 times of the acids and 2.5 times of the aldehydes emitted from automobile exhausts in the Los Angeles air basin. This comparison suggests that major portions of the carboxylic acids detected in the rain are not directly emitted from auto-exhausts, but are most likely produced in the atmosphere by gaseous and/or aqueous phase photo-induced reactions.     

Interannual variability of methanesulfonate in rainwater at Amsterdam Island (Southern Indian Ocean)

Methanesulfonate (MS⁻), an exclusive oxidation product of dimethylsulfide (DMS), has been analyzed in rainwater at Amsterdam Island (37°50′S 77°32′E) in the Southern Indian Ocean from 1991 to 1999. Rainwater MS⁻ concentrations range from 0.004 to 4.59 μmol l⁻¹ with a volume weighted mean value of 0.24 μmol l⁻¹ and present a well distinguished seasonal variation with higher values in summer, in line with the seasonal variation of its gaseous precursor (DMS), which was measured on a daily basis since 1990. The interannual variability of MS⁻ in rainwater follows closely that of DMS, indicating that MS⁻ in rainwater can be used as a surrogate to study long-term variations of atmospheric DMS, and further confirms the findings of Sciare et al. (J. Geophys. Res. 105 (2000a) 26 369), that large-scale anomalies occurred in the biogenic sulfur cycle in the Southern Indian Ocean during the studied period. Furthermore, on a monthly basis, the MS⁻ anomalies in the rainwater were found to be closely related to sea-surface temperature (SST) anomalies. The correlation between MS⁻ and SST is consistent with that observed between gaseous DMS and SST in the area and indicates an important coupling between the oceanic and the atmospheric compartments of the biogeochemical sulfur cycle.     

Exposure to cadmium in male urban and rural workers and effects on FSH,LH and testosterone

ObjectiveThis cross-sectional study was conducted to assess the relationship between exposure to cadmium and circulating reproductive hormone levels in urban and rural male workers.Materials and MethodsUrinary cadmium, blood cadmium, luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone were obtained from 86 non-smoking traffic policemen and 86 subjects working as roadmen in a rural area. All subjects were monitored to evaluate airborne exposure to cadmium.ResultsThe mean value of exposure to cadmium was 1.3 ng m^?3 in traffic policemen, while the mean value was less than 0.5 ng m^?3 in roadmen. The mean concentrations of urinary cadmium (1.4 vs. 0.9 μg g^?1 creatinine; p = 0.001), blood cadmium (1.1 vs. 0.7 μg l^?1; p = 0.000), FSH (2.6 vs. 3.2 μlU ml^?1; p = 0.02) and LH (2.6 vs. 3.1 μlU ml^?1; p = 0.03) were significantly different between traffic policemen and roadmen. No differences were found in the mean values of testosterone between the two groups. Multiple linear regression models showed associations between (a) urinary cadmium, airborne cadmium, working life, job category and consumption of water from water supply (b) blood cadmium, airborne cadmium and job category (c) the values of FSH and age, working life, job category, urinary cadmium and blood cadmium (d) the values of LH and both the age and working life.ConclusionThe above results must be confirmed by further studies, but they indicate the influence of exposure to the cadmium present in urban air on the circulating FSH, even at low doses.     

Quantifying the sources of hazardous elements of suspended particulate matter aerosol collected in Yokohama,Japan

We analyzed metals (Mg, Al, Ca, V, Cr, Mn, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, Pb and Bi), water-soluble ions (Na⁺, NH₄⁺, K⁺, Ca²⁺, Cl^?, NO₃^? and SO₄^2?) and carbonaceous mass (EC and OC) in SPM aerosol samples using an ICP-MS, ion chromatograph and CHN corder, respectively. The SPM samples were collected from 1999 to 2005 at two locations (urban site A and industrial site B) of Yokohama, Japan with concentrations in mean and ranges of 34.2 and 19.7–50.3 μg m^?3 and 22.9 and 12.7–35.1 μg m^?3 for the respective location. Source apportionment of SPM aerosol was conducted appropriately for the first time to these locations employing PCA-APCS technique. Major sources of SPM at site A were a) crustal source, b) urban origin, c) undefined, and d) mineral rock. At site B, the sources were predicted as a) urban origin, b) undefined, c) crustal source, and d) secondarily formed aerosol. The tracers and nature of the source related to urban origin at both sites were similar but retaining different source strength. Secondarily formed aerosol was quite unique at site B. However, mineral rock was remarkable at site A.     

Characteristics of vertical profiles and sources of PM2.5, PM10 and carbonaceous species in Beijing

In August 2003 during the anticipated month of the 2008 Beijing Summer Olympic Games, we simultaneously collected PM₁₀ and PM_2.5 samples at 8, 100, 200 and 325 m heights up a meteorological tower and in an urban and a suburban site in Beijing. The samples were analysed for organic carbon (OC) and elemental carbon (EC) contents. Particulate matter (PM) and carbonaceous species pollution in the Beijing region were serious and widespread with 86% of PM_2.5 samples exceeding the daily National Ambient Air Quality Standard of the USA (65 μg m⁻³) and the overall daily average PM₁₀ concentrations of the three surface sites exceeding the Class II National Air Quality Standard of China (150 μg m⁻³). The maximum daily PM_2.5 and PM₁₀ concentrations reached 178.7 and 368.1 μg m⁻³, respectively, while those of OC and EC reached 22.2 and 9.1 μg m⁻³ in PM_2.5 and 30.0 and 13.0 μg m⁻³ in PM₁₀, respectively. PM, especially PM_2.5, OC and EC showed complex vertical distributions and distinct layered structures up the meteorological tower with elevated levels extending to the 100, 200 and 300 m heights. Meteorological evidence suggested that there exist fine atmospheric layers over urban Beijing. These layers were featured by strong temperature inversions close to the surface (<50 m) and more stable conditions aloft. They enhanced the accumulation of pollutants and probably caused the complex vertical distributions of PM and carbonaceous species over urban Beijing. The built-up of PM was accompanied by transport of industrial emissions from the southwest direction of the city. Emissions from road traffic and construction activities as well as secondary organic carbon (SOC) are important sources of PM. High OC/EC ratios (range of 1.8–5.1 for PM_2.5 and 2.0–4.3 for PM₁₀) were found, especially in the higher levels of the meteorological tower suggesting there were substantial productions of SOC in summer Beijing. SOC is estimated to account for at least 33.8% and 28.1% of OC in PM_2.5 and PM₁₀, respectively, with higher percentages at the higher levels of the tower.     

Measurement and analysis of atmospheric ammonia emissions from anaerobic lagoons

Ammonia-nitrogen flux (NH₃-N=(14/17)NH₃) was determined from six anaerobic swine waste storage and treatment lagoons (primary, secondary, and tertiary) using the dynamic chamber system. Measurements occurred during the fall of 1998 through the early spring of 1999, and each lagoon was examined for approximately one week. Analysis of flux variation was made with respect to lagoon surface water temperature (∼15 cm below the surface), lagoon water pH, total aqueous phase NH_x(=NH₃+NH₄⁺) concentration, and total Kjeldahl nitrogen (TKN). Average lagoon temperatures (across all six lagoons) ranged from approximately 10.3 to 23.3^°C. The pH ranged in value from 6.8 to 8.1. Aqueous NH_x concentration ranged from 37 to 909 mg N l⁻¹, and TKN varied from 87 to 950 mg N l⁻¹. Fluxes were the largest at the primary lagoon in Kenansville, NC (March 1999) with an average value of 120.3 μg N m⁻² min⁻¹, and smallest at the tertiary lagoon in Rocky Mount, NC (November 1998) at 40.7 μg N m⁻² min⁻¹. Emission rates were found to be correlated with both surface lagoon water temperature and aqueous NH_x concentration. The NH₃-N flux may be modeled as ln(NH₃-N flux)=1.0788+0.0406T_L+0.0015([NH_x]) (R²=0.74), where NH₃-N flux is the ammonia flux from the lagoon surface in μg N m⁻² min⁻¹, T_L is the lagoon surface water temperature in ^°C, and [NH_x] is the total ammonia-nitrogen concentration in mg N l⁻¹.     

Quantification of Saharan dust contribution to PM10 concentrations over Italy during 2003–2005

Italy is frequently affected by Saharan dust intrusions, which result in high PM₁₀ concentrations in the atmosphere and can cause the exceedances of the PM₁₀ daily limits (50 μg m^?3) set by the European Union (EU/2008/50). The estimate of African dust contribution to PM₁₀ concentrations is therefore a key issue in air quality assessment and policy formulation. This study presents a first identification of Saharan dust outbreaks as well as an estimate of the African dust contribution to PM₁₀ concentrations during the period 2003–2005 over Italy. The identification of dust events has been carried out by looking at different sources of information such as monitoring network observations, satellite images, ground measurements of aerosol optical properties, dust model simulations and air mass backward trajectory analysis. The contribution of Saharan dust to PM₁₀ monthly concentrations has been estimated at seven Italian locations. The results are both spatially (with station) and temporally (with month and year) variable, as a consequence of the variability of the meteorological conditions. However, excluding the contribution of severe dust events (21st February 2004, 25th–28th September 2003, 23rd–27th March 2005), the monthly contribution of dust varies approximately between 1 μg m^?3 and 10 μg m^?3 throughout year 2005 and between 1 μg m^?3 and 8 μg m^?3 throughout year 2003. In 2004 the dust concentration is lower than 2003 and 2005 (<5 μg m^?3 at all sites). The reduction in the number of daily exceedances of the limit value (50 μg m^?3) after subtraction of the dust contribution is also calculated at each station: it varies with station between 20% and 50% in 2005 and between 5% and 25% in 2003 and 2004.     

Atmospheric nitrogen fluxes at the Belgian coast: 2004–2006

Daily and seasonal variations in dry and wet atmospheric nitrogen fluxes have been studied during four campaigns between 2004 and 2006 at a coastal site of the Southern North Sea at De Haan (Belgium) located at coordinates of 51.1723° N and 3.0369° E. Concentrations of inorganic N-compounds were determined in the gaseous phase, size-segregated aerosol (coarse, medium, and fine), and rainwater samples. Dissolved organic nitrogen (DON) was quantified in rainwater. The daily variations in N-fluxes of compounds were evaluated with air-mass backward trajectories, classified into the main air-masses arriving at the sampling site (i.e., continental, North Sea, and Atlantic/UK/Channel).The three, non-episodic campaigns showed broadly consistent fluxes, but during the late summer campaign exceptionally high episodic N-deposition was observed. The average dry and wet fluxes for non-episodic campaigns amounted to 2.6 and 4.0 mg N m^?2 d^?1, respectively, whereas during the episodic late summer period these fluxes were as high as 5.2 and 6.2 mg N m^?2 d^?1, respectively.Non-episodic seasons/campaigns experienced average aerosol fluxes of 0.9–1.4 mg N m^?2 d^?1. Generally, the contribution of aerosol NH₄⁺ was more significant in the medium and fine particulate fractions than that of aerosol NO₃^?, whereas the latter contributed more in the coarse fraction, especially in continental air-masses. During the dry mid-summer campaign, the DON contributed considerably (～15%) to the total N-budget.Exceptionally high episodic aerosol-N inputs have been observed for the late summer campaign, with especially high deposition rates of 3.6 and 2.9 mg N m^?2 d^?1 for Atlantic/UK/Channel and North Sea-continental (mixed) air-masses, respectively. During this pollution episode, the flux of NH₄⁺ was dominating in each aerosol fraction/air-mass, except for coarse continental aerosols. High deposition of gaseous-N was also observed in this campaign with an average total N-flux of 2–2.5-times higher than in other campaigns.     

Air pollutants in rural homes in Guizhou,China – Concentrations,speciation, and size distribution

Several types of fuels, including coal, fuel wood, and biogas, are commonly used for cooking and heating in Chinese rural households, resulting in indoor air pollution and causing severe health impacts. In this paper, we report a study monitoring multiple pollutants including PM₁₀, PM_2.5, CO, CO₂, and volatile organic compounds (VOCs) from fuel combustion at households in Guizhou province of China. The results showed that most pollutants exhibited large variability for different type of fuels except for CO₂. Among these fuels, wood combustion caused the most serious indoor air pollution, with the highest concentrations of particulate matters (218～417 μg m^?3 for PM₁₀ and 201～304 μg m^?3 for PM_2.5), and higher concentrations of CO (10.8 ± 0.8 mg m^?3) and TVOC (about 466.7 ± 337.9 μg m^?3). Coal combustion also resulted in higher concentrations of particulate matters (220～250 μg m^?3 for PM₁₀ and 170～200 μg m^?3 for PM_2.5), but different levels for CO (respectively 14.5 ± 3.7 mg m^?3 for combustion in brick stove and 5.5 ± 0.7 mg m^?3 for combustion in metal stove) and TVOC (170 mg m^?3 for combustion in brick stove and 700 mg m^?3 for combustion in metal stove). Biogas was the cleanest fuel, which brought about the similar levels of various pollutants with the indoor case of non-combustion, and worth being promoted in more areas. Analysis of the chemical profiles of PM_2.5 indicated that OC and EC were dominant components for all fuels, with the proportions of 30～48%. A high fraction of SO₄^2? (31～34%) was detected for coal combustion. The cumulative percentages of these chemical species were within the range of 0.7～1.3, which was acceptable for the assessment of mass balance.     

Field performance of dichotomous sequential PM air samplers

For over one year, the Environmental Protection Commission of Hillsborough County (EPCHC) in Tampa, Florida, operated two dichotomous sequential particulate matter air samplers collocated with a manual Federal Reference Method (FRM) air sampler at a waterfront site on Tampa Bay. The FRM was alternately configured as a PM_2.5, then as a PM₁₀ sampler. For the dichotomous sampler measurements, daily 24-h integrated PM_2.5 and PM_10–2.5 ambient air samples were collected at a total flow rate of 16.7 l min⁻¹. A virtual impactor split the air into flow rates of 1.67 and 15.0 l min⁻¹ onto PM_10–2.5 and PM_2.5 47-mm diameter PTFE^® filters, respectively. Between the two dichotomous air samplers, the average concentration, relative bias and relative precision were 13.3 μg m⁻³, 0.02% and 5.2% for PM_2.5 concentrations (n=282), and 12.3 μg m⁻³, 3.9% and 7.7% for PM_10–2.5 concentrations (n=282). FRM measurements were alternate day 24-h integrated PM_2.5 or PM₁₀ ambient air samples collected onto 47-mm diameter PTFE^® filters at a flow rate of 16.7 l min⁻¹. Between a dichotomous and a PM_2.5 FRM air sampler, the average concentration, relative bias and relative precision were 12.4 μg m⁻³, −5.6% and 8.2% (n=43); and between a dichotomous and a PM₁₀ FRM air sampler, the average concentration, relative bias and relative precision were 25.7 μg m⁻³, −4.0% and 5.8% (n=102). The PM_2.5 concentration measurement standard errors were 0.95, 0.79 and 1.02 μg m⁻³; for PM₁₀ the standard errors were 1.06, 1.59, and 1.70 μg m⁻³ for two dichotomous and one FRM samplers, respectively, which indicate the dichotomous samplers have superior technical merit. These results reveal the potential for the dichotomous sequential air sampler to replace the combination of the PM_2.5 and PM₁₀ FRM air samplers, offering the capability of making simultaneous, self-consistent determinations of these particulate matter fractions in a routine ambient monitoring mode.     

Absence of trends in relative risk estimates for the association between Black Smoke and daily mortality over a 34 years period in The Netherlands

A major issue in air pollution epidemiology is whether the associations that are found in the statistical analyses on the health effects of air pollution reflect real causal associations of single components or mixtures thereof, or just reflect statistical associations that are mainly the result of the high correlation between the separate components, one of them being the true causal factor.In a previous analysis on the relationship between daily SO₂ levels and daily mortality in The Netherlands [Buringh, E., Fischer, P., Hoek, G., 2000. Is SO₂ a causative factor for the PM-associated mortality risks in The Netherlands? Inhal. Toxicol. 12 (Suppl. 1), 55–60.], it was shown that the statistical significant association between daily variation in SO₂ and daily mortality did not reflect a causal relation. Black Smoke levels in The Netherlands have decreased 4-fold during the 34 years in the period 1972–2006 (annual average from 27 μg m^?3 to 6 μg m^?3). This large decrease in concentrations enabled us to use the same approach for this component as was done earlier for SO₂ to assess whether a decreasing trend in Black Smoke levels in The Netherlands is associated with an increasing trend in mortality relative risks or not.We used daily averaged Black Smoke (BS) data from 1972 to 2006. In the first two decades (1970–1990) only sparse data were available. Based on the availability of the data, we selected data from 1972 to 1974 and from 1982 to 1984 because during these two periods continuous daily measurement series were available. For the later years (1989–2006) data covering the whole of The Netherlands were available, giving a total of 24 years of daily data. Data on daily total mortality counts (excluding external causes), cardiovascular mortality and respiratory mortality for the whole population of The Netherlands were analyzed with regard to daily Black Smoke levels using generalized additive Poisson regression models (GAM). Period specific relative risk estimates were compared and differences in estimates between periods were evaluated.We found no consistent increase in relative risks for daily total and cause-specific mortality over time, despite the decreasing trend in the Black Smoke levels in The Netherlands. Average relative risks for total mortality varied over the different periods from 0.997 per 10 μg m^?3 daily Black Smoke to 1.010 per 10 μg m^?3. Average relative risks for cardiovascular mortality varied from 0.988 per 10 μg m^?3 to 1.010 per 10 μg m^?3 and for respiratory mortality from 1.000 to 1.010 per 10 μg m^?3. For weekly averaged concentrations the average relative risks for total mortality varied over the different periods from 1.004 per 10 μg m^?3 Black Smoke to 1.018 per 10 μg m^?3. Average relative risks for cardiovascular mortality varied from 1.003 per 10 μg m^?3 to 1.016 per 10 μg m^?3 and for respiratory mortality from 1.000 to 1.050 per 10 μg m^?3.The result of our analyses suggests that Black Smoke cannot be excluded as a potential causal agent because relative risks over time show no increasing trend despite the decreasing trend in Black Smoke concentrations.