Elevated atmospheric deposition and dynamics of mercury in a remote upland forest of southwestern China

Mt. Gongga area in southwest China was impacted by Hg emissions from industrial activities and coal combustion, and annual means of atmospheric TGM and PHg concentrations at a regional background station were 3.98 ng m⁻³ and 30.7 pg m⁻³, respectively. This work presents a mass balance study of Hg in an upland forest in this area. Atmospheric deposition was highly elevated in the study area, with the annual mean THg deposition flux of 92.5 μg m⁻² yr⁻¹. Total deposition was dominated by dry deposition (71.8%), and wet deposition accounted for the remaining 28.2%. Forest was a large pool of atmospheric Hg, and nearly 76% of the atmospheric input was stored in forest soil. Volatilization and stream outflow were identified as the two major pathways for THg losses from the forest, which yielded mean output fluxes of 14.0 and 8.6 μg m⁻² yr⁻¹, respectively.     

Historical deposition of mercury and selected trace elements to high-elevation National Parks in the Western U.S. inferred from lake-sediment cores

Atmospheric deposition of Hg and selected trace elements was reconstructed over the past 150 years using sediment cores collected from nine remote, high-elevation lakes in Rocky Mountain National Park in Colorado and Glacier National Park in Montana. Cores were age dated by ²¹⁰Pb, and sedimentation rates were determined using the constant rate of supply model. Hg concentrations in most of the cores began to increase around 1900, reaching a peak sometime after 1980. Other trace elements, particularly Pb and Cd, showed similar post-industrial increases in lake sediments, confirming that anthropogenic contaminants are reaching remote areas of the Rocky Mountains via atmospheric transport and deposition. Preindustrial (pre-1875) Hg fluxes in the sediment ranged from 5.7 to 42 μg m^?2 yr^?1 and modern (post-1985) fluxes ranged from 17.7 to 141 μg m^?2 yr^?1. The average ratio of modern to preindustrial fluxes was 3.2, which is similar to remote lakes elsewhere in North America. Estimates of net atmospheric deposition based on the cores were 3.1 μg m^?2 yr^?1 for preindustrial and 11.7 μg m^?2 yr^?1 for modern times. Current-day measurements of wet deposition range from 5.0 to 8.6 μg m^?2 yr^?1, which are lower than the modern sediment-based estimate of 11.7 μg m^?2 yr^?1, perhaps owing to inputs of dry-deposited Hg to the lakes.     

Dry and wet deposition of water-insoluble dust and water-soluble chemical species during spring 2007 in Tsukuba,Japan

Dry and wet depositions were sampled daily in Tsukuba, Japan, in spring 2007. Temporal variations in the dry and wet deposition fluxes of dust and water-soluble chemical species were controlled largely by air mass origin, the water vapor mixing ratio, and Asian dust events. The contribution of local sources to dry deposition of dust was large when the wind speed was high. Dry deposition fluxes of water-soluble chemical species were larger in humid air masses than in dry air masses. Wet deposition fluxes of dust and water-soluble chemical species indicated that air masses that passed over dust source regions and industrial regions became mixed with the maritime air masses over the coastal site of the Asian continent and western part of the Japanese islands. The total deposition of dust was 4220 mg m^?2 month^?1, and that of water-soluble chemical species ranged from 10 to 636 mg m^?2 month^?1. Wet deposition fluxes of the total deposition flux of dust accounted for 72% and those of water-soluble chemical species was for 72–96%. In particular, the largest wet deposition occurred during a single Asian dust event on 3 April. This event accounted for 23% (950 mg m^?2 month^?1) of the monthly dust deposition flux and for 2–28% (0.43–51 mg m^?2 month^?1) of the monthly deposition flux of water-soluble chemical species. This result implies that the wet deposition flux associated with even one sporadic Asian dust event can have extensive impacts on both terrestrial and oceanic ecosystems in East Asia.     

Concentrations,seasonal variations,and transport of carbonaceous aerosols at a remote Mountainous region in western China

Carbonaceous aerosol concentrations were determined for total suspended particle samples collected from Muztagh Ata Mountain in western China from December 2003 to February 2006. Elemental carbon (EC) varied from 0.004 to 0.174 μg m^?3 (average = 0.055 μg m^?3) while organic carbon (OC) ranged from 0.12 to 2.17 μg m^?3 and carbonate carbon (CC) from below detection to 3.57 μg m^?3. Overall, EC was the least abundant fraction of carbonaceous species, and the EC concentrations approached those in some remote polar areas, possibly representing a regional background. Low EC and OC concentrations occurred in winter and spring while high CC in spring and summer was presumably due to dust from the Taklimakan desert, China. OC/EC ratios averaged 10.0, and strong correlations between OC and EC in spring–winter suggest their cycles are coupled, but lower correlations in summer–autumn suggest influences from biogenic OC emissions and secondary OC formation. Trajectory analyses indicate that air transported from outside of China brings ～0.05 μg m^?3 EC, ～0.42 μg m^?3 OC, and ～0.10 μg m^?3 CC to the site, with higher levels coming from inside China. The observed EC was within the range of loadings estimated from a glacial ice core, and implications of EC-induced warming for regional climate and glacial ice dynamics are discussed.     

Polycyclic aromatic hydrocarbon (PAH) deposition to and exchange at the air-water interface of Luhu, an urban lake in Guangzhou, China

Urban lakes are vulnerable to the accumulation of semivolatile organic compounds, such as PAHs from wet and dry atmospheric deposition. Little was reported on the seasonal patterns of atmospheric deposition of PAHs under Asian monsoon climate. Bulk (dry + wet) particle deposition, air-water diffusion exchange, and vapour wet deposition of PAHs in a small urban lake in Guangzhou were estimated based on a year-round monitoring. The total PAH particle deposition fluxes observed were 0.44-3.46 μg m⁻² day⁻¹. The mean air-water diffusive exchange flux was 20.7 μg m⁻² day⁻¹. The vapour deposition fluxes of PAHs ranged 0.15-8.26 μg m⁻² day⁻¹. Remarkable seasonal variations of particulate PAH deposition, air-water exchange fluxes and vapour wet deposition were influenced by seasonal changes in meteorological parameters. The deposition fluxes were predominantly controlled by the precipitation intensity in wet season whereas by atmospheric concentration in dry season.     

Concentrations and sources of carbonaceous aerosol in the atmosphere of Summit,Greenland

High-volume PM_2.5 samples were collected at Summit, Greenland for approximately six months from late May through December of 2006. Filters were composited and analyzed for source tracer compounds. The individual organic compounds measured at Summit are orders of magnitude smaller than concentrations measured at other sites, including locations representative of remote oceanic, and remote and urban continental aerosol. The measured tracers were used to quantify the contribution of biomass burning (0.6–0.9 ng C m^?3), vegetative detritus (0.3–0.9 ng C m^?3), and fossil fuel combustion (0.1–0.8 ng C m^?3) sources, 4% of OC total, to atmospheric organic carbon concentrations at the remote location of Summit, Greenland. The unapportioned organic carbon (96%) during the early summer period correlates well with the fraction of water soluble organic carbon, indicating secondary organic aerosol as a large source of organic carbon, supported by the active photochemistry occurring at Summit. To the author's knowledge, this paper represents the first source apportionment results for the polar free troposphere.     

Wet deposition of phosphorus in Florida

Wet deposition of phosphorus was measured at 10 sites across Florida originally established as part of the Florida Atmospheric Mercury Study conducted between 1992 and 1996. Monthly integrated samples were collected and analyzed using a total analytical protocol that incorporated “clean lab” conditions for sample equipment preparation and Aerochem Metrics collectors modified for suitability to use for ultra-trace elements. Samples also were collected aboard 15 m towers to minimize any influence on measured deposition by insects, etc., and locally originating particles that do not contribute to true net deposition. Extensive replication of samples in the field was conducted (ca. 83%). The average absolute difference between replicates was 16.2%, with a median absolute difference of 9.5%. Replicate precision was poorest for concentrations above 0.080 mg P l⁻¹, suggesting that concentrations above this level are contaminated.The wet deposition concentrations and fluxes of phosphorus measured in this study are appreciably lower than those reported by previous investigators for wet deposition in Florida, and lie at the lower end of measurements reported in the recent literature. For example, the volume weighted mean concentration and flux for wet deposition across all our study sites averaged 0.005 mg P l⁻¹ and 7.5 mg P m⁻² yr⁻¹, respectively, which is approximately 50% and 32% lower than that reported by Hendry et al. (1981 in Atmospheric Pollutants in Natural Waters. Ann Arbor Science, Ann Arbor. MI, pp. 199–215). Our lower measurements likely reflect three factors: (1) the ultra-trace element sampling and analytical protocols; (2) improved collector design to eliminate sampling artifacts (e.g., splash-off contamination and transfer of contaminants from the dry bucket); and (3) placement of collectors off the ground surface. Lower VWM concentrations were observed near the Florida coast; otherwise, strong spatial patterns across the state were absent. Seasonal variations in VWM also were not pronounced, although deposition fluxes were highest during the summer wet season in response to the strong seasonal distribution of rainfall.     

A four-year size-segregated characterization study of particles PM10, PM2.5 and PM1 depending on air mass origin at Melpitz

PM₁₀ measurements were started in November 1992 at Melpitz site. The mean PM₁₀ concentration in 1993 was 38 μg m^?3 in the summer season (May until October) and about 44 μg m^?3 in the winter season (November until April). The mean PM₁₀ level decreased until 1999 and varies now in ranges from 20–34 μg m^?3 to 17–24 μg m^?3 (minimum and maximum mean values for 1999–2008) in winter and summer seasons, respectively. High volume filter samples of particles PM₁₀, PM_2.5 and PM₁ were characterized for mass, water-soluble ions, organic and elemental carbon from 2004 until 2008. The percentage of PM_2.5 in PM₁₀ varies between summer (71.6%) and winter seasons (81.9%). Mean concentrations of PM₁₀, PM_2.5 and PM₁ in Melpitz were 20, 15, and 13 μg m^?3 in 2004, 22, 18, and 13 μg m^?3 in 2005, 24, 19, and 12 μg m^?3 in 2006 and 22, 17, and 12 μg m^?3 in 2007, respectively. In the four winters the rural background concentration PM₁₀ at Melpitz exceeded the daily 50 μg m^?3 limit for Europe on 8, 8, 7 and 6 days, respectively.Findings for a simple two-sector-classification of the samples (May 2004 until April 2008) using 96-h backward trajectories for the identification of source regions are: Air masses were transported most of time (60%) from the western sector and secondly (17%) from the eastern sector. The lowest daily mean mass concentration PM₁₀ were found during western inflow in summer (17 μg m^?3) containing low amounts of sulphate (2.4 μg m^?3), nitrate (1.7 μg m^?3), ammonium (1.1 μg m^?3) and TC (3.7 μg m^?3). In opposite the highest mean mass concentration PM₁₀ was found during eastern inflow in winter (35 μg m^?3) with high amounts of sulphate (6.1 μg m^?3), nitrate (5.4 μg m^?3), ammonium (3.8 μg m^?3) and TC (9.4 μg m^?3). An estimation of secondary formed OC (SOA) shows 0.8–0.9 μg m^?3 for air masses from West and 2.1–2.2 μg m^?3 from East. The seasonal difference can be neglected.The half-hourly measurements of the particle mass concentration PM₁₀ evaluated as mean daily courses using a TEOM^® show low values (14–21 μg m^?3) in summer and winter for air masses transported from West and the highest concentrations (31–38 μg m^?3) in winter for air masses from East.The results demonstrate the influence of meteorological parameters on long-range transport, secondary particle mass formation and re-emission which modify mass concentration and composition of PM₁₀, PM_2.5 and PM₁. Melpitz site is located in the East of Germany faraway from strong local anthropogenic emissions (rural background). Therefore, this site is suitable for investigation of the influence of long-range transport of air pollution in continental air masses from the East with source regions inside and outside of the European Union.     

Long-term effects of clear-cutting and selective cutting on soil methane fluxes in a temperate spruce forest in southern Germany

Based on multi-year measurements of CH₄ exchange in sub-daily resolution we show that clear-cutting of a forest in Southern Germany increased soil temperature and moisture and decreased CH₄ uptake. CH₄ uptake in the first year after clear-cutting (−4.5 ± 0.2 μg C m⁻² h⁻¹) was three times lower than during the pre-harvest period (−14.2 ± 1.3 μg C m⁻² h⁻¹). In contrast, selective cutting did not significantly reduce CH₄ uptake. Annual mean uptake rates were −1.18 kg C ha⁻¹ yr⁻¹ (spruce control), −1.16 kg C ha⁻¹ yr⁻¹ (selective cut site) and −0.44 kg C ha⁻¹ yr⁻¹ (clear-cut site), respectively. Substantial seasonal and inter-annual variations in CH₄ fluxes were observed as a result of significant variability of weather conditions, demonstrating the need for long-term measurements. Our findings imply that a stepwise selective cutting instead of clear-cutting may contribute to mitigating global warming by maintaining a high CH₄ uptake capacity of the soil.     

Growing season methane budget of an Inner Mongolian steppe

We present a methane (CH₄) budget for the area of the Baiyinxile Livestock Farm, which comprises approximately 1/3 of the Xilin river catchment in central Inner Mongolia, P.R. China. The budget calculations comprise the contributions of natural sources and sinks as well as sources related to the main land-use in this region (non-nomadic pastoralism) during the growing season (May–September). We identified as important CH₄ sources floodplains (mean 1.55 ± 0.97 mg CH₄–C m^?2 h^?1) and domestic ruminants, which are mainly sheep in this area. Within the floodplain significant differences between investigated positions were detected, whereby only positions close-by the river or bayous emitted large amounts of CH₄ (mean up to 6.21 ± 1.83 mg CH₄–C m^?2 h^?1). Further CH₄ sources were sheepfolds (0.08–0.91 mg CH₄–C m^?2 h^?1) and pasture faeces (1.34 ± 0.22 mg CH₄–C g^?1 faeces dry weight), but they did not play a significant role for the CH₄ budget. In contrast, dung heaps were not a net source of CH₄ (0.0 ± 0.2 for an old and 0.0 ± 0.3 μg CH₄–C kg^?1 h^?1 for a new dung heap). Trace gas measurements along two landscape transects (volcano, hill slope) revealed expectedly a mean CH₄ uptake (volcano: 76.5 ± 4.3; hill: 28.3 ± 5.3 μg CH₄–C m^?2 h^?1), which is typical for the aerobic soils in this and other steppe ecosystems. The observed fluxes were rarely influenced by topography.The CH₄ emissions from the floodplain and the sheep were not compensated by the CH₄ oxidation of aerobic steppe soils and thus, this managed semi-arid grassland did not serve as a terrestrial sink, but as a source for this globally important greenhouse gas. The source strength amounted to 1.5–3.6 kg CH₄–C ha^?1 during the growing season, corresponding to 3.5–8.7 kg C ha^?1 yr^?1.     

Near roadway concentrations of organic source markers

Concentrations of elemental carbon (EC), organic carbon (OC), and 33 organic source markers (12 alkanes, 18 polycyclic aromatic hydrocarbons and ketones, and 3 hopanes) are reported near a highway in Raleigh, NC with an annual average daily traffic count of approximately 125,000 vehicles. Daily samples (24-h) were collected at two locations, one approximately 10 m and the other 275 m perpendicular from the road. Concentrations of OC were similar between near (mean = 7.6 μg m^?3) and far (8.0 μg m^?3) locations, but concentrations of most organic species at the near site were between 1.5 and 2 times higher than those at the far site.     

Mercury deposition/accumulation rates in the vicinity of a lead smelter as recorded by a peat deposit

Mercury (Hg) concentration profiles and historical accumulation rates were determined in three ²¹⁰Pb-dated cores from a peat deposit in the vicinity of a lead (Pb) smelter at Příbram, Czech Republic. The Hg concentrations in peat samples ranged from 66 to 701 μg kg⁻¹. Cumulative Hg inventories from each core (for the past 150 yr) varied by a factor of 1.4 (13.6–18.5 mg Hg m⁻²), indicating variations of net Hg accumulation rate within the peat deposit. Historical changes in vegetation cover (leading to variable interception by trees) are probably responsible for this variation in space and time. The uncorrected Hg accumulation rates peaked between the 1960s and 1980s (up to 226 μg m⁻² yr⁻¹). Recent findings show that Hg records from peat tend to overestimate historical levels of Hg deposition. Therefore we used the mass loss compensation factor (MLCF) to normalize Hg accumulation rates. These corrected Hg accumulation rates were significantly lower (maximum 129 μg m⁻² yr⁻¹) and better corresponded to changes in historical smelter emissions, which were highest in the 1960s. The agreement between the corrected Hg accumulation rates in the uppermost peat sections (2–38 μg m⁻² yr⁻¹) and biomonitoring of atmospheric deposition by mosses in several recent years (4.7–34.4 μg m⁻² yr⁻¹) shows the usefulness of MLCF application on Hg accumulation in peat archives. However, the MLCF correction was unsuitable for Pb. The recent Pb deposition rates obtained by an independent biomonitoring study using mosses (0.5–127 mg m⁻² yr⁻¹) were better correlated with net Pb accumulation rates recorded in peat (7–145 mg m⁻² yr⁻¹) than with corrected rates obtained by the MLCF approach (1–28 mg m⁻² yr⁻¹).     

Atmospheric particle characterization, distribution, and deposition in Xi'an, Shaanxi Province, Central China

Physical characterization and chemical analysis of settled dusts collected in Xi’an from November 2007 to December 2008 show that (1) dust deposition rates ranged from 14.6 to 350.4 g m⁻² yr⁻¹. The average deposition rate (76.7 g m⁻² yr⁻¹) ranks the 11th out of 56 dust deposition rates observed throughout the world. The coal-burning power was the major particle source; (2) on average (except site 4), ∼10% of the settled dusts having size <2.6, ∼30% having size <10.5, and >70% having size <30 μm; (3) the concentrations for 20 out of 27 elements analyzed were upto 18 times higher than their soil background values in China. With such high deposition rates of dusts that contain elevated levels of toxic elements, actions should be taken to reduce emission and studies are needed to assess the potential impacts of settled particles on surface ecosystem, water resource, and human health in the area.     

Mercury emission trend influenced by stringent air pollutants regulation for coal-fired power plants in Korea

Regulatory control of mercury emission from anthropogenic sources has become a global concern in the recent past. Coal-fired power plants are one of the largest sources of anthropogenic mercury emission into the atmosphere. This paper summarizes the current reducing trend of mercury emission as co-beneficial effect by more stringent regulation changes to control primary air pollutants with introducing test results from the commercial coal-fired facilities and suggesting a guideline for future regulatory development in Korea. On average, mercury emission concentrations ranged 16.3–2.7 μg Sm^?3, 2.4–1.1 μg Sm^?3, 3.1–0.7 μg Sm^?3 from anthracite coal-fired power plants equipped with electrostatic precipitator (ESP), bituminous coal-fired power plants with ESP + flue gas desulphurization (FGD) and bituminous coal-fired power plants with selective catalytic reactor (SCR) + cold side (CS) ? ESP + wet FGD, respectively. Among the existing air pollution control devices, the best configuration for mercury removal in coal-fired power plants was SCR + CS ? ESP + wet FGD, which were installed due to the stringent regulation changes to control primary air pollutants emission such as SO₂, NOx and dust. It was estimated that uncontrolled and controlled mercury emission from coal-fired power plants as 10.3 ton yr^?1 and 3.2 ton yr^?1 respectively. After the installation of ESP, FGD and SCR system, following the enforcement of the stringent regulation, 7.1 ton yr^?1 of mercury emission has been reduced (nearly 69%) from coal-fired power plants as a co-benefit control. Based on the overall study, a sample guideline including emission limits were suggested which will be applied to develop a countermeasure for controlling mercury emission from coal-fired power plants.     

Canopy leaching of nutrients and metals in a mountain spruce forest

Precipitation and throughfall fluxes of major ions, nutrients (C, N, P), and metals (Al, Fe, Mn), and the chemical composition of litter fall and living plant tissue in Norway spruce stands (the Bohemian Forest; Czech Republic), were used to evaluate how microbial processes and decay of plant tissue in canopies influence canopy leaching (CL) of elements. Proton exchange for Mg²⁺, Ca²⁺, and K⁺ in decaying biomass and co-transport of Ca²⁺ and K⁺ out of plant cells with organic acid anions were the most likely processes contributing to CL of base cations. The CL of total P and N (and also NO₃^?) was minor. Important proportions of the N and P mineral forms were transformed to organic forms by microbial processes (primary and bacterial production), with the respective CL of ?13.9 and 16.4 mmol m^?2 yr^?1 for NH₄⁺ and organic N, and ?0.33 and 0.22 mmol m^?2 yr^?1 for dissolved reactive P (DRP) and organic P. Most of particulate P and N in throughfall (～90%) originated from microbial DRP and NH₄⁺ transformations, but particulate C mostly came from the fragmentation of plant tissue (58%). Among metals, CL was not observed for Al, was small for Fe (0.3 mmol m^?2 yr^?1), and greatest for Mn (0.9 mmol m^?2 yr^?1) due to leaching from decaying tissue by acidic precipitation.     

Wet deposition mercury fluxes in the Canadian sub-Arctic and southern Alberta,measured using an automated precipitation collector adapted to cold regions

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

Atmospheric deposition of organochlorine contaminants to Galveston Bay,Texas

Atmospheric monitoring of PCBs and chlorinated pesticides (e.g., HCHs, chlordanes, and DDTs) in Galveston Bay was conducted at Seabrook, Texas. Air and wet deposition samples were collected from 2 February 1995 and continued through 6 August 1996. Vapor total PCB (tPCB) concentrations in air ranged from 0.21 to 4.78 ng m⁻³ with a dominance of tri-chlorinated PCBs. Dissolved tPCBs in rain ranged from 0.08 to 3.34 ng l⁻¹, with tetra-chlorinated PCBs predominating. The predominant isomers found in air and rain were α- and γ-HCH, α- and γ-chlordanes, 4,4′-DDT, and dieldrin. The concentrations of PCBs and pesticides in the air and rain revealed no clear seasonal trend. Elevated levels of PCBs in the air occurred when temperatures were high and wind came from urban and industrialized areas (S, SW, NW, and W of the site). Concentrations of HCHs were elevated in April, May, and October, perhaps due to local and/or regional applications of γ-HCH (lindane). Other pesticides showed no notable temporal variation. When winds originated from the Gulf of Mexico (southeasterly), lower concentrations of organochlorines were detected in the air. The direct deposition rate (wet+dry) of PCBs to Galveston Bay (6.40 μg m⁻² yr⁻¹) was significantly higher than that of pesticides by a factor of 5–10. The net flux from gas exchange estimated for PCBs was from Galveston Bay water to the atmosphere (78 μg m⁻² yr⁻¹). Gas exchange of PCBs from bay water to the atmosphere was the dominant flux.     

Atmospheric phosphorus deposition at a montane site: Size distribution,effects of wildfire,and ecological implications

The dry deposition of atmospheric particulate matter can be a significant source of phosphorus (P) to oligotrophic aquatic ecosystems, including high-elevation lakes. In this study, measurements of the mass concentration and size distribution of aerosol particles and associated particulate P are reported for the southern Sierra Nevada, California, for the period July–October, 2008. Coarse and fine particle samples were collected with Stacked Filter Units and analyzed for Total P (TP) and inorganic P (IP) using a digestion-extraction procedure, with organic P (OP) calculated by difference. Particle size-resolved mass and TP distributions were determined concurrently using a MOUDI cascade impactor. Aerosol mass concentrations were significantly elevated at the study site, primarily due to transport from offsite and emissions from local and regional wildfires. Atmospheric TP concentrations ranged from 11 to 75 ng m^?3 (mean = 37 ± 16 ng m^?3), and were typically dominated by IP. Phosphorus was concentrated in the coarse (>1 μm diameter) particle fraction and was particularly enriched in the 1.0–3.2 μm size range, which accounted for 30–60% of the atmospheric TP load. Wildfire emissions varied widely in P content, and may be related to fire intensity. The estimated dry depositional flux of TP for each daily sampling period ranged between 7 and 118 μg m^?2 d^?1, with a mean value of 40 ± 27 μg m^?2 d^?1. Relative rates of dry deposition of N and P in the Sierra Nevada are consistent with increasing incidence of N limitation of phytoplankton growth and previously observed long-term eutrophication of lakes.     

Characterization of atmospheric aerosols for organic tarry matter and combustible matter during crop residue burning and non-crop residue burning months in Northwestern region of India

Aerosol (total suspended particulate) samples collected at three diverse locations (urban-commercial, semi-urban and rural-agricultural) in Patiala, India were analyzed for loss on ignition (LOI) and organic tarry matter (OTM) content in ambient air during crop residue burning (CRB) episodes and non-crop residue burning (NCRB) months in 2006–2007. Results showed high levels of LOI and OTM during wheat and rice crop residue-burning periods at all the sites. Higher levels were obtained during rice crop residue-burning period as compared to the wheat residue-burning period. At semi-urban site, LOI varied between 53 ± 36 μg m^?3 and 257 ± 14 μg m^?3 constituting 38–78% (w/w) part of the aerosols whereas levels of OTM varied between 0.98 ± 0.11 μg m^?3 and 7.93 ± 2.76 μg m^?3 comprising 0.42–3.28% (w/w) fraction. At rural-agricultural area site, levels of LOI varied between 86 ± 40 μg m^?3 and 293 ± 70 μg m^?3 comprising 27–84% (w/w), whereas OTM levels varied between 1.31 ± 0.64 μg m^?3 and 10.09 ± 6.56 μg m^?3 constituting 0.83–2.42% (w/w) fraction of the aerosols. At urban-cum-commercial site, levels of LOI and OTM varied between 48 ± 23 μg m^?3 and 281 ± 152 μg m^?3 and 2.53 ± 1.23 μg m^?3 and 17.40 ± 8.50 μg m^?3, constituting 24–62% (w/w) part of the aerosols, respectively. Results also indicated that OTM and LOI were integral parts of aerosols and their concentrations were influenced by the crop residue burning practices with incorporated effect of vehicular activities in Patiala.     

Atmospheric deposition of phthalate esters in a subtropical city

In Chinese cities, air pollution has become a serious and aggravating environmental problem undermining the sustainability of urban ecosystems and the quality of urban life. Bulk atmospheric deposition samples were collected two-weekly, from February 2007 to January 2008, at three representative areas, one suburban and two urbanized, in the subtropical city, Guangzhou, China, to assess the deposition fluxes and seasonal variations of phthalate esters (PAEs). Sixteen PAE congeners in bulk deposition samples were measured and the depositional fluxes of ∑₁₆PAEs ranged from 3.41 to 190 μg m^?2 day^?1, and were highly affected by local anthropogenic activities. The significant relationship between PAEs and particulate depositional fluxes (correlation coefficient R² = 0.72, P < 0.001) showed PAEs are associated primarily with particles. Temporal flux variations of PAEs were influenced by seasonal changes in meteorological parameters, and the deposition fluxes of PAEs were obviously higher in wet season than in dry season. Diisobutyl phthalate (DiBP), Di-n-butyl phthalate (DnBP), and Di(2-ethylhexyl) phthalate (DEHP) dominated the PAE pattern in bulk depositions, which is consistent with a high consumption of the plasticizer market in China. PAE profiles in bulk deposition showed similarities exhibited in both time and space, and a weak increase of high molecular weight PAE (HMW PAE) contribution in the wet season compared to those in the dry season. Average atmospheric deposition fluxes of PAEs in the present study were significantly higher than those from other studies, reflecting strong anthropogenic inputs as a consequence of rapid industrial and urban development in the region.