scholarly journals Atmospheric wet and dry deposition of trace elements at ten sites in Northern China

2014 ◽  
Vol 14 (14) ◽  
pp. 20647-20676 ◽  
Author(s):  
Y. P. Pan ◽  
Y. S. Wang
Keyword(s):  
Trace Elements ◽  
Atmospheric Deposition ◽  
Dry Deposition ◽  
Urban Areas ◽  
Wet Deposition ◽  
Northern China ◽  
Temporal Variations ◽  
Deposition Flux ◽  
Forest Site ◽  
Wet And Dry Deposition

Abstract. Atmospheric deposition is considered to be a major process that removes pollutants from the atmosphere and an important source of nutrients and contaminants for ecosystems. Trace elements (TEs), especially toxic metals deposited on plants and into soil and water, can cause substantial damage to the environment and human health due to their transfer and accumulation in food chains. Despite public concerns, quantitative knowledge of metal deposition from the atmosphere to ecosystems remains scarce. To advance our understanding of the spatio-temporal variations in the magnitudes, pathways, compositions and impacts of atmospherically deposited TEs, precipitation (rain and snow) and dry-deposited particles were collected simultaneously at ten sites in Northern China from December 2007 to November 2010. The measurements showed that the wet and dry depositions of TEs in the target areas were orders of magnitude higher than previous observations within and outside China, generating great concern over the potential risks. The spatial distribution of the total (wet plus dry) deposition flux was consistent with that of the dry deposition, with a significant decrease from industrial and urban areas to suburban, agricultural and rural sites. In contrast, the wet deposition exhibited less spatial variation. The seasonal variation of wet deposition was also different from that of dry deposition, although they were both governed by the precipitation and emission patterns. For the majority of TEs that exist as coarse particles, dry deposition dominated the total flux at each site. This was not the case for K, Ni, As, Pb, Zn, Cd, Se, Ag and Tl, for which the relative importance between wet and dry deposition fluxes varied by site. Whether wet deposition is the major atmospheric cleansing mechanism for the TEs depends on the size distribution and solubility of the particles. We found that atmospheric inputs of Cu, Pb, Zn, Cd, As and Se were of the same magnitude as their increases in the topsoil of agricultural systems. In addition, the total deposition flux of Pb observed at a forest site in this study was twice that of the critical load (7.0 mg m−2 yr−1) calculated for temperate forest ecosystems in Europe. These findings provide baseline data needed for future targeting policies to protect various ecosystems from long-term heavy metal input via atmospheric deposition.

scholarly journals Atmospheric wet and dry deposition of trace elements at 10 sites in Northern China

2015 ◽  
Vol 15 (2) ◽  
pp. 951-972 ◽  
Author(s):  
Y. P. Pan ◽  
Y. S. Wang
Keyword(s):  
Trace Elements ◽  
Atmospheric Deposition ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Northern China ◽  
Deposition Flux ◽  
Forest Site ◽  
Wet And Dry Deposition ◽  
Zinc Cadmium ◽  
Lead Zinc

Abstract. Atmospheric deposition is considered to be a major process that removes pollutants from the atmosphere and an important source of nutrients and contaminants for ecosystems. Trace elements (TEs), especially toxic metals deposited on plants and into soil or water, can cause substantial damage to the environment and human health due to their transfer and accumulation in food chains. Despite public concerns, quantitative knowledge of metal deposition from the atmosphere to ecosystems remains scarce. To advance our understanding of the spatiotemporal variations in the magnitudes, pathways, compositions and impacts of atmospherically deposited TEs, precipitation (rain and snow) and dry-deposited particles were collected simultaneously at 10 sites in Northern China from December 2007 to November 2010. The measurements showed that the wet and dry depositions of TEs in the target areas were orders of magnitude higher than previous observations within and outside China, generating great concern over the potential risks. The spatial distribution of the total (wet plus dry) deposition flux was consistent with that of the dry deposition, with a significant decrease from industrial and urban areas to suburban, agricultural and rural sites, while the wet deposition exhibited less spatial variation. In addition, the seasonal variation of wet deposition was also different from that of dry deposition, although they were both governed by the precipitation and emission patterns. For the majority of TEs that exist as coarse particles, dry deposition dominated the total flux at each site. This was not the case for potassium, nickel, arsenic, lead, zinc, cadmium, selenium, silver and thallium, for which the relative importance between wet and dry deposition fluxes varied by site. Whether wet deposition is the major atmospheric cleansing mechanism for the TEs depends on the size distribution of the particles. We found that atmospheric inputs of copper, lead, zinc, cadmium, arsenic and selenium were of the same magnitude as their increases in the topsoil of agricultural systems. At a background forest site in Northern China, the total deposition flux of lead observed in this study (14.1 mg m−2 yr−1) was twice that of the critical load calculated for temperate forest ecosystems in Europe. These findings provide baseline data needed for future targeting policies to protect various ecosystems from long-term heavy metal input via atmospheric deposition.

scholarly journals Atmospheric total gaseous mercury (TGM) concentrations and wet and dry deposition of mercury at a high-altitude mountain peak in south China

2009 ◽  
Vol 9 (6) ◽  
pp. 23465-23504 ◽  
Author(s):  
X. W. Fu ◽  
X. Feng ◽  
Z. Q. Dong ◽  
R. S. Yin ◽  
J. X. Wang ◽  
...  
Keyword(s):  
South China ◽  
Dry Deposition ◽  
Urban Areas ◽  
Wet Deposition ◽  
Ambient Air ◽  
Total Gaseous Mercury ◽  
Deposition Fluxes ◽  
Wet And Dry Deposition ◽  
Gaseous Mercury ◽  
Seasonal And Diurnal Variations

Abstract. China is regarded as the largest contributor of mercury (Hg) to the global atmospheric Hg budget. However, concentration levels and depositions of atmospheric Hg in China are poorly known. Continuous measurements of atmospheric total gaseous mercury (TGM) were carried out from May 2008 to May 2009 at the summit of Mt. Leigong in south China. Wet and dry deposition fluxes of Hg were also calculated following collection of precipitation, throughfall and litterfall. Atmospheric TGM concentrations averaged 2.80±1.51 ng m−3, which was highly elevated compared to global background values but much lower than semi-rural and industrial/urban areas in China, indicating great emissions of Hg in central, south and southwest China. Seasonal and diurnal variations of TGM were observed, which reflected variations in source intensity, deposition processes and meteorological factors. Wet deposition of Hg was quite low, while its dry deposition of Hg (litterfall + throughfall-direct wet deposition) constituted a major portion of total deposition (~88% for total mercury (THg) and 84% for methyl mercury (MeHg)). This highlights the importance of vegetation to Hg atmospheric cycling. In a remote forest ecosystem of China, dry deposition of TGM, especially gaseous elemental mercury (GEM), was very important for the depletion of atmospheric Hg. Elevated TGM level in ambient air may accelerate the foliar uptake of Hg through air which may partly explain the elevated Hg dry deposition fluxes observed in Mt. Leigong.

scholarly journals Spatial distribution and seasonal variations of atmospheric sulfur deposition over Northern China

2012 ◽  
Vol 12 (9) ◽  
pp. 23645-23677 ◽  
Author(s):  
Y. P. Pan ◽  
Y. S. Wang ◽  
G. Q. Tang ◽  
D. Wu
Keyword(s):  
Acid Deposition ◽  
Seasonal Variations ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Northern China ◽  
Anthropogenic Emissions ◽  
Deposition Flux ◽  
Natural Ecosystems ◽  
Total Acid ◽  
S Deposition

Abstract. The increasing anthropogenic emissions of acidic compounds have induced acid deposition accompanied by acidification in the aquatic and terrestrial ecosystems worldwide. However, comprehensive assessment of spatial patterns and long-term trends of acid deposition in China remains a challenge due to a paucity of field-based measurement data, in particular for dry deposition. Here we quantify the sulfur (S) deposition on a regional scale via precipitation, particles and gases during a 3-yr observation campaign at ten selected sites in Northern China. Results show that the total S deposition flux in the target area ranged from 35.0 to 100.7 kg S ha−1 yr−1, categorized as high levels compared to those documented in Europe, North America, and East Asia. The ten-site, 3-yr average total S deposition was 64.8 kg S ha−1 yr−1, with 32% attributed to wet deposition, and the rest attributed to dry deposition. Compared with particulate sulfate, gaseous SO2 was the major contributor of dry-deposited S, contributing approximately 49% to the total flux. Wet deposition of sulfate showed pronounced seasonal variations with maximum in summer and minimum in winter, corresponding to precipitation patterns in Northern China. However, the spatial and inter-annual differences in the wet deposition were not significant, which were influenced by the precipitation amount, scavenging ratio and the concentrations of atmospheric S compounds. In contrast, the relatively large dry deposition of SO2 and sulfate during cold season, especially at industrial areas, was reasonably related to the local emissions from home heating. Although seasonal fluctuations were constant, clear spatial differences were observed in the total S deposition flux and higher values were also found in industrial areas with huge emissions of SO2. These findings indicate that human activity has dramatically altered the atmospheric S deposition and thus regional S cycles. To systematically illustrate the potential effects of acidifying deposition on the receiving environment, we calculated the deposition of "potential acidity" that takes into account the microbial transformation of ammonium to nitrate in the ecosystems, resulting in the release of hydrogen ions. The estimated total "acid equivalents" deposition of S and nitrogen (N) fell within the range of 4.2–11.6 keq ha−1 yr−1, with a ten-site, 3-yr mean of 8.4 keq ha−1 yr−1. This value is significantly higher than that of other regions in the world and exceeds the critical loads for natural ecosystems in Northern China, thus prompting concerns regarding ecological impacts. The contribution of S to total acid deposition was comparable to that of N at most of sites; however, the importance of S on acidification risks was more pronounced in the industrial sites, highlighting that further SO2 abatement from industrial emissions is still needed. Taking these findings and our previous studies together, a multi-pollutant perspective and joint mitigate strategies to abate SO2 and NH3 simultaneously in the target areas are recommended to protect the natural ecosystems from excess acid deposition caused by anthropogenic emissions.

scholarly journals Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution

2014 ◽  
Vol 14 (2) ◽  
pp. 1107-1121 ◽  
Author(s):  
K. Osada ◽  
S. Ura ◽  
M. Kagawa ◽  
M. Mikami ◽  
T. Y. Tanaka ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Mineral Dust ◽  
Potential Temperature ◽  
Temporal Variations ◽  
Dust Particles ◽  
Spatial Distributions ◽  
Dust Deposition ◽  
Deposition Fluxes ◽  
Wet And Dry Deposition

Abstract. Recent ground networks and satellite remote-sensing observations have provided useful data related to spatial and vertical distributions of mineral dust particles in the atmosphere. However, measurements of temporal variations and spatial distributions of mineral dust deposition fluxes are limited in terms of their duration, location, and processes of deposition. To ascertain temporal variations and spatial distributions of mineral dust deposition using wet and dry processes, weekly deposition samples were obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo (Okinawa) in Japan during October 2008–December 2010 using automatic wet and dry separating samplers. Mineral dust weights in water-insoluble residue were estimated from Fe contents measured using an X-ray fluorescence analyser. Wet and dry deposition fluxes of mineral dusts were both high in spring and low in summer, showing similar seasonal variations to frequency of aeolian dust events (Kosa) in Japan. For wet deposition, highest and lowest annual dust fluxes were found at Toyama (9.6 g m−2 yr−1) and at Cape Hedo (1.7 g m−2 yr−1) as average values in 2009 and 2010. Higher wet deposition fluxes were observed at Toyama and Tottori, where frequent precipitation (> 60% days per month) was observed during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and Cape Hedo, the highest and lowest annual dust fluxes were found respectively at Fukuoka (5.2 g m−2 yr−1) and at Cape Hedo (2.0 g m−2 yr−1) as average values in 2009 and 2010. The average ratio of wet and dry deposition fluxes was the highest at Toyama (3.3) and the lowest at Hedo (0.82), showing a larger contribution of the dry process at western sites, probably because of the distance from desert source regions and because of the effectiveness of the wet process in the dusty season. Size distributions of refractory dust particles were obtained using four-stage filtration: > 20, > 10, > 5, and > 1 μm diameter. Weight fractions of the sum of > 20 μm and 10–20 μm (giant fraction) were higher than 50% for most of the event samples. Irrespective of the deposition type, the giant dust fractions generally decreased with increasing distance from the source area, suggesting the selective depletion of larger giant particles during atmospheric transport. Based on temporal variations of PMc (2.5 < D < 10 μm), ground-based lidar, backward air trajectories, and vertical profiles of potential temperatures, transport processes of dust particles are discussed for events with high-deposition and low-deposition flux with high PMc. Low dry dust depositions with high PMc concentrations were observed under stronger (5 K km−1) stratification of potential temperature with thinner and lower (< 2 km) dust distributions because the PMc fraction of dust particles only survived after depletion of giant dust particles by rapid gravitational settling at the time they reach Japan. In contrast, transport through a thicker (> 2 km) dust layer with weak vertical gradient of potential temperature carry more giant dust particles to Japan. Because giant dust particles are an important mass fraction of dust accumulation, especially in the North Pacific, which is known as a high-nutrient, low-chlorophyll (HNLC) region, the transport height and fraction of giant dust particles are important factors for studying dust budgets in the atmosphere and their role in biogeochemical cycles.

scholarly journals Spatial distribution and temporal variations of atmospheric sulfur deposition in Northern China: insights into the potential acidification risks

2013 ◽  
Vol 13 (3) ◽  
pp. 1675-1688 ◽  
Author(s):  
Y. P. Pan ◽  
Y. S. Wang ◽  
G. Q. Tang ◽  
D. Wu
Keyword(s):  
Spatial Distribution ◽  
Dry Deposition ◽  
Wet Deposition ◽  
Northern China ◽  
Mitigation Strategies ◽  
Deposition Flux ◽  
Target Area ◽  
Natural Ecosystems ◽  
Atmospheric Sulfur ◽  
S Deposition

Abstract. Atmospheric sulfur (S) deposition via precipitation, particles and gases was investigated at ten sites in Northern China. Measurements were performed continuously between December 2007 and November 2010. The total S deposition flux in the target area ranged from 35.0 to 100.7 kg S ha−1 yr−1, noticeably higher than the values documented in Europe, North America, and East Asia. The ten-site, 3-yr average total S deposition was 64.8 kg S ha−1 yr−1, with 68% attributed to dry deposition (mainly SO2) and the rest to wet deposition. Consequently, the spatial distribution of the total flux was consistent to that of dry deposition, that is, higher values were observed at industrial and urban sites than at agricultural and rural sites. However, the seasonal variation in the total S deposition was not obvious across the entire year because of opposite seasonal trends in wet and dry deposition. It was found that the wet deposition, without significant spatial and interannual differences, was influenced by the volume of precipitation, the air-column concentrations of S compounds and in-cloud scavenging. Similar to the wet deposition, the dry-deposited sulfate was also less dependent on the surface concentration. Nevertheless, the regional differences in SO2 dry deposition were mostly explained by the ambient concentration, which is closely associated with local emissions. As expected, the spatial pattern of total S deposition resembled that of the emission inventory, indicating the dramatic anthropogenic imprints on the regional S budget. Although at most of the study sites the "acid equivalents" deposition of S was comparable to that of nitrogen (N), the importance of S in the acidification risks was more pronounced at the industrial sites. The ten-site, 3-yr mean total "acid equivalents" deposition of S and N was estimated to be 8.4 (range: 4.2–11.6) keq ha−1 yr−1, which exceeds the critical loads for natural ecosystems in Northern China. Taking these findings and our previous studies together, a multi-pollutant perspective and joint mitigation strategies to abate SO2 and NH3 simultaneously in the target area are recommended to protect natural ecosystems from excess acid deposition.

Atmospheric transport and deposition of trace elements to lake erie from Urban areas

1996 ◽  
Vol 33 (4-5) ◽  
pp. 259-265
Author(s):  
Gerald J. Keeler ◽  
Nicola Pirrone
Keyword(s):  
Trace Elements ◽  
Urban Areas ◽  
Lake Erie ◽  
Atmospheric Transport ◽  
Spatial And Temporal Variation ◽  
Deposition Flux ◽  
Emission Sources ◽  
Dry Deposition Flux ◽  
Ambient Concentration ◽  
Ambient Concentrations

A hybrid receptor-deposition (HRD) modeling approach was used to determine the spatial and temporal variation in the ambient concentration and dry deposition flux of trace elements on fine (&lt; 2.5 mm) and coarse (&gt; 2.5 mm) particulate matter over Lake Erie. Upper-air observations from the National Weather Service (NWS) and ambient concentrations measured at two sampling sites downwind of major emission sources in the Lake Erie basin were input to the model. An evaluation of the deposition flux of size-segregated trace elements to the lake during the over-water transport was performed. The average total (fine + coarse) deposition flux was 9.6 ng/m2-h for V, 70 ng/m2-h for Mn, 3.2 ng/m2-h for As, 4.2 ng/m2-h for Se, 10 ng/m2-h for Cd, and 43.3 ng/m2-h for Pb.

scholarly journals Triple oxygen isotopes indicate urbanization affects sources of nitrate in wet and dry atmospheric deposition

2018 ◽  
Author(s):  
David M. Nelson ◽  
Urumu Tsunogai ◽  
Ding Dong ◽  
Takuya Ohyama ◽  
Daisuke D. Komatsu ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Urban Environments ◽  
Rural Site ◽  
Urban Site ◽  
Peroxy Radicals ◽  
Long Distance ◽  
Wet And Dry Deposition ◽  
Atmospheric Nitrate ◽  
Nitrate Deposition

Abstract. Atmospheric nitrate deposition resulting from anthropogenic activities negatively affects human and environmental health. Identifying deposited nitrate that is produced locally vs. that originating from long-distance transport would help inform efforts to mitigate such impacts. However, distinguishing the relative transport distances of atmospheric nitrate in urban areas remains a major challenge since it may be produced locally and/or come from upwind regions. To address this uncertainty we assessed spatiotemporal variation in monthly weighted-average Δ17O and δ15N values of wet and dry nitrate deposition during one year at urban and rural sites along the western coast of the northern Japanese island of Hokkaido, downwind of the East Asian continent. Δ17O values of nitrate in wet deposition at the urban site mirrored those of wet and dry deposition at the rural site, ranging between ~ +22 and +30 ‰ with higher values during winter and lower values in summer, which suggests greater relative importance of oxidation of NO2 by O3 during winter and OH during summer. In contrast, Δ17O values of nitrate in dry deposition at the urban site were lower (+19–+25 ‰) and displayed less distinct seasonal variation. Furthermore, the difference between δ15N values of nitrate in wet and dry nitrate deposition was, on average, 3 ‰ greater at the urban than rural site, and Δ17O and δ15N values were correlated for both forms of deposition at both sites with the exception of dry deposition at the urban site. These results suggest that, relative to nitrate in wet deposition in urban environments and wet and dry deposition in rural environments, nitrate in dry deposition in urban environments forms from relatively greater oxidation of NO by peroxy radicals and/or oxidation of NO2 by OH. Given greater concentrations of peroxy radicals and OH in cities, these results imply that dry nitrate deposition results from local NOx emissions more so than wet deposition, which is transported longer distances. These results illustrate the value of stable isotope data for distinguishing the transport distances and reaction pathways of atmospheric nitrate pollution.

scholarly journals Characteristics of atmospheric mercury deposition and size-fractionated particulate mercury in urban Nanjing, China

2014 ◽  
Vol 14 (5) ◽  
pp. 2233-2244 ◽  
Author(s):  
J. Zhu ◽  
T. Wang ◽  
R. Talbot ◽  
H. Mao ◽  
X. Yang ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Fine Particles ◽  
Unit Area ◽  
Atmospheric Mercury ◽  
Anthropogenic Sources ◽  
Deposition Flux ◽  
Coarse Particles ◽  
Mercury Deposition ◽  
Particulate Mercury

Abstract. A comprehensive measurement study of mercury wet deposition and size-fractionated particulate mercury (HgP) concurrent with meteorological variables was conducted from June 2011 to February 2012 to evaluate the characteristics of mercury deposition and particulate mercury in urban Nanjing, China. The volume-weighted mean (VWM) concentration of mercury in rainwater was 52.9 ng L−1 with a range of 46.3–63.6 ng L−1. The wet deposition per unit area was averaged 56.5 μg m−2 over 9 months, which was lower than that in most Chinese cities, but much higher than annual deposition in urban North America and Japan. The wet deposition flux exhibited obvious seasonal variation strongly linked with the amount of precipitation. Wet deposition in summer contributed more than 80% to the total amount. A part of contribution to wet deposition of mercury from anthropogenic sources was evidenced by the association between wet deposition and sulfates, as well as nitrates in rainwater. The ions correlated most significantly with mercury were formate, calcium, and potassium, which suggested that natural sources including vegetation and resuspended soil should be considered as an important factor to affect the wet deposition of mercury in Nanjing. The average HgP concentration was 1.10 ± 0.57 ng m−3. A distinct seasonal distribution of HgP concentrations was found to be higher in winter as a result of an increase in the PM10 concentration. Overall, more than half of the HgP existed in the particle size range less than 2.1 μm. The highest concentration of HgP in coarse particles was observed in summer, while HgP in fine particles dominated in fall and winter. The size distribution of averaged mercury content in particulates was bimodal, with two peaks in the bins of < 0.7 μm and 4.7–5.8 μm. Dry deposition per unit area of HgP was estimated to be 47.2 μg m−2 using meteorological conditions and a size-resolved particle dry deposition model. This was 16.5% less than mercury wet deposition. Compared to HgP in fine particles, HgP in coarse particles contributed more to the total dry deposition due to higher deposition velocities. Negative correlation between precipitation and the HgP concentration reflected the effect of scavenging of HgP by precipitation.

scholarly journals Temporal and Spatial variation of Contribution from Ship Emissions to the concentration and deposition of air pollutants in the Baltic Sea

2016 ◽  
Author(s):  
Karin Haglund ◽  
Björn Claremar ◽  
Anna Rutgersson
Keyword(s):  
Atmospheric Deposition ◽  
Baltic Sea ◽  
Dry Deposition ◽  
Air Pollutants ◽  
Wet Deposition ◽  
Sulphur Content ◽  
The Baltic Sea ◽  
Near Surface ◽  
Baltic Sea Region ◽  
The Baltic

Abstract. The shipping sector contributes significantly to increasing emissions of air pollutants. In order to achieve sustainable shipping, primarily through new regulations and techniques, greater knowledge of dispersion and deposition of air pollutants is required. Regional model calculations of the dispersion and deposition of sulphur, nitrogen and particulate matter from the international maritime sector in the Baltic Sea and the North Sea have been made for the years 2009 to 2013. In some areas in the Baltic Sea region the contribution of sulphur dioxide, nitrogen oxide and nitrogen dioxide from international shipping represented up to 80 % of the total near surface concentration of the pollutants. Contributions from shipping of PM2,5 and PM10 were calculated to a maximum of 21 % and 13 % respectively. The contribution of wet deposition of sulphur from shipping was maximum 29 % of the total wet deposition, and for dry deposition the contribution from shipping was maximum 84 %. The highest percentage contribution of wet deposition of nitrogen from shipping reached 28 % and for dry deposition 47 %. The highest concentrations and deposition of the pollutants in the study were found near large ports and shipping lanes. High concentrations were also found over larger areas at sea and over land where many people are exposed. With enhanced regulations for sulphur content in maritime fuel, the cleaning of exhausts through scrubbers has become a possible economic solution. Wet scrubbers meet the air quality criteria but their consequences for the marine environment are largely unknown. The resulting potential of future acidification in the Baltic Sea, both from atmospheric deposition and from open-loop scrubber water along the shipping lanes, based on different assumptions about sulphur content in fuel and scrubber usage has been assessed. Shipping is expected to increase globally and in the Baltic Sea region, deposition of sulphur due to shipping will depend on traffic density, emission regulations and technology choices for the emission controls. To evaluate future changes scenarios are developed considering the amount of scrubber technology used. The increase in deposition for the different scenarios differs slightly for the basins in the Baltic Sea. The proportion of ocean acidifying sulphur from ships increases when taking scrubber water into account and the major reason to increasing acidifying nitrogen from ships are due to increasing ship traffic. This study also generates a database of scenarios for atmospheric deposition and scrubber exhaust from the period 2011 to 2050.

scholarly journals Wet and dry deposition of mineral dust particles in Japan: factors related to temporal variation and spatial distribution

2013 ◽  
Vol 13 (8) ◽  
pp. 21801-21835
Author(s):  
K. Osada ◽  
S. Ura ◽  
M. Kagawa ◽  
M. Mikami ◽  
T. Y. Tanaka ◽  
...  
Keyword(s):  
Dry Deposition ◽  
Wet Deposition ◽  
Mineral Dust ◽  
Temporal Variations ◽  
Dust Particles ◽  
Insoluble Residue ◽  
Spatial Distributions ◽  
Dust Deposition ◽  
Deposition Fluxes ◽  
Deposition Amount

Abstract. Data of temporal variations and spatial distributions of mineral dust deposition fluxes are very limited in terms of duration, location, and processes of deposition. To ascertain temporal variations and spatial distributions of mineral dust deposition by wet and dry processes, weekly deposition samples were obtained at Sapporo, Toyama, Nagoya, Tottori, Fukuoka, and Cape Hedo (Okinawa) in Japan during October 2008–December 2010 using automatic wet and dry separating samplers. Mineral dust weights in water-insoluble residue were estimated from Fe contents measured using an X-ray fluorescence analyzer. For wet deposition, highest and lowest annual dust fluxes were found at Toyama (9.6 g m−2 yr−1) and at Cape Hedo (1.7 g m−2 yr−1) as average values in 2009 and 2010. Higher wet deposition fluxes were observed at Toyama and Tottori, where frequent precipitation (>60% days per month) was observed during dusty seasons. For dry deposition among Toyama, Tottori, Fukuoka, and Cape Hedo, the highest and lowest annual dust fluxes were found respectively at Fukuoka (5.2 g m−2 yr−1) and at Cape Hedo (2.0 g m−2 yr−1) as average values in 2009 and 2010. Although the seasonal tendency of the monthly dry deposition amount roughly resembled that of monthly days of Kosa dust events, the monthly amount of dry deposition was not proportional to monthly days of the events. Comparison of dry deposition fluxes with vertical distribution of dust particles deduced from Lidar data and coarse particle concentrations suggested that the maximum dust layer height or thickness is an important factor for controlling the dry deposition amount after long-range transport of dust particles. Size distributions of refractory dust particles were obtained using four-stage filtration: >20, >10, >5, and >1 μm diameter. Weight fractions of the sum of >20 μm and 10–20 μm (giant fraction) were higher than 50% for most of the event samples. Irrespective of the deposition type, the giant dust fractions were decreasing generally with increasing distance from the source area, suggesting the selective depletion of larger giant particles during atmospheric transport. Because giant dust particles are an important mass fraction of dust accumulation, especially in the north Pacific where is known as a high-nutrient, low-chlorophyll (HNLC) region, the transport height of giant dust particles is an important factor for studying dust budgets in the atmosphere and their role in biogeochemical cycles.

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