Atmospheric Dry Deposition Fluxes Research Articles

Characteristics of Cd Fluxe in Topsoil Around Typical Mining Area in Hezhou, Guangxi

Guangxi is a typical geological high background area in southwest China, where carbonates, black rock series, basic-ultrabasic rock mass, and metal deposits (mineralized bodies) exhibit strong weathering into loam, resulting in higher cadmium (Cd) content in the soil than that in other areas of China. In order to investigate the degree of influence of mining activities on topsoil environmental quality in the area with high geological background, we chose a mining area and control area in Hezhou for this research and systematically carried out a comparative study on Cd transport routes and transport flux density in topsoil. The results showed that the average atmospheric dry and wet deposition flux densities of Cd in the soil of the mining area and control area were 1.87 g·(hm2·a)-1 and 1.52 g·(hm2·a)-1, accounting for 61.5% and 60.3% of the total input flux density, respectively. The flux density of Cd in the soil by fertilization and irrigation was lower. Surface water infiltration was the main avenue of soil Cd output in both the mining area and control area, accounting for 75.4% and 86.6% of the total output flux density, respectively. The harvest output flux density in the mining area was higher than that in the control area, and the Cd content of rice planted in the mining area was higher than the standard, whereas that of maize was safe. On the whole, the net transport flux densities of soil Cd in the mining area and control area were -3.05 g·(hm2·a)-1 and -4.05 g·(hm2·a)-1, both of which showed Cd leaching in the soil. However, the points of high atmospheric deposition flux density and exceeding Cd content in rice were mainly distributed around the mining area, which may have posed a potential threat to the health of local residents. Therefore, it is suggested to control the soil Cd pollution through monitoring and planting structure adjustment.

Gas–particle partitioning and dry deposition of atmospheric parent, alkylated, nitrated and hydroxyl polycyclic aromatic hydrocarbons over the Bohai sea and northern Yellow sea in autumn

To elucidate the gas–particle partitioning characteristics and dry deposition contributions of polycyclic aromatic hydrocarbons (PAHs) in the marine environment, 23 integrated air samples were collected during a research cruise in the northern Yellow Sea (NYS) and Bohai Sea (BS) in mid-autumn 2020. The atmospheric concentrations of 23 parent PAHs (PPAHs), 18 alkylated PAHs (APAHs), five nitrated PAHs (NPAHs), and seven hydroxyl PAHs (OPAHs) in gaseous and particulate phases were measured simultaneously. The total concentrations of 53 PAHs varied from 8.77 to 348 ng/m3. The 2-ring and 3-ring PPAHs and APAHs had lower particle-bound fractions than those of the NPAHs and OPAHs. For the gas–particle partitioning of the PAHs, the gas–particle partitioning coefficients (Kp) estimated using an octanol–air partition coefficient (KOA)–based model and KOA/soot–air partition coefficient (KSA) dual model (KOA–KSA dual model) were lower than the Kp measured in the field. Underestimation of the Kp commonly occurred with these models, but the KOA–KSA dual model was more suitable than the KOA–based model for gas–particle partitioning of the 53 atmospheric PAHs in the BS and NYS. The estimated atmospheric dry deposition fluxes of the 53 PAHs ranged from 631 to 14,345 ng/m2/day. The BS receives a PAHs load of up to 117 tons/year. The study provides background information on the occurrence and environmental fate of PAHs and could be vitally important for environmental safety management for the Northwest Pacific Ocean.

The joint effects of atmospheric dry and wet deposition on organic carbon cycling in a mariculture area in North China

In this research, the atmospheric dry and wet deposition fluxes of particulate organic carbon (POC) over the coastal waters around the Yangma Island in North Yellow Sea were investigated. Combining the results of this research and previous reports about the wet deposition fluxes of dissolved organic carbon (DOC) in precipitation (FDOC-wet) and dry deposition fluxes of water-dissolvable organic carbon in atmospheric total suspended particles (FDOC-dry) in this area, a synthetic assessment of the influence of atmospheric deposition on the eco-environment was conducted. It was found that the annual dry deposition flux of POC was 1097.9 mg C m−2 a−1, which was approximately 4.1 times that of FDOC-dry (266.2 mg C m−2 a−1). For wet deposition, the annual flux of POC was 445.4 mg C m−2 a−1, accounting for 46.7 % that of FDOC-wet (954.3 mg C m−2 a−1). Therefore, atmospheric POC was mainly deposited through dry process with the contribution of 71.1 %, which was contrary to the deposition of DOC. Considering the indirect input of organic carbon (OC) from atmospheric deposition, that is, the new productivity supported by nutrient input from dry and wet deposition, the total OC input from atmospheric deposition to the study area could be up to 12.0 g C m−2 a−1, highlighting the important role of atmospheric deposition in the carbon cycling of coastal ecosystems. The contribution of direct and indirect input of OC through atmospheric deposition to the dissolved oxygen consumption in total seawater column was assessed to be lower than 5.2 % in summer, suggesting a relatively smaller contribution to the deoxygenation in summer in this region.

Atmospheric dry deposition fluxes of trace metals over the Eastern China Marginal Seas: Impact of emission controls

Atmospheric deposition is an important exogenous input of trace metals to Eastern China Marginal Seas (ECMS), which is strongly affected by human activities. With emission control practices implemented in China, it still remains unknown what changes have taken place in the atmospheric dry depositions of the trace metals over ECMS. This study aimed to estimate the atmospheric dry depositions of Zn, Pb, Cu, and Cd over ECMS via Weather Research and Forecasting Model-Community Multiscale Air Quality Modeling System (WRF-CMAQ) in the two winter periods of January 2012 and January 2019 as well as to explore the impacts of emission control on the depositions. The anthropogenic metal emissions from China, the Korean Peninsula, Japan, and marine ships were investigated in this study. In 2012, the dry deposition fluxes of Zn, Pb, Cu, and Cd over ECMS were in the ranges of 0.50–3.4 μg m−2 d−1, 0.22–1.9 μg m−2 d−1, 0.14–0.90 μg m−2 d−1, and 12–88 ng m−2 d−1, respectively. The deposition fluxes of the four metals over Bohai Sea (BS) and Yellow Sea (YS) were 2–3 times those over East China Sea (ECS). Outflow of polluted air masses from East Asia increased the metal depositions by 3– 5-fold relative to clear days. Compared with 2012, a 5–85 % reduction in the metal depositions over ECMS were estimated in 2019, largest reductions were found over YS and BS. Meteorological variation was able to decrease or increase the metal depositions. However, the emission control only caused a reduction in the entire study region. The metal inputs to the sea were significantly lower from the ship emissions than from the continental anthropogenic emissions, although the proportion of the ship emissions in the total metal depositions rose slightly from 2012 to 2019.

Estimation of Atmospheric Dry and Wet Deposition of Particulate Elements at Four Monitoring Sites in the Canadian Athabasca Oil Sands Region

AbstractThis study develops a framework for estimating atmospheric dry deposition using the inferential approach, and wet deposition using the scavenging ratio approach for particulate elements monitored in the Athabasca oil sands region (AOSR) of Canada. The framework was applied to four monitoring sites (AMS01, AMS04, AMS17, and AMS18) in the AOSR where ambient concentrations of particulate elements were collected in 2016–2017 to estimate atmospheric dry and wet deposition fluxes of 35 elements, including eight USEPA priority elements. Annual total (dry + wet) deposition of the individual elements in PM10 varied by about five orders of magnitudes, ranging from 3 (μg/m2/year) for Yb to 172,000 (μg/m2/year) for Si. Total deposition of the elements that are typically associated with bitumen (e.g., Mo, Ni, and V) did not show any statistically significant spatial variations (p < 0.05). However, S, which is significantly enriched in bitumen and its byproducts, had up to 38% higher fluxes at AMS01 and AMS17 (closer to the oil sands facilities) than at AMS18 (background site). Wet deposition fluxes dominated over the dry deposition fluxes for almost all elements due to efficient snow scavenging and prolonged winter season. Dry deposition fluxes of the crustal elements were higher in the summer season due to their elevated concentrations in PM2.5–10 during the warmer months, whereas most anthropogenic elements did not show any significant seasonal variations. The total deposition of the individual priority toxic elements considered in this study ranged from 6 (μg/m2/year) (Cd; AMS18) to 2,290 (µg/m2/year) (Zn; AMS04), and ranked as follows: Zn > Cu > Ni > Cr > Sb > As > Pb > Cd.

Occurrence and dry deposition of organophosphate esters in atmospheric particles above the Bohai Sea and northern Yellow Sea, China

Levels of eleven organophosphate esters (OPEs) were measured in particle phase atmospheric samples collected at Bohai Sea and northern Yellow Sea in China. The concentration of ∑11OPEs in atmospheric particles ranged from 426 to 3933 pg/m3, with the mean concentration of 1412 pg/m3. Tris(1-chloro-2-propyl) phosphate (TCPP) and triphenyl-phosphine oxide (TPPO) were the most abundant OPE congeners measured, and the individual concentrations of trimethyl phosphate (TMP), tri-iso-butyl phosphate (TiBP), tri-n-butyl phosphate (TnBP), tris(1,3-dichloro-2-propyl) phosphate (TDCP), triphenyl phosphate (TPhP), 2-ethylhexyl diphenyl phosphate (EHDPP), TPPO and tri-m-cresyl phosphate (TMTP) in atmospheric particles above the Bohai Sea were higher than those above the northern Yellow Sea. The estimated atmospheric dry deposition fluxes ranged from 202 to 1869 ng/m2/day. Up to 18.3 ± 12.5 ton/year of OPEs can be loaded to the Bohai Sea.

Origin, transport and deposition of aerosol iron to Australian coastal waters

Australia is a major source of Fe-laden dust to the anemic marine phytoplankton in the Southern Ocean and to Southern Hemisphere (SH) low latitudes diazotrophic bacteria. However, the paucity of observations and laboratory experiments on SH aerosols biases model predictions of atmospheric Fe deposition to the southern oceans and the subsequent response of ocean productivity. As a result of an extensive shipboard aerosol sampling effort, this study presents laboratory measurements of aerosol Fe concentrations, solubilities and fluxes and analysis of chemical tracers, highlighting the large heterogeneity between aerosol Fe sources in 5 coastal regions around Australia. While dust-sourced high Fe loadings and low Fe solubilities (5%) aerosols dominate the atmospheric burden of the western coasts of Australia, much lower Fe concentrations but greater Fe solubilities (10.5% and 13%) were measured in aerosols along the east coast which was attributed to solubility-enhancing atmospheric reactions with anthropogenic pollutants. Surprisingly high aerosol Fe solubilities (>20%) in northern Australia aerosols were associated with direct emissions or atmospheric reactions with bushfire emissions at tropical latitudes, which accounted for 49% of the total (sum) atmospheric dry deposition flux of labile Fe measured across the continent's surrounding seawaters in this study.

Concentrations, fluxes, and potential sources of nitrogen and phosphorus species in atmospheric wet deposition of the Lake Qinghai Watershed, China

Plateau lakes are typically dystrophic and are sensitive to small changes in nutrient deposition. With this assumption, we investigated the concentrations, fluxes, and sources of nitrogen (N) and phosphorus (P) in the atmospheric wet deposition (AWD) of the Lake Qinghai Watershed (LQW), which is the largest inland lake in China, for one year from October 2017 to September 2018. The results showed that the annual volume-weighted mean (VWM) concentrations (mg L−1) in the AWD were 1.97 for NH4+-N, 0.55 for NO3−-N, 0.04 for NO2−-N, 0.77 for dissolved organic N (DON), 3.33 for total dissolved N (TDN), 0.30 for dissolved inorganic P (DIP), 0.07 for dissolved organic P (DOP), 0.36 for total dissolved P (TDP), and 0.99 for reactive sulfur (SO42−-S). The annual AWD fluxes of TDN and TDP were 16.82 and 1.86 kg ha−1 yr−1, respectively. Strong dilution effects in the wet season, a long residency time of nutrient-rich aerosols in the dry season, strong ammonia volatilization in the wet and warm seasons, and moisture sources dominated the seasonal or monthly changing characteristics of N and P concentrations in the AWD, including high in the wet season and low in the dry season for NH4+-N, low in the wet season and high in the dry season for NO3−-N, and generally increasing from April to September for DIP and DOP. Precipitation quantity dominated the monthly changes in the N and P fluxes of the AWD, which gradually increased from April to August and then decreased in September. N and P in the AWD mostly originated from anthropogenic sources. High ammonia volatilization from local intense animal husbandry, alkaline soils and lakes led to a relatively high NH4+-N concentration compared with other sites of the Qinghai-Tibet Plateau, China, and in the world. The N/P molar ratio in the precipitation was higher than 16, which might have effect on the aquatic ecosystems of Lake Qinghai. Ammonia volatilization fluxes and atmospheric dry deposition fluxes of N and P should be further studied to completely understand the geochemical cycles of N and P in the LQW.

Pollution Characteristics, Dry Deposition Fluxes, and Sources for Atmospheric Polycyclic Aromatic Hydrocarbons in the Bosten Lake Watershed

Passive air samplers (PAS-PUF) and passive dry deposition (PAS-DD) samplers were applied in the Bosten Lake watershed located in Xinjiang to estimate the atmospheric concentrations and dry deposition fluxes for 15 US EPA priority polycyclic aromatic hydrocarbons (PAHs) during a heating period in 2016 and no-heating period in 2017, respectively. The results showed that the atmospheric PAHs concentrations in the Bosten oasis area ranged from 6.38 ng·m-3 to 245.43 ng·m-3 during the heating period and 2.33 ng·m-3 to 74.76 ng·m-3 during the non-heating period. The highest atmospheric PAHs concentrations were found in the residential area, followed by regions near Bosten Lake and Tazhong. The atmospheric dry deposition fluxes of PAHs in the Bosten Lake watershed ranged from 0.45 μg·(m2·d)-1 to 18.10 μg·(m2·d)-1 during the heating period and 0.25 μg·(m2·d)-1to 8.15 μg·(m2·d)-1 during the non-heating period. During the heating period, the atmospheric dry deposition fluxes in the residential area were significantly higher than those in the regions near Bosten Lake and Tazhong. However, the atmospheric PAHs dry deposition flux in Tazhong was much higher than that in other sites during the heating and no-heating periods. In general, the atmospheric PAHs dry deposition fluxes during the heating period were significantly higher than those during the non-heating period. PAH composition for the atmosphere and dry deposition were dominated by 3 and 4 ring congeners, especially by phenanthrene, fluorine, fluoranthene, and pyrene during two sampling periods. In addition, the congener diagnostic ratio shows that coal and biomass combustion were possible sources of atmospheric PAHs in the Bosten Lake watershed. The forward and backward trajectory analysis based on the HYSPLIT model demonstrated that the higher atmospheric PAH emissions from the residential area would be transported to Bosten Lake, which can affect the aquatic environment of this lake by dry deposition.

Size-fractionated particulate elements in an inland city of China: Deposition flux in human respiratory, health risks, source apportionment, and dry deposition

Size-resolved samples were collected using a 14-stage impactor during four seasons in Zhengzhou and analyzed for 26 elements to calculate the health risks from atmospheric particle-bound metals. High concentrations of heavy metals were observed in ultrafine (10.2 (Ni)–66.9 (Cd) ng m−3) or submicrometer (11.4 (Ni)–134 (Pb) ng m−3) mode in winter. Two size-dependent models were used to estimate the deposition of inhaled toxic metals in various regions of the human respiratory system. Results show that heavy metals deposited in the alveolar region ranged from 7.6 (As)–375 (Al) ng m−3 and were almost concentrated in ultrafine and fine modes. Cd (2.2–8.6) may cause accumulative non-carcinogenic health effects on children, and Cr (1.0 × 10−4–2.2 × 10−4) may lead to carcinogenic health risks for nearby residents around the sampling site. The major sources by principal component analysis that contributed to Cr and Cd in ultrafine and fine particles were coal combustion, vehicular and industrial emissions. The atmospheric dry deposition fluxes of Cr and Cd were between 0.7 and 1.9 μg m−2 day−1 calculated by a multi-step method. From the environmental and public health perspective, environmental agencies must control the emission of heavy metals in the atmosphere.

Sources and dry deposition of carbonaceous aerosols over the coastal East China Sea: Implications for anthropogenic pollutant pathways and deposition

75 paired TSP and PM2.5 samples were collected over four seasons on Huaniao Island (HNI), an island that lies downwind of continental pollutants emitted from mainland China to the East China Sea (ECS). These samples were analyzed for organic carbon (OC) and elemental carbon (EC), with a special focus on char-EC (char) and soot-EC (soot), to understand their sources, and the scale and extent of pollution and dry deposition over the coastal ECS. The results showed that char concentrations in PM2.5 and TSP averaged from 0.13 to 1.01 and 0.31–1.44 μg m−3; while for soot, they were from 0.03 to 0.21 and 0.16–0.56 μg m−3, respectively. 69.0% of the char and 36.4% of the soot were present in PM2.5. The char showed apparent seasonal variations, with highest concentrations in winter and lowest in summer; while soot displayed maximum concentrations in fall and minimum in summer. The char/soot ratios in PM2.5 averaged from 3.29 to 17.22; while for TSP, they were from 1.20 to 7.07. Both of the ratios in PM2.5 and TSP were highest in winter and lowest in fall. Comparisons of seasonal variations in OC/EC and char/soot ratios confirmed that char/soot may be a more effective indicator of carbonaceous aerosol source identification than OC/EC. Annual average atmospheric dry deposition fluxes of OC and EC into ECS were estimated to be 229 and 107 μg m−2 d−1, respectively, and their deposition fluxes significantly increased during episodes. It was estimated that the loadings of OC + EC and EC accounted for 1.3% and 4.1% of the total organic carbon and EC in ECS surface sediments, respectively, implying a relatively small contribution of OC and EC dry deposition to organic carbon burial. This finding also indicates a possibly more important contribution of wet deposition to organic carbon burial in sediments of ECS, and this factor should be considered for future study.

Atmospheric particle-bound organophosphate ester flame retardants and plasticizers in a North African Mediterranean coastal city (Bizerte, Tunisia)

Organophosphate ester (OPE) flame retardants and plasticizers have been detected at generally high frequencies (70–98%) for the first time in the atmosphere over the NW African coastal Mediterranean. Results from sixty air samples (total suspended particles, TSP) collected between March 2015 and January 2016 in an urban coastal site (Bizerte, Tunisia) revealed ∑9OPE concentrations of ~100–1060 pg m−3 (470 pg m−3, median) with TCPPs, EHDPP and TiBP exhibiting the higher median concentrations (~110, 100 and 85 pg m−3, respectively). Spring generally exhibited the lowest concentrations, probably linked to the influence of local meteorological conditions and air mass trajectories to a lesser extent. Non-chlorinated OPEs generally predominated, in contrast to the most common reported situation in marine environments (i.e. higher abundance of chlorinated OPEs) pointing to the relevance of local OPE sources in the study area. TiBP levels were generally higher than those reported for other marine/coastal environments suggesting this OPE as a good tracer of local sources in Bizerte. Contrarily, the atmospheric levels of other abundant OPEs in the area (e.g. TCPP) seem to be in the range and/or lower than those reported for remote marine environments. These findings point to the interplay of different factors with solar irradiance (potentially enhancing atmospheric photochemical oxidation reactions) and meteorological conditions in the study area likely compensating potential local sources of some OPEs. Not all OPEs presented the same seasonality in terms of atmospheric concentrations and pattern. The estimated atmospheric dry deposition fluxes (∑9OPEs) were 18–180 ng m−2 d−1. Up to ~9 kg y−1 of OPEs (~1 kg y−1 of new organic anthropogenic phosphorus coming from OPEs) can be loaded to the shallow and enclosed Bizerte lagoon (~130 km2), considered as the most important aquaculture area in Tunisia, with yet unknown implications for the environmental exposure and impacts in the ecosystem functioning.

Aerosol concentrations and atmospheric dry deposition fluxes of nutrients over Daya Bay, South China Sea

Based on one and a half years of observations (September 2015 to March 2017) in Daya Bay, we analysed the nutrient concentrations in aerosols and calculated dry deposition fluxes of nutrients. DON was the dominant species of TDN in aerosol particles, accounting for 63.3%. The mean values of DIP, DOP and DSi were 0.78, 0.61 and 2.6 nmol·m−3, respectively. The mean fluxes of nutrients (TDN, TDP and DSi) from dry deposition during the field observation were 2150, 7.4 and 28.2 μmol·m−2·month−1, respectively. The fluxes of nitrogen species show a seasonal pattern with higher input in spring and winter. The dry deposition of nutrients accounted for approximately 20% of the total deposition budget. The molar ratios of DIN/DIP in the dry deposition (mean value 167) suggest that atmospheric dry deposition of nutrients may increase the risk of the unbalanced nutrient condition in the seawater column of Daya Bay.

Atmospheric Dry Deposition Fluxes and Sources of Polycyclic Aromatic Hydrocarbons in Lanzhou Valley, Northwest China

The atmospheric dry deposition flux pollution levels were determined and the sources apportioned for 15 US EPA priority polycyclic aromatic hydrocarbons (PAHs) collected at 13 sampling sites in the Lanzhou valley using passive sampling techniques. The results are as follows. The annual atmospheric dry deposition fluxes ranged from 7.48 to 53.94 μg·(m2·d)-1, with a mean of 18.65 μg·(m2·d)-1. The highest flux levels for both the heating and non-heating seasons, 60.85 μg·(m2·d)-1 and 47.03 μg·(m2·d)-1, respectively, appeared at the traffic site (Donggang Bridge), where the heaviest traffic in the Lanzhou valley occurs. The lowest flux levels of 8.16 μg·(m2·d)-1 and 6.80 μg·(m2·d)-1 for the heating and non-heating seasons, respectively, were found at Baita Mountain, which has a higher percentage of vegetation cover. Meanwhile, the flux levels at the background site (Guantangou Mountain) were significantly lower than those of the other sampling sites. For dry deposition, the PAH components Phe, Flua, Flu, and Pyr were dominant in the heating and non-heating periods, and the sums of the percentages of 3- and 4-ring PAHs were 87.53% for the heating season and 82.73% for the non-heating season. Moreover, the percentage of 5- and 6-ring PAHs for the non-heating period was higher than that for the heating period, which may be because the lighter PAHs were easily volatilized, and thus escaped. Furthermore, the sources of atmospheric dry deposition were identified by principal component analysis (PCA). The results of source apportionment showed that the main atmospheric PAH dry deposition in the Lanzhou valley were from vehicle exhaust emissions, coal combustion, and the coking industry. In further detail, coal combustion and the coking industry contributed most of the PAH dry deposition emissions during the heating period except for the traffic area site of Donggang Bridge, whereas vehicle exhaust was the dominant contributor during the non-heating season. In addition, the annual average dry deposition velocities of atmospheric PAHs were calculated using the dry deposition model for three sites: 0.20 cm·s-1 downtown (Environmental Protection Agency of Lanzhou; JCZ), 0.15 cm·s-1 in an industrial area (Lanyuan Hotel of Xigu; LLH), and 0.17 cm·s-1 in a traffic area (the Staff Hospital of Gansu Province; ZGH), of which the latter two were relatively lower because of comprehensive meteorological factors such as wind speed, temperature, and land use categories. Regarding the dry deposition flux values of the 3- and 4-ring PAHs, the simulated values were a bit larger than the observed values, but all were at the same level of magnitude. However, the simulated flux values were closer to their observed values for 4-ring PAHs than for 3-ring PAHs, which indicated that 3-ring PAHs were lost more easily than 4-ring PAHs were during monitoring.

Atmospheric Dry Deposition Fluxes and Seasonal Variations of Particulate Matter and Lead in Urban Beijing

To investigate the dry deposition pattern of particulate matter and lead in urban Beijing, dry deposited particles were collected based on a surrogate surface between December 2013 and November 2014 and subjected to elemental analysis by using microwave digestion and inductively coupled plasma mass spectrometry. The results showed that dry deposition fluxes of particle mass and total lead were 0.84 t·(hm2·a)-1 and 7.56 mg·(m2·a)-1, respectively, with a seasonal trend of spring > winter > autumn~summer, exhibiting a similar temporal pattern to that of coarse particles. In addition, dry deposition flux of water-soluble lead was 3.14 mg·(m2·a)-1. It was found that the ratio of soluble fraction to total lead in dry deposited particles reached up to 43%, coinciding with a seasonal variation of ambient sulfur dioxide. The findings highlighted the anthropogenic imprints on the dry deposition flux of particles and heavy metals as well as the solubility of lead. This study also provides a first-hand dataset that can be used to assess ecological and environmental impacts of dry deposited lead, and an up-to-date scientific basis for the crafting abatement strategies to further reduce emission of heavy metals in China.

Field measurements of the atmospheric dry deposition fluxes and velocities of polycyclic aromatic hydrocarbons to the global oceans.

The atmospheric dry deposition fluxes of 16 polycyclic aromatic hydrocarbons (PAHs) have been measured, for the first time, in the tropical and subtropical Atlantic, Pacific, and Indian Oceans. Depositional fluxes for fine (0.7-2.7 μm) and coarse (>2.7 μm) aerosol fractions were simultaneously determined with the suspended aerosol phase concentrations, allowing the determination of PAH deposition velocities (vD). PAH dry deposition fluxes (FDD) bound to coarse aerosols were higher than those of fine aerosols for 83% of the measurements. Average FDD for total (fine + coarse) Σ16PAHs (sum of 16 individual PAHs) ranged from 8.33 ng m(-2)d(-1) to 52.38 ng m(-2)d(-1). Mean FDD for coarse aerosol's individual PAHs ranged between 0.13 ng m(-2)d(-1) (Perylene) and 1.96 ng m(-2)d(-1) (Methyl Pyrene), and for the fine aerosol fraction these ranged between 0.06 ng m(-2)d(-1) (Dimethyl Pyrene) and 1.25 ng m(-2)d(-1) (Methyl Chrysene). The estimated deposition velocities went from the highest mean vD for Methyl Chrysene (0.17-13.30 cm s(-1)), followed by Dibenzo(ah)Anthracene (0.29-1.38 cm s(-1)), and other high MW PAHs to minimum values of vD for Dimethyl Pyrene (<0.04 cm s(-1)) and Pyrene (<0.06 cm s(-1)). Dry depositional processes depend on the concentration of PAHs in the suspended aerosol, but also on physicochemical properties and environmental variables (vapor pressure, wind speed, and on the affinity of aerosols for depositing to the sea surface). Empirical parametrizations are proposed to predict the dry depositional velocities of semivolatile organic compounds to the global oceans.

Characterization of Atmospheric Dry Deposition of Polychlorinated Dibenzo-p-dioxins/Dibenzofuran in a Rural Area of Taiwan

The characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and the variation of the gas-particle partitioning of PCDD/Fs near two municipal solid waste incinerators (MSWIs) located in southern Taiwan were investigated. In order to better understand the mechanism of dry deposition, the atmospheric dry deposition flux and velocity of PCDD/Fs were calculated. It was found that the mean atmospheric PCDD/F concentrations (0.0386-0.106 pg I-TEQ/Nm^3) were comparable to those detected in the vicinity of MSWIs in Taiwan, but significantly lower than those in a highly industrialized urban area (0.15 pg I-TEQ/Nm^3) located in southern Taiwan. The relatively higher atmospheric PCDD/F concentrations was found in winter than in summer, probably because of several loss process including photolysis, chemical reactivity, wet and dry deposition, and scavenging by vegetation. The calculated total dry deposition flux of PCDD/Fs ranged from 0.0274-0.718 ng I-TEQ/m^2-month, and the atmospheric deposition flux in winter tended to be higher than those in summer. The results also indicated that dry deposition velocities of atmospheric particles for each month ranged from 0.52-0.91 cm/s (mean=0.63 cm/s) and 0.48-0.73 cm/s (mean=0.55 cm/s) in sites A and B, respectively, which were similar to that for the ambient air near two MSWIs in Taiwan, but slightly higher than those in urban area of Korea. In addition, the dry deposition of PCDD/Fs was mainly contributed by particle-phase at both sampling areas during the estimated period. The above results demonstrated that the dominant mechanism of dry deposition was particle phase deposition.

Apply appropriate models in the study of dry deposition fluxes of particulate matter and polycyclic aromatic hydrocarbons (PAHs) in Tsukuba, Japan

In this study, plates for downward flux and upward flux were used to measure atmospheric dry deposition fluxes for particulate mass and polycyclic aromatic hydrocarbons (PAHs) in TERC (Tsukuba), Japan. Ambient particles concentrations were also collected using a high-volume air sampler, and ambient particle size distributions between 0.01 μm and 13.1 μm were measured using a low-pressure cascade impactor to characterise the PAHs levels and dry deposition. The results indicated that the average cumulative fraction of dry deposition flux for particles and PAHs which attached with them was caused by the particle size of greater than 1.2-6.3 μm (97%).

Measurement of Atmospheric Dry Deposition Flux and Resultant Deposition Velocity of Inorganic Pollutants in the Provincial Capital of Punjab, Pakistan

Inorganic pollutants (IPs), such as Pb, Cu, Zn, and Cd, which are present at trace levels in the atmosphere, are a major group of air pollutants that play important role in atmospheric chemistry. The concentration of such pollutants in the atmosphere is harmful to human health. Data on levels of IPs in the outdoor ambient air is lacking in Pakistan. Knowledge of atmospheric deposition of these IPs in different areas would enable establishing background values that could be used to distinguish additional contributions/ releases when contamination events occur. This knowledge would also help to introduce a strategy to maintain pollution-free air quality. The present study deals with the assessment of atmospheric deposition of IPs at all nine municipal towns in the Lahore City, which is the provincial capital of Punjab province of Pakistan. Sampling work was carried out during March to June 2004. The results show that dry deposition fluxes and deposition velocities of Pb, Cu, Zn, and Cd varied from 7 ± 3 to 30 ± 6 kg km−2 yr−2, 3 ± 2 to 14 ± 6 kg km−2 yr−2, 11 ± 6 to 21 ± 9 kg km−2 yr−2, and 0.7 ± 0.4 to 3 ± 1 kg km−2 yr−2; and 0.4 to 1.4 cm s−1, 0.8 to 1.3 cm s−1, 0.3 to 0.8 cm s−1, and 0.05 to 0.6 cm s−1 respectively. No significant correlations were found between measured deposition fluxes, showing no common emission sources of these pollutants. The data generated in this study will provide baseline values for monitoring of air pollution in the future.

Atmospheric dry deposition of polychlorinated dibenzo- p-dioxins and dibenzofurans in the vicinity of municipal solid waste incinerators

This study focuses on the atmospheric dry deposition flux of polychlorinated dibenzo- p-dioxins and dibenzofurans (PCDD/Fs) in the vicinity of the two municipal solid waste incinerators (MSWIs) located in southern Taiwan. PCDD/Fs in ambient air were taken and analyzed for seventeen 2,3,7,8-substituted PCDD/Fs during November 2004 and July 2005. Results show that the mean concentrations of PCDD/Fs in the ambient air near MSWI-GS and MSWI-RW were 0.090 and 0.097 pg I-TEQ/Nm 3, respectively. Dry deposition fluxes of total PCDD/Fs were 18.0 and 23.5 pg I-TEQ/(m 2 d) in the ambient air near MSWI-GS and MSWI-RW, respectively, which were considerably higher than that measured in Guangzhou, China. Annual dry deposition fluxes of total PCDD/Fs in the ambient air near MSWI-GS and MSWI-RW were 189 and 217 ng/(m 2 year), respectively, which were also much higher than dry deposition of total PCDD/Fs to the Atlantic Ocean. The results of the present study strongly suggest that exposure to PCDD/Fs in this area should be reduced. In addition, parametric sensitivity shows that dry deposition flux of PCDD/Fs is most sensitive to dry deposition velocity of the particle-phase, followed by air temperature and concentration of total suspended particulate but least sensitive to dry deposition velocity of the gas-phase.