Traditional and Novel Organophosphate Esters in Plastic Greenhouse: Occurrence, Multimedia Migration, and Exposure Risk via Vegetable Consumption.

The migration and risk of organophosphate esters (OPEs) in agricultural air-soil-plant multimedia systems due to plastic film application remain unclear. This study investigates the multimedia distribution of traditional OPEs (TOPEs), novel OPEs (NOPEs), and their transformation products (POPEs) in plastic and solar greenhouses. The total concentration of OPE-associated contaminants in air and airborne particles ranged from 594 to 1560 pg/m3 and 443 to 15600 ng/g, respectively. Significant correlations between air OPE concentrations and those in polyolefin film (P < 0.01) indicate plastic film as the primary source. Contaminants were also found in soils (96.8-9630 ng/g) and vegetables (197-7540 ng/g). The primary migration pathway for NOPEs was particle dry deposition onto the soil and leaf, followed by plant accumulation. Leaf absorption was the main uptake pathway for TOPEs and POPEs, influenced by vegetable specific leaf surface area. Moreover, total exposure to OPE-associated contaminants via vegetable intake was assessed at 2250 ng/kg bw/day for adults and 2900 ng/kg bw/day for children, with an acceptable hazard index. However, a high ecological risk was identified for NOPE compounds (median risk quotient, 975). This study provides the first evidence of the multimedia distribution and potential threat posed by OPE-associated contaminants in agricultural greenhouses.

Air-surface exchange of halomethoxybenzenes in a Swedish subarctic catchment.

Halomethoxybenzenes (HMBs) and related halomethoxyphenols are produced naturally in the marine and terrestrial environment and some also have anthropogenic origins. They are relatively volatile and water soluble and undergo atmospheric exchange with water bodies and soil. Here we report air-surface exchange of HMB compounds brominated anisoles and chlorinated dimethoxybenzenes in a Subarctic lake and catchment in Sweden during September 2022. HMBs were isolated from water on solid-phase extraction cartridges and from ground litter/soil by solvent extraction and determined by capillary gas chromatography - quadrupole mass spectrometry. Identified compounds in lake and stream water in the 10-100 pg L-1 range were 1,2,4,5-tetrachloro-3,6-dimethoxybenzene (DAME) > 2,4-dibromoanisole (DiBA) ≥ 2,4,6-tribromoanisole (TriBA) > 1,2,3,4-tetrachloro-5,6-dimethoxybenzene (tetrachloroveratrole, TeCV). DAME and the related compound 2,3,5,6-tetrachloro-4-methoxyphenol (DA) are reported in Subarctic litter/soil in the range 0.005-1.1 mg kg-1 dry weight (dw), whereas DiBA and TriBA were not detected in any litter/soil sample and TeCV in only one. Exchanges were assessed from concentrations in water and soil, air concentrations from a monitoring station at Pallas, Finland, and the physicochemical properties of the HMBs. Fluxes to and from the lake were estimated using the two-film gas exchange model. Net loadings (deposition minus volatilization) for the month of September were - 23, -15 and - 68 g for DiBA, TriBA and DAME, respectively, which amounted to about 4-7 % of the estimated lake inventory. An exchange assessment for DAME from litter/soil showed significant net volatilization at five sites, net deposition at one site and near-equilibrium at one site. The Torneträsk catchment appeared close to steady state with respect to HMB exchange during September 2022. The situation could be different during the warmer and colder seasons, and extending the study to cover these periods is a suggested next step.

Influence of oil extraction on concentration distributions, migration, secondary formation and carcinogenic risk of NPAHs and OPAHs in air and soil in an oilfield development area in China.

Oil extraction leads to environmental pollution from the oilfields and dweller activities, however, knowledge of the concentration distributions, migration, secondary formation and toxicity of nitrated/oxygenated polycyclic aromatic hydrocarbons (N/OPAHs) in oilfield regions is limited. In this research, atmospheric and soil samples in 7 different location types in an important oil industrial base in China were gathered. The ΣNPAHs and ΣOPAHs in the air ranged from 0.05 to 2.47 ng/m3 and 0.14-22.72 ng/m3, respectively, and in soil ranged from 0.22 to 17.81 ng/g and 9.69-66.86 ng/g, respectively. Both NPAHs and OPAHs in the atmosphere exhibited higher concentrations during winter. The atmospheric NPAH concentrations decreased exponentially with distance from urban area especially in the summer, revealing the impact of vehicles on the air in the Yellow River Delta area. High NPAH and OPAH concentrations were found only in soil near oil extraction facilities, indicating that the impact of oil extraction is limited to the soil near the extraction facilities. The air-soil exchanges of N/OPAHs were assessed through fugacity fraction analysis, and NPAHs were in the equilibrium-deposition state and OPAHs were in the net-deposition state in the winter. Higher incremental lifetime cancer risk (ILCR) occurred at the urban, industrial, and oilfield sites in the atmospheric samples, and the soil samples had the largest ILCR values in the oilfield sites. However, ILCR values for both air and soil did not exceed the threshold of 10-6.

Spatial distribution, environmental behavior, and health risk assessment of PAHs in soils at prototype coking plants in Shanxi, China: Stable carbon isotope and molecular composition analyses.

To investigate the environmental behavior of and carcinogenic risk posed by 16 priority-controlled polycyclic aromatic hydrocarbons (PAHs), soil samples and air samples from the coke oven top were collected in two prototype coking plants (named PF and JD). The PF soils contained more PAHs than the JD soils because the PF plant employed the side-charging technique and had a lower coke oven height. The soils from both plants contained enough PAHs to pose a carcinogenic risk, and this risk was higher in the PF plant. Data were collected on the source characteristic spectrum of stable carbon isotopic composition (δ13C) of PAHs emitted from the coke oven top (δ13C values of -36.02‰ to -32.05‰ for gaseous PAHs and -34.09‰ to -25.28‰ for particulate PAHs), and these data fill a research gap and may be referenced for isotopic-technology-based source apportionment. Diagnostic ratios and isotopic technology revealed that the coking plant soils were mainly influenced by the coking process, followed by vehicle exhaust; the soils near the boundary of each plant were slightly affected by C3 plant burning. For most PAHs [excluding fluoranthene, benzo(k)fluoranthene, indeno(1,2,3-c,d)pyrene, and dibenzo(a,h)anthracene], the dominant migration process was the net volatilization of PAHs from soil to air. In the PF plant, 13C was depleted in gaseous PAHs during volatilization.

Application of the multimedia fugacity model in predicting the environmental behaviors of PCBs: Based on field measurements and level III fugacity model simulation.

The comprehensive understanding of PCBs' fate has been impeded by the lack of simultaneous monitoring of PCBs in multiple environmental media in the background areas, which were considered long-term sinks for highly chlorinated PCBs. To address this gap, this study analyzed soils, willow tree barks, water, suspended particulate matter (SPM), and sediment samples collected from the middle reach of the Huaihe River in China for 27 PCBs. The results showed that the levels of ∑27PCBs in the soils were comparable to or lower than the background values worldwide. There were no significant correlations between organic matter and ∑27PCB concentrations in the soils and sediments. Additionally, the contamination of dioxin-like PCBs in the aquatic environment of the study area deserves more attention than in the soils. Applying the level III fugacity model to PCB 52, 77, 101, and 114 revealed that the soil was the primary reservoir, and air-soil exchange was the dominant intermedia transfer process, followed by air-water exchange. Furthermore, simulated results of air-soil and air-water diffusion were compared with those calculated from the field concentrations to predict the potential environmental behaviors of PCBs. Results indicated that the studied river would be a "secondary source" for PCB 52, 77, and 101. However, PCB 52, 77, 101, and 114 would continue to transfer from the air to the soil. This study combines multimedia field measurements and the fugacity model, providing a novel approach to predicting the potential environmental behaviors of PCBs.

Concentrations, phase exchanges and source apportionment of polycyclic aromatic hydrocarbons (PAHs) In Bursa-Turkey.

The present study aimed to determine the pollution levels derived from polycyclic aromatic hydrocarbons (PAHs) in air, plant and soil samples and to reveal the PAH exchange at the soil-air, soil-plant and plant-air interfaces. In this context, air and soil samples were collected in approximately 10-day periods between June 2021 and February 2022 from a semi-urban area in Bursa, an industrial city with a dense population. Also, plant branch samples were collected for the last three months. Total PAH concentrations in the atmosphere (∑16PAH) and soil (∑14PAH) ranged from 4.03 to 64.6 ng/m3 and 13-189.4 ng/g DM, respectively. PAH levels in the tree branches varied between 256.6 and 419.75 ng/g DM. In all air and soil samples, PAH levels were low in the summer and reached higher values in the winter. 3-ring PAHs were the dominant compounds, and their distribution in air and soil samples varied between 28.9%-71.9% and 22.8%-57.7%, respectively. According to the results of diagnostic ratios (DRs) and principal component analysis (PCA), both pyrolytic and petrogenic sources were found to be effective in PAH pollution in the sampling region. The fugacity fraction (ff) ratio and net flux (Fnet) values indicated that the direction of movement of PAHs was from soil to air. In order to better understand the PAH movement in the environment, soil-plant exchange calculations were also achieved. The ratio of ∑14PAH values measured to modeled concentrations (1.19

Spatial Distribution, Sources, Air-Soil Exchange, and Health Risks of Parent PAHs and Derivative-Alkylated PAHs in Different Functional Areas of an Oilfield Area in the Yellow River Delta, North China.

The knowledge of the spatial distribution, sources, and air-soil exchange of polycyclic aromatic compounds (PACs) in an oilfield area is essential to the development of effective control practices of PAC pollution. In this study, 48 passive air samples and 24 soil samples were collected during 2018-2019 in seven functional areas (e.g., urban, oil field, suburban, industrial, agricultural, near pump units, and background) in the Yellow River Delta (YRD) where the Shengli Oilfield is located, and 18 parent polycyclic aromatic hydrocarbons (PAHs) and five alkylated-PAHs (APAHs) were analyzed from all the air and soil samples. The ΣPAHs in the air and soil ranged from 2.26 to 135.83 ng/m3 and 33.96 to 408.94 ng/g, while the ΣAPAHs in the atmosphere and soil ranged from 0.04 to 16.31 ng/m3 and 6.39 to 211.86 ng/g, respectively. There was a downward trend of atmospheric ΣPAH concentrations with increasing the distance from the urban area, while both ΣPAH and ΣAPAH concentrations in the soil decreased with distance from the oilfield area. PMF analyses show that for atmospheric PACs, coal/biomass combustion was the main contributor in urban, suburban, and agricultural areas, while crude production and processing source contributes more in the industrial and oilfield area. For PACs in soil, densely populated areas (industrial, urban, and suburban) are more affected by traffic sources, while oilfield and near-pump unit areas are under the impact of oil spills. The fugacity fraction (ff) results indicated that the soil generally emitted low-molecular-weight PAHs and APAHs and act as a sink for high-molecular-weight PAHs. The incremental lifetime cancer risk (ILCR) of Σ(PAH+APAH) in both the air and soil, were below the threshold (≤10-6) set by the US EPA.

Air-soil exchange of and risks posed by short- and medium-chain chlorinated paraffins: Case study in a contaminated area in China.

Short-chain (SC) and medium-chain (MC) chlorinated paraffins (CPs) are found widely in the environment. Little research into air-soil exchange of SCCPs and MCCPs has been performed. In this study, CP concentrations, congener group profiles, and air-soil exchange in a typical contaminated area were investigated. A total of 10 soil samples and 10 air samples were collected from Zhoushan, an island in China. The samples were analyzed by two-dimensional gas chromatography electron capture negative ionization mass spectrometry. The SCCP and MCCP concentrations in the soil samples were 72-3842 and 117-8819 ng/g, respectively, and the SCCP and MCCP concentrations in the air samples were 57-208 and 1.8-25 ng/m3, respectively. The highest CP concentrations in both soil and air were found in samples from near shipyards, possibly because of CPs being emitted from metal cutting fluids and marine paints used at the shipyards. C14-15Cl7-9 were the dominant CP congener groups in the soil samples. C10Cl6-7 were the dominant CP congener groups in the air samples. Chlorinated decane and undecane and penta-, hexa-, and hepta-chlorinated CPs were enriched in the air relative to the soil. These congeners may have been released from the commercial CP-42 and CP-52. The fugacity fractions (ffs) of 48 homologs decreased as Koa increased. The ffs indicated that SCCPs and MCCPs dominated deposition. The net air-soil exchange fluxes of CPs were 201-769 ng/(m2·h). A preliminary risk assessment indicated that CPs pose low ecological risk except at sampling site S7 and do not pose significant health risks.

Spatial and seasonal variations of PAHs in soil, air, and atmospheric bulk deposition along the plain to mountain transect in Hubei province, central China: Air-soil exchange and long-range atmospheric transport.

Polycyclic aromatic hydrocarbons (PAHs) are a long-term environmental problem faced by human society. The sources of involuntary PAHs are complex, moreover, secondary emissions of fixed PAHs in the environment occur due to global change and disturbance of human activities. Samples of three environmental media including soil, air, and atmospheric bulk deposition were collected to observe the spatial distribution and seasonal variation, to discuss the source or sink of PAHs and their association with the air mass transport along the plain (Jianghan Plain, JHP) to mountain transect, and explore the geographic scope of the atmospheric transport influence. The results obtained showed that 16 individual PAHs generally existed in all environmental multimedia being studied, and the PAHs concentration in air, soil and deposition flux of atmospheric bulk was higher in JPH than in "Western Hubei Mountains" (WHMs). Considerably high PAHs concentrations were obtained from the soil, air and atmospheric bulk deposition in winter, summer, and both summer and winter, respectively. The air-soil fugacity fraction of PAHs indicated that the soil of Dajiuhu (DJH) is likely to be a sink. Backward air trajectory simulation confirmed that most of the air mass passes over the JHP before reaching DJH, combined with the (transport and persistence level III) TaPL3 model results JHP are acting as sources. However, seasonal changes lead to a shift in the roles of soil sources and sinks. The TaPL3 model calculated that PAHs are transported through water for a wider range of effects and a longer persistence, even up to 10 years.

Occurrence and air-soil exchange of organophosphate flame retardants in the air and soil of Dalian, China.

We investigated the concentrations, distributions, potential sources, and air-soil exchange of 10 OPFRs in the air and soil of Dalian. The concentrations of Σ10OPFRs in the soil were in the range of 1.07-288 ng/g (mean: 14.0 ng/g), while the concentrations of Σ10OPFRs in the passive air samples were in the range of 313-4760 pg/m3 (mean: 1630 pg/m3). Generally, the concentrations of OPFRs are relatively high in urban areas compared with those in suburban and rural areas, indicating the influence of intensive anthropogenic activities on local OPFR concentrations. Tris(2-chloroisopropyl) phosphate (TCIPP) was the most abundant congener, followed by tris(2-chloroethyl) phosphate (TCEP) and tri-n-butyl phosphate (TNBP). Spearman correlation analysis illustrated that OPFRs in the air shared common sources, while the sources of OPFRs in the soil were diverse. Net volatilization of TNBP from the soil to the air was observed at all sampling sites, whereas opposite trends were observed for TCIPP, TDCIPP, TBOEP, TPHP, EHDPP, TEHP, TPPO, and TMPP. The exchange trends of TCEP were characterized as volatilization in urban areas, but equilibrium in rural ones. TCEP showed the highest volatilization flux (1100 ng/m3/d), whereas TCIPP showed the highest deposition flux (-171 ng/m3/d). The significant diffusive fluxes of certain OPFRs, especially of those with suspected toxicities, suggested potential high exposure levels to these chemicals.

Atmospheric Concentrations and Air-Soil Exchange of Polycyclic Aromatic Hydrocarbons (PAHs) in Typical Urban-Rural Fringe of Wuhan-Ezhou Region, Central China.

During the summer of 2015, polycyclic aromatic hydrocarbons (PAHs) in the atmosphere were collected by passive air samplers in typical urban-rural fringe of Wuhan-Ezhou region, Central China. The results showed that 16 kinds of PAHs were ubiquitous with the concentrations of ∑16PAHs from 14.69 to 136.30 ng·m-3 and the mean concentration of 43.03 ng·m-3. Phenanthrene (Phe), fluoranthene (Fla) and pyrene (Pyr) were major components, which accounted for 81% of ∑16PAHs. PAHs atmospheric concentrations presented obvious spatial variation, being significantly related to geographical environment and influenced by anthropogenic activity. Air-soil exchange status of PAHs was discussed according to the fugacity fraction (ff). The results showed that HMW-PAHs behaved as net deposition, while LMW-PAHs were more likely to establish dynamic equilibrium between atmosphere and soil than MMW-PAHs and HMW-PAHs. For some PAHs, such as acenaphthylene (Acy) and anthracene (Ant), the soil acted as second sources of them.

Polycyclic aromatic hydrocarbons in the atmosphere and soils of Dalian, China: Source, urban-rural gradient, and air-soil exchange.

We investigated the concentrations, distributions, and sources of PAHs in the air and soils of Dalian, China, as well as their air-soil exchange trends. Total concentrations of PAHs in the air ranged from 6.37 to 124 ng/m3 with an average of 23.1 ± 26.6 ng/m3, while Σ15PAHs in the soils ranged from 42.8 to 28600 ng/g with an average of 2580 ± 5730 ng/g. Significant spatial distribution of PAHs was discovered in the soils with a clear urban-suburban-rural decreasing gradient, suggesting urban area is more contaminated by PAHs due to frequent and intensive human activities. However, high PAH concentrations were also discovered in the air from several rural sites, implying some PAH sources have shifted from urban to suburban or rural areas. Source apportionment indicated that major sources of PAHs in the urban and suburban soils were traffic emission/oil spill and coal combustion respectively, whereas major sources in the rural soils were diverse. Air-soil partitioning result suggested that 3-ring PAHs were mostly volatilized from soil, 6-ring PAHs were deposited into soil, while the trends of 4∼5-ring PAHs varied with sampling site. Fluoranthene, Pyrene, and Chrysene were mostly discovered to be volatilized in the urban and suburban areas, but equilibrium or deposited in the rural area, indicating a potential urban-to-rural transport of PAHs. The atmospheric transport and source shift of PAHs from urban to rural areas highlighted the importance of PAH source control on a regional scale.

Assessment of polychlorinated biphenyls (PCBs) in the Himalayan Riverine Network of Azad Jammu and Kashmir.

The emission of polychlorinated biphenyls (PCBs) in South Asian countries is one of the great environmental concerns and has resulted in the contamination of surrounding high altitude regions such as Azad Jammu and Kashmir (AJK), Pakistan. This first investigation of Polychlorinated Biphenyl (PCBs) concentrations in the ambient air, water and surface soil was conducted along the extensive stream network in the AJK valley of the Himalayan Region. In 2014, surface soil samples were taken and passive air and water samplers were deployed along the four main rivers, namely Jhelum, Neelum, Poonch and Kunhar, and analysed for PCBs (33 congeners) using GC-MS/MS. The ∑33PCBs concentrations ranged from 31.17 to 175.2 (mean ±â€¯SD: 81 ±â€¯46.4 pg/L), ND to 1908 (1054 ±â€¯588.5 pg/g), and 29.8 to 94.4 (52.9 ±â€¯22.7 pg/m3) in surface water, soil and air matrices, respectively. The levels of dioxin-like PCBs (∑8DL-PCBs) contributed considerably towards the total PCBs concentrations: 60.63% (water), 43.87% (air) and 13.76% (soil). The log transformed air-water fugacity (log fa/fw) ratios ranged from -9.37 to 2.58; with 86.3% of the sampling sites showing net volatilization of selected PCB congeners. Similarly, the fugacity fractions for air-soil exchange exhibited narrow variation (0.8 to < 1) indicating net volatilization of PCBs. The ecological risk assessment showed low potential ecological risks (Eri  = 1.58-7.63) associated with PCB contamination. The present findings provide baseline data that suggest cold trapping of POPs in the remote mountainous areas of Pakistan and can support environmental management of POPs at the regional level. This pioneer investigation campaign to assess the PCBs concentrations in Himalayan Riverine Network of Azad Jammu and Kashmir, Pakistan helps to develop baseline data of PCBs from the strategically important riverine environment that would help in future regional as well as global ecological studies. However, the effects of temperature variations on the sampling rates of chemicals across a wide spectrum of volatility along the elevation gradient were not taken under consideration for PCBs atmospheric concentrations.

Congener-specific composition of polychlorinated biphenyls (PCBs) in soil-air partitioning and the associated health risks.

The recent changes in the compositions of polychlorinated biphenyls (PCBs) after their restriction for 40 years may have various effects on human health. In order to characterize the congener-specific compositions of PCBs in the soil-air process and assess the associated human health risks, soil and air samples were simultaneously collected in winter and summer at two different functional locations. Homologue patterns suggest that long-range atmospheric transport might be the major source of soil and air residues of PCBs. The net deposition from air to soil was overwhelming for most PCB congeners. Variations in the occurrence and the homologue patterns of PCBs between the soil and air interface depended on chemical volatility, soil organic matter (OM) content, ambient temperature, topographical condition and atmospheric transport. Dioxin-like PCBs accounted for 11.0-70.3% and 2.31-54.8% of total PCB residues in soil and air, respectively. Non-carcinogenic and carcinogenic risks associated with exposure to soil and air PCBs were also estimated. Different PCB congeners showed different health effects, with the highest contribution from PCB-26. Additionally, the non-carcinogenic risk levels of PCBs were enhanced, while the carcinogenic risk levels decreased during the soil-air exchange process of PCBs with time. Our results highlight the soil-air interaction of PCBs in predicting their potential human exposure health risks.

Spatio-temporal variations of atmospheric and soil polybrominated diphenyl ethers (PBDEs) in highly industrialized region of Dilovasi.

Polybrominated diphenyl ethers (PBDEs) were investigated in ambient air of a highly industrialized region at 23 different sampling sites for 12 months. Total concentrations of 8 PBDE congeners (Σ8PBDE) were found to be between 5.73 and 520 pg m-3 (94.7 ±â€¯78.9; average ±â€¯SD) and BDE-209 was the predominant congener, followed by BDE-47 and/or BDE-99. Their contributions to Σ8PBDE were 71 ±â€¯13, 9 ±â€¯4% and 8 ±â€¯4%; respectively. Compared to previous studies around the world, high concentrations detected in Dilovasi demonstrated the severity of atmospheric PBDE pollution in the area. For all sampling sites, average PBDE concentration obtained in summer (118.5 ±â€¯98.7 pg m-3) was higher than one found in winter period (79.7 ±â€¯59.1 pg m-3) and this seasonal difference was more obvious in industrial/urban sites (p < 0.05), probably due to enhanced volatilization from ongoing PBDE sources such as waste incineration and iron-steel plants. The soil-air exchange tendencies of PBDEs did not show substantial differences between the sampling periods with small variations for each congener. All congeners either tend to deposit to soil or to be within the equilibrium range for all seasons. This reflects the impact of local ongoing sources rather than temperature on the direction of soil-air exchange of PBDEs in this region. Specific congener ratios such as BDE-47/-99 and -99/-100 confirmed the impact of local sources rather than long-range transport on PBDE congeners in the study area. According to the Positive Matrix Factorization (PMF) results, the BDE-209 content of the first factor was found to be 91.7% and this factor was attributed to the deca-BDE technical formulations. The second factor was highly rich with both BDE-183 (%61) and BDE-28 (%52) and identified as octa-BDE technical products. The last factor was highly loaded with BDE-99, BDE-47, BDE-100, BDE-154 and BDE-153 and has been determined as the penta-BDE commercial formulations.

Factors influencing the ecological and human health risks of DDTs in soils and air at the isomeric and enantiomeric levels.

Even though the application of dichlorodiphenyltrichloroethanes (DDTs) has been restricted for over 30 years, their ubiquitous existence still poses profound adverse impacts on ecosystem and human health. In this study, simultaneous soil and air sampling campaigns at different functional areas were conducted in warm and cold seasons. Based on the residue levels and enantiomeric signatures of DDT and its metabolites in soils and air, the parameters influencing ecological and human health risks were explored. ΣDDT concentrations in soils correlated positively with organic matter (OM) and negatively with pH, whereas atmospheric DDT levels were primarily facilitated by increased temperature. High temperature and low soil pH were also favorable for the transformation of DDT into its metabolites. The inhabitants living in agricultural regions or in areas with higher soil OM or pH < 7 were exposed to higher existing and potential health risks of soil DDTs. In addition, at lower temperatures, the existing and potential carcinogenic risks of DDTs from soil exposure were higher, whereas risks from air inhalation were lower. Health risks would be increased when considering the enantioselective toxicity of o,p'-DDT and o,p'-DDD. The results from this study could provide baseline support for risk control and avoidance of DDTs.

Seasonal soil/snow-air exchange of semivolatile organic pollutants at a coastal arctic site (Tromsø, 69°N).

Soils are a major reservoir of semivolatile organic pollutants such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), and exert a control on their atmospheric occurrence. We present here an assessment of the atmospheric occurrence and seasonality of soil/snow-air partitioning and exchange of PCBs, PAHs, hexachlorobenzene (HCB), and hexachlorocyclohexanes (HCHs) in the arctic city Tromsø, northern Norway. The fugacities of the organic pollutants in soils and snow were determined using a soil fugacity sampler by equilibrating the air concentrations with those in the surface soil/snow. The concentrations in soils did not show a significant seasonality. Conversely, the ambient air concentrations and the soil (or snow) fugacity showed a clear seasonality for PCBs, HCH, HCB and some PAHs, related to temperature. Fugacities in soil/snow were correlated with those in the ambient gas phase, suggesting a close seasonal air-soil/snow coupling. Generally, there was a net deposition or close to equilibrium conditions during the winter, which contrasts with the net volatilization observed during the warmer periods. The chemicals with lower octanol-air partition coefficients showed a larger tendency for being volatilized and thus remobilized from this coastal arctic environment. Conversely, the more hydrophobic compounds were close to air-soil/snow equilibrium or showed a net deposition.

Structural equation modeling of PAHs in ambient air, dust fall, soil, and cabbage in vegetable bases of Northern China.

A series of field samples including ambient air (gaseous and particulate phases), dust fall, surface soil, rhizosphere soil and cabbage tissues (leaf, root and core), were collected in vegetable bases near a large coking manufacturer in Shanxi Province, Northern China, during a harvest season. A factor analysis was employed to apportion the emission sources of polycyclic aromatic hydrocarbons (PAHs), and the statistical results indicated coal combustion was the dominant emission source that accounted for different environmental media and cabbage tissues, while road traffic, biomass burning and the coking industry contributed to a lesser extent. A structural equation model was first developed to quantitatively explore the transport pathways of PAHs from surrounding media to cabbage tissues. The modeling results showed that PAHs in ambient air were positively associated with those in dust fall, and a close relationship was also true for PAHs in dust fall and in surface soil due to air-soil exchange process. Furthermore, PAHs in surface soil were correlated with those in rhizosphere soil and in the cabbage leaf with the path coefficients of 0.83 and 0.39, respectively. PAHs in the cabbage leaf may dominantly contribute to the accumulation of PAHs in the edible part of cabbages.

Distribution, sources, and air-soil exchange of OCPs, PCBs and PAHs in urban soils of Nepal.

Due to the high temperature and extensive use of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), tropical cities could act as secondary sources of these pollutants and therefore received global concern. As compared with other tropical cities, studies on the air-soil exchange of OCPs, PCBs and PAHs in tropical Nepali cities remained limited. In the present study, 39 soil samples from Kathmandu (capital of Nepal) and 21 soil samples from Pokhara (second largest city in Nepal) were collected The soil concentrations of the sum of endosulfans (α- and ß-endosulfans) ranged from 0.01 to 16.4 ng/g dw. Meanwhile, ∑dichlorodiphenyltrichloroethane (DDTs) ranged from 0.01 to 6.5 ng/g dw; ∑6PCBs from 0.01 to 9.7 ng/g dw; and ∑15PAHs from 17.1 to 6219 ng/g dw. High concentrations of OCPs were found in the soil of commercial land, while, high soil PAH concentrations were found on tourist/religious and commercial land. Combined the published air concentrations, and the soil data of this study, the directions and fluxes of air-soil exchange were estimated using a fugacity model. It is clear that Nepal is a country contributing prominently to secondary emissions of endosulfans, hexachlorobenzene (HCB), and low molecular weight (LMW) PCBs and PAHs. The flux for all the pollutants in Kathmandu, with ∑endosulfans up to 3553; HCB up to 5263; and ∑LMW-PAHs up to 24378 ng m-2 h-1, were higher than those in Pokhara. These high flux values indicated the high strength of Nepali soils to act as a source.

Occurrence and air-soil exchange of organochlorine pesticides and polychlorinated biphenyls at a CAWNET background site in central China: Implications for influencing factors and fate.

Ambient air and soil samples were collected between March 2012 and March 2013 at Jinsha, a regional background site in central China, to measure the concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). The average concentrations of total OCPs and total PCBs were 191 ± 107 and 39.4 ± 27.1 pg/m3 in air (gaseous and particulate phase) and 0.585 ± 0.437 and 0.083 ± 0.039 ng/g in soil, respectively. The higher concentrations of p,p'-dichlorodiphenyltrichloroethane (p,p'-DDT) and p,p'-DDT/p,p'-DDE ratios in the soil indicated recent p,p'-DDT input to the soil. A strong positive temperature dependence and average fugacity fraction value > 0.5 were observed for p,p'-DDT, suggesting that volatilization of residual DDT in the soil was the main influencing factor on atmospheric p,p'-DDT. Highly average fugacity fractions (>0.7) of trans-chlordane (TC) and cis-chlordane (CC) and high TC/CC ratios both in the soil and atmosphere suggested fresh inputs. Higher gaseous concentrations of hexachlorobenzene (HCB) were observed in winter and negative temperature dependence was directly attributed to the surrounding ongoing source (e.g. fuel consuming activities), especially in winter. Overall, most targeted OCPs and PCBs were influenced by long-range transport, and fugacity fraction values indicated highly volatile compounds (e.g. α-hexachlorocyclohexane (α-HCH) and lower chlorinated PCBs) were volatilized and low volatility compounds (e.g. p,p'-DDE and higher chlorinated PCBs) were deposited at the air-soil interface. Knowing the source and sink of OCPs and PCBs can help to control their pollution in this area and provide a reference for other studies.