Diurnal Variations of Air-Soil Exchange of Semivolatile Organic Compounds (PAHs, PCBs, OCPs, and PBDEs) in a Central European Receptor Area

Cross-media transfer of polycyclic aromatic hydrocarbons in the Naples metropolitan area, southern Italy

At present, an in-depth knowledge of polycyclic aromatic hydrocarbons (PAHs) in the multimedia system of the urban environment remains limited. Taking the Naples metropolitan area (NMA) for instance, we simulated the cross-media transfer of PAHs using a multimedia urban model, involving air, water, soil, sediment, vegetation, and impervious film. The results indicated that the predicted PAH values in 2015 match well with their corresponding in-situ monitoring data. The PAH emission inventory and the simulated mass in various media all showed a downward trend from 2015 to 2020 due to national energy conservation policies and Corona Virus Disease 2019. The simulated mass of PAHs in the soil and sediment phases was 896.8 and 232.7 kg in 2020, respectively, contributing together to 96.7% of PAHs in the NMA. And they were identified as the greatest sinks for PAHs, and exhibited the longest retention duration, with values of PAH persistence reaching approximately 548.8 - 2,0642.3 hours. The results of transfer fluxes indicated that local emissions and atmospheric advection were the primary routes affecting the distribution of PAHs. The sensitivity analysis indicated that atmospheric advection rate was the most critical parameter for air, soil, vegetation, and film, whereas water concentration and sediment degradation rate were vital for water and sediment, respectively. This study offered valuable insights into how human activity contributes to the status and fate of PAHs in the urban environment.

Air-plant interaction and air-soil exchange of polycyclic aromatic hydrocarbons in a large human-influenced reservoir in southwest China

The Three Gorges Reservoir (TGR) is totally manmade, strongly influenced by anthropogenic activity, and lies on the upper reaches of Yangtze River. The periodic storage and discharge of water from the Three Gorges Dam could have altered the original air-plant/soil interactions of contaminants in TGR. Herein, paired atmospheric gas-particle, air-plant, and air-soil samples were collected to investigate the air-plant interaction and air-soil exchange of 16 USEPA priority polycyclic aromatic hydrocarbons (PAHs). The air-plant interaction based on McLachlan's framework to our datasets suggests that PAHs were absorbed via gaseous deposition that was restricted by the plant-gas dynamic equilibrium. The equilibrium indicates a dynamic balance between the gaseous phase and plant surface in PAH absorption. The main limiting factor influencing the PAH uptake was the plant species rather than the atmospheric PAH concentration. The air-soil exchange of PAHs exhibited a net volatilization flux of 16.71 ng/m2/d from the soil to the air based on annual average. There was more volatilization and less deposition in summer and more deposition and less volatilization in autumn and winter. The soil serves as a secondary source of atmospheric PAHs. As the first attempt on probing the multi-interface geochemical process of PAHs, this study highlights the influence of manual water level manipulation from the TGD and environmental factors (such as temperature, humidity, and soil properties) on the regional fate of PAHs in the TGR.

Organochlorine pesticide contamination of soils and dust from an urban environment in the Niger Delta of Nigeria

The concentrations, sources, and risk of twenty organochlorine pesticides (OCPs) in soils and dusts from a typical urban setting in the Niger Delta of Nigeria were examined. The Σ20 OCP concentrations (ng g-1) varied from 4.49 to 150 with an average value of 32.6 for soil, 4.67 to 21.5 with an average of 11.7 for indoor dust, and 1.6 to 96.7 with an average value of 23.5 for outdoor dust. The Σ20 OCP concentrations in these media were in the order: soil > outdoor dust > indoor dust, which was in contrast with the order of the detection frequency, i.e., indoor dust (95 to 100 %) > soil (60 to 90 %) > outdoor dust (30 to 80 %). The concentrations of the different OCP classes in these media followed the order: aldrin + dieldrin + endrin and its isomers (Drins) > chlordanes > dichlorodiphenyltrichloroethane (DDTs) > hexachlorocyclohexane (HCHs) > endosulfans for outdoor dust and soil, while that of the indoor dust followed the order: Drins > chlordanes > endosulfans > DDTs > HCHs. The cancer risk values for human exposure to OCPs in these sites exceeded 10-6 which indicates possible carcinogenic risks. The sources of OCPs in these media reflected both past use and recent inputs.

Associations of exposure to organochlorine pesticides and polychlorinated biphenyls with chronic kidney disease among adults: the modifying effects of lifestyle

Exposure to organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) has been reported to be associated with renal impairment and chronic kidney disease (CKD). Nevertheless, the research results thus far have exhibited inconsistency, and the effect of lifestyle on their association is not clear. In this study, we assessed the correlation between serum OCPs/PCBs and CKD and renal function indicators including estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) among 1721 Chinese adults. In order to further investigate the potential impact of lifestyle, we conducted joint associations of lifestyle and OCPs/PCBs on CKD. We found a negative correlation between p,p'-DDE and eGFR, while logistic regression results showed a positive correlation between PCB-153 and CKD (OR, 1.92; 95% CI, 1.21, 3.06). Quantile g-computation regression analyses showed that the association between co-exposure to OCPs/PCBs and CKD was not significant, but p,p'-DDE and PCB-153 were the main contributors to the negative and positive co-exposure effects of eGFR and CKD, respectively, which is consistent with the regression results. Participants with both relatively high PCB-153 exposure and an unhealthy lifestyle had the highest risk of CKD, in the joint association analysis. The observed associations were generally supported by the FAS-eGFR method. Our research findings suggest that exposure to OCPs/PCBs may be associated with decreased eGFR and increased prevalence of CKD in humans, and a healthy lifestyle can to some extent alleviate the adverse association between PCB-153 exposure and CKD.

Environmental factors influencing the soil-air partitioning of semi-volatile petroleum hydrocarbons: Laboratory measurements and optimization model

The soil-air partition coefficient (KSA) values are commonly utilized to examine the fate of organic contaminants in soils; however, their measurement has been lacking for semi-volatile petroleum hydrocarbons within soil contaminated by crude oil. This research utilized a solid-phase fugacity meter to determine the KSA values of n-alkanes and polycyclic aromatic hydrocarbons (PAHs) under crucial environmental conditions. The results showed a notable increase in KSA values with the extent of crude oil contamination in soil. Specifically, in the 3 % crude oil treatment, the KSA values for n-alkanes and PAHs increased by 1.16 and 0.66 times, respectively, compared to the 1 % crude oil treatment. However, the KSA values decreased with changes in temperature, water content, and particle size within the specified experimental range. Among these factors, temperature played a significant role. The KSA values for n-alkanes and PAHs decreased by 0.27-0.89 and 0.61-0.83 times, respectively, with a temperature increase from 5 °C to 35 °C. Moreover, the research identified that the molecular weight of n-alkanes and PAHs contributed to variations in KSA values under identical environmental factors. With an increase in temperature from 5 °C to 35 °C, the range of n-alkanes present in the air phase expanded from C11 to C34, and PAHs showed elevated levels of acenaphthene (ACE) and benzo (b) fluoranthene (BbFA). Furthermore, heightened water content and particle size were observed to facilitate the volatilization of low molecular weight petroleum hydrocarbons. The effect of environmental variables on soil-air partitioning was evaluated using the Box-Behnken design (BBD) model, resulting in the attainment of the lowest log KSA values. These results illustrate that soil-air partitioning is a complex process influenced by various factors. In conclusion, this study improves our comprehension and predictive capabilities concerning the behavior and fate of n-alkanes and PAHs within soil-air systems.

Characteristics of typical intermediate and semi volatile organic compounds in Shanghai during China International Import Expo event

To ensure good air quality during the China International Import Expo (CIIE) event, stringent emission-reduction measures were implemented in Shanghai. To assess the efficacy of these measures, this study measured typical categories of intermediate/semi volatile organic compounds (I/SVOCs), including alkanes (C10-C26 n-alkanes and pristane), EPA-priority polycyclic aromatic hydrocarbons (PAHs), alkylnaphthalenes, benzothiazole (BTH) and chlorobenzenes (CBs), at an urban site of Shanghai before and during two CIIE events (2019 and 2020; non-CIIE versus CIIE). The average concentrations of alkanes and PAHs during both 2019 and 2020 CIIE events decreased by approximately 41% and 17%, respectively, compared to non-CIIE periods. However, the decline in BTH and CBs was only observed during CIIE-2019. Secondary organic aerosol (SOA) formation from alkanes, PAHs and BTH was evaluated under atmospheric conditions, revealing considerable SOA contributions from dimethylnaphthalenes and BTH. Positive matrix factorization (PMF) analysis further revealed that life-related sources, such as cooking and residential emissions, make a noticeable contribution (21.6%) in addition to the commonly concerned gasoline-vehicle sources (31.5%), diesel-related emissions (20.8%), industrial emissions (18.6%) and ship emissions (7.5%). These findings provide valuable insights into the efficacy of the implemented measures in reducing atmospheric I/SVOCs levels. Moreover, our results highlight the significance of exploring additional individual species of I/SVOCs and life-related sources for further research and policy development.

Assessing pesticides in the atmosphere: A global study on pollution, human health effects, monitoring network and regulatory performance

Pesticides are widely used in agriculture, but their impact on the environment and human health is a major concern. While much attention has been given to their presence in soil, water, and food, there have been few studies on airborne pesticide pollution on a global scale. This study aimed to assess the extent of atmospheric pesticide pollution in countries worldwide and identify regional differences using a scoring approach. In addition to analyzing the health risks associated with pesticide pollution, we also examined agricultural practices and current air quality standards for pesticides in these countries. The pollution scores varied significantly among the countries, particularly in Europe. Asian and Oceanic countries generally had higher scores compared to those in the Americas, suggesting a relatively higher level of air pollution caused by pesticides in these regions. It is worth noting that the current pollution levels, as assessed theoretically, pose minimal health risks to humans. However, studies in the literature have shown that excessive exposure to pesticides present in the atmosphere has been associated with various health problems, such as cancer, neuropsychiatric disorders, and other chronic diseases. Interestingly, European countries had the highest overall pesticide application intensities, but this did not necessarily correspond to higher atmospheric pesticide pollution scores. Only a few countries have established air quality standards specifically for pesticides. Furthermore, pollution scores across states in the USA were investigated and the global sampling sites were mapped. The findings revealed that the scores varied widely in the USA and the current sampling sites were limited or unevenly distributed in some countries, particularly the Nordic countries. These findings can help global relevant environmental agencies to set up comprehensive monitoring networks. Overall, the present research highlights the need to create a pesticide monitoring system and increase efforts to enhance pesticide regulation, ensure consistency in standards, and promote international cooperation.

Air-soil cycling of oxygenated, nitrated and parent polycyclic aromatic hydrocarbons in source and receptor areas

Polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives, OPAHs and NPAHs, are semivolatile air pollutants which are distributed and cycling regionally. Subsequent to atmospheric deposition to and accumulation in soils they may re-volatilise, a secondary source which is understudied. We studied the direction of air-soil mass exchange fluxes of 12 OPAHs, 17 NPAHs, 25 PAHs and one alkylated PAH in two rural environments being influenced by the pollutant concentrations in soil and air, by season, and by land cover. The OPAHs and NPAHs in samples of topsoil, of ambient air particulate and gas phases and in the gas-phase equilibrated with soil were analysed by GC-APCI-MS/MS. The pollutants soil burdens show a pronounced seasonality, a winter maximum for NPAHs and PAHs and a summer maximum for OPAHs. One order of magnitude more OPAH and parent PAH are found stored in forest soil than in nearby grassland soil. Among a number of 3-4 ring PAHs, the OPAHs benzanthrone and 6H-benzo(c,d)pyren-6-one, and the NPAHs 1- and 2-nitronaphthalene, 9-nitrophenanthrene and 7-nitrobenz(a)anthracene are found to re-volatilise from soils at a rural background site in central Europe in summer. At a receptor site in northern Europe, net deposition of polycyclic aromatic compounds (PACs) prevails and re-volatilisation occurs only sporadic. Re-volatilisation of a number of PACs, including strong mutagens, from soils in summer and even in winter indicates that long-range atmospheric transport of primary PAC emissions from central Europe to receptor areas might be enhanced by secondary emissions from soils.

Use of machine learning to identify key factors regulating volatilization of semi-volatile organic chemicals from soil to air

Volatilization from soil to air is a key process driving the distribution and fate of semi-volatile organic contaminants. However, quantifying this process and the key environmental governing factors remains difficult. To address this issue, the volatilization fluxes of polybrominated diphenyl ethers (PBDEs) and organophosphate esters (OPEs) from soil were determined in 16 batch experiments orthogonally with six variables (chemical property, soil concentration, air velocity, ambient temperature, soil porosity, and soil moisture) and analyzed with machine learning methods. The results showed that gradient-boosting regression tree models satisfactorily predicted the volatilization fluxes of PBDEs (r2 = 0.82 ± 0.07) and OPEs (r2 = 0.62 ± 0.13). Permutation importance analysis showed that partitioning potential of chemicals between soil and air was the most important factor regulating the volatilization of the target compounds from soil. Temperature and soil porosity played a secondary role in controlling the migration of PBDEs and OPEs, respectively, due to higher volatilization enthalpies of PBDEs than those of OPEs and dominant adsorption of OPEs on mineral surface. The effect of soil moisture was negative and positive for the volatilization fluxes of PBDEs and OPEs, respectively. These results suggested different responses in the soil-air diffusive transport of PBDEs and OPEs to high temperature and rainstorm induced by climate change.

Full life cycle and sustainability transitions of phthalates in landfill: A review

Phthalates (PAEs) are added to various products as a plasticizer. As these products age and are disposed of, plastic waste containing PAEs enters the landfill. The landfill environment is complicated and can be regarded as a "black box". Also, PAEs do not bind with the polymer matrix. Therefore, when a series of physical chemistry and biological reactions occur during the stabilization of landfills, PAEs leach from waste and migrate to the surrounding environmental media, thereby contaminating the surrounding soil, water ecosystems, and atmosphere. Although research on PAEs has achieved progress over the years, they are mainly concentrated on a particular aspect of PAEs in the landfill; there are fewer inquiries on the life cycle of PAEs. In this study, we review the presence of PAEs in the landfill in the following aspects: (1) the main source of PAEs in landfills; (2) the impact of the landfill environment on PAE migration and conversion; (3) distribution and transmedia migration of PAEs in aquatic ecosystems, soils, and atmosphere; and (4) PAE management and control in the landfill and future research direction. The purpose is to track the life cycle of PAEs in landfills, provide scientific basis for in-depth understanding of the migration and transformation of PAEs and environmental pollution control in landfills, and new ideas for the sustainable utilization of landfills.

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.

Inventory, source and health risk assessment of nitrated and parent PAHs in agricultural soils over a rural river in Southeast China

Nitrated polycyclic aromatic hydrocarbons (NPAHs) have become a concerning topic because of their widespread occurrence and carcinogenicity. However, studies on NPAHs in soils, especially in agricultural soils, are still limited. In this study, a systematic monitoring campaign of 15 NPAHs and 16 polycyclic aromatic hydrocarbons (PAHs) was performed in agricultural soils from the Taige Canal basin in 2018, which is a typical agricultural activity area of the Yangtze River Delta. The total concentration of NPAHs and PAHs ranged from 14.4 to 85.5 ng g^-1 and 118-1108 ng g^-1, respectively. Among the target analytes, 1,8-dinitropyrene and fluoranthene were the most predominant congeners accounting for 35.0% of ∑₁₅NPAHs and 17.2% of ∑₁₆PAHs, respectively. Four-ring NPAHs and PAHs were predominant, followed by three-ring NPAHs and PAHs. NPAHs and PAHs had a similar spatial distribution pattern with high concentrations in the northeastern Taige Canal basin. The soil mass inventory of ∑₁₆PAHs and ∑₁₅NPAHs was evaluated to be 31.7 and 2.55 metric tons, respectively. Total organic carbon had a significant impact on the distribution of PAHs in soils. The correlation between PAH congeners in agricultural soils was higher than that between NPAH congeners. Based on diagnostic ratios and principal component analysis-multiple linear regression model, vehicle exhaust emission, coal combustion, and biomass combustion were the predominant sources of these NPAHs and PAHs. According to the lifetime incremental carcinogenic risk model, the health risk posed by NPAHs and PAHs in agricultural soils of the Taige Canal basin was virtually negligible. The total health risk in soils of the Taige Canal basin to adults was slightly higher than that to children.

The soil-air exchange of OCPs and PCBs in the Tibetan Plateau: Emphasis on episodic transport of unintentionally produced PCBs

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in paired ambient and surface air fugacity samples were measured in the Tibetan Plateau (TP) from 2019 to 2022. The air concentrations of previously intentionally produced chemicals like dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) declined. Their soil-air exchange direction ranged from equilibrium to volatilization, suggesting that the TP is acting as a secondary source of most OCPs and PCBs with the pollution alleviation. However, considerably high atmospheric levels of PCB-11, an indicator of unintentionally produced PCBs (UP-PCBs), were recorded in the southern TP. Strong episodic long-range atmospheric transport (LRAT) and deposition of PCB-11 events took place mostly in summer. Those events associated with winds from potential sources and less rainfall interception along the air mass transport routes accounted for a significant fraction of overall atmospheric deposition in the TP. Meanwhile, cryoturbation and plowing are suspected to be important factors contributing to the reemission of PCB-11 from surface soil. The high abundance of PCB-11 and strong deposition/evaporation events highlights potential environmental and health risks of UP-POPs in the TP.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in agricultural and dumpsite soils in Sierra Leone

This study investigates the concentration and distribution of polycyclic aromatic hydrocarbons (PAHs) in soils, potential sources, risk assessment, and soil physicochemical properties influencing PAH distribution in developed and remote cities in Sierra Leone. Seventeen topsoil samples (0-20 cm) were collected and analyzed for 16 PAHs. The average concentrations of Σ₁₆PAH in soils in the surveyed areas were 1142 ng g^-1 dw, 265 ng g^-1 dw, 79.7 ng g^-1 dw, 54.3 ng g^-1 dw, 54.2 ng g^-1 dw, 52.3 ng g^-1 dw, and 36.6 ng g^-1 dw in Kingtom, Waterloo, Magburaka, Bonganema, Kabala, Sinikoro, and Makeni, respectively. Based on the European soil quality guidelines, Kingtom and Waterloo soils were categorized as heavily and weakly contaminated soil PAHs respectively. The main PAH compounds of this study were 2-ring, 4-ring, and 5-ring PAHs. High molecular weight PAHs (4-6 rings) made up 62.5% of the total PAHs, while low molecular weight PAHs (2-3 rings) was 37.5%. In general, HMWPAHs were predominant in Kingtom, followed by Waterloo. The appointment of PAH sources using different methods revealed mixed sources, but predominantly pyrogenic sources (petroleum, biomass, coal, and fossil fuel contributions). Soil pH has a significant impact on PAH distribution. The toxicity equivalent quantity (TEQ_BaP) levels in soils pose a potential health risk to residents in developed cities but pose a negligible health risk to residents in remote cities. This study is significant as its findings reveal the status of PAH soil contamination in Sierra Leone. The results have important implications for policymakers and stakeholders to identify high-risk zones and establish proper environmental monitoring programs, pollution control measures, and remediation strategies to prevent future risks.

Level and risk assessment of selected polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and organochlorine pesticides in walnut and soil

It is unknown how hydrophobic organic contaminants (HOCs) are distributed and how they affect the environment in high-fat nuts and their planted soil. The profile of HOCs in walnut/soil system was investigated in this study. Polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs) were found in walnuts at concentrations of 0.67, 127, and 116 μg/kg, respectively. The target hazard quotients (THQ) of 17 PCBs, 16 PAHs, and 21 OCPs from walnut consumption by human were 0.06, 0.01, and 0.11, respectively. The highest concentrations of HOC in the soil were found in Nap and toxaphene, with concentrations of 2580 and 902 μg/kg, respectively. Bioaccumulation factors (BAF) and biota-sediment accumulation factors (BSAF) in walnuts were ranged from <0.01 to 7.04 and <0.01 to 3.83, respectively. Concentrations of most individual HOCs in soil samples were significantly correlated with soil organic matter (SOM) (p < 0.01) and minerals (p < 0.01), with maximum correlation coefficients of 0.70 (OM-PCB81) and -0.84 (P-BaP). According to this study, high-fat walnuts do not have a high bioaccumulation of HOCs from soil, and the risk of consumption is within the safe range.

Environmental fate and effects of PAHs in tropical mariculture ponds near the northern South China Sea: Rainfall plays a key role

The behavior and fate of PAHs are affected by multiple meteorological factors, but the main factors driving PAHs in tropical mariculture areas are still not clearly understood. This study continuously monitored PAHs in a few tropical land-based mariculture ponds, discussed their dynamic change trend, migration among the multiple media, and the relevant affected factors. Results indicated that PAHs were widely distributed in these environmental media, and the PAHs' concentration showed an obvious attenuation trend in the mariculture cycle. Wet deposition brought overwhelming majority atmospheric PAHs (92 % ± 5.7 %) to the aqueous system, and >72 % of these PAHs came from oil combustion-related sources and biomass combustion. Compared with the natural sea areas in the same region, mariculture ponds sediment could be changed from a sink at the early stage to a secondary release source of PAHs at the late stage of the rainy season, which intensifies the bioaccumulation of PAHs and the risk of edible carcinogenesis of aquatic products. Our research revealed that rainfall drove the occurrence and environmental behavior of PAHs in the tropical mariculture areas, while land-based mariculture ponds ecosystem affected the regional environmental fate of PAHs and weakened their transmission to the marine environment from land.

Spatial origin analysis on atmospheric bulk deposition of polycyclic aromatic hydrocarbons in Shanghai

Atmospheric deposition of polycyclic aromatic hydrocarbons (PAHs) onto soil threatens terrestrial ecosystem. To locate potential source areas geographically, a total of 139 atmospheric bulk deposition samples were collected during 2012-2019 at eight sites in Shanghai and its surrounding areas. A multisite joint location method was developed for the first time to locate potential source areas of atmospheric PAHs based on an enhanced three dimensional concentration weighted trajectory model. The method considered spatial and temporal variations of atmospheric boundary layer height and homogenized all results over the eight sites via geometric mean. Regional transport was an important contributor of PAH atmospheric deposition while massive local emissions may disturb the identification of potential source areas. Northwesterly winds were associated with elevated deposition fluxes. Potential source areas were identified by the multisite joint location method and included Hebei, Tianjin, Shandong and Jiangsu to the north, and Anhui to the west of Shanghai. PM and SO₂ data from the national ground monitoring stations confirmed the identified source areas of deposited PAHs in Shanghai.

Human Exposure to Pesticides in Dust from Two Agricultural Sites in South Africa

Over the last decades, concern has arisen worldwide about the negative impacts of pesticides on the environment and human health. Exposure via dust ingestion is important for many chemicals but poorly characterized for pesticides, particularly in Africa. We investigated the spatial and temporal variations of 30 pesticides in dust and estimated the human exposure via dust ingestion, which was compared to inhalation and soil ingestion. Indoor dust samples were collected from thirty-eight households and two schools located in two agricultural regions in South Africa and were analyzed using high-performance liquid chromatography coupled to tandem mass spectrometry. We found 10 pesticides in dust, with chlorpyrifos, terbuthylazine, carbaryl, diazinon, carbendazim, and tebuconazole quantified in >50% of the samples. Over seven days, no significant temporal variations in the dust levels of individual pesticides were found. Significant spatial variations were observed for some pesticides, highlighting the importance of proximity to agricultural fields or of indoor pesticide use. For five out of the nineteen pesticides quantified in dust, air, or soil (i.e., carbendazim, chlorpyrifos, diazinon, diuron and propiconazole), human intake via dust ingestion was important (>10%) compared to inhalation or soil ingestion. Dust ingestion should therefore be considered in future human exposure assessment to pesticides.

Source, occurrence and risks of twenty antibiotics in vegetables and soils from facility agriculture through fixed-point monitoring and numerical simulation

In this study, a universal method that combined fixed-point monitoring and numerical simulation was used to understand the source, fate and risks of antibiotics in environment. Results showed that the antibiotic concentration in vegetables, soil and manure from 53 fixed-point monitoring sampling sites were ND-18.47, ND-1438.50 and ND-24710.00 μg kg^-1, respectively. There were positive correlations between the antibiotic concentrations of vegetables and soil as well as between soil and manure. The average Amount_soil/manure values were 1.48-46.02, indicating that antibiotics built up pseudo persistent residues in soil due to repeated fertilization. The modified level-III fugacity model showed that tetracyclines and fluoroquinolones tend to remain in soil given their sorption and mobility, while sulfonamides were highly distributed in plants, especially in leaves. Norfloxacin, ofloxacin, sulfadiazine, sulfamethoxazole and sulfisoxazole were found to be risk factors in facility agriculture and should be continuously monitored during agricultural production. Most importantly, we used the inversion method to determine the recommended maximum residue limits of antibiotics in soil. This will not only allow for better control of the amount of the antibiotics in the environment, but also act as a potential method to assess the risks of pollutants without maximum residue limits in the environment.

Comprehensive Multi-compartment Sampling for Quantification of Long-Term Accumulation of PAHs in Soils

Long-term accumulation in the soils of ubiquitous organic pollutants such as many polycyclic aromatic hydrocarbons (PAHs) depends on deposition from the atmosphere, revolatilization, leaching, and degradation processes such as photolysis and biodegradation. Quantifying the phase distribution and fluxes of these compounds across environmental compartments is thus crucial to understand the long-term contaminant fate. The gas-phase exchange between soil and atmosphere follows chemical fugacity gradients that can be approximated by gas-phase concentrations, yet which are difficult to measure directly. Thus, passive sampling, measured sorption isotherms, or empirical relationships to estimate sorption distribution have been combined in this study to determine aqueous (or gas) phase concentrations from measured bulk concentrations in soil solids. All these methods have their strengths and weaknesses but agree within 1 order of magnitude except for ex situ passive samplers employed in soil slurries, which estimated much lower concentrations in soil water and gas likely due to experimental artifacts. In field measurements, PAH concentrations determined in the atmosphere show a pronounced seasonality with some revolatilization during summer and gaseous deposition during winter, but overall dry deposition dominates annual mean fluxes. The characteristic patterns of PAHs in the different phases (gas phase, atmospheric passive samplers, bulk deposition, and soil solids) confirm the expected compound-specific distribution pattern and behavior. Since revolatilization fluxes in summer are only minor and wet and dry deposition is ongoing, our results clearly show that the PAH loads in topsoils will continue to increase.

Current use pesticides in soil and air from two agricultural sites in South Africa: Implications for environmental fate and human exposure

Concerns about the possible negative impacts of current use pesticides (CUPs) for both the environment and human health have increased worldwide. However, the knowledge on the occurrence of CUPs in soil and air and the related human exposure in Africa is limited. This study investigated the presence of 30 CUPs in soil and air at two distinct agricultural sites in South Africa and estimated the human exposure and related risks to rural residents via soil ingestion and inhalation (using hazard quotients, hazard index and relative potency factors). We collected 12 soil and 14 air samples over seven days during the main pesticide application season in 2018. All samples were extracted, purified and analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. In soils, nine CUPs were found, with chlorpyrifos, carbaryl and tebuconazole having the highest concentrations (up to 63.6, 1.10 and 0.212 ng g^-1, respectively). In air, 16 CUPs were found, with carbaryl, tebuconazole and terbuthylazine having the highest levels (up to 25.0, 22.2 and 1.94 pg m^-3, respectively). Spatial differences were observed between the two sites for seven CUPs in air and two in soils. A large dominance towards the particulate phase was found for almost all CUPs, which could be related to mass transport kinetics limitations (non-equilibrium) following pesticide application. The estimated daily intake via soil ingestion and inhalation of individual pesticides ranged from 0.126 fg kg^-1 day^-1 (isoproturon) to 14.7 ng kg^-1 day^-1 (chlorpyrifos). Except for chlorpyrifos, soil ingestion generally represented a minor exposure pathway compared to inhalation (i.e. <5%). The pesticide environmental exposure largely differed between the residents of the two distinct agricultural sites in terms of levels and composition. The estimated human health risks due to soil ingestion and inhalation of pesticides were negligible although future studies should explore other relevant pathways.

Seasonal variations in air concentrations of 27 organochlorine pesticides (OCPs) and 25 current-use pesticides (CUPs) across three agricultural areas of South Africa

For decades pesticides have been used in agriculture, however, the occurrence of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs) is poorly understood in Africa. This study investigates air concentrations of OCPs and CUPs in three South African agricultural areas, their spatial/seasonal variations and mixture profiles. Between 2017 and 2018, 54 polyurethane foam-disks passive air-samplers (PUF-PAS) were positioned in three agricultural areas of the Western Cape, producing mainly apples, table grapes and wheat. Within areas, 25 CUPs were measured at two sites (farm and village), and 27 OCPs at one site (farm). Kruskal-Wallis tests investigated area differences in OCPs concentrations, and linear mixed-effect models studied differences in CUPs concentrations between areas, sites and sampling rounds. In total, 20 OCPs and 16 CUPs were detected. A median of 16 OCPs and 10 CUPs were detected per sample, making a total of 11 OCPs and 24 CUPs combinations. Eight OCPs (trans-chlordane, o,p'-/p,p'-dichlorodiphenyldichloroethylene (DDE)/dichlorodiphenyltrichloroethane (DDT), endosulfan sulfate, γ-hexachlorocyclohexane and mirex) and two CUPs (carbaryl and chlorpyrifos) were quantified in all samples. p,p'-DDE (median 0.14 ng/m³) and chlorpyrifos (median 0.70 ng/m³) showed the highest concentrations throughout the study. Several OCPs and CUPs showed different concentrations between areas and seasons, although CUPs concentrations did not differ between sites. OCPs ratios suggest ongoing chlordane use in the region, while DDT and endosulfan contamination result from past-use. Our study revealed spatial and seasonal variations of different OCPs and CUPs combinations detected in air. Further studies are needed to investigate the potential cumulative or synergistic risks of the detected pesticides.

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.

Soil-air partitioning of semivolatile organic compounds in the Lesser Himalaya region: Influence of soil organic matter, atmospheric transport processes and secondary emissions

After decades of imposed regulations about reducing the primary emissions of persistent organic pollutants (POPs), these pollutants are still present in the environment. Soils are important repositories of such persistent semivolatile organic contaminants (SVOCs), and it is assumed that SVOCs sequestered in these reservoirs are being re-mobilized due to anthropogenic influence. In this study, concentrations of organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) in soil and air, their fugacities, fluxes and the soil-air partition coefficient (K_SA) were determined for three different land cover types (glacial, remote/mountainous and urban) of the Lesser Himalayan Region (LHR). The concentrations of OCPs, PCBs and PBDEs in soils and air ranged between 0.01 and 2.8, 0.81-4.8, 0.089-0.75 ng g^-1; 0.2-106, 0.027-182, and 0.011-7.26 pg m^-3, respectively. The levels of SVOCs in the soil were correlated with soil organic matter (SOM) indicating that SOM is a substrate for the organic pollutants in soils. The Clausius-Clapeyron plots between ln P and inverse of temperature (1000/T) suggested that long range atmospheric transport was the major input source of PBDEs and higher chlorinated PCBs over the LHR. The uneven and wide distribution of local sources in LHR and up-slope enrichment of SVOCs explained the spatial variability and altitudinal patterns. The soils near mountain and urban lakes act as local sinks of SVOCs such as β-HCH, pp΄-DDT, CB-28, -118, -153, BDE-47, -99, and -154, with soil-air exchange fluxes tending more toward deposition. However, the soils near glacial lakes acted as local sources of more volatile congeners of α-HCH, γ-HCH, op'-DDT, pp'-DDE and lower to medium chlorinated PCBs such as CB-18, -28, -53, -42 and BDE-47, -99, with soil-air exchange tending more toward volatilization flux.

Release, transformation, and risk factors of polybrominated diphenyl ethers from landfills to the surrounding environments: A review

Polybrominated diphenyl ethers (PBDEs) serve as brominated flame retardants when added to various products. When these products reach their end of life, a large amount of domestic waste containing PBDEs enters the landfills. Given their weak chemical bonds, they are easily affected by physical, chemical, and biological processes. These processes result in their release and the subsequent contamination of the surrounding soil, groundwater, and atmosphere, causing harm to humans and ecosystems. However, despite the progress made in the research of PBDEs over the years, understanding of the environmental behavior and fate of pollutants is still limited. With the development of cities, the release of PBDEs in old landfills will gradually increase the risk to the surrounding environment. Here we review the biological and nonbiological transformation of PBDEs and their derivatives in landfills and surrounding areas, as well as their distribution in soil, groundwater, and atmosphere. Specifically, this review aims to provide insights into the following aspects: 1) the biological (plant, animal, and microbial) and nonbiological (metal catalysis and photodegradation) conversion of PBDEs and their derivatives in landfills and surrounding areas; 2) the distribution of landfill-sourced PBDEs in the soil, groundwater, atmosphere and cross-media migration; and 3) suggestions and future research directions for the management and control of PBDEs in landfills.

Atmospheric deposition of chlorinated and brominated polycyclic aromatic hydrocarbons in central Europe analyzed by GC-MS/MS

Chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs) are persistent organic pollutants that are ubiquitous in the atmospheric environment. The sources, fate, and sinks in the atmosphere of these substances are largely unknown. One of the reasons is the lack of widely accessible analytical instrumentation. In this study, a new analytical method for ClPAHs and BrPAHs using gas-chromatography coupled with triple quadrupole mass spectrometry is presented. The method was applied to determine ClPAHs and BrPAHs in total deposition samples collected at two sites in central Europe. Deposition fluxes of ClPAHs and BrPAHs ranged 580 (272-962) and 494 (161-936) pg m-2 day-1, respectively, at a regional background site, Košetice, and 547 (351-724) and 449 (202-758) pg m-2 day-1, respectively, at a semi-urban site, Praha-Libuš. These fluxes are similar to those of PCBs and more than 2 orders of magnitude lower than those of the parent PAHs in the region. Seasonal variations of the deposition fluxes of these halogenated PAHs were found with maxima in summer and autumn, and minima in winter at Košetice, but vice versa at Praha-Libuš. The distribution of ClPAHs and BrPAHs between the particulate and dissolved phases in deposition samples suggests higher degradability of particulate BrFlt/Pyr and BrBaA than of the corresponding ClPAHs. A number of congeners were detected for the first time in the atmospheric environment.

NPAHs and OPAHs in the atmosphere of two central European cities: Seasonality, urban-to-background gradients, cancer risks and gas-to-particle partitioning

Derivatives of polycyclic aromatic hydrocarbons (PAHs) such as nitrated- and oxygenated-PAHs (NPAHs and OPAHs) could be even more toxic and harmful for the environment and humans than PAHs. We assessed the spatial and seasonal variations of NPAHs and OPAHs atmospheric levels, their cancer risks and their gas-to-particle partitioning. To this end, about 250 samples of fine particulate matter (PM2.5) and 50 gaseous samples were collected in 2017 in central Europe in the cities of Brno and Ljubljana (two traffic and two urban background sites) as well as one rural site. The average particulate concentrations were ranging from below limit of quantification to 593 pg m-3 for Σ9NPAHs and from 1.64 to 4330 pg m-3 for Σ11OPAHs, with significantly higher concentrations in winter compared to summer. In winter, the particulate levels of NPAHs and OPAHs were higher at the traffic site compared to the urban background site in Brno while the opposite was found in Ljubljana. NPAHs and OPAHs particulate levels were influenced by the meteorological parameters and co-varied with several air pollutants. The significance of secondary formation on the occurrence of some NPAHs and OPAHs is indicated. In winter, 27-47% of samples collected at all sites were above the acceptable lifetime carcinogenic risk. The gas-particle partitioning of NPAHs and OPAHs was influenced by their physico-chemical properties, the season and the site-specific aerosol composition. Three NPAHs and five OPAHs had higher particulate mass fractions at the traffic site, suggesting they could be primarily emitted as particles from vehicle traffic and subsequently partitioning to the gas phase along air transport. This study underlines the importance of inclusion of the gas phase in addition to the particulate phase when assessing the atmospheric fate of polycyclic aromatic compounds and also when assessing the related health risk.

Past, present, and future perspectives on the assessment of bioavailability/bioaccessibility of polycyclic aromatic hydrocarbons: A 20-year systemic review based on scientific econometrics

Bioaccessibility/bioavailability (bioac-bioav) is an important criterion in the risk assessment of polycyclic aromatic hydrocarbons (PAHs), especially in the restoration of contaminated sites. Although, the bioac-bioav concept is widely employed in PAH risk assessment for both humans and wildlife, their growth and integration in risk assessment models are seldom discussed. Consequently, the relevant literature listed on Web of Science (WOS)™ was retrieved and analyzed using the bibliometric software Citespace in order to gain a comprehensive understanding of this issue. Due to the limitations of the literature search software, we manually searched the articles about PAHs bioac-bioav that were published before 2000. This stage focuses on research on the distribution coefficient of PAHs between different environmental phases and laid the foundation for the adsorption-desorption of PAHs in subsequent studies of the bioac-bioav of PAHs. The research progress on PAH bioac-bioav from 2000 to the present was evaluated using the Citespace software based on country- and discipline-wise publication volumes and research hotspots. The development stages of PAH bioac-bioav after 2000 were divided into four time segments. The first three segments (2000-2005, 2006-2010, and 2011-2015) focused on the degradation of PAHs and their in vivo (bioavailability)-in vitro (bioaccessibility) evaluation method and risk assessment. Meanwhile, the current (2016-present) research focuses on the establishment of analytical methods for assessing PAH derivatives at environmental concentrations and the optimization of various in vitro digestion methods, including chemical optimization (sorptive sink) and biological optimization (Caco-2 cell). The contents are aimed at supplying researchers with a deeper understanding of the development of PAH bioac-bioav.

Daytime Restricted Feeding Modifies the Temporal Expression of CYP1A1 and Attenuated Damage Induced by Benzo[a]pyrene in Rat Liver When Administered before CYP1A1 Acrophase

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that heterodimerizes with the AhR nuclear translocator (ARNT) to modulate CYP1A1 expression, a gene involved in the biotransformation of benzo[a]pyrene (BaP). The AhR pathway shows daily variations under the control of the circadian timing system. Daytime restricted feeding (DRF) entrains the expression of genes involved in the processing of nutrients and xenobiotics to food availability. Therefore, we evaluate if temporal AhR, ARNT, and CYP1A1 hepatic expression in rats are due to light/dark cycles or fasting/feeding cycles promoted by DRF. Our results show that AhR oscillates throughout the 24 h period in DRF and ad libitum feeding rats (ALF), showing maximum expression at the same time points. DRF modified the peak of ARNT expression at ZT5; meanwhile, ALF animals showed a peak of maximum expression at ZT17. An increased expression of CYP1A1 was linked to the meal time in both groups of animals. Although a high CYP1A1 expression has been previously associated with BaP genotoxicity, our results show that, compared with the ALF group, DRF attenuated the BaP-CYP1A1 induction potency, the liver DNA-BaP adducts, the liver concentration of unmetabolized BaP, and the blood aspartate aminotransferase and alanine aminotransferase activities when BaP is administered prior to the acrophase of CYP1A1 expression. These results demonstrate that DRF modifies the ARNT and CYP1A1 expression and protects from BaP toxicity.

Multistage Defense System Activated by Tetrachlorobiphenyl and its Hydroxylated and Methoxylated Derivatives in Oryza sativa

Crops can initiate various defense responses to environmental stresses. The process is often accompanied by extensive transcriptional and metabolic changes to reallocate metabolites. However, it remains unclear how organic pollutants activate the defense systems to reallocate metabolites in crops. The current study demonstrates that three defense systems, including the cytochrome P450s (CYP450s), glutathione S-transferases (GSTs), and phenylpropanoid biosynthesis, were sequentially activated after Oryza sativa was exposed to 2,3,4,5-tetrachlorobipheny l (PCB 61) and its derivatives 4'-hydroxy-2,3,4,5-tetrachlorobiphenyl (OH-PCB 61) and 4'-methoxy-2,3,4,5-tetrachlorobiphenyl (MeO-PCB 61), respectively. Genes encoding CYP76Ms and CYP72As were significantly upregulated after 0.5 h of exposure, followed by the GST-coding gene GSTU48, suggesting that the biotransformation and detoxification of PCB 61, OH-PCB 61, and MeO-PCB 61 occurred. Subsequently, CCR1 and CCR10 involved in phenylpropanoid biosynthesis were activated after 12 h, potentially reducing the oxidative stress induced by PCB 61 and its derivatives. Furthermore, β-d-glucan exohydrolase involved in both phenylpropanoid biosynthesis and starch and sucrose metabolism was significantly downregulated by 7.04-fold in the OH-PCB 61-treated group, potentially contributing to the inhibition of sugar hydrolysis. These findings provide insights into increasing rice adaptability to organic pollutants by reinforcing the enzyme-mediated defense systems, characterizing a novel and critical strategy that enables augmented crop outputs and quality in environments stressed by organic contaminants.

Occurrence, health risks and soil-air exchange of phthalate acid esters: A case study in plastic film greenhouses of Chongqing, China

The residue of phthalate acid esters (PAEs) in plastic film greenhouses had become a global concern environmental pollution problem. However, few studies have focused on the occurrence and fate of PAEs in the soil-air interface of the greenhouses. In this study, the occurrence, health risks, and soil-air exchange of PAEs from ten soil samples and four air samples of different greenhouses were investigated by a case study. The concentrations of total PAEs and individual PAEs congeners between two seasons were significantly different in the greenhouse soil and atmosphere. Di-(2-ethylhexyl) phthalate (1.04 mg kg^-1) and diisobutyl phthalate (0.16 mg kg^-1) were the predominant PAE congeners of soil in spring and autumn, respectively. Di-(2-ethylhexyl) phthalate was the major PAE congeners in the greenhouse atmosphere both of spring (0.03 μg m^-3) and autumn (1.32 μg m^-3). Health risks assessment showed that the predominant exposure route for adults was dietary intake, and the total carcinogenic risk level of PAEs was acceptable. Besides, fugacity model analysis indicated that di-(2-ethylhexyl) phthalate tended to deposit from air to soil with mean deposition flux of 175.1 kg (h⋅km²)^-1 in autumn and 11.9 kg (h⋅km²)^-1 in spring. On the contrary, diethyl phthalate escaped from soil with mean volatilization flux of 0.005 kg (h⋅km²)^-1 in autumn and 0.025 kg (h⋅km²)^-1 in spring. Other PAE congeners have tried to establish an equilibrium status through recycling continuously between the soil and air, and the source-sink relationships depended on their concentrations and hydrophobicity. This study showed that the distribution and movement of PAEs in the soil-air interface might be principally caused by temperature and their chemical properties.

Nitrated- and oxygenated-polycyclic aromatic hydrocarbon in urban soil from Nepal: Source assessment, air-soil exchange, and soil-air partitioning

In contrast to more frequently investigated priority pollutants, such as polycyclic aromatic hydrocarbons (PAHs), only little is known about the fate and distribution of nitrated- and oxygenated-PAHs (NPAHs and OPAHs) in urban soils, particularly in Indian sub-continent. Moreover, experimental data on air-soil exchange and soil-air partitioning are also lacking, which is critical in assessing the partitioning, fugacity coefficient, and secondary emission of PAH-derivatives. Hence, this article provides an insight into the fate, sources, air-soil exchange, and soil-air partitioning of PAH-derivatives on a molecular basis. Prospective health risk due to their exposure has also been discussed. The result showed that PAH-derivatives had significantly polluted all four Nepalese cities. Ʃ₁₅NPAHs and Ʃ₂OPAHs in soil were 4 and 20 times lower than their parent-PAHs, and ranged 396-2530 ng/g (median 458 ng/g) and 91.9-199 ng/g (median 94.9 ng/g), respectively. Ʃ₁₅NPAHs was higher than a few global studies, while Ʃ₂OPAHs was lower than some of the less urbanized/remote areas worldwide. The 6-Nitobenzo[a]pyrene (6-NBaP) was most abundant in soil, and accounted for 10-12% of Ʃ₁₅NPAHs, while Benzanthrone (BZONE) exceeded among OPAHs, and represented 71-76% of Ʃ₂OPAHs, respectively. Source identification study indicated that direct emissions from domestic/residential cooking and heating and secondary formations are the essential sources of derivative chemicals in soil. Fugacity fraction ratio (f_ratio) indicated volatilization from the soil. The soil-air partitioning study showed sorption by soil organic matter/black carbon has little role in soil-air partitioning of PAH-derivatives in Nepal's urban soil. The toxicity equivalency quotients (TEQs) of NPAHs (314 ± 102 ng/g) was estimated slightly higher than their parent-PAHs (294 ± 121 ng/g) suggesting a relatively higher risk of soil toxicity in Nepal.

Polycyclic aromatic compounds (PACs) in the Canadian environment: Links to global change

In this review, global change processes have been linked to polycyclic aromatic compounds (PACs) in Canada and a first national budget of sources and sinks has been derived. Sources are dominated by wildfire emissions that affect western and northern regions of Canada disproportionately due to the location of Pacific and boreal forests and the direction of prevailing winds. Wildfire emissions are projected to increase under climate warming along with releases from the thawing of glaciers and permafrost. Residential wood combustion, domestic transportation and industry contribute the bulk of anthropogenic emissions, though they are substantially smaller than wildfire emissions and are not expected to change considerably in coming years. Other sources such as accidental spills, deforestation, and re-emission of previous industrial deposition are expected to contribute anthropogenic and biogenic PACs to nearby ecosystems. PAC sinks are less well-understood. Atmospheric deposition is similar in magnitude to anthropogenic sources. Considerable knowledge gaps preclude the estimation of environmental transformations and transboundary flows, and assessing the importance of climate change relative to shifts in population distribution and energy production is not yet possible. The outlook for PACs in the Arctic is uncertain due to conflicting assessments of competing factors and limited measurements, some of which provide a baseline but have not been followed up in recent years. Climate change has led to an increase in primary productivity in the Arctic Ocean, but PAC-related impacts on marine biota appear to be modest. The net effect of changes in ecological exposure from changing emissions and environmental conditions throughout Canada remains to be seen. Evidence suggests that the PAC budget at the national scale does not represent impacts at the local or regional level. The ability to assess future trends depends on improvements to Canada's environmental measurement strategy and biogeochemical modelling capability.

Semi-centennial sediment records of HCHs and DDTs from the East China marginal seas: Role of lateral transport in catchment

We reconstructed the history of the inputs of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) into the marine environment to reveal the time-dependent influence of sources and associated anthropogenic activities in China, based on ²¹⁰Pb-dated cores from the East China marginal seas (ECMS). The temporal dynamics of pesticide contamination expresses as deposition fluxes, inventories, and half-life estimations varied among the cores, suggesting heterogeneity in transport pathways of pollutants. The depth profiles of pesticide inputs closely followed their historical production and application timelines in China, and were also affected by human activities in catchments, with general declines in HCH and DDT inputs to the coring sites after their peak deposition. Despite the prevalence of occurrence of weathered HCH/DDT in the cores, there were clear source-dependent differences in isomeric composition and accumulation between before and after these pesticides were banned. α-HCH and p,p'-DDT were relatively more enriched in sediments from the pre-ban period when heavy technical HCHs and DDTs use occurred, as indicated by the higher α-/β-HCH and lower (DDE + DDD)/DDTs ratios, and the larger fractions of α-HCH and p,p'-DDT influxes to the coring sites in the ΣHCH and ΣDDT fluxes, respectively, while this pattern shifted to be historical residue-based in the post-ban period. The difference in the recent influxes of pesticides to core sediments and their higher post-ban inventories highlight the increasing importance of historical sources over time and continuous input of weathered residues into marine environment via lateral transport.

Nuclear abnormalities in umbilical cord blood lymphocytes of newborns from the Ahome and Guasave municipalities in Sinaloa, Mexico

AIM

We measured the frequency of nuclear abnormalities of 210 blood samples from the umbilical cord, since human fetuses are exposed to environmental mixtures of pesticides that induce DNA damage.

METHODS

The determinations were made through the micronucleus assay test in lymphocytes from the umbilical cord blood of newborns whose mothers live in Ahome (n = 105) and Guasave (n = 105), Sinaloa, Mexico.

RESULTS

The average frequency of anomalies in 1000 cells were, respectively: micronucleus 0.4 vs. 2.9, pyknotic cells 18.3 vs. 109.2, chromatin condensation 7.7 vs. 150.1, karyolitic cells 1.8 vs. 24.4, and binucleated cells 4.9 vs. 74.6. The calculated Pearson correlation factors of nuclear abnormality frequencies between both municipalities were low and negative, suggesting that they did not correlate between the Ahome and Guasave newborns and indicating a higher number of mothers exposed in Guasave.

CONCLUSION

Our data suggest that monitoring nuclear abnormalities in umbilical cord blood samples could be a useful tool to identify transplacental mutagens perfusion that is being discharged into the local environment.

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 legacy organochlorine pesticides and their recent exchange dynamics in the Northwest Pacific Ocean

The occurrence and air-sea gas exchange of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and chlordanes were determined in the Northwest Pacific Ocean (NWP) in spring to elucidate their current pollution status and fate. ΣHCHs, ΣDDTs, and Σchlordanes in air (sum of gaseous and aerosol phase) ranged from 9.37 to 102, from 1.73 to 12.8, and from 0.24 to 14.9 pg/m³, respectively, with their dissolved levels being 30.7-518, 7.10-80.5, and 0.25-7.10 pg/L, respectively. HCHs, DDTs, and chlordanes cause substantial contamination of the air and seawater of the East China Sea (ECS), indicating significant OCP inputs from China. Isomer ratios of HCHs and DDTs provided a fingerprint of East Asian emissions of legacy OCPs, with the pollution profiles of HCHs and DDTs dominated by lindane and combined dicofol-type and weathered technical DDTs, respectively. The former result is consistent with the apparent decline in air α-HCH levels over the ECS. Different from still net deposition of gaseous α- and γ-HCH in the NWP, outgassing of trans-chlordane, cis-chlordane, and DDTs other than dicofol-sourced o,p'-DDT was indicated. This observation attributes to intensive historical usage of technical HCHs and the prevalence of lindane pollution in East Asia, and demonstrates the transitioning role of seawater as a source for residual OCPs in the East Asia-NWP region. Significant subcooled liquid vapor pressure-based relationships for legacy OCPs were identified mainly in marine air masses; these were different from land-sourced polybrominated diphenyl ethers, and suggested a heterogeneous role of ocean- and land-based sources in atmospheric partitioning of these pollutants.

New classes of organic pollutants in the remote continental environment - Chlorinated and brominated polycyclic aromatic hydrocarbons on the Tibetan Plateau

Halogenated polycyclic aromatic hydrocarbons are carcinogenic and ubiquitous environmental organic pollutants. The abundance and sources of these compounds have not been studied in remote environments. We collected and analyzed air, soil, lichen, and moss samples from the Tibetan Plateau. Concentrations of chlorinated polycyclic aromatic hydrocarbons were 0.78-4.16 pg/m³ in air, 3.11-297 pg/g in soil, 260-741 pg/g in lichens, and 338-934 pg/g in mosses. Concentrations of brominated polycyclic aromatic hydrocarbons were 0.15-0.59 pg/m³ in air, 0.61-72.3 pg/g in soil, 33.5-64.9 pg/g in lichens, and 20.5-72.5 pg/g in mosses. The dominant congeners were 9- and 2-chlorophenanthrene, 1-chloropyrene, 3-chlorofluoranthene, and 1-bromopyrene. We found correlations between congener concentrations in lichens and in air, and lichens effectively predicted near-ground atmospheric concentrations of the pollutants. The enrichment of photochemically stable compounds in high-altitude environments is influenced by their physicochemical properties. Principal component analysis with multivariate linear regression of chlorinated polycyclic aromatic hydrocarbons measured in lichens provided an assessment of the relative source contributions, and suggested that in Medog County of Tibetan Plateau, 48% was likely from long-range combustion sources, 26% was from local burning sources, and 26% was from photochemical formation.

Organochlorine pesticides in the surrounding soils of POPs destruction facility: source fingerprinting, human health, and ecological risks assessment

The elimination of persistent organic pollutants (POPs) obsolete pesticides stockpiles, particularly the organochlorine pesticides (OCPs), is one of the critical environmental issues faced by many developing countries. This pioneering study aimed to investigate the occurrence, source fingerprinting, human health, and ecological risks of OCPs in the surroundings of the lone POPs pesticide destruction facility in Pakistan. The ΣOCPs residual levels in soil ranged from 35.98 to 566.77 ng/g dry weight (dw), with a mean concentration of 174.42 + 111.62 ng/g (dw). The OCPs contamination levels in the soil followed the pattern as ΣHCHs > Σendrins > Σendosulfans > dieldrin > Σheptachlors > ΣDDTs > Σchlordanes > methoxychlor. The ΣHCHs residual concentrations were comparatively higher than the previous national and global soil studies. The recent accumulation of HCHs, DDTs, and heptachlor was observed in the study area as identified by β-HCH/∑HCHs, (DDE + DDD)/ΣDDTs, heptachlor/Σheptachlor, and heptachlor exo-epoxide/heptachlor ratios. The OCPs' lifetime carcinogenic risk through ingestion, dermal, and inhalation exposure routes ranged from 1.65E-08 to 2.91E-07, whereas the noncarcinogenic hazard quotient (HQ) ranged from 9.12E-05 to 1.61E-03. The risk vulnerability among age groups was in the order: adult > toddler > child > teen > infant. The calculated risk levels were within an acceptable limit of one in a million (1 × 10^-6) for carcinogenic risk and HQ < 1 for noncarcinogenic risk. The current OCPs residual levels, especially dieldrin and endrin, exhibited low to medium ecological risks when compared to various worldwide limits. The upsurge of the OCPs' environmental contamination levels over the years and consideration of the food chain transfer might amplify the human health and ecological risks intensities.

Investigation of polycyclic aromatic hydrocarbons in soils from Caserta provincial territory, southern Italy: Spatial distribution, source apportionment, and risk assessment

The concentrations of polycyclic aromatic hydrocarbons (PAHs) in soils from Caserta provincial territory, southern Italy, were systematically investigated along with their correlations with soil properties and health risk. The concentrations of ∑₁₆PAHs ranged from 10.0 to 4191 ng/g, with a median (1 st quartile, Q1; 3rd quartile, Q3) of 28.5 (17.5-65.0) ng/g; Four-ring PAHs were the most abundant and contributed an average of ∼50.2% of the ∑₁₆PAHs. Significant differences in the spatial distributions of PAHs in soil were observed, with higher levels of PAH contamination found in Caserta city and the surrounding areas. According to the positive matrix factorization (PMF) model, three sources were identified: chemical production and metal smelting, vehicle emissions, and coal/biomass combustion. Soil total organic carbon was significantly correlated with the concentration of total PAHs and the concentrations of PAHs with three-, four-, and five-rings. In contrast, only the concentration of ∑₄DBPs (dibenzo(a,e)pyrene, dibenzo(a,h)pyrene, dibenzo(a,i)pyrene, dibenzo(a,l)pyrene) was well correlated with population density. The soil mass inventory of ∑₁₆PAHs was estimated to be 6.87 metric tons (geometric mean). The ecological risks posed by PAHs in the study are negligible; however, health risks of exposure to soil-borne PAHs were identified based on a probabilistic risk model.

Multiyear levels of PCDD/Fs, dl-PCBs and PAHs in background air in central Europe and implications for deposition

This study presents four years ambient monitoring data of seventeen 2,3,7,8-chlorine substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), twelve dioxin-like polychlorinated biphenyls (dl-PCBs) and sixteen polycyclic aromatic hydrocarbons (PAHs) designed by the US EPA at a background site in central Europe during 2011-2014. The concentrations expressed as toxic equivalents (TEQs) using the WHO₂₀₀₅-scheme for PCDD/Fs (0.2 fg m^-3-61.1 fg m^-3) were higher than for dl-PCBs (0.01 fg m^-3-2.9 fg m^-3), while the opposite was found in terms of mass concentrations. ΣPAHs ranged from 0.20 ng m^-3 to 134 ng m^-3. The mass concentration profile of PCDD/Fs, dl-PCBs and PAHs was similar throughout the four years. PCDD/Fs and PAHs concentrations were dominated by primary sources peaking in winter, while those of dl-PCBs were controlled by secondary sources characterized by a spring-summer peak. During 2011-2014, no significant decrease in the atmospheric levels of ΣPCDD/Fs was observed. On the other hand, the concentrations of Σdl-PCBs and ΣPAHs were decreasing, with halving times of 5.7 and 2.7 years, respectively. We estimated that 422 pg m^-2 year^-1-567 pg m^-2 year^-1 TEQ PCDD/Fs and 3.48 pg m^-2 year^-1-15.8 pg m^-2 year^-1 TEQ dl-PCBs were transferred from the air to the ground surfaces via dry particulate deposition during 2011-2014.

Air-soil diffusive exchange of PAHs in an urban park of Shanghai based on polyethylene passive sampling: Vertical distribution, vegetation influence and diffusive flux

Compared with dry and wet deposition rates, air-soil exchange fluxes cannot be directly measured experimentally. Polyethylene passive sampling was applied to assess transport directions and to measure concentration gradients in order to calculate diffusive fluxes of polycyclic aromatic hydrocarbons (PAHs) across the air-soil interface in an urban park of Shanghai, China. Seven campaigns with high spatial resolution sampling at 18 heights between 0 and 200 cm above the ground were conducted in 2017-2018. Air-to-soil deposition was observed, e.g. for phenanthrene, and soil-to-air volatilization for high molecular weight compounds, such as benzo[b]fluoranthene. Significant linear correlations between gaseous PAH concentration and log-transformed height were observed. Influence of vegetation on vertical concentration gradients of gaseous PAHs was insignificant in most cases except during the growing season. Local micrometeorological conditions resulted in a directional eddy diffusion in air and then influenced vertical diffusion of gaseous PAHs. Furthermore, the vertical eddy diffusivity was estimated as a function of distance to the air-soil surface. Air-soil exchange fluxes based on the Mackay's fugacity approach were calculated and confirmed by diffusive fluxes within air layer based on vertical concentration gradient of PAHs and eddy/molecular diffusion. Polyethylene passive sampling technology provides a useful tool to investigate air-soil exchange process.

Atmospheric deposition and air-soil exchange of polybrominated diphenyl ethers (PBDEs) in a background site in Central China

Jinsha (JSH) is one of the regional background sites in Central China. In this study, eight polybrominated diphenyl ethers (PBDEs) were measured in atmospheric deposition samples (dry particle, wet particle, and wet dissolved), air (gaseous and particle) samples, and soil samples that were collected from March 2012 to March 2013. Of all eight PBDEs, BDE-209 was the most abundant congener in both deposition samples and air/soil samples. Average dry particle, wet particle, and wet dissolved deposition fluxes of Σ₈PBDEs were 270 ± 310 pg m^-2 day^-1, 130 ± 210 pg m^-2 day^-1, and 250 ± 330 pg m^-2 day^-1, respectively, while those of BDE-209 were 210 ± 290 pg m^-2 day^-1, 80 ± 120 pg m^-2 day^-1, and 160 ± 290 pg m^-2 day^-1, respectively. Dry deposition velocities of individual PBDE ranged from 0.11 ± 0.15 cm s^-1 (BDE-183) to 0.24 ± 0.38 cm s^-1 (BDE-209), and total washout ratios ranged from 5.0 × 10³ (BDE-28) to 4.2 × 10⁴ (BDE-209). The calculated net air-soil gas exchange flux of Σ₈PBDEs was - 16 ± 13 pg m^-2 day^-1, suggesting the deposition status of PBDEs. The gas exchange flux at the air-soil interface was significantly lower than the deposition flux, which only accounted for 2.5% of the total deposition flux, implying that atmospheric deposition was an important input pathway for PBDEs to soils. Overall, the pollution level of the soil was relatively low, and the soil serves as a sink for PBDEs from adjacent regions.

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.

Comparability of long-term temporal trends of POPs from co-located active and passive air monitoring networks in Europe

The comparability of data from active (ACT) and passive sampling (PAS) of persistent organic pollutants (POPs) in air is hindered by uncertainties related to the derivation of sampling rates and concentrations, as well as differences in the duration, volume and frequency of sampling. Although data from ACT have been used extensively in short-term PAS calibration studies, no attempts have been made to evaluate the comparability of long-term trends calculated from PAS to established ACT trends. This is crucial, as continuous long-term ACT is unfeasible in most regions of the world. To address these challenges, we calculated and compared trends for organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) at the six sites in Europe with at least 5 years of co-located ACT and PAS data (2012-2016): Birkenes, Košetice, Pallas, Råö, Stórhöfði and Zeppelin. Strong agreement of ACT and PAS trends was observed for most OCPs and PCBs. Apart from two PCBs at Stórhöfði, all pairs of ACT and PAS trends followed the same direction. However, differences in the magnitude, significance and confidence intervals of their slopes were observed for some compounds and were primarily attributed to the short duration of the PAS time series. Despite some limitations, our results suggest that the comparability of ACT and PAS POP trends will continue to improve with additional years of data. This study confirms the suitability of PAS for the calculation of long-term POP trends in air, and highlights the importance of continuous sampling at established monitoring sites with consistent analytical methods.

Proximity to chemical equilibria among air, water, soil, and sediment as varied with partition coefficients: A case study of polychlorinated dibenzodioxins/furans, polybrominated diphenyl ethers, phthalates, and polycyclic aromatic hydrocarbons

To capture the pollutant distribution status among environmental media and to understand how the distribution varies with the pollutants' properties, we assessed a total of 225 fugacity ratios (FRs) of 45 semi-volatile organic compounds (SVOCs) (polychlorinated dibenzo-p-dioxins/furans (PCDDs/Fs), polybrominated diphenyl ethers (PBDEs), phthalates, and polycyclic aromatic hydrocarbons (PAHs)) for five medium pairs (air-water, air-soil, water-sediment, soil-water, and soil-sediment) using the nationwide multimedia monitoring data. For many of the pollutants, fugacity was greatest in air (PCDFs and 6 heavy PAHs) and in sediment (PBDEs and 9 light PAHs) while lowest in soil for most of the pollutants. PAHs and phthalates appeared to be farther away from equilibrium than PCDDs/Fs and PBDEs. The ratios of "equilibrium improbable" FRs to all the FRs in each chemical group were 2%, 0%, 33.3%, and 28.9% for PCDDs/Fs, PBDEs, phthalates, and PAHs, respectively. FR_water/air of PAHs, FR_soil/air, and FR_{sediment/water} of the pollutant groups (except for PBDEs) decreased significantly (p < 0.01) with the partition coefficients, 1/K_air/water (1/K_aw), K_octanol/air (K_oa), and K_{octanol/water} (K_ow), respectively, even in the field conditions. The findings on FRs values provide valuable clues to identifying the media that would act as sink or source for certain chemicals and to using a more appropriate choice in the coherence test of environmental quality objectives, which should be important considerations in the management of chemical contamination in the environment.

Characterization of Tibetan Soil As a Source or Sink of Atmospheric Persistent Organic Pollutants: Seasonal Shift and Impact of Global Warming

Background soils are reservoirs of persistent organic pollutants (POPs). After decades of reduced primary emissions, it is now possible that the POPs contained in these reservoirs are being remobilized because of climate warming. However, a comprehensive investigation into the remobilization of POPs from background soil on the largest and highest plateau on Earth, the Tibetan Plateau (TP), is lacking. In this study, a sampling campaign was carried out on the TP at three background sites with different land cover types (forest, meadow and desert). Field measurements of the air-soil exchange of POPs showed that previous prediction using empirical models overestimated the values of the soil-air partitioning coefficient ( K_SA), especially for chemicals with K_OA > 9. The direction of exchange for γ-HCH, HCB, and PCB-28 overlapped with the air-soil equilibrium range, but with a tendency for volatilization. Their emission fluxes were 720, 2935, and 538 pg m^-2 day^-1, respectively, and were similar in extent to those observed for background Arctic soil in Norway. Nam Co and Ngari are also permafrost regions, and most chemicals at these two sites exhibited volatilization. This is the first result showing that permafrost can also emit POPs. Seasonally, we found that chemicals tended to be re-emitted from soils to the atmosphere in winter and deposited from the air to the soil in summer. This finding is opposite to most previous results, possibly because of the higher air-soil concentration gradient caused by the prevailing transport of POPs in summer. Climate warming exerts a strong influence on air-soil exchange, with an increase of 1 °C in ambient temperature likely leading to an increase of Tibetan atmospheric inventories of POPs by 60-400%.

Solid fuel combustion as a major contributor of polycyclic aromatic hydrocarbons in rural China: Evidence from emission inventory and congener profiles in tree bark

Polycyclic aromatic hydrocarbons (PAHs) remain a focal concern of the air pollution in China. To discriminate the sources of airborne PAHs in Chinese rural regions, a national-scale tree bark sampling campaign and emission inventory estimation were conducted. The concentrations of the sum of 16 U.S. EPA priority PAHs in rural bark ranged from 6.30 to 3803 ng/g, with the dominance of 3- and 4-ring PAHs. Bark residual PAH concentration correlated significantly with emission flux rate, bark lipid content, ambient PM_2.5, precipitation and sampling location. Based on the information of emission data, bark PAH congener profiles, principal component analysis, diagnostic ratios and compound-specific isotope analysis, solid fuel combustion was identified as the major source and could explain 40.3%-46.4% of bark PAH residues in rural China. The δ¹³C values of most individual PAHs were more negative at sites with lower longitude and latitude, suggesting a greater contribution of biomass combustion to PAH residues. Our results suggest the importance of regulating solid fuel combustion to significantly improve the air quality in China, and bark samples can provide a wealth of information on effectively monitoring and controlling the sources of PAH emission in rural China.

The occurrence of OCPs, PCBs, and PAHs in the soil, air, and bulk deposition of the Naples metropolitan area, southern Italy: Implications for sources and environmental processes

I am often reminded of the famous saying of Goethe: "Vedi Napoli e poi muori! - See Naples and die!". Sadly, Naples is now confronted with a number of serious, ongoing problems with a need to alleviate pressure on the worsening environment. One serious problem facing the environment is the presence of the potentially hazardous persistent organic pollutants (POPs), although few systematic studies at regional scale have been conducted. In this study, samples of soil, air, and bulk deposition were collected in Naples metropolitan area (NMA) to characterize the status of POPs, including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polycyclic aromatic hydrocarbons (PAHs). The results obtained showed that most of these compounds are pervasive in all the studied environmental matrices, especially in some hotspot areas, such as the Bagnoli Brownfield Site and the infamous "Triangle of the Death", where unwanted ecological risk conditions for PAHs and Endosulfan were determined, respectively. The interactional complexity between urban and the surrounding rural areas was also confirmed, as is the role that urban areas play in the migration and transformation process of POPs. High urban-rural gradients for atmospheric PAHs and PCBs were observed in the NMA, and the urban areas were identified as the emission source of these contaminants. Similarly, the OCP residues, historically originated from the nearby agricultural regions, experience long-term soil re-emission and continuously influence the connected urban environment via atmospheric transport processes.

Pivotal Role of Snow Deposition and Melting Driving Fluxes of Polycyclic Aromatic Hydrocarbons at Coastal Livingston Island (Antarctica)

The atmosphere-land-ocean dynamics of semivolatile organic compounds in polar regions is poorly understood, also for the abundant and ubiquitous polycyclic aromatic hydrocarbons (PAHs). We report the concentrations and fluxes of PAHs in a polar coastal ecosystem (Livingston Island, Antarctica). From late spring (December 2014) to late summer (February 2015), we sampled air, snow, coastal seawater, plankton, and the fugacity in soils and snow. The concentrations of PAHs in seawater were low but increased during the austral summer. The PAH concentrations in snow were significantly higher than in coastal seawater. Soil-air fugacity ratios showed a net volatilization of PAH when soils were covered with lichens, and close to air-soil equilibrium for bare soils. Concentrations in surface snow were also close to equilibrium with atmospheric PAHs. Conversely, there was a net diffusive deposition of PAHs to coastal seawater during late spring, but a net volatilization from seawater during late summer. Volatilization fluxes were correlated with seawater temperature and salinity, consistent with a key role of snowmelt to the fluxes and dissolved phase concentrations during the austral summer. The comprehensive assessment provided here shows that the fugacity amplification in snow is transferred to soils and coastal seawater supporting PAH concentrations and fluxes.