Inter-regional multimedia fate analysis of PAHs and potential risk assessment by integrating deep learning and climate change scenarios

Evaluation and prediction of anthropogenic impacts on long-term multimedia fate and health risks of PFOS and PFOA in the Elbe River Basin

Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have aroused great concern owing to their widespread occurrence and toxic effects. However, their long-term trends and multimedia fate remain largely unknown. Here, we investigate the spatiotemporal characteristics and periodic oscillations of PFOS and PFOA in the Elbe River between 2010 and 2021. Anthropogenic emission inventories and multimedia fugacity model were developed to analyse their historical and future transport fates and quantify related human risks in each medium for the three age groups. The results show that average PFOS and PFOA concentrations in the Elbe River were 4.08 and 3.41 ng/L, declining at the annual rate of 7.36% and 4.98% during the study period, respectively. Periodic oscillations of their concentrations and mass fluxes were most pronounced at 40-60 and 20-40 months. The multimedia fugacity model revealed that higher concentrations occurred in fish (PFOS: 14.29, PFOA: 0.40 ng/g), while the soil was their dominant sink (PFOS: 179, PFOA: 95 tons). The exchange flux between water and sediment was the dominant pathway in multimedia transportation (397 kg/year). Although PFOS and PFOA concentrations are projected to decrease by 22.41% and 50.08%, respectively, from 2021 to 2050, the hazard quotient of PFOS in fish is a low hazard. This study provides information for the assessment of PFOS and PFOA pollution in global watersheds and the development of related mitigation policies, such as banning fish predation in polluted rivers, to mitigate their risks.

Lagging pollution of polycyclic aromatic hydrocarbons in the rebuilt e-waste site: From the perspective of characteristics, sources, and risk assessment

Little information is known regarding how the lagged pollution of polycyclic aromatic hydrocarbon (PAH) influenced the environment and human health after an e-waste dismantling site was rebuilt. This study investigated the characteristics, sources, and risk assessment of PAHs in a rebuilt e-waste site and its surrounding farmland by analyzing the samples of soil, dust, water, and vegetable. Concentrations of PAHs in soil, vegetable and water in the rebuilt site were relatively higher than in its surrounding farmland. The concentrations in surface soils, soil columns, dust, vegetables, and water varied from 55.4 to 3990 ng g-1, 1.65 to 5060 ng g-1, 2190 to 2420 ng g-1, 2670 to 10,300 ng g-1, and 46.8 to 110 μg L-1 in the e-waste site, respectively. On the farmland, PAH concentrations in surface soils, vegetables, and water ranged from 41.5 to 2760 ng g-1, 506 to 7640 ng g-1, and 56.6 to 89.2 μg L-1, respectively. A higher proportion of high-molecular-weight PAHs (HMW-PAHs) appeared in all multimedia compared with low-molecular-weight PAHs (LMW-PAHs). Diagnostic ratio together with positive matrix factorization (PMF) revealed that vehicle emission was the primary source in this area, and the activity of e-waste disposal was another important source in the rebuilt e-waste site. Based on the deterministic health risks, people working in the reconstructed e-waste site were exposed to low risks, whereas the residents living near the surrounding farmland were exposed to low risk. Sensitivity analyses indicated that exposure frequency and PAH concentrations were the main factors that influenced exposure risk. This study provides valuable insight into the comprehension of the lagging pollution effects of PAH on the environment and human health after the e-waste site was rebuilt.

Environmental fate and health risks of polycyclic aromatic hydrocarbons in the Yangtze River Delta Urban Agglomeration during the 21st century

Understanding the spatiotemporal distribution and behavior of Polycyclic Aromatic Hydrocarbons (PAHs) in the context of climate change and human activities is essential for effective environmental management and public health protection. This study utilized an integrated simulation system that combines land-use, hydrological, and multimedia fugacity models to predict the concentrations, transportation, and degradation of 16 priority-controlled PAHs across six environmental compartments (air, water, soil, sediment, vegetation, and impermeable surfaces) within one of the world's prominent urban agglomerations, the Yangtze River Delta Urban Agglomeration (YRDUA), under future Shared Socio-economic Pathways (SSP)-Representative Concentration Pathways (RCP) scenarios. Incremental lifetime carcinogenic risk for adults and children exposed to PAHs were also evaluated. The results show a declining trend in PAHs concentrations and associated health risks during the 21st century. Land use types, hydrological characteristics, population, and GDP, have significant correlations with the fate of PAHs. The primary removal for PAHs is determined to be driven by advection through air and water. PAHs covering on impermeable surfaces pose a relatively higher health risk compared to those in other environmental media. This study offers valuable insights into PAHs pollution in the YRDUA, aiming to ensure public health safety, with the potential for application in other urban areas.

Investigation on molecular characteristics of organic compounds during a full-scale landfill leachate treatment process based on non-targeted analysis

In this study, a new methodology for evaluating full-scale landfill leachate treatment processes by non-targeted analysis using comprehensive two-dimensional gas chromatography quadrupole time-of-flight mass spectrometry (GC × GC-QTOF-MS) was proposed. The method revealed the chemical complexity of organic compounds in landfill leachate samples at the molecular level and evaluated the removal efficiency of the anaerobic-anoxic-oxic (A2O) - membrane bioreactor (MBR) - nanofiltration (NF) treatment process in conjunction with multi-level classification of organic compounds. Results showed that the results of non-targeted analysis combined with multi-level classification of organic compounds had a significant correlation with the conventional water quality parameters and can be used to evaluate the treatment process. A total of 2508 organic compounds were detected in 6 samples. 17 emerging contaminants (ECs) with known potentially hazards were detected, including Diisobutyl Phthalate (DIBP), which is toxic to male reproduction and development, and 4-Tert-Butylphenol, which causes endocrine disruption in animals. The removal rate of organic compounds by this full-scale landfill leachate treatment processes reached 79.14%. The anaerobic tank played a crucial role with 64.98% contribution. For compounds, the removal rate of heterocyclics was as high as 94.67%, and the removal rate of aliphatics was poor, only 63.49%. This treatment process had almost perfect removal effect on the steroids in alicyclics and phenols in aromatics, but poor treatment effect on saturated alkanes in aliphatics and naphthenes in alicyclics. This study provides a methodology for accurate assessment of the molecular level of treatment processes, new insights for process optimization in waste treatment plants, and data support for the detection of emerging contaminants. The environmental hazards of landfill leachate can be further evaluated in the future in conjunction with ecotoxicity assessment studies.

The past 40 years' assessment of urban-rural differences in Benzo[a]pyrene contamination and human health risk in coastal China

China has implemented many environmental regulations to battle against polycyclic aromatic hydrocarbon (PAH) contamination since the 1990s. It remains unclear how the exposure levels of PAHs changed quantitatively since reform and opening up in 1978 in China, whether the human health risks decreased or not, and how about the discrepancy between urban and rural areas. Here, taking Benzo[a]pyrene (BaP) in the rapidly urbanized Bohai region of China as a case, we used the improved Berkeley-Trent-Urban-Rural model to simulate the multimedia concentrations of BaP from 1980 to 2020 based on BaP emissions at a regional scale. The total emission of BaP in 1990 was the highest, with a value of 240 t, while the urban emission peaked in 2010. The BaP emissions from rural areas were two to seven times higher than urban areas, and the differences became smaller over time. Despite this, the average modeled BaP concentrations in urban air and soil were two to tens fold higher than in rural areas, particularly in highly urbanized or industrialized cities. Mostly, the concentrations of BaP in rural areas peaked in 1990, while those in urban areas peaked in 1990 or 2010. Early urbanized Beijing and Tianjin were the hot-spot cities of BaP contamination before 2000, while after 2010, higher concentrations were found in late industrialized Shandong and Hebei. BaP posed potential cancer risks to local residents, and air inhalation accounted for more than 80 % of the total risk. Under the stronger implementation of environmental regulations since the 1990s, it showed great health benefits, particularly for the urban residents in Beijing and Tianjin. The biggest decline in cancer risk was found in the period 2010-2020, and the average decreasing rates were 61.4 % and 57.4 % for urban and rural areas, respectively.

The ban on the sale of new petrol and diesel cars: Can it help control prospective marine pollution of polycyclic aromatic hydrocarbons (PAHs) in Shandong Province, China?

The constantly increasing amount of road vehicles causes massive exhaust emissions of pollutants, including polycyclic aromatic hydrocarbons (PAHs), necessitating a global responsibility to implement the policy of the ban on the sale of new petrol and diesel cars. Here, we assessed the policy control efficiency on marine pollution of PAHs in China through scenario modeling and prediction models, based on pollution monitoring, risk assessment, and source apportionment of PAHs in typical bays of Shandong Province. The results showed that in 2021, the pollution risk levels were relatively low (HI: 0.008-0.068, M-ERM-Q: 0.001-0.016, IBR: 1.23-2.69, ILCR: 8.11 ×10-6-1.99 ×10-5), and PAHs were mainly derived from traffic emissions (24.9%-35.2%), coal combustion (25.2%-32.9%), petroleum (17.2%-28.9%), and biomass combustion (17.6%-22.8%). In 2050, the predicted decrease of pollution risk values after the implementation of the policy was significant (12%-26%), and the gap between 2021 and 2050 was also significantly huge (18%-85%) without considering possible substitution of conventional energy. Collectively, this study built systematic approaches for assessing prospective marine pollution of PAHs. However, due to the particularity of Shandong Province, i.e., its national predominance of conventional energy consumption, the policy may be more effective when it comes to other coastal areas worldwide, calling for a larger scale research.

The effects of adsorbed benzo(a)pyrene on dynamic behavior of polystyrene nanoplastics through phospholipid membrane: A molecular simulation study

Nanoplastics (NPs) are mainly generated from the decomposition of plastic waste and industrial production, which have attracted much attention due to the potential risk for humans. The ability of NPs to penetrate different biological barriers has been proved, but the understanding of molecular details is very limited, especially for organic pollutant-NP combinations. Here, we investigated the uptake process of polystyrene NPs (PSNPs) combined with benzo(a)pyrene (BAP) molecules by dipalmitoylphosphatidylcholine (DPPC) bilayers by molecular dynamics (MD) simulations. The results showed that the PSNPs can adsorb and accumulate BAP molecules in water phase and then carried BAP molecules to enter DPPC bilayers. At the same time, the adsorbed BAP promoted the penetration of PSNPs into DPPC bilayers effectively by hydrophobic effect. The process of BAP-PSNP combinations penetrating into DPPC bilayers can be summarized into four steps including adhesion on the DPPC bilayer surface, uptake by the DPPC bilayer, BAP molecules detached from the PSNPs, and the PSNPs depolymerized in the bilayer interior. Furthermore, the amount of adsorbed BAP on PSNPs affected the properties of DPPC bilayers directly, especially the fluidity of DPPC bilayers that determine the physiologic function. Obviously, the combined effect of PSNPs and BAP enhanced the cytotoxicity. This work not only presented a vivid transmembrane process of BAP-PSNP combinations and revealed the nature of the effects of adsorbed benzo(a)pyrene on the dynamic behavior of polystyrene nanoplastics through phospholipid membrane, but also provide some necessary information of the potential damage for organic pollutant-nanoplastic combinations on human health at a molecular level.

Influence of temperature and precipitation on the fate of polycyclic aromatic hydrocarbons: simulation experiments on peat cores from a typical alpine peatland in Central China

The corresponding relationships between temperature, precipitation, and polycyclic aromatic hydrocarbon (PAH) concentration in a typical ombrotrophic peatland in Dajiuhu, Shennongjia, were quantitatively characterized by field sampling tests validated with simulation experiments. The PAH concentrations of peat cores in Dajiuhu peatland ranged from 262 to 977 ng·g^-1, with a mean value of 536 ± 284 ng·g^-1. PAHs were mainly composed of 2-3 ring PAHs, accounting for 31.7% ± 2.00% and 31.7% ± 5.00%, respectively. The concentration of PAHs in peat cores showed a significant decrease with increasing temperature, while the low molecular weight PAHs (LMW-PAHs) were more sensitive to temperature changes compared to the high molecular weight PAHs (HMW-PAHs). Besides, with the increase of quantity and velocity of leaching liquid, PAHs in peat were first transferred in the form of attached large-size particles and then gradually entered the aqueous phase. According to the IPCC projections of global warming, Dajiuhu peatland will release 956 ± 26.3 kg·°C^-1 PAHs into gas phase during 2030-2052, and a conservative projection based on local temperature trends showed that 459 ± 12.6 kg·°C^-1 PAHs will be released into gas phase by 2047 in Dajiuhu peatland. The projected release fluxes of PAHs in Dajiuhu peatland with precipitation volume and precipitation velocity are 381 ± 201 kg·100 mm^-1 and 1052 ± 167 kg·min·mL^-1, respectively, which are primarily from peat into particulate and aqueous phase.

Analysis of the multi-media environmental behavior of polycyclic aromatic hydrocarbons (PAHs) within Haizhou Bay using a fugacity model

In this study, we aimed to quantify the transport and fate of PAHs in different environmental phases (air, seawater, soil, sediment and fish), verify application of the Level III fugacity model in a bay simulation, and understand the transport and fate of PAHs in the bay environment on a macroscopic scale. The simulated average concentrations of ∑₁₆PAH in the air and soil (23.8 ng/m³ and 1080.91 ng/g, respectively), which is as a background reference data for the Haizhou Bay. In addition, the soil (307 t), fish (29.4 t), and sediment (9.72 t) phases were found to be important reservoirs in the Haizhou Bay. Emissions from road vehicles (658 t) accounted for the largest share of PAH emissions in the area, and atmospheric deposition contributed most to the input of PAHs to the polluted area in the region. Whereas the contribution of river runoff input was small, and degradation loss was the main output pathway.

Temporal-spatial variation, source forensics of PAHs and their derivatives in sediment from Songhua River, Northeastern China

The distribution patterns and health risk assessment of nitrated polycyclic aromatic hydrocarbons (NPAHs), hydroxy polycyclic aromatic hydrocarbons (OH-PAHs), and regular 16 priority polycyclic aromatic hydrocarbons (PAHs) in sediment from the Songhua River in northeastern China were investigated in this research. During dry seasons, concentrations of 16 USEPA priority PAHs, OH-PAHs, and NPAHs were extremely high, with average values of 1220 ± 288, 317 ± 641, 2.54 ± 3.98, and 12.2 ± 22.1 ng/g (dry weight, dw). The dry period level was confirmed to be 4 times greater than the wet period concentration. Modeling with positive matrix factorization (PMF) and estimation of diagnostic isomeric ratios were applied for identifying sources, according to the positive matrix factorization model: vehicle emissions (38.1%), biomass burning (25%), petroleum source (23.4%), and diesel engines source (13.5%) in wet season as well as wood combustion (44.1%), vehicle source (40.2%), coke oven (10.8%), and biomass burning (4.9%) in the dry season. The greatest seasonal variability was attributed to high molecular weight compounds (HMW PAHs). BaP was confirmed to be 81% carcinogenic in this study, which offers convincing proof of the escalating health issues.

Age- and sex-specific dermal exposure of polycyclic aromatic hydrocarbons in the general population of a city in south China

This study assessed the dermal exposure of population to polycyclic aromatic hydrocarbons (PAHs) in a South China city. Skin wipe samples of the face, hand, forearm, and shank were collected from 120 volunteers (50% male and 50% female) belonging to different age groups (preschooler, thresholder, middle-aged, and elderly). Concentrations of PAHs in the skin wipe samples varied from 18 to 27000 ng/m² in the order of face > hand > forearm > shank, regardless of age and gender. The PAH concentrations of bare skin locations were significantly higher in females than in males, while no significant differences were observed for clothing-covered skin locations between genders. The PAH concentrations for faces were significantly higher in the elderly compared to the other groups. The PAH composition was distinct between the four age groups. The dermal exposure levels of total PAHs and total BaP equivalent concentration (BaP_eq) varied from 25.6 to 620 and 0.093-37.4 ng/kg body weight/d, respectively. The dermal exposure levels of total PAHs were significantly higher in females than in males in all age groups except for the middle-aged group. The hand-mouth exposure doses were significantly higher in the preschoolers than in the other age groups. The values of the carcinogenic risk caused by dermal PAH exposure were between 3.5 × 10^-6 and 1.4 × 10^-3 with 29% of the population (35/120) having risk values exceeding significant levels (1 × 10^-4). The thresholder group exhibited the highest risk for PAH dermal exposure among all groups of the population. This study provides a comprehensive evaluation of the age- and gender-related risk of PAH through dermal exposure.

The effects of molecular weight and orientation on the membrane permeation and partitioning of polycyclic aromatic hydrocarbons: a computational study

Membrane permeation and the partitioning of polycyclic aromatic hydrocarbons (PAHs) are crucial aspects affecting their carcinogenicity and mutagenicity. However, a clear understanding of these processes is still rare due to the difficulty of determining the details experimentally. Here, the interactions between PAHs and lipid bilayers were studied by molecular simulations, mainly to check the influence of molecular weight and orientation. The liposome-water partition coefficient (K_LW), transmembrane time (τ), and permeability coefficient (P) of the PAHs were calculated by integrating free energy profiles from umbrella sampling. For selected PAHs, the membrane adsorption is a spontaneous process. The preferred location is near the CC bond and the orientation is related to the molecular structure. The P values of all the PAHs are basically the same order of magnitude, which means that the molecular weight contributes little to the process. As for K_LW and τ, they show obvious increases with different molecular weights. Unconstrained simulations showed that a flat orientation on the membrane surface would prevent PAHs from being transported through the membrane. Highly hydrophobic driving forces are not always good for the absorption of PAHs, especially the formation of aggregates. In addition, the orientations and energetic barriers of PAHs near the midplane of the lipid bilayer explain the different transitions of high- and low-weight PAHs. This work provides molecular level details relating to the interactions of PAHs with lipid membranes, with significance for understanding the health effects of PAHs.

Using a fugacity model to determine the degradation rate of typical polycyclic musks in the field: A case study in the North Canal River watershed of Beijing, China

To quantitate the degradation rate of 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-[g]-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene (AHTN) under field conditions, a level III fugacity model combined with a least-squares method was used to determine the degradation rate of HHCB and AHTN in the North Canal River watershed of Beijing, China. Model fitting, validation, sensitivity, and uncertainty analyses revealed that the established model was stable and robust. The degradation rates of HHCB and AHTN were 4.16 × 10^-3 h^-1 (t_1/2 = 167 h) and 1.68 × 10^-2 h^-1 (t_1/2 = 41.3 h), respectively. The calculated degradation rates were extrapolated to the Liangshui River, and indicated that the differences between the measured and predicted concentrations were less than 0.32 and 0.34 log units for HHCB and AHTN, respectively. The attenuation rates of HHCB and AHTN were calculated, and the results indicated that degradation was an important yet not the sole contributor to the degradation of the polycyclic musks. Results of uncertainty analyses indicated that the inflow and outflow concentrations of the polycyclic musks in the surface water of each segment strongly influenced the model outputs, followed by environmental factors (water depth and flow rate). It is essential to measure the degradation rate in the field because of the influence of the surrounding environment. The present study reveals the utility of fugacity models to quantify the degradation rate of organic micropollutants in the field.