Cross-interface transfer of polycyclic aromatic hydrocarbons (PAHs) in a shallow urban lake in Shanghai, China based on the fugacity model

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.

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.

Spatiotemporal distribution and inter-media transfer of polycyclic aromatic hydrocarbons in Shanghai, China: Historical patterns and future trends

Polycyclic Aromatic Hydrocarbons (PAHs) represent pervasive pollutants, posing health risks in urban environments. It is essential to comprehend the spatiotemporal distributions, composition profiles, and inter-media transfer processes of PAHs in various environmental compartments, influenced by both natural changes and anthropogenic activities. This study integrates historical and future spatiotemporally changing environmental parameters, including climate data, GDP, population data, land-use types, and hydrological variables, into the Multimedia Urban Model (MUM). This integration enables the simulation of spatiotemporal distributions and inter-media transfer fluxes of PAHs among six different media from the 2010s to the 2100s under two distinct Shared Socio-economic Pathways (SSP) scenarios in the megacity of Shanghai, China. The MUM model, featuring diverse gridded parameters, effectively captures PAH concentrations and movement across environmental compartments. Results indicate a decreasing trend in PAHs concentrations in the 2100s compared to the 2010s, with PAH concentrations in water, sediment, vegetation, and organic film covering impermeable surfaces under the SSP3-7.0 scenario higher than those of the SSP1-2.6 scenario. Low molecular weight PAHs dominate in the sediment, water, and air, whereas high molecular weight PAHs prevail in the organic film, vegetation, and soil. Sediment and soil serve as the predominant sinks for PAHs. The primary transport processes for PAH movement include air-film, air-soil, film-water, soil-air, and water-air. Almost all transfer fluxes exhibit a declining trend in future periods except for the air-film transport pathway. The principal input and removal routes for PAHs in Shanghai involve the advection of air and water. The study provides essential insights into the environmental behavior of PAHs and informs targeted pollution control in Shanghai. Additionally, it serves as a technical reference for similar pollution prediction research.

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.

Spatial and temporal variability and risk assessment of organophosphate esters in seawater and sediments of the Yangtze River estuary

Organophosphate esters (OPEs) as substitutes for PBDEs have been widely detected in the marine environment, while little is known about the pollution characteristics and variation of OPEs in estuarine environments with complex hydrodynamic conditions and land-based input. Yangtze River Estuary (YRE) is a typical highly urbanized and industrialized estuary, with a complex hydrological environment and geochemical behavior. This study found that the concentrations of OPEs in both seawater and sediments in the YRE were higher in spring than in summer. Alkyl OPEs were the first contributor, with TnBP and TiBP as the main components, where the contribution of alkyl OPEs had exceeded 75 % in both seawater and sediments in spring, and 60 % in summer seawater, and even 80 % in sediments. In spring, OPEs peaked in the central to southern region near the YRE. In summer, OPEs were mainly concentrated in the southern branch waterway and southern nearshore area of the YRE and showed a decreasing trend to the northeast. The OPEs in the sediments were mainly concentrated in the Yangtze River Mud Area (YREMA) and the Zhe-Min Coastal Mud Area (ZMCMA). Based on the fugacity model and principal component analysis, sediments could be released into the aquatic environment as an endogenous source, and exogenous sources were mainly municipal and industrial sewage discharge sources, urban and marine traffic discharge sources, and atmospheric deposition sources. The ecological risk analysis showed that the Σ14OPEs had exhibited a low to moderate ecological risk in the southern branch waterway and the south-central region offshore.

Optimizing the multimedia fate model for characterizing environmental risks of florfenicol in seasonally ice-covered reservoirs

Seasonally ice-covered reservoirs have both freeze-thaw and artificial regulation characteristics which could cause the accumulation of antibiotics. Florfenicol, one of the most widely used veterinary antibiotics, with an environmental persistence due to its fluorinated substituents has been detected in the suburban drinking water source reservoirs. In this study, a four-level fugacity model that is appropriate for ice-water-sediment systems was developed to predict the fate of florfenicol and assess its ecological risk in seasonally ice-covered reservoirs. The effects of freeze-thaw and artificial regulation processes on the volume variation of ice and water were considered by the model. The simulation accuracies in ice and water in the model were improved by 3.9% and 17.7%, respectively, compared with the traditional model. The results of mass transfer analysis showed that the inflow of florfenicol in tributaries and the volume variation of ice and water were the major factors influencing the concentration variation of florfenicol in the seasonally ice-covered reservoir. Additionally, ecological risk analysis showed that the values of risk quotients ranged from 0.019 to 0.038 which was consistently at a low ecological risk level. Our findings provide a modeling tool for predicting the fate of antibiotics with persistence and assessing their ecological risks in seasonally freeze-thaw reservoirs in cold regions.

Concentration levels, spatial variations and exchanges of polychlorinated biphenyls (PCBs) in ambient air, surface water and sediment in Bursa, Türkiye

In this study, ambient air, surface water and sediment samples were simultaneously collected and analyzed for PCBs to investigate their levels, spatial variations and exchanges between these three compartments at different sampling sites for 12 months in Bursa, Türkiye. During the sampling period, a total of 41 PCB concentrations were determined in the ambient air, surface water (dissolved and particle phase) and sediment. Thus, 945.9 ± 491.6 pg/m³ (average ± STD), 53.8 ± 54.7 ng/L, 92.8 ± 59.3 ng/L and 71.4 ± 38.7 ng/g, respectively. The highest concentrations of PCBs in the ambient air and in water particulate phase were measured at the industrial/agricultural sampling site (1308.6 ± 252.1 pg/m³ and 168.7 ± 21.2 ng/L, respectively), ∼ 4-10 times higher than background sites; while the highest concentrations in the sediment and dissolved phase were measured at the urban/agricultural sampling sites (163.8 ± 27.0 ng/L and 145.7 ± 15.3 ng/g, respectively), ∼ 5-20 times higher than background sites. PCB transitions between ambient air-surface water (f_A/f_W) and surface water-sediment (f_W/f_S) were investigated by fugacity ratio calculations. According to the fugacity ratios obtained, volatilization from the surface water to the ambient air was observed at all sampling sites (98.7 % of f_A/f_W ratios are <1.0). Additionally, it has been determined that there is a transport from the surface water to the sediment (100.0 % of f_W/f_S ratios are higher than 1.0). The flux values in ambient air-surface water and surface water-sediment environments ranged from -1.2 to 1770.6 pg/m²-day and from -225.9 to 0.001 pg/m²-day, respectively. The highest flux values were measured for PCBs with low chlorine content (Mono-, Di-Cl PCBs), while the lowest flux values were measured for the high chlorine content PCBs (Octa-, Nona- and Deca-Cl PCBs). As it was determined in this study that surface waters contaminated by PCBs have the potential to pollute both air and sediments, it will be important to take measures to protect surface waters.

A method for simulating spatial fates of chemicals in flowing lake systems: Application to phthalates in a lake

In order to describe spatio-temporal distribution of chemicals in flowing lake systems, a dynamic multimedia fate model of chemicals with spatial differentiation was constructed by coupling the level IV fugacity model with lake hydrodynamics. It was successfully applied to four phthalates (PAEs) in a lake recharged by reclaimed water and its accuracy was verified. Results show that under the long-term influence of flow field, the distributions of PAEs in both lake water and sediment have significant spatial heterogeneity of 2∼5 orders of magnitude, but present different distribution rules, which was explained by analysis of PAE transfer fluxes. The spatial distribution of PAEs in the water column depends on hydrodynamic conditions and whether the primary source is reclaimed water or atmospheric input. Slow water exchange and flow speed promote the migration of PAEs from water to sediment, causing them to always accumulate in sediments far away from the recharging inlet. Uncertainty and sensitivity analysis show that the PAE concentrations in water phase are mainly affected by emission and physicochemical parameters, while those in sediment phase are also sensitive to environmental parameters. The model can provide important information and accurate data support for the scientific management of chemicals in flowing lake systems.

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.

Fate of phthalates in a river receiving wastewater treatment plant effluent based on a multimedia model

Phthalic acid esters (PAEs) can enter environment media by secondary effluent discharge from wastewater treatment plants (WWTP) into receiving rivers, thus posing a threat to ecosystem health. A level III fugacity model was established to simulate the fate and transfer of four PAEs in a study area in Tianjin, China, and to evaluate the influence of WWTP discharge on PAEs levels in the receiving river. The results show that the logarithmic residuals of most simulated and measured values of PAEs are within one order of magnitude with a good agreement. PAEs in the study area were mainly distributed in soil and sediment phases, which accounted for 84.66%, 50.26%, 71.96% and 99.09% for dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), respectively. The upstream advection accounted for 77.90%, 93.20%, 90.21% and 90.93% of the total source of DMP, DEP, DBP and DEHP in the river water, respectively, while the contribution of secondary effluent discharge was much lower. Sensitivity analysis shows that emission and inflow parameters have greater influences on the multimedia distributions of PAEs than physicochemical and environmental parameters. Monte Carlo analysis quantifies the uncertainties and verifies the reliability of the simulation results.

Fugacity-based analysis of polycyclic aromatic hydrocarbon pollution in Izmit Bay, Turkey: An analytical framework for assessment with limited data

An analytical framework was proposed for analyzing long-term chemical pollution in a coastal region with limited environmental data. The framework consists of compiling and synthesizing the available knowledge including the chemical's properties and the environmentally relevant data, as well as the data obtained by past monitoring studies. The gathered data is analyzed to assess multimedia fate of the pollutant by using fugacity-based intermedia transport calculations. Uncertainty analysis by applying Monte Carlo simulations is an integrated part of the framework. Dispersion factor (k) values were adopted, enabling a unified and intuitive way to define lognormal uncertainty distributions. The proposed framework was applied to polycyclic aromatic hydrocarbon (PAH) pollution in Izmit Bay, a coastal region in Turkey, impacted by industrialization and population growth. The analysis showed the importance of atmospheric pollution as a PAH source and indicated that Izmit Bay sediments may be at steady state for most PAHs.

Occurrence of synthetic musks in the sediment-seawater system of the Yellow Sea and East China Sea during wet and dry seasons

Synthetic musks are aroma compounds used worldwide as substitutes for natural musks, which have become ubiquitous pollutants in the environment. The land-based input and partition behavior of synthetic musks in sediments and seawater are important for understanding their fate in the marine environment. In this study, a total of 292 seawater and sediment samples from 146 sites of the Yellow Sea and East China Sea were collected during wet and dry seasons and used to determine four synthetic musks, tonalide, galaxolide, musk xylene and musk ketone. Only tonalide was detectable in 10.6% and 17.8% of seawater samples at a concentration range of 23.7-38.2 ng/L and 19.0-24.8 ng/L in wet season and dry season, respectively. In sediments, both galaxolide and tonalide were detectable, with a sum total synthetic musks concentration ranging from 1.4 to 36.6 ng/g dry weight (dw) in wet season and 1.0 to 14.1 ng/g dw in dry season. The concentration of tonalide in seawater was significantly higher in wet season than in dry season and the concentration of synthetic musks in sediments of some coastal areas also exhibited higher concentrations in wet season than in dry season. Fugacity analysis showed that tonalide in the Yellow Sea exhibited a trend of diffusion from sediment to seawater or a state of equilibrium, while no diffusion trend was observed in the East China Sea. The hazard quotient values for tonalide and galaxolide in sediment and seawater samples were lower than 0.1, indicating that they present a low ecological risk. This research provides novel insights that help understand the pollution status, diffusion behavior and ecological risk of synthetic musks in marine environments.

Modeling multimedia fate and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the coastal regions of the Bohai and Yellow Seas

Using an improved multimedia fate model, this study simulated the spatial distributions, partitioning behaviors, and mass exchanges of PAH₁₆ (16 species with priority by the USEPA) in multiple environmental compartments in the coastal regions of the Bohai and Yellow Seas, Northern China. The model predictions generally matched well with the measured results, as the deviations of most points were within one order of magnitude in the air, freshwater, and 3 soil compartments. The estimated concentrations of ΣPAH₁₆ in the northern part were higher than those in the southern part, which was consistent with the emissions of each part. Approximately 97.6% of the ΣPAH₁₆ mass was distributed in soils; therefore, soils served as the dominant sink of PAH₁₆. The estimated net flux of ΣPAH₁₆ from air to soil ranged from 0.4 to 10.7 mg/m²/year (an average of 3.2 mg/m²/year), and the estimated flux of deposition from air to soil fell in the range of 0.4-10.8 mg/m²/year (an average of 3.2 mg/m²/year), which served as the dominant process at the air-soil interface. The estimated net flux of ΣPAH₁₆ from air to freshwater ranged from -15.3 to 9.4 mg/m²/year (an average of -0.3 mg/m²/year), and the reversed volatilization flux from freshwater to air ranged from 0.01 to 21.1 mg/m²/year (an average of 3.7 mg/m^2/year). This situation indicated notable spatial variations and volatilization as the main process affecting the direction of net flux at the air-freshwater interface. Deterministic risk assessment and probabilistic risk assessment were conducted. The overall health risks of the studied regions were acceptable, while the excess lifetime cancer risk (ELCR) by air inhalation was greater than that by soil ingestion. CAPSULE: Multimedia fate model-predicted distributions and compositions of PAH₁₆ in different compartments, compartmental exchange fluxes and directions, and deterministic and probabilistic ELCR via different exposure pathways were assessed.

Nanoplastic State and Fate in Aquatic Environments: Multiscale Modeling

We now know that nanoplastics can harm aquatic organisms, but understanding ecological risk starts with understanding fate. We coupled population balance and fugacity models to predict the conditions under which nanoplastics remain as single particles, aggregate, or sediment and to predict their capacity to concentrate organic pollutants. We carried out simulations across a broad range of nanoplastic concentrations, particle sizes, and particle-particle interactions under a range of salinity and organic matter conditions. The model predicts that across plastic materials and environmental conditions, nanoplastics will either remain mostly dispersed or settle as aggregates with natural colloids. Nanoplastics of different size classes respond dissimilarly to concentration, ionic strength, and organic matter content, indicating that the sizes of nanoplastics to which organisms are exposed likely shift across ecological zones. We implemented a fugacity model of the Great Lakes to assess the organic pollution payload carried by nanoplastics, generating the expectation that nanoplastics would carry nine times more pollutants than microsized plastics and a threshold concentration of 10 μg/L at which they impact pollutant distribution. Our simulations across a broad range of factors inform future experimentation by highlighting the relative importance of size, concentration, material properties, and interactions in driving nanoplastic fate in aquatic environments.

Shift in the distribution and fate of perfluoroalkyl acids by sluice gates in the multi-environment media of rivers

The impact of sluice operations on the distribution and fate of perfluoroalkyl acids (PFAAs) remains poorly understood. In this study, the distribution of PFAAs was investigated in water, suspended particles, sediment, and pore water from the upstream and downstream sections of six sluice gates along the Wangyu River, China. The target PFAAs were widely distributed in the dissolved phase (∑PFAAs: 447.61 ± 180.26 ng/L), particle phase (∑PFAAs: 2040.95 ± 1870.88 ng/g dw), sedimentary phase (∑PFAAs: 39.42 ± 35.38 ng/g dw), and pore water phase (∑PFAAs: 8172.54 ± 4278.60 ng/L). Our data suggest predominant detections of short-chain PFAAs such as perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA) in the four environmental media. Sediment pore water appeared as an essential repository and potential source for PFAA re-release to the river environment. The levels of PFAAs in the dissolved and suspended particle phase upstream of the sluices were significantly lower than those downstream, while the situation in the sediment and pore water phase was the opposite. Sluice operation caused PFAA redistribution among the multi-environment media but did not change the PFAA composition, which had the significant effect on the partition behavior of perfluoroalkyl carboxylic acids (PFCAs) between particles and water, as well as changed the migration pattern of PFOA, PFNA and PFOS from equilibrium to the migration state. Quantitative prediction models were developed for simulating fate of PFAAs in gate-controlled river, and the major factors affecting the distribution and fate of PFAAs were identified. Our findings provide insights into the redistribution mechanisms of PFAAs and an understanding of their environmental fate.

Long-Term Exposure to Phenanthrene Induced Gene Expressions and Enzyme Activities of Cyprinus carpio below the Safe Concentration

Phenanthrene (PHE) is a typical compound biomagnified in the food chain which endangers human health and generally accumulates from marine life. It has been listed as one of the 16 priority PAHs evaluated in toxicology. In order to evaluate the changes of CYP1A GST mRNA expression and EROD GST enzyme activity in carp exposed to lower than safe concentrations of PHE. Long-term exposure of carp to PHE at lower than safe concentrations for up to 25 days. The mRNA expression level and cytochrome P450 (CYP1A/EROD (7-Ethoxylesorufin O-deethylase)) and glutathione S-transferase (GST) activity were measured in carp liver and brain tissue. The results showed that PHE stress induced low-concentration induction and high-concentration inhibition of CYP1A expression and EROD enzyme activity in the liver and brain of carp. In both two organs, GST enzyme activity was also induced. However, the expression of GST mRNA was first induced and then inhibited, after the 15th day. These results indicate that long-term exposure to PHE at lower than safe concentrations still poses a potential threat to carp’s oxidase system and gene expression.

Presence of polycyclic aromatic hydrocarbons among multi-media in a typical constructed wetland located in the coastal industrial zone, Tianjin, China: Occurrence characteristics, source apportionment and model simulation

In-depth understanding and accurately predicting the occurrence and fate of polycyclic aromatic hydrocarbons (PAHs) in constructed wetlands (CWs) is extremely crucial for optimizing the CWs construction and strengthening the risk control. However, few studies have focused on the PAHs among sediment-water-plant and model simulation in CWs. In this study, sediment, surface water and reed samples were gathered and analyzed from a typical CW. The concentrations of 16 PAHs (Σ₁₆PAHs) in sediments, surface water and reeds ranged from 620 to 4277 μg/kg, 114 to 443 ng/L and 74.5 to 362 μg/kg, respectively. The coefficients of variation (CV) were calculated as 0.796, 0.431 and 0.473 for the above three media respectively, indicating that the spatial distribution variation was medium intensity. The fugacity fraction (ff) suggested that sediments might act as the secondary release source of most PAHs. According to the diagnostic ratios and principal component analysis-multiple linear regression (PCA-MLR), PAHs in this CW mainly come from fossil fuels combustion and petroleum leakage. PAHs in sediments showed high ecological risk at water inlet and moderate risk at the other functional zones, while low risks for surface water at all functional zones. Although the human health risk assessment indicated relatively low cancer risk, the health risk still cannot be ignored with the continuous input and accumulation of exogenous PAHs. A mathematical model covering the hydraulics parameters and composition characteristics of the wetland was established, and its reliability was verified. The simulated results obtained by the established model were basically consistent with the measured values. In addition, the total remove efficiency of PAHs in surface water was 40.2%, which calculated by the simulated model. This work provides helpful insight into the comprehension of occurrence and fate of PAHs among multi-media in CWs.

Application of a fugacity model to estimate emissions and environmental fate of ship stack PAHs in Shanghai, China

The understandings of environmental activities and regional inventory of ship stack PAHs are very limited in Shanghai due, in part, to the lack of source-segregated analysis. To address this, measured PAHs in organic film on ship surfaces were employed to reconstruct concentrations in various compartments through a fugacity model to investigate the level, transport, fate and annual emission of ship stack PAHs in Shanghai. The results revealed that ship stack PAHs results in 11.2-181 ng L^-1 and 71.0-1710 ng g^-1 in water and sediment of Shanghai, respectively. After being released into air, ship stack PAHs mainly concentrated in organic films and sediments while sunk in water and sediment. Crucial mass transfer pathways include deposition of airborne and sediment PAHs. The mass loss of ship stack PAHs was primarily through air advection, followed by degradation in sediment. The ship emissions (53.7 tons annually) accounted for approximate one tenth of the regional total in Shanghai (in 2017). Additionally, shipping was estimated to release 127 tons of PAHs annually into the Shanghai section of Yangtze River. Our results suggest our fugacity-based approach can be used to estimate the regional emissions and inventory of ship stack PAHs in the surrounding environment.

Unraveling interfacial properties of organic-coated marine aerosol with lipase incorporation

Marine aerosols are believed to have an organic surface coating on which fatty acids act as an important component due to their high surface activity. In addition, various kinds of enzyme species are abundantly found in seawater, some of which have been identified to exist in marine aerosols. Herein, from the perspective of marine aerosol interface simulation, we investigate the effect of Burkholderia cepacia lipase on the surface properties of stearic acid (SA) monolayer at the air-water interface by using surface-sensitive techniques of Langmuir trough and Infrared reflection-absorption spectroscopy (IRRAS). Our findings indicate that the stearic acid film undergoes a significant expansion, especially when the lipase concentration is 500 nM, because of the incorporation of lipase as observed from the surface pressure-area (π-A) isotherms. IRRAS spectra also show reduced intensities and ordering in the methylene stretching vibration region of stearic acid as a result of low surface density and disordered packing as the enzyme concentration increases. In particular, when the concentration of lipase is 500 nM, the lowest I_as/I_s values are shown on both pure water subphase and artificial seawater subphase, indicating more gauche conformations for SA. Furthermore, SA films with lipase incorporation were also studied at three different pH of subphase environment, considering the decrease of pH caused by the reaction with acidic gases during the aerosol aging process. The results reflect a more pronounced expansion of SA monolayer in acidic environment at pH 2.5, suggesting that hydrophobic interaction plays an important role in the disorder of the SA monolayer. In view of the coexistence of fatty acids and enzymes in the marine environment, this study provides a further understanding of the surface organization and behavior of organic-coated marine aerosols and deepen the knowledge of lipid-enzyme interfacial interactions occurring in the atmosphere.

Fate of polycyclic aromatic hydrocarbons in the Pacific sector of the Arctic Ocean based on a level III fugacity environmental multimedia model

The sink-source controversy for global polycyclic aromatic hydrocarbons (PAHs) in high-latitude seas is extremely concerning. A level III fugacity model was developed for the southern Chukchi Sea to estimate the fate of 16 priority PAHs. The model results indicate large losses were due to seawater advection outflow, followed by degradation in seawater. The Chukchi Sea serves as a source of 4 PAHs (i.e., Nap, Ace, Acp and Fl) in the atmosphere and sediment but acts as a final sink for the other 12 PAHs. The water-air diffusion flux and wet deposition flux play dominant roles in the total transfer flux of the 4 PAHs and the other 12 PAHs, respectively. The source/sink role that high-latitude seas play in PAH distribution has changed under the influence of global climate change. The model proposed in this study provides an approach to support further study of the fate of PAHs in high-latitude seas.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in the sediments of Daihai Lake in Inner Mongolia, China

Polycyclic aromatic hydrocarbons (PAHs) are typical toxic organic pollutants that can accumulate in sediments and may be toxic to aquatic organisms. In the present study, the contamination level, composition pattern, and sources of sixteen PAHs listed by the United States Environmental Protection Agency were investigated in surface sediments and a sediment core from Daihai Lake, which is located in a typical semiarid area of Inner Mongolia, China, and the ecological risk of these PAHs was assessed. The results show that the total concentration of PAHs in the surface sediments ranged from 204.6 to 344.5 ng/g with an average value of 287.2 ng/g and that compared with other aquatic systems, the level of PAHs in the sediments from Daihai Lake was low. However, a general upward trend was observed for the concentrations of PAHs in the sediment core, which might be related to the increase in human activities in the area. Moreover, the PAH concentrations were significantly positively correlated with the total organic carbon (TOC) content in the sediments, and it is thus inferred that TOC regulates the distribution of PAHs in Daihai Lake. Three-ring and four-ring PAHs were found to be predominant in all the sediment samples, and phenanthrene (Phe) was the most abundant compound. According to the composition of PAHs and the anthracene (Ant)/(Ant+Phe) or fluoranthene (Flt)/(Flt+pyrene (Pyr)) ratios, the PAHs in Daihai Lake mainly originated from the combustion of domestic coal, grass, and wood, and petroleum cannot be ignored as a source considering the growth of industry. Risk assessment based on a comparison of PAH concentrations and the effect range low (ERL) and effect range median (ERM) values demonstrated that acenaphthene (Ace) at 11 sites and fluorene (Flu) at 7 sites had occasional adverse biological effects.