Input Of Polycyclic Aromatic Hydrocarbons Research Articles

Sedimentary records of polycyclic aromatic hydrocarbons and organochlorine pesticides to reconstruct anthropogenic activities in Lake Issyk-Kul region (Kyrgyzstan), and their effects on the lake environment

Vertical distributions of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in a sediment core from Lake Issyk-Kul are powerful tools for reconstructing historical anthropogenic activities over the past 350 years. Four periods were identified according to the variations in these environmental proxies. Period Ⅰ (1670s–1800s) corresponds to a phase of limited anthropogenic activity reflected by the lowest ΣPAH16 concentrations, mainly from biomass combustion and petrogenic processes. Along with pronounced deforestation due to wildfires documented in the pollen record, a similar decrease in PAHs suggests that PAHs were most likely generated by natural sources around Lake Issyk-Kul during this period. Period Ⅱ (1800s–1930s) reflects increasing agricultural activities with fluctuations in various PAH concentrations. Anthropogenic biomass-derived PAH inputs from agricultural activities gradually replaced natural inputs to Lake Issyk-Kul, coinciding with several historical events. However, natural factors still mainly controlled changing lake levels before the 1930s. Period Ⅲ (1930s–1970s) corresponds to rapid development of agricultural activities, inferred by slight increases in ΣPAH16 concentrations dominated by coal-derived PAHs and a considerable increase in ΣOCP18 concentrations. Concentrated agricultural activities around Lake Issyk-Kul significantly influenced environmental changes in grain size and water level in the lake. Period Ⅳ (post-1970 s) corresponds to intensive industrial and urban activities, including a 10-year economic depression (1990s–2000s), characterized by the highest ΣPAH16 concentrations mainly from petroleum combustion followed by a sharp drop after the 1990s as the dissolution of the Soviet Union. Industrialization and urbanization in study area have changed the trophic state of Lake Issyk-Kul, particularly in recent years. Climate change has also induced “lateral remobilization” of contaminants, increasing pollution levels in this mountain lake.

Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments of the East China marginal seas: Significance of the terrestrial input and shelf mud deposition

To investigate the distribution, sources, influencing factors, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in East China Marginal Seas (ECMSs) sediments, we measured the concentrations of 16 PAHs in 104 surface sediment samples collected from the ECMSs in 2014 and 2016. Total PAH concentration (∑PAHs) ranged from 4.49 to 163.66 ng/g dry weight (dry w), with 65.98 ± 33.00 (mean ± SD) ng/g dry w. The highest PAH concentrations and total organic carbon were observed in areas with fine-grained sediments in the Bohai Sea (BS), Yellow Sea (YS), and coastal East China Sea (ECS), indicating the prominent influence of regional hydrodynamics and sediment properties. The dominant PAH congener in BS and YS was BbF, whereas coastal ECS was Phe. The heterogeneity of PAH sources implies that terrestrial PAH input and shelf mud deposition have crucial roles in the source–sink processes of PAHs in a strongly human-influenced marginal sea.

Occurrence and Sources of Polycyclic Aromatic Hydrocarbons and Factors Influencing Their Accumulation in Surface Sediment of a Deep-Sea Depression, Namely, the Tatar Trough (Tatar Strait, the Sea of Japan)

The concentrations of 14 polycyclic aromatic hydrocarbons (PAHs) in the sediment of the Tatar Trough were studied. Despite the increase in PAH concentrations over recent decades, which is likely the result of the handling and transportation of fossil fuels, PAH levels and ecological risk were found to be low. The spatial pattern revealed that higher PAH concentrations were mainly in the deeper water sites, suggesting that trough slope failure transported the PAHs to the deeper part of the basin. There was no correlation between the PAHs and grain size or the PAHs and organic carbon that is related to the PAH input from a variety of sources and the heterogeneity of organic matter. The PAH composition, isomer ratio, and PCA identified two areas with different PAH sources. The most northern part of the Tatar Trough received petrogenic PAHs that are probably transported downslope from the northern Tatar Strait where fossil fuels are handled in some ports. Another trough part was polluted by the PAHs from the combustion of coal and biomass and the exhaust of marine vehicles. The minor presence of genes responsible for aerobic PAH destruction can be explained by the anaerobic degradation of PAHs or the spontaneous creation of favorable conditions that promote bacterial PAH oxidation.

Spatial distribution and partition of polycyclic aromatic hydrocarbons (PAHs) in the water and sediment of the southern Bohai Sea: Yellow River and PAH property influences

The marginal Bohai Sea, connected to the northwestern Pacific Ocean, is threatened by human activity. The Yellow River, the second largest river in China, drains large amounts of water, silts, and polycyclic aromatic hydrocarbons (PAHs) into the southern Bohai Sea; however, to what extent the Yellow River inputs influence the spatial distributions and partitions of PAHs in the southern Bohai Sea is not well known. Therefore, this study collected surface water, bottom water, and sediment samples from the southern Bohai Sea and analyzed them to examine the spatial distributions and partitions of 15 priority PAHs. The results showed that PAH concentrations ranged from 26.9 to 50.1 ng L–1 in surface water, 18.8 to 44.1 ng L–1 in bottom water, and 7.4 to 143.9 ng g–1 in sediment, with higher proportions of four-, five-, and six-ring PAHs in sediment than in water. PAH inputs from the Yellow River and sea coastal currents determined the spatial distribution of PAH concentrations in water and sediment, with an overall decrease from the estuary to the southeast. However, the solid dilution effect of input silts from the Yellow River and the liquid dilution effect of water from the Yellow River and Yellow Sea led to lower PAH concentrations in the water and sediment of the southern Bohai Sea than those in other areas of the Bohai Sea. PAH exchange between the atmosphere and seawater led to significantly higher individual PAH concentrations (except for acenaphthylene) in the surface water than in the bottom water, with ratios significantly related to the PAH n-octanol-water partition coefficient, organic carbon-water partition coefficient, and Henry's law constants. These parameters also determined PAH partitioning between the bottom water and sediment. Individual and total PAH concentrations in the sediment were significantly correlated with organic matter, clay, and silt contents. Therefore, the partitions and spatial distributions of PAHs in the southern Bohai Sea comprehensively depend on PAH properties, PAH inputs from the Yellow River and the atmosphere, sea currents, and seawater and sediment properties. The ecological risks posed by individual PAHs in both water and sediment were negligible or acceptable.

Sedimentary records of contaminant inputs in Frobisher Bay, Nunavut

Contaminants, such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), heavy metals, and per and polyfluoroalkyl substances (PFASs), primarily reach the Arctic through long-range atmospheric and oceanic transport. However, local sources within the Arctic also contribute to the levels observed in the environment, including legacy sources and new sources that arise from activities associated with increasing commercial and industrial development. The City of Iqaluit in Frobisher Bay, Nunavut (Canada), has seen rapid population growth and associated development during recent decades yet remains a site of interest for ocean protection, where Inuit continue to harvest country food. In the present study, seven dated marine sediment cores collected in Koojesse Inlet near Iqaluit, and from sites in inner and outer Frobisher Bay, respectively, were analyzed for total mercury (THg), major and trace elements, PAHs, PCBs, and PFASs. The sedimentary record in Koojesse Inlet shows a period of Aroclor 1260-like PCB input concurrent with military site presence in the 1950–60s, followed by decades of input of pyrogenic PAHs, averaging about ten times background levels. Near-surface sediments in Koojesse Inlet also show evidence of transient local-source inputs of THg and PFASs, and recycling or continued slow release of PCBs from legacy land-based sources. Differences in PFAS congener composition clearly distinguish the local sources from long-range transport. Outside Koojesse Inlet but still in inner Frobisher Bay, 9.2 km from Iqaluit, sediments showed evidence of both local source (PCB) and long-range transport. In outer Frobisher Bay, an up-core increase in THg and PFASs in sediments may be explained by ongoing inputs of these contaminants from long-range transport. The context for ocean protection and country food harvesting in this region of the Arctic clearly involves both local sources and long-range transport, with past human activities leaving a long legacy insofar as levels of persistent organic pollutants are concerned.

Polycyclic aromatic hydrocarbon dynamics in soils along proglacial chronosequences in the Alps

Polycyclic aromatic hydrocarbons (PAHs) were studied in the soils of three proglacial areas in France (Noir and Chardon Glaciers) and Italy (Miage Glacier). PAH contents, PAH stocks and PAH contents normalized to the total organic carbon contents (PAHs/TOC ratio) were investigated along proglacial soil chronosequences to infer their evolutions with soil age (from 3 to 4200 years), where the PAH contamination was only related to long-range atmospheric transport. Evolutions of PAH and TOC contents, PAHs/TOC ratio and PAH stock were fitted with exponential and logarithmic relations. For the three proglacial areas, PAH contents increased rapidly during the first 150 years of soil development, ranged from 4 to 152 ng·g−1, and showed a strong relationship with total organic carbon (TOC) contents (r = 0.83, p < 0.05). The joint increase of PAH and TOC contents suggested that PAH accumulation in soils were not only driven by PAH inputs but also by the capacity of soils to store these contaminants. PAH contents in the oldest soils (from 1200 BCE and 2200 BCE) were similar than for soils from 1850 CE. The period 1850–2019 CE corresponded to a decrease in the PAHs/TOC ratio suggesting both a faster accumulation of TOC than PAHs and a dilution effect of PAHs already present in soils. For the oldest soils, the PAHs/TOC ratio appeared similar to those for soils from 1850 CE, with values ranging from 0.48 to 2.06 ng·mg−1, suggesting an equilibrium between both parameters for soils older than 170 years. Finally, PAH stocks ranged from 0.41 mg·m−2 to 6.80 mg·m−2 in the youngest and oldest soils, respectively. These results do not allow us to identify the same period of greatest emission as other studies (estimated ~1960), but they revealed changes in the capacity of soils to store these pollutants.

Seasonal variation, spatial distribution, and sources of PAHs in surface seawater from Zhanjiang bay influenced by land-based inputs

This study was carried out for a comprehensive understanding of the concentrations, seasonal variation, spatial distribution, sources, and land-based inputs of polycyclic aromatic hydrocarbons (PAHs) in surface seawater from Zhanjiang Bay (ZJB). Although the PAHs were ubiquitous, their concentrations were relatively low, and significant seasonal trends and spatial distributions were observed. Based on the diagnostic ratios and composition profiles, the PAHs found in this study mainly originated from coal/biomass burning, and petroleum and its combustion played an important role in the wet seasons. Furthermore, the PAHs from land-based inputs had seasonal variations, spatial distributions, sources, and composition profiles similar to those in ZJB seawater. By combining the cases of energy structure, residential and industrial layouts, maritime traffic, and activities related to ports and mariculture, this study concluded that PAHs in ZJB seawater are greatly influenced by land-based inputs, atmospheric deposition and human activities.

Polycyclic aromatic hydrocarbons (PAHs) in air, foliage, and litter in a subtropical forest: Spatioseasonal variations, partitioning, and litter-PAH degradation

Forest canopies play a vital role in scavenging airborne semi-volatile organic compounds. The present study measured polycyclic aromatic hydrocarbons (PAHs) in the understory air (at two heights), foliage, and litterfall in a subtropical rainforest (the Dinghushan mountain) in southern China. ∑17PAH concentrations in the air ranged from 2.75 to 44.0 ng/m3 (mean = 8.91 ng/m3), showing a spatial variation depending on the forest canopy coverage. Vertical distributions of the understory air concentrations also indicated PAH inputs from the above-canopy air. The concentrations of PAHs in fresh litter (with a mean of 261 ± 163 ng/g dry weight (dw)) were slightly lower than those in the foliage (362 ± 291 ng/g dw). Unlike the stable air PAH concentrations for most of the time of the year, the temporal variations of foliage and litter concentrations were remarkable but generally similar. Higher or comparable leaf/litter-air partition coefficients (KLA) in fresh litter compared with living KLA in leaves suggest that the forest litter layer is an efficient storage media for PAHs. Degradation of three-ring PAHs in litter under the field conditions follows first-order kinetics (R2 = 0.81), while the degradation is moderate for four-ring PAHs and insignificant for five- and six-ring PAHs. The yearly net cumulative deposition of PAHs through forest litterfall in the whole Dinghushan forest area over the sampling year was about 1.1 kg, 46% of the initial deposition (2.4 kg). This spatial variations study provides the results of in-field degradation of litter PAHs and makes a quantitative assessment of the litter deposition of PAHs, deducing their residence dynamics in the litter layer in a subtropical rainforest.

Modeling the long-term fate of polycyclic aromatic hydrocarbons (PAHs) and public health risk in Bohai Bay Sea Area, China

The target of this study was to reconstruct the historical concentration, distribution, variation, and exposure risk evaluation for EPA PAHs to the whole sea of Bohai Bay and the coastal population, by employing a specific dynamic multimedia model during 1950–2050. The unsteady-state model, driven by temporal energy activities from 1950 and sustainable scenarios based on socioeconomic development, indicated the annual emission increased by 4.6 times (from 84.8 tons to 391 tons) until 2020 and resulted in concentrations up to 5.2 times in the atmospheric compartment, and 4.9 times in seawater. Two peak concentrations in 1997 and 2014, consistent with total PAHs input revealed significant regional anthropogenic input in northern Bohai Bay (Tianjin) and southern Bohai Bay (Hebei). The peak-to-peak values of the timing concentration revealed a notably alternative increase in the south (+109.4 %–128.6 %), instead of the rapid decline in the north (−21.5 %–44.5 %). The dominant processes at air-seawater interfaces were air-seawater molecular transfer (from 38.4 % to 51.8 %), and wet deposition (from 60.5 % to 47.5 %). Under 5 shared socioeconomic pathways, the optimal scenario (SSP1) achieved a 24.7 % emission decline, an atmospheric decrease of 15.1 %–31.1 %, and 24.8 %–41.2 % mitigation in seawater during 2020–2050, and each pathway exhibited a general lessening concave in the northern developed municipality, compared with convex in the southern developing regions. The inhalation risk assessment evaluated 10 generations living on Bohai Bay coasts, with an acceptable result, while the current sustainable conceive was with meager fruition in reducing risk.

Snow-Dependent Biogeochemical Cycling of Polycyclic Aromatic Hydrocarbons at Coastal Antarctica.

The temporal trend of polycyclic aromatic hydrocarbons (PAHs) in coastal waters with highly dynamic sources and sinks is largely unknown, especially for polar regions. Here, we show the concurrent measurements of 73 individual PAHs and environmental data, including the composition of the bacterial community, during three austral summers at coastal Livingston (2015 and 2018) and Deception (2017) islands (Antarctica). The Livingston 2015 campaign was characterized by a larger snow melting input of PAHs and nutrients. The assessment of PAH diagnostic ratios, such as parent to alkyl-PAHs or LMW to HMW PAHs, showed that there was a larger biodegradation during the Livingston 2015 campaign than in the Deception 2017 and Livingston 2018 campaigns. The biogeochemical cycling, including microbial degradation, was thus yearly dependent on snow-derived inputs of matter, including PAHs, consistent with the microbial community significantly different between the different campaigns. The bivariate correlations between bacterial taxa and PAH concentrations showed that a decrease in PAH concentrations was concurrent with the higher abundance of some bacterial taxa, specifically the order Pseudomonadales in the class Gammaproteobacteria, known facultative hydrocarbonoclastic bacteria previously reported in degradation studies of oil spills. The work shows the potential for elucidation of biogeochemical processes by intensive field-derived time series, even in the harsh and highly variable Antarctic environment.

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.

Source Identification, Toxicity, and Persistence of PAHs in Sediment Core from a Natural Protected Area in Mexico

Sediment cores maintain a historical record of the various sources of polycyclic aromatic hydrocarbons (PAHs). In 2020, one sediment core was collected within the oyster farming area of the Pom–Atasta lagoon system and the Terminos lagoon. A total of 16 PAH compounds were analyzed to identify the historical patterns of PAH inputs and the relationship with sediment materials. The core was classified into three strata at depths of 0.0–0.2 m, 0.2–0.6 m, and 0.6–1.1 m, in which the high content of silt–sand, organic matter, and carbonates indicates a system of high energy and productivity. The hydrology and characteristics of the sediment suggest a free access of adsorbed PAHs to the study area, mainly of pyrolytic origin. The concentration of ∑PAHs decreases from the surface (527.0 ng g−1 dw) to a greater depth (75.7 ng g−1 dw), which corresponds to 60% of the HMW (high molecular weight) of the total PAHs as combustion products at low temperatures, while LWM-PAH (low molecular weight) inputs are from discharges of petroleum products. The core sediments showed a low probability of toxicity quotient of 9%. The analysis of the carcinogenic toxic equivalent (TEQcarc) in each section of the core was variable, decreasing with the depth from 107.91 ng TEQ g−1 dw to 57.65 ng TEQ g−1 dw, with the compounds benzo(a)pyrene (53.55 ng TEQ g−1 dw) and dibenzo(a,h) anthracene (29.2 ng TEQcarc g−1 dw) having the highest TEQcarc. The anthropogenic activities around the study area may increase the carcinogenic and mutagenic risk to human health. However, in the present study, the low toxic carcinogenic equivalents (TEQBaP) and mutagenic equivalents (MEQBaP) indicate a low probability of sediment toxicity. The ecosystem could be under constant threat from increasing anthropogenic activity; therefore, monitoring programs for the conservation of these ecosystems and oyster farms should be considered.

Pollution history, source and transport path for PAHs in dated sediment cores from four lakes in Northern China

In this paper, concentrations and compositions of 16 USEPA priority control polycyclic aromatic hydrocarbons (PAHs) in the sediment cores collected from four lakes in northern China were analyzed. Pollution history of PAHs were reconstructed based on 210Pb and 137Cs age-dating. Positive definite matrix factorization (PMF) was adopted to quantify the source and relative contribution rate of PAHs. Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) was used to analyze the input trajectory and potential pollution source areas of PAHs under the influences of different air masses. Potential ecological risks of PAHs were assessed based on Effects Range Low (ERL) and Effects Range Median (ERM). The average concentrations of 16 PAHs in sediment cores from four lakes were 596.53 ng/g, 596.47 ng/g, 216.91 ng/g, and 197.57 ng/g dry weight, respectively. The sedimentary history tended to show a similar pattern. It increased from the bottom to the surface layers, with a dominance of 3- and 4- rings PAHs. Due to the expansion of human activities, there has been a rapid increase in 16 PAHs in the sediments of the four lakes since the late 1970s. According to source apportionment, the combustion of fossil fuel combustion contributed 34.71%, 60.80%, 58.12%, 53.02%, to the PAHs in the four sediment cores, respectively, which were the main sources. HYSPLIT showed that the atmospheric inputs of PAHs in the sediment cores of CG Lake, HL Lake, WLS Lake and BST Lake was mainly local air masses with a short distance, and the input directions were southeast, east, southwest, and northwest, accounting for 16.21%, 12.94%, 15.54%, 22.19% of the total trajectory, respectively. Although there was no potential ecological risk for Σ16PAHs, toxicological assessment suggested that Flu and Ace in the four lakes and Ant in CG Lake could create negative biological consequences. More attention should be paid to seven teratogenic and carcinogenic PAHs, the concentrations of which tended to increase in recent years.

Polycyclic aromatic hydrocarbons in soils of Central Plains Urban Agglomeration, China: The bidirectional effects of urbanization and anthropogenic activities

To investigate the variations in environmental behavior (levels, distribution, sources, and soil toxicity) of polycyclic aromatic hydrocarbons (PAHs) under the impact of anthropogenic activities during the urbanization process, we collected soil samples from 195 sites in the Central Plains Urban Agglomeration (CPUA), North China, and analyzed 16 U.S. Environmental Protection Agency (EPA) PAH priority pollutants. We divided the sampling sites into three groups (urban area, industrial area, and farmland) and collected soil samples (0–20 cm surface layer). ∑16PAHs concentrations in the soils of the urban area, industrial area, and farmland ranged from 24.2 to 4400 ng/g, 12.3–8780 ng/g, and 20.9–852 ng/g (the average value of 349, 634, and 186 ng/g), respectively. The 4 to 5 ring PAHs were dominant compounds in three soil types, accounting for 65–80% of the ∑16PAHs. The results of the source analysis showed that the PAHs in the soils of CPUA were mainly from energy consumption. PAH levels in urban and industrial soils had a potential low cancer risk. The impact of urbanization on PAHs in the soil was bidirectional. On the one hand, the level of PAHs in the farmland soil might increase due to burning coal and agricultural machinery, which releases diesel or petrol fumes. On the other hand, in the urbanization process, the PAH content in urban soil and industrial soil showed a downward trend due to the implementation of environmental protection policies in China, which have reduced the atmospheric input of PAHs into the soil.

Aromatic hydrocarbon signatures of the late Miocene-early Pliocene in the Yinggehai Basin, South China Sea: Implications for climate variations

Aromatic hydrocarbons in 36 shales from the late Miocene-early Pliocene strata of the Yinggehai Basin in the South China Sea were investigated. Various higher plant-derived aromatic hydrocarbons were identified, including cadalene, retene, 1,2,7-trimethylnaphthalene, 1-methylphenanthrene (MP), 1,7-dimethylphenanthrene (DMP), 6-isopropyl-1-isohexyl-2-methylnaphthalene, and other polycyclic aromatic hydrocarbons (PAHs). Higher plant parameters suggest that the relative abundance of terrigenous organic matter in the early Pliocene was lower than in the angiosperm-dominated late Miocene Huangliu Formation. Various plant parameters including retene/(retene + cadalene), 1-MP/9-MP, 1,7-DMP/(1,3- + 3,9- + 2,10 + 3,10-DMP), and the higher plant index, indicate that gymnosperms made a larger contribution to the organic matter when the lower Yinggehai Formation was deposited during the early Pliocene. Combustion-derived PAHs, including fluoranthene, benzo[a]anthracene, benzofluoranthenes and coronene, predominate over petrogenic PAHs in the lower Yinggehai Formation and the upper Meishan Formation, indicating that there were more wildfires during deposition of these units compared to the Huangliu Formation. In contrast, there is a mixed input of combustion-derived and petrogenic PAHs in the Huangliu Formation. As also supported by higher abundances of Pinus in palynological records, the combustion-derived PAHs and the gymnosperm/angiosperm parameters provide unequivocal evidence for a cooling climate from the late Miocene to the early Pliocene in the South China Sea.

Elevated urbanization-driven plant accumulation and human intake risks of polycyclic aromatic hydrocarbons in crops of peri-urban farmlands.

As an ubiquitous carcinogen, polycyclic aromatic hydrocarbons (PAHs) are closely related to anthropogenic activities. The process of urbanization leads to the spatial interlacing of farmlands and urbanized zones. However, field evidence on the influence of urbanization on the accumulation of PAHs in crops of peri-urban farmlands is lacking. This study comparatively investigated the urbanization-driven levels, compositions, and sources of PAHs in 120 paired plant and soil samples collected from the Yangtze River Delta in China and their species-specific human intake risks. The concentrations of PAHs in crops and soils in the peri-urban areas were 2407.92ngg-1 and 546.64ngg-1, respectively, which are significantly higher than those in the rural areas. The PAHs in the root were highly relevant to those in the soils (R2 = 0.63, p < 0.01), and the root bioconcentration factors were higher than 1.0, implying the contributions of root uptake to plant accumulations. However, the translocation factors in the peri-urban areas (1.57 ± 0.33) were higher than those in the rural areas (1.19 ± 0.14), indicating the enhanced influence through gaseous absorption. For the congeners, the 2- to 3-ring PAHs showed a higher plant accumulation potential than the 4- to 6-ring PAHs. Principal component analysis show that the PAHs in the peri-urban plants predominantly resulted from urbanization parameters, such as coal combustion, vehicle emissions, and biomass burning. The mean values of estimated dietary intake of PAHs from the consumption of peri-urban and rural crops were 9116ngday-1 and 6601.83ngday-1, respectively. The intake risks of different crops followed the order rice > cabbage > carrot > pea. Given the significant input of PAHs from urban to farmland, the influence of many anthropogenic pollutants arising from rapid urbanization should be considered when assessing the agricultural food safety.

Multimedia distribution of polycyclic aromatic hydrocarbons in the Wang Lake Wetland, China

The Wang Lake Wetland is a highly valued area that is protected due to its high biodiversity. The wetland has a complicated hydrological regime and is subject to frequent human disturbance. We hypothesize that fluctuating hydrology and human activities have varied contributions to the temporal and spatial variations of polycyclic aromatic hydrocarbons (PAHs) in the wetland. Soil (SS), sediment (SD), and water, to acquire dissolved phase (DP) and suspended particulate matter (SPM), samples were collected from eight locations during low- and high-flow periods to elucidate multimedia phase distribution and transport of PAHs. Following the onset of the rainy season, the concentration of SPM-associated PAHs increased significantly, while the DP PAHs remained stable. Individual PAH ratios showed that, although pyrogenic sources are common, petrogenic derived compounds are the main source of PAHs in the Wang Lake Wetland. During the high-flow period, the empirical values for logarithms of the organic carbon-normalized partition coefficients (log KOC) of individual PAH-congeners were lower than the corresponding field-observed log KOC values from the SPM-DP and SD-DP systems, reflecting the complexity in evaluating multi-phase PAH partitioning. During the high-flow period, temperature-driven changes may have changed the sediment from a sink to a source for some high molecular weight PAHs. It was determined that human activities governed the PAH loading in the low-flow period, whereas during high-flow conditions, increased rainfall, higher temperatures, and fishery activity are the main factors controlling PAH input to the Wang Lake Wetland.

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.

Exposure radius of a local coal mine in an Arctic coastal system; correlation between PAHs and mercury as a marker for a local mercury source

Mercury in the Arctic originates from emissions and releases at lower latitudes and, to a lesser extent, from local and regional sources. The relationship between mercury (Hg) and polycyclic aromatic hydrocarbons (PAHs) in sediment can be applied as an indicator of the mercury source. This research examines the Hg contamination gradient from a land-based coal mine to the surrounding coastal environment to quantify the impact of local sources. Total mercury and PAH (Σ14PAH) were measured in terrestrial and marine sediments as well as in marine biota. Samples were collected at the mine and two reference sites. Mercury and Σ14PAH concentrations in samples collected at the mine site were significantly higher than those at the reference sites. This was also found in the biota samples, although less pronounced. This work addresses the complexities of interpreting data concerning very low contaminant levels in a relatively pristine environment. A clear correlation between PAH and Hg concentration in sediment was found, although a large number of samples had levels below detection limits. PAH profiles, hierarchical clustering, and molecular diagnostic ratios provided further insight into the origin of PAHs and Hg, showing that signatures in sediments from the nearest reference site were more similar to the mine, which was not the case for the other reference site. The observed exposure radius from the mine was small and diluted from land to water to marine biota. Due to low contamination levels and variable PAH profiles, marine biota was less suitable for tracing the exposure radius for this local land-based Hg source. With an expected increase in mobility and availability of contaminants in the warming Arctic, changes in input of PAHs and Hg from land-based sources to the marine system need close monitoring.Graphical abstract

Spatial distribution, source analysis, and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the sediments from rivers emptying into Jiaozhou Bay, China

Sediment samples had been collected from five major rivers into Jiaozhou Bay, China to study the spatial distribution, sources, and ecological risks of 16 priority polycyclic aromatic hydrocarbons (PAHs) in April 2018. Results showed that the contents of PAHs in the sediments from the five rivers were significantly different. The distribution trend was Dagu < Yang < Licun < Baisha < Moshui River. The contents of PAHs in the eastern rivers were higher than those in the western portions. The contribution rate of HMW-PAHs was higher than LMW-PAHs in the sediments, with the majority of PAHs being four rings. PAHs in sediments were mainly derived from combustion sources, including the incomplete combustion of petroleum, coal, and wood. The benzo[a]pyrene toxic equivalent method (TEQ) showed that Moshui River had a high risk of carcinogenesis. The evaluation results of Effects Range Low(ERL), Effects Range Median (ERM) and Mean- Effects Range Median-quotient (M-ERM-Q) showed that PAHs in the sediments of Moshui River would occasionally have adverse biological effects, as well as possible medium and low ecological risks. The ecological risks of PAHs in the sediments of the other four rivers were low. Hence, we should focus on and control the input of PAHs in the Moshui River.