Distributions and potential sources of traditional and emerging polycyclic aromatic hydrocarbons in sediments from the lower reach of the Yangtze River, China

Distribution and sources of polycyclic aromatic hydrocarbons in cascade reservoir sediments: influence of anthropogenic activities and reservoir hydrology

The construction of dams has caused disruptions to river connectivity, leading to alterations in the deposition of hydrophobic organic contaminants in reservoir sediments. Further investigation is warranted to explore the impact of cascade reservoirs with differing hydrological characteristics on polycyclic aromatic hydrocarbons (PAHs) distribution in sediment. This study examines the presence of 30 PAHs in the sediments collected from six cascade reservoirs situated in the Wujiang River basin during January and July 2017. The results showed that Σ30 PAHs ranged from 455-3000 ng/g dw (mean 1030 ng/g dw). Anthropogenic activities and reservoir hydrology determined the distribution trend of PAHs in sediments, with an overall increase from upstream to midstream and then a decrease downstream. The PAH levels were highly linked to the secondary industry (P < 0.05). This was further supported by the relationship between the PAH emissions from coal combustion and traffic sources analyzed by the positive matrix factorization model and economic parameters in the wet season (P < 0.01). At the same time, reservoir age (RA) showed a positive correlation with PAH concentrations (P < 0.05), while hydraulic retention time (HRT) exhibited a negative correlation with PAH levels (P = 0.03). The relationship between total organic carbon (TOC) and PAHs in stream sediments worldwide was nonlinear (P < 0.01), with PAH concentrations initially rising and then falling as TOC levels increased. Concerns regarding carcinogenic risk were raised due to contributions from coal and vehicular sources, with the risk increasing with RA.

Source-risk and uncertainty assessment of trace metals in surface sediments of a human-dominated seaward catchment in eastern China

Current total concentration-based methods for source attribution and risk assessment often overestimate metal risks, thereby impeding the formulation of effective risk management strategies. This study aims to develop a framework for source-specific risk assessment based on metal bioavailability in surface river sediments from a human-dominated seaward catchment in eastern China. Metal bioavailability was quantified using chemical fractionation results, and source apportionment was conducted using the positive matrix factorization (PMF) model. Risk assessment integrated these findings using two indices: the Potential Ecological Risk Index (PERI) and the Mean Probable Effect Concentration Quotient (mPEC-Q), with uncertainty addressed via Monte Carlo simulations. Results indicated that average total concentrations of Cu, Pb, Zn, Cr, Hg, Cd, and As exceeded their respective background levels by 1.63 to 15.00 times. The residual fraction constituted the majority, accounting for 53.84 % to 77.79 % of total concentrations, suggesting significant natural origins. However, source apportionment revealed a predominant contribution from anthropogenic activities, including industrial smelting, agricultural practices, and atmospheric deposition. The contributions were found to vary between 5.35 % and 40.03 % when the total concentration was adjusted to bioavailable content. Total concentration-based PERI/mPEC-Q assessments indicated high/moderate risk levels, decreasing to considerable/low risk levels with bioavailability adjustment. Hg and Cd were identified as priority metals. Further incorporating source appointment parameters into the risk assessment, industrial smelting was identified as the primary contributor, accounting for 66.06 % of total risk by total concentration and 65.63 % by bioavailability. This underscores the role of bioavailability in mitigating risk overestimation. Monte Carlo simulations validated industrial smelting as a major risk contributor. This study emphasizes the importance of considering bioavailability in the source-risk assessment of sediment-metals, crucial for targeted risk management in urbanized catchment areas.

Compound- and element-specific accumulation characteristics of persistent toxic substances and metals in sediments of the Yellow Sea

This study investigated the large-scale distributions of persistent toxic substances (PTSs) and heavy metals in sediments of the Yellow Sea, collected from six transects between latitudes 32 and 37 degrees north (n = 35). Elevated concentrations of polychlorinated biphenyls (PCBs) were detected near the mainland, with a predominance of low-chlorinated congeners (di to tetra, ∼60%), indicative of atmospheric deposition. Analysis of traditional and emerging polycyclic aromatic hydrocarbons (t-PAHs and e-PAHs) revealed notable enrichment in the Central Yellow Sea Mud Zone (CYSM), attributing fossil fuel combustion as the significant source. Styrene oligomers and alkylphenols exhibited notable accumulation near the Han River Estuary in South Korea and the Yangtze River Estuary in China, respectively. The accumulation of heavy metals was predominantly observed in the CYSM, with element-specific distribution patterns. Cluster analysis revealed distinct distribution patterns for PTSs and metals, highlighting their source-dependent and grain size-dependent behaviors. In addition, the distribution and accumulation of PTSs tended to depend on their partitioning coefficients, such as the octanol-air partition coefficient (log KOA) and octanol-water partition coefficient (log KOW). This study offers valuable insights into the sources, transport, and fate of hazardous substances in the Yellow Sea, emphasizing the necessity for targeted environmental management strategies.

Importance of soil ecoenzyme stoichiometry for efficient polycyclic aromatic hydrocarbon biodegradation

Efficient remediation of soil contaminated by polycyclic aromatic hydrocarbons (PAHs) is challenging. To determine whether soil ecoenzyme stoichiometry influences PAH degradation under biostimulation and bioaugmentation, this study initially characterized soil ecoenzyme stoichiometry via a PAH degradation experiment and subsequently designed a validation experiment to answer this question. The results showed that inoculation of PAH degradation consortia ZY-PHE plus vanillate efficiently degraded phenanthrene with a K value of 0.471 (depending on first-order kinetics), followed by treatment with ZY-PHE and control. Ecoenzyme stoichiometry data revealed that the EEAC:N, vector length and angle increased before day five and decreased during the degradation process. In contrast, EEAN:P decreased and then increased. These results indicated that the rapid PAH degradation period induced more C limitation and organic P mineralization. Correlation analysis indicated that the degradation rate K was negatively correlated with vector length, EEAC:P, and EEAN:P, suggesting that C limitation and relatively less efficient P mineralization could inhibit biodegradation. Therefore, incorporating liable carbon and acid phosphatase or soluble P promoted PAH degradation in soils with ZY-PHE. This study provides novel insights into the relationship between soil ecoenzyme stoichiometry and PAH degradation. It is suggested that soil ecoenzyme stoichiometry be evaluated before designing bioremeiation stragtegies for PAH contanminated soils.

Organic matter sources and distribution along land-use gradient in a Himalayan foothills River: Insights from molecular markers

The analysis of hydrocarbon biomarkers in surface sediments along the Markanda River in the foothills of the Indian Himalayas was conducted to gain insights into the distribution and composition of organic matter (OM) within the sediments. This investigation is essential for comprehending how anthropogenic changes are influencing the OM dynamics in river systems. The study involved identification and quantification of various compound groups such as n-alkanes, hopanes, steranes, polycyclic aromatic hydrocarbons (PAHs), linear alkyl benzenes (LABs) and phthalate esters along with their respective parametric ratios. The variation in distribution of n-alkanes and associated indices (odd-even carbon number predominance (OEP), average chain length (ACL), terrigenous to aquatic ratio (TAR), carbon preference index (CPI), and natural n-alkanes ratio (NAR)) were used to distinguish the natural source of organic content from those influenced by anthropogenic contamination. The detection of petroleum contamination was indicated by the presence of prominent unresolved complex mixtures (UCM) as well as specific petroleum biomarkers such as hopanes, diasteranes, and steranes. The study revealed varying concentrations of the analyzed organic pollutants, with the average of PAHs at 24.6 ng/g dw, LABs at 18.1 ng/g dw, and phthalates at 8.3 μg/g dw. The variability in concentration of the investigated compound groups across different locations indicated spatial heterogeneity, and the land use patterns appears to modulate the sources of OM in surface sediments. The source contribution of PAHs and phthalates determined by positive matrix factorization (PMF) shows the predominant sources of the anthropogenic hydrocarbons were linked primarily to petroleum/petroleum-derived products emissions, industrial discharges, cultural practices and common household waste/sewage disposal. This analysis provides insights for developing mitigation strategies and informing relevant policy changes globally, thereby contributing to the broader understanding of anthropogenic impacts on water ecosystems.

Distribution, levels, sources and risk assessment of polycyclic aromatic hydrocarbons in the bottom sediments of a Mediterranean river under multiple anthropopressures (Soummam River), Algeria

The Soummam River, a vital watercourse in Algeria is threatened by anthropogenic activities despite its protected wetland status. This study is the first to assess sediment pollution in the Soummam River, examining levels, compositions, sources of 16 PAHs and their effects on the environment and human health. Analysis employing Principal Component Analysis (PCA) and molecular diagnostic ratios pointed to petrogenic sources, likely stemming from petroleum leaks originating from aging pipeline and vehicles, as well as pyrogenic sources arising from vehicle exhaust and biomass combustion. Environmental and health risks were assessed through risk quotients (RQ), Sediments Quality Guidelines (SQG) and Total Lifetime Cancer Risk (TLCR). Ecological risk was found to range from moderate to high, with anticipated biological impacts, while cancer risk was deemed low. Toxicity assessment, measured by TEQ, revealed that the majority of monitoring stations exceeded safe levels. Consequently, urgent action by local authorities is warranted to implement ecosystem rehabilitation measures.

Receptor model-based sources and risk assessment of metals in sediment of the coastal construction-oriented aquatic system in Bangladesh

Metal pollution in sediment from construction areas raises ecological and health concerns, yet source-based sediment pollution in Bangladesh remains understudied. Our investigation focused on fifteen locations in the Kohelia River and the coastal regions near the Matarbari projects (Matarbari Power Plant, Matarbari Deep Seaport), assessing metal concentrations' sources and impacts on ecology and human well-being. Sediment quality indices indicated high Cd and Cr contamination, with sites near Matarbari projects being the most polluted. The positive matrix factorization model identified three anthropogenic sources and mixed sources. Matarbari projects contributed significantly to As (67.9 %), Mn (50.25 %), Cd (48.35 %), and Cr (41.0 %), while ship-breaking yards contributed Fe (58.0 %), Zn (55.5 %), Pb (53.8 %), and Cu (36.1 %). Ecological indices showed different impacts on aquatic life from metal pollution, but cancer risk levels stayed below the threshold set by the US Environmental Protection Agency. These findings underscore the need for targeted measures to address metal pollution.

Multimedia distribution, dynamics, and seasonal variation of PAHs in Songhua wetland: Implications for ice-influenced conditions

The knowledge of polycyclic aromatic hydrocarbons (PAHs) in wetlands remains limited. There is a research need for the dynamics between interfaces of multimedia when ice is present in this fragile ecosystem. In this study, sediment, open-water, sub-ice water, and ice samples were collected from the Songhua wetland to study the behaviors of PAHs with and without influences from ice. The concentration of all individual PAHs in sub-ice water (370-1100 ng/L) were higher than the open-water collected from non-ice-covered seasons (50-250 ng/L). Enrichment of PAHs in the ice of wetland was found, particularly for high-molecular-weight PAHs (HMW). This could be attributed to the relatively lower polarity of hydrocarbons compounds, making them more likely to remain in the ice layer during freezing. Source assessments reveal common sources for sub-ice water and ice, which differ from those in the open water in non-ice-covered seasons. This difference is primarily attributed to heating activities in the Harbin during winter. The average percentage contributions were 79% for sub-ice water and 36% for ice related to vehicle exhausts and coal combustion. Additionally, wood burning contributed 25% to sub-ice water and 62% to ice. Sediment in the wetland was found to serve as a final deposit particularly for heavier PAHs, especially those with 6 rings. Sediment also has the potential to act as a source for the secondary emission of low-molecular-weight PAHs (LMW) congeners into the water. PAHs in wetland displayed low ecological risk, while HMW PAHs with relative higher ecological risk is recommended to be further monitored.

Distribution characteristics, source analysis and risk assessment of polycyclic aromatic hydrocarbons in sediments of Kuye River: a river in a typical energy and chemical industry zone

This study systematically analyzed the distribution characteristics, sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in Kuye River sediments, located in an energy and chemical industry base in northern Shaanxi, China. The results that revealed the concentrations of 16 PAHs in the sediment ranged from 1090.04 to 32,175.68 ng∙g-1 dw, with the four-ring PAHs accounting for the highest proportion. Positive matrix factorization analysis (PMF) revealed the main sources of PAHs as incomplete fossil fuel combustion, biomass combustion, and traffic emissions. The total toxic equivalent concentration of BaP, risk quotient, and lifetime carcinogenic risk of PAHs suggested moderate to high contamination of PAHs in the area. The higher incremental lifetime carcinogenic risk (ILCR) indicated that PAH ingestion was the primary route of impact on public health, with children potentially being more susceptible to PAH exposure. This study can provide valuable theoretical support for implementing pollution prevention measures and ecological restoration strategies for rivers in energy and chemical industry areas.

Use of molecular composition and compound-specific isotope analysis for source appointment of PAHs in sediments of a highly industrialized area

This study utilized both conventional molecular analysis and compound-specific isotopic techniques to identify the sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Ulsan Bay, South Korea. The concentrations of 15 traditional and 11 emerging PAHs were determined in sediments from 21 source sites and 26 bay sites. The concentrations and compositions of traditional and emerging PAHs varied significantly, even at sites close to the source areas. The results obtained from diagnostic ratios and the positive matrix factorization model for source identification were inconsistent in adjacent source areas. The δ13C profiles of PAHs, such as phenanthrene (Phe), fluoranthene (Fl), pyrene (Py), and benz[a]anthracene (BaA) in the sediments showed distinct features depending on the surrounding sources. In urban sediments, lighter δ13CPhe values were observed (mean: -25.1‰), whereas relatively heavier values of δ13CPy were found in petroleum industry areas (mean: -23.4‰). The Bayesian isotope mixing model indicates that the predominant source of PAHs in Ulsan Bay sediments was the petroleum industry (45%), followed by the non-ferrous metals industry (30%), automobile industry (18%), and urban areas (6.3%). These results demonstrated the utility of stable isotopes in assessing the sources and contributions of PAHs in small-scale regions. However, there are still limitations in compound-specific isotope analysis of PAHs, including insufficient end-members for each source, difficulty in analysis, and the influence of non-point sources; thus, further study is needed to expand its application.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in sediments from Baiyang Lake, China

The issue of polycyclic aromatic hydrocarbons (PAHs) has been an environmental focus worldwide. In this study, the contents, sources, and ecological risks of sixteen PAHs in the sediment of Baiyang Lake were estimated, and a list of priority pollutants was established. The total PAH contents ranged from 114 to 1010 ng·g-1. The composition of PAHs indicated that 4- to 6-ring PAHs predominated in the sediment samples. The diagnostic ratio analysis showed that combustion sources were predominant for PAHs in Baiyang Lake. Specifically, the positive matrix factorization model indicated that diesel engine emissions, gasoline engine emissions, wood combustion sources, and coal combustion sources contributed 22, 32, 24, and 22% of ∑PAHs, respectively. Based on the sediment quality guidelines, mean effects range median quotient, ecological risk quotient, and toxicity equivalent quotient methods, the comprehensive assessment results of PAHs in Baiyang Lake sediments indicated that the ecological risks were at medium and low levels. The priority pollutant list showed that benzo[b]fluoranthene and benzo[a]pyrene were the highest-priority pollutants and thus should be given more attention.

Source apportionment and human health risk of PAHs accumulated in edible marine organisms: A perspective of "source-organism-human"

Most PAHs produced by human activities can be absorbed and accumulated by edible organisms and pose a potential hazard to human health. However, the source apportionment and human health risk of PAHs accumulated in edible organisms remains largely unknown. Therefore, we conducted source analysis and health risk assessment based on the PAH concentrations in ten marine fish from coastal areas of Guangdong, China. Results showed that the pollution of PAHs in fish organisms was at "Minimally polluted" level, and that all marine fish had the ability to accumulate PAHs. Risk assessment indicated Carcinogenic risk of PAHs in four populations was at a "Cautionary risk" level, with urban children suffered the highest risk. Petroleum pollution, Coal and biomass combustion, and Marine transport emissions were identified as the main anthropogenic sources for PAHs in organisms, and Marine transport emissions accounted for the highest Carcinogenic risk. The Acceptable daily intake for all populations were far below their actual daily intake without causing "Cautionary risk". Our findings provide new insights into the source apportionment and health risk of PAHs from a "source-organism-human" perspective, and suggested that joint management of three anthropogenic sources would be an effective way to prevent the health risks of PAHs.

Nationwide distribution of polycyclic aromatic hydrocarbons in soil of China and the association with bacterial community

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has raised great environmental concerns. However, the information on national wide distribution of PAHs in soil as well as their effect on soil bacterial community are limited. In this study, 16 PAHs were measured in 94 soil samples collected across China. The total concentration of 16 PAHs (∑PAHs) in soil ranged from 74.0 to 17,657 ng/g (dry weight basis), with a median value of 200 ng/g. Pyrene was the major soil PAH, with a median concentration of 71.3 ng/g. Soil samples from Northeast China had a higher median concentration of ∑PAHs (1,961 ng/g) than those from other regions. Petroleum emission and wood/grass/coal combustion were potential sources for soil PAHs based on diagnostic ratios and positive matrix factors analysis. A nonnegligible ecological risk (hazard quotients > 1) was found in over 20% of soil samples analyzed and the highest median total HQs value (8.53) was found in soils from Northeast China. The effect of PAHs on bacterial abundance, α-diversity, and β-diversity was limited in the soils surveyed. Nevertheless, the relative abundance of some members in genera Gaiella, Nocardioides, and Clostridium was significantly correlated with the concentrations of some PAHs. Especially, the bacterium Gaiella Occulta showed potential in indicating soil contamination by PAH, which is worth further exploration.

Distributions and potential sources of polychlorinated biphenyls and polycyclic aromatic hydrocarbons in the glacimarine sediments of Arctic Svalbard

Distribution and sources of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in the glacimarine sediments (35 sites) of Svalbard were investigated. PCBs (32 congeners), traditional PAHs (15 homologs), emerging PAHs (11 homologs), and alkylated PAHs (16 homologs) were widely distributed in the Svalbard sediments (ranges: below method detection limit to 20, 21 to 3600, 1.0 to 1400, and 31 to 15,000 ng g^-1 dry weight, respectively). Compositional analysis indicated that PCBs mainly originated from combustion sources, with PAHs being strongly influenced by local sources. Positive matrix factorization analysis showed that PAHs were associated with vehicle and petroleum combustion, coal, and coal combustion. Coal-derived PAHs contributed significantly to the sediments of Van Mijenfjorden. Remnants of coal mining activity trapped in the permafrost appear to enter the coastal environments as ground ice melts. Consequently, PAHs are currently emerging as the most significant contributors to potential risks in the Svalbard ecosystems.

Historical evolution of polycyclic aromatic hydrocarbon pollution in Chaihe Reservoir from 1863 to 2018

Pollution from polycyclic aromatic hydrocarbons (PAHs) spreads and changes worldwide. The pollution evolution in the regional water environment evolves in response to multiple factors, requiring considerable attention. PAH heterogeneity in the sediment core from Chaihe Reservoir was investigated to indicate dynamic changes in PAH pollution levels and sources and propose recommendations for controlling PAHs. Dynamic PAH patterns showed that the overall decline in PAH pollution was in association with local anthropogenic activities, temperature, and precipitation over the period 1863-2018. Nevertheless, coal, oil, and natural gas consumptions still played significant roles in transferring PAHs to the reservoir. Meanwhile, there were dominant local origins, including grass, wood, and coal combustion. The results highlight that the joint action of natural and anthropogenic interventions mitigated PAH pollution in the reservoir. Promoting improved fuels, new energy vehicles, and cleaner energy may further lower PAH pollution.

Characterization of the simultaneous degradation of pyrene and removal of Cr(VI) by a bacteria consortium YH

Microorganisms that can simultaneously remediate organic pollutants and heavy metal contamination are great significance in bioremediation. Nevertheless, reports of such microorganisms are still scarce. Here, Pseudomonas sp. YH-1 and Rhodococcus sp. YH-3 were isolated and identified, and they showed greater tolerance to hexavalent (VI) (750 and 800 mg·L^-1). The constructed bacteria consortium YH (YH-1:YH-3 = 1:1) could simultaneously degrade 41.69% of pyrene (50 mg·L^-1) and remove 76.67% of Cr(VI) (30 mg·L^-1) within 5 days. The potential mechanism of Cr(VI) tolerance of YH was further explored by genomic and microscopic analysis. The results showed that YH responded to Cr(VI) stress mainly through efflux of Cr(VI) by chrA and copZ, chromate reduction, DNA-repaired proteases reduces ROS damage, and biosorption by carboxyl, hydroxyl, amino functional groups. Strains YH-1 and YH-3 also contained a variety of genes associated with resistance to other heavy metals, such as cadmium (czcBD), mercury (merAPTR), manganese (mntABC) and copper (copAC, cusABRF and pcoBD). Based on GC-MS and genomic analysis, pyrene was degraded via salicylic acid and phthalic acid pathways. Moreover, a great number of genes related to aromatic hydrocarbon catabolism were identified in the genomes of YH-1 and YH-3. These results confirmed the potential application of the bacteria consortium YH in the bioremediation of water and soil co-contaminated with PAHs-heavy metals.