Aliphatic and polycyclic aromatic hydrocarbons in the Xihe River, an urban river in China's Shenyang City: distribution and risk assessment

Assessment of potential ecological risk for polycyclic aromatic hydrocarbons in urban soils with high level of atmospheric particulate matter concentration

Polycyclic aromatic hydrocarbons (PAHs) are known to be representative carcinogenic environmental pollutants with high toxicity. However, information on the potential ecological and environmental risks of PAH contamination in soil remains scarce. Thus, this study was evaluated the potential ecological risks of PAHs in soils of five Korean areas (Gunsan (GS), Gwangju, Yeongnam, Busan, and Gangwon) using organic carbon (OC)-normalized analysis, mean effect range-median quotient (M-ERM-Q), toxic equivalent quantity (TEQ) analysis, and risk quotient (RQ) derived by the species sensitivity distribution model. In this study, atmospheric particulate matter has a significant effect on soil pollution in GS through the presence of hopanes and the similar pattern of PAHs in soil and atmospheric PAHs. From analysis of source identification, combustion sources in soils of GS were important PAH sources. For PAHs in soils of GS, the OC-normalized analysis, M-ERM-Q, and TEQ analysis have 26.78 × 105 ng/g-OC, 0.218, and 49.72, respectively. Therefore, the potential ecological risk assessment results showed that GS had moderate-high ecological risk and moderate-high carcinogenic risk, whereas the other regions had low ecological risk and low-moderate carcinogenic risk. The risk level (M-ERM-Q) of PAH contamination in GS was similar to that in Changchun and Xiangxi Bay in China. The Port Harcourt City in Nigeria for PAH has the highest risk (M-ERM-Q = 4.02 and TEQ = 7923). Especially, compared to China (RQPhe =0.025 and 0.05), and Nigeria (0.059), phenanthrene showed the highest ecological risk in Korea (0.001-0.18). Korea should focus on controlling the release of PAHs originating from the PM in GS.

Seasonal distribution characteristics and ecological risk assessment of phthalate esters in surface sediment of Songhua River basin

Phthalic acid esters (PAEs) are typical industrial chemicals used in China. PAEs have received considerable attention because of their ubiquity and potential hazard to humans and the ecology. The spatiotemporal distributions of six PAEs in the surface sediments of the Songhua River in the spring (March), summer (July), and autumn (September) are investigated in this study. The total concentration of phthalic acid esters (∑6PAEs) ranges from 1.62 × 102 ng g-1 dry weight (dw) to 3.63 × 104 ng g-1·dw, where the amount in the spring is substantially higher (p < 0.01) than those in the autumn and summer. Seasonal variations in PAEs may be due to rainfall and temperature. The ∑6PAEs in the Songhua River's upper reaches are significantly higher than those in the middle and lower reaches (p < 0.05). Dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) are the two most abundant PAEs. The ecological hazard of five PAEs is assessed using the hazard quotient method. DBP and DEHP pose moderate or high ecological risks to aquatic organisms at various trophic levels. PAEs originate primarily from industrial, agricultural, and domestic sources. Absolute principal components-multiple linear regression results indicate that agricultural sources are the most dominant contributor to the ∑6PAEs (53.7%). Guidelines for controlling PAEs pollution in the Songhua River are proposed.

Pollution patterns and their effects on biota within lotic and lentic freshwater ecosystems: How well contamination and response indicators correspond?

Aquatic environments are often severely polluted with chemical substances of anthropogenic origin, which can pose a potential threat to aquatic organisms and human health. In this study, patterns and sources of heavy metals (HMs, 6 metals) and polycyclic aromatic hydrocarbons (PAHs, 16 hydrocarbons), contamination indicators, environmental genotoxicity measures and metrics of ecological status in lotic and lentic ecosystems were collated for the first time. Chemical analysis has confirmed previously reported long-term contamination at certain study sites. The sediments of Lake Talkša, located in a city and characterized by exclusive anthropogenic pressure, exhibited the highest levels of contamination by both HMs and PAHs. Through positive matrix factorization (PMF) analysis, vehicle and industrial emissions were identified as the primary sources of HMs and PAHs. Our results revealed that frequencies of genotoxic aberrations were higher in river sites compared to lakes, with the highest genotoxic risk observed in the Nemunas River below industrial cities Alytus and Kaunas. Surprisingly, even the severely contaminated Lake Talkša showed only a "moderate" grade of genotoxic risk, highlighting the potential for adaptation of biota to long-term contamination especially in lentic ecosystems. The ecological quality status assessed by macroinvertebrate metrics, which may be sensitive to observed high biological contamination, appeared to be unrelated to contamination patterns. Consequently, to obtain the robust information on anthropogenic contamination and its effects, a combination of various assessment methods and metrics should be employed.

Dissemination and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in water and sediment of Buriganga and Dhaleswari rivers of Dhaka, Bangladesh

Concentration, source, ecological and health risks of sixteen polycyclic aromatic hydrocarbons (PAHs) were estimated for water and sediment samples of two urban rivers namely Buriganga River (BR) and Dhaleswari River (DR). The mean concentration of ∑PAHs in BR water and sediment were 9619.2 ngL-1 and 351.6 ngg-1, respectively. Furthermore, the average PAH concentrations detected in DR water and sediment were 1979.1 ngL-1 and 792.9 ngg-1, respectively. The composition profile showed that 3-ring PAHs were dominant in the water matrix; however, 5-ring PAHs were prevalent in the sediment samples of both rivers. Sources apportion study of PAHs indicated that mixed combustion and petroleum sources are responsible for PAHs contamination in the rivers. Ecological risk study of water suggested that the aquatic lives of both rivers are threatened by Fla, BbF, BkF, DahA, and IcdP, as presented above the threshold level. Comparison with sediment quality guidelines (SQGs) indicated that adverse effects might cause occasionally in the sediment ecosystem in DR at certain sampling sites for Nap, Acy, Fl, Phe, Ant, Pyr, Chr, BaP, and DahA. On the other hand, the presence of Nap, Acy and DahA might occasionally cause adverse biological effects in the BR sediment ecosystem. Estimated hazard quotient (HI > 1) and carcinogenic risk (CRtotal > 10-4) values indicated that local inhabitants living in the vicinity of the rivers are prone to high health risks.

The investigation of the physiochemical factors and bacterial communities indicates a low-toxic infectious risk of the Qiujiang River in Shanghai, China

The overall water quality of urban rivers is closely related to the community structure and the physiochemical factors in them. In this study, the bacterial communities and physiochemical factors of the Qiujiang River, an important urban river in Shanghai, were explored. Water samples were collected from nine sites of the Qiujiang River on November 16, 2020. The water quality and bacterial diversity were studied through physicochemical detection, microbial culture and identification, luminescence bacteria method, and 16S rRNA Illumina MiSeq high-throughput sequencing technology. The water pollution of the Qiujiang River was quite serious with three water quality evaluation indexes, including Cd²⁺, Pb²⁺, and NH₄⁺-N, exceeding the Class V standard set by the Environmental Quality Standards for Surface Water (China, GB3838-2002), while the luminescent bacteria test indicated low toxicity of nine sampling sites. Through 16S rRNA sequencing, a total of 45 phyla, 124 classes, and 963 genera were identified, in which Proteobacteria, Gammaproteobacteria, and Limnohabitans were the most abundant phylum, class, and genus, respectively. The Spearman correlation heatmap and redundancy analysis showed that the bacterial communities in the Qiujiang River were correlated with pH; the concentrations of K⁺, and NH₄⁺-N, and the Limnohabitans were significantly correlated with the concentrations of K⁺, and NH₄⁺-N in the Zhongyuan Road bridge segment. In addition, opportunistic pathogens Enterobacter cloacae complex and Klebsiella pneumoniae in the samples collected in the Zhongyuan Road bridge segment and Huangpu River segment, respectively, were successfully cultured. The Qiujiang River was a heavily polluted urban river. The bacterial community structure and diversity were greatly affected by the physiochemical factors of the Qiujiang River, and it displayed low toxicity while a relatively high infectious risk of intestinal and lung infectious diseases.

Sources, pollution, and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in Porto-Novo Lagoon, Benin Republic

The Porto-Novo Lagoon is influenced by agricultural discharges and human activities. In order to evaluate the impact of wastes and human activities on Porto-Novo Lagoon, the sources and ecological risks of sixteen polycyclic aromatic hydrocarbons (PAHs) were assessed. The physicochemical and biological parameters of the water were also determined. The result showed that between the sampling sites, the mean concentration of dissolved oxygen ranged from 4.8 ± 0.5 to 5.1 ± 0.2 mg/L; biochemical oxygen demand varied from 12.6 ± 2.0 to 77.9 ± 81.9 mg/L; biological oxygen demand ranged from 2.8 ± 2.6 to 5.6 ± 0.9 mg/L; total phosphorus varied between 4.7 ± 2.7 and 15.3 ± 9.5 mg/L; total dissolved solids ranged from 183.0 ± 115.8 to 337.5 ± 413.3 mg/L, and Escherichia coli varied from 495.0 ± 542.9 to 1920.0 ± 2676.5 UFC/100 mL. Water parameter values obtained were not within World Health Organization (WHO)-recommended limits except pH and TDS. Total PAHs (∑PAHs) concentration varied from 38.8 to 123.9 mg/L. The mean ∑PAH concentration was 83.2 ± 20.3 mg/L. Benzo[b]fluoranthene, benzo[g,h,i]perylene, and benzo[k]fluoranthene were the most dominant PAHs and contributed to 55.9%, 15.3%, and 4.5% of the ∑PAHs concentration, respectively. Douane-Tokpa and Djassin recorded the lowest and highest concentrations. PAHs of four to six rings were the most abundant across the sampling sites. Naphthalene showed the lowest risk in the lagoon. Acenaphthene showed low risk at Djassin, while Indeno(1,2,3 cd)pyrene showed low risk at Benin Industry Body Fat. Except for those that were not detected, all the PAHs at individual or complex mixture levels showed high risk at all the sites. The highest total concentration was recorded in Djassin followed by Beaurivage. The high level of PAHs pollution was attributed to both human and goods traffic, runoff, and the complex hotels close to the lagoon. Molecular diagnostic ratios and principal component analysis suggest that the target hydrocarbons were from both petrogenic and pyrogenic sources with predomination of vehicular emission and coal/woods combustion. ∑LWM/HWM confirmed also the predominance of pyrolytic sources of PAHs in Porto-Novo Lagoon. The predominance of the vehicular emission may be due to the position of the complex Porto-Novo Lagoon-Nokoué Lake which is between the two big cities of the country.

Effects of Different Types of Human Disturbance on Total and Nitrogen-Transforming Bacteria in Haihe River

Haihe River is the largest water system in North China and is injected into the Bohai Sea in Tianjin City. In this study, different types of human disturbance (urban sewage, industrial pollution, ship disturbance) were selected from the upper reaches of Haihe river Tianjin section down to the estuary that connected with Bohai Sea for evaluation. By metagenomic sequencing, the effects of different types of disturbances on bacteria communities in Haihe sediments were studied, with a special focus on the function of nitrogen-cycling bacteria that were further analyzed through KEGG comparison. By analyzing the physical and chemical characteristics of sediments, results showed that human disturbance caused a large amount of nitrogen input into Haihe River, and different types of human disturbance led to distinct spatial heterogeneity in different sections of Haihe River. The bacteria community was dominated by Proteobacteria, followed by Chloroflexi, Bacteroidetes, Actinobacteria and Acidobacteria. The relative abundance of each phylum varied at different sites as a response to different types of human disturbances. In nitrogen cycling, microorganisms including nitrogen fixation and removal were detected at each site, which indicated the active potential for nitrogen transformation in Haihe River. In addition, a large number of metabolic pathways relating to human diseases were also revealed in urban and pollution sites by function potential, which provided an important basis for the indicative role of urban river ecosystem for public health security. In summary, by evaluating both the ecological role and function potential of bacteria in Haihe River under different types of human disturbance, the knowledge of microorganisms for healthy and disturbed river ecosystems has been broadened, which is also informative for further river management and bioremediation.

Characterizing spatiotemporal variations of polycyclic aromatic hydrocarbons in Taihu Lake, China

In this study, we analyzed the concentration distributions of 20 polycyclic aromatic hydrocarbons (PAHs) in 41 water samples which were collected from the northern part of Taihu Lake during 4 field campaigns (201511, 201606, 201702 and 201709). The concentrations were determined with GC-MS, and their spatial and seasonal distribution characteristics were interpreted. The results show that 2-ring PAHs present considerably higher concentrations in warm seasons than cold seasons, but the concentrations of the other higher-ring PAHs are rather stable in warm and cold seasons. The distribution patterns of these PAHs might be mainly attributed to ambient temperature effects on the PAH solubility in the water body. Meanwhile, the spatial distributions of the PAH concentrations in cold seasons were rather various in the sampling area, while the distributions in the warm seasons were homogeneous. The different distributions could result from the water recharge from the Yangtze River during cold seasons, which diluted PAH concentrations in the northeastern part of the lake. Furthermore, via literature review on PAH concentrations in water body, PAHs are in a wide range of levels and their patterns are different among the studies, which should be more effected by local factors instead of general PAH properties. The results from this study also present special characteristics of PAHs in Taihu Lake, which exhibit more insight on PAHs existence in water bodies.

Heavy Metal Pollution and Health Risk Assessment of Vegetable-Soil Systems of Facilities Irrigated with Wastewater in Northern China

Soil pollution by heavy metals is a major concern in China and has received much attention in recent years. Aiming to investigate the status of heavy metal pollution and the safety of vegetables in the soil of wastewater-irrigated facilities, this study investigated the distribution and migration characteristics of heavy metals in vegetable−soil systems of facilities in a typical sewage irrigation area of the Xi River, Shenyang City, northern China. Health risks due to the fact of exposure to heavy metals in the vegetable soil of facilities and ingrown vegetables through different exposure pathways were evaluated. Spatial interpolation and a potential ecological risk assessment were applied to evaluate the soil quality. Bioaccumulation factors (BCFs) were used to analyze the absorption and transportation capacity of Cd, Cu, Pb, and Zn by different parts of different vegetables. The results showed that the average concentration of Cd exceeded the standard values by 1.82 times and accumulated by 11 times, suggesting that Cd poses the most severe pollution among the four metals in the soil of facilities in the Xi River sewage irrigation area. In the city, a significant accumulation of Cd in the soil was identified with different spatial distributions. Cd also contributed the most in terms of the estimated potential ecological risk index, while the impacts of the other three metals were relatively small. The concentrations of heavy metals were mostly lower than the limit set by the corresponding Chinese standards. Various BCFs were observed for the four metals in the order Cd > Zn > Cu > Pb. Vegetables also demonstrated different BCFs in the order of leaf vegetables > Rhizome vegetable > Solanaceae vegetable. The magnitude of the noncarcinogenic risk for all four heavy metals was less than one for all three exposure routes and did not cause significant noncarcinogenic health effects in humans. However, the carcinogenic risk of Cd from some vegetables via dietary intake was considered higher. Protection measures should be taken to implement better pollution control and land use planning.

Assessing potential risks of aquatic polycyclic aromatic compounds via multiple approaches: A case study in Jialing and Yangtze Rivers in downtown Chongqing, China

To better evaluate the potential risks of aquatic polycyclic aromatic compounds (PACs), multiple approaches have been implemented in this study to assess the human health and ecological risks of parent, nitrated and oxygenated polycyclic aromatic hydrocarbons (PAHs, NPAHs and OPAHs) in the surface water of Jialing and Yangtze Rivers in downtown Chongqing in southwestern China. The concentrations of ∑PAHs (334 ± 125 ng L^-1) were much higher than those of ∑OPAHs (20.2 ± 7.49 ng L^-1) in the two rivers, while NPAHs were barely detected. Concentrations of detected PACs were higher in wet season than dry season, probably resulted from the elevated particle input due to heavy rainfall in wet season. Concentrations of PAHs were higher in the particulate phase than dissolved phase, while OPAHs levels showed a reverse pattern. The partition coefficients (K_p) of PACs in the water-SPM (suspended particulate matter) system were mainly affected by SPM concentrations and octanol/water partition coefficients of specific PACs. Human health risks calculated from non-probabilistic risk assessment model and probabilistic risk assessment model based on Monte Carlo simulation showed similar data pattern with slight difference in absolute values. Both models revealed potential or even severe human health risks contributed mainly by dermal exposure to aquatic PACs in this study. Furthermore, these models also manifested that infant stage was highly sensitive for PAC exposure. Sensitivity analysis indicated that health risk results was most sensitive to Benzo[a]pyrene equivalent toxic concentration (BaP_eq), followed by showering time and daily water intake volume. Levels of ecological risks and contributions of individual PACs differed from models based on different quality values. The adequacy of toxicity data was crucial for the reliability of ecological risk assessment.

Polycyclic aromatic hydrocarbons in 30 river ecosystems, Taiwan: Sources, and ecological and human health risks

Polycyclic aromatic hydrocarbons (PAHs) are diverse contaminants of global concern because of their ubiquity, toxicity, and carcinogenicity to many organisms, including humans. This study determines the distribution and sources of PAHs in sediments and fish from 30 major rivers in Taiwan, and the risks these PAHs pose to river ecosystems and human health. The total concentrations of 26 PAHs in sediments and fish were 0.016-7.44 mg/kg dw and 0.096-5.51 mg/kg ww, respectively. The PAH composition in sediments differed from that in fish, indicating that sediments may not be the major contributor of PAHs to fish. The accumulation of different PAH compounds in fish was species-specific, depending on the lipid content, living pattern, and trophic level of each fish species, and on the level of environmental contamination. The diagnostic ratios revealed that PAHs in the sediment primarily originated from pyrogenic sources, with some contribution from petrogenic sources. The contribution of each source varied with the sampling site and season. Several water and air quality variables were found to significantly correlate with PAH concentration in sediments and fish, suggesting that PAHs were mainly derived from wastewater discharge and combustion emissions. The 95th percentile risk quotient values suggested that PAHs in sediment from six rivers pose high ecotoxicological risks. The toxic equivalents of benzo[a]pyrene for 16 PAHs in fish were 12-108 μg/kg dw. A human risk assessment using the 95th percentile values of hazard quotient, hazard index, and margin of exposure revealed that the consumption of contaminated fish muscle poses no remarkable risk to human health. However, the 95th percentile carcinogenic risk values indicated that benzo[a]pyrene concentrations in some fish muscles may pose a carcinogenic risk. Benzo[a]pyrene risk management measures are, therefore, necessary.

Normal alkanes in sediments from the Persian Gulf: spatial pattern and implications for autochthonous, allochthonous, and petroleum-originated contaminants

Surface sediments (n = 124) were gathered to evaluate spatial pattern and source apportionment of ∑₂₄n-alkanes in the Persian Gulf. Moran's I indices revealed that ∑₂₄n-alkanes were randomly distributed in sampling space in general. One noticeable exception was a significant spatial high-high cluster (Z-score = 8.6). Profile of n-alkanes observed for this cluster maximized at n-C₂₀, n-C₁₈, n-C₁₆, and n-C₂₂. Detection of very low carbon preference indices and strong even carbon-numbered predominance suggested that bacterial inputs were the process making this cluster. Based on diagnostic ratios and GIS techniques, in situ production of organic materials was widespread in the studied space. Allochthonous and petroleum-based inputs were not traceable for 73.8% and 24.7% of the area, respectively. Petrogenic source apportionment map proposed that petroleum-originated contaminants were probably limited to 6.32 km² of the sampling matrix. The biogenic inputs (autochthonous and allochthonous inputs) and not the petroleum contaminants were the main source of n-alkanes deposited.

Spatial distribution and influencing factors on the variation of bacterial communities in an urban river sediment

The water and sediments of urban rivers are spatially heterogeneous because of the influence of environmental and anthropogenic factors. However, the spatial and functional diversity of bacterial communities in urban river sediments are unclear. We investigated the spatial distribution of microbial compositions in sediments in Qingdao section of the Dagu River, and the effects of sediment physiochemical properties on the variation were explored. Among the seven heavy metals analyzed, only the average concentration of Cd significantly exceeded the safety limit for sediments. The detailed composition and spatial distribution of bacterial communities fluctuated substantially between sites along the river. Bacterial datasets were separated into three clusters according to the environmental characteristics of sampling areas (the urbanized, scenic, and intertidal zones). For the urbanized zone, Acidobacteria, Firmicutes, Gemmatimonadetes, Bacteroidetes, and Gammaproteobacteria were significantly enriched, implying the effects of human activity. In the intertidal zone, Alphaproteobacteria and Deltaproteobacteria were significantly enriched, which are associated with S redox processes, as in the marine environment. Variation partitioning analysis showed that the amount of variation independently explained by variables of Na, Al, total S and Zn was largest, followed by sediment nutrients, while heavy metals and pH explained independently 13% and 9% of the variance, respectively. Overall, microbial structures in the Dagu River exhibited spatial variation and functional diversity as a result of natural and anthropogenic factors. The results will enable the prediction of the changes in urban river ecosystems that maintain their ecological balance and health.

Concentrations, distribution and risk of polycyclic aromatic hydrocarbons in sediments from seven major river basins in China over the past 20 years

Polycyclic aromatic hydrocarbons (PAHs) in river sediments in China have been extensively investigated. However, most previous studies only reported information about specific locations. As a result, the distribution and changes of these chemicals in sediments nationwide remain unknown. Based on published data during 1997-2020, we conducted a systematic meta-analysis to understand the concentration, risk and the spatiotemporal variation of PAHs in river sediments from the seven major river systems in China. The report provides a national picture of PAHs in river sediments of China. Among the seven river systems, higher concentrations of sediment PAHs are found in the basins of Liaohe River and Haihe River. In the study sediments, high-molecular-mass (4-6-ring) PAHs were predominated, reflecting the widespread combustion of coal and fossil fuels across China. In addition, PAH source assessment also suggests that raw coal and crude oil are important contributors to PAH concentrations in the rivers in northeastern China. Over the past 20 years, there is no downward trend in the concentrations of Σ₁₆PAHs in sediments in the seven river basins; but the contribution of high-temperature combustion to the pollution has declined. In addition, our calculated risks from sediment PAHs seem to decline between 1997-2006 and 2007-2017 periods, although the differences were not statistically significant (p > 0.05). Of note, the data collection and the risk assessment methods used in this preliminary survey may result in some uncertainty. Our results suggest that the PAHs in river sediments in China still need to be paid attention to due to the complexity of their sources and harms to aquatic organisms.

Risk assessment framework for nitrate contamination in groundwater for regional management

Nitrate pollution in groundwater is now one of the most important environmental problems all over the world. For this purpose, a new framework for risk screening and assessment of groundwater nitrate was proposed according to source-pathway-receptor-response model to provide basic for defining environmental management strategies. The framework is composed of groundwater relative risk model (RRM), groundwater contamination risk assessment (CRA), and human health risk assessment (HHRA). The framework is applied in the lower Liaohe river basin plain, northeast of China. The results showed that the priority area with high groundwater relative risk in study area was successfully screened by RRM. Furthermore, the sites with high human health risk for public by groundwater nitrate were selected as hazardous areas. This framework promotes systematic integration of risk assessment of groundwater nitrate and expands traditional research on groundwater management from a scale-based approach to crucial insights into pollution.

Using GIS, geostatistics and Fuzzy logic to study spatial structure of sedimentary total PAHs and potential eco-risks; An Eastern Persian Gulf case study

GIS, geo-statistics and autocorrelation analysis were employed to reveal spatial structure of sedimentary ∑16PAHs. Global Moran's I index outlined significant ∑₁₆PAHs clusters for the entire region (Moran's I index =0.62, Z-score = 25.6). Anselin Moran's I index specified locations of the significant low/high spatial clusters. The levels of random and structural variance of ∑₁₆PAHs were about 0.083 and 0.154, respectively. Nugget to sill ratio confirmed that ∑₁₆PAHs has a moderate level of spatial structure and the major part of PAHs variability is not random. Prediction and standard error maps of ∑₁₆PAHs, produced by ordinary kriging, highlighted that more samples should be taken from high cluster region for next studies. Fuzzy logic functions (OR and AND) were used to develop eco-risk maps. It revealed that the potential hazards of PAHs are considerable at the vicinity of petrochemical facilities.

An optimization model of sewage discharge in an urban wetland based on the multi-objective wolf pack algorithm

The Longfeng Wetland of Daqing City in China was taken as the research object to determine a reasonable sewage reduction scheme and resolve the pollution of urban wetland ecosystems. First, the main pollutants, including dichromate oxidizability (COD_Cr), ammonia nitrogen (NH₃-N), total phosphorus (TP), and petroleum, were selected as indices. A two-dimensional hydrodynamic and water quality coupling model was established using MIKE 21. An optimal regulation method to improve the water quality of the wetland was then proposed following the numerical simulation method, and a multi-objective optimization model is established. The model establishes two objective functions based on wetland pollutant and water quality requirements. The model's constraints include hydrodynamic conditions and water quality conditions, and it considers the control point of the sewage concentration, sewage outfall processing capacity, depth of treatment, and changes in the water cycle. The wolf pack algorithm is introduced to resolve the multi-objective problem of sewage outfall optimization, and an optimal sewage scheme is obtained. According to the results of the scheme, some measures are proposed to manage the pollutants in urban wetland waters.

Source, spatial distribution, and toxicity potential of Polycyclic Aromatic Hydrocarbons in sediments from Iran's environmentally hot zones, the Persian Gulf

Surface sediments, sampled from Iranian coast of the Persian Gulf (n = 134), were analyzed in order to track spatial distribution of PAHs and their related eco-hazards. The levels of PAHs were in the range of 1.98-814 ng g^-1 dw and the region was lowly to moderately polluted. The profile of PAHs was mainly composed of 2,3-ring chemicals and suggested a local source of PAHs and relatively fresh inputs. Statistical analysis and molecular fingerprints proposed that the basin receives PAHs from multiple origins including petrogenic and pyrogenic (traffic and auto emission) ones. Spatial distribution of organic matter and fine fraction of the sediments had a horizontally increasing trend in the studied basin. ∑₁₆PAHs showed significant positive correlation with TOC and fine fraction (p < 0.05) and the spatial deposition of ∑₁₆PAHs followed the spatial trends of TOC and fine fraction. Spatial mapping techniques confirmed that Pars Special Economic Energy Zone (PSEEZ) is the hot zone of PAH pollution. A combination of source availability, finer sediments, and great organic matter levels were the main effective factors that highlighted the deposition of PAHs in the PSEEZ. The Nayband Bay, as the Iran's first national marine Park, possibly received PAHs from its adjacent zone, the PSEEZ. On the other hand, low organic matter and sandy nature of the Nayband Bay was not suitable for effective sequestration of PAHs. Thus, the biota of Nayband Park was encountering with relatively severe multiple eco-hazards due to both ecological and economic factors.

Profiles and potential health risks of heavy metals in soil and crops from the watershed of Xi River in Northeast China

Heavy metal soil contamination is a major environmental concern in China and has drawn significant public attention in recent years. The present study assessed the human health risk of four heavy metals (cadmium, lead, mercury, and zinc) through soil exposure and dietary intake in the watershed of Xi River, west of Shenyang, Liaoning Province, northeast China. Concentrations of Cd, Pb, Hg, and Zn were determined in 411 soil samples and 59 crop samples collected from this area. The health risks of heavy metal exposure via soil ingestion, inhalation, dermal contact, and dietary intake of crops were further estimated; total hazard index values were 1.15, 1.33, and 2.03 for the adult male, adult female, and children, respectively, and the total cancer risk was 3.7 × 10^-3 for the local residents. Among the four investigated heavy metals, Cd was the primary pollutant posing health risks. The estimated non-carcinogenic and carcinogenic risks posed by the studied heavy metals were above the acceptable levels proposed by the U.S. EPA. Dietary intake of contaminated crops was identified as the predominant pathway for human heavy metal exposure in this area, suggesting that soil heavy metals can cause more harm when transported to the food chain. Overall, our findings suggest that the Xi River watershed is unsuitable for growing agricultural products, and more effective controls should be taken to curb future heavy metal pollution in the area.

Long-term effects of untreated wastewater on soil bacterial communities

For 46 years (1957-2002), irrigation with wastewater has increased the amount of heavy metal and organic contaminants in soils and altered bacterial communities in Shenyang, northeastern China. There has been characterization of the different heavy metal and petroleum contaminants in two types of land uses (cornfields and paddy fields). The Nemerow composite indices of heavy metal contaminants have been higher in cornfields (1.17-4.73) than those in paddy fields (0.57-1.64). Molecular-based techniques and biochemical-based techniques were used to analyze soil microbial diversity in our study. The metabolic activity of soil microbe communities was higher in paddy sites than that in cornfields. Organic pollutants such as saturated and polycyclic aromatic hydrocarbons have significantly affected soil bacterial compositions. Heavy metals differed in how they disturbed the microbial communities. Arsenic (As) and lead (Pb) shifted the community composition and decreased microbial diversity; copper (Cu) reduced bacterial abundance in soil; and cadmium (Cd) and chromium (Cr) lowered the metabolic capabilities of bacteria.

Impact of secondary effluent from wastewater treatment plants on urban rivers: Polycyclic aromatic hydrocarbons and derivatives

The growing population in urban area impacted the water quality of the urban rivers receiving treated municipal wastewater. Polycyclic aromatic hydrocarbons (PAHs) and their derivatives (SPAHs) are corresponding to the population density. In this study, the concentrations of 16 PAHs and 17 SPAHs, including 4 methyl PAHs (MPAHs), 4 oxygenated PAHs and 9 chlorinated PAHs were investigated in the major urban rivers receiving the effluent from 5 major wastewater treatment plants (WWTPs) in the mega city Beijing. The concentrations of ΣSPAHs (307 ± 68 ng/L) were similar to ΣPAHs (321 ± 92 ng/L) in the total phase (aqueous + particulate) suggesting that SPAHs in the urban rivers should be taken into consideration. The lower concentrations of ΣPAHs and ΣMPAHs in this study than the wastewater receiving rivers and WWTPs effluent previously (2010-2013), as well as the lower concentration in the heating seasons than the non-heating season in the investigated year implied the reduction of coal combustion for heating and power generation in recent years. Although WWTPs effluent was theoretically the only source to the urban rivers in the investigated season, April and November, PAHs and SPAHs in most rivers were demonstrated to be originated from other unknown sources besides the WWTPs effluent. The reduction from the original source, coal combustion (33% and 30%), was more efficient than from the wastewater treatment upgrading (15%) for the reduction of PAHs and SPAHs in the urban rivers.

Seasonal occurrence, source evaluation and ecological risk assessment of polycyclic aromatic hydrocarbons in industrial and agricultural effluents discharged in Wadi El Bey (Tunisia)

Polycyclic aromatic hydrocarbons are of great concern due to their persistence, bioaccumulation and toxic properties. The occurrence, source and ecological risk assessment of 26 polycyclic aromatic hydrocarbons in industrial and agricultural effluents affecting the Wadi El Bey watershed were investigated by means of gas chromatographic/mass spectrometric analysis (GC/MS). Total PAHs (∑ 26 PAH) ranged from 1.21 to 91.7 µg/L. The 4- and 5-ring compounds were the principal PAHs detected in most of 5 sites examined. Diagnostic concentration ratios and molecular indices were performed to identify the PAH sources. Results show that PAHs could originate from petrogenic, pyrolytic and mixed sources. According to the ecotoxicological assessment, the potential risk associated with PAHs affecting agricultural and industrial effluents ranged from moderate to high for both aquatic ecosystem and human health. The toxic equivalency factor (TEF) approach indicated that benzo[a]pyrene and benz[a]anthracene were the principal responsible for carcinogenic power of samples.

Sorptive removal of phenanthrene from aqueous solutions using magnetic and non-magnetic rice husk-derived biochars

A magnetically modified rice husk biochar (MBC) was successfully prepared by a hydrothermal method from original biochar (BC) and subsequently used to remove phenanthrene (PHE) from aqueous solutions. The porosity, specific surface area and hydrophobicity of BC were significantly improved (approx. two times) after magnetic modification. The adsorption data fitted well to pseudo-second-order kinetic and Langmuir models. Compared with BC, MBC had a faster adsorption rate and higher adsorption capacity of PHE. The adsorption equilibrium for PHE on MBC was achieved within 1.0 h. The maximum adsorption capacity of PHE on MBC was 97.6 mg g^-1 based on the analysis of the Sips model, which was significantly higher than that of other sources of BCs. The adsorption mechanism of the two BCs was mainly attributed to the action of surface functional groups and π-π-conjugated reactions. The adsorption of PHE on MBC mainly occurred in the functional groups of C-O and Fe₃O₄, but that on BC was mainly in the functional groups of -OH, N-H, C=C and C-O.

Sediment-associated polycyclic aromatic hydrocarbons and potential eco-hazards in Chabahar Bay, Iran

The surface sediments (0-4cm, n=6) from Chabahar Bay were analyzed to assess the concentrations, composition, and potential eco-hazards of associated PAHs. The range of ∑16 PAHs' concentration was 25.75-312.38ngg^-1 dw, with mean and median levels of 126.7 and 55.12ngg^-1 dw, respectively. The bay was classified as a region with low to moderate PAH pollution. The sources of PAHs varied, and 2-3-ring compounds were dominant (37-90%). There was no significant correlation between TOC/grain size and levels of PAHs. Total carcinogenic PAHs ranged from 0.21 to 79.68ngg^-1 dw, and benzo(a)pyrene was the main constituent of calculated toxic equivalencies. The bay sediments were rarely hazardous and could not address narcotic hazards for the benthic community. Biota-sediment accumulation was not predicted for the examined coral Acropora valida. In equilibrium conditions, release of ∑16PAHs from the bay sediments was estimated to be 0.536μgL^-1 at its maximum.

Four-dimensional data coupled to alternating weighted residue constraint quadrilinear decomposition model applied to environmental analysis: Determination of polycyclic aromatic hydrocarbons

Qualitative and quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) was carried out by three-dimensional fluorescence spectroscopy combining with Alternating Weighted Residue Constraint Quadrilinear Decomposition (AWRCQLD). The experimental subjects were acenaphthene (ANA) and naphthalene (NAP). Firstly, in order to solve the redundant information of the three-dimensional fluorescence spectral data, the wavelet transform was used to compress data in preprocessing. Then, the four-dimensional data was constructed by using the excitation-emission fluorescence spectra of different concentration PAHs. The sample data was obtained from three solvents that are methanol, ethanol and Ultra-pure water. The four-dimensional spectral data was analyzed by AWRCQLD, then the recovery rate of PAHs was obtained from the three solvents and compared respectively. On one hand, the results showed that PAHs can be measured more accurately by the high-order data, and the recovery rate was higher. On the other hand, the results presented that AWRCQLD can better reflect the superiority of four-dimensional algorithm than the second-order calibration and other third-order calibration algorithms. The recovery rate of ANA was 96.5%~103.3% and the root mean square error of prediction was 0.04μgL^-1. The recovery rate of NAP was 96.7%~115.7% and the root mean square error of prediction was 0.06μgL^-1.

Polycyclic aromatic hydrocarbons contamination in surface soil of China: A review

This paper reviews the concentration, distribution, source, and potential risk of polycyclic aromatic hydrocarbons (PAHs) in surface soils of China through analysis of data from >6000 surface soil samples in nearly 100 references. The mean value of total 16 PAHs was 730ng·g^-1 in surface soil in China, a relatively lower or moderate level than other countries. Based on the Maliszewska-Kordybach classification criteria, the proportions of heavily contaminated, contaminated, weakly contaminated, and non-contaminated soil samples were 21.4%, 11.9%, 49.5%, and 17.2%, respectively. There was a clear geographical distribution, with concentrations of the total 16 PAHs descending in the following order: Northeast China (1467ng·g^-1)>North China (911ng·g^-1)>East China (737ng·g^-1)>South China (349ng·g^-1)>West China (209ng·g^-1). Moreover, it was found that the PAH concentrations in surface soil in China descended along the urban-suburban-rural gradient. The concentration and distribution of PAHs were mainly related to the degree of economic development, population density, climatic conditions, and soil organic matter, and the divergence of regional economic patterns and climatic conditions was the main reason for the observed PAH distribution in the soils. Traffic emissions, coal and biomass combustion mainly contributed to the PAH contamination of surface soil in China during the process of urbanization and industrialization, and the average Benzo(a)pyrene equivalent concentration of ∑PAH_7c (seven carcinogenic PAHs) was 99ng·g^-1, which indicated the soil samples had a small potential carcinogenic risk. Despite soil pollution being generally low, PAH concentrations in some areas were relatively high, therefore it is necessary to produce strategies, such as establishing effective guidelines and developing environmental-friendly technology to reduce PAH emissions, and prevent further contamination.

Enhanced biodegradation of mixed PAHs by mutated naphthalene 1,2-dioxygenase encoded by Pseudomonas putida strain KD6 isolated from petroleum refinery waste

Polycyclic aromatic hydrocarbons (PAHs) are a group of environmental pollutant that are given top priority to maintain water and soil quality to the most amenable standard. Biodegradation of PAHs by bacteria is the convenient option for decontamination on site or off site. The aim of the present study was to isolate and identify naturally occurring bacteria having mixed PAHs biodegradation ability. The newly isolated Pseudomonas putida strain KD6 was found to efficiently degrade 97.729% of 1500 mg L-1 mixed PAHs within 12 days in carbon-deficient minimal medium (CSM). The half-life (t1/2) and degradation rate constant (k) were estimated to be 3.2 and 0.2165 days, respectively. The first-order kinetic parameters in soil by strain KD6 had shown efficient biodegradation potency with the higher concentration of total PAHs (1500 mg kg-1 soil), t1/2 = 10.44 days-1. However, the biodegradation by un-inoculated control soil was found slower (t1/2 = 140 days-1) than the soil inoculated with P. putida strain KD6. The enzyme kinetic constants are also in agreement with chemical data obtained from the HPLC analysis. In addition, the sequence analysis and molecular docking studies showed that the strain KD6 encodes a mutant version of naphthalene 1,2-dioxygenase which have better Benzpyrene binding energy (-9.90 kcal mol-1) than wild type (-8.18 kcal mol-1) enzyme (chain A, 1NDO), respectively, with 0.00 and 0.08 RMSD values. The mutated naphthalene 1,2-dioxygenase nahAc has six altered amino acid residues near to the ligand binding site. The strain KD6 could be a good bioresource for in situ or ex situ biodegradation of polycyclic aromatic hydrocarbon.

Characteristics, source, and potential ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the Songhua River Basin, Northeast China

The concentration characteristics, sources, and potential ecological risk assessment of 16 PAHs were investigated in the surface water from the Songhua River Basin, Northeast China. A total of 48 river water samples, including 16 from the main streams and 32 from the tributaries, were collected. Samples were separated into dissolved phases and suspended particle matter (SPM) via filtration with 0.47 μm glass fiber filters. Each phase was analyzed for PAHs. The total PAH concentration in the dissolved phase in the water ranged from 32.5 to 108 ng L^-1 and from 0.3 to 62.3 μg g^-1 (dry weight) in the suspended particle matter (SPM). The total PAH concentration in the main stream was lower than in the tributaries; the volume of annual runoff of rivers had a significant effect on the ƩPAH in the rivers. The 2- and 3-ring PAHs dominated in both the dissolved phase and SPM, indicating a relatively recent local source of PAHs in the study area. The concentrations of PAHs in the Songhua River Basin are lower when compared with the values previously reported in the literature from other rivers around the world. The sources of PAHs were assessed by diagnostic ratios and principal component analysis (PCA), and the ecological risk of the PAHs was assessed based on the risk quotient (RQ). The diagnostic ratios and PCA indicated that the main sources of PAHs originated from pyrogenic and petrogenic sources, and pyrogenic sources had a greater impact. The ecological risk assessment indicated that the PAHs presented low ecosystem risk in the Songhua River Basin.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Haihe River, a typical polluted urban river in Northern China

The distribution, sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments from the Haihe River. Total PAH concentrations varied from 171.4 to 9511.2 ng g^-1 with an average of 2125.4 ng g^-1, suggesting serious pollution of the Haihe River in comparison with other reported rivers worldwide. PAH contaminants differed significantly among 17 sampling locations with high values occurring in industrial areas and densely populated areas. The composition of PAHs was characterized by high abundance of 4-ring and 5-ring PAHs, and benzo[a]anthracene, chrysene, and benzo[a]pyrene were the predominant components. Molecular diagnostic ratios have confirmed that PAHs in Haihe River sediments resulted from mixed sources, primarily including various combustion processes. Ecological risk assessment using the Sediments Quality Guidelines indicated that PAHs in sediments could cause certain negative effects on aquatic organisms in most survey regions.

Origin, toxicological and narcotic potential of sedimentary PAHs and remarkable even/odd n-alkane predominance in Bushehr Peninsula, the Persian Gulf

Surface sediments (n=17) were collected from 6 sites located in the coasts of the Bushehr Peninsula. ∑₁₆PAH concentrations were in the range of 285.9-1288ngg^-1 dw and the sediments were moderately polluted. Py, Ph, B(a)A and Flu showed >70% of the detected values in order of the mentioned rank. 4-ring PAHs were the dominant compounds and the molecular ratios presented the dominant pyrolytic source. The toxicity of PAHs for sediment dwelling life was averagely equivalent to occurrence of 0.08ngg^-1 of Dioxin in dw of the examined sediments. The evaluated narcotic potential (confidence level of 99%) was 0.027-3.04 and upper part of the Bushehr Peninsula, where the human population is more concentrated, showed more narcotic potential. ∑n-alkane concentrations (n-C₁₅-n-C₃₂) were in the range of 3.10-35.6μgg^-1 dw. The dominant distribution of even carbon number n-alkanes was traced back to a possibly autochthonous source.

Spatial distribution and ecological risk assessment of phthalic acid esters and phenols in surface sediment from urban rivers in Northeast China

Concentration and spatial distribution of six phthalic acid esters (PAEs) and eight phenols in sediments of urban rivers, namely the Xi River (XR) and Pu River (PR) in Shenyang city, Northeast China were investigated and the ecological risk of these target pollutants was assessed based on the risk quotient (RQ) approach. Target PAEs and phenols were detected in most of sediment samples collected from the XR and PR. The concentrations of total PAEs in sediments varied from 22.4 to 369 μg/g dw in the XR and 3.71-46.9 μg/g dw in the PR. The levels of phenols ranged from 2.72 to 106 μg/g dw in the XR and 0.811-25.0 μg/g dw in the PR, respectively. The dominant pollutants in both XR and PR were DEHP, phenol and 4-methylphnol. The sampling locations XR1-3 in the XR suffered severe contamination from PAEs and phenols. The sites PR1 and PR6 were heavily polluted by phenols and PAEs, respectively. Almost all target PAEs and phenolic compounds in sediment of the XR exhibited medium or high ecological risk to organisms and the ecological risk in the PR mainly originated from PEAs, phenol and 4-methylphenol. These results would provide guidance for individual pollutant control and indicate that it is imperative to take some effective measures to reduce the pollution of those contaminants.

Consistency between health risks and microbial response mechanism of various petroleum components in a typical wastewater-irrigated farmland

Various petroleum components possess distinctive migration and toxicity characteristics. Evaluation of contamination levels on the basis of total concentrations of petroleum hydrocarbons in soil and groundwater is limited. Hunpu, a typical wastewater-irrigated area, is located at the southwest of Shenyang City, Liaoning Province, China. In this study, various fractions, exposure pathways, and soil microbial communities were taken into account to make petroleum contamination evaluation more effective and precise in the region. The concentrations and hazard quotients of aliphatic fractions, as the bulk of an oil, verified that the groundwater must not be drunk directly. The total concentrations of aliphatic hydrocarbons (TAHs) for C10-34 were 68.90-199.87 μg g(-1) in soil in Hunpu, which required cleanup according to Oklahoma criteria. However, both health and ecological risks indicated that petroleum contamination in surface soil was not serious. Microbes may use aliphatic fractions as carbon and energy source for their growth, which was indicated by positive correlation between them. TAHsC12-16 posed highest human health risks and had the most significant effect on the soil microbial composition, although its concentration was low in both the groundwater and the soil. Straight-, branched-chain saturated, and cyclopropyl phospholipid fatty acids had more closely positive correlation with TAHsC12-16, which indicated that regulation of bacterial membrane fluidity to toxic petroleum pollutants. This study can also provide the guidelines for assessment and management of petroleum contamination.

Heavy metals and polycyclic aromatic hydrocarbons in surface sediments of Karoon River, Khuzestan Province, Iran

Karoon is the longest river in Iran and provides water for industries located along its banks, such as metal, petrochemical, and oil industries. It is also the source of drinking water for cities such as Ahwas, Abadan, and Khorramshahr. In this study, 34 and 18 surface sediment samples were collected and analyzed for heavy metals (Al, As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) and polycyclic aromatic hydrocarbons (PAHs). The measured concentrations of heavy metals were compared with US EPA sediment quality guidelines, and the results showed that Cu concentration was above the threshold effect level (TEL) in 65.67% of the samples and Hg concentration was above the effect range median (ERM) in some samples. The results revealed that Hg was severely enriched (5 < enrichment factor < 20) and classified in very high ecological risk index category. It is the major metallic contaminant in the study area. The total PAH concentrations ranged from 11.54-117,730 μg/kg, with the mean value of 7034.55 μg/kg dominated by lower molecular weight (LMW) PAHs. The total potentially carcinogenic PAHs (∑cPAHs) in sediment samples ranged from 2.09 to 31,930 μg/kg, indicating high carcinogenic potential of sediments in the study area. The total toxic equivalent (TEQ) values ranged from 1.06 to 7228.7 μg/kg. Maximum TEQ occurred in Abadan oil refinery station followed by Khorramshahr soap factory and Abadan petrochemical complex. Principal component analysis and cluster analysis also revealed the relationships between the studied parameters and identified their probable sources.

Spatial and temporal distribution of aliphatic hydrocarbons and linear alkylbenzenes in the particulate phase from a subtropical estuary (Guaratuba Bay, SW Atlantic) under seasonal population fluctuation

Guaratuba Bay, a subtropical estuary located in the SW Atlantic, is under variable anthropogenic pressure throughout the year. Samples of surficial suspended particulate matter (SPM) were collected at 22 sites during three different periods to evaluate the temporal and spatial variability of aliphatic hydrocarbons (AHs) and linear alkylbenzenes (LABs). These compounds were determined by gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC/MS). The spatial distributions of both compound classes were similar and varied among the sampling campaigns. Generally, the highest concentrations were observed during the austral summer, highlighting the importance of the increased human influence during this season. The compound distributions were also affected by the natural geochemical processes of organic matter accumulation. AHs were associated with petroleum, derived from boat and vehicle traffic, and biogenic sources, related to mangrove forests and autochthonous production. The LAB composition evidenced preferential degradation processes during the austral summer.

Polycyclic aromatic hydrocarbons in sediments of China Sea

Increasing pollution pressures were placed in the coastal and estuarine ecosystems in China because of the elevated pollutants discharged from various sources. Polycyclic aromatic hydrocarbons (PAHs) in the environment were closely linked to human activities, which have been intensively studied for their geochemical interest as markers. In this review, the status of PAH contamination in China Sea was assessed by comprehensive reviews of the concentrations, sources, and fates of PAHs in sediments of China Sea. PAH concentrations in China Sea sediments decreased from north to south due to the higher emissions in North China. Atmosphere was probably the main carrier of PAHs in the north due to the higher contents of atmospheric fine particles and higher wind speeds. However, riverine inputs were probably the most important sources of PAHs in the coastal sediments of South China due to higher rainfall.

Distribution and risk assessment of hydrocarbons (aliphatic and PAHs), polychlorinated biphenyls (PCBs), and pesticides in surface sediments from an agricultural river (Durance) and an industrialized urban lagoon (Berre lagoon), France

The distributions of organic pollutants (like hydrocarbons, polychlorinated biphenyls (PCBs), and pesticides) and the risks on the ecosystem were studied in the Durance River and the Berre lagoon (France). High levels of aliphatic hydrocarbons were observed in all stations (1399 to 11,202 μg kg(-1) dw). The n-alkanes were mainly from terrigenous origin confirmed by the values of different ratios calculated (carbon preference index (CPI), natural n-alkanes ratio (NAR), terrigenous/aquatic ratio (TAR), and ratio of low molecular weight to high molecular weight (LMW/HMW)). Total polycyclic aromatic hydrocarbon (PAH) concentrations in the surface sediments of the Durance River and Berre lagoon are 57-1528 and 512-863 μg kg(-1) dw, respectively. Several ratios between parent polycyclic aromatic hydrocarbons showed that the sources of hydrocarbons in the sediments were generally more pyrolytic than petrogenic. The sum of seven PCB contents ranged from 0.03 to 13.13 μg kg(-1) dw. Higher levels of PCBs were detected in sediments from the northern parts of the Berre lagoon (stations B1 and B3). Total pesticides contents ranged from 0.02 to 7.15 μg kg(-1) dw. Among these compounds, ∑DDE and ∑DDT contents ranged, respectively, from 0.35 to 1.65 and from 0.37 to 1.52 μg kg(-1) dw. However, PAH and PCB levels are not high enough to be a threat to aquatic organisms and human beings. Total PAH levels were below the effects range low (ERL) of 3500 μg kg(-1) dw. For PCBs, only two stations (B1 and B3) are higher than the effect range median (ERM) of 180 μg kg(-1) dw. For endrin (pesticide), the concentrations are between the ERL (0.02 μg kg(-1) dw) and the ERM (45 μg kg(-1) dw).

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in sediments of Liaohe River: levels, spatial and temporal distribution, possible sources, and inventory

Spatial and seasonal variations of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the sediment of Liaohe River were investigated in this study. A total of 29 surface sediment samples were collected in May and September in 2013. Results showed that levels of the two classes of compounds were higher in September than in May. The total concentration of PBDEs (∑8PBDEs) ranged from 0.30 to 5.09 ng g(-1) in May and from 0.17 to 13.73 ng g(-1) in September, respectively, and BDE 209 was the dominant compound. The total concentration of PCBs (∑33PCBs) was in the range of 4.92-76.86 and 11.69-179.61 ng g(-1) in May and September, respectively, with tri- and tetra-CBs dominated in the total PCBs in the sediments. According to the congener profiles and the principal component analysis, the major sources of PCBs and PBDEs in sediments of Liaohe River were from the usage of commercial products and industrial activities, and the degradation of high brominated BDEs also contributed to the current PBDEs in the sediments. The mass inventories of PBDEs and PCBs in the sediments of Liaohe River were 1.74 and 21.96 t, respectively, indicating that Liaohe River sediments may act as the potential sources of PBDEs and PCBs to the downstream coastal areas.

Urban rivers as conveyors of hydrocarbons to sediments of estuarine areas: source characterization, flow rates and mass accumulation

Aliphatic (n-C12-n-C40, unresolved complex mixture, resolved peaks) and aromatic hydrocarbons (46 PAH) were investigated in suspended particulate matter (SPM) sampled over eleven months in six of the major rivers and two channels of the Guanabara Bay Basin. PAH flow rates of the most contaminated rivers, the contribution to the PAH sediment load of the receiving bay, and the main sources of hydrocarbons were determined. PAH (38) ranged from 28 ng L(-1) to 11,514 ng L(-1). Hydrocarbon typology and statistical evaluation demonstrated contribution of distinct sources in different regions and allowed quantification of these contributions. Total flow rate for the five major rivers amounts to 3 t year(-1) and responds for 30% of the total PAH annual input into the northern area of the Guanabara Bay. For the first time PAH mass deposited in the bay sediments has been estimated and shall serve as base for decision making and source abatement.

Origin, distribution and toxicological potential of polycyclic aromatic hydrocarbons in surface sediments from the Bushehr coast, the Persian Gulf

To evaluate the hazards of polycyclic aromatic hydrocarbons (PAHs) in the Bushehr coastal zones, 12 surface sediments were analyzed. The ∑14PAHs concentrations varied from 371 to 611 ng g(-1) dw. The primary sources of the observed PAHs were pyrolytic processes, demonstrating the dominance of petroleum-related combustion inputs. The ERL/ERM and TEL/PEL values showed that there was a moderate level of toxicity risk for some PAHs. The toxicological significance of the pollutants was assessed using the toxic equivalency factor (TEF) to calculate both the toxic equivalent for dioxins (TEQTCDD) and the TEQ carcinogenic risks. Dibenz(a,h)anthracene exhibited the highest proportion in the TEQs, ranging from 49% to 56% (TEQcarc) and from 29% to 39% (TEQTCDD) regarding the overall toxicity in the sampled sediments. This result suggests that the ambient dibenz(a,h)anthracene concentration represents the risk posed by PAHs in the sediments. Moreover, using a specific sediment criterion demonstrated the bioaccumulation potential of benzo(a)pyrene for humans in the sampled sediments.

Halophyte plant colonization as a driver of the composition of bacterial communities in salt marshes chronically exposed to oil hydrocarbons

In this study, two molecular techniques [denaturing gradient gel electrophoresis (DGGE) and barcoded pyrosequencing] were used to evaluate the composition of bacterial communities in salt marsh microhabitats [bulk sediment and sediment surrounding the roots (rhizosphere) of Halimione portulacoides and Sarcocornia perennis ssp. perennis] that have been differentially affected by oil hydrocarbon (OH) pollution. Both DGGE and pyrosequencing revealed that bacterial composition is structured by microhabitat. Rhizosphere sediment from both plant species revealed enrichment of operational taxonomic units closely related to Acidimicrobiales, Myxococcales and Sphingomonadales. The in silico metagenome analyses suggest that homologous genes related to OH degradation appeared to be more frequent in both plant rhizospheres than in bulk sediment. In summary, this study suggests that halophyte plant colonization is an important driver of hydrocarbonoclastic bacterial community composition in estuarine environments, which can be exploited for in situ phytoremediation of OH in salt marsh environments.

Sediment PAH: contrasting levels in the Caspian Sea and Anzali Wetland

A comparative study of 23 PAH congeners in sediment of the Caspian Sea coast and Anzali Wetland was conducted in 2010. Surface sediment was analyzed using chromatography and mass spectrometry. Total PAH concentrations ranged between 212 and 9009 ng g(-1) dw. Spatial distribution maps revealed that PAH levels were higher in the coastal areas of the Caspian Sea where oil related activities have been common since 1800's. Diagnostic ratios analysis indicated that PAHs largely originated from petrogenic processes. PAH toxicity level was assessed using sediment quality guidelines and toxic equivalent concentrations to determine toxic effects on marine organism. Based on these investigations, in our study areas, the probability of toxicity for benthic organisms is "low to medium". The toxic equivalent concentrations of carcinogenic PAHs varied between 11 and 231 ng TEQ/g; higher total toxic equivalent concentrations values were found in the coastal areas of the Caspian Sea.

Relating metal bioavailability to risk assessment for aquatic species: Daliao River watershed, China

The spatial distribution of metal bioavailability (Ni, Cu, Zn, and Pb) was first evaluated within the waters of Daliao River watershed, using the diffusive gradient in thin films (DGT) and chemical equilibrium models. To assess potential risks associated with metal bioavailability, site-specific 95% protection levels (HC5), risk characterizations ratios (RCR) and ratios of DGT-labile/HC5 were derived, using species sensitivity distribution (SSD). The highest bioavailability values for metals were recorded in the main channel of the Daliao River, followed by the Taizi River. Dynamic concentrations predicted by WHAM 7.0 and NICA-Donnan for Cu and Zn agreed well with DGT results. The estuary of the Daliao River was found to have the highest risks related to Ni, Cu, and Zn. The number of sites at risk increased when considering the total toxicity of Ni, Cu, and Zn.

Health risk assessment of semi-volatile organic pollutants in Lhasa River China

The semi-volatile organic compounds in Lhasa River were determined qualitatively and quantitatively by gas chromatography method with mass spectrometric detection. Total concentrations of 23 organic pollutants in samples from five sites ranged from 1.56 to 2.78 μg/L. The average concentrations for ΣPAEs, ΣPAHs and ΣBTEXs obtained in this study were 1.53, 0.33 and 0.51 μg/L, respectively. Moreover, the results of analysis of variable showed that there were significant differences (P < 0.05) among the sites for levels of ΣPAHs, ΣPAEs and ΣBTEXs. Cluster analysis was applied to detect spatial similarity for grouping of sites under the monitoring network. The results indicated that the five sites in this study could be divided into two significant groups, i.e. low and high pollutant groups. Health risk assessment was conducted by multimedia environmental goals (MEG), risk quotient (RQ) for each pollutant and hazard quotient (HQ) approach from USA ecological risk assessment (ERA) for screening stage. Calculated both total ambient severity and RQ were less than 1 and therefore minimal risk to human and ecological health. For analysis results of HQ, whether for the ingestion exposure or dermal adsorption pathway were all less than 1, the results also agreed with the RQ model and MEG model for evaluating the potential for adverse health effects due to exposure semi-volatile organic compounds from surface water. Therefore, SVOCs in Lhasa River posed little or no threat to the health of local consumers and ecological environment.

Petroleum contamination of soil and water, and their effects on vegetables by statistically analyzing entire data set

Aliphatic hydrocarbons have been used to assess total oil concentrations, petroleum sources, and petroleum degradation. In this study, surface soil, groundwater, surface water, and vegetables were collected from the outskirts of Xi'an, the largest city in northwestern China, and the samples were analyzed for aliphatic hydrocarbon contents. The concentrations of n-alkanes were 1.06-4.01 μg/g in the soil. The concentrations and the geochemical characteristics of n-alkanes showed that the low carbon number hydrocarbons were mainly from petroleum sources, whereas the high carbon number hydrocarbons received more hydrocarbons from herbaceous plants. The concentrations of n-alkanes were 9.20-93.44 μg/L and 23.74-118.27 μg/L in the groundwater and the surface water, respectively. The water had characteristics of petroleum and submerged/floating macrophytes and was found in concentrations that would cause chronic disruption of sensitive organisms. The concentrations and geochemical characteristics of n-alkanes in Brassica chinensis L. and Apium graveolens were different, but both were contaminated by petroleum hydrocarbons. The results from principal component analysis (PCA) indicated that the sorption of n-alkanes to soil particles could not be described by linear models. The distributions of n-alkanes in vegetables were positively correlated with those in soil, and the correlation coefficient was up to 0.9310 using the constructed vectors. Therefore, the researchers should pay close attention to the effect of soil contamination on vegetables.

Historical records of organic pollutants in sediment cores

Analyses of sediment core samples are primary sources of historical pollution trends in aquatic systems. Determining organic compounds, such as POPs, in the dated sediments enables the estimation of their temporal concentration changes and the identification of the contaminant origin in local regions. Wars, large-scale fires, economical transitions, and bans on certain chemicals are reflected in the sediment organic compound concentrations. The high POP concentrations in surficial sediments suggest that these chemicals, even after being banned, remain in the environment. Furthermore, vertical profiles can help in understanding the sedimentation process and in estimating effective countermeasures against pollution. Moreover, studies published during the period 1991-2013 on PAHs, PCBs, OCPs, dioxins and dioxin-like compound concentrations in sediment core samples are reviewed.

Effects of pollution sources and soil properties on distribution of polycyclic aromatic hydrocarbons and risk assessment

In this study, the concentrations of polycyclic aromatic hydrocarbons (PAHs) in soil profiles and the soil properties were analyzed in Hunpu, a typical wastewater irrigation area, northeast of China. The total concentrations of 16 priority control PAHs ranged from 7.88 to 2,231.42 μg/kg. Among 16 PAHs, the most abundant was Phenanthrene and the 3- or 4- ring PAHs were predominant. The PAH concentrations were higher in the upland fields near the oil wells, whereas leaching of PAH into the groundwater caused low concentrations in the paddy fields. The geochemical indices and the results from the principal component analysis of all 16 PAHs indicated that PAHs were mainly from atmospheric dusts in the top soil in I-1P/I-3P/I-7P and through soil profiles in I-4U/I-5P/I-8U, whereas those in the bottom layers were mainly from petroleum production and wastewater irrigation in I-1P/I-3P/I-7P and through soil profiles in I-2U and I-6U. In the redundancy analysis, PAHs exhibited negative correlation with pH, depth, silt, and clay, but had positive correlation with sand and organic matter. Finally, total toxic equivalent in the soil profiles and the calculated health risk of PAHs in the surface soil using contaminated land exposure assessment model elucidated the cancer risk that PAHs pose on human health in the Hunpu region.

Distribution and sources of polycyclic aromatic hydrocarbons in the surface water of Taizi River, Northeast of China

Spatial and seasonal distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs), identified as priority pollutants by the US Environmental Protection Agency, were investigated in the surface water of the Taizi River in Liaoning Province, northeast of China. Samples were collected from the mainstream, and tributaries of the Taizi River in dry, wet, and normal seasons. Five important industrial point sources were also monitored. The total PAH concentrations ranged from 454.5 to 1,379.7 ng l(-1) in the dry season, 1,801.6 to 5,868.9 ng l(-1) in the wet season, and 367.0 to 5,794.5 ng l(-1) in the normal season. The total PAH concentrations were significantly increased in the order of wet season > normal season > dry season. The profile of PAHs in the surface water samples was dominated by low molecular weight PAHs particularly with two- and three-ring components in the three seasons, suggesting that the PAHs were from a relatively recent local source. Source identification inferred that the PAHs in the surface water of the Taizi River came from both petrogenic inputs and pyrogenic sources.

Contamination and ecological risk assessment of toxic trace elements in the Xi River, an urban river of Shenyang city, China

The objectives of this study were to assess the enrichment, contamination, and ecological risk posed by toxic trace elements in the sediments of the Xi River in the industrialized city of Shenyang, China. Surface sediment and sediment core were collected; analyzed for toxic trace elements; and assessed with an index of geoaccumulation (Igeo), enrichment factor (EF) value, potential ecological risk factor (Er), ecological risk index (RI), and probable effect concentration quotient (PECQ). Elemental concentrations (milligram per kilogram) were 8.5-637.9 for As, 6.5-103.9 for Cd, 12.2-21.9 for Co, 90.6-516.0 for Cr, 258.1-1,791.5 for Cu, 2.6-19.0 for Hg, 70.5-174.5 for Ni, 126.9-1,405.8 for Pb, 3.7-260.0 for Sb, 38.4-100.4 for V, and 503-4,929 for Zn. The Igeo, EF, Er, and PECQ indices showed that the contamination of Cd and Hg was more serious than that of As, Cr, Cu, Ni, Pb, Sb, and Zn, whereas the presence of Co and V might be primarily from natural sources. The Igeo index for Cr and Ni might underestimate the degree of contamination, potentially as a result of high concentrations of these elements in the shale. The RI index was higher than 600, indicating a notably high ecological risk of sediment for the river. The average PECQ for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn ranged from 1.4 to 4.1 for surface sediment and from 5.2 to 9.6 in the sediment cores, indicating a high potential for an adverse biological effect. It was concluded that the sediment in the Xi River was severely contaminated and should be remediated as a hazardous material.

Using variances in hydrocarbon concentration and carbon stable isotope to determine the important influence of irrigated water on petroleum accumulation in surface soil

Hunpu is a wastewater-irrigated area southwest of Shenyang. To evaluate petroleum contamination and identify its sources at the area, the aliphatic hydrocarbons and compound-specific carbon stable isotopes of n-alkanes in the soil, irrigation water, and atmospheric deposition were analyzed. The analyses of hydrocarbon concentrations and geochemical characteristics reveal that the water is moderately contaminated by degraded heavy oil. According to the isotope analysis, inputs of modern C3 plants and degraded petroleum are present in the water, air, and soil. The similarities and dissimilarities among the water, air, and soil samples were determined by concentration, isotope, and multivariate statistical analyses. Hydrocarbons from various sources, as well as the water/atmospheric deposition samples, are more effectively differentiated through principal component analysis of carbon stable isotope ratios (δ(13)C) relative to hydrocarbon concentrations. Redundancy analysis indicates that 57.1 % of the variance in the δ(13)C of the soil can be explained by the δ(13)C of both the water and air, and 35.5 % of the variance in the hydrocarbon concentrations of the soil can be explained by hydrocarbon concentrations of both the water and the air. The δ(13)C in the atmospheric deposition accounts for 28.2 % of the δ(13)C variance in the soil, which is considerably higher than the variance in hydrocarbon concentrations of the soil explained by hydrocarbon concentrations of the atmospheric deposition (7.7 %). In contrast to δ(13)C analysis, the analysis of hydrocarbon concentrations underestimates the effect of petroleum contamination in the irrigated water and air on the surface soil. Overall, the irrigated water exerts a larger effect on the surface soil than does the atmospheric deposition.

Distribution of polycyclic aromatic hydrocarbons in surface water and sediment near a drinking water reservoir in Northeastern China

The levels of polycyclic aromatic hydrocarbons (PAHs) in the water and the sediment samples collected near the Mopanshan Reservoir-the most important drinking water resource of Harbin City in Northeast China-were examined. A total of 16 PAHs were concurrently identified and quantified in the three water bodies tested (Lalin River, Mangniu River, and Mopanshan Reservoir) and in the Mopanshan drinking water treatment plant during the high- and low water periods. The total PAH concentrations in the water and sediment samples ranged from 122.7 to 639.8 ng/L and from 89.1 to 749.0 ng/g dry weight, respectively. Similar spatial and temporal trends were also found for both samples. The lowest Σ16PAH concentration of the Mopanshan Reservoir was obtained during the high water period; by contrast, the Lalin River had the highest concentration during the low water period. The PAH profiles resembling the three water bodies, with high percentages of low-molecular weight PAHs and dominated by two- to three-ring PAHs (78.4 to 89.0%). Two of the molecular indices used reflected the possible PAH sources, indicating the main input from coal combustion, especially during the low water period. The conventional drinking water treatment operations resulted in a 20.7 to 67.0% decrease in the different-ringed PAHs in the Mopanshan-treated drinking water. These findings indicate that human activities negatively affect the drinking water resource. Without the obvious removal of the PAHs in the waterworks, drinking water poses certain potential health risks to people.