Polycyclic aromatic hydrocarbons (PAHs) in water and sediment of Hoor Al-Azim wetland, Iran: a focus on source apportionment, environmental risk assessment, and sediment-water partitioning

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.

Potentially toxic elements contamination in the water resources: an integrated risk assessment approach in the upper Citarum watershed area

The Citarum watershed is West Java Province's most important water resource; hence, harmful compounds should be monitored regularly. This study assessed pollution levels along with ecological and health risks from Cd, Pb, Mn, Fe, Cu, Cr, and Hg contamination in river water, sediment, groundwater, and soil in Citarum's upper watershed. In river water, the average amounts of Cd, Pb, Mn, Fe, Cu, Cr, and Hg were 0.002, 0.05, 0.092, 0.649, 0.022, 0.001, and 0.421 mg/L. In sediment, they were 7.4, 1175.1, 32,289.9, 37.3, 3.9, and 0.015 mg/kg. The mean concentrations of Cd, Pb, Mn, Fe, Cu, Cr, and Hg in groundwater were 0.004, 0.046, 0.567, 0.366, 0.019, 0.001, and 0.177 mg/L, and in soil, BDL, 10.2, 744.6, 50,094.1, 45.6, 5.9, and 0.015 mg/kg. The river water and groundwater were highly polluted by PTEs, with HPI values of 14,733 and 933, respectively. While PTEs pollution levels and risk in sediment and soil were low based on I-geo, CF, PLI, and M-ERM-Q values, PTEs contamination in river water may cause adverse impacts on aquatic living organisms (HQ > 1). The population doing recreational activities in river ecosystems was still safe from non-carcinogenic and carcinogenic impacts due to PTEs exposure from river water and sediment (THI < 1 and TCR value < 1E-04), while the population in the upper Citarum River was not safe from the carcinogenic risk due to PTE exposure from groundwater and soil (TCR > 1E-04). The sensitivity analysis showed that Cd concentration in groundwater is the most influential factor in cancer risk, with a total contribution of 99.9%. Therefore, a reduction in Cd concentration in groundwater is important to reduce cancer risk in the population.

Does mangrove leave falling dominate the bury of polycyclic aromatic hydrocarbons in the mangrove of China?

Mangrove wetlands are vital coastal ecosystems that can absorb and accumulate pollutants. Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that pose potential risks to ecosystems and human health. However, their source and transport fate in mangrove areas are poorly understood. This study investigates 29 PAHs pollution of water and sediment in Zhangjiangkou Mangrove Wetland, the northernmost large-scale mangrove wetland reserve in China. We examine the distribution, source, transport mechanisms and risk assessment of PAHs. The results show that the concentrations of PAHs in mangrove sediment range from 55.62 to 347.36 ng/g (DW), with 5-ring PAHs being the dominant species. While the concentrations of PAHs in surface water range from 10.61 to 46.39 ng/L, with 2-ring PAHs and alkylated PAHs being the dominant species. The PAHs concentrations in surface water and sediment of river are higher than those in mangrove area, indicating that mangrove water could receive PAHs through tidal exchange. Based on diagnostic ratios (DRs), principal component analysis (PCA), and positive matrix factorization (PMF), we infer that the leaf deposition (48.55%) could be an important pathway of PAHs in mangrove sediment except for river water transport (51.45%), while the PAHs in estuary water originate mainly from point sources such as biomass burning (50.96%) and traffic emission (49.04%). The range of toxic equivalents in surface water and sediment was 2.73-16.09 ng TEQ g-1 and 0.03-3.63 ng/L, respectively. Although the ecological risk assessment suggests that the PAHs pollution in surface water and sediment poses a low risk, we recommend more attention to the protection of the mangrove ecosystem. This study reveals that mangrove leaf falling might be a significant mechanism of PAH sequestration in the mangrove system, which deserves more attention in future research.

Spatial distribution and source apportionment of surface soil's polycyclic aromatic hydrocarbons in the Yangtze River Delta

Soil acts as a crucial reservoir of polycyclic aromatic hydrocarbons (PAHs) in the environment, and its PAH content serves as a significant indicator of regional PAH pollution. Monitoring PAH levels in soil is important for assessing the potential risks to human and environmental health. In this study, 53 surface soil samples were collected from the Yangtze River Delta. These samples were monitored for 16 priority PAHs. Pollution levels, compositional profiles, and source differences of soil PAHs were analyzed among different regions, urban and rural areas, and functional zones. The total PAH content (Σ16PAHs) in the surface soil of the Yangtze River Delta was 2326.01 ± 2901.53 ng/g. High-ring PAHs (4-6 rings) accounted for the predominant portion (85.50%) of total PAHs. The average pollution level of soil PAHs in Jiangsu Province (2651.92 ± 3242.87 ng/g) was significantly higher than that of Zhejiang Province (2001.44 ± 2621.71 ng/g) and Shanghai (1669.13 ± 1758.34 ng/g), and high-ring PAHs constituted a predominant portion in these three regions. There was no significant difference in the PAH content between urban and rural areas. In different functional areas, automobile stations exhibited the highest PAH levels among the functional zones analyzed, with traffic emissions identified as a major source of soil PAH in this area. The primary factors influencing the distribution of soil PAHs in the study area were the duration of urbanization exposure (r = 0.753, p < 0.01) and soil organic carbon content (r = 0.452, p < 0.01). This provides novel evidence for the cumulative build-up of PAHs during urbanization. The positive matrix factorization model was used to analyze the sources of PAHs in the surface soil of the Yangtze River Delta, revealing that biomass and coal combustion (60.19%) and traffic emissions and coal combustion (31.82%) were the primary sources of PAHs in the region.

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.

Investigation of the concentration, origin and health effects of PAHs in the Anzali wetland: The most important coastal freshwater wetland of Iran

This study investigated the concentration of PAHs in 19 water samples, 34 sediment samples and 22 fish samples of Anzali Wetland, located in north of Iran. The average concentration of ∑PAHs in the wetland sediment was 89.19 μg/kg (8.28-806.64) and 78.31 ng/L (5.14-253.37) in the wetland water. Also, the average concentration of ∑PAHS in the muscle of the investigated fish in the wetland was 23 μg/kg (56.1 to 7.6). The source apportionment of PAHs in water and sediment considering isomeric ratios and statistical methods reveals the predominance of petrogenic origin of the compounds in water and pyrogenic origin in sediment. Overall, the level of contamination in fish is relatively low to moderate, considering ∑PAHs. The findings present clear evidence of low to moderate level of contamination in the wetland, the PAHs contamination however could cross their ecological thresholds in future unless control measures are taken to protect the wetland.

Occurrence and source of PAHs in Miankaleh International Wetland in Iran

We examined the occurrence and sources of 16 priority PAHs in the water and sediment samples of the Miankaleh Wetland (Coastal Biosphere Reserve), famous for harbouring huge flocks of migrating birds. The water and sediment samples collected from various locations were visualized and processed using a self-organizing map, positive matrix factorization and GIS. All the sediment samples, and >90% of the water samples, showed some degree of PAHs contamination. Higher PAH levels occur near the Chopoghi Channel, powerplants, sewage outfalls, and near fishing operations. Compared with previous study in this area, the PAHs concentration in the sediments of aquatic ecosystem of Miankaleh Wetland is increasing. The levels of PAH contamination seem too low to account for the mass deaths of migratory birds, and botulinus contamination seems the likely cause. Fugacity calculations show that the sediments act as a sink for PAHs. According to PMF and SOM analyses, three origins of PAHs were recognized: (i) fossil fuel and vehicular emissions with high-molecular weight PAHs (4-5 ring); (ii) municipal and industrial sewages characterized by low-molecular weight PAHs (2-3 ring) typical of petrogenic sources; and (iii) port activity characterized by prevalence of petrogenic influence and petroleum-related activities (combustion PAHs and low-molecular weight PAHs) consistent with port activity. This wetland needs serious attention because of continuous input of pollutants. The results and the methods used in this study may assist in improving coastal wetlands management.

Seasonal assessment of the distribution, source apportionment, and risk of water-contaminated polycyclic aromatic hydrocarbons (PAHs)

The research aims to evaluate the seasonal differences in the distribution, source, and risks of water-contaminated PAHs. The PAHs were extracted by the liquid-liquid method and analyzed with GC-MS, and a total of eight PAHs were detected. There was a percentage increase in the average concentration of the PAHs from the wet to the dry season in the range of 20 (Anthracene)-350 (Pyrene)%. Total PAHs (∑PAHs) range from 0.31 to 1.23 mg/l in the wet period and from 0.42 to 1.96 mg/l in the dry period. The distribution of the average PAHs in mg/l showed that Fluoranthene ≤ Pyrene < Acenaphthene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in wet period and while Fluoranthene < Acenaphthene < Pyrene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in the dry period. The children were exposed to non-carcinogenic risk through non-dietary ingestion due to the accumulative effect (HI) of the PAHs in the dry period. Furthermore, the naphthalene was responsible for ecological and carcinogenic risk in the wet period, while the fluorene, phenanthrene, and anthracene were responsible for ecological and carcinogenic risk in the dry period. However, while adults and children are both susceptible to carcinogenic risk through the oral channel during the dry period, only children are susceptible to non-carcinogenic risk through this pathway. The multivariate statistical analysis revealed the influence of physicochemical parameters on the detected PAHs and also showed the PAHs' sources to be mainly combustion, pyrolysis, and vehicular emission.

The Relationship Between Dust Sources and Airborne Bacteria in the Southwest of Iran

The biological agents are carried from deserts and dried lands to long distances by high dust volumes. Their adverse effects can be reduced by specifying and controlling dust sources and their related biological agents. Thus, the current work examined the relationship between the bacteria in air and soil samples by taking samples from the soil surface of two dust sources, as well as from air samples during spring from Khorramshahr and Abadan cities. The dust event is the most influential factor on airborne bacteria. There is an insignificant negative (-0.06), insignificant positive (0.14), and weak positive (0.24) correlation between airborne bacteria and UV radiation, relative humidity, and temperature, respectively. After preparing a 16S ribosomal DNA (rDNA) clone library from the soil and air samples, operational taxonomic unit picking and taxonomic assignment were conducted using QIIME Virtual Box. In the present work, Bacillus was the dominant species. The relationship between dust sources and air samples was determined by principal component analysis. Bacteria in the Hoor-Al-Azim dust source and airborne bacteria on dusty and non-dusty days showed a more significant correlation compared to bacteria in the Shadegan dust source. Source Tracker software was used to estimate the contribution of dust sources. The primary source of dust was associated with the dried areas of Hoor-Al-Azim on the non-dusty and dusty days. Finally, the long transport of airborne bacteria was assessed by moderate resolution imaging spectroradiometer (MODIS) and the back trajectory model of Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) data. The research findings can help decision-makers prioritize dust sources to control the adverse effects of dust.

Polycyclic Aromatic Hydrocarbons (PAHs) in the Dissolved Phase, Particulate Matter, and Sediment of the Sele River, Southern Italy: A Focus on Distribution, Risk Assessment, and Sources

The Sele River, located in the Campania Region (southern Italy), is one of the most important rivers and the second in the region by average water volume, behind the Volturno River. To understand the distribution and sources of polycyclic aromatic hydrocarbons (PAHs) in the Sele River, water sediment samples were collected from areas around the Sele plain at 10 sites in four seasons. In addition, the ecosystem health risk and the seasonal and spatial distribution of PAHs in samples of water and sediment were assessed. Contaminant discharges of PAHs into the sea were calculated at about 1807.9 kg/year. The concentration ranges of 16 PAHs in surface water (DP), suspended particulate matter (SPM), and sediment were 10.1–567.23 ng/L, 121.23–654.36 ng/L, and 331.75–871.96 ng/g, respectively. Isomeric ratio and principal component analyses indicated that the PAH concentrations in the water and sediment near the Sele River were influenced by industrial wastewater and vehicle emissions. The fugacity fraction approach was applied to determine the trends for the water-sediment exchange of 16 priority PAHs; the results indicated that fluxes, for the most part, were from the water into the sediment. The toxic equivalent concentration (TEQ) of carcinogenic PAHs ranged from 137.3 to 292.6 ngTEQ g⁻¹, suggesting that the Sele River basin presents a definite carcinogenic risk.

Eutrophication and sediment-water exchange of total petroleum hydrocarbons and heavy metals of Hashilan wetland, a national heritage in NW Iran

The heavy metal(loid)s concentrations in water and sediments were analyzed in the Hashilan wetland to assess the spatial distribution, pollution status, fate, partitioning, and ecological risk and also to identify the heavy metal(loid)s sources in sediments using PMF (Positive Matrix Factorization) and APCs-MLR (absolute principal component score-multiple linear regression) receptor models. According to the pollution indices, (Ni, Cu, Cr, Mo), and (Zn, Cr, and Cu) are considered the most important pollutants in sediments and water, respectively. Ni, Cr, and Cu are the main contributors to ecological risks in sediments of some stations. The potential ecological risk assessment proposed low ecological risk in water of the study area. Higher distribution coefficient (Kp) values of Ni, Cr, Mn, Cu, Co, Pb, As, and Zn indicated the majority of these heavy metals present in the sediments; whereas, the majority of Cd concentration occurs in water. PMF and APCs-MLR results indicated the natural sources were the main factors affecting the concentrations of Ni, Cr, Zn, Al, Co, Fe, Pb, As, Cd and somewhat Cu. Mixed natural and agricultural activities are the main sources of Mo, and somewhat Cu. According to the results, there is low pollution of TPH (total petroleum hydrocarbons) in the sediment samples. Also, phosphate (PO42-) and nitrate (NO3-) concentrations were below the recommended permissible limits at all sampling sites except the S8 station for NO3-.

COVID-19 and urban rivers: Effects of lockdown period on surface water pollution and quality- A case study of the Zarjoub River, north of Iran

Due to the spreading of the coronavirus (COVID-19) in Iran, restrictions and lockdown were announced to control the infection. In order to determine the effects of the lockdown period on the status of the water quality and pollution, the concentrations of Al, As, Ba, Cr, Cu, Mo, Ni, Pb, Se, and Zn, together with Na+, Mg2+, Ca2+ and electrical conductivity (EC), were measured in the Zarjoub River, north of Iran, in both pre-lockdown and post-lockdown periods. The results indicated that water pollution and associated human health risk reduced by an average of 30% and 39%, respectively, during the lockdown period. In addition, the multi-purpose water quality index also improved by an average of 34%. However, the water salinity and alkalinity increased during the lockdown period due to the increase of municipal wastewater and the use of disinfectants. The major sources of pollution were identified as weathering, municipal wastewater, industrial and agricultural effluents, solid waste, and vehicular pollution. PCA-MLR receptor model showed that the contribution of mixed sources of weathering and municipal wastewater in water pollution increased from 23 to 50% during the lockdown period. However, the contribution of mixed sources of industrial effluents and solid wastes reduced from 64 to 45%. Likewise, the contribution of traffic-related sources exhibited a reduction from 13% in the pre-lockdown period to 5% together with agricultural effluent in the post-lockdown period. Overall, although the lockdown period resulted in positive impacts on diminishing the level of water pollution caused by industrial and vehicular contaminants, the increase of municipal waste and wastewater is a negative consequence of the lockdown period.

Trend analysis of anthropogenic activities affecting trace metals deposition in core sediments from the coastal and four rivers estuary of Sarawak, Malaysia

This study reports the concentrations of trace metals in core sediments profile from the coastal and four rivers estuary in the Kuching Division of Sarawak, Malaysia, and the controlling mechanisms influencing their availability in sediments of the studied area. The bonding of trace metals with non-mobile fractions was confirmed with the sequential extraction. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to measure the concentrations of the trace metals. Granulometric analyses were performed using normalized sieve apertures to determine the textural characteristics of the sediments. Enrichment factor was used to evaluate the level of metal enrichment. Heavy metals concentrations in sediment samples varied in the range: Pb (8.9-188.9 mg/kg d.w.), Zn (19.4-431.8 mg/kg d.w.), Cd (0.014-0.061 mg/kg d.w.), Ni (6.6-33.4 mg/kg d.w.), Mn (2.4-16.8 mg/kg d.w.), Cu (9.4-133.3 mg/kg d.w.), Ba (1.3-9.9 mg/kg d.w.), As (0.4-7.9 mg/kg d.w.), Co (0.9-5.1 mg/kg d.w.), Cr (1.4-7.8 mg/kg d.w.), Mg (68.8-499.3 mg/kg d.w.), Ca (11.3-64.9 mg/kg d.w.), Al (24.7-141.7 mg/kg d.w.), Na (8.8-29.4 mg/kg d.w.), and Fe (12,011-35,124.6 mg/kg d.w.). The estimated results of the enrichment factor suggested enrichments of Pb, Zn, and Cu in all the core sediment samples and depths at all sites. The other trace metals showed no enrichments in almost all the sampled stations. Continuous accumulation of Pb, Zn, and Cu metals over a period can be detrimental to living organisms and the ecology. The results obtained from the statistical analyses suggested that the deposition of trace metals in the studied sites is due to anthropogenic inputs from the adjacent land-based sources.

Trace metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in the surface sediments from Sanya River, China: Distribution, sources and ecological risk

The urban inland river ecosystems are now facing comprehensive pollution and governance pressures. Up to now, few works related to the multiple pollution assessment of trace metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) for the urban inland river sediments have been reported in China. Our study investigated the spatial distribution, ecological risk and potential sources of trace metals, PAHs and PCBs in surface sediment collected from 20 sampling sites of Sanya River, Hainan Province, China. The pollution status and potential ecological risk of trace metals were evaluated using the contamination indexes including geoaccumulation index (I_geo), individual potential ecological risk (E_rⁱ), potential ecological risk index (RI) and pollution load index (PLI). Considering the carcinogenicity and toxicity of PAHs and PCBs to human health and the ecological environment, we also analyzed the distributions, sources and adverse biological effects of PAHs and PCBs according to the sediment quality guidelines (SQGs), principal component analysis (PCA) and other source analysis. This study revealed that the surface sediments in Sanya River were extremely slight pollution and showed a very low ecological risk according to I_geo, E_rⁱ, PLI and RI results for trace metals. Besides, PAHs and PCBs pollution detected may not pose considerable adverse biological effect to ecological environment in a foreseeable period on the basis of comprehensive research results. The overall surface sediments quality of the Sanya River not seem to pose a serious pollution and ecological risk based on the evaluation results of multiple pollution factors. The study provided detailed information on the multiple pollution status and location of surface sediments, one of the key environmental indicators of international tourism cities, in the Sanya River, which would be useful for the water quality improvement of Sanya River and the environmental remediation of the other coastal ecosystems from different regions.

Integration of chemical and biological methods: A case study of polycyclic aromatic hydrocarbons pollution monitoring in Shandong Peninsula, China

Polycyclic aromatic hydrocarbons (PAHs), as persistent toxic substances (PTS), have been widely monitored in coastal environment, including seawater and sediment. However, scientific monitoring methods, like ecological risk assessment and integrated biomarker response, still need massive researches to verify their availabilities. This study was performed in March, May, August and October of 2018 at eight sites, Yellow River estuary (S1), Guangli Port (S2), Xiaying (S3), Laizhou (S4), Inner Bay (S5), Outer Bay (S6), Hongdao (S7) and Hongshiya (S8) of Shandong Peninsula, China. The contents of 16 priority PAHs in local seawater and sediment were determined, by which ecological risk assessment risk quotient (RQ) for seawater and sediment quality guidelines (SQGs) were calculated to characterize the PAHs pollution. Meanwhile, multiple biomarkers in the digestive gland of clam Ruditapes philippinarum were measured to represent different biological endpoints, including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), sulfotransferase (SULT), superoxide dismutase (SOD) and lipid peroxidation (LPO), by which integrated biomarker response (IBR) was calculated to provide a comprehensive assessment of environmental quality. Taken together, these results revealed the heaviest pollution at S2 as both PAHs concentrations and biomarkers responses reflected, and supported the integrated biomarker response as a useful tool for marine environmental monitoring, through its integration with SQGs.

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

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

Spatial distribution, partitioning, ecological risk and source apportionment of potential toxic elements in water and sediments of the Hoor Al-Azim wetland and their bioaccumulation in selected commercial fish species

The potentially toxic elements (PTEs) concentrations in water and sediments were measured in the Hoor Al-Azim wetland to evaluate the spatial distribution, pollution rate, fate, partitioning, and ecological risk and also to recognize the PTEs sources in sediments using MLR-APCs (multiple linear regression-absolute principal component scores) receptor model. The human health risk was investigated based on the seven fish species consumed in the study area. Based on the results, water and sediment contamination was observed at some stations in the southern part of the wetland where agricultural water drains. Also, the sediments of oil well drilling disposal site was polluted by PTEs. Based on the MLR-APCs model, 80.8% of Mo and 81.5% of Se originated from agricultural source. Total target hazard quotients (TTHQ) values suggested that the children could experience adverse health effects due to consumption of Coptodon zillii, Aspius vorax, Carassius auratus and Carasobarbus luteus.

Remediation of soils and sediments polluted with polycyclic aromatic hydrocarbons: To immobilize, mobilize, or degrade?

Polycyclic aromatic hydrocarbons (PAHs) are generated due to incomplete burning of organic substances. Use of fossil fuels is the primary anthropogenic cause of PAHs emission in natural settings. Although several PAH compounds exist in the natural environmental setting, only 16 of these compounds are considered priority pollutants. PAHs imposes several health impacts on humans and other living organisms due to their carcinogenic, mutagenic, or teratogenic properties. The specific characteristics of PAHs, such as their high hydrophobicity and low water solubility, influence their active adsorption onto soils and sediments, affecting their bioavailability and subsequent degradation. Therefore, this review first discusses various sources of PAHs, including source identification techniques, bioavailability, and interactions of PAHs with soils and sediments. Then this review addresses the remediation technologies adopted so far of PAHs in soils and sediments using immobilization techniques (capping, stabilization, dredging, and excavation), mobilization techniques (thermal desorption, washing, electrokinetics, and surfactant assisted), and biological degradation techniques. The pros and cons of each technology are discussed. A detailed systematic compilation of eco-friendly approaches used to degrade PAHs, such as phytoremediation, microbial remediation, and emerging hybrid or integrated technologies are reviewed along with case studies and provided prospects for future research.

Bioaccumulation of polycyclic aromatic hydrocarbons in Solea solea from Bizerte and Ghar El Melh Lagoons (Tunisia) and human health risk assessment

The present study objective was to assess polycyclic aromatic hydrocarbons in Bizerte and Ghar El Melh Lagoons Solea solea and to assess the potential risk to human health from its consumption. To reach these objectives twenty fish samples from each site were collected and 15 priority polycyclic aromatic hydrocarbons (PAHs) were analyzed in their muscles using high-performance liquid chromatography with a fluorescence detector. Total PAH sole concentrations from Bizerte and Ghar El Melh Lagoons were similar or lower to those recorded in other species from other regions across the world. In the studied fish species, the 2 and 3 ring PAHs are the dominated compounds that enter to the composition of PAHs which indicates that PAHs could be principally derived from a petrogenic origin for the both studied lagoons. The human health risk by sole consumption was evaluated and revealed to exhibit no hazard to the local population health concerning PAH intakes. The findings of this biomonitoring study will help in the implementation of sustainable environmental policies for effective water pollution control and the two investigated lagoons management.

Polycyclic aromatic hydrocarbons in sedimentary cores of Tibetan Plateau: Influence of global warming on cold trapping

Cold condensation is an important pathway for polycyclic aromatic hydrocarbons (PAHs) depositing at remote alpine lakes after long-range atmospheric transportation. However, in the context of global warming, the obvious temperature rise in the Tibetan Plateau (TP) might have an impact on the air deposition of PAHs by controlling the extent of cold condensation. To investigate the influence of rising temperatures on the atmospheric deposition of PAHs, two dated sedimentary cores from Pumoyum Co Lake (PC) and Selin Co Lake (SC) were collected, respectively and concentrations of 16 individual PAHs were measured. In both PC and SC, the total concentration of 16 PAHs presented relatively lower levels in four historical periods of "hot anomaly" including 1973-1975, 1988-1989, 1998-1999, and 2006-2007. This indicated that the hot temperatures might restrict the atmospheric deposition of PAHs. Besides, the results of the principal component analysis did discriminate those "hot anomalies". As the temperature kept increasing in TP, for low molecular weight PAHs and high molecular weight PAHs, the influence of rising temperatures on the cold condensation was different. Therefore, it was identified that the effect of global warming on the environmental fate of POPs cannot be neglected, especially in alpine regions like TP.

Spatial and temporal variations of PAHs in surface sediments of estuarine and coast of CanGio wetland, Vietnam

Surface sediments from estuarine and coast of CanGio wetland (CGW) of Hochiminh City, Vietnam, were investigated to identify the spatial and temporal variations of polycyclic aromatic hydrocarbons (PAHs). The total PAHs showed wide variation but similar to patterns observed (F = 0.901, p = 0.46) in LongTau (31 ± 77 ng/g dry weight, n = 13), SoaiRap (53 ± 81, n = 4), ThiVai (60 ± 62, n = 10) estuaries, and coastal areas (112 ± 211, n = 9). A decreasing trend in the wet season (F = 8.8, p = 0.01) reflected that inland sources such as wastewater discharged and atmospherically transported contaminants contributed to PAHs in sediments. The risk posed by the PAHs in the coastal and estuarine areas of CGW is still negligible. The present study provides baseline data, which can be used for regular monitoring and future strategy of environmental protection for the study area.

QuEChERS with Ultrasound-Assisted Extraction Combined with High-Performance Liquid Chromatography for the Determination of 16 Polycyclic Aromatic Hydrocarbons in Sediment

Background

Polycyclic aromatic hydrocarbons (PAHs) have attracted worldwide attention due to their carcinogenic, teratogenic, and mutagenic effects, environmental persistence, and bioaccumulation characteristics. Therefore, the sensitive, reliable, and rapid detection of PAHs in sediment is of great importance.

Objective

To develop a high-performance liquid chromatography (HPLC) with fluorescence and ultraviolet detection after Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) treatment for simultaneous determination of 16 U.S. Environmental Protection Agency priority PAHs in sediment samples.

Method

The samples were ultrasonically extracted with acetone and then the supernatant was purified with a modified QuEChERS method. After centrifugation, the supernatant was injected into the HPLC system for analysis. The separation was accomplished on a ZORBAX Eclipse PAH column (150 × 4.6 mm, 3.5 μm) and the column temperature was set at 30 °C. The flow rate of the mobile phase consisting of water and acetonitrile in gradient elution mode was fixed at 0.9 mL/min. Detection was conducted on an ultraviolet detector and a fluorescence detector simultaneously. The qualitative analysis was based on retention time and the quantification was based on standard curves.

Results

Under the optimal conditions, this method showed good linearities in the range of 10–200 μg/L with correlation coefficients greater than 0.9993. The method had LODs ranging from 0.00108 to 0.314 ng/g. The mean recoveries ranged from 78.4 to 117% with intra-day and inter-day RSDs of 0.592–10.7% and 1.01–13.0%, respectively. The proposed method was successfully applied to the detection of 16 PAHs in sediment samples collected from the Funan River in Chengdu, China with total contents of 431–2143 ng/g·dw.

Conclusions

The established method is simple, rapid, environmentally friendly, and cost-effective. It can be applied to the analysis of 16 PAHs in sediment samples.

Highlights

A method of QuEChERS with ultrasound-assisted extraction combined with HPLC has been established for the analysis of 16 PAHs in sediment samples and the proposed method has been successfully applied to the analysis PAHs in real sediment samples.

Copula-based exposure risk dynamic simulation of dual heavy metal mixed pollution accidents at the watershed scale

Most heavy metal exposure and pollution results from multiple industrial activities, including metal processing in refineries, and microelectronics. These issues pose a great threat to human health, ecological balance, and even societal stability. During 2012-2017, China, in particular, faced the challenge of 23 heavy metals accidents, six of which were extraordinarily serious accidents. Accidental environmental pollution is rarely caused by a single heavy metal, but rather by heavy metal mixtures. To address the need for a joint exposure risk assessment for heavy metal mixed pollution accidents at the watershed scale, a Copula-based exposure risk dynamic simulation model was proposed. A coupled hydrodynamic and accidental heavy metal exposure model is constructed for an hourly simulation of the exposure fate of heavy metals from each risk source once accidental leakage has occurred. The Copula analysis was introduced to calculate the dual heavy metal joint exposure probability in real time. This method was applied to an acute Cr⁶⁺-Hg²⁺ joint exposure risk assessment for 43 electroplating plants in nine sub-watersheds within the Dongjiang River downstream basin. The results indicated seven risk sources (i.e., S1, S4, H18, H23, H27-H28, and H34) that presented relatively high exposure risk to their surrounding sub-watersheds. Spatially, the acute exposure risk level was highest in the tributary basin (sub-watershed XW) than in the mainstream (sub-watershed DW2) and the river network (sub-watershed RW) of the lower reaches of the Dongjiang River. This research highlights an effective probabilistic approach for performing a joint exposure risk analysis of heavy metal mixed pollution accidents at the watershed scale.

Sedimentary polycyclic aromatic hydrocarbons (PAHs) along the mouth bar of the Yangtze River Estuary: Source, distribution, and potential toxicity

The source, distribution, and potential toxicity of sedimentary polycyclic aromatic hydrocarbons (PAHs) along the mouth bar of the Yangtze River Estuary were investigated. Total concentrations of 17 PAHs in the study area ranged from 34.94 to 580.26 ng/g (mean value 146.31 ng/g). Results of PMF model revealed that mixed vehicle emissions (38.43%), natural gas combustion (24.98%), biomass combustion (20.76%) and coal combustion (15.83%) were sources of these sedimentary PAHs. The ERL/ERM, TEL/PEL and TEC/PEC values showed that the potential toxicity of PAHs was at low to medium level, but the presence of benzo[a]pyrene (BaP) and benzo[e]pyrene (BeP) requires more attention and research. Sedimentary PAHs pollution level in the three shoals (East Nanhui Shoal, Jiuduansha Shoal and Hengsha Shoal) was higher than that of the two passages (South Passage and North Passage), which demonstrates the possibility of restoration of the adjacent shoals by dredged soils in terms of PAHs pollution.

Improved comprehensive ecological risk assessment method and sensitivity analysis of polycyclic aromatic hydrocarbons (PAHs)

Based on the existing comprehensive ecological risk assessment methods of PAHs, this paper proposed an improved hierarchical Archimedean copula integral assessment (HACIA) model with the optimization in the model selection mechanism and accelerating the calculation speed, and according to which performed the sensitivity analysis of the integrated risk relative to the underlying grouped risk probability. Taihu Lake in China and the Bay of Santander in Spain were taken as study areas, whose samples were obtained and extracted concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs). After briefly analyzing their concentration characteristics and source, their comprehensive ecological risks were evaluated by the improve HACIA model and their sensitivity was also analyzed. The results proved that, for Taihu Lake, pyrogenic sources occupied the dominance, especially grass, coal and wood combustion, while the risk proportion of 5-rings PAHs was the lowest indeed based on the improved HAICA model. For the Bay of Santander, source apportionment indicated both petrogenic and pyrogenic sources, mainly from vehicle emissions including gasoline and diesel engines, and 4-ring PAHs were urgently needed to be managed. However, the sensitivity analysis results of two study areas showed that the most effective control target for reducing integral risk has no obvious relationship with the maximum grouped risk. And a clear linear relationship between the maximum sensitivity range and the logarithm of the initial overall risk only presented in one of study areas, which required further research to clarify. In brief, the improved HACIA model is helpful to evaluate the comprehensive ecological risk of 16 PAHs, and formulate risk management strategies based on grouped risk assessment and sensitivity analysis, with the former points out the admonitory risk and the latter helps to find the most effective mitigation measures.

Soil PAHs against varied land use of a small city (Tezpur) of middle Brahmaputra Valley: seasonality, sources, and long-range transport

This study reports soil PAHs from a small city (Tezpur) of the mid-Brahmaputra Valley. The soil PAHs has been assessed from representative land use using detailed protocol of extracting, cleaning, and quantitative analysis by HPLC technique. The concentrations of PAHs showed minimum spatial variability and yet showed strong seasonal variability, which could be typical of small cities having weak local source strengths. On examining the air mass reaching the region, it appeared that there has been explicit effect of long-range transport. The HYSPLIT back trajectories reaching the study area during different seasons showed variations in terms of their origins and transport pathways. This might have led to differential long-range transport of PAHs, which is reflected in the seasonal variabilities of the concentrations of PAHs. The seasonal variations were much profound with the highest ΣPAHs concentration during post-monsoon (7961 ng g^-1) followed by pre-monsoon (2414 ng g^-1) and monsoon (773 ng g^-1) season. The toxicity of the PAHs was examined as BaP equivalent (BaPeq) concentrations, which were found to be on the lower side as compared to the studies conducted elsewhere. The percentage contribution of 3- and 4-ring compounds was found to be greater. An attempt also was made to apportion the sources of the PAHs by application of diagnostic ratios, principal component analysis-multiple linear regression (PCA-MLR) and hierarchal cluster analysis (HCA), which revealed that coal and biomass burning and vehicular emissions are the major contributors to the PAHs load in Tezpur city.

Characteristics, distribution, source and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in sediments along the Yangtze River Estuary Deepwater Channel

Characteristics, distribution, source, and ecological risk level of polycyclic aromatic hydrocarbons (PAHs) in sediments along Yangtze River Estuary Deepwater Channel were investigated. Total concentration of fifteen PAHs of study area ranged between 89.52 and 208.02 ng/g (mean value 140.48 ng/g). PAHs ratios and the statistical analysis showed that local fossil fuels high-temperature combustion (vehicular exhaust, anthropogenic combustion and pyrogenic sources) was the main PAHs origin. According to sediment quality guidelines (SQGs) and other criteria, the potential ecological risks of PAHs in sediments along Yangtze River Estuary Deepwater Channel are at low to medium levels, but the presence of dibenzo[a,h]anthracene (DBahAnt) requires more study and evaluation of potential toxicological effects.