Pollution and Risk of PAHs in Surface Sediments from the Tributaries and Their Relation to Anthropogenic Activities, in the Main Urban Districts of Chongqing City, Southwest China

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

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

Polycyclic aromatic hydrocarbons in the surface water and sediment along Euphrates River system: Occurrence, sources, ecological and health risk assessment

This study presented for the first time a comprehensive measurement campaign of 16 PAHs along the Euphrates River for five months, in both water and sediment samples. Our study revealed that the PAHs contamination increased along the flow direction due to the increasing non-point pollution and the return flows of agriculture. The 5-6 rings PAHs were dominant in water and sediment samples with an average of 42 % and 50 %, respectively. The diagnostic ratios of PAHs suggest that the pollution of these compounds originated mainly from petroleum product combustions. The carcinogenic PAHs formed 46 % and 55 % of the total measured compounds in water and sediment samples, respectively, which highlights potential ecological and human health risks. Based on sediment quality guidelines (SQGs), most sites exhibit an effect range between low and medium. The calculated incremental lifetime cancer risk (ILCR) for adult and children were in the 10^-2-10^-3 range, which is 3-6-fold higher than what was reported in the literature. These observations call for urgent attention from environmental authorities of countries sharing this key water source in Western Asia.

Effect of incubation time of three single extraction procedures on trace element extraction from sediment and soil

The use of standard single-extraction procedures to evaluate the mobility and availability of trace elements is a common practice in most laboratories dealing with soil or sediment analysis. Most standard single-extraction procedures describe incubations last for 2 h. However, these were tested and validated for soil analysis. Applying them for sediment analysis without further investigation might be misleading and should be reviewed with care. This paper investigates the effect of incubation time on the extraction efficiency of three standard single-extracting reagents (0.01 M CaCl₂, 1 M NH₄NO₃, and 0.05 M EDTA). Incubation experiments with sediment and soil samples lasting for 2 h, 10 h, and 10 d were performed. The results indicated that 2 h appears sufficient to reach equilibrium using CaCl₂ or NH₄NO₃ for soil analysis; but when analyzing sediments, incubation for 10 d resulted in higher concentrations. Incubation experiments with 0.05 M EDTA showed that incubation for 2 h was enough to extract Cd from the soil sample, Mn and to a lesser extent Cd from the sediment samples; while for the other elements, incubation for 10 d yielded higher concentrations for both sample types compared to that obtained after 2 h and 10 h separately. Relative to the pseudo-total metal contents, more than 55% of all studied elements were extracted by using 0.05 M EDTA, indicating high bioavailable metal fraction.

Sediment record in pollution, toxicity risk, and source assignment of polycyclic aromatic hydrocarbons (PAHs) in Erhai Lake, Southwest China

Surface sediments and sediment core had been collected from Erhai Lake, Southwest China to study the concentrations, toxicity risks, and sources of polycyclic aromatic hydrocarbons (PAHs). The average concentrations of Σ₁₆PAHs, seven carcinogenic PAHs (carPAHs), and carcinogenic toxic equivalents (TEQ^car) in the surface sediments and sediment core were 1634.50 ± 488.56 ng g^-1 and 436.72 ± 128.17 ng g^-1, 67.18-293.65 ng g^-1 and 91.07-265.90 ng g^-1, and 34.89 ± 13.17 ng g^-1 and 36.99 ± 7.52 ng g^-1, respectively. The Σ₁₆PAHs and carPAHs concentrations in surface sediments were higher in the southern lake. The Σ₁₆PAHs and TEQ^car in the sediment core peaked in the 2010s and 1980s. The spatiotemporal variations in TEQ^car and carPAHs were similar. Positive matrix factorization revealed that traffic emissions contributed 35.71 % of the TEQ^car, whereas coal and biomass combustion contributed 12.89 % in the surface sediments. The contribution of gasoline and fossil fuel to TEQ^car significantly increased from 19.2 % (1890s) to 66.5 % (1990s), that of benz[a]pyrene (coal combustion) decreased, and those of benz[b]fluoranthene and indeno[1,2,3-cd]pyrene (petroleum combustion and traffic emissions) increased from 1.92 % to 3.93 % and from 1.54 % to 2.52 % in the sediment cores, respectively, owing to changes in energy consumption.

Toxicity determination, pollution source delineation, and microbial diversity evaluation of PAHs-contaminated sediments for an urban river

The Feng-Sang River is a metropolitan river in Kaohsiung City, Taiwan. In this study, Feng-Sang River sediments were analyzed to investigate the distributions and sources of polycyclic aromatic hydrocarbons (PAHs). The Sediment Quality Guidelines (SQGs), potentially carcinogenic PAHs (TEQcarc ), and toxic equivalence quotient (TEQ) were applied to evaluate influences of PAHs on ecosystems and microbial diversities. Results indicate that PAHs concentrations varied between seasons and locations. The concentrations of ∑16 PAHs ranged from 73.6 to 603.8 ng/kg in dry seasons and from 2.3 to 199.3 ng/kg in wet seasons. This could be because of the flushing effect during wet seasons, which caused the movement and dilution of the PAH-contaminated sediments. Diagnostic ratio analysis infers that high PAHs levels were generated by combustion processes and vehicle traffic, and results from multivariate descriptive statistical analysis also demonstrate that the vehicular traffic pollution could be the major emission source of PAHs contamination. Comparisons of PAHs with SQGs indicate that PAHs concentrations in sediment were below the effects range low (ERL) values, and thus, the immediate threat to organisms might not be significant. The diagnostic ratio analyses are effective methods for PAH source appointment. The metagenomic assay results imply that sediments contained essential microbial species with eminent diversity. The detected PAH-degrading bacteria (Desulfatiglans, Dechloromonas, Sphingomonas, Methylobacterium, Rhodobacter, Clostridium, and Exiguobacterium) played a key role in PAHs biotransformation, and Dechloromonas and Rhodobacter had a higher relative abundance. Results of microbial diversity analyses indicate that the contaminated environment induced the changes of governing microbial groups in sediments. PRACTITIONER POINTS: Diagnostic ratio analyses are effective methods for PAHs source appointment. Microbial composition in sediments are highly affected by anthropogenic pollution. Combustion and vehicle traffic contribute to urban river sediments pollution by PAHs. Dechloromonas and Rhodobacter are dominant PAHs-degrading bacteria in sediments.

PAHs Source Identification in Sediments and Surrounding Soils of Poyang Lake in China Using Non-Negative Matrix Factorization Analysis

Identifying sources of soil and sediment PAHs and apportioning their contributions are key in building effective pollution abatement strategies, especially for Poyang Lake—the largest freshwater lake in China. PAHs were detected in all the monitored soil and sediment samples under three land use types, with the concentrations varying by area, ranging from moderate to relatively high. The order of PAHs content in different the land use types was as follows: industrial soil > grassland soil > agricultural soil. Although agricultural soil was dominated by LMW PAHs, industrial grassland soils were dominated by HMW PAHs. Based on factor analysis, non-negative matrix factorization analysis was effective in non-negative constrained skew rotation, especially for clear and interpretable source analysis of PAHs.

Distribution of Nitrogen and Phosphorus in Pore Water Profiles and Estimation of Their Diffusive Fluxes and Annual Loads in Guanting Reservoir (GTR), Northern China

Improvement of water quality has frequently been delayed due to high recycling rates of nutrients across the sediment-water interface in a reservoir. Diffusive fluxes and annual loads of ammonia nitrogen (NH₄⁺-N) and phosphate (PO₄^3--P) in sediments from Guanting Reservoir (GTR) were estimated according to their vertical distribution. The average contents of NH₄⁺-N and PO₄^3--P in surface pore water were higher by factors of 6.9 - 11.7 and 1.3 - 6.4 than those in overlying water, respectively. The ranges of fluxes were 1.59 - 13.0 (mg m² d^-1) for NH₄⁺-N, and 0.002 - 0.196 (mg m² d^-1) for PO₄^3--P. The annual load contributions from sediments of GTR were 659 t a^-1 for NH₄⁺-N and 4.83 t a^-1 for PO₄^3--P. Notably, the upstream of GTR accounted for 50.7% annual loads for NH₄⁺-N, while the downstream contributed 71.2% loads to PO₄^3--P. This study will better inform future environmental management for the reservoir.

Spatial Distributions, Sources and Risks of Polycyclic Aromatic Hydrocarbons in Sediments from Ziya River System, Northern China

With the development of urbanization and industrialization, Ziya River Plain (ZYRP) had become one of the most polluted regions of polycyclic aromatic hydrocarbons (PAHs) in north China. The distribution of PAHs in sediments were investigated, and then their sources and risks were evaluated. The results showed that the total PAHs varied from 3372 to 92,948 μg/kg, and heavy pollution was found in the upstream. Both the isomer pair ratios of PAH and principal components analysis (PCA) revealed that fossil fuel combustion was the mainly contributes (69.1%), followed by wood and coal combustion (26.7%). The ecological risk for the whole area was moderate, with the highest risk in Niuwei River (NWR). and significant correlation was found between the ecological risk and high-molecular-weight (HMW) of PAHs (r² > 0.99, p < 0.01). Our findings would give insights into the mitigation of sedimentary PAHs pollution in north China.

Occurrences, Retention and Risk Assessments of PAHs in Beidagang Wetland in Tianjin, China

Coastal wetlands are the last barriers for pollutants from land to the sea. In this study, a coastal wetland that locates in the lower reach of Haihe River Systems was selected to speculate the removal and retention of polycyclic aromatic hydrocarbons (PAHs) by analyzing their spatial distributions and the changes of composition. The results showed that the overall removal efficiency of PAHs in water phase was 58.1%. There was an accumulation for sedimentary PAHs, reaching 431 ng/g (181 ng/g in the inlet). The compositions of sedimentary PAHs were also changed, high-molecular-weight PAHs were the main component (70-50%), with a steady decreasing trend and the influence of water flow direction. The risk assessment by mean effect range media quotients (M-ERM-Qs) depicted that there was in low ecological risk, due to the degradation of PAHs in the wetlands. Our results clearly demonstrated the coastal wetlands could effectively retain the PAHs, thus we recommend an active protection strategy for the coast wetlands in Tianjin in the future.

Coking wastewater treatment plant as a sources of polycyclic aromatic hydrocarbons (PAHs) in sediments and ecological risk assessment

The spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in sediments of Maba River, a major tributary of Beijiang River (South China). A total of 13 samples from Maba River and its tributary, Meihua River, were analyzed for 16 PAHs. The total concentration of 16 PAHs (ΣPAH) in high and low water period ranged between 47.61 to 25480.98 ng g-1, with a mean concentration of 4382.98 ng g-1, and 60.30 to 15956.62 ng g-1 with a mean concentration of 3664.32 ng g-1, respectively. Three-ring and four-ring PAHs were the dominant species. It was concluded that a pattern of pyrolytic input as a major source of PAHs in sediments through the molecular ratio method for the source identification, such as HMW/LMW PAHs, Flu/(Flu+Pyr), IcdP/(IcdP+BghiP) and BaA/(BaA+Chr). It is suggested that the pollution emission from the iron and steel plant might be the most important sources of PAHs into Maba River water system. The threat of PAHs contamination to biota of the river was assessed using effect range low (ERL) and effect range median (ERM) values, which suggested that PAHs in Maba River and its tributary had already caused ecological risks.

Sorption kinetics of parent and substituted PAHs for low-density polyethylene (LDPE): Determining their partition coefficients between LDPE and water (KLDPE) for passive sampling

Low-density polyethylene (LDPE) has been widely used as a sorbent for passive sampling of hydrophobic organic contaminants (HOCs) in aquatic environments. However, it has seen only limited application in passive sampling for measurement of freely dissolved concentrations of parent and substituted PAHs (SPAHs), which are known to be toxic, mutagenic and carcinogenic. Here, the 16 priority PAHs and some typical PAHs were selected as target compounds and were simultaneously determined by gas chromatography-mass spectrometer (GC-MS). Some batch experiments were conducted in the laboratory to explore the adsorption kinetics of the target compounds in LDPE membranes. The results showed that both PAHs and SPAHs could reach equilibrium status within 19-38 days in sorption kinetic experiments. The coefficients of partitioning between LDPE film (50 μm thickness) and water (K_LDPE) for the 16 priority PAHs were in good agreement with previously reported values, and the values of K_LDPE for the 9 SPAHs are reported in this study for the first time. Significant linear relationships were observed, i.e., log K_LDPE = 0.705 × log K_OW + 1.534 for PAHs (R² = 0.8361, p < 0.001) and log K_LDPE = 0.458 × log K_OW + 3.092 for SPAHs (R² = 0.5609, p = 0.0077). The selected LDPE film was also proven to meet the condition of "zero sink" for the selected target compounds. These results could provide basic support for the configuration and in situ application of passive samplers.