Co-occurrence of organophosphate esters and phosphorus fractions in river sediments: Implications for pollution prediction and environment risk assessment.

Organophosphate esters (OPEs) and phosphorus (P) are widespread pollutants in aquatic ecosystems, presenting potential ecological risks. However, there is still a lack of comprehensive understanding of their relationships in sediments. In this study, we investigated the co-occurrence and behaviors of the OPEs and P in urban river sediments. The results indicated serious OPE and P pollution in the study area, with substantial spatial variations in the contents and compositions. The OPE congeners and P fractions exhibited different correlations, particularly more significant linear relationships (R = 0.455 - 0.816, p < 0.05) were observed between the aryl-OPEs and P fractions, potentially due to the influence from sources, physicochemical properties, and total organic carbon. About 56 to 71% of variability in predicting the concentrations of aryl-OPE can be explained by the multiple linear regression model using the Fe/Al- and Ca-bound P contents. The study regions exhibited greater aryl-OPEs ecological risks were consistent with the regions with more serious Total P pollution levels. This study represents the first report demonstrating the potential of Fe/Al-P and Ca-P contents in predicting aryl-OPE contents in heavily polluted sediments, providing a useful reference to comprehensively assess the occurrence and environmental behaviors of aryl-OPEs in anthropogenic polluted sediments.

Profiles and spatial distributions of heavy metals, microbial communities, and metal resistance genes in sediments from an urban river.

The occurrence and propagation of resistance genes due to exposure to heavy metals (HMs) in rivers is an emerging environmental issue. Little is known about resistance genes in microbial communities in river sediments with low HM concentrations. The profiles and spatial distributions of HMs, the microbial community, and metal resistance genes (MRGs) were analyzed in sediment samples from the Zhilong River basin in Yangjiang city, near the Pearl River Delta. Concentrations of copper (Cu), cadmium (Cd), lead (Pb), chromium (Cr), and nickel (Ni) were relatively low compared with those in other urban river sediments in China. HM chemical composition and fractions and the structure of the microbial community varied along the main channel, but the composition and abundance of MRGs were relatively homogeneous. Variations in HMs and microbial communities in mid- to upstream areas were related to the presence of tributaries, whose inputs were one of the major factors affecting HM chemical fractions and genera structure in mainstream sediments. There were no significant correlations (p < 0.05) between HM concentrations, bacterial communities, and the MRG profiles; thus, HM concentrations were not the main factor affecting MRGs in sediments. These results contribute to understanding the propagation of MRGs in urban rivers in developing cities.

Spectral change of dissolved organic matter after extracted by solid-phase extraction and its feasibility in predicting the acute toxicity of polar organic pollutants in textile wastewater.

Spectroscopic parameters can be used as proxies to effectively trace the occurrence of organic trace contaminants, but their suitability for predicting the toxicity of discharged industrial wastewater with similar spectra is still unknown. In this study, the organic contaminants in treated textile wastewater were subdivided and extracted by four commonly-used solid-phase extraction (SPE) cartridges, and the resulting spectral change and toxicity of textile effluent were analyzed and compared. After SPE, the spectra of the percolates from the four cartridges showed obvious differences with respect to the substances causing the spectral changes and being more readily adsorbed by the WAX cartridges. Non-target screening results showed source differences in organic micropollutants, which were one of the main contributors leading to their spectral properties and spectral variations after SPE in the effluents. Two fluorescence parameters (C1 and humic-like) identified by the excitation emission matrix-parallel factor analysis (EEM-PARAFAC) were closely correlated to the toxicity endpoints for Scenedesmus obliquus (inhibition ratios of cell growth and Chlorophyll-a synthesis), which can be applied to quantitatively predict the change of toxicity effect caused by polar organic pollutants. The results would provide novel insights into the spectral feature analysis and toxicity prediction of the residual DOM in industrial wastewater.

Toxic effects of microplastics in plants depend more by their surface functional groups than just accumulation contents.

Differentially charged microplastics (MPs) engendered by plastic aging (e.g., plastic film) widely existed in the agricultural ecosystem, yet minimal was known about the toxic effects of MPs on plants and their absorption and accumulation characteristics. Root absorption largely determined the migration and accumulation risks of MPs in the soil-crop food chain. Here, five types of MPs exposure experiments of leaf lettuce were implemented to simulate root absorption by hydroponics. MPs exposure caused different degrees of growth inhibition, root lignification, root cell apoptosis, and oxidative stress responses; accelerated chlorophyll decomposition and hampered normal electron transfer within the PSII photosystem. Moreover, the uptake of essential elements by roots was inhibited to varying degrees due to the pore blockage in the cell wall and the hetero-aggregation of opposite charges after MPs exposure. MPs exposure observably up-regulated the organic metabolic pathways in roots, thus affecting MPs mobility and absorption through the electrostatic and hydrophobic interactions between the root exudations and MPs. Importantly, MPs penetrated the root extracellular cortex into the stele and were transported to the shoots by transpiration through xylem vessels based on confocal laser scanning microscopy and scanning electron microscopy images. Quantitative analysis of MPs indicated that their toxic effects on plants were determined to a greater extent by the types of surface functional groups than just their accumulation contents, that is, MPs were confirmed edible risks through crop food chain transfer, but bioaccumulation varied by surface functional groups.

Tracing the occurrence of organophosphate ester along the river flow path and textile wastewater treatment processes by using dissolved organic matters as an indicator.

Organophosphate esters (OPEs) are frequently detected in wastewater and receiving river, but their occurrence is hard to be quickly and effectively responded. In this study, the relevant OPEs and dissolved organic matters (DOMs) data were obtained from two textile wastewater treatment plants (WWTPs) with different processes and a 15 km stretch of river receiving the treated textile wastewater. UV-Vis absorption and fluorescence spectroscopy combined with peak-picking and fluorescence regional integration (FRI) methods were used to characterize DOM components in these samples. The results showed that OPEs concentrations were not always consistent with that of DOM, but were related to their physico-chemical properties and sources. Correlation and regression analysis indicated that the FRI pattern could be considered for tracing the occurrence of organophosphate diesters derived from multiple pollutants in river water, and reflected the emerging of moderate or high removal organophosphate triesters in WWTPs. Difference in the sources and DOM compositions was the main contributor to the correlation difference of OPEs and DOM in the two types of processes. The treatment technique also played important roles in the co-occurrence of OPEs and DOM in different WWTPs. This study would be beneficial to develop in-situ monitoring for the dynamic change of emerging contaminants along with a river flow path and from WWTPs, respectively.

Occurrence, ecotoxicological risks of sulfonamides and their acetylated metabolites in the typical wastewater treatment plants and receiving rivers at the Pearl River Delta.

Sulfonamides (SAs) were frequently detected in various environmental water bodies because of their incomplete removal during wastewater treatment process, and this may lead to a negative effect on aquatic ecosystems. This study investigated six SAs and three of their acetylated metabolites in the influents, effluents, and the receiving river waters from four typical wastewater treatment plants (WWTPs) at the Pearl River Delta in Guangdong province, China. The results indicated that sulfadiazine, sulfapyridine and sulfamethoxazole had the highest detection frequency. Moreover, sulfadiazine and sulfamethoxazole had its maximum concentrations (216 ng/L and 200 ng/L, respectively) in the influent during dry season. To evaluate the compound degradability, the removal efficiency of each individual sulfonamide was calculated, and a modified method to assess it was recommended considering the widespread inter-conversion between SAs and their metabolites. Finally, regarding the effluent and river water, potential environmental risk based on the Hazard quotients (HQs) was estimated towards three diverse non-targeted organisms. Sulfamethoxazole was assessed with the highest HQ (>3.6), being the sole sulfonamide that would pose a risk to algae in the effluents and river waters. Thus, SAs emission needs to be further reduced from WWTPs into the environment.

Polybrominated diphenyl ethers and alternative halogenated flame retardants in mollusks from the Chinese Bohai Sea: Levels and interspecific differences.

Polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs) were measured in eleven mollusk species collected from the Chinese Bohai Sea. PBDEs and AHFRs were detected in all species, and their average total concentrations were in the range of 22.5-355 and 10.0-84.3 ng/g lipid weight, respectively. Decabromodiphenyl ether (BDE-209) and decabromodiphenylethane (DBDPE) were the dominant halogenated flame retardants (HFRs), contributing 22.5% to 73.6% and 3.1% to 38.3% of the total HFRs, respectively. The levels of PBDEs and AHFRs were moderate to high from a global perspective. Interspecific differences in the accumulation of PBDEs and AHFRs were characterized by heat map and cluster analysis. Composition profile differences were also observed, with higher proportions of AHFRs in gastropods than in bivalves. These species-specific differences in concentrations and profiles in mollusks were attributed to different species traits, including feeding habit, trophic level, and metabolic potential.

Organophosphate Triesters and Diester Degradation Products in Municipal Sludge from Wastewater Treatment Plants in China: Spatial Patterns and Ecological Implications.

Little is known about the occurrences, distributions, sources, and potential risks of organophosphate (OP) triesters and diester degradation products in municipal sludge from wastewater treatment plants (WWTPs). In this study, we conducted the first nationwide survey to simultaneously determine a suite of 11 OP triesters and six diester degradation products in sludge from WWTPs across China. All OP triesters were detected and three diesters were identified for the first time in sludge samples. Total concentrations of OP triesters and diester degradation products were in the ranges of 43.9-2160 and 17.0-1300 ng (g of dry weight)-1, respectively, indicating relatively low pollution levels in China compared with those of several developed countries. A distinct geographical variation of higher concentrations of OP triesters and diesters in East China than in Central and West China was observed, suggesting that regional levels of organophosphate esters are associated with the magnitudes of regional economic development. Source analysis revealed nonchlorinated OP diesters are mainly derived from degradation in WWTPs, while chlorinated OP diesters were largely sourced from outside WWTPs. The estimated total emission fluxes of OP triesters and diesters via land-application sludge in China were approximately 330 and 134 kg/year, respectively. Further risk assessment based on risk quotient values in sludge-applied soils indicated low to medium risks for most OP triesters and diesters except tris(methylphenyl) phosphate. The significant accumulation of OP triesters and widespread occurrence of diester degradation products in sludge raise environmental concerns about these contaminants.