Emerging persistent organic pollutants in Chinese Bohai Sea and its coastal regions

Enrichment, bioaccumulation and human health assessment of organochlorine pesticides in sediments and edible fish of a plateau lake

The organochlorine pesticides (OCPs) are with features of persistence, high toxicity, bioaccumulation and adverse impact on ecosystems and human beings. Although OCPs pollutions have been observed in the plateau lakes, comprehensive understandings in the distribution characteristics and human health risks of OCPs in these valuable but fragile ecosystems are limited. We here investigated the distribution, bioaccumulation process and health risks of OCPs in the Jianhu lake, a representative plateau lake in China. The endrin ketone, endrin aldehyde and heptachlor were the most dominant species in surface and columnar sediments. Their total contents ranged between 0 ~ 1.92 × 103 ng·g-1. The distribution of OCPs in sediment cores combined with chronology information indicated that the fast accumulation of OCPs happened during the last decades. Combining the distribution features of OCPs in different sources with mixing model results of carbon isotope (δ13C), farming area was identified as the main source (46%), and the OCPs were transported to lake by inflow-rivers (37%). The enrichment of OCPs in sediments caused considerable bioaccumulation of OCPs in local fish (∑OCPs 0-3199.93 ng·g-1, dw) with the bio-sediment accumulation factor (BSAF) ranging from ND to 9.41. Moreover, growing time was another key factor governing the accumulation in specific species (Carassius auratus and Cyprinus carpio). Eventually, the carcinogenic risk index (CRI) and exposure risk index (ERI) of the endrin category and aldrin exceeded the reference value, indicating relatively high health risks through consumption of fish. Overall, this study systematically illustrated the bioaccumulation process and health risks of OCPs in the typical plateau lake, providing theoretical support for the better protection of this kind of lakes.

Determination and environmental risk assessment of organophosphorus flame retardants in sediments of the South China Sea

As ubiquitous contaminants in the environment, organophosphorus flame retardants (OPFRs) would eventually settle in marine sediment. In this study, concentrations, spatial distributions, and ecological risks of seven OPFRs in sediment samples of the South China Sea (SCS) were investigated for the first time. Total concentration of all OPFRs ranged from 2.5 to 32.3 ng/g dry weight (dw), in which the abundance of tri-cresyl phosphates (TCPs) was the highest. OPFRs in the SCS were at a medium level compared with those from other parts of the world. The nearshore ocean current, ship transportation, and riverine inputs might influence the spatial distributions of OPFRs. The total inventory of six OPFRs in sediment was estimated to be 202.8 tons (16.7×10⁴ km²). The hazard quotient (HQ) of OPFRs ranged from 0 to 3.2E-02, indicating the ignorable ecological risk of OPFRs in sediments of the SCS. This study provides insight into the occurrence of current-use OPFRs in the SCS which deserved long-term concern in the future due to their continuous terrigenous inputs.

Perfluoroalkyl acids in dust on residential indoor/outdoor window glass in Chinese cities: occurrence, composition, and toddler exposure

The dust on indoor and outdoor surfaces of the window glasses were collected using sterile cotton balls in 11 cities from China. Two sampling campaigns were conducted with the time interval of 7 days to investigate the accumulation especially during the Spring festival holidays. Twenty-nine perfluoroalkyl acids (PFAA) were quantified to investigate concentration, composition, and toddlers' exposure. The concentrations of ∑PFAA ranged from no detection (nd) to 43 ng/m2 (mean 8.9 ± 10 ng/m2). Perfluorobutanoic acid (PFBA) was detected in 78% samples and accounted for 55 ± 21% of ∑PFAA concentrations. 6:2 fluorotelomer sulfonic acid (6:2 FTSA) and hexafluoropropylene oxide dimer acid (HFPO-DA) were detected in more than 50% samples indicating the use of alternatives. Fluorotelomer carboxylic acid (FTCA) and fluorotelomer unsaturated acid (FTUCA) were found in the dust, implying the degradation of fluorotelomer alcohols (FTOH). The highest concentration of ∑PFAA (43 ng/m2) was found in outdoor dust from Xinzhou, Shanxi Province. Higher ∑PFAA concentrations were found in indoor dust than outdoor in 6 paired samples (3 from Feb. 14 and 3 from Feb. 21). In Tianjin and Handan, the concentrations of ∑PFAA from outdoor surfaces were higher in sampling campaign I (SC I, Feb. 21) than in sampling campaign II (SC II, Feb. 14), implying intensive outdoor release. The exposure of 2-year-old toddlers to PFAA via hand-to-mouth ingestion and dermal absorption was estimated; the mean values of intake were 2.1 and 1.5 pg/kg body weight, respectively, assuming an exposure time of 1 h.

Pollutants in Plastics within the North Pacific Subtropical Gyre

Here we report concentrations of pollutants in floating plastics from the North Pacific accumulation zone (NPAC). We compared chemical concentrations in plastics of different types and sizes, assessed ocean plastic potential risks using sediment quality criteria, and discussed the implications of our findings for bioaccumulation. Our results suggest that at least a fraction of the NPAC plastics is not in equilibrium with the surrounding seawater. For instance, "hard plastic" samples had significantly higher PBDE concentrations than "nets and ropes" samples, and 29% of them had PBDE composition similar to a widely used flame-retardant mixture. Our findings indicate that NPAC plastics may pose a chemical risk to organisms as 84% of the samples had at least one chemical exceeding sediment threshold effect levels. Furthermore, our surface trawls collected more plastic than biomass (180 times on average), indicating that some NPAC organisms feeding upon floating particles may have plastic as a major component of their diets. If gradients for pollutant transfer from NPAC plastic to predators exist (as indicated by our fugacity ratio calculations), plastics may play a role in transferring chemicals to certain marine organisms.

Molecular perspectives and recent advances in microbial remediation of persistent organic pollutants

Nutrition and pollution stress stimulate genetic adaptation in microorganisms and assist in evolution of diverse metabolic pathways for their survival on several complex organic compounds. Persistent organic pollutants (POPs) are highly lipophilic in nature and cause adverse effects to the environment and human health by biomagnification through the food chain. Diverse microorganisms, harboring numerous plasmids and catabolic genes, acclimatize to these environmentally unfavorable conditions by gene duplication, mutational drift, hypermutation, and recombination. Genetic aspects of some major POP catabolic genes such as biphenyl dioxygenase (bph), DDT 2,3-dioxygenase, and angular dioxygenase assist in degradation of biphenyl, organochlorine pesticides, and dioxins/furans, respectively. Microbial metagenome constitutes the largest genetic reservoir with miscellaneous enzymatic activities implicated in degradation. To tap the metabolic potential of microorganisms, recent techniques like sequence and function-based screening and substrate-induced gene expression are proficient in tracing out novel catabolic genes from the entire metagenome for utilization in enhanced biodegradation. The major endeavor of today's scientific world is to characterize the exact genetic mechanisms of microbes for bioremediation of these toxic compounds by excavating into the uncultured plethora. This review entails the effect of POPs on the environment and involvement of microbial catabolic genes for their removal with the advanced techniques of bioremediation.