Occurrence, distribution and seasonal variation of chlorinated paraffins in coral communities from South China Sea

Metabolic disturbance of short- and medium-chain chlorinated paraffins to zebrafish larva

Chlorinated paraffins (CPs) are widely produced chemicals. Short-chain CPs (SCCPs) and medium-chain CPs (MCCPs) were listed as Persistent Organic Pollutants (POPs) and candidate POPs under the Stockholm Convention, respectively. The present study explored the developmental toxicity and metabolic disruption caused by SCCPs and MCCPs in zebrafish (Danio rerio) larvae. CPs exposure at environmentally relevant levels caused no obvious phenotypic changes with zebrafish larvae except that the body length shortening was observed after exposure to CPs at 1-200 μg/L for 7 day post fertilization. A further metabolomic approach was conducted to explore the early biological responses of developmental toxicity induced by CPs at low dose (1, 5, and 10 μg/L). The results of metabolic disorder, pathway analysis and chronic values indicated that, compared with SCCPs, MCCPs exhibited more risks to zebrafish larvae at low doses. Lipid metabolism was markedly affected in SCCPs exposure group, whereas MCCPs primarily disturbed lipid metabolism, amino acid, and nucleotide metabolisms. Compare with SCCPs, the relatively higher lipid solubility, protein affinity and metabolic rate of MCCPs can probably explain why MCCP-mediated metabolic disruption was significantly higher than that of SCCP. Notably, SCCPs and MCCPs have the same potential to cause cancer, but no evidence indicates the mutagenicity. In summary, our study provides insight into the potential adverse outcome for SCCP and MCCP at low doses.

Occurrence, distribution and annual emissions of chlorinated paraffins in hazardous byproducts from municipal solid waste incineration plants in South China

Nowadays incineration technology has become the most mainstream way for the disposal of municipal wastes. Short chain chlorinated paraffins (SCCPs) and medium chain chlorinated paraffins (MCCPs) are currently classified as new persistent organic pollutants (POPs) and candidate POPs under the Stockholm Convention, respectively. However, the occurrence and contamination characteristics of these main hazardous byproducts (e.g., leachate, fly ash, and bottom ash) from municipal solid waste incineration (MSWI) plants have remained unknown. This study focused on the SCCPs and MCCPs (defined as CPs) contamination and their annual emissions from leachate, fly ash, and bottom ash among three typical MSWI plants in Shenzhen, South China. Compared to the dissolved phase of the leachate, higher concentrations of CPs were detected in the adsorbed phase. The total concentrations of CPs ranged from lower method detection limits (1 in leachate (i.e., adsorbed phase) and bottom ash, while the opposite results were found in fly ash. The dominant SCCP congener groups were C10Cl6-7 in leachate and fly ash, and C13Cl6-7 in bottom ash. The dominant MCCP congener groups were C14Cl7-8 in leachate, fly ash and bottom ash samples. Principal component analysis (PCA) revealed the dominant CPs in fly ash were obviously different from those in leachate and bottom ash. Estimated total annual emissions of CPs from the three main hazardous byproducts generated from typical MSWI plants were estimated between 66.2 and 7510 kg/y and bottom ash contributed the most to the CP emissions. Overall, this study is the first report on CP contamination in hazardous byproducts from MSWI plants, and can provide basic data support for CP contamination control.

Chlorinated Paraffin Pollution in the Marine Environment

Chlorinated paraffins (CPs) are ubiquitous in the environment due to their large-scale usage, persistence, and long-range atmospheric transport. The oceans are a critical environment where CPs transformation occurs. However, the broad impacts of CPs on the marine environment remain unclear. This review describes the sources, occurrence and transport pathways, environmental processes, and ecological effects of CPs in the marine environment. CPs are distributed in the global marine environment by riverine input, ocean currents, and long-range atmospheric transport from industrial areas. Environmental processes, such as the deposition of particle-bound compounds, leaching of plastics, and microbial degradation of CPs, are the critical drivers for regulating CPs' fate in water columns or sediment. Bioaccumulation and trophic transfer of CPs in marine food webs may threaten marine ecosystem functions. To elucidate the biogeochemical processes and environmental impacts of CPs in marine environments, future work should clarify the burden and transformation process of CPs and reveal their ecological effects. The results would help readers clarify the current research status and future research directions of CPs in the marine environment and provide the scientific basis and theoretical foundations for the government to assess marine ecological risks of CPs and to make policies for pollution prevention and control.

Bioaccumulation and Biotransformation of Chlorinated Paraffins

Chlorinated paraffins (CPs), a class of persistent, toxic, and bioaccumulated compounds, have received increasing attention for their environmental occurrence and ecological and human health risks worldwide in the past decades. Understanding the environmental behavior and fate of CPs faces a huge challenge owing to the extremely complex CP congeners. Consequently, the aims of the present study are to summarize and integrate the bioaccumulation and biotransformation of CPs, including the occurrence of CPs in biota, tissue distribution, biomagnification, and trophic transfer, and biotransformation of CPs in plants, invertebrates, and vertebrates in detail. Biota samples collected in China showed higher CP concentrations than other regions, which is consistent with their huge production and usage. The lipid content is the major factor that determines the physical burden of CPs in tissues or organs. Regarding the bioaccumulation of CPs and their influence factors, inconsistent results were obtained. Biotransformation is an important reason for this variable. Some CP congeners are readily biodegradable in plants, animals, and microorganisms. Hydroxylation, dechlorination, chlorine rearrangement, and carbon chain decomposition are potential biotransformation pathways for the CP congeners. Knowledge of the influence of chain length, chlorination degree, constitution, and stereochemistry on the tissue distribution, bioaccumulation, and biotransformation is still scarce.

Bioaccumulation and trophic transfer of PAHs in tropical marine food webs from coral reef ecosystems, the South China Sea: Compositional pattern, driving factors, ecological aspects, and risk assessment

Multiple environmental pressures caused by global warming and human activities have aroused widespread concern about PAHs pollution in tropical marine coral reef regions (CRRs). However, the trophodynamics of PAHs in the food webs of the CRRs and the related influence factors have not been reported. This study investigated the occurrence, trophic amplification, and transmission of PAHs in various organisms selecting between at least representative species for each level in CRRs of the South China Sea (SCS); revealed their driving mechanisms; and explored the trophodynamics of PAHs in the food web of the coral reef ecosystem. Results showed that more PAHs can be accumulated in the mantle tissue of Tridacnidae, and the proportion of mantle tissue of Tridacnidae increases with the increase of latitude (y = 0.01x + 0.17, R² = 0.49, p < 0.05). Latitude drives the differential occurrence level and bioaccumulation of PAHs in tropical marine organisms, and also affects the trophodynamics of PAHs in aquatic ecosystem food webs. PAHs undergo trophic amplification in the food webs of tropical marine ecosystems represented by coral reefs, thus further aggravating the negative environmental impact on coral reef ecosystems. The cancer risk caused by accidental ingestion of PAHs by humans through consumption of seafood in CRRs is very low, but we should be alert to the biomagnification effect of PAHs.

First report on per- and polyfluoroalkyl substances (PFASs) in coral communities from the Northern South China sea: Occurrence, seasonal variation, and interspecies differences

In this study, the contamination levels and seasonal variation of 22 PFASs were investigated in coastal reef-building corals (n = 68) from the northern South China Sea (SCS) during wet and dry seasons. Perfluorohexane sulfonate (PFHxS) was the predominant PFASs in all coral samples, representing 43% of the total PFAS. Long-chain PFASs, as well as PFAS alternatives, were frequently detected above the MQL (>88%) but showed relatively low concentrations compared to short-chain PFASs in most species and seasons. Seasonal variation of PFAS concentrations were observed in branching corals, indicating that the accumulation of PFASs may be associated with coral morphological structures. Interspecies differences in PFAS levels agree well with different bioaccumulation potentials among coral species. Redundancy analysis (RDA) showed that seasonal factor and coral genus could partly influence PFAS concentrations in coral tissues. In summary, our study firstly reported the occurrence of PFASs in coral communities from the SCS and highlights the necessity for future investigations on more toxicity data for coral communities.

Dietary exposure and risk assessment of chlorinated paraffins in roots and rhizomes of traditional Chinese medicine herbs

Traditional Chinese medicine (TCM) provides therapeutic and health care effects through dietary intake. Owing to the susceptibility of plants to contaminations, a risk assessment system is urgently needed to ensure the safe use of TCMs. In this study, the contamination levels and risks associated with the dietary intake of short-chain chlorinated paraffins (SCCPs) and medium-chain chlorinated paraffins (MCCPs) were investigated in six kinds of frequently-used TCM herbs. The concentrations varied from 144.4 to 1527.8 ng·g^-1 dw for SCCPs and non-detect to 1214.1 ng·g^-1 dw for MCCPs, with mean values of 551.5 and 259.8 ng·g^-1 dw, respectively. A geographic distribution analysis indicated that the concentrations of CPs in TCMs were mainly associated with their levels of contamination in the ambient environment. Carbon atom-chlorine congener profiles of CPs were dominated by C₁₀Cl_7-8 and C₁₄Cl_7-8 congeners, accounting for 20.1% and 32.4% of the total SCCP and MCCP concentrations, respectively. Principal component analysis indicated that the TCM species might be the main factor influencing the accumulation of SCCPs congeners. Finally, a risk assessment reveals that the estimated daily intake and margin of exposure were far below levels that might pose a health risk, indicating an acceptable dietary intake of SCCPs and MCCPs in the studied TCMs. This is the first report of CPs in the TCM herbs and the obtained results are expected to aid in future evaluation of the quality of TCMs and ensuring diet and drug safety.

Characterization of chlorinated paraffin-degrading bacteria from marine estuarine sediments

This study explored chlorinated paraffin (CP)-degrading bacteria from the marine environment. Aequorivita, Denitromonas, Parvibaculum, Pseudomonas and Ignavibacterium were selected as the dominant genera after enrichment with chlorinated paraffin 52 (CP52) as the sole carbon source. Eight strains were identified as CP degraders, including Pseudomonas sp. NG6 and NF2, Erythrobacter sp. NG3, Castellaniella sp. NF6, Kordiimonas sp. NE3, Zunongwangia sp. NF12, Zunongwangia sp. NH1 and Chryseoglobus sp. NF13, and their degradation efficiencies ranged from 6.4% to 19.0%. In addition to Pseudomonas, the other six genera of bacteria were first reported to have the degradation ability of CPs. Bacterial categories, carbon-chain lengths and chlorination degrees were three crucial factors affecting the degradation efficiencies of CPs, with their influential ability of chlorinated degrees > bacterial categories > carbon-chain lengths. CP degradation can be performed by producing chlorinated alcohols, chlorinated olefins, dechlorinated alcohols and lower chlorinated CPs. This study will provide valuable information on CP biotransformation and targeted bacterial resources for studying the transformation processes of specific CPs in marine environments.

Spatial distribution, homologue patterns and ecological risks of chlorinated paraffins in mangrove sediments along the South China Coast

The spatial distribution, homologue patterns, and ecological risks of chlorinated paraffins (CPs) were investigated in sediments from sixteen mangrove wetlands along the South China Coast (SCS). The total concentrations of CPs in mangrove sediments from Guangdong, Fujian, Guangxi, and Hainan were in the range of 933-4760, 619-2300, 375-1550, and 271-658 ng/g dry weight, respectively. The contamination levels and spatial distribution of short-chain and medium-chain CPs (SCCPs and MCCPs, respectively) in mangrove sediments were mainly affected by local population scale and CP industries. The dominant CP patterns in sediments were C₁₀-₁₁Cl_6-8 and C₁₄Cl_7-9 for SCCPs and MCCPs, respectively. Redundancy analysis, based on CP levels and several potential influencing factors showed that MCCPs/SCCPs ratio was the main factor affecting the accumulation of CPs in mangrove sediments. Additionally, MCCP concentrations were significantly correlated with total organic carbon (TOC), indicating that TOC might affect MCCP accumulation in mangrove sediments. Risk assessments indicated that CPs would pose medium ecological risks to sediment dwelling organisms in nearly one-third of the sampling sites. This is the first comprehensive report of the sedimentary SCCPs and MCCPs in mangrove wetlands along the SCS and highlights the need for more sediment toxicity data for CPs.

Hair and nails as noninvasive bioindicators of human exposure to chlorinated paraffins: Contamination patterns and potential influencing factors

Most of the studies on short- and medium-chain chlorinated paraffins (SCCPs and MCCPs) in human tissues have focused on human milk and blood. However, little is known about the occurrence of CPs in human hair and nails. In this study, SCCPs and MCCPs were analyzed in 62 pairs of human hair and nails from North China. Median concentrations (range) of SCCPs and MCCPs in human hair were 239 (19.2-877) and 325 (16.9-893) ng/g dw, respectively, all of which were significantly higher than 154 (57.7-355) and 233 (61.0-476) ng/g dw, respectively, in nail samples (p < 0.05). The homologue profiles of CPs in human hair were similar to those in nails, where SCCPs and MCCPs were dominated by C₁₀Cl_6-7 and C₁₄Cl_7-8, respectively. A significant positive relationship was observed between CP levels and age of people for hair, whereas negative linear correlations were observed for nails. The redundancy analysis indicated that age of people might be the main influencing factor on the accumulation of CPs in hair and nails. The present study performed comprehensive evaluation of CP exposure levels in human hair and nail and highlights the need for more data on relationship between internal and external exposure to CPs.

Transcriptome Profiling Reveals a Divergent Adaptive Response to Hyper- and Hypo-Salinity in the Yellow Drum, Nibea albiflora

Simple Summary

Global warming and certain climate disasters (typhoon, tsunami, etc.) can lead to fluctuation in seawater salinity that causes salinity stress in fish. The aim of this study was to investigate the functional genes and relevant pathways in response to salinity stress in the yellow drum. Genes and pathways related to signal transduction, osmoregulation, and metabolism may be involved in the adaptive regulation to salinity in the yellow drum. Additionally, the genes under salinity stress were mainly divided into three expression trends. Our results provided novel insights into further study of the salinity adaptability of euryhaline fishes.

Abstract

The yellow drum (Nibea albiflora) is an important marine economic fish that is widely distributed in the coastal waters of the Northwest Pacific. In order to understand the molecular regulatory mechanism of the yellow drum under salinity stress, in the present study, transcriptome analysis was performed under gradients with six salinities (10, 15, 20, 25, 30, and 35 psu). Compared to 25 psu, 907, 1109, 1309, 18, and 243 differentially expressed genes (DEGs) were obtained under 10, 15, 20, 30, and 35 psu salinities, respectively. The differential gene expression was further validated by quantitative real-time PCR (qPCR). The results of the tendency analysis showed that all DEGs of the yellow drum under salinity fluctuation were mainly divided into three expression trends. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the PI3K-Akt signaling pathway, Jak-STAT signaling pathway as well as the glutathione metabolism and steroid biosynthesis pathways may be the key pathways for the salinity adaptive regulation mechanism of the yellow drum. G protein-coupled receptors (GPCRs), the solute carrier family (SLC), the transient receptor potential cation channel subfamily V member 6 (TRPV6), isocitrate dehydrogenase (IDH1), and fructose-bisphosphate aldolase C-B (ALDOCB) may be the key genes in the response of the yellow drum to salinity stress. This study explored the transcriptional patterns of the yellow drum under salinity stress and provided fundamental information for the study of salinity adaptability in this species.