Organophosphate Triesters and Their Transformation Products in Sediments of Mangrove Wetlands in the Beibu Gulf, South China Sea

Distribution and adsorption-desorption of organophosphate esters from land to sea in the sediments of the Beibu Gulf, South China Sea: Impact of seagoing river input

Higher ecological risks and lower bioremediation potentials identified for emerging OPEs than legacy PCBs in the Beibu Gulf, China

Simultaneous determination of eight neonicotinoid insecticides, fipronil and its three transformation products in sediments by continuous solvent extraction coupled with liquid chromatography-tandem mass spectrometry.

Long-lived radionuclides in marine sediments from the Beibu Gulf, South China Sea: Spatial distribution, controlling factors, and proxy for transport pathway

Biomonitoring of organophosphate triesters and diesters in human blood in Jiangsu Province, eastern China: Occurrences, associations, and suspect screening of novel metabolites

Despite the growing ubiquity of organophosphate (OP) triesters as environmental contaminants, parameters affecting their aquatic chemical stabilities are currently unknown. The present study examined the pH-dependent (7, 9, 11, or 13) hydrolysis of 16 OP triesters in mixtures of 80 ng/mL for each OP triester over a period of 35 days at 20 °C. For the pH = 7, 9, and 11 solutions, 10 of the 16 OP triesters were stable and with no significant (p > 0.05) degradation. For the remaining 6 OP triesters, significant degradation occurred progressing from the pH = 7 to 11 solutions. At pH = 13, except for tributyl phosphate and tris(2-ethylhexyl) phosphate, 14 OP triesters were degraded with half-lives ranging from 0.0053 days (triphenyl phosphate) to 47 days (tripropyl phosphate). With increasingly basic pH the order of OP triester stability was group A (with alkyl moieties) > group B (chlorinated alkyl) > group C (aryl). Numerous OP diesters were identified depending on the pH level of the solution, whereas OP monoesters were not detectable. This is consistent with no significant (p > 0.05) depletion observed for 5 OP diesters in the same 4 solutions and over same 35 day period, suggesting OP diesters are end products of base-catalyzed hydrolysis of OP triesters. Our results demonstrated that pH-dependent hydrolysis of OP triesters does occur, and such instability would likely affect the fate of OP triesters in aqueous environments where the pH can be variable and basic.

Development and validation of a liquid chromatography-tandem mass spectrometry method for comprehensive detection of organophosphate esters and their degradation products in sediment

Mangrove sediment microorganisms play a vital role in the energy transformation and element cycling in marine wetland ecosystems. Using metagenomics analysis strategy, we compared the taxonomic structure and gene profile of the mangrove and non-mangrove sediment samples at the subtropical estuary in Beibu Gulf, South China Sea. Proteobacteria, Bacteroidetes, and Firmicutes were the most abundant bacterial phyla. Archaeal family Methanosarcinaceae and bacterial genera Vibrio and Dehalococcoides were significantly higher in the mangrove sediments than in the nonmangrove sediments. Functional analysis showed that "Carbohydrate metabolism" was the most abundant metabolic category. The feature of carbohydrate-active enzymes (CZs) was analyzed using the Carbohydrate-Active EnZymes Database. The significant differences of CZs between mangrove and non-mangrove sediments, were attributed to the amounts of polyphenol oxidase (EC 1.10.3.-), hexosyltransferase (EC 2.4.1.-), and β-N-acetylhexosaminidase (EC 3.2.1.52), which were higher in the mangrove sediment samples. Principal component analysis indicated that the microbial community and gene profile between mangrove and non-mangrove sediments were distinct. Redundancy analysis showed that total organic carbon is a significant factor that affects the microbial community and gene distribution. The results indicated that the mangrove ecosystem with massive amounts of organic carbon may promote the richness of carbohydrate metabolism genes and enhance the degradation and utilization of carbohydrates in the mangrove sediments.

Understanding the environmental fate and risks of organophosphate esters: Challenges in linking precursors, parent compounds, and derivatives.

Xia, Z.; Waniek, J.J., and Leipe, T., 2013. Anthropogenic fingerprint in Beibu Gulf (South China Sea) sediments. In: Harff, J., Leipe, T., Waniek, J.J., and Zhou, D. (eds.), Depositional Environments and Multiple Forcing Factors at the South China Sea's Northern Shelf, Journal of Coastal Research, Special Issue, No. 66, pp. 72–90. Coconut Creek (Florida), ISSN 0749-0208.Surface sediments and five cores were chosen to determine grain size, geochemical elements, heavy metals concentrations and age using 14C dating to study sedimentary environment and anthropogenic impact in the Beibu Gulf (South China Sea). The grain size analysis shows differences in the depositional environment amongst the subareas of the gulf. In the north of the gulf, the depositional environment is strong and unstable with complicated hydrodynamics because of the combined influence of rivers, tide, littoral current and the monsoon. In the central part, the depositional environment is weaker and stable, whereas in the south of the gulf (at the entrance), the deposition is higher and influenced mainly by tide. The deposition rate is around 0.3 mm/yr based on 14C dating. The geochemical element analysis indicates different sediment sources in different subareas of the gulf and possible influence of a biogenic source. The terrigenous elements (Al, Fe, Li, Ti, K and Zr) have high positive correlation coefficients, and originate from the northern coast and Hainan Island. The trace elements are mostly enriched within the fine sediments. The enrichment factors (EF) and cultural enrichment factors (CEF) based on aluminum and titanium show that total organic carbon (TOC), As and Hg have high concentrations in the surficial sediments in the north (9.92 mg/kg and 34 μg/kg) and the south (15.5 mg/kg and 22 μg/kg) of the gulf, and are enriched below the surface. Despite the regional differences in heavy metal concentrations in surface sediments, no anthropogenic impact was observed in the center of the gulf according to the results of EF and CEF using the core data. Measured concentrations of the anthropogenic elements were below the evaluation criterion values of the National Standards of GB18668-2002, P. R. China indicating low anthropogenic impact in the entire gulf.

With the prohibition of conventional organochlorine pesticides (OCPs), the extensive use and continuous release of current-use pesticides (CUPs), such as organic amine pesticides (OAPs) and organophosphate pesticides (OPPs), in agriculture and mariculture activities have raised global attention. In this study, the occurrence and distribution of 36 pesticides from above 3 categories were investigated in seawater and sediment in Beibu Gulf, a typical subtropical agricultural and maricultrual zone. Results showed that pesticides were widely present in this region with the total concentration ranging from 0.36 to 21.07 ng/L in seawater and from 0.02 to 9.73 ng/g dw in sediment. OAPs and OPPs were the most abundant categories contributing 74% and 66% to the total pesticides burden in seawater and sediment, respectively, revealing the current-use pesticides as substitutes of legacy organochlorine pesticides (OCPs) were mainly used in surrounding areas. For both seawater and surface sediment, the spatial distribution of pesticides concentrations showed generally seaward decreasing trends, suggesting that anthropogenic activities at coastal areas have an important impact on pesticides pollution. Source identification indicated OCPs in some seawater samples might be from mixture of antifouling paint and dicofol usage, while history residues are main sources of OCPs in sediment. OAPs, especially for cyflufenamid and kresoxim-methyl, mainly come from agricultral and maricultural sewage input, and OPPs were speculated from currency transportation from surrounding areas. Ecological risk assessment showed that OPPs posed moderate to even high risks in most seawater sites. It appears that crustaceans are the most sensitive trophic species to OPPs among aquatic organisms, followed by fish. According to the results of health risks proposed by the major aquatic products in Beibu Gulf (fish and shrimp), the selected pesticides pose no health risk to humans. Nevertheless, OCPs made the highest contribution to the total HQ values. Comprehensively considering the evaluation results of both ecological and health risks, more attention should be given on OPPs and OCPs pollution in the Beibu Gulf.

Occurrence, distribution, source identification, and risk assessment of organophosphate esters in the coastal waters of Beibu Gulf, South China Sea: Impacts of riverine discharge and fishery

Organophosphate esters and their transformation products in megacity atmospheres: Size-dependent gas-particle partitioning and transformation potential.

The opening of the Qiongzhou Strait during the Holocene was a significant geological event in the Beibu Gulf, profoundly influencing sediment provenance and ocean circulation systems. Due to the scarcity of geological records documenting this event, the understanding of regional Holocene sedimentary evolution has been constrained. To investigate the impact of this event on sediment provenance and ocean currents in the Beibu Gulf, geochemical analyses were conducted on sediment core SO-31 retrieved from the South China Sea. The sediments in core SO-31 were stratigraphically divided into three units based on vertical geochemical profiles, reflecting changes in sea level and shifts in sediment provenance within the study area. The Th/Cr vs. Th/Sc scatter plot for core SO-31 indicate that sedimentary materials primarily originated from the Red River during 11,400–7700 a BP, and a significant change in provenance occurred in the study region around 7700 a BP, characterized by increased contributions from the Qiongzhou Strait and decreased contributions from the Red River. This suggests that the opening of the Qiongzhou Strait significantly influenced the sediment supply to the central Beibu Gulf around 7700 a BP. These findings provide critical geochemical evidence for studying the Qiongzhou Strait opening event and enhance our understanding of Holocene sedimentary evolution and “source–sink” transitions in the Beibu Gulf.

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.