Temporal and seasonal variation and ecological risk evaluation of flame retardants in seawater and sediments from Bohai Bay near Tianjin, China during 2014 to 2017

Community-level risk assessments on organophosphate esters in the sediments from the Bohai Sea of China based on multimodal species sensitivity distributions coupled with the equilibrium partitioning method

Organophosphate esters (OPEs), increasingly used as alternatives to brominated flame retardants, are ubiquitous in the global aquatic environment. Despite their potential toxicological impact on ecosystems, community-level risk assessments for OPEs in sediments remain scarce. This study investigated OPE occurrences and composition characteristics in the Bohai Sea's sediments and appraised both individual and joint ecological risks posed by characteristic OPE homologs using ten commonly used species sensitivity distribution (SSD) models, integrating acute-to-chronic conversion and phase equilibrium partitioning. OPEs were detected across all sediment samples, with total concentrations ranging from 0.213 ng/g dry weight (dw) to 91.1 ng/g dw. The predominant congeners included tri-n-butyl phosphate (TnBP), triisobutyl phosphate (TiBP), tri(2-ethylhexyl) phosphate, tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCPP), tris(1, 3-dichloro-2-propyl) phosphate (TDCIPP), and triphenylphosphine oxide. Best-fit SSD models varied among TnBP, TiBP, TCEP, TCPP, and TDCIPP, demonstrating Sigmoid, Burr III, Sigmoid, Burr III, and Burr III, respectively. The same parametric model demonstrated variability in the fitting process for different OPE congeners, which also happened to the fitting results of ten parametric models for the same specific characteristic congener, underscoring the necessity of employing multiple models for precise community-level risk assessments. Hazard concentrations for a 5% cumulative probability were 0.116 mg/L, 2.88 mg/L, 1.30 mg/L, 1.44 mg/L, and 1.85 mg/L for each respective congener. The resulting risk quotients (RQ) and overall hazard index (HI) were selected as criteria to assess the individual and joint ecological risks of OPEs in sediments from the Bohai Sea, respectively. RQ and HI were both below 0.1, indicating a low risk to the local ecosystems. Multi-model SSD analysis could provide refined data for community-level risk evaluation, offering valuable insights for the development of evidence-based environmental standards and pollution control strategies.

Organophosphate ester in surface water of the Pearl River and South China Sea, China: Spatial variations and ecological risks

This study focused on investigating the concentrations, compositional profiles, partitioning behaviors and spatial variations of organophosphate esters (OPEs) in the Pearl River (PR), South China Sea (SCS) region, to evaluate their environmental risks. ∑OPEs concentrations in the surface water of the PR ranged from 117.5 to 854.8 ng/L in the dissolved phase and from 0.5 to 13.3 ng/L in the suspended particulate matter. In the surface seawaters of the northern and western parts of the SCS, ∑OPEs concentrations were 1.3-17.6 ng/L (mean: 6.7 ± 5.2) and 2.3-24.4 ng/L (mean: 7.6 ± 5.5), respectively. The percentage of chlorinated OPEs in surface water samples from the PR to the SCS was 79 ± 15%. Tripentyl phosphate (TPeP) (average: 28.3%) and triphenylphosphate (TPhP) (average: 9.6%) exhibited significant particulate fraction. A significant negative correlation (p < 0.05) between salt concentration and OPE congeners in seawater suggested that river runoff predominantly introduced OPEs into the coastal waters of the SCS. The findings also showed higher levels of OPEs in the PR and estuary than in offshore waters. The OPE loading from the PR into the SCS was estimated to be ∼119 t y-1. The presence of TCEP (RQmax = 2.1), TnBP (RQmax = 0.48) and TPhP (RQmax = 0.3) in PR water samples pose a high risk to aquatic organisms, whereas OPEs (RQ < 0.1) in SCS water samples do not pose a threat to aquatic organisms. This research emphasizes the environmental fate and impact of OPEs on surface waters of the PR and SCS.

Organophosphate esters (OPEs) pollution characteristics, bioaccumulation and human consumption implication in wild marine organisms from the Yellow River Estuary, China

As the substitutes of polybrominated diphenyl ethers, organophosphate esters (OPEs) with high concentrations have accumulated in the estuaries, bays, and harbors. However, limited information is available about the OPEs in the estuary organism categories, especially under the multiple industrial pressure. This study investigated the occurrence, bioaccumulation and human consumption implication in wild marine organisms from the Yellow River Estuary, where located many petroleum and chemical manufacturing industries. This study found that concentrations of Σ13OPEs ranged from 547 ng/L to 1164 ng/L in seawater (median: 802 ng/L), from 384 to 1366 ng/g dw in the sediment (median: 601 ng/g dw), and from 419 to 959 ng/g dw (median: 560 ng/g dw) in the marine organisms. The congener compositions in the organisms were dominated by alkyl-OPEs (80.7 %), followed by halogenated-OPEs (18.8 %) and aryl-OPEs (0.5 %). Based on the principal component analysis, petrochemical pollution, and industrial wastewater discharge were distinguished as the main plausible sources of OPEs to the YRE ecosystem. Most OPEs had potential or strong bioaccumulation capacity on the organisms, with a positive correlation between log BAF (Bioaccumulation Factor) and log Kow of OPEs. The highest estimated daily intake value of OPEs was tri-n-propyl phosphate, exceeding 300 ng/kg·bw/day via consuming fish. The highest hazard quotients from OPEs ranged from 0.001 to 0.1, indicating a low risk to human health by consuming marine organisms in the YRE. As the consumption of OPEs increases year by year, the risks of OPEs still cannot be ignored.

Investigation of alkyl, aryl, and chlorinated OPFRs in sediments from estuarine systems: Seasonal variation, spatial distribution and ecological risks assessment

Estuaries in South Africa are very important for biodiversity conservation and serve as focal points for leisure and tourism activities. The organophosphate flame retardants (OPFRs) levels in these aquatic systems haven't been documented in any studies as of yet. Due to the negative effects of persistent organic pollutants in South African estuaries, we examined the occurrence of eight OPFRs in sediments of two estuaries by studying their spatiotemporal distribution, season variation, and ecological risks. The Sundays Estuary (SDE), a semi-urbanized agricultural surrounding system, recorded an ∑8OPFR concentration in sediments that ranged from 0.71 to 22.5 ng/g dw, whereas Swartkops Estuary, a largely urbanized system, recorded a concentration that ranged from 0.61 to 119 ng/g dw. Alkyl-OPFRs were the prevalent homologue in both estuaries compared to the chlorinated and aryl groups. While TBP, TCPP, and TCrP were the most abundant compounds among the homologue groups. There was no distinct seasonal trend of ∑8OPFR concentration in either estuary, with summer and autumn seasons recording the highest concentrations in SDE and SWE, respectively. Ecological risks in the majority of the study sites for the detected compounds were at low (RQ < 0.1) and medium levels (0.1 ≤ RQ < 1) for certain species of fish, Daphnia magna and algae. However, the cumulative RQs for all the compounds had ∑RQs ≥1 for most sites in both estuaries, indicating that these organisms, if present in both estuaries, may be exposed to potential ecological concerns due to accumulated OPFR chemicals. The scope of future studies should be broadened to include research areas that are not only focus on the bioaccumulation patterns of these compounds but also find sustainable ways to reduce them from these estuarine environments.

Organophosphate esters in edible marine fish: Tissue-specific distribution, species-specific bioaccumulation, and human exposure

Although growing evidences have proved the wide presence of organophosphate esters (OPEs) in marine environments, information on the tissue- and species-specific accumulation characteristics of these emerging pollutants in wild marine fish and the associated human exposure risks are currently lacking. Eleven OPEs were comprehensively investigated for their occurrence and tissue accumulation in 15 marine fish species and their living environment matrices (seawater and sediment) from the Beibu Gulf. The OPE concentrations were statistically higher in the liver (17.6-177 ng/g ww, mean 90.9 ± 52.1 ng/g ww) than those of muscle tissues (2.04-22.9 ng/g ww, mean 10.6 ± 5.6 ng/g ww). Tris (phenyl) phosphate (TPHP) was the most predominant OPE congeners in fish liver, and tris(2-chloropropyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP) were dominant OPEs in the muscle. The results suggested different OPE profiles occurred between the tissues. The median logarithmic bioaccumulation factors (BAFs) of TPHP in the muscle and liver, and TCEP in muscle were higher than the regulatory benchmark value (BCF >3.7), indicating very strong bioaccumulation. Carnivorous benthic fish appear to potentially accumulate TPHP, while pelagic and omnivory fish tend to accumulate TCIPP and TCEP. Except for proteins and phospholipids, no significant relationships were found between OPE levels and other biological properties of the studied fish. The results implied that the species-specific accumulation of OPEs mainly attributed to habitat and feeding habit rather than the difference of biochemical composition among species. Metabolism may have a significant effect on the bioaccumulation of OPEs in marine fish. The dietary risks of OPEs for consumers in different age groups ranged from 2.02 × 10-4 to 3.01 × 10-3, indicating relatively low human exposure risks from fish consumption.

Tracing Organophosphate Ester Pollutants in Hadal Trenches─Distribution, Possible Origins, and Transport Mechanisms

Unraveling the mysterious pathways of pollutants to the deepest oceanic realms holds critical importance for assessing the integrity of remote marine ecosystems. This study tracks the transport of pollutants into the depths of the oceans, a key step in protecting the sanctity of these least explored ecosystems. By analyzing hadal trench samples from the Mariana, Mussau, and New Britain trenches, we found the widespread distribution of organophosphate ester (OPE) flame retardants but a complex transport pattern for the OPE in these regions. In the Mariana Trench seawater column, OPE concentrations range between 17.4 and 102 ng L-1, with peaks at depths of 500 and 4000 m, which may be linked to Equatorial Undercurrent and topographic Rossby waves, respectively. Sediments, particularly in Mariana (422 ng g-1 dw), showed high OPE affinity, likely due to organic matter serving as a transport medium, influenced by "solvent switching", "solvent depletion", and "filtering processes". Amphipods in the three trenches had consistent OPE levels (29.1-215 ng g-1 lipid weight), independent of the sediment pollution patterns. The OPEs in these amphipods appeared more linked to surface-dwelling organisms, suggesting the influence of "solvent depletion". This study highlights the need for an improved understanding of deep-sea pollutant sources and transport, urging the establishment of protective measures for these remote marine habitats.

Organophosphate esters in the urban atmosphere of Thessaloniki city, Greece

The occurrence of organophosphate esters (OPEs) in the atmosphere of the urban area of Thessaloniki city, Greece was studied. OPEs were determined in particulate matter (PM2.5) and precipitation during the period 2020-2021. ∑OPEs in rainwater ranged from 520 to 4719 ng L-11 (mean: 1662 ng L-1) with tris (2-butoxyethyl) phosphate (TBOEP) and tris (1-chloro-2-propyl) phosphate (TClPP) being the most abundant compounds. TBOEP and TClPP as well as triphenylphosphine oxide (TPPO) and tris (chloroethyl) phosphate (TCEP) were the dominant OPEs in PM2.5. Concentrations of ∑OPEs in PM2.5ranged from 2.82 to 13.3 ng m-3 (mean: 5.93 ng m-3). Wet deposition fluxes of OPEs were estimated and air mass back trajectories were used to elucidate possible source profiles. An overall low health risk for local population via inhalation of OPEs was revealed.

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

As emerging pollutants, organophosphate esters (OPEs) have been reported in coastal environments worldwide. Nevertheless, information on the occurrence and ecological risks of OPEs, especially the related transformation products, in mangrove wetlands is scarce. For the first time, the coexistence and distribution of OP triesters and their transformation products in three mangrove wetlands in the Beibu Gulf were investigated using ultrasonication and solid-phase extraction, followed by UHPLC-MS/MS detection. The studied OPEs widely existed in all the sampling sites, with the total concentrations ranging from 6.43 ng/g dry weight (dw) to 39.96 ng/g dw and from 3.33 ng/g dw to 22.50 ng/g dw for the OP triesters and transformation products, respectively. Mangrove wetlands tend to retain more OPEs than the surrounding coastal environment. Pearson correlation analysis revealed that the TOC was not the sole factor in determining the OPEs' distribution, and degradation was not the main source of the transformation products in mangrove sediments in the Beibu Gulf. The ecological risks of selected OPEs for different organisms were also assessed, revealing a medium to high risk posed by OP diesters to organisms. The levels or coexistence of OPEs and their metabolites in mangroves need constant monitoring, and more toxicity data should be further studied to assess the effect on normal aquatic organisms.

Organophosphate flame retardants and their metabolites in the Pearl River Estuary: Occurrence, influencing factors, and ecological risk control strategies based on a mass balance model

Estuaries serve as crucial filters for land-based pollutants to the open sea, but there is a lack of information on the migration and fate of organophosphate flame retardants (OPFRs) within estuaries. This study focused on the Pearl River Estuary (PRE) by examining the co-occurrence of OPFRs and their metabolites and quantifying their transport fluxes using a mass balance model. The seawater concentrations of OPFRs and their metabolites exhibited significant seasonal variations (p < 0.01), while the sediment concentrations of OPFRs reflected the long-term distributional equilibrium in the PRE. The concentration of Σ9OPFRs in seawater showed a relentless dilution from the entrance to the offshore region in the normal and wet seasons, which was significantly in accordance with the gradients of pH, dissolved oxygen (DO), and salinity (p < 0.05). Furthermore, horizontal migration dominated the transport of OPFRs, and the inventory assessment revealed that both the water column and sediment were important reservoirs in the PRE. According to the estimated fluxes from the mass balance model, riverine input emerged as the principal pathway for OPFR entry into the PRE (1.55 × 105, 6.28 × 104, and 9.00 × 104 kg/yr in the normal, dry and wet seasons, respectively), whereas outflow to the open sea predominantly determined the main fates of the OPFRs. The risk quotient (RQ) results showed that EHDPHP (0.835) in water posed medium ecological risk, while other OPFRs and metabolites presented relatively lower risk (RQ < 0.1). The risk control effects were evaluated through scenario simulations of mathematical fitting between controllable source factors and the RQ of risky OPFR. The risk of EHDPHP in the PRE could be effectively reduced by restricting its concentrations in entrance region (<9.31, 8.67, and 12.7 ng/L in the normal, dry and wet seasons, respectively) of the PRE. This research offers foundational insights into environmental management and pollution control strategies for emerging pollutants in estuaries.

Organophosphate esters in seawater and sediments from the low-latitude tropical sea

Little is known about the distribution, transport and fate of organophosphate esters (OPEs) in the low-latitude tropic sea. Fourteen OPEs were measured in seawater and sediments from the Pearl River Estuary (PRE) and South China Sea (SCS). The concentrations of OPEs in seawater and sediments ranged from 7.65-270 ng/L and 9.02-44.9 ng/g dw, respectively. The concentrations of OPEs in surface seawater from the PRE (93.4 ± 16.5 ng/L) were significantly higher than those in SCS (23.6 ± 2.17 ng/L, p < 0.001). OPEs in water from the PRE showed a decreasing trend from upstream to downstream. The salinity of water was an important factor to determine the concentrations of OPEs in the PRE. The annual input of OPEs from the PRE to the SCS was about 304 tons. The concentrations of OPEs in seawater column from the SCS decreased during 5-800 m and showed an increasing pattern from 800 m to 3400 m, indicating that OPEs can transport into deep seawater. TCPP was the most abundant OPEs in water and sediments from the PRE and TCEP was the predominant OPEs in the SCS. This work highlights long-range transport of OPEs by seawater to the deep sea environment.

Tissue distribution and trophic transfer of organophosphate triesters and diesters in three marine mammals of the Liaodong Bay and the Northern Yellow Sea

Tissue (muscle, liver, kidney, lung, and heart) distribution and trophic transfer of organophosphate (OP) triesters and diesters in stranded 10 minke whales, 20 spotted seals and 27 East Asian finless porpoises from the Liaodong Bay and the Northern Yellow Sea were evaluated. The OP triesters and diesters were widely found in the tissues of the three marine mammals and their preys, with mean concentrations ranging from below the limits of detection (LOD) to 4342 μg/kg dry weight (dw) and from below the LOD to 1460 μg/kg dw, respectively. Tissue-specific distribution of the OP triesters or diesters were found in the investigated marine mammals with chemical-specific and species-specific. Log Kow negatively affect the accumulation of OP diesters in the marine mammals (p < 0.05), which related to their accumulation pathway in the tissues. The biological traits of the three marine mammals, body length, gender and age could affect the distribution of several OP triesters or diesters. Yet more concern is that significantly biological magnification was found for bis(2-chloroethyl) phosphate (BCEP) with trophic magnification factor (TMF) of 5.36 and for tris(2-ethylhexyl) phosphate (TEHP)(TMF:2.88) along with the finless porpoise food web. These results considerably contribute to expanding understanding of OP triesters or diesters pollution on the organisms in marine ecosystem.

Interannual variation and machine learning simulation of organophosphate esters in Taihu Lake

Organophosphate esters (OPEs) are widespread in water bodies and have attracted public attention due to their hazards. This study investigated the presence of OPEs in surface water of Taihu Lake from 2012 and 2021-2022. The OPEs concentration was compared ten years ago and ten years later. Water and meteorological parameters were ranked using the random forest (RF) model, and OPEs concentration in lakes was simulated using selected parameters as inputs. The concentration of Σ7OPEs was higher ten years ago compared to ten years later. There was no significant seasonal difference in Σ7OPEs from 2021-2022, while the concentration of Σ7OPEs in 2012 was lower in summer than in other seasons. The spatial distribution of the two interannual Σ7OPEs exhibited a decreasing trend from the northwest region. The results of RF importance ranking and redundancy analysis showed that NH3-N, TN, TP, water temperature and relative humidity were the most influential factors affecting OPEs concentrations. RF models performed better for TnBP, as indicated by training R and test R values are excellent and relatively low errors. Our results demonstrated that machine learning models were useful in facilitating efficient monitoring and assessment of OPEs contamination in lakes.

Determinants of organophosphate esters exposure in pregnant women from East China

Organophosphate esters (OPEs) have been broadly used in various industrial and consumer products, resulting in global distribution and human exposure. Gestational exposure to OPEs may adversely affect the health of both pregnant women and their offspring. To better understand OPE exposure in pregnant women, our study determined eight urinary metabolites of major OPEs in pregnant women (n = 733) recruited at 12-16 weeks of gestation from Shanghai, China, and explored the determinants of OPE exposure among various sociodemographic characteristics, lifestyles, and dietary factors. Urinary metabolites of OPEs, including bis (1,3-dichloro-2-propyl) phosphate (BDCPP), bis (2-chloroethyl) phosphate (BCEP), bis (1-chloro-2-propyl) phosphate (BCIPP), dicresyl phosphate (DCP), diphenyl phosphate (DPP), dibutyl phosphate (DBP), bis (2-ethylhexyl) phosphate (BEHP), and bis (2-butoxyethyl) phosphate (BBOEP), exhibited a detection rate ranging from 69.30% to 99.32%. Multivariate linear regression models indicated that pregnant women who were multiparous, had a higher family income per capita, worked in white-collar jobs, and took nutritional supplements such as milk powder and fish oil tended to have higher urinary OPE metabolite concentrations. Besides, independent of sociodemographic characteristics and lifestyle factors, consumption of more aquatic products, soy products, pork, and puffed food, as well as drinking of purified tap water versus tap water, were associated with increased urinary OPEs metabolite concentrations. Our study demonstrated that OPE exposure was ubiquitous in pregnant women from Shanghai, and provided new insights into the potential factors influencing OPE exposure during pregnancy.

Uncovering the distribution patterns and origins of organophosphate esters (OPEs) in the Yellow River Estuary via high-resolution mass spectrometry

Limited information is available regarding the pollution status of organophosphate esters (OPEs) in the environment of the Yellow River estuary. Here, n = 51 sediment samples were collected from the Yellow River estuary in 2021, and further analyzed by using the integrated target, suspect, and feature fragment-dependent nontarget OPE screening strategy developed in our laboratory. Among the 30 target OPEs, 19 were detectable in at least one of the analyzed samples, with total concentrations (Σ19OPEs) ranging from of 41.4 to 1930 ng/g dry weight (dw). On the basis of an in-house suspect compound database, we further tentatively identified 11 suspect OPEs, and they were semi-quantified. Furthermore, four other interesting findings were observed and described as follows: 1) a statistically significant difference existed in the concentrations of OPEs in sediment samples between the lower reaches of the Yellow River (n = 5 samples), and the Yellow River estuary (n = 46 samples) (unpaired t-test, p < 0.001); 2) tris(2,4-di-tert-butylphenyl)phosphate (TDTBPP) exhibited the greatest concentrations (ranging from 30.7 to 1920 ng/g dw) among all OPEs detected in the sediment samples; 3) samples from the north of the Yellow River estuary had higher OPE concentrations than those from the south; and 4) a suspect screening strategy allowed us to identify a novel OPE structure (tert-butyl)phenyl (ethyne-oxidane) bis(2,4-di-tert-butylphenyl) phosphate (TPBDTP) that exhibited a highly positive correlation relationship with TDTBPP (r = 0.749; p < 0.001). Overall, this study provided evidence that OPEs (especially TDTBPP) were ubiquitous in the sediment environment of the Yellow River estuary; thus, we emphasize that continuous monitoring of OPE pollution should be conducted in this region.

Elucidating the toxicity mechanisms of organophosphate esters by adverse outcome pathway network

With the widespread use of organophosphate esters (OPEs), the accumulation and toxicity effect of OPEs in biota are attracting more and more concern. In order to clarify the mechanism of toxicity of OPEs to organisms, this study reviewed the OPEs toxicity and systematically identified the mechanism of OPEs toxicity under the framework of adverse outcome pathway (AOP). OPEs were divided into three groups (alkyl-OPEs, aryl-OPEs, and halogenated-OPEs) and biota was divided into aquatic organism and mammals. The results showed that tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and triphenyl phosphate (TPHP) mainly caused neurotoxicity, reproductive, and hepatotoxicity in different mechanisms. According to the constructed AOP network, the toxicity mechanism of OPEs on aquatic organisms and mammals is different, which is mainly attributed to the different biological metabolic systems of aquatic organisms and mammals. Interestingly, our results indicate that the toxicity effect of the three kinds of OPEs on aquatic organisms is different, while there was no obvious difference in the mechanism of toxicity of OPEs on mammals. This study provides a theoretical basis for OPEs risk assessment in the future.

Spatial and temporal variability and risk assessment of organophosphate esters in seawater and sediments of the Yangtze River estuary

Organophosphate esters (OPEs) as substitutes for PBDEs have been widely detected in the marine environment, while little is known about the pollution characteristics and variation of OPEs in estuarine environments with complex hydrodynamic conditions and land-based input. Yangtze River Estuary (YRE) is a typical highly urbanized and industrialized estuary, with a complex hydrological environment and geochemical behavior. This study found that the concentrations of OPEs in both seawater and sediments in the YRE were higher in spring than in summer. Alkyl OPEs were the first contributor, with TnBP and TiBP as the main components, where the contribution of alkyl OPEs had exceeded 75 % in both seawater and sediments in spring, and 60 % in summer seawater, and even 80 % in sediments. In spring, OPEs peaked in the central to southern region near the YRE. In summer, OPEs were mainly concentrated in the southern branch waterway and southern nearshore area of the YRE and showed a decreasing trend to the northeast. The OPEs in the sediments were mainly concentrated in the Yangtze River Mud Area (YREMA) and the Zhe-Min Coastal Mud Area (ZMCMA). Based on the fugacity model and principal component analysis, sediments could be released into the aquatic environment as an endogenous source, and exogenous sources were mainly municipal and industrial sewage discharge sources, urban and marine traffic discharge sources, and atmospheric deposition sources. The ecological risk analysis showed that the Σ14OPEs had exhibited a low to moderate ecological risk in the southern branch waterway and the south-central region offshore.

Occurrence, source apportionment, and ecological risk assessment of organophosphate esters in surface sediment from the Ogun and Osun Rivers, Southwest Nigeria

Organophosphate esters (OPEs) are synthetic chemicals widely used as e.g., flame retardants and plasticisers in various consumer products. Due to the toxicity of OPEs in aquatic ecosystems, exposure of fauna and flora to these compounds is of potential concern. In this study, the concentrations, profiles, sources, and ecological risk of eight OPEs were investigated in the sediments from the two major rivers in southwest Nigeria. Concentrations of ∑OPEs in surface sediments were in the range 13.1 - 2110 ng/g dry weight (dw) (median: 378 ng/g dw) in the Ogun River and 24.7-589 ng/g dw (median: 174 ng/g dw) in the Osun River. These concentrations are broadly within the range of those reported in surface sediment in previous studies conducted in other locations around the world. Tris (2-butoxyethyl) phosphate (TBOEP) was the dominant OPE in the sediment samples with a median concentration of 337 and 126 ng/g dw for the Ogun and Osun Rivers respectively, while tri-n-butyl phosphate (TnBP) was not detected in any sample. Excluding TBOEP, the chlorinated organophosphate esters: tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were the dominant OPEs in the Osun River, while the aryl-OPEs: triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tri-m-tolyl phosphate (TMTP) were dominant in the Ogun River. Under a median exposure scenario, moderate ecological risk was predicted from exposure to TCIPP in the Osun River. In contrast, under a high exposure scenario, concentrations of TDCIPP (risk quotient, RQ = 5.33-5.37) constituted a high ecological risk in both rivers, with moderate risks observed for TBOEP (RQ = 0.022-0.18) and TCIPP (RQ = 0.097 - 0.16). Therefore, the risk to aquatic organisms from concomitant exposure to mixtures of OPEs in freshwater ecosystems requires further investigation.

Environmental occurrence and ecotoxicity of aquaculture-derived plastic leachates

Plastic products such as fishing nets and foam buoys have been widely used in aquaculture. To enhance the desirable characteristics of the final equipment, plastic gear for aquaculture is mixed with a wide range of additives. Recent studies have shown that additives could be leached out to the environment with a long-term use of aquaculture plastics, forming aquaculture-derived plastic leachates. It should be emphasized that some leachates such as phthalic acid esters (PAEs) and organophosphate esters (OPEs) are endocrine disruptors, which could increase the exposure risk of aquatic products and subsequently display potential threats to human health via food chain. However, systematic studies on the release, occurrence, bioaccumulation, and toxic effects of aquaculture-derived plastic leachates are missing, overlooking their potential sources and ecotoxicological risks in aquatic environments. We have reviewed and compared the concentrations of major plastic leachates in the water environment and organisms of global aquaculture and non-farmed areas, confirming that aquaculture leachate is an important source of contaminants in the environment. Moreover, the toxic effects of aquaculture-derived plastic additives and the related mechanisms are summarized with fish as a representative, revealing their potential health risk. In addition, we proposed current challenges and future research needs, which provides scientific guidance for the use and management of plastic products in aquaculture industries.

Organophosphate esters in the seawater of the Bohai Sea: Environmental occurrence, sources and ecological risks

Organophosphate esters (OPEs) are widely distributed in surface water systems, but limited information was available on the spatial occurrence and ecological risks of OPEs in the Bohai Sea. In this study, 89 water samples in the Bohai Sea and the five surrounding rivers were investigated for the determination of 15 OPEs. The concentration of ∑₁₅OPEs ranged from 373.20 to 2931.27 ng·L^-1 in the river water and 137.81 to 2641.30 ng·L^-1 in the seawater, with high levels of OPEs in Liaodong Bay. Tris(2-chloroethyl) phosphate (TCEP, 10- 92 %) and triethyl phosphate (TEP, 5- 64 %) were dominant for OPEs. The correlation analysis, principal component analysis and hierarchical cluster analysis suggested the conjunction of municipal wastewater via river input and maritime shipping was the main source of OPEs in the Bohai Sea. The ecological risk assessment indicated that the individual OPEs arise low ecological risks in the Bohai Sea, while medium ecological risks of ∑₁₅OPEs are in minority river samples.

Uptake, accumulation, and translocation of organophosphate esters and brominated flame retardants in water hyacinth (Eichhornia crassipes): A field study

Mechanisms underlying the plant uptake, accumulation, and translocation of organophosphate esters (OPEs) and brominated flame retardants (BFRs) in field environments remain ambiguous. To better understand these processes, we selected a typically polluted river with steady flow and rampant water hyacinth (Eichhornia crassipes) and investigated 25 OPEs and 23 BFRs in 24 sets of matched water-plant samples. Both OPEs and BFRs showed high or ultra-high levels in field water hyacinths, statistically positive water-plant/root concentration correlations, and dominant distributions in the roots. Passive root uptake was the dominant route for OPEs and BFRs to enter the water hyacinth. Both OPEs and BFRs in water hyacinth exhibited acropetal translocation from the root and possible basipetal translocation from the leaf. The accumulation and translocation of OPEs in water hyacinth were significantly affected by their substituents and structures, including the chlorination degree, alkyl chain length, side chain, and methylation degree of aryl-substituted OPEs. The translocation of BFRs in water hyacinth also showed close association with their bromination degree, but their accumulation in roots showed anomaly, indicating possible transformations. Overall, the enrichment and behavior of OPEs and BFRs in water hyacinth seemed to be mainly controlled by physicochemical parameters. OPE/BFR concentrations in total suspended particulate (TSP), TSP-associated organic carbon content, TSP concentration, and plant biomass all showed significant effects on their root accumulation and translocations in water hyacinth. This study provides rare field evidences and novel insights into the basipetal translocation of OPEs and BFRs in plants.

Bioaccumulation and Trophic Transfer of Organophosphate Flame Retardants and Their Metabolites in the Estuarine Food Web of the Pearl River, China

The accumulation and trophodynamics of organophosphate flame retardants (OPFRs) and their metabolites were investigated in the estuarine food web of the Pearl River, China. The mean ∑OPFR concentration among the investigated species increased in the following order: fish [431 ± 346 ng/g lipid weight (lw)] < snail (1310 ± 621 ng/g lw) < shrimp (1581 ± 1134 ng/g lw) < crab (1744 ± 1397 ng/g lw). The di-alkyl phosphates (DAPs) of di-(n-butyl) phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), and diphenyl phosphate (DPHP) were the most abundant metabolites, with concentrations same as or even higher than their corresponding parent compounds. The log bioaccumulation factors for most OPFRs were lower than 3.70, and significant biomagnification was only found for trisphenyl phosphate [TPHP, with the trophic magnification factors (TMFs) > 1]. The TMFs of OPFRs, except for TPHP and tributyl phosphate had a positive correlation with lipophilicity (log K_OW, p ≤ 0.05) and a negative correlation with the biotransformation rate (log K_M, p ≤ 0.05). The mean TMF > 1 was observed for all of the OPFR metabolites based on the bootstrap regression method. The "pseudo-biomagnification" of OPFR metabolites might be attributed to the biotransformation of OPFRs in organisms at high trophic levels.

Insights into the geographical distribution, bioaccumulation characteristics, and ecological risks of organophosphate esters

Organophosphate esters (OPEs), as flame retardants and plasticizers, have been numerously explored regarding the occurrence and ecotoxicology. Given their toxicity, persistency and bio-accumulative potential, however, they may pose negative effects on ecosystems, regarding which is a growing global concern. Accordingly, the present review systematically analyses the recent literature to (1) elucidate their worldwide distribution, bioaccumulation, and biomagnification potential, (2) determine their interim water quality criteria (i.e., effect thresholds), and (3) preliminarily assess the ecological risks for 32 OPEs in aquatic ecosystems. The results showed that the spatiotemporal distribution of OPEs was geographically specific and closely related to human activities (i.e., megacities), especially halogenated-OPEs. We also found that precipitation of airborne particulates could affect the concentrations of OPEs in soil, and there was a positive correlation between the bioaccumulation and hydrophobicity of OPEs. Tris(2-ethylhexyl) phosphate may exhibit high bioaccumulation in aquatic organisms. A substantial difference was found among interim water quality criteria for OPEs, partly attributable to the variation of their available toxicity data. Tris(phenyl) phosphate (TPHP) and tris(1,3-dichloroisopropyl) phosphate with the lowest predicted no-effect concentration showed the strongest toxicity of growth and reproduction. Through the application of the risk quotient and joint probability curve, TPHP and tris(chloroethyl) phosphate tended to pose moderate risks, which should receive more attention for risk management. Future research should focus on knowledge gaps in the mechanism of biomagnification, derivation of water quality criteria, and more precise assessment of ecological risks for OPEs.

Occurrence, bioaccumulation and trophic transfer of organophosphate esters in marine food webs: Evidence from three bays in Bohai Sea, China

Due to the widespread use of organophosphate esters (OPEs), the occurrence and trophic transfer of OPEs have attracted attentions in ecosystems. However, as the final sink for these chemicals, the bioaccumulations and trophodynamics of OPEs in marine ecosystems are still not clear. In this study, seawater, sediment and marine organisms collected from Bohai Bay (BHB), Laizhou Bay (LZB), and Liaodong Bay (LDB) in Bohai Sea (BS), China were analyzed to investigate the occurrence, bioaccumulation and trophic transfer of typical OPEs. Total concentration of OPEs (∑₉ OPEs) in surface water in LZB (255.8 ± 36.44 ng/L) and BHB (209.6 ± 35.61 ng/L) was higher than that in LDB (170.0 ± 63.73 ng/L). Marine organisms in LZB accumulated the highest concentrations of OPEs among the 3 bays (∑₁₀OPEs, 70.56 ± 61.36 ng/g ww). Average bioaccumulation factor (BAF) of OPEs in marine organism in BHB, LZB, and LDB was ranged from -2.48 to 0.16, from -2.96 to 1.78, and from -2.59 to 0.59. We also found that trophic magnification factors (TMF) are generally <1, which suggested trophic dilutions of OPEs in BS, China. Nevertheless, the relatively high OPEs levels in BS still may bring potential risks to ecosystem and human health.

Organophosphate esters (OPEs) in a coral reef food web of the Xisha Islands, South China Sea: Occurrence, trophodynamic, and exposure risk

Despite organophosphate esters (OPEs) are widely prevalent in the environment, however, limited information is available regarding their occurrence, trophodynamics, and exposure risks in coral reef ecosystems. In this study, 11 OPEs were investigated in a tropical marine food web (7 fish species and 9 benthos species) from the Xisha (XS) Islands, South China Sea (SCS). The ∑₁₁OPEs were 1.52 ± 0.33 ng/L, 2227 ± 2062 ng/g lipid weight (lw), 1024 ± 606 ng/g lw, and 1800 ± 1344 ng/g lw in seawater, fish, molluscs, and corals, respectively. Tris (2-chloroisopropyl) phosphate (TCIPPs) were the dominant OPEs in seawater, fish, and molluscs, while tris (2-butoxyethyl) phosphate (TBOEP) predominated in coral tissues. Abiotic and biotic factors jointly affect the OPEs enrichment in marine organisms. Trophic magnification factors (TMFs) (range: 1.31-39.2) indicated the biomagnification potency of OPEs. A dietary exposure risk assessment indicated that OPEs at current levels in coral reef fish posed a low risk to human health but were not negligible. Overall, this study contributes to a further understanding of the environmental behaviors of OPEs in coral reef ecosystems.

Bioaccumulation of organophosphorus flame retardants in marine organisms in Liaodong Bay and their potential ecological risks based on species sensitivity distribution

Although organophosphorus flame retardants (OPFRs) in aquatic environments have received increasing concern, little information is available on their bioaccumulation and trophic transfer in marine food webs. Consequently, the risks of OPFRs to marine ecosystems are unknown. In this study, seven OPFR compounds in marine biological samples collected from Liaodong Bay, Bohai Sea, were analyzed to evaluate their level and biological amplification effect in the marine food web. The total OPFRs of marine organisms in Liaodong Bay ranged from 2.60 to 776 ng/g ww, and lipids were critical factors affecting the concentration of OPFRs in marine species. Tris (2-ethylhexyl) phosphate (TEHP) and tris(1-chloro-2-propyl) phosphate (TCIPP) were the OPFRs most frequently detected in marine species. Still, tris(2-chloroethyl) phosphate (TCEP) was dominant in most marine species (16/24), and the content of chlorinated OPFRs was highest. At the same time, alkyl OPFRs and aryl OPFRs accounted for the same proportion. No correlation between OPFR concentration and the trophic level was observed in marine organisms from Liaodong Bay. It was shown in the results of the species sensitivity distribution that TCIPP in Chinese seawater does not pose a potential ecological risk to marine species. However, much work remains to be done on accumulating information and the ecological risks of OPFRs in different marine food webs.

Distribution, sources, and ecological risk of organophosphate esters in the urbanized Jiaozhou Bay, East China

Organophosphate esters (OPEs), substitutes of polybrominated diphenyl ethers, have been found in a variety of marine environmental matrices, whereas little is known about the feature and sources of seawater OPEs from the environments simultaneously affected by multiple anthropogenic activities. Jiaozhou Bay is one typical bay heavily disturbed by human activities, which was semi-enclosed and surrounded by large amounts of discharged rivers and catchments, various types of ports, and aquaculture farms. This study found that concentrations of Σ₁₃OPEs ranged from 23.90 to 366.40 ng/L (median: 37.76 ng/L) in the seawater and from 90.15 to 1183.14 ng/L (median: 940.61 ng/L) in the inflowing river water. Tris (2-chloroisopropyl) phosphate, triethyl phosphate, and tris (2-chloroethyl) phosphate were the predominant congener, with the percentage of 43.76%, 22.80%, and 14.01%, respectively, in the bay water and 52.47%, 11.31%, and 23.66% in the river water. The overall spatial distribution was characterized by a higher concentration of Σ₁₃OPEs and halogenated-OPEs in the nearshore sites and in the inflowing rivers, which were surrounded by urbanized areas with dense anthropogenic activities, especially along the eastern coast. Effluent discharge and vehicular and marine traffic emissions were distinguished as two main plausible sources of OPEs to Jiaozhou Bay, based on the principal component analysis and Spearman correlations. Ecological risk analysis indicated that Σ₁₃OPEs posed a low risk to aquatic organisms in the bay and low-to-medium risks in the inflowing rivers.

Contaminant occurrence, spatiotemporal variation, and ecological risk of organophosphorus flame retardants (OPFRs) in Hangzhou Bay and east China sea ecosystem

Occurrence, spatiotemporal variation, sources, and ecological risks of 20 organophosphorus flame retardants (OPFRs) in water and sediments from Hangzhou Bay (HZB) and its adjacent East China Sea (ECS) were investigated in this study. The concentrations of OPFRs (∑OPFR) in water ranged from 0.51 ng/L to 885 ng/L, with chlorinated OPFRs having the highest value. For sediments, ∑OPFR ranged from 2.93 ng/g, dry weight (dw) to 37.8 ng/g, dw. The ∑OPFR in the water and sediments of HZB in summer was significantly (p < 0.05) higher than that in autumn. Additionally, the pollution of OPFRs in HZB was higher than that in ECS, and the high-concentration areas appeared in the north and south banks of HZB and near the coast of ECS. Principal component analysis-multiple linear regression showed that the OPFRs in this region were mainly from industrial products (e.g., polyurethane foam/paint/coating/textiles/product processing). In terms of aquatic environments, ecological risks were in a low (∑RQs<0.1) to moderate (0.1<∑RQs<1) level, with regard to median exposure levels, a moderate risk (0.1<∑RQs<1) was found in the sediments during autumn. This study can provide new insights into the OPFR pollution characteristic and ecological risk in a specific eco-environment.

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

As emerging pollutants, the environmental geochemistry of organophosphate esters (OPEs) in the coastal zone with multiple functional areas are still less recognized. This study investigated spatiotemporal distribution, sources and risks of 11 widely used OPEs in surface waters from seagoing rivers and multiple coastal functional areas of the Beibu Gulf. The results indicated that significantly higher ∑₁₁OPEs (total concentrations of 11 OPEs, ng/L) occurred in summer (34.2-1227) than in winter (20.6-840), as a result of the high emission caused by climate reasons. In general, higher ∑₁₁OPEs occurred in rivers (41.2-1227) than in the coast (34.2-809) in summer, especially in the urban rivers, while in winter, higher ∑₁₁OPEs occurred in the coast (23.4-840 vs 20.6-319 in rivers) because of obviously higher ∑₁₁OPEs in marine fishery areas (99-840). Source identification revealed that fishery activity, especially fishing vessels, and urban rivers were the main sources of OPEs in the Beibu Gulf. For the individual OPE, only tri-n-butyl phosphate (TNBP) may have ecological risks to aquatic organisms in a few sites, but if considering the additive effects, the OPEs mixtures would pose a high risk to algae and low to medium threats to crustaceans and fish.

Sources, behaviors, transformations, and environmental risks of organophosphate esters in the coastal environment: A review

The rapid growth in the global production of organophosphate esters (OPEs) has resulted in their high environmental concentrations. The low removal rate of OPEs makes the effluents of wastewater treatment plants be one of the major sources of OPEs. Due to relatively high solubility and mobility, OPEs can be carried to the coastal environment through river discharge and atmospheric deposition. Therefore, the coastal environment can be an important OPE sink. Previous studies have shown that OPEs were widely detected in coastal atmospheres, water, sediments, and even aquatic organisms. OPEs can undergo various environmental processes in the coastal environment, including adsorption/desorption, air-water exchange, and degradation. In addition, bioaccumulation of OPEs was observed in coastal biota but current concentrations would not cause significant ecological risks. More efforts are required to understand the environmental behaviors of OPEs and address resultant environmental and health risks, especially in the complicated environment.

A new and systematic review on the efficiency and mechanism of different techniques for OPFRs removal from aqueous environments

Organic phosphorus flame retardants (OPFRs), as a new type of emerging contaminant, have drawn great attention over the last few years, due to their wide distribution in aquatic environments and potential toxicities to humans and living beings. Various treatment methods have been reported to remove OPFRs from water or wastewater. In this review, the performances and mechanisms for OPFRs removal with different methods including adsorption, oxidation, reduction and biological techniques are overviewed and discussed. Each technique possesses its advantage and limitation, which is compared in the paper. The degradation pathways of typical OPFRs pollutants, such as Cl-OPFRs, alkyl OPFRs and aryl OPFRs, are also reviewed and compared. The degradation of those OPFRs depends heavily upon their structures and properties. Furthermore, the implications and future perspectives in such area are discussed. The review may help identify the research priorities for OPFRs remediation and understand the fate of OPFRs during the treatment processes.

Organophosphate esters and synthetic musks in the sediments of the Yangtze River Estuary and adjacent East China Sea: Occurrence, distribution, and potential ecological risks

Occurrence, distribution, and potential ecological risks of ten organophosphate esters (OPEs) and nine synthetic musks (SMs) were investigated in sediments from the Yangtze River Estuary (YRE) and adjacent East China Sea (ECS). The total concentrations of OPEs in the surface sediments ranged from 0.977 to 19.0 ng/g dry weight (dw) with tris(2-chloro-propyl) phosphate being the dominant component. Total concentrations of SMs ranged from 0.176 to 7.25 ng/g dw, with 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta(g)-2-benzopyran and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-tetrahydronaphthalene as the dominant SMs. Higher sedimentary concentrations of ΣOPEs and ΣSMs were found in the river mouths of the YRE, inter face of Hangzhou Bay, and mud area of the ECS; the results suggested that terrestrial discharge might be the main source of OPEs and SMs in the studied region. Risk assessment revealed that low ecological risks were posed by OPEs, and limited to low ecological risks were posed by SMs.

Occurrence and distribution of organophosphate flame retardants in seawater and sediment from coastal areas of the East China and Yellow Seas

Organophosphates (OPEs) are manmade organic pollutants that are widely used as flame retardants, plasticizers, and antifoaming and hydraulic agents. In this study, seven OPEs in seawater and sediment from the Yellow Sea and East China Sea were determined to study the distribution and diffusion behavior, and to evaluate the environmental risks. The ΣOPEs in the seawater and sediments ranged from below the method detection limit (<MDL) to 497.40 ng/L and from < MDL to 66.50 ng/g dw, respectively. Tri-n-butyl phosphate (TnBP), tris-(1, 3-Dichloro-2-Propyl) phosphate (TDCPP), and tri-meta-cresyl phosphate (TmCP) were the dominant OPEs in the seawater and sediments. OPEs were mainly distributed in coastal areas and the South Yellow Sea, indicating that they are mainly affected by land-based pollution and ocean currents. Fugacity analysis shows that tri-para-cresyl phosphate (TpCP) was in a state of equilibrium, while TDCPP, TnBP, and TmCP other OPEs tended to diffuse from sediment to water. The diffusion behavior of OPEs is mainly affected by their chemical properties. Hazard quotient (HQ) values of TmCP and TpCP in sediment samples were >1.0, indicating high ecological risks to aquatic organisms.

Ecological risk assessment for organophosphate esters in the surface water from the Bohai Sea of China using multimodal species sensitivity distributions

Organophosphate esters (OPEs) as the foremost substitutes of brominated flame retardants have been ubiquitously found in the aquatic environment around the world. However, the information on the community-level risks induced by OPEs to the marine ecosystem remains scarce. This study adopted ten commonly used species sensitivity distribution (SSD) parametric statistical approaches coupled with the acute-to-chronic transformation for the toxicity data to fit the sensitivity distributions of different species to four major OPE congeners including triethyl phosphate (TEP), tri-n-butyl phosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP), and tris(1-chloro-2-propyl) phosphate (TCPP) in the surface water of the Bohai Sea. All SSD models except Exponential for TnBP, TCEP, and TCPP fitted well the chronic toxicity data for the four OPE congeners. Discrepancies appeared among the best fitting models for different congeners, which also happened to the fitting results from the multiple SSD models for each congener. Based on the best fitting models, the hazard concentrations corresponding to the cumulative probability of 5% were 3.58 mg/L, 0.116 mg/L, 1.30 mg/L, and 1.44 mg/L for TEP, TnBP, TCEP, and TCPP, respectively. The risks induced by the four OPE congeners to the Bohai Sea ecosystem were negligible during the monitoring period because of both the risk quotients and the hazard indexes far <0.1. This study drew a clear picture of the joint ecological risks of TEP, TnBP, TCEP, and TCPP to the Bohai Sea environment. The application of multimodal SSD statistical methods will benefit the accurate derivation of water quality criteria and the community-level ecological risk assessment for pollutants.

Terrigenous export and ocean currents' diffusion of organophosphorus flame retardants along China's adjacent seas

High demands for but strict regulatory measures on Organophosphorus Flame Retardants (OPFRs) have resulted in mainland China transitioning from the region that imports OPRFs to one that exports these substances. Simultaneously, large quantities of terrigenous OPFRs have been exported to adjacent seas by the major river systems, particularly the Yangtze River. This study examined the presence of ten OPFRs in China's adjacent seas. High levels of OPFRs were observed in seas south of mainland China, with Tris (2-chloroethyl) phosphate (TCEP) and Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) dominant. The terrigenous OPFRs were redistributed by the ocean surface currents, with OPFRs tending to accumulate in regions with lower current speed. The producers of OPFRs are mainly distributed along the Haihe, Yellow, and Yangtze river systems. The application of OPFRs to electric vehicle charging stations, charging connectors, and 5G infrastructure in the Chinese mainland will likely drive rapid growth in OPFR related industry in the future. The diffusion trend map of OPFR indicated that the Bohai Sea and the central northern Yellow Sea are at high risk of ecological damage in the spring. The offshore region of the north of the South China Sea tended to aggregate more OPFRs in summer. Regions of the OPFR aggregation effect were at a higher risk of ecological damage.

Occurrence, Distribution, and Risk of Organophosphate Flame Retardants in Sediments from Jiulong River Estuary and Adjacent Western Taiwan Strait, China

Organophosphate ester flame retardants (OPFRs) are widely prevalent in the environment and are of significant concern because of their potential toxicity to human health and wildlife. In this study, the concentration, frequency, spatial distribution, potential sources, and ecological risks of OPFRs in sediments from the Jiulong River estuary and the adjacent western Taiwan Strait were investigated. Concentrations of four of the five studied OPFRs were between <LOD and 36.6 ng/g. The distribution of all OPFRs, except 2-Ethylhexyl diphenyl phosphate (EHDPP), remained highly consistent with hydrological (salinity) trends. Furthermore, a significantly positive correlation between EHDPP and total concentrations suggested that it may be the dominant contaminant at both sites. Principal element analysis indicated multiple sources of OPFRs, which were categorized as emissions from road runoff and surface traffic, effects of atmospheric deposition and hydrologic conditions, and a combination of industrial and population effects. Ecological risk indicates that tris (chloroethyl) phosphate (TCEP) and triphosphate ester (2,3-dibromopropyl) (TDBPP) have almost no risk, tris (clorisopropyl) phosphate (TCPP) generally has low risk, while EHDPP has moderate risk with the highest value of 0.487 in the sediments from both sites. Meanwhile, TCPP and TCEP exhibit lower theoretical health risks but are still not negligible. Overall, this work provides data to support global pollutant studies and facilitate the implementation of pollutant control strategies.

Bioaccumulation of organophosphorus flame retardants in the marine mussel Mytilus galloprovincialis

The bioaccumulation and depuration of seven organophosphorus flame retardants (OPFRs) in marine mussel Mytilus galloprovincialis were studied. OPFRs showed to be bioavailable in aquatic environments. When mussels are exposed to environmentally relevant concentrations of OPFRs, uptake kinetics fit well to a first-order model with a single compartment; in contrast depuration rates were generally underestimated by that model, most likely because it does not take into account the biotransformation of OPFRs by the organisms. The highest bioaccumulation rates were observed for tricresyl phosphate (TCrP), triphenyl phosphate (TPhP) and 2-ethylhexyldiphenylphosphate (EHDPP). This could be due to the presence of aryl groups in these compounds, their low solubility in water, and their affinity for fat tissues. According to these findings TCrP, with a BCF value of 4042 L kg^-1 wet weight, should be classified in environmental regulations as an accumulative chemical.

Exploring source footprint of Organophosphate esters in the Bohai Sea, China: Insight from temporal and spatial variabilities in the atmosphere from June 2014 to May 2019

Organophosphate esters (OPEs) are still produced and used in large quantities in the world-wide, and the environmental burden and behavior have generated widespread concern, especially in some large-scale waterbodies. This study conducted a comprehensive assessment on the temporal and spatial variabilities and budget of OPEs to trace the source for the Bohai Sea (BS), based on a 5-year seasonal monitoring campaign (June 2014 to May 2019) of 12 atmospheric sites around the BS and our previous studies. The average concentration of Σ₁₀OPEs in atmosphere during the sampling period was 7.65 ± 6.42 ng m^-3, and chlorinated OPEs were the major compounds. The Seasonal-Trend decomposition procedure based on Loess (STL) analyzed that during the 5-year sampling period, the atmospheric concentrations of Σ₁₀OPEs had a slightly increasing trend with a rate of + 0.092 ng m^-3 yr^-1, and the seasonal concentrations had a distinct seasonal distribution. The highest concentration of Σ₁₀OPEs was observed at the sampling site of Dalian, followed by Tianjin, Yantai, and Beihuangcheng. The estimation of the fugacity ratios and air-water gas exchange fluxes established that the concentration levels of two major components of chlorinated OPEs (tris-(2-chloroethyl) phosphate (TCEP) and tris-(1-chloro-2-propyl) phosphate (TCPP)) in the atmosphere were dominated by their volatilization from BS's seawater (1.24 ± 0.46 t yr^-1 for TCEP and 5.15 ± 2.15 t yr^-1 for TCPP), with 73% deriving from the coastal seawater. The budget assessment suggested that the volatile fluxes of TCEP and TCPP accounted for 8% and 29% of their storages (15.6 ± 5.32 t for TCEP and 17.6 ± 6.70 t for TCPP) in the BS seawater, which were mainly contributed by continental river input (20% for TCEP and 42% for TCPP). The efforts indicated that river inputs of TCEP and TCPP needed to be paid more attention for the improvement of environmental quality of the BS.

Organophosphate esters in inland and coastal waters in northern Greece

The occurrence and distribution of organophosphate esters (OPEs) in inland and coastal waters in Thessaloniki, Greece, were studied during the period 2019-2020. Samples from rivers and streams as well as coastal waters, were analyzed for the presence of 11 OPEs in dissolved and particulate fraction. OPEs were ubiquitous pollutants in the aquatic environment. Concentrations of dissolved fraction of ΣOPEs concentrations ranged from 400 to 2158 ng L^-1 in rivers, 400-1270 in coastal sites and 377-30,560 ng L^-1 in streams. TBOEP showed the highest concentrations followed by TPHP, TNBP and TClPP. Significant particulate fractions were determined for TNBP, TClPP TPHP and TCP. Field partition coefficients in inland waters were dependent on the concentration of total suspended solids. Risk assessment did not show potential threat due to OPEs in rivers and coastal sites, however, potential adverse effects were found in streams.

Occurrence, spatiotemporal distribution, and ecological risks of organophosphate esters in the water of the Yellow River to the Laizhou Bay, Bohai Sea

Limited information is available on the spatiotemporal occurrence and ecological risks of organophosphate esters (OPEs) in coastal environments. 175 water samples were collected in Laizhou Bay (LZB) and its rivers and estuaries during spring and summer for the determination of 12 targeted OPEs. Total concentration of OPEs ranged from 234.4 to 2892.1 ng L^-1 in the river and estuarine water and 87.6 to 969.4 ng L^-1 in the bay water, with medians of 1015.8 and 296.8 ng L^-1, respectively, showing that riverine inputs were the major sources of OPEs in the bay. Tris (2-chloroisopropyl) phosphate (TCIPP) and triethyl phosphate (TEP) were the most abundant OPEs, with median contributions of 47% and 36% in the bay water, respectively. The total concentration of OPEs was higher in the estuarine area of the Yellow River and the southwestern coast of the LZB under the influence of riverine OPE inputs and ocean currents. In addition, the concentrations of dominant OPE species were significantly higher in the surface water than in the bottom water. The concentrations of dominant OPE species were found to be significantly lower in summer than in spring, mainly due to both precipitation and seawater dilution effects. However, the concentrations of three minor OPE species were significantly higher in summer than in spring, probably because of their high usage in summer. TCIPP and TEP concentrations were significantly negatively correlated with salinity. The targeted OPEs posed low ecological risk in the bay and moderate ecological risk in the rivers and estuaries, which was mostly ascribed to the toxicity of tris (2-chloroethyl) phosphate (TCEP) and resorcinol-bis (diphenyl) phosphate (RDP) to algae. Priority should be given to TCIPP, TEP, TCEP, and RDP in the LZB due to their high concentrations and/or toxicity.

Spatial pattern analysis reveals multiple sources of organophosphorus flame retardants in coastal waters

Organophosphorus flame retardants (PFRs) are a group of emerging contaminants which have been detected in worldwide waters. However, source of various PFRs in the large-scale area like coastal water environment have not been clearly revealed. In this study, fifteen PFRs in coast of Guangdong-Hong Kong-Macao Greater Bay area (GBA), China were investigated, and a method of spatial pattern analysis was firstly used for pollution source identification. Seawater samples from different segments of GBA coast were analyzed and thirteen PFRs were quantified with total concentrations ranging from 32.7 to 1032.7 ng L^-1. GBA coasts have been seriously polluted by PFRs. A hierarchical cluster analysis of the PFR concentrations in different GBA sites showed significant spatial distributions for different types of PFRs. A series of correlation analysis between PFRs distributions and spatial pattern of GBA socio-economic indicators were performed, and multiple sources including human settlement, wastewater, manufacture, construction industry, vehicles, and shipping transport were found to be correlated to PFRs pollutions in the coasts. This study indicates that spatial pattern analysis based on statistical analysis would be a promising method of analyzing environmental data and exploring pollution source in large-scale area.

Occurrence, distribution and risk assessment of organophosphate ester flame retardants and plasticizers in surface seawater of the West Pacific

Twenty-eight samples of surface seawater were collected from the West Pacific Ocean during 2019 using a high-volume solid-phase extraction with high-throughput organic analysis (Hi-throat/Hi-volume SPE) method, and concentrations of 10 organophosphate ester flame retardants and plasticizers (OPEs) were determined. The total OPE concentration in the samples was 3.02-48.4 ng L^-1 (mean 25.0 ± 10.5 ng L^-1), with tris(2-chloroethyl) phosphate (TCEP) being the largest contributor. Cluster analysis results showed off-shore input from the coast of East and Southeast Asia was an important source of these chemicals. Tri-p-tolyl phosphate (TpTP) should also be considered for long-term monitoring, because of its high detection frequency. Results of a risk assessment indicated low ecological risk to species in the West Pacific Ocean for TPhP and ΣOPEs. Hazard quotients (HQs) were all <1, indicating that the health risk to humans from these chemicals was at acceptable levels.

A review on the occurrence of organophosphate flame retardants in the aquatic environment in China and implications for risk assessment

Organophosphate flame retardants (OPFRs), used extensively as substitutes for polybrominated diphenyl ethers, are ubiquitous environmental contaminants. OPFR pollution in aquatic environments, the main sink of pollutants, has been studied extensively over the past decade. Here, we review the current knowledge on the consumption and applications of OPFRs, and on their ecotoxicity in aquatic environments worldwide. We also synthesize the available evidence on the occurrence of OPFRs in aquatic environments in China (wastewater treatment plant influent and effluent, surface water, sediment, aquatic biota, and drinking water). Across China, the measured concentrations of OPFRs differ by more than three orders of magnitude. Risk assessments based on these measurements indicate a low level of ecological risk from OPFRs in most aquatic environments in China, and a low risk to human health from drinking water and aquatic products. Finally, we identify gaps in the current knowledge and directions for further research on OPFRs in aquatic environments.

Spatio-temporal variations and input patterns on the legacy and novel brominated flame retardants (BFRs) in coastal rivers of North China

Decabromodiphenyl ether (BDE209) has been subject to restrictions since 2018 in developed countries but is still manufacturing in China. Decabromodiphenyl ethane (DBDPE) is widely used as a replacement for BDE209. To better understand the behaviors and fates of these legacy and novel brominated flame retardants (BFRs), water samples were collected from the estuaries of 36 rivers that drain into the Bohai Sea (BS) and North Yellow Sea (NYS) in 2017 and 2018. The results showed that BDE209 was still the predominant compound with a median concentration of 2470 pg L^-1, whereas DBDPE had a median concentration of 129 pg L^-1. Spatially, relatively high concentrations were observed in the rivers near Laizhou Bay (LB), which is the manufacturing hub of BFRs. BDE209 concentrations were significantly higher in dry season than in wet season, which indicates a dominant process of dilution by precipitation during the wet season. DBDPE concentration showed no significant seasonal difference. This implies that wet deposition was the major additional source of DBDPE during the wet season, and the concentration increased further during the autumn as a result of a time-lag effect. The BFR concentrations in urban rivers were lower than those reported by a study undertaken in August 2013. An increase in the BFR concentrations in rural rivers since 2013 suggested increases in the use and non-point source emissions of BFRs in some remote aquatic environments. The estimated annual inputs of BDE209 and DBDPE into the BS were ∼95.9 kg yr^-1 and ∼26.8 kg yr^-1, respectively, whereas those into the NYS were ∼24.1 kg yr^-1 and ∼8.38 kg yr^-1. The results revealed an ecological risk of BDE209 in winter especially in the Xiaoqing River, thus suggesting the impact of BDE209 on the aquatic environment and human health.

Organophosphorus flame retardants (OPFRs) in the seawater and sediments of the Qinzhou Bay, Northern Beibu Gulf: Occurrence, distribution, and ecological risks

The occurrence, distributions, and ecological risks of 11 organophosphate flame retardants (OPFRs) were investigated in the seawater and sediment samples from the Qinzhou Bay. The Σ₁₁OPFRs in the surface seawater and sediments ranged from 150 to 885 ng/L and from <the limit of quantification (LOQ) to 32.2 ng/g dw, respectively, with high levels of OPFRs in the industrialized and port areas. Tris (2-chloro-propyl) phosphate (TCIPP), tris (2-chloroethyl) phosphate (TCEP), and tri-n-butyl phosphate (TNBP) were the dominant OPFRs in the surface seawater and sediments. The Σ₁₁OPFRs concentrations in the sediment core ranged 1.2-18.6 ng/g dw and the vertical trends showed a recent increase of OPFRs emissions, especially for TNBP and triphenyl phosphate (TPHP). Risk assessment revealed that individual OPFR could pose low to medium ecological risks, but the risk from the mixture of OPFRs on aquatic organisms requires more attention.

Organophosphorus flame retardants in breast milk from Beijing, China: Occurrence, nursing infant's exposure and risk assessment

Organophosphorus flame retardants (OPFRs) are widely used chemicals, whereas data on OPFRs in human being is limited. In this study, thirteen OPFRs were measured in 105 breast milk samples collected from Beijing mothers in 2018. The ∑₁₃OPFRs ranged from <LOD to 106 ng mL^-1 (<LOD-6700 ng g^-1 lipid weight (lw)), with a median value 10.6 ng mL^-1 (157 ng g^-1 lw). The most abundant compound was tris(2-ethylhexyl) phosphate (TEHP), followed by triphenyl phosphate (TPhP) and 2-ethylhexyl diphenyl phosphate (EHDPP). The detecting frequencies and contamination levels of OPFRs in our study were higher than those reported in other studies, which indicated that China is one of the most affected regions by OPFRs. In addition, OPFR levels in our study were found to be higher than levels of brominated flame retardants (BFRs) in human milk from China. Based on regression analyses, mothers' personal characters, including age, pregnancy, residing/working location, and educational level were found to be impact factors of some OPFRs in breast milk. Estimated daily intakes (EDI) of the OPFRs for nursing infants via human milk ingest were calculated, and the mean EDIs of the 13 OPFRs ranged from 2.62 to 1640 ng kg^-1 bw d^-1. Since the mean and max EDIs of most OPFRs were lower than corresponding reference doses (RfDs), the daily OPFR intake for most nursing infants would not cause significant health concerns. However, the max EDIs of two OPFRs, TPhP and EHDPP, with values of 1.09 × 10⁴ and 2190 ng kg^-1 bw d^-1, respectively, were higher than their corresponding RfDs. To our knowledge, this is the first report on the occurrence of OPFRs in human milk from China.

Rapid electrochemical reduction of a typical chlorinated organophosphorus flame retardant on copper foam: degradation kinetics and mechanisms

With the widespread use, chlorinated organophosphorus flame retardants (Cl-OPFRs) as a new emerging contaminant have been widely detected in water environments over the last few years. In this study, the degradation of a typical Cl-OPFR, TCEP (tris (2-chloroethyl) phosphate), by electrochemical reduction was investigated. It was found that copper (Cu) foam as the cathode showed more rapid and effective degradation for TCEP, compared to other cathodes. When TCEP was at the low concentrations (0.1 and 1 mg L^-1), its degradation by Cu foam could reach above 95% within 20 min, and the maximum rate constant was 0.127 min-1. TCEP reduction was little influenced by the co-existing humic substance and anions, except Cl^-. Compared with the reported oxidation methods, electrochemical reduction showed fast and stable degradation for TCEP. For other types of Cl-OPFRs, electrochemical reduction displayed a fast and effective removal for tris (1,3-dichloro-2-propyl) phosphate but lower removal for tris (2-cholroisopropyl) phosphate who possessed methyl units in the branched chains, influencing its reducibility. Based on the product analysis and Fukui function calculation, the bonds of TCEP molecule were found to be gradually broken, and the three oxygen-ethyl-chlorine arms were cleaved one by one. The products including C₆H₁₃Cl₂O₄P (MW = 249.99278 Da), C₄H₉Cl₂O₄P (MW = 221.96105 Da) and C₄H₁₀ClO₄P (MW = 188.0002 Da) were detected at 60 min reaction, and those intermediates showed much lower toxicities than TCEP according to the previous report. The findings may provide a promising treatment for Cl-OPFRs removal from aqueous environments and help understand their reductive fate.

Comprehensive evaluation of organophosphate ester contamination in surface water and sediment of the Bohai Sea, China

This study investigated the occurrence and profile of 14 organophosphate esters (OPEs) in surface water and sediment of the whole Bohai Sea. A total of 53 pairs of surface water and sediment samples were collected and the contained OPEs were quantified using a gas chromatography-mass spectrometry (GC-MS). The average concentrations of OPEs in surface water and sediment were in the range of 0-92.9 ng/L and 0.001-8.58 ng/g dry weight (dw), respectively, with tri (2-chloroethyl) phosphate (TCEP) as the predominant congener in both compartments. The total concentrations of 14 OPEs (∑₁₄OPEs) in surface water and sediment were in the range of 10.9-516.4 ng/L and 1.42-52.9 ng/g dw, respectively. The inventories of ∑₁₄OPEs were calculated to be 179.3 tons in the water and 101.5 tons in the sediment. Based on the risk quotients (RQs), the ecological risks of OPEs to the aquatic organisms in the Bohai Sea were considered to be negligible.

Elucidating multilevel toxicity response differences between tris(1,3-dichloro-2-propyl) phosphate and its primary metabolite in Corbicula fluminea

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and its primary metabolite, bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) are frequently detected in aquatic environments. However, information regarding the biotoxicity of these compounds to bivalves is limited. We explored the multilevel physiological responses of Corbicula fluminea to TDCIPP and BDCIPP. The results indicated that TDCIPP/BDCIPP bioaccumulation in bivalves was positively correlated with their hydrophobicity. Furthermore, the higher body burden of TDCIPP in digestive glands led to significantly higher levels of ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), and P-glycoprotein (p < 0.05). Owing to different molecular structures of inducers, upregulations of cyp4, gstm1, and abcb1 mRNA exhibited different sensitivities to TDCIPP and BDCIPP. Although Phase-I and Phase-II biotransformation and the multixenobiotic resistance (MXR) system were activated to protect bivalves from TDCIPP or BDCIPP, digestive glands produced large amounts of reactive oxygen species (ROS). Moreover, oxidative stress, the percentage of apoptotic cells in digestive glands, and inhibition of siphoning behaviour in TDCIPP treatments were higher than those in BDCIPP treatments (p < 0.05), indicating that TDCIPP was more toxic to bivalves than BDCIPP. Lower bioaccumulation and rapid metabolism of BDCIPP in vivo may contribute to alleviating its toxicity. This research establishes a foundation for further understanding the differences between the toxic mechanisms of TDCIPP and its metabolites.

Legacy and novel flame retardants in water and sediment from highly industrialized bays of Korea: Occurrence, source tracking, decadal time trend, and ecological risks

Legacy and novel flame retardants (FRs) such as polybrominated diphenyl ethers (PBDEs), novel BFRs, and organophosphate flame retardants (OPFRs) were measured in water and sediment collected from highly industrialized bays of Korea. Predominant compounds in sediment were BDE 209, DBDPE, and BTBPE for BFRs, and TCPP and TBOEP for OPFRs, respectively. Higher alternative FR concentrations were observed compared to those reported for previous studies. The highest BFR concentrations were found in locations close to industrial complexes, while the OPFR concentrations were highest in locations close to domestic regions and a wastewater treatment plant. Different contamination sources were observed for BFRs and OPFRs. The ratio of DBDPE/BDE 209 in sediment ranged from 0.84 to 28, indicating a shift in consumption of BFRs. A significant decline in PBDEs suggests the effectiveness of domestic and global regulations. Despite this, sedimentary PBDE concentrations may pose adverse health risks to benthic organisms and humans.