Species-specific and habitat-dependent bioaccumulation of halogenated flame retardants in marine organisms from estuary to coastal seas.

Halogenated flame retardants (HFRs) have attracted global attention owing to their adverse effects on ecosystems and humans. The Shandong Peninsula is the largest manufacturing base for HFRs in East Asia, yet its impacts on marine ecosystems are unclear. Seventeen HFRs were analyzed in organisms captured from the Xiaoqing River estuary, Bohai Sea (BS), Yellow Sea and Northern East China Sea to investigate the distribution and bioaccumulation of HFRs on a broad scale. The results showed a downward trend in ΣHFR concentrations from the estuary (37.7 ng/g lw on average) to Laizhou Bay (192 ng/g lw) and to coastal seas (3.13 ng/g lw). The concentrations of ΣHFRs were significantly higher in demersal fish (0.71-198 ng/g lw) and benthic invertebrates (0.81-3340 ng/g lw) than in pelagic fish (0.30-27.6 ng/g lw), reflecting a habitat dependence. The concentrations of higher-brominated homologs were greater in benthic invertebrates, whereas a greater level of lower-brominated PBDE congeners was observed in fish, suggesting different profiles between species. Furthermore, the analogue composition of HFRs in fish was similar to that in the dissolved phase of seawater, whereas the HFR pattern in benthic invertebrates was consistent with the profile in sediment. The concentrations of HFRs in organisms vary widely depending on emissions from anthropogenic activities, whereas bioaccumulation patterns are strongly influenced by species and habitat.

Occurrence and ecological risk assessment of neonicotinoids and related insecticides in the Bohai Sea and its surrounding rivers, China.

Systemic insecticides like neonicotinoids and the phenylpyrazole insecticide fipronil are the most widely applied insecticides around the world. Multiple studies analyzed insecticide residues in freshwater systems, but data on seawater contamination levels are scarce. This study investigates the spatiotemporal distribution and ecological risk assessment of fipronil, neonicotinoids, sulfoxaflor and selected transformation products (TPs) in the Chinese Bohai Sea and its surrounding rivers. Well-established neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) and TPs of fipronil and imidacloprid were frequently detected (detection frequency (DF): 42-100%) in freshwater. The median total insecticide concentration in freshwater was significantly higher in summer (72.4 ng•L-1) than in fall (23.4 ng•L-1), with major contributions from neonicotinoids, suggesting that pollution originates mostly from diffuse sources. In 2018, acetamiprid, desnitro-imidacloprid, fipronil-desulfinyl and thiacloprid were abundant in seawater (DF: 47-100%), indicating a high stability of acetamiprid and thiacloprid and a rapid photodegradation of fipronil and imidacloprid in surface waters. These results indicate that the continued use of these parent compounds may lead to their accumulation and/or of their TPs in shallow coastal seas. Consequently, this may lead to their transport to open seas, increasing their potential risk to marine organisms. Similarities between contaminant fingerprints in freshwater and seawater strongly suggest riverine discharges as main pollution source of adjacent coastal areas. This is the first study to perform an ecological risk assessment of fipronil, neonicotinoids, sulfoxaflor and selected TPs on marine ecosystems. Fipronil and its TPs demonstrated to be environmentally relevant with potential high risks for aquatic species. Our study provides novel insights into the fate and ecological risk of fipronil, neonicotinoids, sulfoxaflor and their TPs to marine species in shallow coastal seas.

Decabromodiphenyl Ether versus Decabromodiphenyl Ethane: Source, Fate, and Influencing Factors in a Coastal Sea Nearing Source Region.

Both decabromodiphenyl ether (BDE 209) and decabromodiphenyl ethane (DBDPE) are still produced in large quantities in China, especially in the Shandong Province closed to the Bohai Sea (BS). This study conducted a comprehensive investigation of the distribution and budget of brominated flame retardants (BFRs) in the BS. BDE 209 was the predominant BFR in most of the investigated rivers flowing into the BS, although DBDPE exceeded BDE 209 in certain rivers as a result of the replacement of BDE 209 with DBDPE in North China. The spatial distributions of BFRs in the rivers were controlled by the proximity of the BFR manufacturing base and the extent of urbanization. BFRs' spatial distribution in the BS was influenced by a combination of land-based pollution sources, environmental parameters (e.g., suspended particulate matter, particulate organic carbon, and particulate black carbon), and hydrodynamic conditions. The spatial variation trend of BDE 209/DBDPE ratios in various environmental media provided useful information. Vertically, the BDE 209/DBDPE ratio decreased from the seawater surface layer to the sediment, indicating their differential transport in the BS. A multi-box mass balance model and analysis of BDE 209 showed that degradation was the primary sink of BFRs in seawater (∼68%) and surface sediment (∼72%) in the BS.

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.

Distributions, transports and fates of short- and medium-chain chlorinated paraffins in a typical river-estuary system.

Chlorinated paraffins (CPs) are widely employed in a variety of domestic and industrial products, and are ubiquitously detected in the environment. Short-chain chlorinated paraffins (SCCPs) have been listed in the Stockholm Convention as persistent organic pollutants (POPs), but not medium-chain chlorinated paraffins (MCCPs), even though they exhibit physicochemical properties and environmental behaviors similar to SCCPs. However, very limited data are available regarding their environmental behaviors and fates in river-estuary systems. China is the major producer of chlorinated paraffins (CPs), and Shandong Province is the main producer of CPs in China. Here, we investigated the distribution, transport, and fate of SCCPs and MCCPs in a heavily polluted river in Shandong Province, aiming to explore the distributions of CPs between dissolved and particulate phases, and between water and sediment phases, as well as the transport of CPs from river headwaters to estuaries and the roles of the estuarine turbidity maximum zone (ETM) on the fate of CPs. CP concentrations in sediments were 9.1-16,000 ng/g dw (mean value: 1000 ng/g dw) for SCCPs and 2.4-27,000 ng/g dw (mean value: 4400 ng/g dw) for MCCPs. In the water column, CP concentrations were 7.4-470 ng/L for SCCPs (mean value: 43 ng/L) and 4.0-120 ng/L for MCCPs (mean value: 27 ng/L). CP concentrations in riverine sediments were among the highest worldwide. SCCPs accounted for 95% of CPs (sum of SCCPs and MCCPs) in the dissolved phase. Cities around the river basin were found to be important pollution sources for CPs. Long-chained and more chlorinated congeners with larger LogKow values might be more likely to be 'salted-out', and thus, will be sequestrated in sediments in the ETM, while those lighter congener groups with relatively high water solubility were prone to be transported by water flow to larger distances.

Source, fate and budget of Dechlorane Plus (DP) in a typical semi-closed sea, China.

Dechlorane Plus (DP), which has severe effects on marine ecosystems, has been proposed for listing under the Stockholm Convention as a persistent organic pollutant (POPs). This study was the first comprehensive investigation of the concentration and fate of DP in the Bohai Sea (BS) based on determination of river estuary water, river estuary sediment, surface seawater, bottom seawater, and sea sediments samples. The highest water DP levels were found in river estuary in Tianjin in North China due to the huge usage of DP in recent years, and spatial distribution analysis indicates it was mainly affected by regional high urbanization and emission of E-waste. The spatial distribution of DP in the BS was mainly affected by a combination of coastal hydrodynamics and land anthropogenic activities. On the basis of multi-box mass balance, simulations of DP in seawater showed an increase from 2014 to 2025, before leveling off at 184 pg L -1 by a constant DP input to the BS. Riverine discharge almost contributed to the total input (∼99%) and dominated the DP levels in the BS. Degradation of DP accounted for 55.3% and 78.1% of total DP output in seawater and sediment, respectively, indicating that degradation mainly affected decline of DP in the environment.

Legacy and novel halogenated flame retardants in seawater and atmosphere of the Bohai Sea: Spatial trends, seasonal variations, and influencing factors.

Seventeen halogenated flame retardants (HFRs) were concurrently analyzed in surface seawater and low atmospheric samples from the Bohai Sea during four research cruises. HFRs mainly existed in particulate phases, and in general decabromodiphenyl ethane (DBDPE) was the predominant compound in both air and water samples. Relatively high concentrations were observed in the water of Laizhou Bay (LB), where the largest manufacturing base of brominated flame retardants (BFRs) in China is located and weak water exchange occurs. Transport from LB by coastal currents may be the main source of BFRs in some areas without emission sources. The HFRs in seawater exhibited distinct seasonal variation, with significantly higher concentrations in winter than those in summer. The controlling factors include the resuspension of sediment induced by large wind waves in winter and phytoplankton scavenging in spring and seawater stratification in summer. HFRs composition varied largely in different seasons, due to the different extents of riverine input and atmospheric deposition. Normally, for air masses passing through the nearby industrial regions, high concentrations of DBDPE (up to 1780 pg m-3) co-existed with high total suspended particle (TSP) levels (up to 150 µg m-3). The estimated atmospheric deposition fluxes of HFRs were 19, 51, and 80 kg season-1 in spring, summer, and winter, respectively, indicating that the Bohai Sea is a sink of HFRs via atmospheric deposition. This study has increased our understanding of the behaviors and fates of the legacy and novel HFRs in the shallow coastal sea.

Halogenated flame retardants in the sediments of the Chinese Yellow Sea and East China Sea.

With the phasing out of traditional polybrominated diphenyl ethers (PBDEs), significant volumes of alternative brominated flame retardants (aBFRs) are being used and released into the environment compartment, especially in coastal regions. The levels and distribution of PBDEs, aBFRs, and dechlorane plus (DPs) were investigated in the surface sediments of the Yellow Sea (YS) and East China Sea (ECS) to examine the distribution and sources of these hydrophobic contaminants. The level and distribution of pollutants in the sediments of YS and ECS show obvious regional differences. As a major replacement for decabromodiphenyl ether (BDE 209), decabromodiphenyl ethane (DBDPE) was the dominant compound observed in the surface sediments, with a concentration one order of magnitude higher than that of BDE 209. High concentrations were found in the depositional zones of the YS, indicating that these contaminants may originate from land-based pollution sources (likely from the Laizhou Bay manufacturing base) near the Bohai Sea. The pollutants can be carried by the coastal current together with the sediment from the Yellow River, transported through the Bohai Strait and deposited in the mud zone of Northern and Southern YS. Low levels of halogenated flame retardants (HFRs) were found in the estuary of the Yangtze River and ECS, indicating that Yangtze River contributes less HFRs to the region. Riverine discharge, atmospheric deposition, surface runoff, ocean current system, and mud area deposition effects may be significant factors influencing the distributions of HFRs.

Fates and ecological effects of current-use pesticides (CUPs) in a typical river-estuarine system of Laizhou Bay, North China.

Current-use pesticides (CUPs) are widely applied in agriculture; however, little is known about their environmental behaviors, especially in the freshwater-seawater transitional zone. Water and sediment samples were collected in an intensively human impacted river (Xiaoqing River) from the headwaters to Laizhou Bay to investigate the distributions and environmental fates of four CUPs: trifluralin, chlorothalonil, chlorpyrifos, and dicofol. These CUPs were frequently detected in water and sediment samples. ∑CUPs in water and sediment samples ranged from 1.20 to 100.2 ng L-1 and 6.6-2972.5 ng g-1 dry weight (dw), respectively. Chlorpyrifos and chlorothalonil were the most abundant CUPs in water and sediment samples, respectively. Spatial distribution of CUPs in the Xiaoqing River aquatic ecosystem was mainly influenced by point sources, agricultural activities, the dilution effect by seawater, and environmental parameters. Field-based sediment water partitioning coefficients, normalized by organic carbon (log Koc), were calculated. Interestingly, temperature and salinity exhibited significant impacts on the distribution of log Koc of the four CUPs. The effect of temperature on the distribution of log Koc of the four CUPs varied between the CUPs. In most water samples, the levels of chlorpyrifos exceed the freshwater screening benchmarks. Hence, urgent control measures need to be devised and implemented.

From headwaters to estuary: distribution, sources, and ecological risk of polycyclic aromatic hydrocarbons in an intensively human-impacted river, China.

Located in the Shandong Province, North China, the Xiaoqing River is heavily contaminated by industrial wastewater and domestic sewage. However, it plays a significant role with regard to irrigation for agriculture in the river basin. In this study, spatial distribution, sources, and the ecological risk of aqueous polycyclic aromatic hydrocarbons (PAHs) in the Xiaoqing River Basin were investigated from the headwaters to the estuary. Fifteen USEPA priority PAHs (except naphthalene) were quantified in water particulate and soluble phases and in sediment samples. Σ15PAHs concentrations in the sediment varied from 17.15 to 3808.01 ng/g dry weight (dw), with an average of 988.72 ng/g dw, suggesting severe pollution of the Xiaoqing River in comparison with other rivers worldwide. The composition of PAHs was characterized by the high abundance of 4-ring and 5-ring PAHs in sediments and 2-ring and 3-ring PAHs in water. Industrial wastewater is a significant source of PAHs. In the river section, point source was the main factor affecting the distribution of PAHs, while in the estuary region, estuarine turbidity maximum zone (ETM), riverine flow and discharge, and its hydrodynamic parameters play more key roles on PAH levels. Molecular diagnostic ratios have proved that PAHs in sediments were derived from mixed sources, primarily a combination of several combustion processes. Toxicity equivalency concentrations (TEQs) and Ecological risk assessment by Sediment Quality Guidelines indicated that PAHs in sediments might have certain unfavorable effects on ecosystems in certain sites.

From headwaters to estuary: Distribution and fate of halogenated flame retardants (HFRs) in a river basin near the largest HFR manufacturing base in China.

With the gradual phasing out of polybrominated diphenyl ethers (PBDEs), market demands for alternative halogenated flame retardants (HFRs) are increasing. The Laizhou Bay area is the biggest manufacturing base for brominated flame retardants (BFRs) in China, and the Xiaoqing River is the largest and most heavily contaminated river in this region. Water and sediment samples were collected from the headwaters to the estuary of the Xiaoqing River to investigate the distribution and fate of HFRs [i.e., PBDEs, alternative brominated flame retardants (aBFRs) and dechlorane plus (DPs). In the water samples, DPs was the most abundant flame retardant (median: 11.7ng/L), followed by decabromodiphenylethane (DBDPE) (5.92ng/L). In the sediment samples, DBDPE was the predominant flame retardant (39.5ng/g dw), followed by decabromodiphenyl ether (BDE 209) (2.81ng/g dw). The levels of DBDPE exceeded those of BDE 209 in most samples, indicating the overwhelming replacement of BDE 209 by DBDPE in this area. In the river section of this study, point source and atmospheric deposition followed by land runoff were the major factors influencing the distribution of HFRs, whereas in the estuary, riverine discharge, the estuarine maximum turbidity zone (MTZ), and hydrodynamic parameters played more important roles. Manufacturing is a significant source of contamination of the Xiaoqing River basin through atmospheric deposition and wastewater discharge.

Spatial distribution and seasonal variation of four current-use pesticides (CUPs) in air and surface water of the Bohai Sea, China.

Current-use pesticides (CUPs) are widely used in agriculture, and some are listed as persistent organic pollutants (POPs) due to their bioaccumulative and toxic properties. China is one of the largest producers and users of pesticides in the world. However, very limited data are available about the environmental fates of CUPs. Four CUPs (trifluralin, chlorothalonil, chlorpyrifos, and dicofol) in surface seawater and low atmospheric samples taken during research cruises on the Bohai Sea in August and December 2016 and February 2017 were analyzed, we added the spring data sampled in May 2012 to the discussion of seasonal variation. In our study, chlorpyrifos was the most abundant CUPs in the gas phase with a mean abundance of 59.06±126.94pgm-3, and dicofol had the highest concentration dissolved in seawater (mean: 115.94±123.16pgL-1). The concentrations of all target compounds were higher during May and August due to intensive use and relatively high temperatures in the spring and summer. Backward trajectories indicated that air masses passing through the eastern coast of the Bohai Sea contained high concentrations of pollutants, while the air masses from the Bohai and Yellow Seas were less polluted. The high concentration of pollutants in seawater was not only influenced by high yields from the source region of production or usage, but also by input from polluted rivers. Volatilization from surface water was found to be an important source of trifluralin and chlorpyrifos in the air. Air-sea gas exchange of chlorothalonil underwent strong net deposition (mean FRs: 51.67), which was driven by higher concentrations in air and indicates that the Bohai Sea acted as a sink for chlorothalonil.

Polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (aBFRs) in sediments from four bays of the Yellow Sea, North China.

The distribution characteristics and potential sources of polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardants (aBFRs) were investigated in 54 surface sediment samples from four bays (Taozi Bay, Sishili Bay, Dalian Bay, and Jiaozhou Bay) of North China's Yellow Sea. Of the 54 samples studied, 51 were collected from within the four bays and 3 were from rivers emptying into Jiaozhou Bay. Decabromodiphenylethane (DBDPE) was the predominant flame retardant found, and concentration ranged from 0.16 to 39.7 ng g(-1) dw and 1.13-49.9 ng g(-1) dw in coastal and riverine sediments, respectively; these levels were followed by those of BDE 209, and its concentrations ranged from n.d. to 10.2 ng g(-1) dw and 0.05-7.82 ng g(-1) dw in coastal and riverine sediments, respectively. The levels of DBDPE exceeded those of decabromodiphenyl ether (BDE 209) in most of the samples in the study region, whereas the ratio of DBDPE/BDE 209 varied among the four bays. This is indicative of different usage patterns of brominated flame retardants (BFRs) and also different hydrodynamic conditions among these bay areas. The spatial distribution and composition profile analysis indicated that BFRs in Jiaozhou Bay and Dalian Bay were mainly from local sources, whereas transport from Laizhou Bay by coastal currents was the major source of BFRs in Taozi Bay and Sishili Bay. Both the ∑PBDEs and ∑aBFRs (sum of pentabromotoluene (PBT), 2,3-diphenylpropyl-2,4,6-tribromophenyl ether (DPTE), pentabromoethylbenzene (PBEB), and hexabromobenzene (HBB)) were at low concentrations in all the sediments. This is probably attributable to a combination of factors such as low regional usage of these products, atmospheric deposition patterns, coastal currents transportation patterns, and degradation processes for higher BDE congeners. This paper is the first study that has investigated the levels of DBDPE in the coastal sediments of China's Yellow Sea.