Aggravating Pollution of Emerging Aryl Organophosphate Esters in Urban Estuarine Sediments of South China.

Emerging aryl organophosphate esters (aryl-OPEs) have been employed as substitutes for organohalogen flame retardants in recent years; however, their environmental occurrence and associated impacts in urban estuarine sediments have not been adequately investigated, impeding regulatory decision-making. Herein, field-based investigations and modeling based on surface sediment and sediment core analysis were employed to uncover the historical pollution and current environmental impacts of aryl-OPEs in the Pearl River Estuary, South China. Our results revealed a substantial increase in aryl-OPE emission, particularly emerging aryl-OPEs, through sediment transport to the estuary since the 2000s. The emerging aryl-OPEs comprised 83% of the total annual input in the past decade, with an average annual input of 155,000 g. Additionally, the emerging-to-traditional aryl-OPE concentration ratios increased with decreasing distance from the shore, peaking in the highly urbanized riverine outlets. These findings indicate that inventories of emerging aryl-OPEs are likely increasing in estuarine sediments and their emissions are surpassing those of traditional aryl-OPEs. Our risk-based priority screening approach indicates that some emerging aryl-OPEs, particularly bisphenol A bis(diphenyl phosphate), can pose a higher environmental risk than traditional aryl-OPEs in estuarine sediments. Overall, our study highlights the importance of recognizing the environmental impacts of emerging aryl-OPEs.

Pharmaceutical Residues in Edible Oysters along the Coasts of the East and South China Seas and Associated Health Risks to Humans and Wildlife.

The investigation of pharmaceuticals as emerging contaminants in marine biota has been insufficient. In this study, we examined the presence of 51 pharmaceuticals in edible oysters along the coasts of the East and South China Seas. Only nine pharmaceuticals were detected. The mean concentrations of all measured pharmaceuticals in oysters per site ranged from 0.804 to 15.1 ng g-1 of dry weight, with antihistamines being the most common. Brompheniramine and promethazine were identified in biota samples for the first time. Although no significant health risks to humans were identified through consumption of oysters, 100-1000 times higher health risks were observed for wildlife like water birds, seasnails, and starfishes. Specifically, sea snails that primarily feed on oysters were found to be at risk of exposure to ciprofloxacin, brompheniramine, and promethazine. These high risks could be attributed to the monotonous diet habits and relatively limited food sources of these organisms. Furthermore, taking chirality into consideration, chlorpheniramine in the oysters was enriched by the S-enantiomer, with a relative potency 1.1-1.3 times higher when chlorpheniramine was considered as a racemate. Overall, this study highlights the prevalence of antihistamines in seafood and underscores the importance of studying enantioselectivities of pharmaceuticals in health risk assessments.

Medicating the coast in a metropolitan city: Enantiomeric profiles and joint probabilistic risk assessment of antidepressants and antihistamines.

Pharmaceuticals are receiving increasing attention as emerging contaminants in the aquatic environment. Herein, we investigated the occurrence of 11 antidepressants, 6 antihistamines and 4 metabolites in treated wastewater effluents, rivers, stormwater, and seawater in Hong Kong, with special focus on chirality. The average levels of ∑pharmaceuticals ranged from 0.525 to 1070 ng/L in all samples and the total annual mass load of target pharmaceuticals in the marine environment of Hong Kong was 756 kg/y. Antihistamines accounted for >80 % of ∑pharmaceuticals, with diphenhydramine and fexofenadine being predominant. The occurrence and enantiomeric profiles of brompheniramine and promethazine sulfoxide were reported in global natural waters for the first time. Among chiral pharmaceuticals, mirtazapine and fexofenadine exhibited R-preference, while others mostly exhibited S-preference, implying that the ecological risks derived from achiral data for chiral pharmaceuticals may be biased. The joint probabilistic risk assessment of fluoxetine revealed that R-fluoxetine and rac-fluoxetine presented different ecological risks from that of S-fluoxetine; Such assessment also revealed that target pharmaceuticals posed only minimal to low risks, except that diphenhydramine posed an intermediate risk. As estimated, 10 % aquatic species will be affected when the environmental level of diphenhydramine exceeds 7.40 ng/L, which was seen in 46.9 % samples. Collectively, this study highlights further investigations on the enantioselectivity of chiral pharmaceuticals, particularly on environmental behavior and ecotoxicity using local aquatic species as target organisms.

New Perspective to Understand and Prioritize the Ecological Impacts of Organophosphate Esters and Transformation Products in Urban Stormwater and Sewage Effluents.

Due to their prevalence in urban contaminated water, the driving factors of organophosphate esters (OPEs) need to be well examined, and their related ecological impacts should include that of their transformation products (TPs). Additionally, a robust framework needs to be developed to integrate multiple variables related to ecological impacts for improving the ecological health assessment. Therefore, OPEs and TPs in urban stormwater and wastewater in Hong Kong were analyzed to fill these gaps. The results revealed that the total concentrations of OPEs in stormwater were positively correlated with the area of transportation land. Individual TP concentrations and the mass ratios of individual TPs/OPEs were somewhat higher in sewage effluents than that in stormwater. OPEs generally showed relatively higher risk quotients than TPs; however, the total risk quotients increased by approximately 38% when TPs were factored in. Moreover, the molecular docking results suggested that the investigated TPs might cause similar endocrine disruption in marine organisms as their parent OPEs. This study employed the Toxicological-Priority-Index scheme to successfully integrate the ecological risks and endocrine-disrupting effects to refine the ecological health assessment of the exposure to OPEs and their TPs, which can better inform the authority on the prioritization for regulating these contaminants of emerging concern in urban built environments.

Simultaneous Dissemination of Nanoplastics and Antibiotic Resistance by Nematode Couriers.

Nanoplastics (NPs) are increasingly recognized as a newly emerging pollutant in the environment. NPs can enable the colonization of microbial pathogens on their surfaces and adsorb toxic pollutants, such as heavy metals and residual antibiotics. Although the dissemination of plastic particles in water bodies and the atmosphere is widely studied, the dissemination of NPs and adsorbed pollutants on land, via biological means, is poorly understood. Since soil animals, such as the bacterivorous nematode Caenorhabditis elegans (C. elegans), are highly mobile, this raises the possibility that they play an active role in disseminating NPs and adsorbed pollutants. Here, we established that antibiotic-resistant bacteria could aggregate with antibiotic-adsorbed NPs to form antibiotic-adsorbed NP-antibiotic resistant bacteria (ANP-ARB) aggregates, using polymyxins (colistin) as a proof-of-concept. Colistin-resistant mcr-1 bearing Escherichia coli from a mixed population of resistant and sensitive bacteria selectively aggregate with colistin-ANPs. In the soil microcosm, C. elegans fed on ANP-ARB clusters, resulting in the rapid spread of ANP-ARB by the nematodes across the soil at a rate of 40-60 cm per day. Our work revealed insights into how NPs could still disseminate across the soil faster than previously thought by "hitching a ride" in soil animals and acting as agents of antibiotic-resistant pathogens and antibiotic contaminants. This poses direct risks to ecology, agricultural sustainability, and human health.

Residue Distribution and Daily Exposure of Per- and Polyfluoroalkyl Substances in Indica and Japonica Rice.

Per- and polyfluoroalkyl substances (PFAS) have excellent chemical stability but have adverse environmental impacts of concern. Furthermore, bioaccumulation of PFAS in rice varieties─which is the essential staple food crop in Asia─has not been verified. Therefore, we cultivated Indica (Kasalath) and Japonica rice (Koshihikari) in the same Andosol (volcanic ash soil) paddy field and analyzed the air, rainwater, irrigated water, soil, and rice plants for 32 PFAS residues, throughout the cultivation to human consumption. During the rice cultivation period, the cultivation environment in atmospheric particulate matter (PM) constituted perfluoroalkyl carboxylic acids (PFCAs), with minimal perfluorinated sulfonic acids (PFSAs). Furthermore, perfluorooctanesulfonic acid (PFOS) migrates at a PM > 10 to drop in a cultivation field and was conducive to leakage and accumulation of PFCAs in air particles in the field environment. Moreover, precipitation was a sources of irrigation water contamination, and cultivated soil with a high carbon content could capture PFSAs and PFCAs (over C10). There were no major differences in residual PFAS trends in the rice varieties, but the distribution of PFAS in the growing soil, air, and rainwater differed. The edible white rice part was mainly affected by irrigation water in both varieties. Monte Carlo simulations of daily exposure assessments of PFOS, PFOA, and perfluorononanic acid showed similar results for Indians consuming Indica rice and Japanese consuming Japonica rice. The results indicate that the ultratrace PFAS residue concentrations and their daily exposure were not cultivar-specific.

Source Apportionment, Hydrodynamic Influence, and Environmental Stress of Pharmaceuticals in a Microtidal Estuary with Multiple Outlets in South China.

Pharmaceutical residues in the environment are of great concern as ubiquitous emerging contaminants. This study investigated the presence of 40 pharmaceuticals in water and sediment of the Pearl River Estuary (PRE) in the wet season of 2020. Among psychiatric drugs, only diazepam was found in water samples while six of them were detected in the sediment. The Σantibiotics levels ranged from 6.18 to 35.9 ng/L and 2.63 to 140 ng/g dry weight in water and sediment samples, respectively. Fluoroquinolones and tetracyclines were found well settling in the outlet sediment, while sulfonamides could be released from disturbed sediment under stronger tidal wash-out conditions. After entering the marine waters, pharmaceuticals tended to deposit at the PRE mouth by the influence of the plume bulge and onshore invasion of deep shelf waters. Low ecological risks to the aquatic organisms and of causing antimicrobial resistance were identified. Likewise, hydrological modeling results revealed insignificant risks: erythromycin-H2O and sulfamethoxazole discharged through the outlets constituted 30.8% and 6.74% of their environmental capacity, respectively. Source apportionment revealed that pharmaceutical discharges through the Humen and Yamen outlets were predominantly of animal origin. Overall, our findings provide strategic insights on environmental regulations to further minimize the environmental stress of pharmaceuticals in the PRE.

A systematic study of microplastic occurrence in urban water networks of a metropolis.

The release of microplastics from sewage treatment works (STWs) into the oceans around coastal cities is well documented. However, there are fewer studies on the microplastic abundance in stormwater drains and their emissions into the coastal marine environment via sewage and stormwater drainage networks. Here, we comprehensively investigated microplastic abundance in 66 sewage and 18 sludge samples collected from different process stages at three typical STWs and 36 water samples taken from six major stormwater drains during the dry and wet seasons in Hong Kong, which is a metropolitan city in south China. The results showed that microplastics were detected in all the sewage and stormwater samples, with the abundance ranging from 0.07 to 91.9 and from 0.4 to 36.48 particles/L, respectively, and in all the sludge samples with the abundance ranging from 167 to 936 particles/g (d. w.). There were no significant seasonal variations in the microplastic abundance across all samples of sewage, sludge, and stormwater. For both waterborne sample types, a smaller size (0.02-0.3 mm) and fiber shape were the dominant characteristics of the microplastics. Polyethylene terephthalate (PET) and polypropylene (PP) were the most abundant polymer types in the sewage samples, while polyethylene (PE), PET, PP, and PE-PP copolymer were the most abundant polymer types in the stormwater samples. The estimated range of total daily microplastic loads in the effluent from STWs in Hong Kong is estimated to be 4.48 × 109 - 2.68 × 1010 particles/day, demonstrating that STWs are major pathways of microplastics in coastal environments despite the high removal percentage of microplastics in sewage treatment processes examined. This is the first comprehensive study on microplastics in the urban waters of a coastal metropolis. However, further studies on other coastal cities will enable an accurate estimation of the microplastic contribution of stormwater drains to the world's oceans.

Occurrence, spatial distribution, and partitioning behavior of marine lipophilic phycotoxins in the Pearl River Estuary, South China.

The occurrence, spatial distribution, and partitioning behavior of 17 marine lipophilic phycotoxins (MLPs) in surface and bottom seawater, particulate organic matter (POM), and surface sediment from the Pearl River Estuary (PRE) were investigated to understand current contamination and the potential risks to marine ecosystems in this region. Nine MLPs were detected, including azaspiracid1-3, gymnodimine, okadaic acid, dinophysistoxin 1-2, pectenotoxin2 (PTX2), and homoyessotoxin, with Σ17MLP concentrations ranging 545-12,600 pg L-1 and 619-8,800 pg L-1 in surface and bottom seawater, respectively; 0-294 ng g-1 and 0.307-300 ng g-1 dry weight (dw) in surface and bottom POM, respectively; and 3.90-982 pg g-1 dw in surface sediment. Lower Σ17MLP levels in the seawater were found at the mouth of the PRE, and gradually increased with increasing distance offshore. According to the calculated partition coefficient, the affinity of MLPs for the aquatic environment components was as follows (from highest to lowest): POM > seawater > sediment. Overall, the distribution and migration of MLPs in the PRE may depend on partition coefficients, the organic carbon fraction, and environmental factors.

Significant input of organophosphate esters through particle-mediated transport into the Pearl River Estuary, China.

Most organophosphate esters (OPEs) enter the marine environment through atmospheric deposition and surface runoff, yet the role of particle-mediated transport in their inputs and loss processes remains poorly understood. To fill this knowledge gap, samples of size-segregated atmospheric particles, suspended particulate matter (SPM) in seawater, and sediments in the Pearl River Estuary (PRE) were collected and analyzed for OPEs. Total concentrations of atmospheric particulate OPEs showed a decreasing trend with increasing offshore distance in the PRE. The spatial and vertical distribution patterns of OPEs in SPM were diverse, which could be largely affected by physicochemical properties of SPM, marine microbial activities, hydrodynamic conditions, and environmental factors. Sediment in the region close to Modaomen outlet was subject to relatively high OPE concentrations. Approximately 24,100 and 65,100 g d-1 of particulate OPEs were imported into the PRE through atmospheric deposition and surface runoff, respectively; 83,200 g d-1 of which were exported to the open sea. The input and environmental fate of particulate OPEs were found to be dependent on sources, particulate media, and chemical species. The present study provides insights into the influence of OPEs in the PRE through particle-mediated transport and calls for more concern on anthropogenic impact on the estuary.

Spatiotemporal occurrence of phthalate esters in stormwater drains of Hong Kong, China: Mass loading and source identification.

Urban stormwater is an important pathway for transporting anthropogenic pollutants to water bodies. Phthalate esters (PAEs) are endocrine disruptors owing to their estrogenic activity and potential carcinogenicity and their ubiquitous presence has garnered global interest. However, their transportation by urban stormwater has been largely overlooked. This study, for the first time, investigated 15 PAEs in stormwater from six major stormwater drains in the highly urbanized Hong Kong, a major metropolitan city in China. The results showed that PAEs were ubiquitous in the stormwater of Hong Kong, with total concentrations (∑15PAEs) spanning from 195 to 80,500 ng/L. Bis(2-n-butoxyethyl) phthalate (DBEP), diisopentyl phthalate (DiPP), dicyclohexyl phthalate (DCHP) and di-n-pentyl phthalate (DnPP) were detected in stormwater for the first time. Spatial variations in PAEs were observed among different stormwater drains, possibly due to the different land use patterns and intensities of human activities in their respective catchments. The highest and lowest levels of ∑15PAEs were found in Kwai Chung (3860 ± 1960 ng/L) and the Ng Tung River (672 ± 557 ng/L), respectively. Additionally, significantly higher concentrations of ∑15PAEs in stormwater were found in the wet season (2520 ± 2050 ng/L) than in the dry season (947 ± 904 ng/L). Principal component analysis classified domestic and industrial origins as two important sources of PAEs in the stormwater of Hong Kong. Stormwater played a crucial role in transporting PAEs, with an estimated annual flux of 0.705-29.4 kg. Thus, possible stormwater management measures were proposed to protect the receiving environment and local ecosystems from stormwater.

Fluorine mass balance analysis and per- and polyfluoroalkyl substances in the atmosphere.

Given that only a small number of per- and polyfluoroalkyl substances (PFAS) are routinely monitored, levels of PFAS in the atmosphere may be underestimated. A protocol including analyses of target PFAS (n = 50), water-soluble fluoride, and total fluorine has been proposed and applied to atmospheric samples. The whole method recovery (including extraction recovery and sampling efficiency) of 90-110% were obtained for the majority of compounds (48/50) with low deviations between replicates (< 20%). Fluorotelomer alcohols were the most prevalent PFAS in the indoor air, while the outdoor air was dominated by the ultrashort-chain ionic PFAS (e.g., trifluoroacetic acid and perfluoropropanoic acid). Concentrations of organofluorine (OF) compounds calculated from the fluorine mass balance ranged from 1.74 ng F/m3 to 14.3 ng F/m3 and from 52.0 ng F/m3 to 1100 ng F/m3 in the particulate and gaseous phases, respectively, whereas only a minor proportion (around 1%) could be explained by target PFAS. In indoor air, OF compounds were observed in relatively high levels and with a shift to the fine particles (PM<1) . Our results reveal a large proportion of unidentified OF signatures in the atmosphere and suggest the need to use multiple approaches to improve our understanding of airborne fluorinated substances.

Phthalate esters in seawater and sediment of the northern South China Sea: Occurrence, distribution, and ecological risks.

In this study, the occurrence and distribution of 15 phthalate esters (PAEs) in seawater and sediment from the northern South China Sea (NSCS) were investigated for the first time to improve understanding on the contamination status of PAEs in this region. The concentrations of total PAEs (∑15 PAEs) were found to range from 68.8 to 1500 ng/L, 46.0 to 7800 ng/L, and 49.2 to 440 ng/g dry weight in surface seawater, bottom seawater, and sediment, respectively. Among the 15 PAEs, dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP) were the predominant PAE congeners, with mean contributions of 44.7% and 24.0% in surface water, and 42.7% and 25.8% in bottom water, respectively. Moreover, diisobutyl phthalate (DiBP) constituted the majority of ∑15 PAEs in the sediment (61.3%). Comparatively high concentrations of Σ15 PAEs were observed in seawater at the sites within the western NSCS, whereas relatively higher concentrations of Σ15 PAEs were detected in sediments at the eastern NSCS. River input and atmospheric deposition could be the main sources of PAEs in the NSCS. Preliminary risk assessment implied that DBP, DiBP, and DEHP posed low to high potential risks for marine organisms at different trophic levels. These results would be valuable for implementing effective control measures and remediation strategies for PAEs contamination in the region.

Simultaneous analysis of neutral and ionizable per- and polyfluoroalkyl substances in air.

A new method is preliminarily validated for the simultaneous analysis of ionic and neutral per- and polyfluoroalkyl substances (PFASs) in both particulate and gaseous phases in air using a nanosampler-20 air sampler (NS20) composed of quartz fiber filters (QFFs), polyurethane foam (PUF) and artificial activated charcoal (GAIAC™). Perfluoroalkane sulfonamido ethanols (FOSEs) mainly remained in PUF, whereas the other neutral analytes were mainly found in GAIAC. Satisfactory recoveries were obtained for FOSEs, fluorotelomer alcohols (FTOHs), fluorotelomer iodides (FTIs), ranging fron 70%-120%, moderate recoveries were achieved for perfluorinated iodine alkanes (FIAs) and diiodofluoroalkanes (FDIAs), ranging from 50%-70%, while poor recoveries were found for perfluoroalkane sulfonamides (FOSAs). Breakthrough experiments revealed that almost all the target analytes were well trapped in GAIAC™, including the very volatile 4:2 FTOH. Applying to real sampling, our results showed that 6:2 and 8:2 FTOH were the most abundant species, with levels detected at 190 pg/m3 and 160 pg/m3. To the best of our knowledge, FDIAs were detected in ambient air for the first time at an average level of 8.3 pg/m3. Overall, the profiles observed from the real air samples reflected current industrial transition from longer chain to shorter chain in PFAS production. Our results revealed that the current method is promising for a more comprehensive understanding on the fates of PFASs in air.

Tracing human footprint and the fate of atmospheric polycyclic aromatic hydrocarbons over the Pearl River Estuary, China: Importance of particle size.

Few studies have focus on size-segregated particulate polycyclic aromatic hydrocarbons (PAHs) in the oceanic atmosphere. To better understand the impacts of anthropogenic activities on atmospheric PAHs, a heavily human-impacted estuary, the Pearl River Estuary (PRE), was chosen as a case study. We collected gaseous and size-segregated particulate samples of ambient air at two sites in the PRE, as well as from the exhaust emissions of the cruise ship used in the sampling campaign. In addition, surface seawater samples were collected. Size distribution patterns of high molecular-weight (HMW) particulate PAHs were bimodal at one site and unimodal at the other, suggesting PAHs at the former site were derived not only from long-range atmospheric transport but also from local sources. Gas-particle partition coefficients of HMW PAHs in size-segregated particles varied with particle sizes, mostly higher in fine particles (<1.8 µm). Dry deposition flux of Σ23PAHs (defined as the sum of 23 PAHs) was contributed mainly from coarse particles (>1.8 µm), and HMW PAHs with lower dry deposition velocities could be transported farther away. With respect to air-water exchange, lower MW PAHs tended to have net volatilization, whereas higher MW PAHs were likely to have net deposition. This study sheds new lights on the origins and fate of atmospheric PAHs over the PRE, and suggests the emissions of maritime traffics should be regulated. Collected near the metropolitan regions, atmospheric PAHs over the PRE were highly affected by anthropogenic activities, especially for HMW PAHs, which could pose a long-lasting impact to the oceanic atmosphere and marine organisms.

Occurrence and spatial distribution of legacy and novel brominated flame retardants in seawater and sediment of the South China sea.

The occurrence and spatial distribution of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NBFRs) in seawater and surficial sediment samples (N = 19 and 45, respectively) from the South China Sea (SCS) in 2018 were investigated, and the correlation between BFRs and site parameters (total organic carbon, depth, etc.) were assessed by principal component analysis. The concentration ranges of ΣPBDEs in seawater and sediments were 0.90-4.40 ng/L and 0.52-22.67 ng/g dry weight (dw), respectively, while those of ΣNBFRs were 0.49-37.42 ng/L and 0.78-82.29 ng/g dw, respectively. BDE-209 and decabromodiphenyl ethane were the predominant BFRs, accounting for 38.65% and 36.94% in seawater and 26.71% and 68.42% in sediments, respectively. Notably, tris(2,3-dibromopropyl)isocyanurate and 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine, seldomly detected in aquatic matrices worldwide, were detected for the first time in the study area, and their relatively high levels and detection frequencies indicate the ubiquitous application of these NBFRs in the Pearl River Delta. Zhuhai and Jiangmen are the main sources of NBFRs in the SCS. Preliminary risk assessment on NBFRs using hazard quotient indicates low to medium risks to marine organisms at some sites. The occurrence of NBFRs in the SCS highlights the prioritization of more toxicological information on these compounds.

Developing interim water quality criteria for emerging chemicals of concern for protecting marine life in the Greater Bay Area of South China.

This study aimed to establish marine water quality criteria (MWQC) for emerging chemicals of concern (ECCs) for protecting aquatic life in the Greater Bay Area (GBA) of South China. Despite the frequent occurrence and elevated concentrations of these ECCs in the GBA, there is a lack of regional MWQC for these contaminants. We screened 21 common ECCs that were classified into the following six groups: (1) new persistent organic contaminants; (2) brominated flame retardants; (3) perfluoroalkyl and polyfluoroalkyl substances; (4) pharmaceutically active compounds (PhACs); (5) plasticizers; and (6) personal care products. Globally, MWQC for PhACs remain largely unavailable despite their increasing occurrence in marine environments. Using an integrative scientific approach, we derived interim MWQC for the GBA with specific protection goals. The approach described herein can be applied for the derivation of MWQC for ECCs and the establishment of guidelines for ecological risk assessment in the GBA and other regions.

Intra-day microplastic variations in wastewater: A case study of a sewage treatment plant in Hong Kong.

Wastewater treatment plants (WWTPs) in coastal region play a primary role in transferring microplastics into the marine environment. Wastewater is closely related to anthropogenic activities, thus the intra-day variation of abundance of microplastics in the influent should be large and could have significant impact on their estimation of the daily mass load. In this study, a 2-hour interval sampling campaign was conducted at a secondary WWTP in Hong Kong to investigate the intra-day variations and daily loads of microplastics in influent. Results show that the average microplastic abundances increased from 7.1 ± 6.0 to 12.8 ± 5.8 particles/L over time, with predominant particle sizes ranging 1-5 mm. Approximately 80% of the microplastics in samples collected from 9:30-15:00 were polyethylene and polyester, while most samples collected at 17:00 were polypropylene and polyurethane. Microplastic loads exhibited large intra-day variations ranging 6.60 × 108-1.16 × 109 particles/day, indicating that calculated daily microplastic loads based on a specific sampling period may inaccurately estimate the actual daily load.

Enantiomer-specific bioaccumulation and distribution of chiral pharmaceuticals in a subtropical marine food web.

There is a growing concern about the occurrence of chiral pharmaceuticals in the aquatic environment. However, trophic transfer of pharmaceutical enantiomers in marine organisms is still largely unknown. This study assessed the bioaccumulation and spatial distribution of four frequently detected pharmaceuticals - atenolol, metoprolol, venlafaxine, and chloramphenicol, in a subtropical marine food web in Hong Kong waters. Twenty-four species were analyzed, including mollusks, crustaceans, and fishes. Special focus was placed in the chirality of the four analytes comprising ten different stereoisomers. Results showed that mean concentrations of individual pharmaceuticals ranged from <0.03 to 5.88 ng/g wet weight, and invertebrates generally had higher concentrations than fishes. Organisms from Hong Kong western waters were likely more contaminated by the studied pharmaceuticals than those from southern and eastern waters. Trophic dilution was observed for atenolol and chloramphenicol, with trophic magnification factors of 0.164 and 0.517, respectively. R-(+)-atenolol, S-(-)-metoprolol, and R-(-)-venlafaxine were selectively accumulated in fishes, and stereoisomeric impurities of chloramphenicol, i.e., enantiomers apart from R,R-para-form, were widespread in the investigated species. Under the worst-case scenario, atenolol and metoprolol in collected fishes might exceed toxic threshold, while local adults were unlikely to experience health risks from pharmaceutical exposure via seafood consumption.

Occurrence of disinfection by-products in sewage treatment plants and the marine environment in Hong Kong.

Disinfection byproducts (DBPs) are generated by disinfectants reacting with organic matters. Previous studies have focused on DBPs in drinking water, but they have not paid sufficient attention to DBPs in sewage treatment plants (STPs), where the sources and compositions of DBPs are much more complicated, and there is a likelihood of more toxic DBPs being formed. In this study, the occurrence of DBPs in six STPs in Hong Kong and the potential impact of the effluents from the STPs on the marine environment were investigated. In STPs, the mean concentrations of the total DBPs ranged from 1160 to 17,019 ng/L, 1562 to 20,795 ng/L, and 289 to 1037 ng/L in the influent, effluent, and seawater, respectively. Trihalomethanes, haloacetonitriles, and trihalophenols were the most commonly detected DBPs, whereas hexachloro-1,3-butadiene and halocarbazoles were not detected in the STPs and in the marine environment in Hong Kong. Secondary treatment efficiently removed DBPs and DBP precursors. Regarding disinfection techniques, UV irradiation showed little effect on the concentrations of DBPs, whereas sodium hypochlorite significantly elevated the levels of both traditional and emerging DBPs. The effluents from two selected STPs that use chlorination have an obvious impact on the marine environment. This work presents the potential sources of DBPs in sewage, the influence of the treatment processes and disinfection techniques employed in STPs on the removal/formation of DBPs, and the impact of the effluents from the STPs on the marine environment. This work also highlights the need for investigating the emerging DBPs generated in STPs and their related environmental concerns.