Critical reassessment of microplastic abundances in the marine environment.

Microplastics (MPs) pose a growing concern in the marine environment, but their global prevalence remains largely unknown due to the absence of precise and standardized detection methods. This review critically evaluates existing techniques for quantifying MP abundances in marine field studies, addressing inaccuracies resulting from the exclusion of particle sizes, polymer types, or limitations in identification methods. These traced inaccuracies were considered to recalculate MP abundances for particle sizes from 10 to 5000 µm, providing the first corrected global overview of MP distribution that enables quality assessment and reliable comparisons between adjusted data. The recalculations indicate that MP abundances are up to 15 times higher in marine waters (average (1.5 ± 36.2) × 105 items m-3) and up to 11 times higher in the marine sediments (average (2.7 ± 117.9) × 105 items kg-1) than previously reported in the literature. The Australasian Mediterranean Sea (average (1.2 ± 10.6) × 106 items m-3) and the North Atlantic (average (2.1 ± 37.6) × 105 items kg-1) emerged as the most polluted regions in marine waters and sediments, respectively, with primary contributors being the coasts of Southeast Asia and East America. This review demonstrates that previous field studies, global estimates, and models have significantly underestimated MP levels in marine environments in many cases, which could result in misinterpretations of both local and global pollution levels. This work highlights the critical need for precise handling of microplastic samples and urges future researchers to adopt standardized protocols for MP analysis to avoid inaccurate and misleading outcomes.

Microplastic Particles and Fibers in Seasonal Ice of the Northern Baltic Sea.

Microplastic pollution is a pervasive issue, with remarkably high concentrations observed even in the most remote locations such as Arctic sea ice and snow. The reason for such large microplastic abundances in sea ice is still speculative and applies mainly to saline or freshwater conditions. In this study, we investigated seasonal ice core samples collected in March 2021 from the northern Baltic Sea (Gulf of Bothnia) for their microplastic distributions. The Baltic Sea is characterized by low salinity and can be ice-covered for up to six months annually. Microplastics were analyzed in the melted ice samples using an adsorption technique and Raman microscopy to identify their abundances, colors, shapes, and sizes to calculate their masses. Due to the strong dynamic of the ice layer and the repeated melting and freezing processes during the ice formation, no discernible trends in microplastic abundances, masses, or polymer types were observed throughout the ice core length. The average microplastic abundance (±SD) in the Baltic Sea ice was determined to be 22.3 ± 8.6 N L-1, with 64.9% of the particles exhibiting a particulate shape and 35.1% having a fibrous shape. The most prevalent polymer type was polyethylene terephthalate (PET), accounting for 44.4% of all polymers. This is likely due to the high proportion of PET fibers (93.8%). The majority of particle-shaped microplastics were identified as polyethylene (PE; 37.2%), followed by PET (17.2%), polyvinyl chloride (PVC; 15.9%), and polypropylene (PP; 15.9%). No correlations were found between microplastic concentrations and proximity to land, cities, industries, or rivers, except for PP mass concentrations and particle sizes, which correlated with distances to industries in Luleå, Sweden.

A Global Inventory of Natural and Synthetic Estrogens in Aquatic Systems.

Estrogens are a group of endocrine disruptors that are recognized as a threat to the world's ecosystems and are easily transported through aquatic systems from mainly anthropogenic sources. To illustrate this growing problem, we have compiled a global overview of measured concentrations of natural and synthetic estrogens restricted to freshwater systems (lakes, rivers, and lagoons) and marine coastal and open ocean environments, focusing on estrone (E1), 17$\upbeta$-estradiol (E2), estriol (E3), and 17$\upalpha$-ethinylestradiol (EE2). We found that the cumulative risk quotient is high at 65% of 400 sampled sites, highlighting that estrogen pollution is a major environmental concern. Our investigation revealed that almost no information is available on the concentration levels of E1, E2, E3, and EE2 for the open ocean areas. However, their occurrence in all systems, including open seas, suggests that estrogens are not completely degraded during transport to and within the environment and may be more persistent than previously thought.

Air-Sea Exchange and Atmospheric Deposition of Phthalate Esters in the South China Sea.

Phthalate esters (PAEs) have been investigated in paired air and seawater samples collected onboard the research vessel SONNE in the South China Sea in the summer of 2019. The concentrations of ∑7PAEs ranged from 2.84 to 24.3 ng/m3 with a mean of 9.67 ± 5.86 ng/m3 in air and from 0.96 to 8.35 ng/L with a mean of 3.05 ng/L in seawater. Net air-to-seawater deposition dominated air-sea exchange fluxes of DiBP, DnBP, DMP, and DEP, while strong water-to-air volatilization was estimated for bis(2-ethylhexyl) phthalate (DEHP). The estimated net atmospheric depositions were 3740 t/y for the sum of DMP, DEP, DiBP, and DnBP, but DEHP volatilized from seawater to air with an average of 900 t/y. The seasonally changing monsoon circulation, currents, and cyclones occurring in the Pacific can significantly influence the concentration of PAEs, and alter the direction and magnitude of air-sea exchange and particle deposition fluxes. Consequently, the dynamic air-sea exchange process may drive the transport of PAEs from marginal seas and estuaries toward remote marine environments, which can play an important role in the environmental transport and cycling of PAEs in the global ocean.

Changes of dissolved organic matter following salinity invasion in different seasons in a nitrogen rich tidal reach.

Dissolved organic matter (DOM) is a heterogeneous mixture of dissolved material found ubiquitously in aquatic systems and dissolved organic nitrogen is one of its most important components. We hypothesised nitrogen species and salinity intrusions affect the DOM changes. Here, using the nitrogen rich Minjiang River as an easily accessible natural laboratory 3 field surveys with 9 sampling sites (S1-S9) were conducted in November 2018, April and August 2019. The excitation emission matrices (EEMs) of DOM were explored with parallel factor (PARAFAC) and cosine-histogram similarity analysis. Four indices including fluorescence index (FI), biological index (BIX), humification index (HIX) and the fluorescent DOM (FDOM) were calculated and the impact of physicochemical properties was assessed. The results suggested that the highest salinities of 6.15, 2.98 and 10.10, during each campaign corresponded to DTN concentrations of 119.29-240.71, 149.12-262.42 and 88.27-155.29 µmol·L-1, respectively. PARAFAC analysis revealed the presence of tyrosine-like proteins (C1), tryptophan-like proteins or a combination of the peak N and tryptophan-like fluorophore (C2) and the humic-like material (C3). The EEMs in the upstream reach (i.e. S1-S3) were complex with larger spectra ranges, higher intensities and similar similarity. Subsequently, the fluorescence intensity of three components decreased significantly with low similarity of EEMs (i.e. S4-S7). At the downstream, the fluorescence levels dispersed significantly and no obvious peaks were seen except in August. In addition, FI and HIX increased, while BIX and FDOM decreased from upstream to downstream. The salinity positively correlated with FI and HIX, and negatively related to BIX and FDOM. Besides, the elevated DTN had a significant effect on the DOM fluorescence indices. Altogether, salinity intrusion and elevated nitrogen are relevant for the distribution of the DOM, which is helpful for the water management tracing the DOM source according to the on-line monitoring of salinity and nitrogen in estuaries.

The biogeography and co-occurrence network patterns of bacteria and microeukaryotes in the estuarine and coastal waters.

Community and diversity shifts of bacteria and microeukaryotes with strong environmental and spatial variations have been unveiled in the Pearl River Estuary (PRE) and northern coastal part of South China Sea (SCS). However, it is not clear what the determining factors shape the microbial community and how the biotic interactions respond to the estuarine and oceanic environment. Here, we established the multiple regression models (MRM) and co-occurrence networks on microbial communities in PRE and SCS habitats. The results showed that there were significant differences of the abiotic factors affecting the bacterial and microeukaryotic communities between PRE and SCS habitats. Salinity explained the largest variations to the microbial community dissimilarities in PRE. Whereas spatial and environmental factors determined the microbial community dissimilarities in SCS. Positive relations between parasitic lineages (e.g. Perkinsea and Cercozoa) and algal taxa (Dinophyceae, Cryptophyta, Chlorophyta and Ochrophyta) dominated in the PRE network. While parasites Syndiniales positively correlated with other Syndiniales and protists in SCS. Strong positive associations among autotrophic and heterotrophic groups were revealed in both niches. Therefore, the biotic interactions are also important and may be responsible for the unexplained variations of the abiotic factors from MRM models. Microbial network in the PRE estuarine water had weakened resistance to environmental disturbances, while the SCS network had greater capacity to maintain network stability. This study shed light on the different mechanisms of abiotic and biotic factors in shaping the compositions of bacteria and microeukaryotes between PRE and SCS niches, and highlights the weakening effect of environmental disturbances on the microbial network stability.

Abiotic Long-Term Simulation of Microplastic Weathering Pathways under Different Aqueous Conditions.

Microplastics (MPs) are one of the most abundant and widespread anthropogenic pollutants worldwide. In addition to the global spread and threats of plastic to native species by carrying toxic substances, its slow degradation rate and resulting long retention time in the environment constitute a problem that is still poorly understood. In this study, five of the most manufactured plastic types were weathered under simulated beach conditions for 18 months in freshwater, brackish water, and seawater. Those included polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). PP was the first polymer type that fragmented after 9 months of weathering and influenced the pH of the surrounding water. Molecular surface changes were detected for all polymers, just after the first week. Hydroxyl bonds were one of the first groups incorporated into the polymers, weakening 2-3 weeks later. Carbonyl groups were also measured early, but with significantly different developments with time between the polymer types. Differences in degradation rates were proven between the water media, with the fastest degradation in seawater compared to brackish water and freshwater for PE and PP. These results are consistent with previous findings on MPs aged under environmental conditions and provide initial long-term observations of MP degradation pathways under simulated environmental conditions. These findings are valuable for assessing the fate and hazards of MPs in aquatic systems.

Organophosphate Esters in Air and Seawater of the South China Sea: Spatial Distribution, Transport, and Air-Sea Exchange.

Organophosphate esters (OPEs) have become one group of chemicals with emerging concern in the marine environment. In this work, we investigated OPEs in the air and seawater of the South China Sea in summer 2019. The concentrations of ∑10OPEs in the atmosphere ranged from 66 to 550 pg/m3, with TCIPP, TNBP, TPhP, and TEP predominating in the air. The total dissolved OPE concentrations (∑10OPEs without TEP) measured in high-volume water samples ranged from 300 to 3600 pg/L, with a mean concentration of 1180 ± 910 pg/L. TEP was measured with liquid-liquid extraction (LLE), and it showed the highest concentration (average 2000 ± 1450 pg/L) among the selected OPEs. Total suspended matter associated OPEs accounted for less than 4.7% of the sum of OPE concentrations in seawater. Fugacity fractions and air-sea exchange fluxes showed that TCEP, TCIPP, TIBP, TEHP, TPhP, and EHDPP were favored to volatilize, TEP dominated the deposition, while TPrP and TNBP varied between volatilization and deposition. Atmospheric particle deposition fluxes ranged from 5 to 71 ng/m2/day with an average of 17 ± 15 ng/m2/day. The input of ∑OPEs to the entire South China Sea via atmospheric particle deposition was estimated to be 22 ± 19 tons/year, while the net air-sea exchange fluxes of OPEs were volatilization from seawater to air with an average of 44 ± 33 tons/year. This work suggests that air-sea exchange and atmospheric particle deposition are significant processes interfering with the transport of OPEs in the marine environment.

Biofilm enhances the copper (II) adsorption on microplastic surfaces in coastal seawater: Simultaneous evidence from visualization and quantification.

Microplastics (MPs) exposed to the urban coastal seawater could form biofilms, which facilitate the adsorption and transportation of hazardous contaminants. However, influence of biofilms on the metal adsorption of MPs, especially the co-existence of biofilm and metals on MPs, is still less known. In this study, the adsorption of copper (Cu) on biofilm-coated MPs (BMPs) was visually analyzed and quantified. The results of scanning electron microscopy in combination with energy dispersive X-ray showed that biofilm and metals co-occurred on MPs in seawater. The nanoscale secondary ion mass spectrometry images further exhibited that the distribution of Cu, chlorine (Cl) and biofilm on MP surfaces was highly consistent. Moreover, the adsorption of Cu(II) on BMPs was enhanced as quantified by inductively coupled plasma-mass spectrometer. Furthermore, different species on BMPs with and without Cu were identified, and their potential functions of metal or Cl metabolism were predicted based on KEGG pathway database. Overall, for the first time, this study provides visual and quantified evidences for the enhancement of Cu(II) adsorption on BMPs based on co-localization, and it may shed a light on the development of methodologies for investigating the interaction among MPs, biofilms and pollutants in marine environment.

First long-term evidence of microplastic pollution in the deep subtropical Northeast Atlantic.

No anthropogenic pollutant is more widespread in the aquatic and terrestrial environment than microplastic; however, there are large knowledge gaps regarding its origin, fate, or temporal variations in the oceans. In this study, we analyzed sediment trap material from the deep subtropical Northeast Atlantic (2000 m) in a long-term record (2003-2015) to assess the role of the deep ocean as a potential sink of microplastics. Microplastic particles were identified in all 110 analyzed samples with flux rates of 1.13-3146.81 items d-1 m-2. Calculated microplastic mass fluxes ranged between 0.10 and 1977.96 µg d-1 m-2, representing up to 8% of the particle flux. Between years, the composition of the different polymers changed significantly, dominated by polyethylene, whose amount was correlated with the lithogenic input. The correlation between polyethylene and the lithogenic fraction was attributed to an air transport pathway from northeast Africa and surrounding regions. The second most abundant polymer detected in our study was polyvinyl chloride, which is not correlated with lithogenic or biogenic particle flux fractions. Instead, we observed seasonality for polyvinyl chloride with recurring high fluxes in winter before the plankton bloom and significantly lower amounts in summer. Other polymers identified were polypropylene, polyethylene terephthalate, and lower numbers of polystyrene and polymethyl methacrylate. The average microplastic particle size for all samples and polymers was 88.44 ± 113.46 µm, with polyethylene and polyvinyl chloride having the highest proportion of small particles (<100 µm). Our findings provide first insights into temporal variations of sinking microplastics, which are crucial for understanding the fate of plastic in the oceans.

Structural and Functional Characteristics of Microplastic Associated Biofilms in Response to Temporal Dynamics and Polymer Types.

The colonization of bacterial communities and biofilm formation on microplastics (MPs) have aroused great concern recently. However, the influence of time and polymer types on the structural and functional characteristics of biofilms remains unclear. In this study, three types of MPs (polyethylene, polypropylene, and polystyrene) were exposed for different time periods (10, 20 and 30 days) in seawater using a microcosm experiment. Microscopic spectroscopy and high-throughput gene sequencing techniques were used to reveal the temporal changes of structural and functional characteristics of MPs associated biofilms. The results indicate that the biofilm formation is affected by both the incubation time and the polymer type. In addition, bacterial diversity and community structure in the biofilms show selectivity towards seawater, and tend to shift over time and among different polymer types. Moreover, biofilms are shown to harbor plastic degrading bacteria, leading to the changes of functional groups and surface hydrophobicity, and thereby enhancing the biodegradation of MPs.

Separation of microplastics from mass-limited samples by an effective adsorption technique.

Microplastic in the environment hides visible and invisible dangers for the ecosystems and domiciled organisms. Due to the large quantities of microplastics already distributed worldwide, comparative studies to investigate the associated hazards, distribution patterns, and abundances are becoming increasingly important. Due to varying efforts and budgets, there is still no homogenized detection method for microplastics in the environment, which severely compromises the comparability and reliability of results between previous studies. In this study, we compare the efficacy, degradative effect on microplastics, and microplastic recovery rates of different digestion and separation methods for isolating microplastics from mass-limited environmental samples with high biogenic content. Our results show that the most gentle and effective isolation method is an adsorption-based technique that exploits the lipophilic properties of plastic for separation. This technique achieves an average microplastic recovery rate of 98.0 ± 3.8% and a matrix removal of 96.3 ± 0.3% at low cost and minimum effort. To examine the applicability of this technique to natural environmental samples, eight sediments and two plankton net samples from the South China Sea were selected to determine microplastic abundances. In the analyzed sediment samples, 0-9 microplastic items per 10 g sediment d. w. were found, while 17-25 items per m3 were detected in net samples. Considering the respective mean plastic density, this corresponds to a calculated microplastic mass of 0-39 µg (10 g d.w.)-1 and 3.7-7.1 µg m-3 in sediment and water samples, respectively. This study represents a new way of microplastic extraction from matrix-rich mass-limited samples with high accuracy and easy feasibility at low costs, which would be useful as a worldwide homogenized method in future microplastic research projects and related data comparability.

Occurrence and distribution of estrogenic substances in the northern South China Sea.

Estrogenic substances are today among the contaminants of emerging concern. Besides naturally occurring estrogens, other natural and synthetic substances can mimic a hormonal action due to their structural resemblance to hormones, possibly affecting the endocrine system of living organisms. Estrogens have been detected in inland water bodies such as influents and effluents of waste water treatment plants as well as in rivers, but data on their distribution and variability in the marine ecosystem are still limited. Surface water samples obtained during two research cruises on the northern shelf of the South China Sea (SCS) near the Pearl River Estuary, in September 2018 and in August 2019, were investigated for estrogenic substances, namely estrone (E1), 17ß-estradiol (E2), 17α-ethinylestradiol (EE2), genistein (GEN), daidzein (DAI) and zearalenone (ZEN). Among the target analytes, the natural hormones E1 and E2, as well as the synthetic EE2, were the most abundant with maximum concentrations of 1.1 ng L-1, 0.7 ng L-1 and 0.6 ng L-1, respectively. Of substances produced by plants and fungi, GEN, DAI and ZEN, only GEN was detected (1.2 ng L-1). High concentrations occurred predominantly close to the coast, which was also reflected in the calculated estradiol equivalent quotients (up to 1.4 ng L-1). In general, the distribution of estrogenic substances observed in both years shows a regional and inter-annual variability consistent with the modeled surface current data for the SCS. Regarding single estrogenic compounds and estradiol equivalents, marine organisms in the northern SCS might be exposed to high potential risk.

Abundance and characteristics of microfibers detected in sediment trap material from the deep subtropical North Atlantic Ocean.

Plastics and microplastics increasingly gain importance due to their perils and wide distribution in the marine environment. Microfibers account for the largest percentage of anthropogenic-induced microparticles, which inter alia, consist of plastic, and are found in deep-sea sediments. However, the sinking of fibers from the surface through the water column to the seafloor is still poorly understood. The present study investigates microfibers extracted from sediment trap samples, which were deployed in the North Atlantic Subtropical Gyre (NASG). The average result of eleven analyzed samples showed 913 microfibers per gram of collected particle flux material, with a predominant fiber length shorter than 1 mm (75.6%) and a distribution maximum between 0.2 and 0.4 mm. Further, the average number of microfibers found in this study was used to derive microfiber fluxes for the NASG based on the deployment time of the sediment trap. Extrapolating the computed flux of 94 microfibers m-2 day-1 to the entire NASG area would correspond to a total microfiber mass flux of 9800 t a-1 or 73 × 1013 microfibers a-1 of sinking microfibers through the water column. These findings offer an extended application of sediment traps to monitor microfiber fluxes, which reveals the opportunity to investigate the mechanism driving sinking of microfibers and microplastics into the deep open ocean.

Biofilm formation and its influences on the properties of microplastics as affected by exposure time and depth in the seawater.

The effects of microbial colonization and biofilm formation on microplastics in the marine and coastal environments have aroused global concern recently. However, the simultaneous influences of exposure time and depth on biofilm formation, and subsequently on the properties variations of microplastics is less studied. In this study, polyethylene (PE) film was exposed at three depths (2 m, 6 m, and 12 m) for three time periods (30 days, 75 days, and 135 days) in the coastal seawater of Yellow Sea, China. The results show that the total amount of biofilms markedly increased with exposure time, but decreased with water depth. Typical morphologies and compositions of biofilms such as coccus-, rod-, disc-shaped bacteria and filaments, as well as a dense layer of extracellular polymeric substances were observed on the surfaces of the PE microplastics. Biofilm formation could decrease the hydrophobicity of PE microplastics, and increase the abundances of hydrophilic C-O and CO groups on the surface of PE. Alphaproteobacteria, Gammaproteobacteria and Bacteroidia were identified as the core microbiome of the PE associated biofilms, while the dominant bacteria families vary from the early to the late phases of the biofilm formation. Our results indicate that microplastics associated biofilms could affect the environmental processes and fates of microplastics in the marine and coastal environment.

Characteristics and distribution of microplastics in the coastal mangrove sediments of China.

Mangroves are a unique and important type of coastal wetlands in the tropical and subtropical zones worldwide. The abundance and spatial distribution of microplastics in the mangrove sediments however are still poorly understood. The present study aimed to illustrate the characteristics, abundance and spatial distribution of microplastics in different mangrove sediments along the south-eastern coastal zones of China. Microplastic samples (roughly 10-20 kg fresh sediments at each site) taken from 21 sampling sites showed various shapes, colors, composition, sizes, surface morphology, abundance and strong spatial heterogeneity. Five different shapes of microplastics with a variety of colors were detected in the mangrove sediments, among which foams (74.6%) and fibers (14.0%) were the dominant types. The polymer composition of the microplastics identified based on the FT-IR and µ-FTIR covered polystyrene (75.2%), polypropylene (11.7%), rayon (4.6%), polyester (3.4%), polyethylene (2.8%) and acrylic (2.4%). The observed microplastics with a size range of less than 2 mm made up 58.6% of the total microplastic particles. The microplastics had various surface morphologies, exhibiting complicated weathered surfaces. The abundance of microplastics showed a substantial variation among the sampling sites, ranging from 8.3 to 5738.3 items kg-1 (dry sediment). Altogether, our study provides a better understanding of microplastic pollution status and prevention policy-making of mangrove habitats in China.

Patterns of estrogenic activity in the Baltic Sea.

Compounds such as estradiol and ethinylestradiol belong to contaminants of emerging concern, as they can disrupt the endocrine system of an organism with a hormonal system. The determination of such compounds is still challenging due to required low detection and quantification limits. Bioassays have proved to be sensitive tools for investigating the full potential of all compounds that can elicit an estrogenic response. In this study, surface water samples from different sampling sites and seasons in the Baltic Sea were analyzed for estrogenic activity with the Arxula adeninivorans yeast estrogen screen. Observed estradiol equivalent concentrations were in the range of

Phylogenetic analysis and yessotoxin profiles of Gonyaulax spinifera cultures from the Benguela Current upwelling system.

The Benguela Current in the Atlantic is one of the four major upwelling systems on the Eastern boundary of the world ocean. Thus the coastal regions off Namibia are prone to high primary productivity that can lead to Harmful Algae Blooms as this nutrient rich water reaches the euphotic zone. Yessotoxins (YTXs) produced by G. spinifera were detected in Namibian phytoplankton field samples in 2011. Isolation of G. spinifera cultures from this location in 2012 enabled molecular genetics work and further liquid chromatography-mass spectrometry assessment of toxin profiles. The molecular work grouped the Benguela G. spinifera with other toxic G. spinifera strains originating from Italy and New Zealand. The main YTX analogs present in the Benguela G. spinifera are homo-YTX, YTX and a hydroxylated analogue. This work adds important knowledge on the occurrence of Harmful Algae Blooms in this region and is of relevance for safety.

Sinking velocity of sub-millimeter microplastic.

Sinking experiments were conducted using irregularly shaped polyamide (PA), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET) particles sized 6 to 251 µm. Certified PS spheres were used to validate experiments and showed that the effect of particle size on terminal sinking velocity is well reproduced by the method. As expected sinking velocities of irregularly shaped particles were considerably lower than theoretical values for spheres of the same size range calculated via several approximations available in the literature. Despite the influence of particle shape, the dependence of terminal sinking velocity on particle size can reasonably well be described by a quadratic linear regression, with an average determination of 63%. To generalize results we present a model that predicts terminal sinking velocity as a function of particle size and particle excess density over the fluid. Improving the predictive power of this model requires further experiments with a range of particle characteristics.

Polycyclic and organochlorine hydrocarbons in sediments of the northern South China Sea.

We investigated the concentration distribution and composition of organic pollutants in sediments of the shelf and the deep northern South China Sea (NSCS). Concentrations of polycyclic aromatic hydrocarbons (Σ15PAH; 10.69-66.45 ng g-1), Dichlorodiphenyltrichloroethane (Σ4DDT; 0-0.82 ng g-1), and polychlorinated biphenyls (Σ24PCB; 0-0.12 ng g-1) are below established sediment quality guidelines, suggesting no environmental risk. Surprisingly, concentrations increase from the shelf to the deep NSCS, and are higher in the east of the study area. The organic pollutant composition indicates PAH mainly derived from pyrogenic sources, and mostly degraded DDT and PCB. However, in the deep NSCS, considerable contribution of petrogenic PAH, low chlorinated PCB and p,p'-DDT suggest more recent input from different sources compared to the shelf. From these results we infer that organic pollution in the NSCS does not originate from the Pearl River Estuary but from the NE SCS, SW of Taiwan.