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To investigate the distribution, sources, influencing factors, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in East China Marginal Seas (ECMSs) sediments, we measured the concentrations of 16 PAHs in 104 surface sediment samples collected from the ECMSs in 2014 and 2016. Total PAH concentration (∑PAHs) ranged from 4.49 to 163.66 ng/g dry weight (dry w), with 65.98 ± 33.00 (mean ± SD) ng/g dry w. The highest PAH concentrations and total organic carbon were observed in areas with fine-grained sediments in the Bohai Sea (BS), Yellow Sea (YS), and coastal East China Sea (ECS), indicating the prominent influence of regional hydrodynamics and sediment properties. The dominant PAH congener in BS and YS was BbF, whereas coastal ECS was Phe. The heterogeneity of PAH sources implies that terrestrial PAH input and shelf mud deposition have crucial roles in the source–sink processes of PAHs in a strongly human-influenced marginal sea. • Distribution and sources of PAHs in sediments of the ECMSs were explored. • The dominant PAH congener in BS and YS was BbF, whereas coastal ECS was Phe. • Sink of PAHs in the BS and YS was mainly influenced by the atmospheric deposition. • Input of Yangtze River significantly affected occurrence of PAHs in the coastal ECS. [ABSTRACT FROM AUTHOR]

Abstract 75 paired TSP and PM 2.5 samples were collected over four seasons on Huaniao Island (HNI), an island that lies downwind of continental pollutants emitted from mainland China to the East China Sea (ECS). These samples were analyzed for organic carbon (OC) and elemental carbon (EC), with a special focus on char-EC (char) and soot-EC (soot), to understand their sources, and the scale and extent of pollution and dry deposition over the coastal ECS. The results showed that char concentrations in PM 2.5 and TSP averaged from 0.13 to 1.01 and 0.31–1.44 μg m−3; while for soot, they were from 0.03 to 0.21 and 0.16–0.56 μg m−3, respectively. 69.0% of the char and 36.4% of the soot were present in PM 2.5. The char showed apparent seasonal variations, with highest concentrations in winter and lowest in summer; while soot displayed maximum concentrations in fall and minimum in summer. The char/soot ratios in PM 2.5 averaged from 3.29 to 17.22; while for TSP, they were from 1.20 to 7.07. Both of the ratios in PM 2.5 and TSP were highest in winter and lowest in fall. Comparisons of seasonal variations in OC/EC and char/soot ratios confirmed that char/soot may be a more effective indicator of carbonaceous aerosol source identification than OC/EC. Annual average atmospheric dry deposition fluxes of OC and EC into ECS were estimated to be 229 and 107 μg m−2 d−1, respectively, and their deposition fluxes significantly increased during episodes. It was estimated that the loadings of OC + EC and EC accounted for 1.3% and 4.1% of the total organic carbon and EC in ECS surface sediments, respectively, implying a relatively small contribution of OC and EC dry deposition to organic carbon burial. This finding also indicates a possibly more important contribution of wet deposition to organic carbon burial in sediments of ECS, and this factor should be considered for future study. Graphical abstract Image 1 Highlights • PM 2.5 contained approximately 69% of char and 36% of soot, respectively, in TSP. • Char/soot may be a more effective indicator of carbonaceous aerosol source identification than OC/EC. • Dry depositions of OC + EC and EC accounted for 1.3% and 4.1% of their burial in ECS surface sediments, respectively. [ABSTRACT FROM AUTHOR]

The production and use of intentionally-produced polychlorinated biphenyls (PCBs) in China have a short history compared with countries of North America and Europe, where technical PCB mixtures were manufactured in large amounts for decades before being banned. Unintentionally-produced PCB emissions increased dramatically in China, leading to unique profiles of PCB burdens. This study first time evaluated 208 individual PCB congeners at 94 sites from surface sediments of the East China Marginal Seas (ECMSs) and explored their sources. Non-technical PCBs transported from atmospheric transport and river discharge played a dominant role in most areas of the ECMSs, while historical residuals of technical PCBs occupied the fine-grained sediments in muddy areas of the central Yellow Sea (YS), regarding to the low sedimentation rate in the central YS. Furthermore, emissions from Taizhou located on the coast of the East China Sea (ECS), which is an important electronic waste dismantling site in East China, contributed additional technical PCBs to the inner shelf of the ECS. Our results indicate that non-technical PCBs have become the dominant PCB species in the ECMSs, and emphasize the synergistic effects of large riverine input, long-range atmospheric transport, and muddy shelf deposition on PCB source and sink of in marginal seas. [Display omitted] • Non-technical PCBs dominate the total PCB burden in the ECMSs sediments. • Non-technical PCBs comprise 76% of PCBs from riverine and atmospheric inputs. • Technical PCBs are concentrated in central sea areas and e-waste recycling sites. • Atmospheric deposition controls the PCB concentrations in the YS and BS. • River discharge and e-waste emissions regulate the PCB concentrations in the ECS. [ABSTRACT FROM AUTHOR]

Abstract: In the past decades, China has experienced substantial economic growth and industrialization. However, the effects of vast development of China on Hg input to the nearby oceans are still unclear. In this study, the influx and isotopic compositions of Hg in four 210Pb‐dated sediment cores were examined to investigate changes in Hg deposition to the marginal seas off China over a century. Nearshore cores had higher Hg influxes than offshore cores. Increases of Hg influxes started since the 1950s, which coincides with China's economic development. Dramatic historical changes in Hg isotopic composition were observed in the cores (δ202Hg: −2.01‰ to −0.69‰; Δ199Hg: −0.16‰ to 0.31‰; n = 106). δ202Hg increased from the deep to the surface layers of the cores. The offshore cores mainly showed positive Δ199Hg values, but the pre‐1950 samples had more positive Δ199Hg values than the younger samples. The nearshore cores mainly showed negative Δ199Hg values in the pre‐1950s samples, but the younger samples showed Δ199Hg values close to zero. A triple‐mixing isotope model, used to quantify the contribution of potential Hg inputs (e.g., direct discharge of industrial Hg, soil Hg, and precipitation‐derived Hg), showed clear evidence of enhanced industrial Hg inputs to the ocean margin, but slightly decreased watershed soil Hg inputs in the last few decades. The variations of watershed‐derived Hg were likely caused by the construction of impoundments in major rivers of China. This study demonstrates that mercury inputs to Chinese marginal seas have been largely altered due to the industrialization and economic development of China. [ABSTRACT FROM AUTHOR]

The presence of 14 organophosphate esters (OPEs) in surface sediments from a typical fishing port agglomeration in Dalian, North China was investigated for the first time. Tris(2-ethylhexyl) phosphate (TEHP), triphenylphosphine oxide (TPPO), and tris(2-chloroethyl) phosphate (TCEP) dominated 12 detectable OPEs (∑OPEs), with concentrations ranging widely from 0.56 to 352 ng/g (dry weight basis). The ∑OPE levels in sediments varied significantly across fishing harbors of various grades, and within the same grade, highlighting uneven distribution of OPE sources and inputs to harbors. The first- and second-class fishing harbors had higher geometric mean of ∑OPE contents compared to center and natural harbors, reflecting higher OPE pollution in these areas. Although there were significant correlations among the OPE congeners with high detection frequencies, the composition patterns of sediment OPEs varied considerably among fishing ports. The sediments in the center and first-class harbors had higher abundance of non-chlorinated OPEs (non-Cl-OPEs), suggesting heterogeneity in source strength and pollution characteristics of Cl- and non-Cl-OPEs in fishing ports. The distribution of OPEs in sediments was weakly associated with sediment organic carbon, but not socioeconomic variables, indicating complex controlling factors of their distributions in port sediments. The ecological risks of sediment OPEs were evaluated, and while OPE accumulations ranged broadly (7–684 ng/cm2), exposure hazards were negligible. The sediments in first- and second-class fishing harbors, which had greater OPE accumulation, were identified as reservoirs of OPEs in port aquatic environments. [Display omitted] • TEHP and TCEP dominated non-Cl- and Cl-OPEs in fishing port sediments, respectively. • OPE levels and compositions varied irregularly with fishing port grades. • Sediment organic carbon partially controlled OPE distributions among fishing ports. • The sediments of first- and second-class fishing ports were reservoirs of OPEs. [ABSTRACT FROM AUTHOR]

Black carbon (BC) and persistent organic pollutants (POPs) were analyzed from three sediment cores collected offshore in the East China Marginal Seas. The results showed steadily increasing or stable BC concentrations and fluxes. By contrast, time trends of POPs fluxes were consistent with historical records of commercial production and use in China. Although the POP inventories decreased significantly with increase in offshore distance, the relatively consistent trends for individual POPs in different sea areas confirmed that the main sources are derived from mainland China and that atmospheric input was an important contribution. POPs inventories decreased by 59–91 % during transport from the Yellow Sea to the remote East China Sea and deposition to the sediment. This suggests that the source signal for POPs may be preserved under stable depositional environments, even though only a fraction of those pollutants are buried in open sea sediments. • BC and POPs were analyzed from three sediment cores collected offshore in the ECMSs. • Compared with BC, there was a significant loss of POPs during transport in the water column. • Source signals may be better preserved although only a fraction is buried in the sediment. [ABSTRACT FROM AUTHOR]

The Xiangjiang River (XR), the second largest tributary of the Yangtze River, is mainly located in Hunan province in south-central China. Nineteen surface sediment samples (the top 3-cm layer) collected from XR were analyzed to determine the concentrations, distribution, sources, and ecological risk of organochlorine pesticides (OCPs). The concentrations of OCPs were 3.0-29.8 ng/g (dry weight) with a mean of 12.6 ± 7.7 ng/g. The widely detected compounds included HCHs, DDTs, HCB, and dieldrin. Overall, the dominant OCPs in the sediments were mainly composed of residual and degradation products, e.g., β-HCH with a mean of 42.2 % in HCHs and p, p′-DDE with a mean of 43.5 % in DDTs, implying that OCPs in the sediments had suffered from long-term aging without fresh inputs in XR. However, there was a high proportion of p, p′-DDT to DDTs in three sites, suggesting that there was use of technical DDT from their surrounding areas at present. The ratios of α-HCH/γ-HCH and p, p′-DDD + p, p′-DDE/DDTs increase from the upper reaches to the lower reaches of XR, suggesting sediments enriched with α-HCH and metabolites DDD and DDE during sediment transport process and could be attributed to the transformation of γ-HCH to α-HCH and DDT to DDE or DDD. The assessment of the ecological risk indicates that the OCPs in the sediments of XR have a moderate adverse biological effect on organisms. [ABSTRACT FROM AUTHOR]

Abstract: Forty-two surface sediment samples collected from the southern coastal East China Sea (ECS) were analyzed for organochlorine pesticides (OCPs). The results showed high concentrations of DDTs and parent DDT fractions in the nearshore area, suggesting that there is still a fresh input of these species from non-point sources, probably due to the recent usage of relevant products. However, for HCHs, the high concentrations with elevated β-HCH fraction were focused at the local major river estuaries, indicating that soils-released HCH input was mainly from the major river runoffs. The distribution and composition of OCPs in the coastal ECS could be more prominently controlled by the direct regional inputs rather than the general natural sorption process on particulate organic carbon. DDTs and chlordane are more important for their potential ecotoxicological risk on neighboring benthic community in the nearshore region and the local major river estuaries. [Copyright &y& Elsevier]

Abstract: Recent occurrence, distribution and mass inventories of 16 priority polycyclic aromatic hydrocarbons (PAHs) proposed by USEPA in the south Bohai Sea (BS) were studied based on the analytical data of 71 surface sediment samples. The concentrations of 16 PAHs varied from 37 to 537ngg−1 (dry weight). A clear difference was observed between the coastal Bohai Bay (CBB) and its adjacent BS (ABS) in the distribution and compositions of PAHs. The petrogenic source of phenanthrene in CBB was attributable to the industrial wastewater, fugitive fuel leakages from ships and offshore oil production. Four to six ring PAHs were predominantly from the coal and wood combustions in the whole area. The estimated PAH input to the south BS (43,000km2, 56% of BS in area) was 36.6tonyr−1, indicating that the study area was one of the important reservoirs of PAHs in world. [Copyright &y& Elsevier]

Abstract: The rapid economic development in the Yangtze River Delta (YRD), China in the last three decades has had a significant impact on the environment of the East China Sea (ECS). Lead isotopic compositions of a 210Pb dated sediment core collected from the coastal ECS adjacent to the Yangtze River Estuary were analyzed to track the Pb pollution in the region. The baseline Pb concentration in the coastal ECS sediments before the industrialization in China was 32μgg−1, and the corresponding 206Pb/207Pb ratio was 1.195. The high-resolution profiles of Pb flux and 206Pb/207Pb ratios had close relationships with the economic development and the history of the use of leaded gasoline in China, and they were clearly different from those of most European countries and United States. [Copyright &y& Elsevier]

Polycyclic aromatic hydrocarbons (PAHs) in two 210Pb dated sediment cores from the coastal East China Sea, strongly influenced by the discharge from the Yangtze River, were determined to help to reconstruct the economic development over the past century in East China. The variations in PAH concentrations and fluxes in the sediment cores were primarily due to energy structure change, severe floods and dam construction activities. The impact on PAHs by the river discharge overwhelmed the atmospheric depositions. The profiles of PAH fluxes and concentrations as well as compositions in the cores revealed the transformation from an agricultural economy to an industrial one especially after the 1990s'' in the region. PAHs in the study area were dominated by pyrolytic sources. [Copyright &y& Elsevier]

Large river estuarine-inner shelf systems play an important role in the coastal biogeochemical cycling of heavy metals; however, the source-to-sink of mercury (Hg) in these environments remain poorly understood. In this study, the Hg isotopic composition of surface sediments in the Yangtze River Estuary (YRE) and inner shelf of the East China Sea (ECS) were examined to quantitatively track Hg sources in this region. We detected large spatial variation in δ202Hg (−1.88 to −0.29‰) and Δ199Hg (−0.22 to 0.13‰) in sediments of the YRE-ECS inner shelf. The impact of sediment resuspension and transport from the YRE to the inner shelf of the ECS could have little effect on Hg isotopic composition, and the two regions shared similar Hg isotopic composition. An isotope-based triple mixing model further revealed major contributors to sediment Hg from industrial Hg discharge into water (51.8 ± 24.5%), soil Hg from surface runoff (29.2 ± 17.0%), and precipitation-derived atmospheric deposition Hg (19.1 ± 17.5%). The Hg isotopic compositions of the YRE sediments and other local river estuaries were similar to those of direct industrial Hg discharge, indicating that contaminated riverine discharge was the dominant Hg source for estuarine and adjacent shelf areas. Soil Hg delivered through surface runoff was the primary source of Hg to the coastal areas not near large river estuaries, whereas precipitation-derived atmospheric deposition had a greater influence on offshore sediment Hg content. Industrial Hg discharged to rivers had the highest mean depositional flux (35.0 ± 27.3 ng cm−2 yr−1) and mass inventory (25.6 t yr−1), accounting for 77.4% of the total Hg variance. The findings of this study demonstrate that large rivers such as the Yangtze River can supply substantial amounts of industrial Hg to the estuary and adjacent shelf. Image 1 • Hg isotopic compositions in sediments in the YRE–ECS inner shelf were examined. • Three major Hg contributors to sediments were revealed by an isotope-based mixing model. • Large river industrial Hg discharge was the dominant Hg source in the YRE-ECS inner shelf. Quantitatively tracing the sources of mercury in estuarine-inner shelf sediments of the East China Sea based on Hg isotopic composition. [ABSTRACT FROM AUTHOR]

Four sediment cores were collected along the Yangtze-derived sediment transport pathway in the inner shelf of the East China Sea (ECS) for OCP analysis. The sediment records of HCHs and DDTs in estuarine environment reflected remobilization of chemicals from enhanced soil erosion associated to extreme flood events or large scale land use transformation. The sediment records in the open sea, instead, reflected long-term historical trends of OCP application in the source region. Unlike the so-called mud wedge distribution of sediment, inventories of HCHs and DDTs slightly increased from the mouth of Yangtze River alongshore toward south, suggesting the sediment deposition rate was one of factors on the exposure of chemicals within the inner shelf of the ECS. Re-suspension and transport of the Yangtze-derived sediment and consequent fractionation in grain size and TOC were also responsible for the spatial variation of inventories of catchment derived OCPs in a major repository area of the Yangtze suspended sediment. The total burdens of HCHs and DDTs in the inner shelf of the ECS were 35 tons and 110 tons, respectively. After 1983 (year of the official ban in China), those values were 13 tons and 50 tons, respectively. It appears that the Yangtze still delivers relatively high inputs of DDTs more than 30 years after the official ban. High proportions of DDD + DDE and β-HCH suggested those OCPs mainly originated from historical usage in the catchment recent years. [ABSTRACT FROM AUTHOR]

Abstract: The sources, distribution and fate of sedimentary organic matter (SOM) in the Yellow Sea (YS) were studied based on the datasets of total organic carbon (TOC), total nitrogen (TN), organic carbon isotopic values (δ 13C) and n-alkanes of forty-seven surface sediment samples. The spatial pattern of TOC and TN coincided with that of the sediment grain size, suggesting the hydrodynamic constraints on the accumulation of SOM in the YS. The relatively low TOC/TN ratios with contrasting TN intercept of the regression lines indicate the influence of the sorption of inorganic N in the NYS and a mixture of microorganism-derived N-rich OM pool with the terrigenous N-poor OM for the SYS sediment samples, respectively. The enriched δ 13C could also be partially related to the agriculture inputs due to the enhanced fertilization process in addition to the planktonic-derived OM. Molecular compositions of n-alkanes and principal component analysis (PCA) showed a significant terrigenous contribution for the SOM in the central mud deposits. The observed even carbon preference of the short chain length n-alkanes (C12–C22) reveals the potential contribution of microorganism-derived OM in the YS. Combined lines of evidence of significant terrigenous n-alkanes in the YS suggest that the hydrodynamic forcing plays a key role on the selective dispersal and preferential accumulation of the fluvial terrigenous organic materials. The simplified terrigenous SOM transport pathway to the central mud deposits of the YS was conceptually constructed based on the mixed sediments provenances, hydrodynamic transport and depositional mechanism of the fine-grained sediments in this region. [Copyright &y& Elsevier]

The East China Seas (ECSs) are the receptors of the land-based persistent organic pollutants (POPs), such as polybrominated diphenyl ethers (PBDEs) mainly from China through atmospheric deposition driven by the East Asian winter monsoon and fluvial discharge (e.g., Yangtze River and Yellow River), making the offshore sediments to be a good proxy to reconstruct history of those pollutants in China. In this work, four well-placed sediment cores were extracted from the mud areas in the ECSs, and the 210 Pb-dated cores were analyzed to yield historical concentration profiles of PBDEs in the area. The results showed that there was a persistent increase from 1970s and almost no clear sign in the decline of PBDEs until recently in China. More importantly, there was a faster increase of PBDEs from 1990s in China; while this period was just shown as gradually leveling off or even declining trends in developed countries. The persistently increasing trend of PBDEs in China since 1990s could be largely due to the booming of the manufacturing industry and unexpectedly transfer of PBDE pollution from developed countries to China. Besides, the relative high concentrations and fluxes of PBDEs in the core from coastal ECS located near a well-known electrical/electronic waste (e-waste) recycling area suggests an important contribution of PBDE emissions from recycling centers of e-waste in China. Although efforts in environmental monitoring of PBDE contamination have been substantially increased over the last decade, China is still lagging behind in terms of nationwide regulation of PBDE usage and treatment of disposal PBDE-containing products. [ABSTRACT FROM AUTHOR]

This study provides an extensive depiction of regional scale sedimentary total organic carbon (TOC) sequestration in the Bohai Sea (BS) and Yellow Sea (YS), marginal system of the western Pacific Ocean. The spatial pattern of the sediment mass accumulation rate (MAR) in the BS and YS was summarized based on a 100-year timescale. The relatively higher MAR (3 − 7 g/cm 2 /y) in the Yellow River estuary, compared to the adjacent areas, indicate a predominant impact of river discharge on the modern sedimentation process in the BS. Relatively stable sedimentary environment in the offshore mud deposits of the BS and YS was also identified based on the along-core sediment composition and radionuclides profiles. The corresponding spatial pattern of grain size and TOC content suggest a hydrodynamic constraint on the sedimentary TOC accumulation. Moreover, in spite of the various TOC sources revealed by the bulk organic matter (OM) proxies (C/N ratio and δ 13 C), the restriction of these bulk parameters with potential masking of the signature of terrigenous OM was also identified. The average burial flux of TOC (15.3 g C/m 2 /y) was finally obtained with a total sequestration of 5.6 × 10 6 t C/y, suggesting that the BS and YS serve as a significant repository of sedimentary TOC. The overall organic carbon storage capacity of the BS and YS is mainly sustained by the fluvial/land-based OM input, high phytoplankton primary productivity, convergent hydrodynamic and stable depositional settings. [ABSTRACT FROM AUTHOR]

Abstract: The in situ records of a cruise in September 1995 off the Huanghe mouth and laboratory measurements indicate that the shear front off the river mouth results from the phase difference between the nearshore and offshore tides and plays significant role in the river-laden sediment dispersal. Two types of shear front, identified from the behaviors of currents inside and outside the shear front, alternate over tidal cycle, each of which lasts for ∼2–3h. The dispersal patterns of suspended sediment at the stations inside and outside the shear front are distinctly different from each other. In addition, the gravity-driven hyperpycnal flow generated near the mouth is terminated within shallow water due to the barrier effect of shear front. A dispersal pattern of river-laden suspended sediment in the shear frontal zone is proposed to interpret the difference of sediment transport inside and outside the shear front. The fresh and highly turbid river effluents discharge to the sea during ebb tides and are transported northwestwards inside the shear front under the combined impacts of northward ebb currents, down-slope transport of hyperpycnal flow and confining action of shear front; after partially mixing with the ambient seawater the river effluents are then transported southeastwards outside the shear front along the flood currents, causing the intermittent increase in suspended sediment concentration and corresponding decrease in salinity outside the shear front. Over annual time scale the subaqueous slope has a geomorphological response to the ephemeral shear front. Most of the river-laden sediment deposit inside the shear front with a high accumulation rate, while erosion is dominant outside the shear front due to the lack of sediment supply. [Copyright &y& Elsevier]

Mercury (Hg), Lead (Pb) and its stable isotopes and polycyclic aromatic hydrocarbons (PAHs) were analyzed in a sediment box core obtained from the central Bohai Sea (BS) of northern China to trace anthropogenic input for the past century. The records of Hg, PAHs and Pb isotopic ratios revealed that the BS was clearly impacted by human activities from the early 1930s to the middle 1940s, possibly related to the acceleration of heavy industrialization in northeast China. Under rapid development and significant increase in fossil fuel consumption, pressure on the BS environment had obviously increased, as revealed by increasing concentrations of Hg, Pb, and PAHs from the early 1960s to late 1990s, with a synchronous decrease of 206Pb/207Pb isotopic ratios. The evolving trends in 206Pb/207Pb ratio, Hg, and PAHs were found to be decoupled since the early 2000s, possibly because of the significant improvement in environmental protection. Depositional records of Pb isotopic ratios with PAH compositions indicate a high-resolution sediment footprint of anthropogenic energy-consumption-based impacts around the BS over the past century, especially with the transformed emission sources from the leaded gasoline and combustion of coal before the 2000s to coal combustion and nonferrous metal smelting thereafter. The decreased records of sedimentary Pb have been widely found by around the world (e.g. North America, Southeast Asia and West Europe) after the ban on the leaded gasoline. However, this trend in China is reverse by the phasing out of leaded gasoline since the 2000s, possibly due to the recent accelerating development of nonferrous metal smelting and the continued increase in coal-dominated energy consumption. • High-resolution sediment records of recent anthropogenic impacts in Bohai were obtained. • Impact of heavy industry in Northeast China during 1930s was firstly recorded in Bohai sediment. • Transformation of Pb emission sources from leaded gasoline to coal and metal smelting was recorded at the 2000s. • Coupled deposition records of Pb and PAHs could serve as a coastal sediment footprint of human impact. [ABSTRACT FROM AUTHOR]

We reconstructed the history of the inputs of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) into the marine environment to reveal the time-dependent influence of sources and associated anthropogenic activities in China, based on 210Pb-dated cores from the East China marginal seas (ECMS). The temporal dynamics of pesticide contamination expresses as deposition fluxes, inventories, and half-life estimations varied among the cores, suggesting heterogeneity in transport pathways of pollutants. The depth profiles of pesticide inputs closely followed their historical production and application timelines in China, and were also affected by human activities in catchments, with general declines in HCH and DDT inputs to the coring sites after their peak deposition. Despite the prevalence of occurrence of weathered HCH/DDT in the cores, there were clear source-dependent differences in isomeric composition and accumulation between before and after these pesticides were banned. α -HCH and p , p ′-DDT were relatively more enriched in sediments from the pre-ban period when heavy technical HCHs and DDTs use occurred, as indicated by the higher α -/ β -HCH and lower (DDE + DDD)/DDTs ratios, and the larger fractions of α -HCH and p , p ′-DDT influxes to the coring sites in the ΣHCH and ΣDDT fluxes, respectively, while this pattern shifted to be historical residue-based in the post-ban period. The difference in the recent influxes of pesticides to core sediments and their higher post-ban inventories highlight the increasing importance of historical sources over time and continuous input of weathered residues into marine environment via lateral transport. Image 1 • Dynamics of deposited HCHs and DDTs in the ECMS were related to input pathways. • Compositions and accumulations of pesticides varied with time-dependent sources. • Weathered HCHs and DDTs dominated their current inputs to the ECMS. • Importance of lateral transport of residual pesticides into the ECMS is rising. [ABSTRACT FROM AUTHOR]