Air-Seawater Exchange of Organochlorine Pesticides along the Sediment Plume of a Large Contaminated River

Operating pesticide use reduction within the boundary of food security in peri-urban settings

Pesticide use in peri-urban areas affects the urban environment and public health, and reducing the use may present food security issues for urban dwellers. In this study, we explore how a municipality-adopted goal of a 20% reduction in pesticide use could be achieved, along with local food security and environmental implications, for Shanghai located in the densely populated East China. A regional Shanghai Agricultural Sector Model incorporating district- and technology-varying crop budgets, was developed to simulate the effects of pesticide reduction policy. Here we find that achieving the reduction goal had the largest implications in districts with high pesticide use totals and intensities, potentially reducing pesticide non-point source pollution in the Yangtze River Estuary and Dianshan Lake; the production levels of rice and leafy vegetables would be most affected; and adopting machinery that allows more precise pesticide application modulates these results. Moreover, imposing the requirements at the district-level caused more severe local food security concerns, and less environmental benefits. Furthermore, a closed Shanghai's agricultural economy would substantially enlarge the regional heterogeneity in the above-mentioned outcomes. Exploring the effects of a quantity control policy on current-use pesticides at different aggregation levels has important implications for regulating the use of agrochemicals.

Legacy and emerging persistent organic pollutants in the marginal seas of China: Occurrence and phase partitioning

Emerging per-and polyfluoroalkyl substances (PFASs) and traditional organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs) in the marginal seas of China were analyzed to study the occurrence, transport and phase partitioning. The influence of organic carbon (OC) and element carbon (EC) on particulate emerging pollutants in seawater was studied for the first time. The concentrations of PFASs, OCPs and PAHs in the seawater (dissolved phase plus particulate phase) ranged from 1.4 to 8.6, 0.76 to 4.3 and 8.4 to 130 ng L^-1, respectively. Pollutants in the northern East China Sea were generally higher than that in the southern East China Sea and South China Sea, which may be attribute to river discharges and land sources in the Yangtze River Delta. The Yellow Sea Coastal Current and Yangtze River Dilute Water drove the transport of contaminants from north to south marginal seas. Positive correlations between EC and PAHs were found, which can be explained by co-emission of them during combustion. Moreover, positive correlations between OC, EC and Log K_d for BkF, BeP, HCB, 6:2 FTSA were found, which demonstrated that OC and EC promoted the partitioning of these high oleophilic compounds to suspended particle.

Pesticides in the atmosphere and seawater in a transect study from the Western Pacific to the Southern Ocean: The importance of continental discharges and air-seawater exchange

The global oceans are known as terminal sink or secondary source for diffusive emission of organochlorine pesticides (OCPs) and selected current used pesticides (CUPs) into the overlaying atmosphere. Many pesticides have been widely produced worldwide, subsequently applied, and released into the environment. However, information on the occurrence patterns, spatial variability, and air-seawater exchange of pesticides is limited to easily accessible regions and, hence, only few studies are reported from the remote Southern Ocean. To fill this information gap, a large-scale ship-based sampling campaign was conducted. In the samples from this campaign, we measured concentrations of 221 pesticides. Both gaseous and aqueous samples were collected along a sampling transect from the western Pacific to the Southern Ocean (19.75° N-76.16° S) from November 2018 to March 2019. Twenty-seven individual pesticides were frequently (≥ 50%) detected in gaseous and aqueous samples. Tebuconazole, diphenylamine, myclobutanil, and hexachlorobenzene (HCB) dominated the composition profile in both phases. Spatial trends analysis in atmospheric and seawater concentrations showed a substantial level reduction from the western Pacific towards the Southern Ocean. Back-trajectory analysis showed that atmospheric pesticide concentrations were strongly influenced by air masses origins. Continental and riverine inputs are important sources of pesticides in the western Pacific and Indian Oceans. Atmospheric and seawater concentrations for the target pesticide residues in the Southern Ocean are low and evenly distributed due to the large distance from potential pollution sources as well as the effective isolation by the Antarctic Convergence (AC). Air-seawater fugacity ratios and fluxes indicated that the western Pacific and Indian Oceans were secondary sources for most pesticides emitted to the atmosphere, while the Southern Ocean was still considered to be a sink.

Advances in Optical Sensors for Persistent Organic Pollutant Environmental Monitoring

Optical chemical sensors are widely applied in many fields of modern analytical practice, due to their simplicity in preparation and signal acquisition, low costs, and fast response time. Moreover, the construction of most modern optical sensors requires neither wire connections with the detector nor sophisticated and energy-consuming hardware, enabling wireless sensor development for a fast, in-field and online analysis. In this review, the last five years of progress (from 2017 to 2021) in the field of optical chemical sensors development for persistent organic pollutants (POPs) is provided. The operating mechanisms, the transduction principles and the types of sensing materials employed in single selective optical sensors and in multisensory systems are reviewed. The selected examples of optical sensors applications are reported to demonstrate the benefits and drawbacks of optical chemical sensor use for POPs assessment.

Health risks of exposure to soil-borne dichlorodiphenyltrichloroethanes (DDTs): A preliminary probabilistic assessment and spatial visualization

Residues of dichlorodiphenyltrichloroethane and its metabolites (DDTs) in soils continue to severely threaten and endanger human health. This present study comprehensively interprets the health risks associated with exposure to soil-borne DDTs and also identifies the spatial visualization of risks at a large regional scale in Fujian, China. There was significant spatial variability of human risk across the region, while levels of health risk displayed a significant positive correlation with population density (p < 0.05). High risk levels occurred mostly in the coastal areas in northeastern Fujian, with additional hotspots in inland areas. The highest total incremental lifetime cancer risks (ILCRs) occurred in Sanming, reaching up to 9.52 × 10^-5, 3.27 × 10^-5, and 1.76 × 10^-4 for children, teens, and adults, respectively. Further, the highest hazard index (HI) value was observed in Fuzhou, reaching up to 6.09, 3.84, and 2.37, respectively. The 95% confidence interval of data regarding ILCRs exceeded the recognized safe threshold, whereas the HI has been deemed accepted. Adults were identified as the most susceptible population in terms of cancer risks, with o,p'-DDT being the primary contributor of ILCRs. Moreover, children were showed to be the most vulnerable in terms of non-cancer risks, with p,p'-DDD being the main contributor of HI. Food ingestion appeared to be the dominant exposure pathway, for both cancer and non-cancer risks. The concentration of DDTs (C_soil) and exposure duration (ED) also greatly influenced the risk, together contributing to over 99% of the ILCRs and HI.

Spatial distribution, deposition flux, and environmental impact of typical persistent organic pollutants in surficial sediments in the Eastern China Marginal Seas (ECMSs)

High emissions of synthetic compounds are damaging the marine environment and threatening human health. This study represents the first extensive and comprehensive analysis of three typical persistent organic pollutants (POPs), i.e., organochlorine pesticides (n = 228), perfluoroalkyl substances (n = 202), and short-chain chlorinated paraffins (n = 162), using a highly resolved spatial dataset. The results revealed the complex distribution of POPs in the Eastern China Marginal Seas (ECMSs). POPs in the surface sediments of the ECMSs showed spatial heterogeneity, with high levels observed mainly in areas with fine-grained sediments (e.g., the Yellow River and Changjiang River estuaries and the central south Yellow Sea). Strong positive correlations were identified between POP concentration and sediment grain size/components/longitude/latitude in the ECMSs, suggesting that POP distribution was significantly influenced by river input and regional hydrodynamics. The annual deposition fluxes of POPs in the ECMSs were also calculated and high values were recorded in the Yellow River Estuary and East China Sea. Human-induced changes in the catchments could affect the fate of POPs in the ECMSs and other river-dominated marginal seas worldwide. Our findings highlight concerns regarding local aquaculture and provide a basis for government decision-making. We also suggest the need for increased attention to be paid to the effects of marine organic pollution on aquaculture on a global scale.

Semi-centennial sediment records of HCHs and DDTs from the East China marginal seas: Role of lateral transport in catchment

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.

Atmospheric legacy organochlorine pesticides and their recent exchange dynamics in the Northwest Pacific Ocean

The occurrence and air-sea gas exchange of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs), and chlordanes were determined in the Northwest Pacific Ocean (NWP) in spring to elucidate their current pollution status and fate. ΣHCHs, ΣDDTs, and Σchlordanes in air (sum of gaseous and aerosol phase) ranged from 9.37 to 102, from 1.73 to 12.8, and from 0.24 to 14.9 pg/m³, respectively, with their dissolved levels being 30.7-518, 7.10-80.5, and 0.25-7.10 pg/L, respectively. HCHs, DDTs, and chlordanes cause substantial contamination of the air and seawater of the East China Sea (ECS), indicating significant OCP inputs from China. Isomer ratios of HCHs and DDTs provided a fingerprint of East Asian emissions of legacy OCPs, with the pollution profiles of HCHs and DDTs dominated by lindane and combined dicofol-type and weathered technical DDTs, respectively. The former result is consistent with the apparent decline in air α-HCH levels over the ECS. Different from still net deposition of gaseous α- and γ-HCH in the NWP, outgassing of trans-chlordane, cis-chlordane, and DDTs other than dicofol-sourced o,p'-DDT was indicated. This observation attributes to intensive historical usage of technical HCHs and the prevalence of lindane pollution in East Asia, and demonstrates the transitioning role of seawater as a source for residual OCPs in the East Asia-NWP region. Significant subcooled liquid vapor pressure-based relationships for legacy OCPs were identified mainly in marine air masses; these were different from land-sourced polybrominated diphenyl ethers, and suggested a heterogeneous role of ocean- and land-based sources in atmospheric partitioning of these pollutants.

Rapid changes in organochlorine pesticides in sediments from the East China sea and their response to human-induced catchment changes

Human-induced catchment changes have affected the sedimentary processes in marginal seas, which will impact the transport and burial processes of materials and inevitably impact marine biogeochemical cycles. Organochlorine pesticides (OCPs) and sediment characteristics in surface sediments from the East China Sea (ECS) at two time points (2006 and 2018) were compared to understand the response of OCPs to human-induced catchment changes. A significant coarsening trend occurred after the impoundment of the Three Gorges Dam (TGD), with the mean grain size increasing from 6.4 ± 1.2 Φ to 4.4 ± 2.1 Φ, suggesting that the sedimentary environment in the ECS changed drastically. OCP concentrations in the ECS evidently decreased after the impoundment of the TGD, with mean values decreasing from 2.55 ± 1.51 ng g^-1 to 1.08 ± 0.84 ng g^-1. The deposition flux of OCP also decreased from 2.65 ± 1.67 ng cm^-2 yr^-1 to 0.89 ± 0.60 ng cm^-2 yr^-1. The reduction in the riverine input might be the reason that caused variations in the OCP concentration and deposition flux. In addition, sediment coarsening is likely to be the another primary factor influencing the differences in the distribution and deposition flux of the OCPs in the ECS. Therefore, the distribution and burial of OCPs in the ECS have been changed drastically, which may broadly impact the marine environment and biogeochemical cycles.

Air-Seawater Gas Exchange and Dry Deposition of Chlorinated Paraffins in a Typical Inner Sea (Liaodong Bay), North China

As a group of new persistent organic pollutants, short-chain chlorinated paraffins (SCCPs) and medium-chain CP (MCCPs) have attracted extensive worldwide interest in recent years. However, the data regarding to the environmental behavior, especially in atmospheric transfer and air-seawater exchange, are still sparse. In this study, seasonal marine boundary layer air and seawater samples were collected from Chinese Bohai sea and a fugacity model was built to evaluate the air-seawater diffusion and deposition flux of CPs. Generally, the total CP levels in atmosphere and seawater samples in summer were higher than those in spring, and CPs existed mostly in the gaseous phase in air and the dissolved phase in seawater. For SCCPs, C₁₀ and C₁₁ components were the most abundant homologue groups. For MCCPs, the C₁₄ homologue dominated in the particle phase of atmosphere and particulate phase of seawater. The logarithmic fugacity ratios (log f_a/ f_w) of higher chlorinated congeners (Cl₈ to Cl₁₀: 0.71 to 1.32 in May and 1.38 to 2.29 in August) indicated that net deposition was the predominant process, whereas lower chlorinated congeners, especially Cl₅ homologue groups in August, showed a trend of net volitization (log  f_a/ f_w < -0.5). The results of diffusion and dry deposition fluxes indicated that air-seawater gas exchange of CPs was significantly higher than dry deposition in the sampling areas.

Organochlorine pesticides in the sedimentary core of the southern Tibetan Plateau: The missing pieces induced by lateral remobilization

The sedimentary core in remote alpine lakes has been recognized as an ideal proxy to reconstruct the emission and air deposition histories of persistent organic pollutants (POPs). Nevertheless, POPs formerly stored in a catchment might also contribute to the variation in the lake sediment by lateral remobilization. In this study, to reveal the relative importance of lateral remobilization, we measured the vertical profiles and isomeric ratios of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and endosulfan in a dated sedimentary core collected from Lake Yamzho Yumco in the southern Tibetan Plateau. In addition to the flux peaks in the 1970s corresponding to the heavy atmospheric deposition of DDTs and HCHs, these pollutants' fluxes displayed rebounds in the flood periods, with characteristic low ratios of DDT/DDE (α-/β-HCH). This might indicate a massive remobilization of "weathered" pesticides from catchment soil to the lake because of strong hydro-dynamics. Moreover, the relative contribution of lateral remobilization to the lake sediment in the past decades was recognized through the correlation between DDT/DDE (α-/β-HCH) ratios and ∑DDT (∑HCH) fluxes. The results showed that the lateral remobilization contributed to 20-42% of the total fluxes. This study discriminated the air deposition from the contribution of lateral remobilization, which improves current understanding of the vertical POPs profiles in the sedimentary core.

Diffusive flux of PAHs across sediment-water and water-air interfaces at urban superfund sites

Superfund sites may be a source of polycyclic aromatic hydrocarbons (PAHs) to the surrounding environment. These sites can also act as PAH sinks from present-day anthropogenic activities, especially in urban locations. Understanding PAH transport across environmental compartments helps to define the relative contributions of these sources and is therefore important for informing remedial and management decisions. In the present study, paired passive samplers were co-deployed at sediment-water and water-air interfaces within the Portland Harbor Superfund Site and the McCormick and Baxter Superfund Site. These sites, located along the Willamette River (Portland, OR, USA), have PAH contamination from both legacy and modern sources. Diffusive flux calculations indicate that the Willamette River acts predominantly as a sink for low molecular weight PAHs from both the sediment and the air. The sediment was also predominantly a source of 4- and 5-ring PAHs to the river, and the river was a source of these same PAHs to the air, indicating that legacy pollution may be contributing to PAH exposure for residents of the Portland urban center. At the remediated McCormick and Baxter Superfund Site, flux measurements highlight locations within the sand and rock sediment cap where contaminant breakthrough is occurring. Environ Toxicol Chem 2017;36:2281-2289. © 2017 SETAC.

Anthropogenic organochlorine compounds as potential tracers for regional water masses: A case study of estuarine plume, coastal eddy, wind-driven upwelling and long-range warm current

Water masses are the crucial factor driving the terrigenous anthropogenic organochlorine compounds (OCs) migration from the coast to open sea. Therefore, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in the Northern South China Sea (NSCS), where different types of water masses are generated by the East Asian summer monsoon: Pearl River estuary plume (PREP), Guangdong offshore eddy (GDEC), South China Sea warm current (SCSWC) and wind-driven upwelling current (WDUC). No discrepant distributions of OC concentrations were found in these water masses (p > 0.05). However, compositions and diagnostic ratios of HCHs, DDTs, trans- or cis-chlordane and PCBs could reflect the discrepancies in the input, transport and transformation of OCs caused by the hydrological characteristics of water masses, therefore, this allowing them to serve as potential tracers of regional water masses. In detail, α/γ-HCH and β-HCH percentages could indicate the weathered residue in the GDEC, long-range transport in the SCSWC, rapid photodegradation in the surface WDUC and biodegradation in the deep WDUC, respectively. The predominance of o, p'-DDT and p, p'-DDT could indicate fresh input in the PREP, GDEC and WDUC. DDT/DDTs of ratios <0.5 also reflected long-range transport in the SCSWC. Different DDD/DDE ratios indicated different oxygen environments of microbial degradation in the surface and deep water of the WDUC. Trans/cis-chlordane ratios could indicate the selective degradation of trans-chlordane in different water masses. Finally, a higher proportion of penta-PCB could reflect the strong paint additive sources carried by river erosion in the PREP.

Polychlorinated biphenyls and organochlorine pesticides in Tiber River and Estuary: Occurrence, distribution and ecological risk

The polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) pollution in the Tiber River and its environmental impact on the Tyrrhenian Sea (Central Mediterranean Sea) were estimated. 32 PCBs and 17 OCPs (aldrin, α-BHC, β-BHC, δ-BHC, lindane, p,p'-DDD, p,p'-DDE, p,p'-DDT, dieldrin, endosulfan I, endosulfan II, endosulfan sulfate, endrin, endrin aldehyde, heptachlor, heptachlor epoxide, methoxychlor) were determined in the water dissolved phase (DP), suspended particulate matter (SPM) and sediment samples. Total concentrations of PCBs ranged from 0.54 to 74.75ngL(-1) in water (sum of DP and SPM) and from 3.73 to 79.30ngg(-1) dry weigh in sediment samples; while the concentrations of total OCPs collected in water (sum of DP and SPM) ranged from 0.07 to 7.04ngL(-1) and from 0.66 to 10.02ngg(-1) dry weigh in sediment samples. Contaminant discharges into the sea were calculated in about 227.08kgyear(-1) for PCBs and 24.91kgyear(-1) for OCPs, showing that this river should account as one of the main contribution sources of PCBs and OCPs to the Tyrrhenian Sea. The ∑TEQPCB from the sediment samples ranged from 0.0006 to 0.37ngg(-1) with an average level of 0.13ngg(-1). Based on Sediments Quality Guidelines, biological adverse effects on aquatic ecosystem were rare to occasional for PCB and OCP levels in Tiber water system.

Estimation of Uncertainty in Air-Water Exchange Flux and Gross Volatilization Loss of PCBs: A Case Study Based on Passive Sampling in the Lower Great Lakes

Compared with dry and wet deposition fluxes, air-water exchange flux cannot be directly measured experimentally. Its model-based calculation contains considerable uncertainty because of the uncertainties in input parameters. To capture the inherent variability of air-water exchange flux of PCBs across the lower Great Lakes and to calculate their annual gross volatilization loss, 57 pairs of air and water samples from 19 sites across Lakes Erie and Ontario were collected using passive sampling technology during 2011-2012. Error propagation analysis and Monte Carlo simulation were applied to estimate uncertainty in the air-water exchange fluxes. Results from both methods were similar, but error propagation analysis estimated a smaller uncertainty than Monte Carlo simulation in cases of net deposition. Maximum likelihood estimations (MLE) of wind speed and air temperature were recommended to quantify the site-specific air-water exchange flux. An assumed 30-40% of relative uncertainty in overall air-water mass transfer velocity was confirmed. MLEs of volatilization fluxes of total PCBs across Lakes Erie and Ontario were 0.78 and 0.53 ng m^-2 day^-1, respectively, and gross volatilization losses of total PCBs over the whole lakes were 74 kg year^-1 for Lake Erie and 63 kg year^-1 for Lake Ontario. Mass balance analysis across Lake Ontario indicated that volatilization was the uppermost loss process of aqueous PCBs.