Distributions, sources, and ecological risks of DDT-related contaminants in water, suspended particulate matter, and sediments from Haihe Plain, Northern China

Effect of soil-groundwater system on migration and transformation of organochlorine pesticides: A review

Soil is the place where human beings, plants, and animals depend on for their survival and the link between the various ecological layers. Groundwater is an important component of water resources and is one of the most important sources of water for irrigated agriculture, industry, mining and cities because of its stable quantity and quality. Soil and groundwater are important strategic resources highly valued by countries around the world. However, in recent years, the deterioration of the ecological environment of soil-groundwater caused by industrial, domestic, and agricultural pollution sources has continued to threaten human health and ecological security. Among them, organochlorine pesticides (OCPs), as typical organic pollutants, cause very serious pollution of soil and groundwater environment. However, most studies on the pollution of OCPs have focused on the aboveground or surface water environment, and little consideration has been given to the pollution and hazards of OCPs to the deep soil and groundwater environment, especially the effects of different environmental factors on the transport and transformation of OCPs in soil-groundwater. Moreover, in addition to the influence of a single factor on it, the interactions that arise between different factors cannot be ignored. This paper focuses on two major sources of OCPs in soil and groundwater environments, compiles and summarizes the effects of environmental factors such as pH, microbial communities and enzyme activities on the transport and transformation of OCPs in soil and groundwater systems, discusses the synergistic effects of individual environmental factors and others, and comprehensively analyses the effects of synergistic effects of various environmental factors on the transport and transformation of OCPs. In the context of ecological civilization construction, it provides the scientific basis and theoretical foundation for the prevention and treatment of OCPs-contaminated soil and groundwater, and puts forward new ideas and suggestions for the research and development of green, eco-friendly remediation and treatment technologies for OCPs-contaminated sites.

Waste barrel contamination and macrobenthic communities in the San Pedro Basin DDT dumpsite

Industrial waste barrels were discarded from 1947 to 1961 at a DDT dumpsite in the San Pedro Basin (SPB) in southern California, USA at ~890 m. The barrels were studied for effects on sediment concentrations of DDX, PCBs, PAHs and sediment properties, and on benthic macrofaunal assemblages, including metazoan meiofaunal taxa >0.3 mm. DDX concentration was highest in the 2-6 cm fraction of the 10-cm deep cores studied but exhibited no correlation with macrofaunal density, composition or diversity. Macrofaunal diversity was lowest and distinct in sediments within discolored halos surrounding the barrels. Low macrobenthos density and diversity, high dominance by Entoprocta, and numerical prevalence of large nematodes may result from the very low oxygen concentrations in bottom waters (< 4.4 μM). There is potential for macrofauna to remobilize DDX into the water column and ultimately the food web in the SPB.

DDT contamination in water resources of some African countries and its impact on water quality and human health

Dichlorodiphenyltrichloroethane (DDT) usage has been prohibited in developed nations since 1972 but is exempted for use in indoor residual spraying (IRS) in developing countries, including African countries, for malaria control. There have been no previous reviews on DDT residues in water resources in Africa. The study aimed to provide a review of available research investigating the levels of DDT residues in water sources in Africa and to assess the consequent human health risks. A scoping review of published studies in Africa was conducted through a systematic electronic search using PubMed, Web of Science, EBSCO HOST, and Scopus. A total of 24 articles were eligible and reviewed. Concentrations of DDT ranged from non-detectable levels to 81.2 μg/L. In 35% of the studies, DDT concentrations surpassed the World Health Organization (WHO) drinking water guideline of 1 μg/L in the sampled water sources. The highest DDT concentrations were found in South Africa (81.2 μg/L) and Egypt (5.62 μg/L). DDT residues were detected throughout the year in African water systems, but levels were found to be higher during the wet season. Moreover, water from taps, rivers, reservoirs, estuaries, wells, and boreholes containing DDT residues was used as drinking water. Seven studies conducted health risk assessments, with two studies identifying cancer risk values surpassing permissible thresholds in water sampled from sources designated for potable use. Non-carcinogenic health risks in the studies fell below a hazard quotient of 1. Consequently, discernible evidence of risks to human health surfaced, given that the concentration of DDT residues surpassed either the WHO drinking water guidelines or the permissible limits for cancer risk in sampled drinking sources within African water systems. Therefore, alternative methods for malaria vector control should be investigated and applied.

Organochlorine pesticide residues in agricultural draining water in Tunisia

Organochlorines pesticides (OCPs) are persistent organic pollutants known by their persistence, their ability to bioaccumulate in the food chain and by their toxicity. This work aims to analyze pesticides in draining water samples taken from two different regions from Tunisia. A liquid-liquid extraction method proposed by the International Atomic Energy Agency (IAEA) has been adopted for the extraction of OCPs from draining water. The analysis of these compounds was carried out with a gas chromatography coupled to mass spectrometry. Eight draining water sample was analyzed from the region of Kebili and levels of OCPs ranged between ND and 3.415 ng L^-1. Four draining water samples were sampled from the region of Cap Bon and levels of OCPs in draining water varied between 14.955 and 59.305 ng L^-1. The concentration of OCPs in draining water didn't exceed the limits standardized by the regulations for drainage water, which makes possible the reuse of this water for agricultural purposes after having undergone a secondary treatment.

Soil aggregate-associated distribution of DDTs and HCHs in farmland and bareland soils in the Danjiangkou Reservoir Area of China

Soil organic matter (SOM) is the principal aggregating agent for soil aggregation and also the main adsorbent for organochlorine pesticides (OCPs) such as dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH), which may thereby affect OCP distribution in soils subjected to different land use types. However, the potential effects of land use on SOM and OCP distribution patterns in soil aggregates are not well understood. In this study, soils from farmlands and barelands in the Danjiangkou Reservoir area were analyzed to determine the influence of land use on OCP distribution and composition in different aggregate fractions (>3, 1-3, 0.25-1, and <0.25 mm). The results showed that the levels of ∑DDTs ranged from 9.01 to 27.48 with a mean of 14.40 ng g^-1, and ∑HCHs ranged from 2.06 to 4.66 with a mean of 3.19 ng g^-1 in farmland soils. In comparison, bareland soils were less contaminated, with total DDTs and HCHs fell in the range of 0.75-5.01 ng g^-1 and not detected (n.d.)-1.40 ng g^-1 respectively. In regard to the distribution patterns in soil aggregates, the residual levels of ∑DDTs and ∑HCHs tended to a certain degree to enrich in microaggregates (<0.25 mm) relative to bulk soils. A further analysis revealed that the enrichment of ∑DDTs and ∑HCHs in microaggregates were mainly attributed to the accumulation of p,p'-DDE and β-HCH. Moreover, SOM was found also enriched in microaggregates. The enrichment of SOM was significantly and positively correlated with these of ∑DDTs, ∑HCHs, and the dominant metabolites (i.e., DDE and β-HCH) in both land use types. Such results indicated that the variations in behavior of OCPs could be linked to the processes of soil aggregate turnover. These findings may help to enrich the theory of soil OCPs sequestration and establish targeted strategies to mitigate their health risks in the environment.

Ligninolytic enzymes: Versatile biocatalysts for the elimination of endocrine-disrupting chemicals in wastewater

Direct municipal wastewater effluent discharge from treatment plants has been identified as the major source of endocrine‐disrupting chemicals (EDC) in freshwaters. Consequently, efficient elimination of EDC in wastewater is significant to good water quality. However, conventional wastewater treatment approaches have been deficient in the complete removal of these contaminants. Hence, the exploration of new and more efficient methods for elimination of EDC in wastewater is imperative. Enzymatic treatment approach has been suggested as a suitable option. Nonetheless, ligninolytic enzymes seem to be the most promising group of enzymes for EDC elimination, perhaps, owing to their unique catalytic properties and characteristic high redox potentials for oxidation of a wide spectrum of organic compounds. Therefore, this paper discusses the potential of some ligninolytic enzymes (laccase, manganese peroxidase, and versatile peroxidase) in the elimination of EDC in wastewater and proposes a new scheme of wastewater treatment process for EDC removal.

Spatial distributions, source apportionment and ecological risk of SVOCs in water and sediment from Xijiang River, Pearl River Delta

Xijiang River is an important drinking water source in Guangxi Province, China. Along the Xijiang River and surrounding tributary, the pollution profile of three important groups of semi-volatile organic compounds, including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) and phthalate esters (PAEs), was analyzed. Relatively low levels of PAHs (64-3.7 × 10² ng L^-1) and OCPs (16-70 ng L^-1), but high levels of PAEs (7.9 × 10²-6.8 × 10³ ng L^-1) occurred in the water. Comparatively, low levels of OCPs (39-1.8 × 10² ng g^-1) and PAEs (21-81 ng g^-1), but high levels of PAHs (41-1.1 × 10³ ng g^-1) were found in sediment. Principal component analyses for source identification indicated petroleum-derived residues or coal and biomass combustion, and vehicular emission was the main sources for PAHs. The OCPs sources of each category were almost independent, whereas the new input of HCHs and p,p'-DDTs probably existed in some areas. PAEs were mainly originated from personal care products of urban sewage, plastic and other industrial sources. Ecological risk through the risk quotient analysis indicated a small or significant potential adverse effect on fish, daphnia and green algae. Nevertheless, the integrated risk of all pollutants should be taken into account in future study.

Ball Milling-Induced Plate-like Sub-microstructured Iron for Enhancing Degradation of DDT in a Real Soil Environment

The remediation of soil contaminated by 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) has been a challenge. In this paper, the degradation performances of the ball milling-induced plate-like sub-microstructured zero valent iron (SMZVI) to DDT in a real soil environment is studied. It has been found that such SMZVI exhibits much higher degradation performances to DDT in soil than commercial ZVI powders under acidic conditions. More than 95% DDT could be degraded within 80 min in the 5 ppm DDT-contaminated soil with addition of 50 mg g^-1 SMZVI, which is much better than the previously reported results. The time-dependent DDT removal amount can be well described by the pseudo first-order kinetic model. Further experiments have revealed that the ZVI dosages, surfactant's and acidic additions, and the weight ratio of soil-to-water in the slurries are important to DDT degradation, and the degradation products were mainly DDD (a product with less chlorine). An acid-assisted ZVI-induced reductive dechlorination process is proposed, which can well explain the DDT degradation behaviors in soil and the influence from the other factors. This work not only deepens the understanding of DDT degradation in soils based on ZVI but also demonstrates that the SMZVI could be a promising material for DDT degradation in real environments.

A review on environmental monitoring of water organic pollutants identified by EU guidelines

The contamination of fresh water is a global concern. The huge impact of natural and anthropogenic organic substances that are constantly released into the environment, demands a better knowledge of the chemical status of Earth's surface water. Water quality monitoring studies have been performed targeting different substances and/or classes of substances, in different regions of the world, using different types of sampling strategies and campaigns. This review article aims to gather the available dispersed information regarding the occurrence of priority substances (PSs) and contaminants of emerging concern (CECs) that must be monitored in Europe in surface water, according to the European Union Directive 2013/39/EU and the Watch List of Decision 2015/495/EU, respectively. Other specific organic pollutants not considered in these EU documents as substances of high concern, but with reported elevated frequency of detection at high concentrations, are also discussed. The search comprised worldwide publications from 2012, considering at least one of the following criteria: 4 sampling campaigns per year, wet and dry seasons, temporal and/or spatial monitoring of surface (river, estuarine, lake and/or coastal waters) and ground waters. The highest concentrations were found for: (i) the PSs atrazine, alachlor, trifluralin, heptachlor, hexachlorocyclohexane, polycyclic aromatic hydrocarbons and di(2-ethylhexyl)phthalate; (ii) the CECs azithromycin, clarithromycin, erythromycin, diclofenac, 17α-ethinylestradiol, imidacloprid and 2-ethylhexyl 4-methoxycinnamate; and (iii) other unregulated organic compounds (caffeine, naproxen, metolachlor, estriol, dimethoate, terbuthylazine, acetaminophen, ibuprofen, trimethoprim, ciprofloxacin, ketoprofen, atenolol, Bisphenol A, metoprolol, carbofuran, malathion, sulfamethoxazole, carbamazepine and ofloxacin). Most frequent substances as well as those found at highest concentrations in different seasons and regions, together with available risk assessment data, may be useful to identify possible future PS candidates.

Ecological risk assessment of microcystin-LR in the upstream section of the Haihe River based on a species sensitivity distribution model

The eutrophication of surface water has been the main problem of water quality management in recent decades, and the ecological risk of microcystin-LR (MC-LR), which is the by-product of eutrophication, has drawn more attention worldwide. The aims of our study were to determine the predicted no effect concentration (PNEC) of MC-LR and to assess the ecological risk of MC-LR in the upstream section of the Haihe River. HC₅ (hazardous concentration for 5% of biological species) and PNEC were obtained from a species sensitivity distribution (SSD) model, which was constructed with the acute toxicity data of MC-LR on aquatic organisms. The concentrations of MC-LR in the upstream section of the Haihe River from April to August of 2015 were analysed, and the ecological risk characteristics of MC-LR were evaluated based on the SSD model. The results showed that the HC₅ of MC-LR in freshwater was 17.18 μg/L and PNEC was 5.73 μg/L. The concentrations of MC-LR ranged from 0.68 μg/L to 32.21 μg/L and were obviously higher in summer than in spring. The values of the risk quotient (RQ) ranged from 0.12 to 5.62, suggesting that the risk of MC-LR for aquatic organisms in the river was at a medium or high level during the study period. Compared with other waterbodies in the world, the pollution level of MC-LR in the Haihe River was at a moderate level. This research could promote the study of the ecological risk of MC-LR at the ecosystem level.

The evolution of pollution profile and health risk assessment for three groups SVOCs pollutants along with Beijiang River, China

Three important groups of semi-volatile organic compounds (SVOCs), polycyclic aromatic hydrocarbons (PAHs), organic chlorinated pesticides (OCPs) and phthalate esters (PAEs), were produced by various human activities and entered the water body. In this study, the pollution profiles of three species including 16 PAHs, 20 OCPs and 15 PAEs in water along the Beijiang River, China were investigated. The concentrations of Σ₁₆PAHs in the dissolved and particulate phases were obtained as 69-1.5 × 10² ng L^-1 and 2.3 × 10³-8.6 × 10⁴ ng g^-1, respectively. The levels of Σ₂₀OCPs were 23-66 ng L^-1 (dissolved phase) and 19-1.7 × 10³ ng g^-1 (particulate phase). Nevertheless, higher levels of PAEs were found both in the dissolved and particulate phases due to abuse use of plastic products. Furthermore, non-cancer and cancer risks caused by these SVOCs through the ingestion absorption and dermal absorption were also assessed. There was no non-cancer risk existed through two kinds of exposure of them at current levels, whereas certain cancer risk existed through dermal absorption of PAHs in the particulate phase in some sampling sites. The results will show scientific insights into the evaluation of the status of combined pollution in river basins, and the determination of strategies for incident control and pollutant remediation.

Using Chironomus dilutus to identify toxicants and evaluate the ecotoxicity of sediments in the Haihe River Basin

To effectively manage a watershed and successfully restore a river system, it is very important to assess the toxicity of sediments and identify the substances causing the toxicity. Seventy-six sediments collected in the Haihe River Basin (HRB) in China were screened for acute toxicity using Chironomus dilutus. We found that sediments from more than 32% of sampling sites, distributed mainly in the Ziya tributary and along the estuary, were acutely toxic to midges. A toxicity identification evaluation showed that the toxicity of the sediment samples was mainly from ammonia nitrogen, metals, and organics. Calculations of the toxic unit (TU) showed that ammonia and metals contributed more to sediment toxicity than organics, and that PAHs may have contributed in other tributaries. A modified three-step sequential extraction procedure to assess the bioavailability of the metals indicated that the toxicity from metals was mainly from Cd and Zn. This is one of the first studies in which this type of approach has been applied to directly connect contaminants with ecological effects in the HRB.

Current status and historical variations of DDT-related contaminants in the sediments of Lake Chaohu in China and their influencing factors

The temporal-spatial distributions of DDT-related contaminants (DDXs), including DDT (dichlorodiphenyltrichloroethane), DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane), in the sediments of Lake Chaohu and their influencing factors were studied. p,p-DDE and p,p-DDD were found to be the two dominant components of DDXs in both surface and core sediments. The parent DDT compounds were still detectable in sediment cores after the late 1930s. Historical usage of technical DDT was identified as the primary source of DDXs in sediments, as indicated by DDT/(DDD + DDE) ratios of less than one. The residual levels of DDXs were higher in the surface and core sediments in the western lake area than in other lake areas, which might be due to the combined inflow effects of municipal sewage, industrial wastewater and agricultural runoff. The DDX residues in the sediment cores reached peak values in the late 1970s or early 1980s. There were significant positive relationships between DDX residues in sediment cores with annual DDT production and with fine particulate sizes (<4.5 μm). The relationship between the DDXs and TOC in sediment was complex, as indicated by the significant differences among the surface and core sediments. The algae-derived organic matter significantly influenced the amount of residue, composition and distribution of DDXs in the sediments. The DDD/DDE ratios responded well to the anaerobic conditions in the sediments that were caused by algal blooms after the late 1970s in the western lake area. This suggests that the algae-derived organic matter was an important factor and served as a biomarker of eutrophication and also affected the DDX residues and lifecycle in the lake ecosystem.

Concentrations and distribution of organochlorine pesticides in pine needles of typical regions in Northern Xinjiang

The residues of organochlorine pesticides (OCPs) in 29 pine needle samples of typical regions (including Shihezi, Beitun, and Kanas) in Northern Xinjiang was determined with a gas chromatograph equipped with an electron capture detector. Total OCPs concentrations in pine needles ranged from 2.94 to 186 ng/g dry weight, with a mean concentration of 39.63 ng/g. The results indicated that Beitun was the most polluted region while Kanas was the least polluted one. Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the predominant species in samples. Analysis of the sources of contamination showed that HCHs in the needles were derived from an old mixed source of technical HCHs or lindane. For DDTs, it was suspected to have recent application at some sites, which were derived mainly from a mixture of technical DDTs and dicofol containing DDT impurities. Categorical principal component analysis was performed in finding out more about the degradation behavior of DDTs and HCHs, which was identical with the results of source analysis.

Evaluation of foam surfactant for foam-flushing technique in remediation of DDT-contaminated soil using data envelopment analysis method

With an aim to select the most appropriate foaming surfactant for remediation of DDT-contaminated soil by foam-flushing technique, the performances of nonionic and anionic surfactant in several aspects were observed in this study. SDS had the best foam static characteristic among the four experimental surfactants. The solubilizing ability for DDT followed the order of Tween80 > TX100 > SDS > Brij35. The adsorption loss of SDS onto soil was the lowest. The order of desorption efficiency for DDT followed as TX-100 > Tween80 > Brij35 > SDS. Based on these experimental investigations, the overall performances of foaming surfactants were evaluated by data envelopment analysis method. The results indicated that SDS was the optimal alternative for remediation of DDT-contaminated soil by foam-flushing technique. This conclusion was reached with the consideration of the cost, foam static characteristic, surfactant adsorption loss, solubilizing ability, and desorption efficiency of surfactant for DDT.

Concentrations, distributions, sources, and risk assessment of organochlorine pesticides in surface water of the East Lake, China

East Lake resides in the urban area of Wuhan City and is the largest urban lake in China. The concentrations of 16 organochlorine pesticides (OCPs) were analyzed in 108 surface water samples collected from the East Lake. The total concentrations of OCPs ranged from not detected to 120 ng L(-1) with predominance of δ-HCH, heptachlor, and α-HCH. The mean values of HCHs and DDTs were 7.40 and 5.70 ng L(-1), respectively, accounting for 40 and 31 % of the total OCPs. For the five lakelets in East Lake, Houhu Lake exhibited the highest concentrations of HCHs, DDTs, and total OCPs, which has been used actively for fisheries and surrounded by suburban rural areas and farmlands. Historical lindane or technical HCH input was probably the source of HCH, while technical DDTs might be the source of DDT in the East Lake. The ratio between heptachlor and its metabolic products indicated recent input of heptachlor. Although the combining ecological risks for all aquatic species in the East Lake calculated by species sensitivity distribution reached approximately 10(-5), the OCPs in the East Lake had slight effects on aquatic organisms. The carcinogenic risks and non-carcinogenic hazard indices of DDTs and HCHs indicated that water in the East Lake was not suitable as water sources for human. However, the results indicated the water quality was safe for people to swim in the urban lake.

DDT residue contamination in sediments from Lake Sibaya in northern KwaZulu-Natal, South Africa: implications for conservation in a World Heritage Site

Maputaland in northern KwaZulu-Natal is a biodiversity hotspot and host to a number of ecologically important systems, including Lake Sibaya, southern Africa's largest natural freshwater lake. The region is malaria endemic and this study reports the presence of DDT and its metabolites in the sediments of Lake Sibaya that have resulted from the widespread and continued use of DDT in the region. DDT residues (p,p'-DDT, p,p'-DDD, and p,p'-DDE) were detected at all 11 sites sampled, with total concentrations ranging from 0.8 to 123 ng g(-1). Total DDT concentrations at Lake Sibaya represent some of the highest levels reported in South Africa, with most samples exceeding sediment quality guideline values. The findings from this study raise concerns and indicate that urgent further work is needed to investigate the potential for bioaccumulation, which could adversely affect breeding fish, bird, and crocodile populations in the region. While this study represents the first report on DDT contamination in Lake Sibaya, results have important implications for a number of other aquatic ecosystems within the Maputaland ecoregion, as well as the many local people who depend on them.

The residues, distribution, and partition of organochlorine pesticides in the water, suspended solids, and sediments from a large Chinese lake (Lake Chaohu) during the high water level period

The levels of organochlorine pesticides (OCPs) in the water, suspended solids, and sediments from Lake Chaohu during the high water level period were measured by a solid-phase extraction gas chromatograph-electron capture detector. The spatial distributions of the three phases and the water/suspended solids and sediment/water partition coefficients were analyzed. The results showed the following: (1) The mean contents of OCPs in the water, suspended solids, and sediments were 132.4 ± 432.1 ng/L, 188.1 ± 286.7 ng/g dry weight (dw), and 13.7 ± 9.8 ng/g dw, respectively. The dominant OCP components were isodrin (85.1%) for the water, DDTs (64.4%) for the suspended solids, and both isodrin (48.5%) and DDTs (31.8%) for the sediments. (2) β-HCH was the primary isomer of HCHs in the water and sediments, and the proportions were 61.7 and 41.3%; γ-HCH was the primary isomer in the suspended solids, accounting for 49.3%; p,p'-DDT was the dominant content of DDTs in the water and suspended solids, whereas p,p'-DDD was the main metabolite of DDTs in the sediments. (3) The concentrations of contaminants in the water from the western lake were greater than those from the eastern lake, but the concentrations in the suspended solids from the western lake were less than those from the eastern lake. (4) There was no significant correlation between the water-suspended solids partition coefficient Kd and the n-octanol-water partition coefficient Kow, and between the sediment-water organic-C weighted sorption coefficients Koc and Kow.