DDT In Sediments Research Articles

Occurrence and Ecological Risk Assessment of Typical Persistent Organic Pollutants in Hengshui Lake

Sediment samples were collected from 11 typical sites in Hengshui Lake separately in August 2018 and March 2019. Characteristics and ecological risk assessment of typical persistent organic pollutants (POPs), including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs), in these sediments were analyzed. The results showed that the average content of ΣPAHs in sediments of Hengshui Lake was 875.49 ng·g-1 and 1010.17 ng·g-1 in August 2018 and March 2019, respectively. Compared with other regions in China and abroad, ΣPAHs in sediments from Hengshui Lake were at moderate pollution level. Distribution of ΣPAHs varied between different sites, but the values changed within a narrow range in different seasons. Sources of PAHs in sediments from Hengshui Lake were complex, but combustion of wood and coal was the main source, followed by oil pollution. Generally, the ecological risk of PAHs was at a low level. However, fluorene pollution control should be strengthened. For ΣOCPs, the average values in sediments were 35.57 ng·g-1 and 38.39 ng·g-1 in August and March, respectively. Compared with other regions, the pollution of ΣOCPs was at a moderate level. In addition, the distribution of ΣOCPs varied a small amount between different sites. There were significant differences between the two seasons. The contents of DDTs in sediments were mainly related to the residual DDTs after long-term soil weathering and the input of recent DDTs sources. Contents of HCHs in sediments were influenced by the use of HCHs in industrial history and inputs of agricultural lindane. Generally, the ecological risk of OCPs was at a medium level, but the DDTs pollution control should be strengthened. For ΣPBDEs, the average values were 1.77 ng·g-1 and 1.45 ng·g-1 in the sediments in August 2018 and March 2019, respectively. Compared with other regions, they were at a lower pollution level. The distribution of ΣPBDEs showed small differences between different sites, and did not obviously vary between spring and summer. The PBDEs in sediments were mainly low-bromine PBDEs, which might be contaminated with penta-BDEs from textiles and foams. Additionally, PBDEs were also probably input by distant settlement and migration from the atmosphere, and soil flushing into the lake. PBDEs posed no immediate ecological risk.

Levels and distribution of pesticide residues in soil and sediments in Eastern Lake Tanganyika environs

The aim of this study was to investigate the types, levels and distribution of pesticide residues in Eastern Lake Tanganyika basin in Tanzania. Water, soil and sediments samples were collected from various sites in Kigoma region. Analyses of cleaned sample extracts were performed using gas chromatographyelectron capture detection (GC-ECD) and gas chromatography-mass spectrometry (GC-MS). Six pesticide residues and metabolites were detected, namely, p,p' -DDT, o,p' -DDT, p,p' -DDE, p,p' -DDD, diazinon and chlorpyrifos. DDT, DDD and DDE were the predominantly detected compounds in all of the samples. Diazinon and chlorpyrifos were detected in soil samples only. The highest concentrations of total DDT in sediments and soil ranged from 10.02 to 116 μg/kg dry weight (dw) and 7.5 to 564.2 μg/kg dw, respectively. Chlorpyrifos and diazinon had concentrations up to 36 and 184 μg/kg dw, respectively. The concentrations of DDT residues were greater in soil samples than in sediments. The highest concentrations of DDT residues were detected in soil samples. The ratios of ( p,p' -DDE + p,p' -DDD)/ p,p' -DDT indicated recent inputs in most samples. The study reveals that there were recent uses of DDT, diazinon and chlorpyrifos in the region. Continued use of DDT indicates risks and may result into serious environmental problems. The area therefore needs serious environmental monitoring. © 2017 International Formulae Group. All rights reserved. Keywords: Pesticide, Lake, soil, sediments, Tanzania

Residues of organochlorine pesticides and polycyclic aromatic hydrocarbons in surface waters, soils and sediments of the Kaidu River catchment, northwest China

We investigated residual levels of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) in water, soil and sediments from the Kaidu River catchment in Xinjiang, an arid zone in northwest China. Sediments from areas with highly polluted soil have higher OCPs and PAHs, caused by intensive anthropogenic activities. Pollution concentrations, however, were lower than those in Lake Bositeng indicating that the lake is a sink for pollutants in this region. Source analysis indicated that hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) originated mainly from historical agricultural applications. DDTs in sediments of the Lake Bositeng Estuary, however, may contribute to pollutant resuspension, resulting from sediment disturbance, and recent inputs. Low-molecular-weight PAHs were predominant, indicating that PAHs originated primarily from low-temperature combustion processes and petroleum-derived sources. A risk assessment of OCPs and PAHs in soil and sediment, suggested that concentrations were not high enough to cause adverse biological effects in the aquatic ecosystem.

Organochlorine pesticides across the tributaries of River Ravi, Pakistan: Human health risk assessment through dermal exposure, ecological risks, source fingerprints and spatio-temporal distribution

This study monitored the human health risks through dermal exposure, hazardous risks to ecological integrity, contamination levels, spatio-temporal distribution, and congener specific analysis of organochlorine pesticides (OCPs) across River Ravi and its three northern tributaries (Nullah Bein, Nullah Basanter and Nullah Deg). The residual levels of OCPs isomers were screened for water (n=54) and surface sediment (n=54) samples from twenty seven sampling sites in two alternate seasons (pre-monsoon and post-monsoon). The ∑OCPs concentrations ranged from 13.61 to 1992.18ng/g dry weight and 12.89 to 128.16ng/L with predominance of β-endosulfan and p,p′-DDT in sediment and water matrixes, respectively. Distribution pattern revealed significantly higher concentrations in upstream and midstream, suggesting considerable transboundary OCPs pollution. Calculated ratios of α-HCH/γ-HCH, o,p′-DDT/p,p′-DDT, (DDE+DDD)/∑DDTs and cis/trans-chlordane for water and sediments identified the fresh addition of lindane, technical DDTs and chlordane in the study area. Risk quotient (RQ) based ecological risk was found to be >1 at all studied streams during both seasons and elucidates higher risks for endosulfan (α-endosulfan) and endrin. Human health risk assessment indicated absence of hazardous (non-carcinogenic) risk through bathing in studied streams; as the hazard index values ranged from 1.09E−05 to 2.48E−02 (acceptable limit; <1). However, the calculated carcinogenic risk possessed by OCPs through dermal exposure ranged from 1.39E−10 to 1.98E−05 that highlighted the considerable carcinogenic risk associated to aldrin, dieldrin, p,p′-DDT and β-endosulfan at certain studied sites. Therefore, the high levels of ecological risk and carcinogenic human health risk had emphasized an immediate elimination of ongoing OCPs addition in the studied area.

Organochlorine pesticides and polycyclic aromatic hydrocarbons in water and sediment of the Bosten Lake, Northwest China

We evaluated organic pollution in Bosten Lake, Xinjiang, China, by measuring the concentrations and distributions of organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs). Water and sediment samples were collected from 19 sites (B1–B19) in the lake for analysis. Our analytical results show that the concentrations of total OCPs in water ranges from 30.3 to 91.6 ng/L and the concentrations of PAHs ranges from undetectable (ND) to 368.7 ng/L. The concentrations of total OCPs in surface (i.e., lake bottom) sediment ranges from 6.9 to 16.7 ng/g and the concentrations of PAHs ranges from 25.2 to 491.0 ng/g. Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) account for large proportions of the OCPs. Low α- to γ-HCH ratios in both water and sediment samples indicate possible contributions from both industrial products and lindane. DDTs in water are probably from historical input, whereas DDTs in sediments are from both historical and recent inputs. Moreover, DDT products in both water and sediments were from multiple sources in the northwestern part of the lake (B11, B12, B13, and B14). Fugacity ratios for DDT isomers (p,p′-DDE and p,p′-DDT) at these sites were generally higher than equilibrium values. These results suggest that the input from the Kaidu River and diffusion of DDTs from the sediment to the water are responsible for DDT pollution in the water. Lower-molecular-weight PAHs, which originate primarily from wood and coal combustion and petroleum sources, represent the major fraction of the PAHs in both water and sediment samples. Our findings indicate that OCPs and PAHs in Bosten Lake can be attributed primarily to human activities. A risk assessment of OCPs and PAHs in water and sediment from Bosten Lake, however, suggests that concentrations are not yet high enough to cause adverse biological effects on the aquatic ecosystem.

Remediation of organochlorine pesticides contaminated lake sediment using activated carbon and carbon nanotubes

Organochlorine pesticides (OCPs) in sediment were a potential damage for humans and ecosystems. The aim of this work was to determine the effectiveness of carbon materials remedy hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethanes (DDTs) in sediment. Two different carbon materials including activated carbon (AC) and multi-walled carbon nanotubes (MWCNTs) were used in the present research. Sediment treated with 2 wt% AC and MWCNTs after 150 d contact showed 97%, and 75% reduction for HCH, and 93% and 59% decrease for DDTs in aqueous equilibrium concentration, respectively. Similarly, the reduction efficiencies of DDT and HCH uptake by semipermeable membrane devices (SPMDs) treated with AC (MWCNTs) were 97% (75%) and 92% (63%), respectively under the identical conditions. Furthermore, for 2 wt% AC (MWCNTs) system, a reduction of XAD beads uptake up to 87% (52%) and 73% (67%) was obtained in HCH and DDT flux to overlying water in quiescent system. Adding MWCNTs to contaminated sediment did not significantly decrease aqueous equilibrium concentration and DDTs and HCH availability in SPMDs compared to AC treatment. A series of results indicated that AC had significantly higher remediation efficiency towards HCH and DDTs in sediment than MWCNTs. Additionally, the removal efficiencies of two organic pollutants improved with increasing material doses and contact times. The greater effectiveness of AC was attributed to its greater specific surface area, which was favorable for binding contaminants. These results highlighted the potential for using AC as in-situ sorbent amendments for sediment remediation.

Sequestration of HCHs and DDTs in sediments in Dongting Lake of China with multiwalled carbon nanotubes: implication for in situ sequestration.

Organochlorine pesticides (OCPs) in sediments could be released into water, posing great threats to human health and organisms. In this study, the treatment effectiveness of in situ sequestration of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethane (DDTs) in sediments was explored using multiwalled carbon nanotubes (MWCNTs) as adsorbents. Physicochemical tests (aqueous equilibrium concentrations, semipermeable membrane device (SPMD) uptake, and quiescent flux to overlying water) were conducted to evaluate the sequestration effectiveness of MWCNTs. Compared to the control, the MWCNT-treated sediments showed great reductions of HCHs and DDTs in aqueous equilibrium concentrations, SPMD uptake, and quiescent flux to overlying water. And the effects of dose of MWCNTs, diameter of MWCNTs, and contact time between MWCNTs and sediments on sequestration effectiveness were studied. Increased dose, decreased MWCNT diameter, and prolonged contact time resulted in a better sequestration effectiveness. The results indicated that the addition of MWCNTs to sediment could reduce the content of HCHs and DDTs released from sediments, reducing bioavailability of HCHs and DDTs and minimizing risks to ecosystem and human. MWCNTs have potential applications as adsorbents for in situ treatment of OCP-contaminated sediments.

Historical record and fluxes of DDTs at the Palos Verdes Shelf Superfund site, California.

Marine sediments at many locations in the world are contaminated with a wide range of persistent organic pollutants. The Palos Verdes Shelf (PVS) is located in the ocean off the coast of Los Angeles, California and has been listed as a Superfund site by the US EPA since 1997, because of heavy contamination of DDTs and PCBs. However, little is known about the historical trend in the deposition of DDTs as a result of decades-long discharge of wastewater effluents. In this study, sediment cores were taken from the PVS site and determined for DDT and its metabolites including DDE and DDD (denoted as DDTs). Individual DDTs were found in the majority (95%) of the samples analyzed. The highest ∑DDT concentrations were found in three cores along the 60-meter isobath with geometric means of 31300, 7490, and 5010ng/gdw and medians of 82400, 17300, and 5200ng/g dw, respectively. Among DDT congeners, p,p'-DDE, o,p'-DDE and p,p'-DDD were predominant, contributing to approximately 54%, 27%, and 14% of the ΣDDTs in sediment. The vertical profiles of concentrations of contaminants in the sediment cores were examined. For most of the cores, a steady increase in the concentrations of DDTs during 1940s to 1980s was observed, while the concentrations declined gradually toward the surficial layers. On the basis of the mass flux of DDTs calculated and the area of the PVS Superfund site, we estimated the total deposition amount of DDTs in sediment and the deposition amount of ΣDDTs in this region during 1947-1971 was 132 tons, which was fairly close to what was reported in earlier studies for industrial wastewater discharge in the PVS site (870-1450tons). Our findings suggest that the elevated levels of DDTs in sediment from the PVS site are linked to the discharge of these contaminants between the 1940s-1980s.

Polychlorinated biphenyls and organochlorine pesticides in surface sediments from Shantou Bay, China: Sources, seasonal variations and inventories

Sediments from Shantou Bay, China, were analyzed for polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) for the first time. The concentrations of PCBs and OCPs were 0.54–55.5ngg−1 and 2.19–16.9ngg−1 (dry weight), respectively. Source identification showed that tri-CBs and penta-CBs were manufactured and used in the last century, while usage of antifouling paint might still serve as a significant source of sediment DDT. Concentrations of PCBs and HCHs significantly (p<0.05) increased after wet season, suggesting that atmospheric deposition and surface runoff played an important role in distribution of historical pollutants. Additionally, the adverse biological effects could occasionally occur for DDT in sediments. The mass inventories were preliminarily calculated for PCBs (90.1ngcm−2 and 0.09tons) and OCPs (61.8ngcm−2 and 0.062tons) in Shantou Bay, while as part of the “reservoir” of organochlorine compounds to the global ocean, its role cannot be neglected.

Distribution Characteristics and Ecological Risk Assessment of Organochlorine Pesticides in Surface Sediments of Zhelin Bay in Guangdong Province, China

The distribution characteristics and pollution degrees of 20 organochlorine pesticides (OCPs) were investigated in surface sediments from Zhelin Bay south of China and the ecological risk of OCPs and integrated ecological risk at the samples stations in sediments were evaluated by risk quotient (RQ) and sediment quality guideline of NOAA. The possible sources of HCHs and DDTs in sediments were preliminarily studied, and the correlation between OCPs and sediment characteristic parameters was discussed. The concentrations of DDTs in surface sediments were found to be higher than those of other OCPs, especially p,p'-DDD, and the concentrations of DDTs were higher than the limited values of Chinese Marine sediment quality criteria. The total concentration of 20 OCPs in surface sediments ranged from 14.14 to 306.88 ng·g-1, with a mean concentration of 78.37 ng·g-1, and the highest total concentration was at site 8(S8). There were inevitable adverse biological effects and high ecological risk of p,p'-DDD and p,p'-DDT, high integrated ecological risk at S8 and S10. The possible sources of HCHs in surface sediments of Zhelin Bay were mainly from the application of Lindane pesticides. At S1,S2,S10,S11 there was input of DDT into mariculture area of Zhelin Bay, and at the other sites the sources of DDT were from the early residue in sediments or the long-term weathering sediments of using pesticides. There was a very significant positive correlation between HCHs, endosulfan, chlordane and dieldrin in sediments, while there was a negative relation between the above OCPs and TOC, which indicated that the presence of TOC could promote their biodegradation. There was a significant positive correlation between p, p'-DDD and Ca, which revealed that DDT used in the early period was deposited with biological carbonate. Increasing size of sediment particles discouraged the accumulation and enrichment of OCPs in sediments.

Characteristics and risk assessment of organochlorine pesticide residues in surface sediments collected at the Qingshitan Reservoir

ABSTRACTAn ultrasonic extraction – gas chromatography – electron capture detector analytical method was used to measure the concentration and types of organochlorine (OC) pesticides in sediment to obtain a better understanding of the characteristics and hidden ecological risks associated with OC pesticide exposure in surface sediment of the Qingshitan Reservoir. Fifteen types of OC pesticides were detected in the sediment, and the sum concentration of these chemicals was in the 149.32–490.19 ng/g range (mean value: 319.39 ng/g). The concentrations of detected OC pesticides occurred in the following order: hexachlorohexanes (HCHs) (mean value: 200.17 ng/g) > DDTs (mean value: 36.92 ng/g) > heptachlors (mean value: 32.74 ng/g) > methoxychlor (mean value: 24.13 ng/g). There was a 100% detection rate for HCH isomers, and their concentrations occurred in the following order: β-HCH > δ-HCH > γ-HCH > α-HCH. β-HCH was the main component of HCHs. Ratios between α-HCH/γ-HCH and β-/(α+γ)-HCH were used to investigate the sources of pollution. Most of the surveyed areas were polluted by lindane, which originated from past pesticide residue usage, and no new inputs of HCHs were found. DDT was the major component of the DDTs, and accounted for 52%–87% of the DDTs. The ratios of (DDE+DDD)/DDT at all sample collection points were less than 1, indicating that degradation rate of DDTs in sediment was low and there was a new input of DDTs in these surveyed areas. The ratio of DDD/DDE was less than 1 at most of the sample collection points, indicating that the degradation of DDT in the sediments primarily took place under aerobic conditions. Comparison of OC pesticide residual levels in the underwater sediment collected at the Qingshitan Reservoir to other states and countries showed the pollution level of these chemicals of the Qingshitan Reservoir was relatively high. The ecological risk was assessed based on guideline values of effects range-low (ERL) and effects range-medium (ERM). The results showed that DDD, DDE, DDTs and endrin residues in the sediment posed a moderate ecological risk, but DDT and γ-HCH showed high ecological risk. These OC pesticides might adversely affect biological systems, and need to be addressed.

The legacy of organochlorine pesticide usage in a tropical semi-arid region (Jaguaribe River, Ceará, Brazil): Implications of the influence of sediment parameters on occurrence, distribution and fate

Between the 1940s and 1990s, immeasurable amounts of organochlorine pesticides (OCPs) were used in endemic disease control campaigns and agriculture in the tropical semi-arid regions of Brazil. The present study evaluated the legacy of banned OCP usage, considering the levels, ecological risk and dependence on sediment physicochemical properties for the fate and distribution in the Jaguaribe River. The sum concentration of OCPs (ΣOCPs) ranged from 5.09 to 154.43ng·g−1, comparable to the levels found in other tropical and subtropical regions that have traditionally used OCPs. The environmental and geographical distribution pattern of p,p-DDT, p,p-DDD and p,p-DDE shows that the estuarine zone contained more than 3.5 times the levels observed in the fluvial region, indicating that the estuary of the Jaguaribe River is a sink. The temporal pattern indicates application of dichloro-diphenyl-trichloroethanes (DDTs) in the past; however, there is evidence of recent input of these pesticides. High ecological risk was observed for levels of γ-hexachlorocyclohexanes (γ-HCH) and heptachlor, and moderate ecological risk was observed for levels of DDTs in sediments from the Jaguaribe River. The heptachlor, γ-HCH and hexachlorobenzene (HCB) concentrations depend on the organic and inorganic fractions of sediment from the Jaguaribe River, whereas the p,p-DDE, p,p-DDD, p,p-DDT and α-endosulfan concentrations depend solely on the organic fraction of the sediment.

Assessing the distribution and human health risk of organochlorine pesticide residues in sediments from selected rivers.

Sediment samples from major agricultural producing areas in Edo state Nigeria were analysed for α-HCH, γ-HCH, β-HCH and ∑DDT with the aim of elucidating contamination profiles, distribution characteristics, carcinogenic and non-carcinogenic risk of these compounds in these regions. Analysis was done using a gas chromatography (GC) equipped with electron capture detector (ECD), while health risk assessment was carried out using the Incremental Lifetime Cancer Risk (ILCR) and the chronic daily intake (CDI). Results showed varying concentrations of α-HCH, γ-HCH, β-HCH and ∑DDT pesticides in sediment samples with hexachlorocyclohexane (∑HCHs) (4.6 µg/g/dw) being the dominant contaminants as it was widely detected in all samples and stations. Source identification revealed that the current levels of HCHs and DDT in sediments were attributed to both historical use and fresh usage of these pesticides. Risk estimates using ILCR and CDI showed that the risk of cancer and non-cancer effects was highest when exposure route was through ingestion. Furthermore, model projections highlights children as high risk population groups for non-dietary exposure to OCPs. These findings suggests the need for increased monitoring programmes, with a wider scope for both currently used pesticides and legacy/banned pesticides.

Distribution and ecological risk assessment of HCHs and DDTs in surface seawater and sediment of the mariculture area of Jincheng Bay, China

The distribution of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in the surface seawater and sediment of Jincheng Bay mariculture area were investigated in the present study. The concentration of total HCHs and DDTs ranged from 2.98 to 14.87 ng L−1 and were < 0.032 ng L−1, respectively, in surface seawater, and ranged from 5.52 to 9.43 and from 4.11 to 6.72 ng g−1, respectively, in surface sediment. It was deduced from the composition profile of HCH isomers and DDT congeners that HCH residues derived from a mixture of technical-grade HCH and lindane whereas the DDT residues derived from technical-grade DDT and dicofol. Moreover, both HCH and DDT residues may mainly originate from historical inputs. The hazard quotient of α-HCH, β-HCH, γ-HCH and δ-HCH to marine species was 0.030, 0.157, 3.008 and 0.008, respectively. It was estimated that the overall probability of adverse biological effect from HCHs was less than 5%, indicating that its risk to seawater column species was low. The threshold effect concentration exceeding frequency of γ-HCH, p,p′-DDD, p,p′-DDE and p,p′-DDT in sediment ranged from 8.3% to 100%, and the relative concentration of the HCH and DDT mixture exceeded their probable effect level in sediment. These findings indicated that the risk to marine benthos was high and potentially detrimental to the safety of aquatic products, e.g., sea cucumber and benthic shellfish.

Organo-halogenated contaminants (OHCs) in the sediments from the Soan River, Pakistan: OHCs(adsorbed TOC) burial flux, status and risk assessment

In this study, regression analysis revealed that TOC is the principal factor in controlling the fate of organo-halogenated contaminants (OHCs: PCBs, PBDEs, OCPs) in Soan River, Pakistan. The OHCs(adsorbed TOC) burial flux (OHCs(adsorbed TOC)Bf; mg/cm2·yr) was calculated in the following ranges: ∑PCBs (0.07–0.31), ∑PBDEs (0.005–0.029), ∑HCHs (0.015–0.046) and ∑DDTs (0.007–0.039). Apart from OHCs(adsorbed TOC)Bf, the levels of OHCs were in the following order: PCBs>DDTs>PBDEs>HCH>Chlordane>HCB. PBDEs and PCB congener patterns showed following order respectively: BDE-149>-153>-18>-138>-44 and PCB-149>-153>-18>-138>-44. DDT isomers and metabolites' pattern were p,p′-DDT>p,p′-DDD>p,p′-DDE>o,p′-DDT>o,p′-DDD>o,p′-DDE and HCHs were β-HCH>α-HCH>γ-HCH>δ-HCH. PBDE composition had similarities to penta-BDE and DE-71 mixtures and PCBs with commercial products Aroclor-1254 and -1260. (DDE+DDD)/∑DDTs and p,p′-DDT/p,p′-DDE suggested the recent input of DDTs in sediments while α/γ-HCH indicated past usage of lindane and technical mixtures. Risk assessment suggested that Soan River and its tributaries are potentially at risk against most of the OHCs.

Contamination profile of DDT and HCH in surface sediments and their spatial distribution from North-East India

Contamination status and spatial distribution of DDTs and HCHs were investigated in sediments collected from ponds and riverine system from districts Nagaon and Dibrugarh, North East India. A total of 113 surface sediment samples were collected from both the districts including 43 from ponds/wetlands and 70 from rivers/streams. Based on dry weight (dw), the mean concentration of ∑HCH and ∑DDT in sediments were found to be 287ng/g (71.2–834ng/g) and 321ng/g (30.1–918ng/g) for district Dibrugarh while 330ng/g (39.2–743ng/g) and 378ng/g (72.5–932ng/g) for district Nagaon, respectively. DDTs and HCHs in sediments were well influenced by total organic carbon, clay and silt content of sediments. Source identification revealed that sediment residue levels have originated from long and recent mixed source of technical HCH and Lindane for HCHs and mainly technical DDT for DDTs. Majority of samples exceeded the sediment quality guidelines (SQG) for γ-HCH, p,p′-DDT and ∑DDT indicating potential environmental risk. This baseline data can be used as reference for regular ecological and future POPs monitoring program.

Health and ecological risk-based characterization of soil and sediment contamination in shipyard with long-term use of DDT-containing antifouling paint

Dichlorodiphenyltrichloroethane (DDT) was a frequently occurring type of persistent organic environmental pollutant in China and DDT-containing antifouling paint could be the main contributor of DDT to shipyards and fishing harbors. A field survey was conducted in a shipyard in southern China to investigate the content and distribution of DDT in soil and sediments. Human health and screening-level ecological risk assessments were conducted for DDT contamination in soil and sediments and the results indicated that total DDT in all samples tested exceeded present advisory safe limits. Analysis of the composition and distribution implicated DDT-containing antifouling paint used for ship maintenance as an important source of DDT. Individual and cumulative health risks for residents exceeded the extra lifetime cancer risks of 10−6 and 10−5, mainly from exposure to soil, ingestion and dermal contact. DDT in sediments is associated with a high level of toxicity for the benthic community when >99% of samples exceed the threshold concentration likely to be responsible for effects and severe effects. Further risk control for DDT is required to ensure safety for human health, the benthic community and the environment.

Distribution, sources, and ecological risks of organochlorine pesticides in surface sediments from the Yellow River Estuary, China

Thirty-four surface sediment samples were analyzed for organochlorine pesticides (OCPs), in order to provide information on levels, distribution and sources of these compounds in the Yellow River Estuary, China. The levels of the organochlorine pesticides in samples were detected by the technique of soxhlet extraction followed by analysis by gas chromatography (GC) coupled with a mass selective detector. Total concentrations of OCPs ranged widely from 0.06 to 53.4 ng g(-1), with a mean value of 44.84 ng g(-1), at the mid level of pesticide concentrations compared to those reported in other regions worldwide. HCHs were the predominant species in the study area. The ratios of α-HCH/γ-HCH indicated that the technical HCH contamination was mainly due to a recent input of lindane in upper reach of Yellow River Estuary. The ratios of (DDD + DDE)/DDTs and DDD/DDE suggested that DDTs in sediments came mainly from the degradation of historical DDT in the environment, and DDT could be much easier to degrade into DDD under anaerobic conditions. Principal component analysis (PCA) could conclude that most of the OCPs came from early input and historical degradation products in the study area. Based on the sediment quality guidelines, γ-HCH and p'p-DDE would be of more concern for the ecotoxicological risk in this study area.

Occurrence and distribution of organochlorine residues in surface sediments of the Candarli Gulf (Eastern Aegean)

The residual levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in surface sediments collected from Candarli Gulf. Total concentrations of OCPs and PCBs in sediments ranged from 10.2 to 57.3 and 2.8 to 205ngg−1dwt, respectively. DDTs in sediments were derived from the aged and weathered agricultural soils in 61% of the sampling stations while 39% of the sites originated from the recent DDT inputs. Their concentrations appeared to be relatively low by global standards and only sediments receiving the impact from the Bakircay River and petrochemical industry approached the sediment quality guidelines for PCBs and DDTs. Based on ERL/ERM guidelines, DDT and PCBs posed ecological risk to the bottom-dwelling consumers.

Evaluating the performances of accelerated-solvent extraction, microwave-assisted extraction, and ultrasonic-assisted extraction for determining PCBs, HCHs and DDTs in sediments

Three extraction techniques have been recently used for the quantitative extraction of semi-volatile organic pollutants in sediments, i.e. accelerated solvent extraction (ASE), microwave assisted extraction (MAE) and ultrasonic assisted extraction (UAE). However, their extraction efficiencies have rarely been quantitatively compared using rigorous mathematical methods. In this paper, one-way analysis of variance (ANOVA) was employed to evaluate the performance of ASE, MAE and UAE in the overall extraction of PCBs, DDTs and HCHs by analysis of their recoveries from the Standard Reference Material IAEA-417, a sediment sample certified by many international laboratories. Conclusions were drawn at a significance level of P ≤ 0.05. No significant differences were found among the mean values for method recoveries using ASE, MAE and UAE. The mean values for real recoveries using ASE and MAE were nearly identical, but the real recovery using UAE was much lower. The concentrations of all PCBs, DDTs and HCHs except for CB52 and o,p′-DDT using UAE were the lowest. Comparing the results obtained using ASE with MAE, the concentrations of CB28, CB52, CB138, α-HCH, β-HCH, p,p′-DDE and p,p′-DDD were nearly identical, while the concentrations of other compounds were significantly different. Based on the low recoveries, it was concluded that UAE is a relatively inefficient extraction method, while ASE and MAE are equivalent methods. Taking into consideration the relative standard deviation (RSD) values, solvent volume, extraction time, and purchasing costs of the apparatus, MAE was considered superior to ASE for extraction of PCBs, DDTs and HCHs.