Source Of DDT Research Articles

Pollution sources and occurrences of selected persistent organic pollutants (POPs) in sediments of the Mekong River delta, South Vietnam

The Mekong River delta is one of the largest agricultural land in the Southeast Asia. It plays a very important role for agriculture and fisheries in South Vietnam. However, comprehensive studies on the environmental pollution of persistent organic pollutants (POPs) in Mekong River delta have not been carried out in recent years. In this study, we collected sediment samples from the Mekong River to evaluate the contamination and ecological risks caused by several POPs. The contamination pattern of POPs was DDT>PCBs>CHLs>HCHs>HCB. DDTs are the most abundant pollutants, their concentration ranging from 0.01 to 110 ng/g dry wt, followed by PCBs (0.039-9.2 ng/g dry wt). DDTs and PCBs concentrations were higher in sediment from adjacent to urban areas than those from rural and agricultural sites, suggesting urban areas as important point sources of DDTs and PCBs to the river. Ratio of p,p'-DDT/p,p'-DDE was lower compared to those previously reported. However, some samples still had the ratio higher than 0.5, indicating recent input of DDT into the aquatic environments. This result shows that although the magnitude of contamination decreased over time, recent inputs of DDTs to the river still occur. Some sediment samples had concentrations of DDT compounds higher than the standards from the Canadian Environmental Quality Guideline, suggesting continuous monitoring for POPs contamination in the Mekong River is necessary.

Concentrations, enantiomeric compositions, and sources of HCH, DDT and chlordane in soils from the Pearl River Delta, South China

Concentrations, and enantiomeric compositions of HCH, DDT and chlordane in 74 soils of the Pearl River Delta, South China were investigated. The mean concentrations of HCHs and DDTs descended in the order: crop soils>paddy soils>natural soils. The concentrations (ng/g dw) of p,p'-DDE, p,p'-DDT, p,p'-DDD and o,p'-DDT in crop soils were 0.14-231, 0.07-315, <DL-96.7 and 0.06-73.8, respectively, while those of chlordane were generally below 0.78 for trans-chlordane (TC) and 0.75 for cis-chlordane (CC). Enantiomeric factors (EF value) were determined for o,p'-DDT, alpha-HCH, TC and CC. Both preferential depletions of (-) enantiomer and (+) enantiomer were observed for o,p'-DDT and alpha-HCH, indicated by EF values either <0.5 or >0.5. An EF value >0.5 generally suggested a preferential degradation of the (-) enantiomers of both TC and CC. The racemic alpha-HCH observed in the soils with higher HCH concentrations indicated that the transformation from gamma-HCH (e.g. lindane) to alpha-HCH may be an important process in the soils. The isomer ratios of p,p'-DDT/(DDE+DDD), o,p'-DDT/p,p'-DDT and enantiomeric compositions of o,p'-DDT suggested that both illegal use of technical DDT and the DDT impurity in dicofol may be responsible for the freshly DDT input in the region. The sources of DDTs were drawn by principal component analysis-multiple linear regression (PCA-MLR). The relative contributions of dicofol-type DDT, residues, and fresh technical DDT were estimated to be 55%, 21% and 17%, respectively. In addition, CC was found to degraded faster than TC in soils from the Pearl River Delta. The study demonstrated that the combination of isomer ratios and enantiomeric composition analysis may provide critical information on the potential sources and fate of organochlorine pesticides in soil.

Organochlorine Contaminants in Human Adipose Tissues from China: Mass Balance Approach for Estimating Historical Chinese Exposure To DDTs

Concentrations of persistent organochlorines (OCs), such as DDTs, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), polychlorinated biphenyls (PCBs), and chlordane compounds (CHLs) were determined in 34 human adipose tissues collected from Guizhou Province, southern China, during 2002. DDT was the predominant contaminant among OCs analyzed; concentrations ranged from 420 to 20 000 ng/g on a lipid wt basis (average +/- sd: 5700 +/- 4100 ng/g). Concentrations of DDTs and the ratio of p,p'-DDT/ sigmaDDT in humans in China were significantly higher than those reported for developed countries. DDT levels in humans in Guizhou Province were comparable to those from Shanghai City, implying the presence of significant sources of DDTs in inland and coastal areas in China. Age-dependent accumulation of HCH concentration was found in this study, possibly because of the considerable reduction in average dairy intake (ADI) of HCHs by Chinese during the recent two decades. On the basis of the information of the ADI rates, half-lives, and body burdens of DDTs, the magnitude of historical DDT exposures by Chinese was estimated. This suggested that approximately 80% of DDTs deposited in Chinese adipose tissues was accumulated before the 1990s. The monitoring of OC levels and epidemiological studies are needed in China to understand the status of contamination and the risks to humans.

Distribution of DDT in sediments off the central California coast

A collaborative sampling cruise off the central California coast was conducted to evaluate contaminant transport pathways along and across the shelf in the spring of 2002. The area has a complex current structure and net transport routes are not known for sure. Sediment characteristics, and organic and trace metal contaminants were analyzed in sediments taken from locations near shore, out to the heads of several canyons. Relative to the continental shelf and Pioneer Canyon stations, DDT was found at higher concentrations in Ascension and Monterey Canyons. Monterey Bay still receives DDT from terrestrial runoff and may be the source of DDT found in Ascension Canyon. DDT concentrations in Monterey Bay biota indicate bioaccumulation is occurring at depth due to continuing input from the shore. Effects on the deep ocean benthic community is unknown.

Level and distribution of DDT in surface soils from Tianjin, China

One hundred and eighty eight surface soil samples were collected from the Tianjin area to study the contamination of DDT and its metabolites. Measurements were taken for p, p ′-DDE, p, p ′-DDD, p, p ′-DDT, o, p ′-DDE, o, p ′-DDD and o, p ′-DDT for all samples. The results indicated that p, p ′-DDT and p, p ′-DDE were the predominant contaminant compounds in the surface soil samples, with mean concentrations of 27.5 and 18.8 ng g −1 respectively. No significant differences in DDT concentrations were found between the soils from wastewater treated irrigated areas and other areas, suggesting that wastewater irrigation is not an important source of DDT in the area. However, the spatial distribution of soil DDTs levels in the area did correlate well with early direct application rates of pesticides. In addition, both pH level and organic carbon content are also known factors affecting the level of DDT and its metabolites. Although it was assumed that the use of these chemicals was banned in the early 1980s, the current concentration levels appear to be too high to be mere residuals after 20 years degradation.

Conifer needles as passive biomonitors of the spatial and temporal distribution of DDT from a point source

Needles of two conifer species, Picea abies and Pinus nigra, were used as passive samplers for monitoring air contamination by sampling at increasing distances from a suspected point source of DDT. Needle concentrations declined with increasing distance downwind of the point source allowing to identify spatial and temporal trends of accumulation. This suggested that conifer needles are effective biomonitors of contamination levels in areas characterized by the presence of semi-volatile substances. Differences in uptake were apparent between the species. Needle morphology and structure were studied with scanning electron microscope (SEM) as were dimensional parameters (surface area, volume). The results suggest that the concentrations depend on a mechanism involving the inner structure of the needles, specifically the number and accessibility of resin channels rather than their surface area. Pine needles have more channels with greater accessibility than spruce. The results suggest that spruce is more suitable for short term measurement while pine for determining long term cumulative exposure.

Distribution of HCH and DDT in the coastal marine environment of Mumbai, India.

Organochlorine pesticides (OCPs) in sediment, water and biota samples from the coastal marine environment of Mumbai were analysed to elucidate their distribution in various environmental compartments. HCH isomers, dichlorodiphenyltrichloroethane (DDT) and its metabolites were the predominantly identified compounds in all the samples. High ratios of DDT to dichlorodiphenyldichloroethylene (DDE) were found in seawater samples. This indicates the presence of a significant source of DDT in this region. In sediment samples, the gamma-isomer contributed almost 55% to the total HCH, indicating a high affinity of the gamma-isomer towards the sediment. The levels of organochlorines in fish obtained from this region were found to be lower than the levels of organochlorines in fish in temperate regions.

Organochlorine contamination in fish and mussels from Cambodia and other Asian countries

Contamination by organochlorine compounds (OCs) was examined in fish and mussels collected from Cambodia and other Asian developing countries in 1997 and 1998. DDT and its metabolites were the predominantly detected compound in both fish and mussel samples. PCBs were second highest, followed by HCHs, CHLs, and HCB. Freshwater fish contained higher concentrations of DDTs than marine fish and mussels, implying that the source of DDTs originated from inland watersheds such as the Mekong River, Basac River, Tonlesap River, and Tonlesap Great Lake. Comparison of the OC residue levels in fish and mussels from Cambodia with those in other Asian and Oceanic regions suggested that Cambodia is one of the countries least contaminated by OCs. In other words, it can be concluded that among Asian and Oceanic countries Cambodia has kept a “Clean Environment”.

Diagenetic fate of organic contaminants on the Palos Verdes Shelf, California

Municipal wastes discharged through deepwater submarine outfalls since 1937 have contaminated sediments of the Palos Verdes Shelf. A site approximately 6–8 km downcurrent from the outfall system was chosen for a study of the diagenetic fate of organic contaminants in the waste-impacted sediments. Concentrations of three classes of hydrophobic organic contaminants (DDT+metabolites, polychlorinated biphenyls (PCBs), and the long-chain alkylbenzenes) were determined in sediment cores collected at the study site in 1981 and 1992. Differences between the composition of effluent from the major source of DDT (Montrose Chemical) and that found in sediments suggests that parent DDT was transformed by hydrolytic dehydrochlorination during the earliest stages of diagenesis. As a result, p,p′-DDE is the dominant DDT metabolite found in shelf sediments, comprising 60–70% of ΣDDT. The p,p-DDE/p,p′-DDMU concentration ratio decreases with increasing sub-bottom depth in sediment cores, indicating that reductive dechlorination of p,p′-DDE is occurring. Approximately 9–23% of the DDE inventory in the sediments may have been converted to DDMU since DDT discharges began ca. 1953. At most, this is less than half of the decline in p,p′-DDE inventory that has been observed at the study site for the period 1981–1995. Most of the observed decrease is attributable to remobilization by processes such as sediment mixing coupled to resuspension, contaminant desorption, and current advection. Existing field data suggest that the in situ rate of DDE transformation is 102–103 times slower than rates determined in recent laboratory microcosm experiments (Quensen, J.F., Mueller, S.A., Jain, M.K., Tiedje, J.M., 1998. Reductive dechlorination of DDE to DDMU in marine sediment microcosms. Science, 280, 722–724.). This explains why the DDT composition (i.e. o,p′-, p,p′-isomers of DDE, DDD, DDT) of sediments from this site have not changed significantly since at least 1972. Congener-specific PCB compositions in shelf sediments are highly uniform and show no evidence of diagenetic transformation. Apparently, the agents/factors responsible for reductive dechlorination of DDE are not also effecting alteration of the PCBs. Two types of long-chain alkylbenzenes were found in the contaminated sediments. Comparison of chain length and isomer distributions of the linear alkylbenzenes in wastewater effluent and surficial sediment samples indicate that these compounds undergo biodegradation during sedimentation. Further degradation of the linear alkylbenzenes occurs after burial despite relatively invariant isomer compositions. The branched alkylbenzenes are much more persistent than the linear alkylbenzenes, presumably due to extensive branching of the alkyl side chain. Based on these results, p,p′-DDE, PCBs, and selected branched alkylbenzenes are sufficiently persistent for use in molecular stratigraphy. The linear alkylbenzenes may also provide information on depositional processes. However, their application as quantitative molecular tracers should be approached with caution.

Persistent Organochlorine Residues in Marine and Freshwater Fish in Cambodia

Concentrations of persistent organochlorines (OCs) such as PCBs (polychlorinated biphenyls), DDT compounds (DDTs), HCH (hexachlorocyclohexanes) isomers (HCHs), chlordane compounds (CHLs) and HCB (hexachlorobenzene) were determined in 27 species of marine and freshwater fish collected from Cambodia. DDT and its derivatives were the predominantly detected compounds in both marine and freshwater fish. PCBs were the second highest followed by HCHs, CHLs and HCB. Freshwater fish contained higher concentrations of DDTs than those of marine fish, implying that the sources of DDTs originate from inland watersheds such as the Mekong River, Basac River, Tonlesap River and Tonlesap Great Lake. Comparison of the OCs residue levels in Cambodian fish with those in other Asian and Oceanic regions suggested that Cambodia is one of the less-contaminated countries by OCs. In other words, it can be concluded that Cambodia has kept “Clean Environment” among Asian and Oceanic countries.

Dispersion of sediment DDTs in the coastal ocean off southern California

The masses of DDT compounds (DDTs) in surface sediments of the Palos Verdes Shelf (PVS) and Santa Monica Bay (SMB) have declined over the last two decades, following the ban on DDT production in 1970. This mass reduction could result from a number of biological and physical processes, including biodegradation and/or dispersal away from the sites. We integrated existing data with our new data of DDTs from different compartments in the coastal zones off southern California to assess the importance of the dispersal mechanism. The synthesis of the data indicated that: (1) historically deposited DDTs have been remobilized upward in the sediment column; (2) DDTs have been resuspended into the water column; and (3) sewage-derived DDTs have been redeposited into distant areas. Resuspension of DDTs from contaminated sediments was evident from the close correlation between the DDT concentrations in the water column and surface sediment at three locations with different DDT levels. The current distribution patterns for linear alkylbenzenes and DDTs in surface sediments at SMB were also suggestive of dispersal of DDTs. The distribution of DDTs in the surface sediments exhibiting a gradient from the outfalls to offshore and the general spatial distribution pattern in the basins precluded the possibility of either aerial fallout or surface runoff as being an important source of DDTs. These results are consistent with the hypothesis that resuspended DDTs in the discharge zones are being dispersed to distant areas. The percent of DDEs in total DDTs was uniformly high (∼90%) in the PVS and SMB sediments, but varied widely in sediments of the Santa Monica and San Pedro Basins. The percent DDEs were particularly low (as low as 10%) in certain subsurface sections of the sediments near two dumpsites containing DDT wastes (from prior to 1970) comprising of low proportions of DDE. However, the top-layers of the basin sediments contained DDT residues with high %DDEs similar to that of sediments on the PVS, suggesting a common source from the historic DDTs in the wastewater discharges. The available data is insufficient to confirm the possibility of anaerobic degradation of DDEs in the sediment cores investigated which could also result in the mass reduction of DDTs in the post-1970 sediments.

In Situ Measurements of Chlorinated Hydrocarbons in the Water Column off the Palos Verdes Peninsula, California

Spatial distributions of DDT and its primary metabolites (DDTs) and polychlorinated biphenyls (PCBs) in the water column off the Palos Verdes Peninsula, CA, were measured in the winter and summer of 1997 using an in situ sampling method. The concentrations of DDTs ranged from 0.6 to 15.8 ng/L, while those of PCBs ranged from 0.06 to 1.14 ng/L at eight sampling stations. The spatial distribution patterns of DDTs and PCBs as well as the DDT/PCB concentration ratio in the water column were similar to those found in the sediment, and the vertical profiles of DDTs and PCBs at both sampling seasons exponentially decreased with increasing distance from the sea floor. In addition, the partitioning characteristics of DDTs and selected PCB congeners indicated a tendency of mobilization from sediment to water. All of these findings strongly suggest that contaminated sediments are a main source of DDT and PCB inputs to the water column surrounding the study site.

Persistent organochlorine contaminants in ringed seals (Phoca hispida) from the Kara Sea, Russian Arctic

AbstractRinged seals collected from the KaraSea in the Russian Arctic during 1995 were analyzed for persistent organochlorines (OCs) such as DDTs, polychlorinated biphenyls (PCBs), chlordane compounds (CHLs), hexachlorocyclohexanes (HCHs), and hexachlorobenzene to understand the present status of contamination. Noticeably higher levels of DDTs and PCBs were detected in ringed seals from the Russian Arctic when the values compared with same species from the Canadian Arctic and the Norwegian Arctic. This suggests the presence of significant local sources of DDTs and PCBs in Russia or nearby areas. Concentrations of CHLs and HCHs in ringed seals were comparable with those in this species elsewhere in circumpolar regions, probably as a consequence of uniform distribution of CHLs and HCHs due to the atmospheric transport of these compounds to the Arctic region. Larga seals collected from the Sea of Okhotsk were also analyzed for OCs to compare residue levels and accumulation patterns with those in ringed seals. In larga seals, the prominent residues were DDTs and PCBs, with levels comparable or slightly lower than those in ringed seals. Lactational transfer of PCBs, DDTs, and CHLs was evident in ringed seals based on increasing concentrations with age in males but not in females. The transfer rates were estimated to be 38% for DDTs, 25% for PCBs, and 30% for CHLs of the whole body burden in the mature female. Comparison of the PCB congener pattern accumulated in seals suggested that ringed seals have an greater capacity to degrade toxic non‐ortho (IUPAC 126) and mono‐ortho (IUPAC 105 and 118) coplanar congeners than did Baikal seals, but a lower capacity than found in larga seals.

95/04216 Polynuclear aromatic hydrocarbons in the United Kingdom environment: A prelimianry source inventory and budget

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.

Persistent Organochlorine Residues in Air, Water, Sediments, and Soils from the Lake Baikal Region, Russia

Contamination of semivolatile organochlorines (OCs) such as hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), DDTs, chlordanes, and polychlorinated biphenyls (PCBs) was assessed in air, water, sediments, and soils from the Lake Baikal region, Russia. Comparison of the residue levels in the lake with those in other regions suggested the presence of local sources of DDTs and PCBs, although the residues were considered to be lower than those in the low-latitude areas in the eastern Asia and Oceania. Larger proportions of p,p'-DDT to total DDTs and similarities of PCB congener compositions to a Russian technical PCB formation were found in the samples analyzed, implying their usages nearby the lake. The estimated fluxes of OCs by gas exchange across the air-water interface applying the two-film model indicated that the lake water plays a role as a sink for HCB, HCHs, and DDTs and also serves as a source for PCBs. The magnitude for PCB volatilization in this lake was found to be smaller than those in the Great Lakes for which the values have been previously reported.

Biological monitoring of environmental contaminants: Chlorinated hydrocarbons in eggs of hens

High concentrations of persistent chlorinated hydrocarbon pesticide residues were detected by gas-liquid chromatography with an electron capture detector ( 3H), in eggs of hens collected from Lucknow under the pesticide monitoring programme. The present study reveals extremely high contamination of eggs, particularly with DDT and HCH residues. The eggs may be an important source of DDT and HCH build-up in the human body. Residue levels of p, p′-DDT and its metabolites p, p′-DDE and α, β and γ-isomers of HCH were higher in eggs of poultry-farm hens compared to those of domestic hens. Egg yolk contained higher levels compared with egg white, because of the lipophilic nature of pesticides and the high lipid content in the yolk. Average levels of total DDT and HCH residues in the yolk and white in the whole egg of a poultry-farm hen were found to be 18.5 and 4.6 μg respectively, whereas the average levels were 7.4 and 4.1 μg, respectively, in the whole egg of a domestic hen.

Residues from past uses of organochlorine insecticides and PCB in waters draining eleven agricultural watersheds in southern Ontario, Canada, 1975–1977

Between May, 1975 and April, 1977 eleven agricultural watersheds ranging in size between 19 and 79 km 2 were studied for residues of persistent organochlorine insecticides and PCB. Stream water, rainwater, sediments, invertebrates and fish were analysed. The presence of DDT, its metabolites and dieldrin, insecticides that had been removed from field application between 1969 and 1972, and PCB, an industrial fire retardant that had been voluntarily restricted to ‘closed system’ use in 1971, were identified. ΣDDT was present in 93% of 949 initial stream waters and 40.6% exceeded a 3 ng/l International Joint Commission (IJC-1977) water quality objective for boundary waters of the Great Lakes. Unit area loading for ΣDDT ranged from 2.9 to 88 mg/ha/yr per watershed. Dieldrin was present in one-fifth of stream waters and 16% exceeded the 1 ng/l IJC (1977) objective. Unit area loading for dieldrin varied from zero to 28 mg/ha/yr per watershed. PCB residues were detected in 94.4% of stream waters at or above 2 ng/l and unit area loading varied from 28 to 269 mg/ha/yr per watershed. DDE and PCB were found in rainwater and this could represent a major source of contamination of PCB. The soil reservoir was the main source of DDT and dieldrin. Accumulations of all three organochlorine compounds in invertebrates and fish were between 10 3 and 10 4 times. None of the fish or invertebrates exceeded the IJC objective of 0.1 μg/g PCB.

Environmental Contamination of Flue-Cured Tobacco with Chlorinated Hydrocarbon Insecticides

AbstractIndirect contamination of tobacco by DDT, TDE, endrin, dieldrin, and toxaphene was investigated under field conditions. Levels of DDT + TDE in soil ranged from &lt;&lt; 0.01 to 0.18 ppm, and those in cured leaves ranged from 0.11 to 1.69 ppm. The lower stalk position at the major test location generally had greater concentrations of DDT + TDE than the middle and upper positions, but distribution of these insecticides among leaf positions was variable for other locations. Residues of DDT in the bottom stalk position were positively correlated with those in the soil. Plant-bed soils did not appear to be a major source of DDT + TDE residues in cured tobacco. Residues of endrin and dieldrin were near or below the limit of detection (0.01 ppm) in soil and cured leaf. Residues of toxaphene ranged from &lt;&lt; 0.1 to 4.7 ppm in soil and &lt;&lt; 0.3 to 7.7 ppm on tobacco. Toxaphene residues in the bottom and top stalk positions were positively correlated with residues in soil. Contamination by toxaphene appeared to be attributable to uptake from soil and to movement of the insecticide as drift or vapour through the air.

Significance of the Food Chain in DDT Accumulation by Fish

Brook trout accumulated approximately 10 times more of the available DDT from the food than directly from the water. Since, in aquatic environments, the concentration of DDT is usually much higher in the food chain than in the water, we suggest that the food chain is the major source of DDT for fish in natural waters.

Chlorinated hydrocarbon insecticides: root uptake versus vapor contamination of soybean foliage.

The major environmental source of DDT (dichlorodiphenyltrichlo-roethane) residues in soybean plants arises from vapor movement from contaminated soil surfaces. In contrast, the presence of dieldrin, endrin, and heptachlor results primarily from root uptake and translocation through stems to leaves and seeds.