Concentrations and inventories of polycyclic aromatic hydrocarbons and organochlorine pesticides in watershed soils in the Pearl River Delta,China

The concentration levels, source, and inventories of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in 55 surface vegetable soils in the watershed of the Pearl River Delta (PRD) were analyzed and compared with those of the surface sediments in the Pearl River Estuary (PRE) and northern South China Sea (SCS). The 16 priority PAHs on US EPA list range from 58 to 3,077 microg/kg (average: 315 microg/kg). The concentrations of DDTs and HCHs range from 3.58 to 831 microg/kg (average: 82.1 microg/kg) and from 0.19 to 42.3 microg/kg (average: 4.42 microg/kg). The ratios of DDT/ (DDD+DDE) are higher than 2 in majority of the soil samples, suggesting that DDT contamination still exists. The PAH ratios suggest that the source of PAHs is petroleum, and combustion of fossil fuel, biomass, and coal. The average concentrations of PAHs and the linear regression slope between PAHs and TOC for the soils and the sediments are quite similar. It was estimated that the soil mass inventories at 0-20 cm depth are 1,292 metric tons for PAHs and 356 metric tons for OCPs in the studied region. The average PAHs inventory per unit area for the soil samples investigated in PRD is about 0.86 time that of surface sediments in the Pearl River Estuary, and about 2.43 times that of surface sediments in the northern South China Sea. PAHs in the soils in PRD have similar source to those of the surface sediments in PRE. All of those may suggest that PAHs in PRE and SCS are probably mainly inputted from the soils in PRD via soil erosion and river transport.     

River water quality and pollution sources in the Pearl River Delta, China

Some physicochemical parameters were determined for thirty field water samples collected from different water channels in the Pearl River Delta Economic Zone river system. The analytical results were compared with the environmental quality standards for surface water. Using the SPSS software, statistical analyses were performed to determine the main pollutants of the river water. The main purpose of the present research is to investigate the river water quality and to determine the main pollutants and pollution sources. Furthermore, the research provides some approaches for protecting and improving river water quality. The results indicate that the predominant pollutants are ammonium, phosphorus, and organic compounds. The wastewater discharged from households in urban and rural areas, industrial facilities, and non-point sources from agricultural areas are the main sources of pollution in river water in the Pearl River Delta Economic Zone.     

Distribution and sources of organochlorine pesticides in sediments of the Xiangjiang River, south-central China

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

Assessment of sampling designs to measure riverine fluxes from the Pearl River Delta, China to the South China Sea

The Pearl River Delta (PRD), located in South China and adjacent to the South China Sea, is comprised of a complicated hydrological system; therefore, it was a great challenge to sample adequately to measure fluxes of organic and inorganic materials to the coastal ocean. In this study, several sampling designs, including five-point (the number of sampling points along the river cross-section and three samples collected at the upper, middle, and bottom parts at each vertical line), three-point (at the middle and two other profiles), one-point (at the middle profile), and single-point (upper, middle, or bottom sub-sampling point at the middle profile) methods, were assessed using total organic carbon (TOC) and suspended particulate matter (SPM) as the measurables. Statistical analysis showed that the three- and five-point designs were consistent with one another for TOC measurements (p > 0.05). The three- and one-point sampling methods also yielded similar TOC results (95% of the differences within 10%). Single-point sampling yielded considerably larger errors than the three- and one-point designs, relative to the results from the five-point design, but sampling at the middle sub-point from the middle profile of a river achieved a relatively smaller error than sampling at the upper or bottom sub-point. Comparison of the sampling frequencies of 12 times a year, four times a year, and twice a year indicated that the frequency of twice a year was sufficient to acquire representative TOC data, but larger sample size and higher sampling frequency were deemed necessary to characterize SPM.     

Passive air sampling of DDT, chlordane and HCB in the Pearl River Delta, South China: implications to regional sources

The Pearl River Delta (PRD) is one of the largest fast-developing economic zones in China. Hong Kong and the mainland part of the PRD differed in socio-economic development history and chemical management policies. Polyurethane foam (PUF)-passive air sampling (PAS) was deployed at 21 regional air quality monitoring stations across the PRD in summer and winter, respectively. Dichloro-diphenyl-trichloroethane (DDT), chlordane and hexachlorobenzene (HCB) were analyzed with GC-MS. High total DDT (240-3700 pg m(-3)) and chlordane (100-2600 pg m(-3)) concentrations were observed. Concentrations of DDTs and chlordane were higher in summer than winter; HCB vice versa. Spatially, the mainland part of the PRD generally displayed higher DDT concentrations than Hong Kong. Antifouling paint for fishing ships in coastal China was suggested to be an important current DDT source in the coast. The reason is unknown for the very low trans-/cis-chlordane (TC/CC) ratios (0.27) found in the mainland in winter. HCB concentrations were relatively uniform across the PRD, and long range transport of HCB from inland/North China to the PRD in winter was suggested.     

Transport and fate of organochlorine pesticides in the River Wuchuan,southeast China

Persistent organic pollutants (POPs) such as chlorinated pesticides are of global concern due to their widespread occurrence, persistence, bioaccumulation and toxicity to animals and human. This paper summarises recent research on 18 chlorinated pesticides in an important catchment in China, by determining their concentrations and behaviour in water, sediment, soil and plants. The concentrations of the total pesticides were in the ranges 187-893 ng l(-1) in river water, 8.53-210 ng g(-1) dry weight in soil, 2.66-13.45 ng g(-1) dry weight in river sediment, and 651-2823 ng g(-1) dry weight in plants. The predominance of beta-HCH as the major isomer of HCHs in all water, soil, sediment and plant samples was clearly observed, due to beta-HCH's resistance to biodegradation. On average beta-HCH accounted for 44%, 53%, 50%, and 46% of the total HCH concentration in water, soil, sediment and plant, respectively. Of the DDTs, DDE accounted for 48%, 43%, 53%, 55% of the total DDT, which suggested that DDT had been transformed to its metabolites, DDE and DDD, of which DDE was the more stable. The chlorinated pesticide levels in the River Wuchuan were generally below the guideline values in China, but some sites displayed levels in excess of EC Environmental Quality Standards for HCHs and DDTs. The results therefore provide important information on the current contamination status of a key agricultural watershed in China, and point to the need for urgent actions to evaluate the long-term fate and toxicity of such persistent compounds and an appropriate remediation strategy.     

Distribution, sources, and potential toxicological significance of PAHs in drinking water sources within the Pearl River Delta

The Pearl River Delta (PRD) region is one of the most population-dense areas in China. The safety of its drinking source water is essential to human health. Polycyclic aromatic hydrocarbons (PAHs) have attracted attention from the scientific community and the general public due to their toxicity and wide distribution in the global environment. In this work, PAHs pollution levels from the drinking source water in nine main cities within the PRD were investigated. ∑15 PAHs concentrations during the wet season varied from 32.0 to 754.8 ng L(-1) in the dissolved phase, and from 13.4 to 3017.8 ng L(-1) in the particulate phase. During the dry season, dissolved PAHs ranged from 48.1 to 113.6 ng L(-1), and particulate PAHs from 8.6 to 69.6 ng L(-1). Overall, ∑15 PAHs concentrations were extremely high in the XC and ZHQ stations during the wet season in 2008 and 2009. In most sites, PAHs originated from mixed sources. Hazard ratios based on non-cancerous and cancerous risks were extremely higher in XC compared with the others during the wet season, though they were much less than 1. Nevertheless, risks caused by the combined toxicity of ∑15 PAHs and other organics should be seriously considered. PAHs toxic equivalent quantities ranged from 0.508 to 177.077 ng L(-1).     

Assessment of organochlorine pesticides and plasticisers in the Selangor River basin and possible pollution sources

A study on the quality of water abstracted for potable use was conducted in the Selangor River basin from November 2008 to July 2009. Seven sampling sites representing the intake points of water treatment plants in the basin were selected to determine the occurrence and level of 15 organochlorine pesticides (OCPs), six phthalate esters (PAEs) and bisphenol A (BPA). Results indicated OCPs were still detected regularly in 66.1 % of the samples with the Σ₁₅OCPs ranging from 0.6–25.2 ng/L. The first data on PAEs contamination in the basin revealed Σ₆PAEs concentrations were between 39.0 and 1,096.6 ng/L with a median concentration of 186.0 ng/L while BPA concentration ranged from <1.2 to 120.0 ng/L. Although di-n-butyl phthalate was detected in all the samples, concentrations of di-ethyl(hexyl)phthalate were higher. Sampling sites located downstream recorded the highest concentrations, together with samples collected during the dry season. Comparison of the detected contaminants with the Department of Environment Water Quality Index (DOE-WQI) showed some agreement between the concentration and the current classification of stream water. While the results suggest that the sites were only slightly polluted and suitable to be used as drinking water source, its presence is cause for concern especially to the fragile firefly “Pteroptyx tener” ecosystem located further downstream.     

Levels and source of organochlorine pesticides in surface waters of Qiantang River, China

Qiantang River is a typical river used for drinking water source, flowing through agricultural area in east China. Surface water samples at 45 sampling sites from the river were collected and analyzed for 13 organochlorine pesticides (OCPs) during six surveys in 2 years of 2005–2006. Sediments, soils, farmland runoff water and dry/wet deposition of this region were also measured for their OCPs residue in order to know possible source of OCPs contamination. The total OCPs concentrations in surface water were 7.68–615.2 ng/l. β-HCH, δ-HCH, Aldrin, Heptachlor, Heptachlor epoxide are the major OCPs in water. The maximum levels of OCPs in water were found in July, while significantly lower OCP concentrations were measured in January. Significant linear correlation was found between the concentration of HCH and that of total 13 OCPs in water. The measured OCP concentrations in sediments, soils, farmland runoff water and dry/wet deposition are discussed in relation to concentrations and patterns found in the surface water. Comparison of OCP levels in sediments and soils led to conclusion that erosion of soil contribute significantly to the contamination of water. The OCPs dry and wet deposition to water body was estimated to 0.49 and 0.86 ton/year, respectively. The ratio of α/γ-HCH and (DDE+DDD)/∑DDT in environmental matrix indicated there probably existed new OCPs input of lindane and dicofol into the river.     

Source apportionment for sediment PAHs using hybrid genetic pattern search treatment of a chemical mass balance receptor model: application to the Pearl River Delta region,China

In order to solve the collinear problem and improve the estimation accuracy of the chemical mass balance (CMB) model which can be essentially regarded as a constrained optimization process, in this study, a hybrid genetic pattern search algorithm (HGPS) was proposed and applied to apportion the source contributions for sediment polycyclic aromatic hydrocarbons (PAHs) in the Pearl River Delta (PRD) region, China. Simulation results with developed synthetic datasets indicated that the estimated source contributions by HGPS were more close to the true values than CMB8.2. Utilizing the HGPS-CMB, residential coal and traffic tunnel were apportioned as the major sources of sediment PAHs in the PRD region. For freshwater surface sediments, the average contribution from residential coal ranged from 32 to 55 %, and traffic tunnel ranged from 13 to 33 %, while the major sources for marine sediments were traffic tunnel (10?~?56 %). These results provide information for developing better PAH pollution control strategies for the PRD.     

Heavy metal pollution in surface soils of Pearl River Delta,China

Heavy metal pollution is an increasing environmental problem in Chinese regions undergoing rapid economic and industrial development, such as the Pearl River Delta (PRD), southern China. We determined heavy metal concentrations in surface soils from the PRD. The soils were polluted with heavy metals, as defined by the Chinese soil quality standard grade II criteria. The degree of pollution decreased in the order Cd?>?Cu?>?Ni?>?Zn?>?As?>?Cr?>?Hg?>?Pb. The degree of heavy metal pollution by land use decreased in the order waste treatment plants (WP)?>?urban land (UL)?>?manufacturing industries (MI)?>?agricultural land (AL)?>?woodland (WL)?>?water sources (WS). Pollution with some of the metals, including Cd, Cu, Ni, and Zn, was attributed to the recent rapid development of the electronics and electroplating industries. Cd, Hg, and Pb (especially Cd) pose high potential ecological risks in all of the zones studied. The soils posing significantly high and high potential ecological risks from Cd covered 73.3 % of UL, 50 % of MI and WP land, and 48.5 % of AL. The potential ecological risks from heavy metals by land use decreased in the order UL?>?MI?>?AL?>?WP?>?WL?>?WS. The control of Cd, Hg, and Pb should be prioritized in the PRD, and emissions in wastewater, residue, and gas discharges from the electronics and electroplating industry should be decreased urgently. The use of chemical fertilizers and pesticides should also be decreased.     

Characteristics of particulate matter pollution in the Pearl River Delta region, China: an observational-based analysis of two monitoring sites

Two-year monitoring data (2006 and 2009), collected at the sub-urban site (WQS) and the background site (TH), were used to study the characteristics of Particulate Matter (PM) pollution in the Pearl River Delta region, China. Similar levels of PM(2.5) concentration measured at both sites seem to confirm that the fine particles have emerged as a major regional pollution issue. The seasonal variation of PM(2.5) concentration is associated with the regional monsoon circulations while the diurnal variation is related to land-sea breeze, traffic emissions and boundary layer development. Negative correlation was found in PM(2.5)-wind speed and PM(2.5)-humidity. Analysis of radiation, temperature and ozone suggests the existence of secondary aerosol formation. Transport effect may be another contributing factor to high PM pollution in the region, such as occasional long-distance dust intrusion and trans-boundary effects from upwind areas.     

Accumulation of heavy metals in leaf vegetables from agricultural soils and associated potential health risks in the Pearl River Delta,South China

This study investigated the extent of heavy metal accumulation in leaf vegetables and associated potential health risks in agricultural areas of the Pearl River Delta (PRD), South China. Total concentrations of mercury (Hg), cadmium (Cd), lead (Pb), chromium (Cr) and arsenic (As) were determined in 92 pairs of soil and leaf vegetable (flowering Chinese cabbage, lettuce, pakchoi, Chinese cabbage, loose-leaf lettuce, and Chinese leaf mustard) samples collected from seven agricultural areas (cities). The bioconcentration factors (BCF) of heavy metals from soil to vegetables were estimated, and the potential health risks of heavy metal exposure to the PRD residents through consumption of local leaf vegetables were assessed. Results showed that among the six leaf vegetables, pakchoi had the lowest capacity for heavy metal enrichment, whereas among the five heavy metals, Cd had the highest capacity for transferring from soil into vegetables, with BCF values 30-fold those of Hg and 50-fold those of Cr, Pb and As. Sewage irrigation and fertilization were likely the main sources of heavy metals accumulated in leaf vegetables grown in agricultural areas of the PRD region. Different from previous findings, soil pH had no clear effect on metal accumulation in leaf vegetables. Despite a certain degree of metal enrichment from soil to leaf vegetables, the PRD residents were not exposed to significant health risks associated with consumption of local leaf vegetables. Nevertheless, more attention should be paid to children due to their sensitivity to metal pollutants.     

Incidence of organochlorine pesticides in soils of Shenzhen, China

To determine the incidence of organochlorine pesticides (OCPs) in soil in a rapid urbanization region, soil samples from various land use types in Shenzhen were collected in winter, 2007. The concentration of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) ranged from non-detected to 149 ng g(-1) and 19 to 88 ng g(-1), respectively. The highest levels of OCPs were observed in soil from traffic and industry areas, reflecting that intensive human disturbance make the soil pollution accumulation more disperse. HCHs and DDTs profiles revealed that the sources were associated mainly with lindane and technical DDTs, respectively, while HCHs in the soil of Shenzhen might originate from both recent and historical sources. The loss of OCPs by soil erosion will enter surface runoff and impose impact on the water environment. Non-dietary exposure estimation indicates that children were the most sensitive group. The average daily exposure to OCPs for males was more serious than for females. Non-dietary exposure to DDTs and HCHs in residential blocks of Shenzhen were far below the acceptable daily intake recommended by the Food and Agriculture Organization/World Health Organization.     

Occurrence and behavior of non-steroidal anti-inflammatory drugs and lipid regulators in wastewater and urban river water of the Pearl River Delta, South China

Occurrence of five non-steroidal anti-inflammatory drugs (salicylic acid, ibuprofen, naproxen, indomethacin and diclofenac) and three lipid regulators (bezafibrate, clofibric acid and gemfibrozil) was investigated in wastewater, sewage sludge, and river water of the urban section of the Pearl River at Guangzhou in South China. Behavior and fate of the pharmaceuticals during treatment in two sewage treatment plants (STPs) were also studied in depth by determining concentrations in the influents and effluents at major treatment units and the sewage sludge. Concentrations of the pharmaceuticals in the raw wastewater were mostly at ng L(-1) levels except salicylic acid whose concentrations ranged from 9.6 to 23.3 μg L(-1). No significant amount of the pharmaceuticals was detected in the suspended particulate matter of wastewater and sewage sludge. Salicylic acid, indomethacin, and naproxen were almost completely removed (≥ 99%); gemfibrozil, ibuprofen and bezafibrate were significantly removed (>75%), whereas diclofenac and clofibric acid were removed by 60-70% during treatment in the STPs. Generally, biodegradation was the governing process for elimination of the investigated pharmaceuticals. Anaerobic biodegradation was responsible for most of the removal of diclofenac whereas aerobic biodegradation also played an important role in elimination of the other pharmaceuticals except SA, which was nearly completely removed after the anoxic process. In the Pearl River, the pharmaceuticals were widely detected. Both the concentrations and detection frequency were higher in March 2008 than those in the other seasons, which may be ascribed mainly to less dilution caused by lower precipitation. Besides the STPs, urban canals directly connected with the Pearl River may also be important contributors to the pharmaceutical contamination in the river.     

Residues of organochlorine pesticides in water and suspended particulate matter from the Yangtze River catchment of Wuhan, China

The residues of 13 organochlorine pesticides (OCPs) in surface water and HCHs and DDTs in suspended particulate matter (SPM) from rivers and lakes in Yangtze River catchment of Wuhan, China, were investigated. The concentration of total OCPs in surface water varied from 1.01 to 46.49 ng l⁻¹ (mean 10.55 ng l⁻¹). The levels of total HCHs (ΣHCH) and total DDTs (ΣDDT) in surface water were in the range of 0.55–28.07 ng l⁻¹ and lower than detection limit to 16.71 ng l⁻¹, respectively, which was lower than Chinese standards on the whole. For OCPs residues in SPM, the mean levels varying from 0.20 to 34.72 ng l⁻¹ and 0.46 to 2.72 ng l⁻¹ for ΣHCH and ΣDDT, respectively, which ranked the relatively higher levels among Chinese studied rivers. Results from this investigation showed that previous excessive usage of technical OCPs was the main reason for the residues of HCHs and DDTs both in surface water and SPM, although some new sources were likely to occurred in the region. Apart from the OCPs in SPM originated from upstream in flood season, one of the important sources of OCP residues both in water and SPM in Yangtze River was supposed to be the inputs of its tributaries. Additionally, in situ water-SPM phase distributions of OCPs indicated that HCHs tended totransport with water as well as DDTs was prone to combine with SPM in Yangtze River catchment of Wuhan.     

Occurrence and behavior of pharmaceuticals, steroid hormones, and endocrine-disrupting personal care products in wastewater and the recipient river water of the Pearl River Delta, South China

The occurrence and behavior of β-blockers, antiepileptic drug carbamazepine and its metabolites, X-ray contrast agent iopromide, natural and synthetic hormones, and several groups of hormone-like personal care products (PCPs), including antiseptics (triclocarban, triclosan, and 2-phenylphenol), parabens and bisphenol A, were investigated in municipal wastewater, sewage sludge, and urban river water of the Pearl River Delta, South China. The pharmaceuticals, natural hormones and PCPs were ubiquitously detected in the raw wastewater from a sewage treatment plant (STP). Only triclocarban and triclosan were detected at significant amounts in the dewatered sludge. Iopromide and the PCPs were greatly removed/transformed from the aqueous phase of the wastewater. The β-blockers were only moderately removed/transformed. Carbamazepine passed through the STP almost unchanged. Biodegradation was the dominant process for elimination/transformation of the pharmaceuticals, hormones, and most PCPs in the STP. However, sorption also played an important role in the fate of triclocarban with nearly 50% of the mass load entering the STP ended up and persisted in the dewatered sludge. The pharmaceuticals, estrone, and PCPs were also widely detected in the Pearl River at Guangzhou. Bisphenol A had the highest concentration. The pharmaceutical concentrations in the Pearl River were higher in March than in May, most likely due to less dilution by lower precipitation. The omnipresence and high levels of the pharmaceuticals and PCPs in the Pearl River may be associated with direct discharge of untreated wastewater and pose potential risks to the ecological system.     

Assessing Impact of Urbanization on River Water Quality In The Pearl River Delta Economic Zone, China

The Pearl River Delta Economic Zone is one of the most developed regions in China. It has been undergoing a rapid urbanization since the reformation and opening of China in 1978. This process plays a significant impact on the urban environment, particularly river water quality. The main goal of this present study is to assess the impact of urban activities especially urbanization on river water quality for the study area. Some Landsat TM images from 2000 were used to map the areas for different pollution levels of urban river sections for the study area. In addition, an improved equalized synthetic pollution index method was utilized to assess the field analytical results. The results indicate that there is a positive correlation between the rapidity of urbanization and the pollution levels of urban river water. Compared to the rural river water, urban river water was polluted more seriously. During the urban development process, urbanization and urban activities had a significant negative impact on the river water quality.     

Tiered aquatic ecological risk assessment of organochlorine pesticides and their mixture in Jiangsu reach of Huaihe River, China

A tiered approach consisting of several probabilistic options was used to refine aquatic ecological risk assessment (ERA) of individuals and mixture of various Organochlorine Pesticides (OCPs) detected in Jiangsu reach of Huaihe River, China. The tiered approach ranged from determined Hazard Quotient (HQ) to Joint Probability Curve and Monte Carlo simulation based HQ-distribution. The results from all levels of ERA methods in the tiered framework are consistent with each other. The results show that Endrin, o,p'-Dichloro-Diphenyl-Trichloroethane (DDT), alpha-Endosulfan and beta-Endosulfan posed clear ecological risk; p,p'-DDT, p,p'-DDD, Aldrin, Heptachlorepoxide and Methoxychlor posed potential risk; while Hexachlorocyclohexanes, Heptachlor, Dieldrin and Hexachlorobenzene posed negligible risk. Further, based on the concept of total equivalent concentration, combined ecological risk caused by the mixture of all detected OCPs was calculated, and it proved to be significantly higher than the risk caused by any individual OCP. Despite inevitable uncertainties in current ERA, a comprehensive tiered approach can help to get a more credible result of risks of individuals and mixture of hazardous pollutants and screen the major risk pollutants contributing to the combined ecological risk.     

Regional differences and sources of organochlorine pesticides in soils surrounding chemical industrial parks

Concentrations of organochlorine pesticides (OCPs; dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB)) were investigated in 105 soil samples collected in vicinity of the chemical industrial parks in Tianjin, China. OCP concentrations significantly varied in the study area, high HCH and DDT levels were found close to the chemical industrial parks. The intensity of agricultural activity and distance from the potential OCP emitters have important influences on the OCP residue distributions. Principal component analysis indicates that HCH pollution is a mix of historical technical HCH and current lindane pollution and DDT pollution input is only due to technical DDT sources. The significant correlations of OCP compounds reveal that HCHs, DDTs and HCB could have some similar sources of origin.