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Occurrence and possible sources of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Chao River, China
Chemosphere 114 (2014) 136–143
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Occurrence and possible sources of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Chao River, China Yang Yu a, Yingxia Li a,⇑, Zhenyao Shen a, Zhifeng Yang a, Li Mo b, Yanhong Kong b, Inchio Lou c a
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China China Academy of Urban Planning & Design, Beijing 100044, China c Department of Civil and Environmental Engineering, University of Macau, Macau SAR, China b
h i g h l i g h t s DDTs, HCHs, HCB are the dominant OCPs and PCB-118 is the major PCB. OCP level is higher in corn fields and orchards and lower in forests and grasslands. OCPs in soil came from new use of lindane and old application of DDTs, HCB, etc. PCBs primarily come from atmospheric deposition. Proper management of lindane, DDTs, HCB is critical for the water resource quality.
a r t i c l e
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Article history: Received 21 October 2013 Received in revised form 19 March 2014 Accepted 30 March 2014
Handling Editor: H. Fiedler Keywords: Agricultural soil Chao River Lindane Miyun Reservoir Organochlorine pesticides (OCPs) Polychlorinated biphenyls (PCBs)
a b s t r a c t To analyze the possible influence of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) on Miyun Reservoir, 14 soil samples and 1 water sample were collected along the Chao River, which is the main upstream source of the reservoir. A total of 24 kinds of OCPs and 12 kinds of P dioxin-like PCBs were measured. Results showed that the OCPs concentration ranged from 0.8145 to P 1 16.8524 ng g , and the PCBs ranged from 0.0039 to 0.0365 ng g1. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were the three dominant kinds of OCPs in this region, and the majority component of the PCBs was PCB-118 in both water and soil samples. The OCP ratios suggest that new inputs of lindane exist. DDTs mainly come from old technical inputs. HCHs might come from a new application of lindane, which highlights the importance of prohibited pesticide control. OCP concentrations were higher in corn fields and orchards and lower in forest lands and grasslands, which indicated that OCPs were very much influenced by human activities. The proportion of PCB components in this study area suggested that they mainly came from atmospheric deposition. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Organochlorine compounds (OCs) such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in soil and aquatic environment are obtaining increasing global concern (Zhou et al., 2001, 2006; Zhang et al., 2004; Feng et al., 2011) because of their persistence, toxicity and bioaccumulation (Tanabe et al., 1994; Jones and De Voogt, 1999). OCs can be transported from air to surface soil and water by dry and wet deposition, from soil to aquatic bodies by rainfall runoff, and from soil and aquatic bodies back to air by volatilization. Due to the ⇑ Corresponding author. Tel./fax: +86 10 58804585. E-mail address: [email protected] (Y. Li). http://dx.doi.org/10.1016/j.chemosphere.2014.03.095 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
long-range atmospheric transport, OCs have been found in most areas of the world (Kong et al., 2005; Castro-Jiménez et al., 2008; Zhang et al., 2008; Zhao et al., 2010; Wang et al., 2012; Barakat et al., 2013; Gao et al., 2013b). They greatly affect the qualities of water, soil, air and even human health. Included in the group of OCPs are dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), dieldrin, endrin, aldrin, isodrin, heptachlor, heptachlor epoxide A, heptachlor epoxide B, hexachlorobenzene (HCB), oxychlordane, trans-chlordane, a-endosulfan, b-endosulfan, cis-chlordane and methoxychlor. DDTs and HCHs were dominant OCPs produced and utilized in China from 1950 to 1983 owing to their high efficiency, low cost, broad-spectrum pesticidal efficacy. Due to their persistence, bioaccumulation and toxicity, the ban on the production of technical
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HCHs and DDTs was effective on April 1st, 1983. Until then, about 4.9 million tons of HCHs and 0.4 million tons of DDTs had been used for agriculture in China (Hua and Shan, 1996). From 1991, China started the industrial production of lindane (c-HCH) for export and restricted usage on certain crops (Li et al., 2001). Lindane has been mainly used to kill locus, wheat mole cricket, midges, and wood moth. Although the use and production of DDTs and HCHs have been banned since 1983 in China, high residual levels can still be frequently detected in various environmental media (Yang et al., 2008a; Yang et al., 2008b; Xie et al., 2012). After 1983, approximately 11 400 tons of lindane was still reportedly being produced (Li et al., 2001), and DDTs have been continuously produced for approximately 20 years owing to export demands, malaria control and dicofol production (Yang et al., 2008a). Until now lindane is still produced and used in China. In theory, PCBs could have 209 possible congeners according to the number and position of their chlorine atoms. Among these 209 possible congeners, 12 kinds of dioxin-like PCBs are typical hormonal substances, which are able to induce adverse effects on human skin, liver, gastrointestinal systems, immune systems and others. Approximately 10 000 tons of PCBs were produced from 1965 to 1974 in China, which accounts for 1% of global production(Zheng et al., 2010) and the low chlorinated congeners PCBs are the dominant components (Xing et al., 2005). As for China, the production of PCBs was totally stopped in 1974, whereas PCBs still exist in many industrial process and byproducts. PCBs have been found in paints, dyed paper and plastics, heat exchange fluids in transformers and capacitors, and sealants. PCBs are also used as additives in pesticides. As the major OC sink, agricultural soil (Tao et al., 2005; Sun et al., 2009) was the primary target of many OC studies. Information regarding OC pollution in soil along rivers and reservoirs is especially important due to the high probability of flushing into the surrounding water bodies in rainy days (Kim et al., 2005; Herngren et al., 2006; Kang et al., 2010). Miyun Reservoir is the major surface drinking water resource for Beijing and its water quality is crucial to people’s health. Chao River is the main inflow of the Miyun Reservoir. The region along the lower reach of Chao River is predominantly agricultural lands with many country people living there. Non-point sources are the major pollution sources for Miyun Reservoir, which have exceeded the amount from point sources (Ou and Wang, 2008; Li et al., 2013). The OCs in soil can be
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migrated by volatilization, degradation, and leaching process to deeper soil layers or even groundwater, and flushing into surrounding water bodies. In this study, water and soil samples along the lower reach of Chao River were collected. The concentrations of OCPs and PCBs were determined to understand the potential OC pollution risk to Miyun Reservoir. 2. Materials and methods 2.1. Study area and sampling method A total of 15 samples were collected in October 2011, with 1 water sample from Chao River near Xiaocaocun (Fig. 1), about 12 km away from the entrance into Miyun Reservior. The other 14 soil samples were taken from lands along the lower reach of Chao River. The sampling lands include corn field (n = 5), orchard (n = 3), forest land (n = 3) and grassland (n = 3). The sampling site locations are shown in Fig. 1. Surface soil samples were collected using a metal shovel. The sampling depth was about 15 cm with relative loose soil that tends to be moved by the rainfall wash-off. Three subsamples were collected at each site within a 1 m2 area and bulked together to form one composite soil sample. Then the bulked sample was sealed in a clean polyethylene plastic bag and transported to the laboratory. All of the soil samples were air-dried for 3 weeks before analysis. At site 15 as shown in Fig. 1, 8 L water sample was collected and stored in 2 glass bottles, then transported back to the laboratory immediately. 2.2. Reagents The standard mixture solution for 24 OCPs, including a-, b-, cand d-HCH, O,P0 -DDE, O,P0 -DDD, P,P0 -DDE, P,P0 -DDT, O,P0 -DDT, P,P0 -DDD, dieldrin, endrin, aldrin, isodrin, heptachlor, heptachlor epoxide A, heptachlor epoxide B, HCB, oxychlordane isomer, trans-chlordane, cis-chlordane, a-endosulfan, b-endosulfan and methoxychlor was obtained from AccuStandard Company, USA. The standard mixture solution for 13 12C12-PCBs, including PCB-77, 105, 114, 118, 123, 126, 138, 153, 156, 167, 169, 180 and 189, was obtained from Labor Dr. Ehrenstorfer. The internal OCP
Fig. 1. Locations of sampling sites along the lower reach of Chao River.
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standards (13C6hexachlorobenzene, 13C6b-HCH, 13C6c-HCH, 13C10 trans-nonachlor, 13C12p, p0 -DDE, 13C10mirex and 13C12dieldrin) and PCBs (13C12PCB-77, 81, 105, 114, 118, 123, 126, 157, 159, 167, 169, 170, 180 and 189) were all purchased from Cambridge Isotope Laboratories. All of the solvents (hexane, acetone and dichloromethane) used for sample processing and analysis were of chromatography grade.
2.3.2. Water sample Water sample was filtered and then adsorbed by Amberlite XAD-2. The Amberlite XAD-2 with the internal standard was Soxhlet extracted. The extraction and purification methods were the same as the methods for soil samples indicated above.
2.3. Sample extraction and clean-up
The concentrated OCP and PCB extracts were identified and quantified using GC–MS (gas chromatography–mass spectrometry) with a DB-5MS chromatographic column (30 m 0.25 mm, i.d. 0.1 lm, Agilent Technologies, Palo Alto, CA, USA). For OCPs, an oven program started at 80 °C for 3 min, and then increased to 260 °C at a rate of 6 °C min1. For PCBs, the oven temperature was set at 100 °C and maintained for 3 min, and then increased to 250 °C at a rate of 5 °C min1.
2.3.1. Soil samples A 10.00 g sub-sample was homogenized with 100 lL of internal standard (20 ng g1) and then Soxhlet extracted with a 1:1 (V:V) hexane and acetone solvent mixture (200 mL) for 24 h for OCP extraction. The extract was concentrated by a rotary evaporator to approximately 1 mL. An aluminum/silica gel column (1.2 cm 40 cm) was used to clean up and fractionate the extract. The column was flushed with 30 mL of hexane and then eluted with approximately 100 mL of hexane/dichloromethane (70:30, V:V). The fraction was re-concentrated by a rotary evaporator and further concentrated to 100 lL under a gentle stream of highly pure nitrogen gas. The PCB extraction was similar to the OCP extraction method. A 10.00 g sub-sample was mixed with 40 lL of the internal standard (16 ng g1) and Soxhlet extracted with a 1:1 (V:V) hexane and acetone solvent mixture (200 mL) for 24 h for PCB extraction. The extract was concentrated by a rotary evaporator to approximately 1 mL. The extract was purified using a multilayer silica gel column (1.5 cm 40 cm) and fractionated. The column was flushed with 50 mL of hexane and eluted with approximately 100 mL of hexane/dichloromethane (97:3, V:V). The solvent was then reduced to 100 lL.
2.4. Gas chromatography–mass spectrometry analysis
3. Results and discussion 3.1. Occurrence of OCPs P The concentration of OCPs, which stands for the sum of 24 kinds of OCPs examined in this study, in the water sample was 5.33 ng L1. The concentrations of the main contents including DDTs, HCHs and HCB were 2.19, 1.57 and 1.32 ng L1 comprising P 41%, 30% and 25% of the OCPs, respectively. The occurrences of DDTs, HCHs and HCB demonstrate the influence of pesticide usage in the upstream watershed of Chao River. The b-HCH concentration of 0.805 ng L1 in the water sample was higher than the a, c and d-HCH concentrations of 0.12, 0.5, 0.149 ng L1, respectively as demonstrated in Fig. 2. Higher b-HCH concentration is commonly found in water bodies since the a, c-HCH are easily degraded
Fig. 2. Concentrations of individual OCP in soil and water samples along the lower reach of Chao River.
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and d-HCH is the most easily adsorbed. In the water sample, O,P0 -DDD, dieldrin, endrin, aldrin, isodrin, heptachlor, heptachlor epoxide (isomer A), heptachlor epoxide (isomer B), oxychlordane isomer and a-endosulfan were all lower than detection limits. The other 14 OCPs were detected with very low concentrations of cis-chlordane and b-endosulfan as shown in Fig. 2. More OCP categories were detected in soil samples except for dHCH, dieldrin, endrin, aldrin, isodrin, heptachlor epoxide (isomer A), oxychlordane isomer and methoxychlor. The mean, minimum P and maximum concentrations of OCPs in soil samples were 1 4.84, 0.81 and 16.85 ng g . There were two or three orders of magnitude in difference among the sites for c-HCH, P,P0 -DDE as shown in Fig. 2. The great OCP content difference among sites demonstrated that anthropogenic activities brought different amount of OCPs to different kinds of land uses and different sites in the same watershed. It is important to know these differences and make different management strategies for different land uses. The highest P OCPs level was found in corn field from site 10, which might be caused by heavy dose of pesticide in corn fields. Among the soil OCPs, DDTs, HCHs and HCB were the most dominant compounds, accounting for 61%, 27% and 11%, which were similar to the water sample. In the agriculture soil, DDTs, HCHs and HCB mainly come from the old and new use of pesticides, which can be flushed into rivers when it rains. O,P0 -DDE, O,P0 -DDD, P,P0 -DDE, P,P0 -DDT and O,P0 -DDT + P,P0 -DDD P were all detected in the soil and water samples. The DDTs (the 0 0 0 0 sum of P,P -DDE, P,P -DDT and O,P -DDT + P,P -DDD) concentration in soil samples ranged from 0.1835 to 15.7150 ng g1 as shown in Fig. 2, which was lower than the national soil safety standards for P level one (50 ng g1, GB, 1995). The DDTs concentration fluctuated among different sites, with the highest concentration found in S10 corn field and the lowest concentration found in S3 forest land. This further demonstrated that DDTs in this region mainly came from human activities. In terms of the measured individual DDT, the detection frequencies for 14 soil samples were higher than
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83% (Fig. 2), indicating wide occurrence and persistence of DDTs in this region. P As shown in Fig. 2, the HCH (the sum of a-, b-, c- and d-HCH) concentration ranged from 0.1162 to 6.0188 ng g1 with a mean of 1.3063 ng g1. In the soil samples, c-HCH was the dominant HCH, with a mean value of 1.1416 ng g1, followed by b-HCH and a-HCH. This HCH distribution is different from water sample with the dominance of b-HCH and certain amount of c-HCH. The degradation rate of c-HCH is influenced by the characteristics of soil and the average half-life period is two months. Therefore the HCHs in water sample should come from the previous rainfall runoff and river sediment release, both of which contained older application of HCHs. Whereas the HCHs in soil samples come from both recent and precious HCH applications. In Fig. 2, the detection frequencies of a-, b- and c-HCH were all 100%, and the d-HCH concentrations of all samples were lower than the detection limit. The highest a-, band c-HCH concentrations occurred in S9 and S12, both of which were corn field. This indicates the critical effect of land use type P on HCH concentrations in soil. Whereas all the HCHs concentrations were lower than the national soil safety standards for level one (50 ng g1, GB, 1995). The concentration of HCB in the water sample was 1.323 ng L1. The HCB concentrations in soil samples were within a range of 0.2221–1.2716 ng g1, with a mean of 0.5561 ng g1. The highest soil sample HCB concentration occurred in S2 (grassland) with a value of 1.2716 ng g1, which might be due to the drowning in rainy season at S2. 3.2. Occurrence of PCBs In the water sample, only two kinds of PCBs, namely PCB-105 and PCB-118, were detected. In soil samples, 12 kinds of dioxinlike PCBs were investigated, among which 9 kinds were detected and PCB-81, 114 and 157 were lower than the detection limits as P shown in Fig. 3. The concentration of PCBs, which stands for
Fig. 3. Concentrations of individual PCB in soil and water samples along the lower reach of Chao River.
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the sum of 12 kinds of PCBs examined in this study, ranged from 0.0039 to 0.0365 ng g1, with an average of 0.0150 ng g1. The PCB-118 concentration ranged from 0.0010 to 0.0272 ng g1 with a mean of 0.0068 ng g1. PCB-118 was the dominant PCB with the highest concentration in all the dioxin-like PCBs. It was the only component detected 100%, followed by PCB-105. PCBs in the surface soils and waters mainly come from dry and wet deposition, surface runoff, and industrial wastes (Hiller et al., 2011). Although some PCBs are used as additives to produce pesticides such as HCHs and trichlorophenol (Que, 2007), the amount of PCBs added is very small compared with other sources. Therefore direct application of PCBs on crops can be ignored. In China, 90% of PCBs was primarily used in power capacitors and 10% was mainly used as a paint additive (Zhang et al., 2008). PCB-105 and PCB-118 were the major components of PCBs in both soil and water samples in this study, which indicated that PCBs in soil and water might come from similar sources. In this study area, no PCB storage or production industries have ever existed. Therefore PCBs in this region may mainly come from atmospheric deposition. 3.3. Distribution of OCPs and PCBs with different land uses P P The mean concentrations of OCPs and PCBs for individual land use were plotted in Fig. 4. Higher mean concentrations of P OCPs were found in corn fields and orchards and lower mean P concentrations of OCPs in forests and grasslands, indicating that stronger human activities in corn fields and orchards caused higher P OCPs concentrations. More inputs of pesticides and fertilizers in corn fields and orchards raised the level of OCPs.
Fig. 4. Mean concentrations of
P P OCPs and PCBs for different land uses.
P The mean PCBs distribution with land uses was different from P P that of OCPs. Mean concentration of PCBs in grasslands was the highest among these four land uses. This is because the grasslands are often submerged in water in rainy season so that the grassland samples contain both soil and sediments, which can absorb the PCBs in water. PCBs are easily adsorbed to soil organic matter and difficult to be flushed. Higher mean concentrations of P PCBs in orchards and forest lands may be due to the larger leaf surface area, which can receive more deposition of PCBs from the atmosphere. The particles with PCBs on leaves will be flushed to the ground in rainy days. 3.4. Possible sources of OCPs and PCBs Isomer ratios were analyzed to obtain further insights of the possible pollution sources. Technical HCHs contain 60–70% aHCH, 5–12% b-HCH, 10–12% c-HCH and 6–10% d-HCH, and the lindane is composed of pure c-HCH (>99%) (Iwata et al., 1993). Therefore the ratio of a-HCH/c-HCH is relatively stable with a value of 4.64–5.83 for technical HCHs and nearly zero for lindane (Zhang et al., 2004). Additionally, this ratio could increase with the environmental degradation process since a-HCH and c-HCH are easily degraded in the environment. Among the four kinds of HCHs, b-HCH is the most stable and hardest to degrade. In this study, the a-HCH/c-HCH ratios of 14 soil samples ranged from 0.002 to 0.796 with a mean of 0.138 as shown in Table 1. It can be concluded that HCH residuals in soil in this area primarily came from a newer use of lindane and old technical HCH residuals. The a-HCH/c-HCH ratio of the water sample is 0.240. The ratios between the parent compound and its metabolites can provide useful information on the pollution sources. Technical DDTs generally contain 75% P,P0 -DDT, 15% O,P0 -DDT, 5% P,P0 -DDE, and less O,P0 -DDE, P,P0 -DDD and O,P0 -DDD. The O,P0 -DDT/P,P0 -DDT ratio can be used to distinguish DDT pollution caused by technical DDTs from that of dicofol. The value of O,P0 -DDT/P,P0 -DDT ranges from 0.2 to 0.3 in technical DDTs and from 1.3 to 9.3 or higher in dicofol (Qiu et al., 2005). In this study, the concentration of O,P0 DDT + P,P0 -DDD was identified instead of individual O,P0 -DDT and P,P0 -DDD. So the ratio of (O,P0 -DDT + P,P0 -DDD)/P,P0 -DDT was calculated and this ratio was mostly lower than 0.3 with the exception of S3, S6 and S14 as shown in Table 1. This finding indicated that technical DDTs were the main source for most of the study area. More ratios among OCPs can also be used to indicate the sources of OCPs. When heptachlor epoxide/heptachlor is larger
Table 1 Ratios of different OCP concentrations for 15 sampling sites. Sites
a-HCH/cHCH
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15
0.030 0.112 0.017 0.002 0.012 0.034 0.195 0.164 0.110 0.247 0.796 0.009 0.204 0.007 0.240
(O,P0 -DDT + P,P0 -DDD)/P,P0 DDT n.n. 0.162 0.430 0.205 0.179 0.342 0.147 0.239 0.228 0.110 – 0.231 0.145 1.328 0.074
P,P0 -DDE/P,P0 DDT n.n. 0.054 0.306 0.059 0.603 0.061 0.139 0.103 0.805 0.956 0.033 0.091 0.017 0.379 0.101
Heptachlor epoxide/ heptachlor *
0 0* 0* 0* n.n. n.n. n.n. n.n. 1.136 – n.n. – 0* 0* n.n.
cis-Chlordane/transchlordane
a-Endosulfan/b-
0.606 0.115 n.n. n.n. 0* n.n. 0* n.n. 0* 0* n.n. 0* n.n. n.n. 0.084
1.352 8.966 n.n. 0.361 n.n. n.n. 4.458 n.n. n.n. n.n. n.n. n.n. n.n. 1.586 0*
n.n.: The denominator and numerator are all lower than the detection limits. 0*: The numerator is lower than the detection limit whereas the denominator is higher than the detection limit. –: The denominator is lower than the detection limit whereas the numerator is higher than the detection limit.
endosulfan
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– 0.5–32.5 0.19 13–407 n.d.–19.73 – 0.2–25.6 – n.d.–40 n.d.–9.12 – 0.3–70.6 1.4 36–574 n.d.–5.1 0.08–187.8 0.8–44.2 2.3 – n.d.–1.8 6.2–11.95 2.7–12.3 – – n.d.–4.51 n.d.–0.9 0.4–129.6 0.06 – n.d.–0.74 Delhi, India (n = 9) Sugarcane crop soils, Mexico (n = 63) UK (n = 3) Garden soil of Waikato, New Zealand (n = 5) Indo–Gangetic, alluvial plains, India(n = 31)
– – Flooded soils of Florida, USA (n = 10)
–
– 0.38–4.76 – 1.93–34.65 – 0.9–8.79 Around Taihu Lake, China (n = 13) Wuchuan, China # (n = 56)
n.d.–1.37 n.d.–1.41 n.d.–2.67 n.d.–2.74 n.d.–1.10 n.d.–0.78 Around Guanting Reservoir, China # (n = 30) Around Guanting Reservoir, China # (n = 56)
0.3–1.07 0.27–1.32 0.09–3.61 0.1–2.31 0.32–0.96 0.24–1.01
– – –
Along Jinjiang River, China #(n = 8)
Around Hongze lake, China (upland field, n = 22) Along Mulan River, China# (n = 17) Along Qiulu River, China # (n = 8)
0.0225– 5.8610 0.09–1.57 0.0020– 0.0954 0.12–2.06 Along Chao River, China# (n = 14)
0.0223– 0.3484 n.d.-2.20
c-HCH b-HCH
a-HCH Area
To understand more regarding the OC level in this region, the HCH and DDT concentrations from this study are compared with similar studies on soil samples from other areas (Marburger et al., 2002; Zhang et al., 2002; Feng et al., 2003; Wang et al., 2005; Zhang et al., 2005; Singh et al., 2007; Zhang et al., 2011; Yang et al., 2013; Gao et al., 2013a) as shown in Table 2. The concentrations of a-HCH and b-HCH in this study are lower than those of other regions, primarily as a consequence of lower past use in this region. The highest concentration of c-HCH is nearly four times higher than in most other water resource regions in China. This indicates that the new use of lindane in the Chao River area should be given more attention. Whereas in other countries especially developing countries such as India, the highest concentration of c-HCH is 187.8 ng g1, which is much higher than other regions. P As for the HCHs in this study, its concentration is at a medium level compared with other water resource areas. When compared P with the Guanting Reservoir area, the concentration of HCHs is at a similar pollution level. Guanting Reservoir was not able to serve as the drinking water resource for Beijing from 1997 due to its deteriorated water quality and resumed to be mainly industrial water resource for Beijing after restoration. Therefore, pesticide control measures should be implemented in the Chao River region to reduce further pollution to Miyun Reservoir. DDT concentrations in the study region are moderate in comparison with other water resource area, and much lower than the non-water resource places such as garden soil. Complex anthropogenic pollution exists in this study area.
Table 2 HCH and DDT concentrations of surface soil samples from different regions worldwide (ng g1).
3.5. Comparative analysis
#: Soil samples were collected around water resource regions. n.d.: Lower than the detection limit. –: No data available.
– – 0.37 n.d.–111 n.d.– 42.39 6.4–199.8 – – – 0.08–7.25 n.d.–3.6 4.3–4.6 – – n.d.–2.71
0.7 –
– – – 70–1160 n.d.–74.06
Marburger et al. (2002) Prakash et al. (2004) Velasco et al. (2012) Meijer et al. (2001) Gaw et al. (2006) Singh et al. (2007) – 0.7
Feng et al. (2003) Zhang et al. (2002) n.d.–5.3 – – 0.88–6.88
– 0.55– 7.38 0.7 n.d.–3.4 –
– 1.13– 12.69 –
–
n.d.–44.82 n.d.–52.2 n.d.–3.93 n.d.–3.55
n.d.–8.96 n.d.–7.33
n.d.–5.84 n.d.– 39.09 – –
– 0.93–10.28
Zhang et al. (2005) Wang et al. (2005) n.d.–94.07 n.d.–57.9 n.d.–39.8 n.d.–33.08
Zhang et al. (2011) Zhang et al. (2011) 0.91–27.89 1.24–10.04 0.22–8.01 0.03–4.26
n.d.–3.4 0.01– 1.23 n.d.–7.54 n.d.–3.37 0.47–7.32 0.03–17.05 n.d.–5.09 0.14–5.44 1.22–7.47 0.96–4.11 0.42–3 0.35–1.31
Gao et al. (2013a) n.d.–73.55 – n.d.–20.43 –
n.d.–9.99 0.2–2.29
–
0.19– 3.96 –
–
Yang et al. (2013)
0.1835– 15.7150 1.77–25.03 0.1019– 7.6067 0.38–7.55 –
0.0145– 7.2697 0.27–10.04 –
0.1162– 6.0188 0.41–6.78
Reference d-HCH
P HCHs
O,P0 -DDT
P,P0 -DDE
than 1, heptachlor contamination most likely originates from older uses of heptachlor (Jiang et al., 2009). In S9, S10 and S12, the heptachlor mainly came from older uses related to the development of agriculture. If the ratio of cis-chlordane/trans-chlordane is larger than 1, the origin is an older use (Bidleman et al., 2002). In this study, S1, S2 and S15 showed a newer input from chlordane. In technical endosulfan, there are 70% a-endosulfan and 30% b-endosulfan, and a-endosulfan is more easily degraded. S2 and S7 had values that were clearly larger than 2.33, suggesting that they came from a newer endosulfan use. The mean PCB proportions of 14 soil samples are shown in Fig. 5. PCB-118 was the dominant component of PCBs, which was similar to other studies (Park et al., 2010; Chavhan et al., 2012). The PCBs produced in China were mainly composed of low chlorinated congeners (Zhang et al., 2008). There were no PCB production factories or storage in this region in history and the PCBs mainly originated from atmospheric deposition.
n.d.
P DDTs P,P0 -DDT P,P0 -DDD
Fig. 5. Mean individual PCB proportion of 14 soil samples.
This study
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4. Conclusions Along the lower reach of Chao River, DDTs, HCHs and HCB were the dominant OCPs in soil and water samples. The concentrations of OCPs varied greatly with different sites with up to two to three orders difference forc-HCH, P,P0 -DDE. Human activities greatly influence the OCP inputs to different sites. OCP concentrations were higher in orchards and corn fields and lower in forest lands and grasslands. The concentration of c-HCH was higher than in most other water resource areas. New input of c-HCH exists in this region indicating recent application of prohibited pesticides such as linane, which highlights the importance of pesticide control in this region. DDT ratio analysis indicated that the DDTs at most sites came from older uses of technical DDTs. The PCBs in this area primarily came from atmospheric deposition, and PCB-118 was the main component. Similar OC concentration distribution in soil and water samples suggested that the OCs in water mainly originated from soil flushing by rain. Acknowledgements This research is supported by the National Science Foundation for Innovative Research Group (Grant 51121003), the National Science Foundation of China (Grant 51278054) and the FST Short Term PD & VF Scheme 2013 and MYRG072(Y1-L2)-FST13-LIC from University of Macao. The authors are grateful for these supports. References Barakat, A.O., Khairy, M., Aukaily, I., 2013. Persistent organochlorine pesticide and PCB residues in surface sediments of Lake Qarun, a protected area of Egypt. Chemosphere 90, 2467–2476. Bidleman, T.F., Jantunen, L.M.M., Helm, P.A., Brorström-Lundén, E., Juntto, S., 2002. Chlordane enantiomers and temporal trends of chlordane isomers in arctic air. Environ. Sci. Technol. 36, 539–544. Castro-Jiménez, J., Deviller, G., Ghiani, M., Loos, R., Mariani, G., Skejo, H., Umlauf, G., Wollgast, J., Laugier, T., Héas-Moisan, K., Léauté, F., Munschy, C., Tixier, C., Tronczyn´ski, J., 2008. PCDD/F and PCB multi-media ambient concentrations, congener patterns and occurrence in a Mediterranean coastal lagoon (Etang de Thau, France). Environ. Pollut. 156, 123–135. Chavhan, C., Sheikh, J., Algiwale, T., Thokchom, B., Thacker, N., 2012. Releases of dioxin-like PCBs in water, soil and residue produced from high thermal processes and waste incinerators. Bull. Environ. Contam. Toxicol. 89, 537–541. Feng, J., Zhai, M., Liu, Q., Sun, J., Guo, J., 2011. Residues of organochlorine pesticides (OCPs) in upper reach of the Huaihe River, East China. Ecotoxicol. Environ. Saf. 74, 2252–2259. Feng, K., Yu, B.Y., Ge, D.M., Wong, M.H., Wang, X.C., Cao, Z.H., 2003. Organo-chlorine pesticide (DDT and HCH) residues in the Taihu Lake Region and its movement in soil–water system: I. Field survey of DDT and HCH residues in ecosystem of the region. Chemosphere 50, 683–687. Gao, J., Zhou, H., Pan, G., Wang, J., Chen, B., 2013a. Factors influencing the persistence of organochlorine pesticides in surface soil from the region around the Hongze Lake, China. Sci. Total Environ. 443, 7–13. Gao, S., Chen, J., Shen, Z., Liu, H., Chen, Y., 2013b. Seasonal and spatial distributions and possible sources of polychlorinated biphenyls in surface sediments of Yangtze Estuary, China. Chemosphere 91, 809–816. Gaw, S.K., P Wilkins, A.L., Kim, N.D., Palmer, G.T., Robinson, P., 2006. Trace element and DDT concentrations in horticultural soils from the Tasman, Waikato and Auckland regions of New Zealand. Sci. Total Environ. 355, 31–47. GB, 1995. Soil environmental quality standard (GB15618-1995). (in Chinese). Herngren, L., Goonetilleke, A., Ayoko, G.A., 2006. Analysis of heavy metals in roaddeposited sediments. Anal. Chim. Acta 571, 270–278. Hiller, E., Zemanová, L., Sirotiak, M., Jurkovicˇ, L.U., 2011. Concentrations, distributions, and sources of polychlorinated biphenyls and polycyclic aromatic hydrocarbons in bed sediments of the water reservoirs in Slovakia. Environ. Monit. Assess. 173, 883–897. Hua, X., Shan, Z., 1996. The production and application of pesticides and factor analysis of their pollution in environment in China. Adv. Environ. Sci. 4, 33–45 (in Chinese). Iwata, H., Tanabe, S., Sakai, N., Tatsukawa, R., 1993. Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of ocean on their global transport and fate. Environ. Sci. Technol. 27, 1080–1098. Jiang, Y., Wang, X., Jia, Y., Wang, F., Wu, M., Sheng, G., Fu, J., 2009. Occurrence, distribution and possible sources of organochlorine pesticides in agricultural soil of Shanghai, China. J. Hazard. Mater. 170, 989–997. Jones, K.C., De Voogt, P., 1999. Persistent organic pollutants (POPs): state of the science. Environ. Pollut. 100, 209–221.
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Occurrence and possible sources of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) along the Chao River, China Yang Yu a, Yingxia Li a,⇑, Zhenyao Shen a, Zhifeng Yang a, Li Mo b, Yanhong Kong b, Inchio Lou c a
State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China China Academy of Urban Planning & Design, Beijing 100044, China c Department of Civil and Environmental Engineering, University of Macau, Macau SAR, China b
h i g h l i g h t s DDTs, HCHs, HCB are the dominant OCPs and PCB-118 is the major PCB. OCP level is higher in corn fields and orchards and lower in forests and grasslands. OCPs in soil came from new use of lindane and old application of DDTs, HCB, etc. PCBs primarily come from atmospheric deposition. Proper management of lindane, DDTs, HCB is critical for the water resource quality.
a r t i c l e
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Article history: Received 21 October 2013 Received in revised form 19 March 2014 Accepted 30 March 2014
Handling Editor: H. Fiedler Keywords: Agricultural soil Chao River Lindane Miyun Reservoir Organochlorine pesticides (OCPs) Polychlorinated biphenyls (PCBs)
a b s t r a c t To analyze the possible influence of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) on Miyun Reservoir, 14 soil samples and 1 water sample were collected along the Chao River, which is the main upstream source of the reservoir. A total of 24 kinds of OCPs and 12 kinds of P dioxin-like PCBs were measured. Results showed that the OCPs concentration ranged from 0.8145 to P 1 16.8524 ng g , and the PCBs ranged from 0.0039 to 0.0365 ng g1. Dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and hexachlorobenzene (HCB) were the three dominant kinds of OCPs in this region, and the majority component of the PCBs was PCB-118 in both water and soil samples. The OCP ratios suggest that new inputs of lindane exist. DDTs mainly come from old technical inputs. HCHs might come from a new application of lindane, which highlights the importance of prohibited pesticide control. OCP concentrations were higher in corn fields and orchards and lower in forest lands and grasslands, which indicated that OCPs were very much influenced by human activities. The proportion of PCB components in this study area suggested that they mainly came from atmospheric deposition. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Organochlorine compounds (OCs) such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in soil and aquatic environment are obtaining increasing global concern (Zhou et al., 2001, 2006; Zhang et al., 2004; Feng et al., 2011) because of their persistence, toxicity and bioaccumulation (Tanabe et al., 1994; Jones and De Voogt, 1999). OCs can be transported from air to surface soil and water by dry and wet deposition, from soil to aquatic bodies by rainfall runoff, and from soil and aquatic bodies back to air by volatilization. Due to the ⇑ Corresponding author. Tel./fax: +86 10 58804585. E-mail address: [email protected] (Y. Li). http://dx.doi.org/10.1016/j.chemosphere.2014.03.095 0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
long-range atmospheric transport, OCs have been found in most areas of the world (Kong et al., 2005; Castro-Jiménez et al., 2008; Zhang et al., 2008; Zhao et al., 2010; Wang et al., 2012; Barakat et al., 2013; Gao et al., 2013b). They greatly affect the qualities of water, soil, air and even human health. Included in the group of OCPs are dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), dieldrin, endrin, aldrin, isodrin, heptachlor, heptachlor epoxide A, heptachlor epoxide B, hexachlorobenzene (HCB), oxychlordane, trans-chlordane, a-endosulfan, b-endosulfan, cis-chlordane and methoxychlor. DDTs and HCHs were dominant OCPs produced and utilized in China from 1950 to 1983 owing to their high efficiency, low cost, broad-spectrum pesticidal efficacy. Due to their persistence, bioaccumulation and toxicity, the ban on the production of technical
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HCHs and DDTs was effective on April 1st, 1983. Until then, about 4.9 million tons of HCHs and 0.4 million tons of DDTs had been used for agriculture in China (Hua and Shan, 1996). From 1991, China started the industrial production of lindane (c-HCH) for export and restricted usage on certain crops (Li et al., 2001). Lindane has been mainly used to kill locus, wheat mole cricket, midges, and wood moth. Although the use and production of DDTs and HCHs have been banned since 1983 in China, high residual levels can still be frequently detected in various environmental media (Yang et al., 2008a; Yang et al., 2008b; Xie et al., 2012). After 1983, approximately 11 400 tons of lindane was still reportedly being produced (Li et al., 2001), and DDTs have been continuously produced for approximately 20 years owing to export demands, malaria control and dicofol production (Yang et al., 2008a). Until now lindane is still produced and used in China. In theory, PCBs could have 209 possible congeners according to the number and position of their chlorine atoms. Among these 209 possible congeners, 12 kinds of dioxin-like PCBs are typical hormonal substances, which are able to induce adverse effects on human skin, liver, gastrointestinal systems, immune systems and others. Approximately 10 000 tons of PCBs were produced from 1965 to 1974 in China, which accounts for 1% of global production(Zheng et al., 2010) and the low chlorinated congeners PCBs are the dominant components (Xing et al., 2005). As for China, the production of PCBs was totally stopped in 1974, whereas PCBs still exist in many industrial process and byproducts. PCBs have been found in paints, dyed paper and plastics, heat exchange fluids in transformers and capacitors, and sealants. PCBs are also used as additives in pesticides. As the major OC sink, agricultural soil (Tao et al., 2005; Sun et al., 2009) was the primary target of many OC studies. Information regarding OC pollution in soil along rivers and reservoirs is especially important due to the high probability of flushing into the surrounding water bodies in rainy days (Kim et al., 2005; Herngren et al., 2006; Kang et al., 2010). Miyun Reservoir is the major surface drinking water resource for Beijing and its water quality is crucial to people’s health. Chao River is the main inflow of the Miyun Reservoir. The region along the lower reach of Chao River is predominantly agricultural lands with many country people living there. Non-point sources are the major pollution sources for Miyun Reservoir, which have exceeded the amount from point sources (Ou and Wang, 2008; Li et al., 2013). The OCs in soil can be
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migrated by volatilization, degradation, and leaching process to deeper soil layers or even groundwater, and flushing into surrounding water bodies. In this study, water and soil samples along the lower reach of Chao River were collected. The concentrations of OCPs and PCBs were determined to understand the potential OC pollution risk to Miyun Reservoir. 2. Materials and methods 2.1. Study area and sampling method A total of 15 samples were collected in October 2011, with 1 water sample from Chao River near Xiaocaocun (Fig. 1), about 12 km away from the entrance into Miyun Reservior. The other 14 soil samples were taken from lands along the lower reach of Chao River. The sampling lands include corn field (n = 5), orchard (n = 3), forest land (n = 3) and grassland (n = 3). The sampling site locations are shown in Fig. 1. Surface soil samples were collected using a metal shovel. The sampling depth was about 15 cm with relative loose soil that tends to be moved by the rainfall wash-off. Three subsamples were collected at each site within a 1 m2 area and bulked together to form one composite soil sample. Then the bulked sample was sealed in a clean polyethylene plastic bag and transported to the laboratory. All of the soil samples were air-dried for 3 weeks before analysis. At site 15 as shown in Fig. 1, 8 L water sample was collected and stored in 2 glass bottles, then transported back to the laboratory immediately. 2.2. Reagents The standard mixture solution for 24 OCPs, including a-, b-, cand d-HCH, O,P0 -DDE, O,P0 -DDD, P,P0 -DDE, P,P0 -DDT, O,P0 -DDT, P,P0 -DDD, dieldrin, endrin, aldrin, isodrin, heptachlor, heptachlor epoxide A, heptachlor epoxide B, HCB, oxychlordane isomer, trans-chlordane, cis-chlordane, a-endosulfan, b-endosulfan and methoxychlor was obtained from AccuStandard Company, USA. The standard mixture solution for 13 12C12-PCBs, including PCB-77, 105, 114, 118, 123, 126, 138, 153, 156, 167, 169, 180 and 189, was obtained from Labor Dr. Ehrenstorfer. The internal OCP
Fig. 1. Locations of sampling sites along the lower reach of Chao River.
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standards (13C6hexachlorobenzene, 13C6b-HCH, 13C6c-HCH, 13C10 trans-nonachlor, 13C12p, p0 -DDE, 13C10mirex and 13C12dieldrin) and PCBs (13C12PCB-77, 81, 105, 114, 118, 123, 126, 157, 159, 167, 169, 170, 180 and 189) were all purchased from Cambridge Isotope Laboratories. All of the solvents (hexane, acetone and dichloromethane) used for sample processing and analysis were of chromatography grade.
2.3.2. Water sample Water sample was filtered and then adsorbed by Amberlite XAD-2. The Amberlite XAD-2 with the internal standard was Soxhlet extracted. The extraction and purification methods were the same as the methods for soil samples indicated above.
2.3. Sample extraction and clean-up
The concentrated OCP and PCB extracts were identified and quantified using GC–MS (gas chromatography–mass spectrometry) with a DB-5MS chromatographic column (30 m 0.25 mm, i.d. 0.1 lm, Agilent Technologies, Palo Alto, CA, USA). For OCPs, an oven program started at 80 °C for 3 min, and then increased to 260 °C at a rate of 6 °C min1. For PCBs, the oven temperature was set at 100 °C and maintained for 3 min, and then increased to 250 °C at a rate of 5 °C min1.
2.3.1. Soil samples A 10.00 g sub-sample was homogenized with 100 lL of internal standard (20 ng g1) and then Soxhlet extracted with a 1:1 (V:V) hexane and acetone solvent mixture (200 mL) for 24 h for OCP extraction. The extract was concentrated by a rotary evaporator to approximately 1 mL. An aluminum/silica gel column (1.2 cm 40 cm) was used to clean up and fractionate the extract. The column was flushed with 30 mL of hexane and then eluted with approximately 100 mL of hexane/dichloromethane (70:30, V:V). The fraction was re-concentrated by a rotary evaporator and further concentrated to 100 lL under a gentle stream of highly pure nitrogen gas. The PCB extraction was similar to the OCP extraction method. A 10.00 g sub-sample was mixed with 40 lL of the internal standard (16 ng g1) and Soxhlet extracted with a 1:1 (V:V) hexane and acetone solvent mixture (200 mL) for 24 h for PCB extraction. The extract was concentrated by a rotary evaporator to approximately 1 mL. The extract was purified using a multilayer silica gel column (1.5 cm 40 cm) and fractionated. The column was flushed with 50 mL of hexane and eluted with approximately 100 mL of hexane/dichloromethane (97:3, V:V). The solvent was then reduced to 100 lL.
2.4. Gas chromatography–mass spectrometry analysis
3. Results and discussion 3.1. Occurrence of OCPs P The concentration of OCPs, which stands for the sum of 24 kinds of OCPs examined in this study, in the water sample was 5.33 ng L1. The concentrations of the main contents including DDTs, HCHs and HCB were 2.19, 1.57 and 1.32 ng L1 comprising P 41%, 30% and 25% of the OCPs, respectively. The occurrences of DDTs, HCHs and HCB demonstrate the influence of pesticide usage in the upstream watershed of Chao River. The b-HCH concentration of 0.805 ng L1 in the water sample was higher than the a, c and d-HCH concentrations of 0.12, 0.5, 0.149 ng L1, respectively as demonstrated in Fig. 2. Higher b-HCH concentration is commonly found in water bodies since the a, c-HCH are easily degraded
Fig. 2. Concentrations of individual OCP in soil and water samples along the lower reach of Chao River.
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and d-HCH is the most easily adsorbed. In the water sample, O,P0 -DDD, dieldrin, endrin, aldrin, isodrin, heptachlor, heptachlor epoxide (isomer A), heptachlor epoxide (isomer B), oxychlordane isomer and a-endosulfan were all lower than detection limits. The other 14 OCPs were detected with very low concentrations of cis-chlordane and b-endosulfan as shown in Fig. 2. More OCP categories were detected in soil samples except for dHCH, dieldrin, endrin, aldrin, isodrin, heptachlor epoxide (isomer A), oxychlordane isomer and methoxychlor. The mean, minimum P and maximum concentrations of OCPs in soil samples were 1 4.84, 0.81 and 16.85 ng g . There were two or three orders of magnitude in difference among the sites for c-HCH, P,P0 -DDE as shown in Fig. 2. The great OCP content difference among sites demonstrated that anthropogenic activities brought different amount of OCPs to different kinds of land uses and different sites in the same watershed. It is important to know these differences and make different management strategies for different land uses. The highest P OCPs level was found in corn field from site 10, which might be caused by heavy dose of pesticide in corn fields. Among the soil OCPs, DDTs, HCHs and HCB were the most dominant compounds, accounting for 61%, 27% and 11%, which were similar to the water sample. In the agriculture soil, DDTs, HCHs and HCB mainly come from the old and new use of pesticides, which can be flushed into rivers when it rains. O,P0 -DDE, O,P0 -DDD, P,P0 -DDE, P,P0 -DDT and O,P0 -DDT + P,P0 -DDD P were all detected in the soil and water samples. The DDTs (the 0 0 0 0 sum of P,P -DDE, P,P -DDT and O,P -DDT + P,P -DDD) concentration in soil samples ranged from 0.1835 to 15.7150 ng g1 as shown in Fig. 2, which was lower than the national soil safety standards for P level one (50 ng g1, GB, 1995). The DDTs concentration fluctuated among different sites, with the highest concentration found in S10 corn field and the lowest concentration found in S3 forest land. This further demonstrated that DDTs in this region mainly came from human activities. In terms of the measured individual DDT, the detection frequencies for 14 soil samples were higher than
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83% (Fig. 2), indicating wide occurrence and persistence of DDTs in this region. P As shown in Fig. 2, the HCH (the sum of a-, b-, c- and d-HCH) concentration ranged from 0.1162 to 6.0188 ng g1 with a mean of 1.3063 ng g1. In the soil samples, c-HCH was the dominant HCH, with a mean value of 1.1416 ng g1, followed by b-HCH and a-HCH. This HCH distribution is different from water sample with the dominance of b-HCH and certain amount of c-HCH. The degradation rate of c-HCH is influenced by the characteristics of soil and the average half-life period is two months. Therefore the HCHs in water sample should come from the previous rainfall runoff and river sediment release, both of which contained older application of HCHs. Whereas the HCHs in soil samples come from both recent and precious HCH applications. In Fig. 2, the detection frequencies of a-, b- and c-HCH were all 100%, and the d-HCH concentrations of all samples were lower than the detection limit. The highest a-, band c-HCH concentrations occurred in S9 and S12, both of which were corn field. This indicates the critical effect of land use type P on HCH concentrations in soil. Whereas all the HCHs concentrations were lower than the national soil safety standards for level one (50 ng g1, GB, 1995). The concentration of HCB in the water sample was 1.323 ng L1. The HCB concentrations in soil samples were within a range of 0.2221–1.2716 ng g1, with a mean of 0.5561 ng g1. The highest soil sample HCB concentration occurred in S2 (grassland) with a value of 1.2716 ng g1, which might be due to the drowning in rainy season at S2. 3.2. Occurrence of PCBs In the water sample, only two kinds of PCBs, namely PCB-105 and PCB-118, were detected. In soil samples, 12 kinds of dioxinlike PCBs were investigated, among which 9 kinds were detected and PCB-81, 114 and 157 were lower than the detection limits as P shown in Fig. 3. The concentration of PCBs, which stands for
Fig. 3. Concentrations of individual PCB in soil and water samples along the lower reach of Chao River.
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the sum of 12 kinds of PCBs examined in this study, ranged from 0.0039 to 0.0365 ng g1, with an average of 0.0150 ng g1. The PCB-118 concentration ranged from 0.0010 to 0.0272 ng g1 with a mean of 0.0068 ng g1. PCB-118 was the dominant PCB with the highest concentration in all the dioxin-like PCBs. It was the only component detected 100%, followed by PCB-105. PCBs in the surface soils and waters mainly come from dry and wet deposition, surface runoff, and industrial wastes (Hiller et al., 2011). Although some PCBs are used as additives to produce pesticides such as HCHs and trichlorophenol (Que, 2007), the amount of PCBs added is very small compared with other sources. Therefore direct application of PCBs on crops can be ignored. In China, 90% of PCBs was primarily used in power capacitors and 10% was mainly used as a paint additive (Zhang et al., 2008). PCB-105 and PCB-118 were the major components of PCBs in both soil and water samples in this study, which indicated that PCBs in soil and water might come from similar sources. In this study area, no PCB storage or production industries have ever existed. Therefore PCBs in this region may mainly come from atmospheric deposition. 3.3. Distribution of OCPs and PCBs with different land uses P P The mean concentrations of OCPs and PCBs for individual land use were plotted in Fig. 4. Higher mean concentrations of P OCPs were found in corn fields and orchards and lower mean P concentrations of OCPs in forests and grasslands, indicating that stronger human activities in corn fields and orchards caused higher P OCPs concentrations. More inputs of pesticides and fertilizers in corn fields and orchards raised the level of OCPs.
Fig. 4. Mean concentrations of
P P OCPs and PCBs for different land uses.
P The mean PCBs distribution with land uses was different from P P that of OCPs. Mean concentration of PCBs in grasslands was the highest among these four land uses. This is because the grasslands are often submerged in water in rainy season so that the grassland samples contain both soil and sediments, which can absorb the PCBs in water. PCBs are easily adsorbed to soil organic matter and difficult to be flushed. Higher mean concentrations of P PCBs in orchards and forest lands may be due to the larger leaf surface area, which can receive more deposition of PCBs from the atmosphere. The particles with PCBs on leaves will be flushed to the ground in rainy days. 3.4. Possible sources of OCPs and PCBs Isomer ratios were analyzed to obtain further insights of the possible pollution sources. Technical HCHs contain 60–70% aHCH, 5–12% b-HCH, 10–12% c-HCH and 6–10% d-HCH, and the lindane is composed of pure c-HCH (>99%) (Iwata et al., 1993). Therefore the ratio of a-HCH/c-HCH is relatively stable with a value of 4.64–5.83 for technical HCHs and nearly zero for lindane (Zhang et al., 2004). Additionally, this ratio could increase with the environmental degradation process since a-HCH and c-HCH are easily degraded in the environment. Among the four kinds of HCHs, b-HCH is the most stable and hardest to degrade. In this study, the a-HCH/c-HCH ratios of 14 soil samples ranged from 0.002 to 0.796 with a mean of 0.138 as shown in Table 1. It can be concluded that HCH residuals in soil in this area primarily came from a newer use of lindane and old technical HCH residuals. The a-HCH/c-HCH ratio of the water sample is 0.240. The ratios between the parent compound and its metabolites can provide useful information on the pollution sources. Technical DDTs generally contain 75% P,P0 -DDT, 15% O,P0 -DDT, 5% P,P0 -DDE, and less O,P0 -DDE, P,P0 -DDD and O,P0 -DDD. The O,P0 -DDT/P,P0 -DDT ratio can be used to distinguish DDT pollution caused by technical DDTs from that of dicofol. The value of O,P0 -DDT/P,P0 -DDT ranges from 0.2 to 0.3 in technical DDTs and from 1.3 to 9.3 or higher in dicofol (Qiu et al., 2005). In this study, the concentration of O,P0 DDT + P,P0 -DDD was identified instead of individual O,P0 -DDT and P,P0 -DDD. So the ratio of (O,P0 -DDT + P,P0 -DDD)/P,P0 -DDT was calculated and this ratio was mostly lower than 0.3 with the exception of S3, S6 and S14 as shown in Table 1. This finding indicated that technical DDTs were the main source for most of the study area. More ratios among OCPs can also be used to indicate the sources of OCPs. When heptachlor epoxide/heptachlor is larger
Table 1 Ratios of different OCP concentrations for 15 sampling sites. Sites
a-HCH/cHCH
S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12 S13 S14 S15
0.030 0.112 0.017 0.002 0.012 0.034 0.195 0.164 0.110 0.247 0.796 0.009 0.204 0.007 0.240
(O,P0 -DDT + P,P0 -DDD)/P,P0 DDT n.n. 0.162 0.430 0.205 0.179 0.342 0.147 0.239 0.228 0.110 – 0.231 0.145 1.328 0.074
P,P0 -DDE/P,P0 DDT n.n. 0.054 0.306 0.059 0.603 0.061 0.139 0.103 0.805 0.956 0.033 0.091 0.017 0.379 0.101
Heptachlor epoxide/ heptachlor *
0 0* 0* 0* n.n. n.n. n.n. n.n. 1.136 – n.n. – 0* 0* n.n.
cis-Chlordane/transchlordane
a-Endosulfan/b-
0.606 0.115 n.n. n.n. 0* n.n. 0* n.n. 0* 0* n.n. 0* n.n. n.n. 0.084
1.352 8.966 n.n. 0.361 n.n. n.n. 4.458 n.n. n.n. n.n. n.n. n.n. n.n. 1.586 0*
n.n.: The denominator and numerator are all lower than the detection limits. 0*: The numerator is lower than the detection limit whereas the denominator is higher than the detection limit. –: The denominator is lower than the detection limit whereas the numerator is higher than the detection limit.
endosulfan
141
– 0.5–32.5 0.19 13–407 n.d.–19.73 – 0.2–25.6 – n.d.–40 n.d.–9.12 – 0.3–70.6 1.4 36–574 n.d.–5.1 0.08–187.8 0.8–44.2 2.3 – n.d.–1.8 6.2–11.95 2.7–12.3 – – n.d.–4.51 n.d.–0.9 0.4–129.6 0.06 – n.d.–0.74 Delhi, India (n = 9) Sugarcane crop soils, Mexico (n = 63) UK (n = 3) Garden soil of Waikato, New Zealand (n = 5) Indo–Gangetic, alluvial plains, India(n = 31)
– – Flooded soils of Florida, USA (n = 10)
–
– 0.38–4.76 – 1.93–34.65 – 0.9–8.79 Around Taihu Lake, China (n = 13) Wuchuan, China # (n = 56)
n.d.–1.37 n.d.–1.41 n.d.–2.67 n.d.–2.74 n.d.–1.10 n.d.–0.78 Around Guanting Reservoir, China # (n = 30) Around Guanting Reservoir, China # (n = 56)
0.3–1.07 0.27–1.32 0.09–3.61 0.1–2.31 0.32–0.96 0.24–1.01
– – –
Along Jinjiang River, China #(n = 8)
Around Hongze lake, China (upland field, n = 22) Along Mulan River, China# (n = 17) Along Qiulu River, China # (n = 8)
0.0225– 5.8610 0.09–1.57 0.0020– 0.0954 0.12–2.06 Along Chao River, China# (n = 14)
0.0223– 0.3484 n.d.-2.20
c-HCH b-HCH
a-HCH Area
To understand more regarding the OC level in this region, the HCH and DDT concentrations from this study are compared with similar studies on soil samples from other areas (Marburger et al., 2002; Zhang et al., 2002; Feng et al., 2003; Wang et al., 2005; Zhang et al., 2005; Singh et al., 2007; Zhang et al., 2011; Yang et al., 2013; Gao et al., 2013a) as shown in Table 2. The concentrations of a-HCH and b-HCH in this study are lower than those of other regions, primarily as a consequence of lower past use in this region. The highest concentration of c-HCH is nearly four times higher than in most other water resource regions in China. This indicates that the new use of lindane in the Chao River area should be given more attention. Whereas in other countries especially developing countries such as India, the highest concentration of c-HCH is 187.8 ng g1, which is much higher than other regions. P As for the HCHs in this study, its concentration is at a medium level compared with other water resource areas. When compared P with the Guanting Reservoir area, the concentration of HCHs is at a similar pollution level. Guanting Reservoir was not able to serve as the drinking water resource for Beijing from 1997 due to its deteriorated water quality and resumed to be mainly industrial water resource for Beijing after restoration. Therefore, pesticide control measures should be implemented in the Chao River region to reduce further pollution to Miyun Reservoir. DDT concentrations in the study region are moderate in comparison with other water resource area, and much lower than the non-water resource places such as garden soil. Complex anthropogenic pollution exists in this study area.
Table 2 HCH and DDT concentrations of surface soil samples from different regions worldwide (ng g1).
3.5. Comparative analysis
#: Soil samples were collected around water resource regions. n.d.: Lower than the detection limit. –: No data available.
– – 0.37 n.d.–111 n.d.– 42.39 6.4–199.8 – – – 0.08–7.25 n.d.–3.6 4.3–4.6 – – n.d.–2.71
0.7 –
– – – 70–1160 n.d.–74.06
Marburger et al. (2002) Prakash et al. (2004) Velasco et al. (2012) Meijer et al. (2001) Gaw et al. (2006) Singh et al. (2007) – 0.7
Feng et al. (2003) Zhang et al. (2002) n.d.–5.3 – – 0.88–6.88
– 0.55– 7.38 0.7 n.d.–3.4 –
– 1.13– 12.69 –
–
n.d.–44.82 n.d.–52.2 n.d.–3.93 n.d.–3.55
n.d.–8.96 n.d.–7.33
n.d.–5.84 n.d.– 39.09 – –
– 0.93–10.28
Zhang et al. (2005) Wang et al. (2005) n.d.–94.07 n.d.–57.9 n.d.–39.8 n.d.–33.08
Zhang et al. (2011) Zhang et al. (2011) 0.91–27.89 1.24–10.04 0.22–8.01 0.03–4.26
n.d.–3.4 0.01– 1.23 n.d.–7.54 n.d.–3.37 0.47–7.32 0.03–17.05 n.d.–5.09 0.14–5.44 1.22–7.47 0.96–4.11 0.42–3 0.35–1.31
Gao et al. (2013a) n.d.–73.55 – n.d.–20.43 –
n.d.–9.99 0.2–2.29
–
0.19– 3.96 –
–
Yang et al. (2013)
0.1835– 15.7150 1.77–25.03 0.1019– 7.6067 0.38–7.55 –
0.0145– 7.2697 0.27–10.04 –
0.1162– 6.0188 0.41–6.78
Reference d-HCH
P HCHs
O,P0 -DDT
P,P0 -DDE
than 1, heptachlor contamination most likely originates from older uses of heptachlor (Jiang et al., 2009). In S9, S10 and S12, the heptachlor mainly came from older uses related to the development of agriculture. If the ratio of cis-chlordane/trans-chlordane is larger than 1, the origin is an older use (Bidleman et al., 2002). In this study, S1, S2 and S15 showed a newer input from chlordane. In technical endosulfan, there are 70% a-endosulfan and 30% b-endosulfan, and a-endosulfan is more easily degraded. S2 and S7 had values that were clearly larger than 2.33, suggesting that they came from a newer endosulfan use. The mean PCB proportions of 14 soil samples are shown in Fig. 5. PCB-118 was the dominant component of PCBs, which was similar to other studies (Park et al., 2010; Chavhan et al., 2012). The PCBs produced in China were mainly composed of low chlorinated congeners (Zhang et al., 2008). There were no PCB production factories or storage in this region in history and the PCBs mainly originated from atmospheric deposition.
n.d.
P DDTs P,P0 -DDT P,P0 -DDD
Fig. 5. Mean individual PCB proportion of 14 soil samples.
This study
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4. Conclusions Along the lower reach of Chao River, DDTs, HCHs and HCB were the dominant OCPs in soil and water samples. The concentrations of OCPs varied greatly with different sites with up to two to three orders difference forc-HCH, P,P0 -DDE. Human activities greatly influence the OCP inputs to different sites. OCP concentrations were higher in orchards and corn fields and lower in forest lands and grasslands. The concentration of c-HCH was higher than in most other water resource areas. New input of c-HCH exists in this region indicating recent application of prohibited pesticides such as linane, which highlights the importance of pesticide control in this region. DDT ratio analysis indicated that the DDTs at most sites came from older uses of technical DDTs. The PCBs in this area primarily came from atmospheric deposition, and PCB-118 was the main component. Similar OC concentration distribution in soil and water samples suggested that the OCs in water mainly originated from soil flushing by rain. Acknowledgements This research is supported by the National Science Foundation for Innovative Research Group (Grant 51121003), the National Science Foundation of China (Grant 51278054) and the FST Short Term PD & VF Scheme 2013 and MYRG072(Y1-L2)-FST13-LIC from University of Macao. The authors are grateful for these supports. References Barakat, A.O., Khairy, M., Aukaily, I., 2013. Persistent organochlorine pesticide and PCB residues in surface sediments of Lake Qarun, a protected area of Egypt. Chemosphere 90, 2467–2476. Bidleman, T.F., Jantunen, L.M.M., Helm, P.A., Brorström-Lundén, E., Juntto, S., 2002. Chlordane enantiomers and temporal trends of chlordane isomers in arctic air. Environ. Sci. Technol. 36, 539–544. Castro-Jiménez, J., Deviller, G., Ghiani, M., Loos, R., Mariani, G., Skejo, H., Umlauf, G., Wollgast, J., Laugier, T., Héas-Moisan, K., Léauté, F., Munschy, C., Tixier, C., Tronczyn´ski, J., 2008. PCDD/F and PCB multi-media ambient concentrations, congener patterns and occurrence in a Mediterranean coastal lagoon (Etang de Thau, France). Environ. Pollut. 156, 123–135. Chavhan, C., Sheikh, J., Algiwale, T., Thokchom, B., Thacker, N., 2012. Releases of dioxin-like PCBs in water, soil and residue produced from high thermal processes and waste incinerators. Bull. Environ. Contam. Toxicol. 89, 537–541. Feng, J., Zhai, M., Liu, Q., Sun, J., Guo, J., 2011. Residues of organochlorine pesticides (OCPs) in upper reach of the Huaihe River, East China. Ecotoxicol. Environ. Saf. 74, 2252–2259. Feng, K., Yu, B.Y., Ge, D.M., Wong, M.H., Wang, X.C., Cao, Z.H., 2003. Organo-chlorine pesticide (DDT and HCH) residues in the Taihu Lake Region and its movement in soil–water system: I. Field survey of DDT and HCH residues in ecosystem of the region. Chemosphere 50, 683–687. Gao, J., Zhou, H., Pan, G., Wang, J., Chen, B., 2013a. Factors influencing the persistence of organochlorine pesticides in surface soil from the region around the Hongze Lake, China. Sci. Total Environ. 443, 7–13. Gao, S., Chen, J., Shen, Z., Liu, H., Chen, Y., 2013b. Seasonal and spatial distributions and possible sources of polychlorinated biphenyls in surface sediments of Yangtze Estuary, China. Chemosphere 91, 809–816. Gaw, S.K., P Wilkins, A.L., Kim, N.D., Palmer, G.T., Robinson, P., 2006. Trace element and DDT concentrations in horticultural soils from the Tasman, Waikato and Auckland regions of New Zealand. Sci. Total Environ. 355, 31–47. GB, 1995. Soil environmental quality standard (GB15618-1995). (in Chinese). Herngren, L., Goonetilleke, A., Ayoko, G.A., 2006. Analysis of heavy metals in roaddeposited sediments. Anal. Chim. Acta 571, 270–278. Hiller, E., Zemanová, L., Sirotiak, M., Jurkovicˇ, L.U., 2011. Concentrations, distributions, and sources of polychlorinated biphenyls and polycyclic aromatic hydrocarbons in bed sediments of the water reservoirs in Slovakia. Environ. Monit. Assess. 173, 883–897. Hua, X., Shan, Z., 1996. The production and application of pesticides and factor analysis of their pollution in environment in China. Adv. Environ. Sci. 4, 33–45 (in Chinese). Iwata, H., Tanabe, S., Sakai, N., Tatsukawa, R., 1993. Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of ocean on their global transport and fate. Environ. Sci. Technol. 27, 1080–1098. Jiang, Y., Wang, X., Jia, Y., Wang, F., Wu, M., Sheng, G., Fu, J., 2009. Occurrence, distribution and possible sources of organochlorine pesticides in agricultural soil of Shanghai, China. J. Hazard. Mater. 170, 989–997. Jones, K.C., De Voogt, P., 1999. Persistent organic pollutants (POPs): state of the science. Environ. Pollut. 100, 209–221.
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