Journal of Geochemical Exploration

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1 Journal of Geochemical Exploration 125 (2013) Contents lists available at SciVerse ScienceDirect Journal of Geochemical Exploration journal homepage: Organochlorine pesticides (OCPs) in soils of the coastal areas along Sanduao Bay and Xinghua Bay, southeast China Jiaquan Zhang a,b, Xinli Xing a, Shihua Qi a,, Lingzhi Tan a, Dan Yang a, Wei Chen a, Junhua Yang c, Meihui Xu c a State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan China b Hubei Key Laboratory of Mine Environmental Pollution Control and Remediation, School of Environmental Science and Engineering, Hubei Polytechnic University, Huangshi China c Fujian Institute of Geological Survey, Fuzhou China article info abstract Article history: Received 18 August 2012 Accepted 17 December 2012 Available online 23 December 2012 Keywords: Organochlorine pesticides (OCPs) Soil Fujian province Sanduao Bay Xinghua Bay Concentrations of organochlorine pesticides (OCPs) have been measured in 21 surface soil samples (0 20 cm) collected along Sanduao Bay and Xinghua Bay, southeast China. The total concentrations of OCPs in soil samples of Sanduao Bay and Xinghua Bay range from 1.85 to ng/g (dry weight) and ng/g (dry weight), respectively. The mean concentrations of soil samples two bays were in following order: DDTs>HCHs> endosulfans>chlordanes. HCHs in the study areas may have received fresh lindane input. DDTs in 85.7% soil along Sanduao Bay and Xinghua Bay indicating a use of technical DDT in these areas for a long time. But, DDTs in some soil samples along Xinghua Bay were likely due to the historical application of technical DDT. There were weak correlations between TOC contents and residues of HCHs, DDTs, chlordane and endosulfan, indicating that TOC of soil is not the only factor enhance adsorption of these compounds Published by Elsevier B.V. 1. Introduction As one class of the ubiquitous persistent organic pollutants (POPs), organochlorine pesticides (OCPs) have been a major environmental issue, drawing extensive attention from environmental scientists and the public. They were the most widely used pesticides around the world before the 1970s (Wong et al., 2005). Being a large agricultural country, China has been a major producer and consumer of OCPs. In China, OCPs were used to control pests mostly for more than three decades. Even after the ban of technical hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in 1983, ton of lindane (which contains mainly γ-hch) was still produced between 1991 and 2000, and DDT production also continues due to the export demand (Tao et al., 2005). Endosulfan is still on the list of allowable insecticides on crops presently in China (Zhang et al., 2012). As we know, soils still play an important role in global distribution and fate of POPs. They not only have a large retention capacity but can also re-emit POPs into the environment as secondary sources (Barra et al., 2005; Zheng et al., 2009). A significant proportion of HCHs and DDTs, typically ranging from 20 to 70% of a pesticide or its degradation products, may remain in soil following application (Miglioranza et al., 2003). This source can keep for decades because of large storage and high persistence. A few examples include accumulation by terrestrial animals, wash-off to aquatic environments, and exchange with air. Corresponding author. Tel.: address: shihuaqi@cug.edu.cnl (S. Qi). Meanwhile, sediment was usually regarded as an important sink of OCPs. The sediment could also be a potential source via a series of biogeochemical processes. Concentrations of OCPs in sediment may be affected by a variety of inputs from terrestrial soil, such as agricultural surface runoff, groundwater, and atmospheric deposition. We can say that soils along the bay are the connection between bay and continent. So, the study on OCPs in the soils along the bay is very important. Sanduao Bay is not far from Ningde City, northeast Fujian province. Sanduao Bay is a very special bay, with a water area of 714 km 2, but the only outlet of the east is only 2.6 km wide, is rare in the world. The channel depth of Sanduao Bay is one of the best bays in the world, and the shelter, with good nondeposit. It is a world-class natural deep water harbor. Xinghua Bay is one of the biggest natural deep water bays in Fujian province, with a water area of 370 km 2, and in a slightly rectangular shape. Moreover, the agricultural land stretches between the cities have been cultured for many decades and had received large amounts of OCPs in the past. Some POPs have been detected in water, sediment and marine fauna in Xinghua Bay (Wang et al., 2009; Yatawara et al., 2010), but so far Sanduao Bay has not been reported about POPs in soils. In this study, soil samples collected along Sanduao Bay and Xinghua Bay were analyzed for OCPs to demonstrate the distribution of OCPs in these two bays, because OCPs in soil can be released into adjacent the bays, and OCPs were determined to compare the contamination status and distribution between Sanduao Bay and Xinghua Bay /$ see front matter 2012 Published by Elsevier B.V.

2 154 J. Zhang et al. / Journal of Geochemical Exploration 125 (2013) Materials and methods 2.1. Study area and sample collection Twenty-one surface soil samples (0 20 cm) of the coastal areas were collected along Sanduao Bay and Xinghua Bay, southeast China. The locations of the sampling stations are shown in Fig. 1, of which 11 sites were located at Sanduao Bay and 10 sites at Xinghua Bay. The surface soils were collected in March 2009 using a precleaned stainless steel scoop. At each site, four sub samples were collected from a 50 m 50 m plot, and thoroughly mixed to form a composite sample. All the samples were packed into polyethylene plastic bags and immediately stored at 4 C until storing in lab's freezer ( 20 C) Sample extraction and cleanup The analytical method for OCPs was carried out according to the method, US-EPA 8080A. In the laboratory, soil samples were homogenized and air-dried. Ten grams of dried soil was spiked with 20 ng of 2,4,5,6- tetrachoro-m-xylene (TCmX) and decachlorobiphenyl (PCB209) as recovery surrogates and were Soxhlet-extracted with dichloromethane (Tedia Co., USA) for 24 h. Elemental sulfur was removed by adding activated copper granules to the collection flasks. The sample extract was concentrated and solvent-exchanged to n-hexane (Tedia Co., USA) and further reduced to 2 3 ml by a rotary evaporator. The alumina/silica (1:2, v/v) gel column (both 3% deactivated with H 2 O) was used to clean up the extract and OCPs were eluted with 30 ml of dichloromethane/hexane (2/3, v/v). The eluate was then concentrated to 0.2 ml under a gentle nitrogen stream. Pentachloronitrobenzene (PCNB) was added as an internal standard prior to gas chromatography-electron (GC-ECD) analysis. The mixed standard sample of OCPs, 2,4,5,6-tetrachloro-m-xylene (TCmX), decachlorobiphenyl (PCB 209) and pentachloronitrobenzene (PCNB) were purchased from Ultra Scientific, USA. Silica gel ( μm) was activated at 130 C for 16 h, then deactivated by purified water (3.0%, w/w) and stored in a desiccator. Anhydrous sodium sulfate was baked at 600 C for 6 h before use. The glass ware were cleaned with detergent, K 2 Cr 2 O 7 H 2 SO 4 solution, tap water and deionized water, respectively and finally baked at 180 C for 3.5 h before use Analysis of OCPs An Agilent 7890A gas chromatograph equipped with a Ni electron capture detector (GC-ECD) was used for detecting the levels of OCPs in the extracted surface soil samples. The capillary column used for the analysis was a DB-5 (30 m, 0.32 mm i.d., 0.25 μm film thickness). Nitrogen was used as carrier gas at 2.5 ml/min under the constant flow mode. Injector and detector temperatures were maintained at 290 C and 300 C, respectively. The temperature program used as follows: the oven temperature began at 100 C (equilibrium time 1 min), raised to 200 C at 4 C/min, then to 230 C at 2 C/min, and at last reached to 280 C at a rate of 8 C/min, held for 15 min. N km Sanduao Bay S4 S5 S6 S7 S8 S N S10 S3 Jiangxi Zhejiang Shanghai S E Xinghua Bay S1 S N E N Fujian X6 Hongkong X4 X5 X7 X8 X9 X10 Sampling site X3 10ng/g X2 X N E E Fig. 1. Locations of the sampling stations and concentrations of OCPs in Sanduao Bay and Xinghua Bay.

3 J. Zhang et al. / Journal of Geochemical Exploration 125 (2013) Analysis of total organic carbon (TOC) About 3 g of the pulverized soil sample was treated with 1 M HCl for 24 h. After the inorganic carbon was thoroughly removed, it was dried at 85 C until the weight ceased to change. 50 mg of the sample was used to determine TOC. It was measured with a liquitoc (Elementar, Germany) by conventional standard procedures Quality control The target compounds were identified on the basis of the retention times (previously confirmed with GC MS) and quantified by the internal standard. The residues of HCHs and DDTs were quantitatively determined by the calibration curves of the standards using peak areas. The quantitative determinations were performed be internal standard procedure. The quality assurance of analytical method could be found in our previous work (Zhang et al., 2011). No significant peaks overlapping the OCP standards appeared in the chromatograms of the blanks. The method detection limits (MDLs) of OCPs were described as 3:1 signal versus noise value (S/N). The spiked recoveries of OCPs using 20 ng of composite standards were in the range of %. The concentrations of OCPs were corrected according to the recovery ratios for the surrogates. The relative standard deviation (RSD) ranged from 4% to 10%. 3. Results and discussion 3.1. Residues of OCPs in soil from Sanduao Bay Fig. 1 shows the horizontal distribution of OCPs in surface soils of Sanduao Bay. The arithmetic mean (with standard deviations (±SD)) and range of OCPs in surface soil of Sanduao Bay were shown in Table 1. The total concentrations of OCPs in soil samples of Sanduao Bay were in the range of ng/g. The mean concentration was in order: DDTs>HCHs>endosulfans>chlordanes. DDTs were the dominant contamination in surface soil of Sanduao Bay. The distribution of OCPs in surface soil of Sanduao Bay was shown in Table 1. The results revealed that OCPs concentrations varied widely depending on their location, specifically for Sanduao Bay, the highest level was found at site S5, followed by sites S4, however, site S10 was the lowest level. The high level at site S5 and S4 are likely explained by the fact that S5 and S4 is near the city of Ningde, where many factories discharge various organic pollutants. Sites S10 was located in the outside of Sanduao Bay, where it is harder for the discharged pollutants to reach. The concentrations of total HCHs (sum of α-hch, β-hch, γ-hch and δ-hch) in soil of Sanduao Bay ranged from 1.32 to 3.18 ng/g, with a mean (±SD) value of 2.15±0.70 ng/g (Table 1). As far as HCH isomers are concerned, the concentration was in an order: δ-hch>α-hch>γ-hch>β-hch. The most dominant δ-hch ranged from 0.38 to 1.35 ng/g, with a mean (±SD) value of 0.72±0.34 ng/g (Table 1). The concentrations of total DDTs (sum of p,p -DDT, p,p -DDE, p,p -DDD and ο,p -DDT) ranged from 0.08 to ng/g, with a mean (±SD) value of 13.25±17.78 ng/g (Table 1). In terms of the distribution of DDT and its various metabolites in the soil samples, o,p -DDT and p,p -DDT were the most dominant, and its mean (± SD) concentrations were 10.08±18.70 and 2.13±2.50 ng/g, respectively. The residue of o,p -DDT and p,p -DDT ranged from n.d ng/g and ng/g, respectively (Table 1). In this study, the mean values (±SD) of endosulfan concentrations (sum of α- and β-endosulfan) in soil samples were 0.83± 0.44 ng/g. α- and β-isomers were detected in soil samples with the levels from n.d. to and n.d. to 0.91 ng/g, respectively. The mean concentration of β-isomer was higher than that of α-isomer, which can be explained by a more rapid degradation of α-isomer in soil (Jiang et al., 2009). The mean value (±SD) of chlordane concentrations (sum of trans-chlordane and cis-chlordane) in soil samples was 0.72±0.32 ng/g. The concentrations of cis-chlordane and trans-chlordane were in the range of n.d ng/g and ng/g, respectively Residues of OCPs in soil from Xinghua Bay Fig. 1 shows the horizontal distribution of OCPs in surface soils from Xinghua Bay. The arithmetic mean (±SD) and range of OCPs in surface soil of Xinghua Bay are shown in Table 1. The total concentrations of OCPs in soil samples of Xinghua Bay were in the range of ng/g. The mean concentration was in order: DDTs> HCHs>endosulfans>chlordanes. DDTs were the dominant contamination in the surface soil of Xinghua Bay. The distribution of OCPs in the surface soil of Xinghua Bay is shown in Table 1. The results revealed that OCPs concentrations of Fuzhou City were higher than Putian City. The high level is likely explained by many OCPs factories discharge and heavy pesticide usage. The concentrations of total HCHs in soil of Xinghua Bay ranged from 2.02 to 4.03 ng/g, with a mean (±SD) value of 2.88±0.77 ng/g Table 1 Concentrations of OCPs in soil from Sanduao Bay and Xinghua Bay, and soil reference values (ng/g dw). Compound Sanduao Bay Xinghua Bay Reference values Mean ±SD Range Mean ±SD Range China b Neth c α-hch β-hch n.d. a γ-hch δ-hch HCHs o,p -DDT n.d p,p -DDE n.d p,p -DDD n.d p,p -DDT DDTs cis-chlordane n.d trans-chlordane Chlordanes α-endosulfan n.d n.d β-endosulfan n.d Endosulfans OCPs a Not detected. b Chinese Environmental Quality Standard for Soils (GB ). c Netherlands Target Values for Soil Remediation (2000).

4 156 J. Zhang et al. / Journal of Geochemical Exploration 125 (2013) (Table 1). As far as HCH isomers are concerned, the concentration was in the order: β-hch>δ-hch>γ-hch>α-hch. The most dominant β-hch ranged from 0.33 to 2.31, with a mean (±SD) value of 1.04± 0.62 ng/g (Table 1). The concentrations of total DDTs ranged from 1.24 to ng/g, with a mean (±SD) value of 15.41±11.19 ng/g (Table 1). In terms of the distribution of DDT and its various metabolites in the soil samples, p,p -DDT was the most dominant, and its mean (± SD) concentration was 8.57±9.85 ng/g. The residue of p,p -DDT ranged from 0.35 to ng/g (Table 1). In this study, the mean value (±SD) of endosulfan concentrations in soil samples was 0.87±0.27 ng/g. α- and β-isomer were detected in soil samples with the levels from n.d. to 0.74 and 0.43 to 0.75 ng/g, respectively. The mean concentration of β-isomer was higher than that of α-isomer, which can be explained by the more rapid degradation of α-isomer in soil (Jiang et al., 2009). The mean values (±SD) of chlordane concentrations in soil samples were 0.65±0.21 ng/g. The concentrations of cis-chlordane and transchlordane were in the range of ng/g and ng/g, respectively Compositions and sources of OCPs Technical HCHs and lindane were the main sources of HCH pollution in China. Technical HCHs (α-hch (60% 70%), β-hch (5% 12%), γ-hch (10% 12%) and δ-hch (6% 10%)) was banned in China in the mid-1980s. Afterwards, it was substituted by lindane (>99% γ-hch) (Willett et al., 1998). Based on the composition of HCHs, α/ γ-ratio is used to identify fresh inputs of HCHs. In technical HCHs, this ratio is between 3 and 7 (Li, 1999; Li et al., 1998). Therefore, a high ratio of α/γ-hch reflects historical evidence of HCHs and a low ratio of α/γ-hch reflects the current use of lindane (Tao et al., 2005). By comparing the ratio of this study with data from literature, the major sources of HCHs in samples from the study area may be identified. As shown in Fig. 2, the ratios of α/γ-hch in all soils were less than 3. And thus it could be inferred that HCHs in these study area may be have been received fresh lindane. Meanwhile, compared to other OCPs, HCHs isomers are generally more water soluble and volatile, which explains why HCHs in soils were much lower than DDTs. Technical DDT and dicofol were the main sources of DDT pollution in China (Yang et al., 2010). The ratios of DDT and its metabolites provide the information about the pollution source. In general, the ratio of (DDE+DDD)/(p,p -DDT+DDE+DDD) is a useful indicator for new inputs of the technical DDTs (Qiu et al., 2004). The low ratio of (DDE+DDD)/(p,p -DDT+DDE+DDD) (b0.5) is indicative for fresh DDTs application and a ratio much greater than 0.5 indicates aged (microbial degraded) DDTs (Jaga and Dharmani, 2003). In addition, the ratio of o,p -DDT/p,p -DDT ranges from 0.2 to 0.3 in technical DDT and from 1.3 to 9.3 or higher than 9.3 in dicofol (Jiang et al., 2009; Li et al., 2008; Qiu et al., 2005). As shown in Fig. 3, the ratios of (DDE+DDD)/(p,p -DDT+DDE+DDD) in 85.7% soil along Sanduao Bay and Xinghua Bay were less than 0.5, suggesting that the application of technical DDT in these areas for a long time. The ratios of (DDE+DDD)/(p,p -DDT+DDE+DDD) of the soils in X4, X5, and X6 from Xinghua Bay were higher than 0.5, indicating the historical application of technical DDT. In addition, because p,p -DDT is reductively de-chlorinated to DDD under anaerobic conditions and to DDE under aerobic conditions(heberer and Dünnbier, 1999), this result was consistent with the fact that surface soil tends to be aerobic probably resulted in the low percentage of DDD and the high percentage of DDE among the metabolites of DDT in the study areas. The ratio of o,p -DDT/p,p -DDT in 63.4% soils was more than 1.3 from Sanduao Bay, while Xinghua Bay was 80%. The ratios of o,p -DDT/p,p -DDT in sediment cores were below 1.3. It indicates the application of the dicofol in these areas, recently Relationship between OCPs and TOC OCPs are inclined to bind with soil organic matter because of their hydrophobicity. The increase of organic matter content in soil can supply more carbon source to facilitate microbial degradation of OCPs (Jiang et al., 2009). As a result, the content of TOC (0.54% 4.54%) for the 21 soil samples from Xinghua Bay and Sanduao Bay might make an impact on the residue of OCPs in soil. In this study, the correlation coefficient square (R 2 ) of Sanduao Bay was HCHs (0.1050), DDTs (0.3509), chlordanes (0.1703), endosulfans (08), respectively. And the correlation coefficient square (R 2 ) of Xinghua Bay was HCHs (0.0161), DDTs (0.3171), chlordanes (01), endosulfans (0.4278), respectively (Fig. 4). There were all weak correlations between TOC contents and residues of HCHs, DDTs, chlordane and endosulfan. It is indicated that TOC could enhance adsorption of these compounds (Wang et al., 2006). However, there was a poor correlation between TOC and individual OCPs, which can be explained that land use, particle size of soil, ph value of soil (Gong et al., 2004a). Organic matter composition and physicochemical characteristics of OCPs can also affect the retention of individual OCPs in soil. Therefore, OCPs concentrations and TOC did not show a positive correlation Pollution assessment To assess the risk of contamination, concentrations of HCHs and DDTs in soils were compared with the soil quality reference values recommended in China and Netherlands. According to the Guideline of Chinese Environmental Quality Standard for soils (GB ), the maximum permissible concentration of both HCHs and DDTs in the soil should be less than the second grade (500 ng/g dw) in order concentration ng/g 2.50 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 site α-hch β-hch γ-hch δ-hch α-/γ-hch ratio Fig. 2. Compositions and sources of HCHs in Sanduao Bay and Xinghua Bay.

5 J. Zhang et al. / Journal of Geochemical Exploration 125 (2013) concentration ng/g ratio S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 site o,p'-ddt p,p'-dde p,p'-ddd p,p'-ddt DDD/DDE (DDD+DDE)/(p,p'-DDT+DDD+DDE) o,p'-/p,p'-ddt Fig. 3. Compositions and sources of DDTs in Sanduao Bay and Xinghua Bay. to ensure the safety of agricultural products and prevent food contamination by HCHs and DDTs, which can be detrimental to human health. The first grade (50 ng/g dw) was set by the Guideline of Chinese Environmental Quality Standard in terms of protecting regional ecology and maintaining the natural environmental background. In the study area, HCHs concentrations in all soil samples met the first grade while DDTs concentrations in 20 out of 21 soil samples (95.2%) met the first grade. However, 4.7% were between the first and the second first grade. In terms of the soil protection guideline of Netherlands (Gong et al., 2004b; Zhang et al., 2006), the concentrations of HCHs in most of the soil samples collected in this study were significantly lower than the limit for unpolluted soil (b10 ng/g). However, the concentrations of DDTs in 18 of 21 soil samples (85.7%) in the present study were higher than the limit for unpolluted soil (b2.5 ng/g). When compared to both China and Netherlands guidelines, HCHs pollution in agricultural soil along Sanduao Bay and Xinghua Bay can be considered as unpolluted, but DDTs pollution pointed out a potential pollution risk. Although no remediation measures were required with respect to the soil OCPs residues in soil along Sanduao Bay and Xinghua Bay, the ecological and health effects of these endocrine disruptive pollutants through food chain should deserve concern in light of their possible biological magnifications in higher trophic organisms including human beings. 4. Conclusions Concentrations of OCPs have been measured in 21 surface soil samples (0 20 cm) collected along Sanduao Bay and Xinghua Bay, southeast China. The total concentrations of OCPs in soil samples of Sanduao Bay and Xinghua Bay were in the range of ng/g, ng/g, respectively. The mean concentrations of two bays were in the order: DDTs>HCHs>endosulfans>chlordanes. HCHs in these study areas may be have been received fresh lindane. 85.7% soil along Sanduao Bay and Xinghua Bay use technical DDT in these areas for a long time. But, the soils in X4, X5, and X6 from Xinghua Bay were the historical application of technical DDT. There were all weak correlations between TOC contents and residues of HCHs, DDTs, chlordane and endosulfan, indicating that TOC could not be the only factor with enhanced adsorption of these compounds. In general, soil properties such as TOC alone could not fully explain the adsorption of target OCPs into soil, suggesting rather complex behaviors between soil properties and OCPs residues. Acknowledgments This work was supported by National Natural Science Foundation of China (no ), the College Science Technology Research a HCHs ng/g R 2 = DDTs ng/g R 2 = chlordanes ng/g R 2 = endosulfan ng/g R 2 = b HCHs ng/g R 2 = DDTs ng/g R 2 = chlordanes ng/g R 2 = endosulfan ng/g R 2 = Fig. 4. Relationship between OCPs and TOC in surface soils along Sanduao Bay (a) and Xinghua Bay (b).

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