Organochlorine pesticides (OCPs) are characterized by ubiquity, bioaccumulation and persistence in the environment and are of worldwide concern. Sixteen surface sediment samples were analyzed for hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) to provide information on the levels, distribution and sources of these compounds after flood season in the old Yellow River Estuary, China. The concentrations of ΣDDT were considerably lower than those of ΣHCH. The concentrations of ΣHCH and ΣDDT in sediments after flood season were lower than those in sediments before flood season. The distribution indicated that the levels of HCHs and DDTs from sites near the beach were higher than those in the other sites. The principal component analysis suggested the usage of HCHs could serve as input sources for OCPs. The cluster analysis suggested that there were some similar migration characteristics and similar origins among these pesticides. O'p-DDT and o'p-DDT is of the greatest concern for the ecotoxicological risk.

INTRODUCTION

Organochlorine pesticides (OCPs) have been extensively studied due to their ubiquity, bioaccumulation and persistence in the environment (Yang et al. 2005). Technical hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs), typical OCPs were the most extensively used pesticides in China between the 1950s and 1983, resulting in widespread contamination in various environmental compartments (Wu et al. 2013). The residence time of OCPs in the environment is notably long, and sediment is an important reservoir of OCPs (Pandit et al. 2006). These compounds can enter marine and freshwater ecosystems through effluent release, atmospheric deposition, runoff (Zhou et al. 2001) and can be adsorbed on suspended particulate matter due to their high hydrophobicity and low water solubility, thereby accumulating in sediments (Wang et al. 2013). The compounds may be transferred to higher trophic levels through the food chain. Some previous literature has also reported studies on OCPs in the sediments. For example, Tang et al. (2013) have studied OCPs in the lower reaches of Yangtze River, China; Tan et al. (2009) have reported distribution and sources of pesticides in water and sediments from Daliao River Estuary of Liaodong Bay, Bohai Sea, China; Pazi et al. (2012) have studied the occurrence and distribution of organochlorine residues in surface sediments of the Candarli Gulf (Eastern Aegean); Mishra et al. (2013) have reported the contamination profile of DDT and HCH in surface sediments and their spatial distribution from North-East India. Up to now, there are no studies on OCPs in the sediment from the old Yellow River Estuary, China.

The old Yellow River Estuary in Dongying City, Shandong Province, China is an estuary through which the Yellow River fed into the Bohai Sea from 1855 to 1976. The Yellow River Estuary is a new river channel, which is in the diversion of the river after the artificial diversion in 1976. The Yellow River Estuary is below Lijin, which is a weak tidal estuary continental. The annual flood season generally occurs in July or August in this area. The massive oil field exploitation and the large water conservancy project construction around the coastal regions has resulted in severe environmental stress. In the past, the development of the surrounding agriculture led to the massive use of pesticides and caused environmental pollution. To the best of our knowledge, there are few studies on the contamination of OCPs in sediment of the old Yellow River Estuary. In our previous studies, we have also reported OCPs in the surface sediments and a sediment core from the Yellow River Estuary, OCPs in surface soils from the nature reserve of the Yellow River delta before flood season (Da et al. 2013, 2014a, b). The present work is a small-scale survey of the contamination status and spatial distribution of HCHs and DDTs in the sediments after flood season from the old Yellow River Estuary. The study seeks to understand the distribution of HCHs and DDTs in surface sediment and to analyze the pollution source, as well as the potential biological risk, of these compounds in this area.

MATERIALS AND METHODS

Sampling

A total of 16 surface sediment samples were collected with a stainless steel grab from the old Yellow River Estuary in August 2013. The sampling time was just after flood season of the Yellow River Estuary. The sampling sites are shown in Figure 1. The sediments were collected with a stainless steel grab. All the samples were wrapped with aluminum foil and mixed separately and stored at −20 °C in prewashed glass bottles until analysis.
Figure 1

Map of sampling locations of the sediments.

Figure 1

Map of sampling locations of the sediments.

Sample preparation and extraction

Extraction methods of OCPs in sediment samples were based on EPA3540. The samples were freeze-dried, hand-sieved (200 μm) and homogenized. Approximately 20 g of homogenized sample was extracted in a Soxhlet apparatus with 200 mL of dichloromethane for 48 hours. Activated copper was added for desulfurization. The extractor water bath temperature was maintained at 49 °C. Extracts were then rotary evaporated to 2 mL, and 10 mL n-hexane was added to solvent-exchange and was further reduced to 1–2 mL by rotary evaporation. The alumina/silica (v/v = 1:2) gel column was eluted with 70 mL of dichloromethane/hexane (v/v = 3/7) for OCPs. The eluate was concentrated to 1 mL by rotary evaporation.

Instrumental analysis

The determination of the OCPs was quantified with an Agilent 6890 Series gas chromatography system connected to an Agilent 5973 Network Mass Spectrometer Selective Detector (GC-MS). Samples (1 μL) were auto injected in splitless mode, and the separation was performed with a DB-5 MS fused silica capillary column (30 × 0.25 × 0.25 mm). The carrier gas was helium (99.999%) at flow rate of 1.0 mL min−1. The MS was operated in EI+ mode with selected ion monitoring, and the electron energy was 70 eV. The column oven temperature was programmed at an increasing rate of 15 °C min−1 from an initial temperature of 80 °C for 1 minute, ramping at a rate of 12 °C minute−1 to 200 °C for 10 minutes, to 220 °C at 1 °C minute−1 and maintaining for 5 minutes and to a final temperature of 290 °C at 15 °C minute−1 with a final holding time of 5 minutes.

Quality control

The residue levels of OCPs were quantitatively determined by the internal standard method using peak area. The correlation coefficients of calibration curves of OCPs were all higher than 0.998. Instrumental detection limits (DLs) were determined from linear extrapolation from the lowest standard in the calibration curve using the area of a peak having a signal-to-noise ratio of 3, which ranged from 0.5 to 1 ng g−1 for OCPs. The spiked levels were close to, or below, DL. For every set of ten samples, procedural blanks, spiked blanks and replicate samples were run to check for interference and cross-contamination. The spiked recoveries of OCPs were in the range of 85–102% and the relative standard deviation values ranged from 2 to 10%.

Principal component analysis and cluster analysis

As these pesticides may come from the same sources and have similar environmental behavior; therefore, they may display some correlations. The correlations for these pesticides are expressed by multivariate statistics such as principal component analysis (PCA) and cluster analysis (CA). The analysis was performed with SPSS11.0 for Windows. PCA is used to explore the relationship of the measured parameters and facilitate the assessment of potential input sources (Hu et al. 2009). CA is used to classify the observation variables so that the common characteristic variables are gathered together.

RESULTS AND DISCUSSION

Residues of HCHs and DDTs in sediments

The concentrations of HCHs and DDTs are summarized in Table 1. The detection frequencies for the HCHs and DDTs in the samples were 93.8% and 36.5%, respectively, indicating a wide occurrence of HCHs in the sediments from the old Yellow River. Based on dry weight, the residues of HCHs and DDTs ranged from 2.54 ng g−1 to 13.91 ng g−1 (mean = 7.52 ng g−1) and 0.016 ng g−1 to 2.54 ng g−1 (mean = 0.45 ng g−1), respectively. The concentrations of DDTs were much lower than those of the HCHs. This trend is not consistent with the previous observations on the contamination of OCPs in sediments of Bohai Sea and Daya Bay, China (Ma et al. 2001; Zhou et al. 2001). According to the literature, the differences and resemblances of OCPs were mainly caused by historic usage, physicochemical properties, silt and organic matter (Wu et al. 2013). However, this trend is consistent with the contamination of OCPs in sediments in the Qiantang River, China (Zhou et al. 2006). The most likely explanation for the relatively higher concentrations of HCHs is that the amount of HCHs used was significantly larger than that of DDTs. According to the literature, HCHs were used in larger quantities than DDTs in the past in China (Wu et al. 2013).

Table 1

Concentration of OCPs (ng/g dw) in surface sediments

Sample codeα-HCHβ-HCHγ-HCHδ-HCH∑HCHo'p-DDEp'p-DDEo'p-DDTp'p-DDTp'p-DDDo'p-DDD∑DDT
S1 1.30 3.57 1.56 n.d. 6.43 0.10 0.11 0.34 1.09 0.43 0.25 2.32 
S2 2.73 4.34 1.32 n.d. 8.39 n.d. n.d. n.d. 0.02 n.d. n.d. 0.02 
S3 1.68 3.02 n.d. n.d. 4.70 0.02 n.d. 0.05 n.d. n.d. n.d. 0.08 
S4 4.56 1.28 1.30 0.12 7.26 n.d. n.d. n.d. n.d. n.d. 0.11 0.11 
S5 3.79 5.26 1.83 0.06 10.94 n.d. 0.02 0.03 0.06 n.d. n.d. 0.115 
S6 3.42 4.72 0.76 8.90 n.d. 0.03 0.11 n.d. n.d. n.d. 0.14 
S7 0.41 3.59 0.56 n.d. 4.56 n.d. n.d. n.d. n.d. n.d. n.d. n.d. 
S8 0.53 11.00 1.16 1.22 13.91 n.d. n.d. 0.03 0.28 0.11 n.d. 0.42 
S9 2.40 4.82 0.85 0.8 8.87 n.d. n.d. n.d. 0.03 n.d. 0.02 0.05 
S10 0.51 3.90 0.87 0.89 6.17 n.d. n.d. n.d. n.d. 0.09 n.d. 0.09 
S11 1.31 2.99 n.d. 0.67 4.97 n.d. n.d. 0.011 n.d. 0.05 n.d. 0.07 
S12 2.37 5.50 0.81 0.62 9.30 n.d. n.d. n.d. n.d. n.d. n.d. n.d. 
S13 2.67 4.44 0.74 0.61 8.46 n.d. n.d. n.d. n.d. 0.09 n.d. 0.09 
S14 2.88 4.71 1.36 0.20 9.15 n.d. 0.03 n.d. n.d. n.d. n.d. 0.03 
S15 0.45 1.53 0.56 n.d. 2.54 0.07 0.13 0.45 0.33 n.d. 0.12 1.09 
S16 1.94 3.09 0.87 n.d. 5.90 n.d. 0.21 0.71 1.10 0.30 0.22 2.54 
Sample codeα-HCHβ-HCHγ-HCHδ-HCH∑HCHo'p-DDEp'p-DDEo'p-DDTp'p-DDTp'p-DDDo'p-DDD∑DDT
S1 1.30 3.57 1.56 n.d. 6.43 0.10 0.11 0.34 1.09 0.43 0.25 2.32 
S2 2.73 4.34 1.32 n.d. 8.39 n.d. n.d. n.d. 0.02 n.d. n.d. 0.02 
S3 1.68 3.02 n.d. n.d. 4.70 0.02 n.d. 0.05 n.d. n.d. n.d. 0.08 
S4 4.56 1.28 1.30 0.12 7.26 n.d. n.d. n.d. n.d. n.d. 0.11 0.11 
S5 3.79 5.26 1.83 0.06 10.94 n.d. 0.02 0.03 0.06 n.d. n.d. 0.115 
S6 3.42 4.72 0.76 8.90 n.d. 0.03 0.11 n.d. n.d. n.d. 0.14 
S7 0.41 3.59 0.56 n.d. 4.56 n.d. n.d. n.d. n.d. n.d. n.d. n.d. 
S8 0.53 11.00 1.16 1.22 13.91 n.d. n.d. 0.03 0.28 0.11 n.d. 0.42 
S9 2.40 4.82 0.85 0.8 8.87 n.d. n.d. n.d. 0.03 n.d. 0.02 0.05 
S10 0.51 3.90 0.87 0.89 6.17 n.d. n.d. n.d. n.d. 0.09 n.d. 0.09 
S11 1.31 2.99 n.d. 0.67 4.97 n.d. n.d. 0.011 n.d. 0.05 n.d. 0.07 
S12 2.37 5.50 0.81 0.62 9.30 n.d. n.d. n.d. n.d. n.d. n.d. n.d. 
S13 2.67 4.44 0.74 0.61 8.46 n.d. n.d. n.d. n.d. 0.09 n.d. 0.09 
S14 2.88 4.71 1.36 0.20 9.15 n.d. 0.03 n.d. n.d. n.d. n.d. 0.03 
S15 0.45 1.53 0.56 n.d. 2.54 0.07 0.13 0.45 0.33 n.d. 0.12 1.09 
S16 1.94 3.09 0.87 n.d. 5.90 n.d. 0.21 0.71 1.10 0.30 0.22 2.54 

In addition, the concentrations of HCHs and DDTs in this study were much lower than those of HCHs and DDTs in the surface sediments from the Yellow River Estuary in our previous studies (Da et al. 2013), the concentrations of HCHs and DDTs in this study were higher than those of HCHs and DDTs in a sediment core from the Old Yellow River Estuary in our previous studies (Da et al. 2014a). In this study, the sampling time was after flood season of the Yellow River Estuary, the floods wash away sediment, and also wash away HCHs and DDTs, therefore, the concentrations of ∑HCH and ∑DDT in sediments after flood season were lower than those of HCHs and DDTs in the surface sediments before flood season in July 2012 (Da et al. 2013). It was very interesting that the concentrations of HCHs and DDTs in the surface core were lower than those of HCHs and DDTs in the bottom core in our previous study (Da et al. 2014a). However, the concentrations of HCHs and DDTs in the surface sediments in this study were higher than the average concentrations of HCHs and DDTs in the sediment core (Da et al. 2014a). Thus, we speculated that the concentration of HCHs and DDTs in the bottom sediment was higher than the average concentration (HCHs: 7.52 ng g−1, DDTs: 0.45 ng g−1) of HCHs and DDTs in the surface sediment from the sixteen sampling sites.

The residues of HCHs in this study area are relatively lower than, or similar to, those in the Daling River area (1.1–30 ng g−1) (Wang et al. 2013), the Pearl River (1.20–17.0 ng g−1) (Mai et al. 2002) and the Haihe Estuary (0.997–36.1 ng g−1) (Zhao et al. 2010) but higher than those in the Bohai Sea (0.16–3.17 ng g−1) (Hu et al. 2009) and Laizhou Bay (0.03–6.38 ng g−1) (Zhong et al. 2011). In the case of DDTs, the concentrations are similar to those in the East China Sea (0.06–6.04 ng g−1) (Yang et al. 2005) but lower than those in Yueqing Bay (1.85–16.54 ng g−1) (Yang et al. 2010), the Pearl River Delta Estuary (3.8–31.7 ng g−1) (Zhang et al. 2002; Wang et al. 2007) and Bohai Bay (0.20–11.1 ng g−1) (Wan et al. 2005). In general, the levels of DDTs and HCHs were relatively lower than or similar to those in other Chinese rivers.

Distributions of HCHs and DDTs

The spatial distributions of DDTs and HCHs are shown in Figure 2. The concentrations of OCPs varied among sampling locations. The residues of OCPs from sites near the beach (S5, S8) were higher than those in the other sites. This is consistent with the distributions of OCPs in surface sediments from the East China Sea (Yang et al. 2005). The distribution difference can be caused by many possible factors such as historic usage, physicochemical properties, silt and organic matter (Yang et al. 2005). This relationship was also found in a previous study. We also found that the concentration of HCHs in all the sites was higher than those of DDTs. The different concentration can be caused by many possible factors, such as historic usage and the degradation and accumulation mechanisms of HCHs and DDTs (Yang et al. 2005). Meanwhile, more attention should be paid to the source of HCHs in the site at S8. The river inflow and surface runoff might be responsible for the high concentrations of HCHs in this site (Wang et al. 2013).
Figure 2

The concentration of HCHs and DDTs in surface sediments.

Figure 2

The concentration of HCHs and DDTs in surface sediments.

Compositions and sources of HCHs and DDTs

Hexachlorocyclohexanes

In China, technical HCHs and lindane have been widely used. Technical HCHs were extensively applied in agriculture from the 1950s to the early 1980s (Wang et al. 2013), whereas lindane (γ-HCH 99.9%) was used for controlling pests from the 1990s (Wang et al. 2013). These isomers have different physicochemical properties. β-HCH is more resistant to hydrolysis and environmental degradation, whereas α-HCH is more likely to partition to the air and be transported over long distances (Hitch & Day 1992). Moreover, α-HCH and γ-HCH can be transformed into β-HCH (Hitch & Day 1992); therefore, β-HCH would be the predominant isomer if there were no fresh input of HCH. The ratio of α-HCH/γ-HCH would be less than 3 for lindane and in the range of 3–7 for technical HCH (Yang et al. 2010). Therefore, this ratio can identify the sources of HCHs (Yang et al. 2008).

The average percentages of the different isomers are shown in Figure 3(a). β-HCH is the predominant isomer and exists in all of the samples. The isomers of α-HCH, β-HCH, γ-HCH and δ-HCH were observed to contribute approximately 28.1%, 57.1%, 8.0% and 6.7%, respectively. Compared with its original components (Wang et al. 2013), the compositions have changed significantly. The higher percentage of β-HCH may be due to the properties of lower vapor pressure and less degradability. In addition, α-HCH and γ-HCH could be transformed into β-HCH over time. The high percentage of β-HCH indicates that HCH residues are derived mainly from the historical usage of HCH. The high percentage of β-HCH in the sediments was also recorded in other study areas, including the East China Sea (Yang et al. 2005), the Daliao River Estuary (Tan et al. 2009), the Minziang River Estuary (Zhang et al. 2003), Baiyangdian Lake (Dai et al. 2011), South India (Senthilkumar et al. 2001) and the Yangtze River (Tang et al. 2013).
Figure 3

Compositions of HCH and DDT in the surface sediments.

Figure 3

Compositions of HCH and DDT in the surface sediments.

The ratios of α-HCH/γ-HCH in the samples were in the range of 0.45–4.5 with 68.8% of samples with a value of less than 3. This result confirmed that lindane was the major source, and the use of technical HCHs was the minor source. Our result is consistent with the sources of HCHs in sediments from Baiyangdian Lake, China (Dai et al. 2011). However, the low α/γ-HCH ratio was observed in some other study regions, implying that only lindane emission sources existed (Zhang et al. 2011; Tan et al. 2009; Sun et al. 2010).

Dichlorodiphenyltrichloroethanes

The use of DDTs was officially banned in 1983 but was terminated in 2000 in China (Tao et al. 2007). After the ban of DDTs, the use of the pesticide dicofol with a high impurity of DDT compounds has been applied (Liu et al. 2008). The ratios between parent DDT compounds and their metabolites can provide important information on the source of DDTs (Zhang et al. 2011). A ratio of (DDE + DDD)/DDTs >0.5 can be thought to be subjected to aged DDTs, and a ratio <0.5 indicates fresh DDTs (Zhang et al. 1999). Ratios of DDD/DDE >1 indicate that the anaerobic degradation is the main pathway of DDT loss, whereas ratios <1 imply the presence of aerobic degradation (Wu et al. 2013). The ratios of o′p-DDT/p′p-DDT range from 0.2 to 0.3 for technical DDTs and from 1.3 to 9.3 for dicofol (Qiu et al. 2005; Yang et al. 2010).

The compositions of the DDTs are shown in Figure 3(b), which shows that the concentrations of p′p-DDT were much higher than o′p-DDT in most of the samples. Similarly, p′p-DDE and p′p-DDD were slightly higher than o′p-DDE and o′p-DDD. Moreover, p′p-DDT was the predominant isomer and existed in most of the sampling sites. This is consistent with industrial DDT composition (Bopp 1982). The dominance of p′p-DDT in sediments was also reported from the Nagaon and Dibrugarh, North-East India (Mishra et al. 2013), the Yangtze River, China (Tang et al. 2013) and the Candarli Gulf, Eastern Aegean (Pazi et al. 2012). The mean ratio of (DDE + DDD)/DDT was 0.51, with 62.3% of the ratio values greater than 0.5, which could be thought to be subjected to the degradation of historical DDTs. The ratios of DDD/DDE were in the range of 0–3.23, with 68.8% of the values being greater than 1, indicating that the biodegraded condition of DDT was anaerobic. The ratios of o′p-DDT/p′p-DDT range of 1.3–9.3 comprised 62.5% of all samples, which suggested that both the dicofol-type DDTs and the technical DDT application may be present. However, possible point pollution sources could not be excluded based on the results described above. Several recent studies reported high DDT residues in human breast and animal tissues, and revealed a new input of DDTs, especially in South China. These pollution events usually occur on a relatively small scale and are driven by water runoff (Yang et al. 2005).

Correlation between HCHs and DDTs

The results of CA is presented in Figure 4. All pesticides were divided into three groups. The presence of p′p-DDE, p′p-DDT, o′p-DDD and p′p-DDD residues in the first group suggests they have similar migration characteristics. The presence of β-HCH and δ-HCH residues in the second group indicates that there is a similar exposure pathway between them. The presence of γ-HCH, o′p-DDT and α-HCH residues in the third group indicates a correlation among these compounds.
Figure 4

Clustering tree diagram of the pesticides.

Figure 4

Clustering tree diagram of the pesticides.

The results of PCA are presented in Table 2. The three principal components accounted for 87.5% of the total variance. The high positive loadings of α-HCH, β-HCH and γ-HCH in the same group of PCF1 (44.6%) suggest HCH isomers serve as input sources for OCPs. O′p-DDE, o′p-DDT, p′p-DDE and p′p-DDT in the same group of PCF2 (28.7%) suggests the occurrence status of these pesticides. The sedimentary condition in these areas is aerobic due to the opened setting. The input of DDTs could be more easily degraded into DDE under anoxic condition, indicating a common appearance of DDT and DDE in PCF2. As for PCF3 (14.2%), the loadings of δ-HCH, o′p-DDD and p′p-DDD suggest these pesticides have similar migration characteristics.

Table 2

Factor loadings for principal component analysis for OCPs

PesticidesComponent
PCF-1PCF-2PCF-3
α-HCH 0.841 0.154 0.158 
β-HCH 0.812 − 0.321 0.126 
γ-HCH 0.771 0.123 − 0.365 
δ-HCH − 0.021 0.013 0.728 
o′p-DDE 0.113 0.868 0.143 
o′p-DDD 0.315 0.189 0.723 
o′p-DDT 0.116 0.756 0.021 
p′p-DDE 0.123 0.749 − 0.023 
p′p-DDD 0.101 0.129 0.823 
p′p-DDT 0.203 0.854 0.012 
% of variance 44.6 28.7 14.2 
Cumulative % 44.6 73.3 87.5 
PesticidesComponent
PCF-1PCF-2PCF-3
α-HCH 0.841 0.154 0.158 
β-HCH 0.812 − 0.321 0.126 
γ-HCH 0.771 0.123 − 0.365 
δ-HCH − 0.021 0.013 0.728 
o′p-DDE 0.113 0.868 0.143 
o′p-DDD 0.315 0.189 0.723 
o′p-DDT 0.116 0.756 0.021 
p′p-DDE 0.123 0.749 − 0.023 
p′p-DDD 0.101 0.129 0.823 
p′p-DDT 0.203 0.854 0.012 
% of variance 44.6 28.7 14.2 
Cumulative % 44.6 73.3 87.5 

Potential biological effects of OCPs

The effects range-low value (ERL) and the effects range-median value (ERM) have been used to predict potential impacts of contaminants in sediments (Yang et al. 2010). The threshold effects level (TEL) and probable effects level (PEL) were applied to evaluate the possible ecotoxicological risks of OCPs (Wu et al. 2013). The evaluated values of selected OCPs are shown in Table 3. The concentrations of all assessed compounds were lower than the ERM. The concentration of DDT (o′p-DDT and p′p-DDT) and the DDTs were higher than the ERL values for six samples and two samples of all samples, respectively, suggesting DDTs had potential impacts of contaminants. The PEL and TEL values may cause adverse biological risk to the environment (Hu et al. 2009; Sun et al. 2010). The concentrations of γ-HCH were higher than TEL and PEL in 87.5% and 37.5% of the samples, respectively, suggesting that sediments were polluted with γ-HCH. Secondly, the concentrations of DDT were higher than TEL and PEL in 31.2% and 6.3% of the samples, respectively. Compared to γ-HCH, DDT has relatively high soil sorption coefficients and low water solubility; thus DDTs are more likely to partition into environmental sectors which exhibit greater organic phases. Moreover, DDT has higher aquatic toxicity, higher biota accumulation and longer persistence than γ-HCH (Chen et al. 2011). Therefore, more ecotoxicological concern should be paid to o′p-DDT and p′p-DDT. According to the above analysis, slight potential health risks may exist to organisms in this area.

Table 3

Assessments of potential biological risks of selected OCPs in surface sediments using two sediment quality guidelines

ChemicalRange (ng·g−1)ERLAbove ERL (%)ERMAbove ERM (%)TELAbove TEL (%)PELAbove PEL (%)
o′p-DDT and p′p-DDT 0–6 37.5 1.19 31.25 4.47 6.25 
p′p-DDE 0–0.21 2.2 27 1.22 7.81 
p′p-DDD 0–0.43 20 2.07 374 
DDT 0–2.54 1.58 12.5 46.1 3.89 51.7 
γ-HCH 0–1.83 – – – – 0.32 87.5 0.99 37.5 
ChemicalRange (ng·g−1)ERLAbove ERL (%)ERMAbove ERM (%)TELAbove TEL (%)PELAbove PEL (%)
o′p-DDT and p′p-DDT 0–6 37.5 1.19 31.25 4.47 6.25 
p′p-DDE 0–0.21 2.2 27 1.22 7.81 
p′p-DDD 0–0.43 20 2.07 374 
DDT 0–2.54 1.58 12.5 46.1 3.89 51.7 
γ-HCH 0–1.83 – – – – 0.32 87.5 0.99 37.5 

CONCLUSIONS

In the present work, the concentrations of ∑DDT were much lower than those of ∑HCH. The concentrations of ∑HCH and ∑DDT in sediments after flood season were lower than those in sediments before flood season. Compared with the other riverine/estuarine in China, the levels of DDTs and HCHs were relatively lower or similar. The residue of OCPs from sites near the beach was higher than those in the other sites. PCA suggested that the usage of HCHs could serve as input sources. CA suggested that there were some similar migration characteristics among these pesticides. O′p-DDT and p′p-DDT would be of greater concern for their ecotoxicological risk in this study area.

ACKNOWLEDGEMENTS

This work is supported by the National Natural Science Foundation of China (no. 41173032), National Science and Technology Support Program (1012BAC10B02), Programs of Huainan Mining Industry (Group) Co., Ltd,the National Natural Science Foundation of Anhui Provincial Education Department (KJ2014A216), Anhui Provincial Natural Science Foundation (1508085QD72). Special thanks are given to anonymous reviewers for their useful suggestions and comments.

REFERENCES

REFERENCES
Chen
W.
Jing
M. M.
Bu
J. W.
Ellis Burnet
J. E.
Qi
S. H.
Song
Q.
Ke
Y. B.
Miao
J. J.
Liu
M.
Yang
C.
2011
Organochlorine pesticides in the surface water and sediments from the Peacock River Drainage Basin in Xinjiang, China: a study of an arid zone in Central Asia
.
Environ. Monit. Assess.
177
,
1
21
.
Da
C. N.
Liu
G. J.
Yuan
Z. J.
2014a
Analysis of HCHs and DDTs in a sediment core from the Old Yellow River Estuary, China
.
Ecotox. Environ. Safe.
100
,
171
177
.
Hitch
R. K.
Day
H. R.
1992
Unusual persistence of DDT in some western USA soils
.
Bull. Environ. Contam. Toxicol.
48
,
259
264
.
Liu
M.
Cheng
S. B.
Ou
D. N.
Yang
Y.
Liu
H. L.
Hou
L. J.
Gao
L.
Xu
S. Y.
2008
Organochlorine pesticides in surface sediments and suspended particulate matters from the Yangtze estuary, China
.
Environ. Pollut.
156
,
168
173
.
Mai
B. X.
Fu
J. M.
Sheng
G. Y.
Kang
Y. H.
Lin
Z.
Zhang
G.
Min
Y. S.
Zeng
E. Y.
2002
Chlorinated and polycyclic aromatic hydrocarbons in riverine and estuarine sediments from Pearl River Delta, China
.
Environ. Pollut.
117
,
457
474
.
Qiu
X. H.
Zhu
T.
Yao
B.
Hu
J. X.
Hu
S. W.
2005
Contribution of dicofol to the current DDT pollution in China
.
Environ. Sci. Technol.
39
,
4385
4390
.
Wang
J.
Guo
L. L.
Li
J.
Zhang
G.
Lee
C. S. L.
Li
X. D.
Jones
K. C.
Xiang
Y. R.
Zhong
L. J.
2007
Passive air sampling of DDT, chlordane and HCB in the Pearl River Delta, South China: implications to regional sources
.
J. Environ. Monit.
9
,
582
588
.
Wang
L.
Jia
H. L.
Liu
X. J.
Sun
Y. Q.
Yang
M.
Hong
W. J.
Qi
H.
Li
Y. F.
2013
Historical contamination and ecological risk of organochlorine pesticides in sediment core in northeastern Chinese river
.
Ecotox. Environ. Safe.
93
,
112
120
.
Yang
R. Q.
Yao
T. D.
Xu
B. Q.
Jiang
G. B.
Zheng
X. Y.
2008
Distribution of organochlorine pesticides (OCPs) in conifer needles in the southeast Tibetan Plateau
.
Environ. Pollut.
153
,
92
100
.
Zhang
G.
Min
Y. S.
Mai
B. X.
Sheng
G. Y.
Fu
J. M.
Wang
Z. S.
1999
Time trend of BHCs and DDTs in a sedimentary core in Macao estuary, Southern China
.
Mar. Pollut. Bull.
39
,
326
330
.
Zhang
G.
Parker
A.
House
A.
Mai
B.
Li
X.
Kang
Y.
Wang
Z.
2002
Sedimentary records of DDT and HCH in the Pearl River Delta, south China
.
Environ. Sci. Technol.
36
,
3671
3677
.
Zhang
J. Q.
Qi
S. H.
Xing
X. L.
Tan
L. Z.
Gong
X. Y.
Zhang
Y.
Zhang
J. P.
2011
Organochlorine pesticides (OCPs) in soils and sediments, southeast China, a case study in Xinghua Bay
.
Mar. Pollut. Bull.
62
,
1270
1275
.
Zhong
G.
Tang
J.
Zhao
Z.
Pan
X.
Chen
Y.
Li
J.
Zhang
G.
2011
Organochlorine pesticides in sediments of Laizhou Bay and its adjacent rivers, North China
.
Mar. Pollut. Bull.
62
,
2543
2547
.