Bull Environ Contam Toxicol (2014) 93:580–585 DOI 10.1007/s00128-014-1387-2
Occurrence, Distribution and Sources of Organochlorine Pesticides (OCPs) in Surface Sediments from the Lijiang River, a Typical Karst River of Southwestern China Dan Zhang • Yinghui Wang • Kefu Yu Pingyang Li • Ruijie Zhang • Yiyin Xu
•
Received: 13 January 2014 / Accepted: 17 September 2014 / Published online: 27 September 2014 Ó Springer Science+Business Media New York 2014
Abstract The Lijiang River is a typical karst river of southwestern China. Karst-aquifer systems are more vulnerable to contamination compared to other types of aquifers. The occurrence and distribution of organochlorine pesticides (OCPs) in surface sediments from the Lijiang River were investigated to evaluate their potential ecological risks. The total concentrations of them in sediments ranged from 0.80 to 18.73 ng/g dry weight (dw) (mean 6.83 ng/g dw). The residue levels of OCPs varied in the order of HCB [ HCHs [ DDTs. Compositional analyses of OCPs showed that HCHs and DDTs were mainly from historical usage. The ecological risk assessment suggested that HCHs and DDTs in Lijiang River sediments may cause adverse ecological risks, particularly at sites near agricultural areas. Keywords Lijiang River Karst river OCPs Sediment contamination Ecological risk Organochlorine pesticides (OCPs) are of great concern around the world, due to their impact on non-target organisms, persistence in the environment, and bioaccumulation in the tissues of animals as well as humans via the
D. Zhang Y. Wang (&) K. Yu P. Li R. Zhang Coral Reef Research Center, Guangxi University, Nanning 530004, China e-mail: [email protected] D. Zhang Y. Wang P. Li R. Zhang School of Environment, Guangxi University, Nanning 530004, China Y. Xu Scientific Research Academy of Guangxi Environmental Protection, Nanning 530004, China
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food chain (Hu et al. 2011; Sojinu et al. 2012). Although the residue levels of OCPs in the environment have considerably declined in the past 30 years (Wang et al. 2012), their long half-lives (DT50-values) and potential adverse effects present a significant threat to the environment. Due to the low solubility in water and high organic carbon partition coefficient values (Koc), OCPs are easily adsorbed on suspended particulate matters and subsequently deposited in sediments. Once disturbed, sediments can be resuspended and the contaminants can reenter the aquatic environment and circulate in ecosystems, resulting in a secondary contamination (Veses et al. 2012; Wu et al. 2013). An investigation of the distribution of OCPs in surface sediments can be notably significant because sediments act both as a pollutant sink and as a secondary contamination source. Approximately one-third of China is karstic. The most extensive karst areas are in southwestern China, including Guangxi. Guilin City, which is located in the northeast of Guangxi, hosts the most typical karst landforms in southwestern China and has important high-quality karst water resources (Guo et al. 2010). Karst regions are characterized by unique surface and subsurface features and complex interactions with the atmosphere, hydrosphere and biosphere. Karstaquifer systems are more vulnerable to contamination compared to other types of aquifers (Guo et al. 2010). Moreover, contaminants introduced into karst aquifers often extended over large distances (Guo et al. 2010). Besides, numerous karst features facilitate the exchange of contaminants between surface and ground waters and the groundwater resources are sensitive to surface water contaminants (Bailly-Comte et al. 2008). The Lijiang River covers an area of 5,585 km2 and flows a distance of about 437 km from the north of Guilin City to the south. It is the main source of drinking water in Guilin City. With the intensive agriculture in Guilin City, large
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Table 1 OCPs concentrations and basic statistical data in surface sediments from the Lijiang River (ng/g dw) OCPs
S01
S02
S03
S04
S05
S06
S07
S08
Range
Mean
SD
DL
DT50 (days)
HCB
0.61
1.44
0.35
2.88
4.83
1.22
0.35
3.49
0.35–4.83
1.90
1.55
0.05
6,051
Heptachlor
ndc
nd
0.38
0.01
nd
nd
nd
nd
nd–0.38
0.05
0.13
0.01
21,612
Heptachlor epoxide
0.01
nd
0.59
0.03
0.09
0.02
nd
nd
nd–0.59
0.09
0.19
0.01
23,614
Trans-chlordane
nd
0.68
0.90
0.52
1.47
nd
0.29
0.38
nd–1.47
0.53
0.46
0.01
34,543
Cis-chlordane
0.01
0.24
0.31
nd
nd
nd
nd
nd
nd–0.31
0.07
0.12
0.01
34,543
a-endosulfan
0.02
1.42
nd
nd
nd
0.01
0.01
nd
nd–1.42
0.18
0.47
0.01
18,159
b-endosulfan
nd
0.16
0.12
0.02
0.02
nd
nd
nd
nd–0.16
0.04
0.06
0.01
18,159
Aldrin
0.02
nd
1.02
0.01
0.03
nd
nd
3.96
nd–3.96
0.63
1.30
0.01
15,217
Dieldrin
0.03
3.19
1.25
0.06
0.12
0.02
0.06
0.43
0.02–3.19
0.65
1.04
0.02
16,625
Endrin
0.01
1.41
0.88
0.01
0.02
nd
nd
0.44
nd–1.41
0.35
0.50
0.01
16,625
p,p’-DDE p,p’-DDD
0.01 0.04
1.11 1.23
0.01 0.25
0.02 0.03
0.04 0.10
0.01 0.02
0.01 0.03
0.18 2.62
0.01–1.11 0.02–2.62
0.17 0.54
0.36 0.87
0.01 0.01
2,802 2,355
o,p’-DDT
nd
0.01
0.19
0.02
0.01
0.01
nd
0.30
nd–0.30
0.07
0.11
0.01
7,733
p,p’-DDT
nd
0.23
0.10
nd
nd
nd
nd
0.04
nd–0.23
0.05
0.08
0.02
6,767
a-HCH
0.01
0.65
0.98
0.02
0.03
0.05
0.06
0.45
0.01–0.98
0.28
0.35
0.01
3,149
b-HCH
0.02
0.44
0.23
0.04
0.06
0.07
0.09
1.02
0.02–1.02
0.25
0.32
0.01
2,519
c-HCH
0.01
6.14
0.08
0.01
0.01
0.06
0.06
1.13
0.01–6.14
0.94
2.00
0.01
3,149
0.06
0.12
0.03
2,099
1.52
2.45
0.83
1.19
6.83
6.22
d-HCH nd 0.38 0.09 nd nd nd nd nd nd–0.38 P HCHa 0.04 7.61 1.38 0.07 0.10 0.18 0.21 2.60 0.04–7.61 P b DDT 0.05 2.58 0.55 0.07 0.15 0.04 0.04 3.14 0.04–3.14 P OCP 0.80 18.73 7.73 3.68 6.83 1.49 0.96 14.44 0.80–18.73 a P b P HCH = a-HCH ? b-HCH ? c-HCH ? d-HCH; DDT = p,p’-DDE ? p,p’-DDD ? o,p’-DDT detection limit; DT50: half-life; DT50 values (sediment) for OCPs were reported by Shen et al. (2005)
amounts of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and hexachlorobenzene (HCB) were used to protect crops from insects and weeds from the 1950s to 1980s. Other OCPs such as heptachlors, chlordanes, endosulfans and aldrins have been also used in small amounts for agricultural and public health purpose in Guilin City from the 1950s to 1980s (Wang et al. 2011). However, the application of OCPs (beside HCB) has been banned in Guilin City since the 1980s due to their toxicity (Zhang et al. 2006). During recent years, HCB has been applied for controlling the spread of Oncomelania hupensis in Guilin City (Zhang et al. 2006), resulting that karst aquifers are threatened by HCB contamination. Hence it is essential to ascertain the concentrations of OCPs from the Lijiang River, especially in sediments which can integrate OCP exposure over time. The aims of this study were to survey the levels and distribution of OCPs in surface sediments from the Lijiang River, to assess their environmental risks in this region, and to understand their environmental behavior and fate in sediments.
Materials and Methods Sampling was conducted in March 2007 using a stainless steel grab sampler. A total of eight surface sediments
? p,p’-DDT;
c
nd: not detected; DL:
were collected from the Lijiang River. Due to the long half-lives of OCPs (Table 1) (Shen et al. 2005) and the banning of OCPs (beside HCB) in Guilin City in the 1980s (Zhang et al. 2006), the sampling design involving no repeated sampling may reflect the OCP contamination levels in the study area to some degree. Each sediment sample was actually a mixed sample of three sediments randomly collected from an area of around 20 m2 at the centre of the sampling site. These sediments were sampled covering many potential sources of OCP contamination, i.e., agricultural areas, urban areas and sewage treatment plants (Miglioranza et al. 2013; Shi et al. 2011). Details of the sampling sites are shown in Fig. 1. S02 (Mahuang Zhou) and S08 (Wayao) are located near intensive agricultural areas, as well as near the outflow of sewage treatment plants. S03 (Downstream Mahuang Zhou) is the location where Taohua River (a tributary of the Lijiang River) flows into the Lijiang River. Moreover, the main urban settlements are concentrated around S05 (Zi Zhou). The surface sediment samples (top 5 cm) were scooped into pre-cleaned glass jars, and then cooled with ice during transportation to the Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Guangzhou, China where they were stored at -20°C until further analysis.
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rose to 200°C at 4°C/min, then to 230°C at 2°C/min, and at last reached 280°C at a rate of 8°C/min, then held for 15 min. A 2 lL sample was injected into the GC-ECD for analysis. Quantification was based on internal calibration curves made from standard solutions at six concentration levels. The resulting correlation coefficients for the calibration curves of OCPs were all[0.999. A strict regime of quality control was employed before the onset of the sampling and analysis program. Method blanks (solvent) and spiked blanks (standards spiked into solvent) were analyzed. In addition, each sediment sample was analyzed in triplicate (n = 3). The relative standard deviation (RSD) ranged from 4 % to 10 %. The detection limits (DLs) of OCPs were based on a signal-to-noise ratio (S/N) of 3. The DLs of OCPs ranged from 0.01 to 0.05 ng/ g dw (Table 1). The recoveries of TCMX and PCB209 were 69 ± 6 % and 76 ± 7 %, respectively. The data were subjected to statistical analysis. Arithmetic mean and standard deviation values were determined using the SPSS 16.0 statistical software package. Fig. 1 Map of the sampling sites in the investigation area. S01: Yushan Bridge, S02: Mahuang Zhou, S03: Downstream Mahuang Zhou, S04: Jiefang Bridge, S05: Zi Zhou, S06: Lijiang River Bridge, S07: Jingpingshan Bridge, S08: Wayao
Results and Discussion
The procedures for OCPs’ extraction, fractionation and instrumental analysis were described in detail elsewhere (Gong et al. 2007). In brief, sediment samples were homogenized and freeze-dried with vacuum freeze drier before extraction. 10 g of dried sediments were 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 for 24 h. Activated copper granules were added to the collection flask to remove elemental sulfur. The extract was added with anhydrous sodium sulfate and then concentrated by rotary evaporator and solvent exchanged to hexane and further reduced to 2–3 mL. A 1: 2 alumina/silica gel column (both 3 % deactivated with H2O) was used to clean up and fractionate the extract, and OCPs were eluted with 30 mL of hexane/dichloromethane (3:2). The effluents were reduced finally to a volume of 0.2 mL under a gentle gas stream of purified nitrogen. A know quantity of pentachloronitrobenzene (PCNB) was added as an internal standard prior to gas chromatography–electron capture detector (GC–ECD) analysis. OCPs were measured using a HP-6890 gas chromatograph equipped with a 63Ni electron capture detector (GC– ECD) and a HP-5 silica fused capillary column (30 m 9 0.32 mm i.d. 9 0.25 lm film thickness). High purity N2 was used as the carrier gas at a flow rate of 2.5 mL/ min under the constant flow mode. Injector and detector temperatures were maintained at 290 and 300°C, respectively. The oven temperature began at 100°C for 1 min and
The statistical data of OCPs concentrations in sediment samples from the Lijiang River are summarized in Table 1. Due to DT50 values (sediment) for OCPs ranging from 2,099 (d-HCH) to 34,543 days (chlordanes), OCPs concentrations in sediments of the Lijiang River declined to different degrees (Shen et al. 2005). The total concentrations of OCPs were 0.80–18.73 ng/g dw (mean 6.83 ng/g dw). The results show that the concentrations of OCPs varied in different sampling regions. The highest concentration of OCPs was observed at S02 (18.73 ng/g dw), followed by S08 (14.44 ng/g dw). The presence of OCPs (beside HCB) in sediments from the Lijiang River was associated with historical input (Wang et al. 2011). The levels of OCPs in sediments in the present study were compared to those measured in sediments from the Han River, Korea (Kim et al. 2009), the Mekong River, Vietnam (Minh et al. 2007), the Haihe River, China (Yang et al. 2005) and the Tonghui River, China (Zhang et al. 2004). The results show that the contamination of OCPs in sediments of the Lijiang River was at a medium level compared to the other studied rivers. OCPs residue levels varied in the order of HCB [ HCHs [ DDTs. In this study, the concentrations of HCB ranged from 0.35 to 4.83 ng/g dw (mean 1.90 ng/g dw). HCB has never been used directly as a pesticide in China, but it has been used as an intermediate in the synthesis of pentachlorophenol (PCP) and pentachlorophenolNa (PCP-Na). PCP and Na-PCP have been used for more than 30 years in China as either a rice field herbicide or a
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pesticide to control the spread of O. hupensis in many lakes in the southern China (Wen et al. 2008). In order to control the spread of O. hupensis, technical Na-PCP has been sprayed in the Lijiang River (Zhang et al. 2006). There is no chemical plant producing HCB near the sampling locations S01–S08, so the use of Na-PCP near the Lijiang River may contribute to the HCB input. In addition, HCB has relatively high vapor pressure, so long-range transport from chemical plants producing HCB is probably another source in the study area. HCHs and DDTs have been banned from using as pesticides for agricultural purpose in Guilin City since the 1980s (Wang et al. 2011). In this study, the total concentrations of HCHs (a-HCH, b-HCH, c-HCH and d-HCH) ranged from 0.04 to 7.61 ng/g dw (mean 1.52 ng/g dw). The highest concentration of HCHs was observed at S02 (near agricultural areas), showing that large amounts of HCHs have been applied there in the past. A comparison to other studies show that the concentrations of HCHs in sediments of the Lijiang River were lower than those measured in sediments from the Haihe River, China (1.88–18.8 ng/g dw) (Yang et al. 2005), but higher than those of the Tonghui River, China (0.06–0.38 ng/g dw) (Zhang et al. 2004) and the Mekong River, Vietnam (\0.02–1.30 ng/g dw) (Minh et al. 2007). Overall, the data indicate that the contamination of HCHs in sediments of the Lijiang River was at a medium level compared to the other studied rivers. The total concentrations of DDTs (p,p’-DDT, o,p’-DDT, p,p’-DDD and p,p’-DDE) in different sites were in the range of 0.04–3.14 ng/g dw (mean 0.83 ng/g dw). Among DDT and its metabolites, p,p’-DDD (mean 0.54 ng/g dw) was the dominant compound, followed by p,p’-DDE (0.17 ng/g dw) and o,p’-DDT (0.07 ng/g dw). The highest concentration of DDTs was observed at S08 (near agricultural areas) with a concentration up to 3.14 ng/g dw, showing that a relatively larger proportion of DDTs was used at agricultural areas compared to other sites. Compared to other studies, DDTs concentrations in sediments from the Lijiang River were lower than those measured in sediments from the Mekong River, Vietnam (\0.01–110 ng/g dw) (Minh et al. 2007) and the Haihe River, China (0.320–80.2 ng/g dw) (Yang et al. 2005), but comparable to those in sediments of the Tonghui River, China (0.11–3.78 ng/g dw) (Zhang et al. 2004) and the Han River, Korea (1.05–8.94 ng/g dw) (Kim et al. 2009). Overall, the data indicate that the contamination of DDTs in sediments of the Lijiang River was at a medium level compared to the other studied rivers. Compositional differences of HCH isomers and DDT metabolites in the environment could indicate different sources of contamination. Technical HCHs generally contain four isomers: a-HCH (60 %–70 %), b-HCH (5 %– 12 %), c-HCH (10 %–12 %) and d-HCH (6 %–10 %),
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while lindane comprises over 99 % of c-HCH. The physico-chemical properties of these HCH isomers are different. b-HCH has the lowest water solubility and vapor pressure, which is the most stable and relatively resistant to microbial degradation. Also it should be noted that c-HCH can be converted to a-HCH and subsequently to b-HCH in the environment (Javedankherad et al. 2013; Yang et al. 2005). In this study, the mean compositions of HCH isomers in sediment samples were a-HCH: 29.60 %, b-HCH: 38.82 %, c-HCH: 30.14 %, d-HCH: 1.44 % (Fig. 2a). Therefore, the dominance of b-HCH reflects the long-term migration and transformation of HCH in sediments from the Lijiang River. Technical DDTs and dicofol were the main contamination sources of DDTs in China (Sun et al. 2009). Technical DDTs contain p,p’-DDT (85 %), o,p’-DDT (\15 %) and some other trace impurities (\5 %). Dicofol contains about 3.54 %–10.78 % DDT as impurities, with o,p’-DDT as the major DDT compound (Sun et al. 2009). As shown in Fig. 2b, the mean compositions of DDT and its metabolites varied in the order of p,p’-DDD (61.39 %) [ p,p’-DDE (21.98 %) [ o,p’-DDT (13.09 %) [ p,p’-DDT (3.55 %). The result shows that p,p’-DDD was dominant at most of the sampling sites. Compared to the concentrations of DDT and its metabolites, ‘‘aged (degraded)’’ or ‘‘new (input recently)’’ of DDT can be inferred. The ratio of (DDE ? DDD)/ P DDT [ 0.5 could be indicative of a long period of weathering (degradation) of DDT (Yang et al. 2005). In this P study, the mean ratio of (DDE ? DDD)/ DDT in sediments from the Lijiang River was 0.83, which infers that DDTs input in investigation area was historical, and significant degradation has occurred. In order to evaluate the ecological risks of organic contaminants in this study, the concentrations of HCB, DDTs and HCHs were compared to two sediment quality guidelines (SQGs), i.e., the ERL (effects range-low value; below which adverse effects would be rarely observed) and the ERM (effects range-median value; above which adverse effects would frequently occur) guidelines (Long et al. 1995) as well as the NC (negligible concentration; below which the occurrence of adverse effects should be considered to be negligible) and the MPC (maximum permissible concentration; above which the risk of adverse effects should be considered to be unacceptable) guidelines (Crommentuijn et al. 2000) (Fig. 3). In the case of c-HCH, 75 % of sites did not exceed the ERL value (0.32 ng/g dw). However, c-HCH concentrations in sediments at S02 and S08 were higher than the ERM value (1 ng/g dw). The results indicate that the incidence of adverse effects of c-HCH at the two sites were higher than 75 % (Long et al. 1995). Although the total concentrations of DDTs did not exceed the ERM value at any site, they exceeded the ERL value (1.6 ng/g dw) at S02
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Fig. 2 Compositions of HCH isomers and DDT metabolites in surface sediments from the Lijiang River
sediments at two sites (i.e., S02, S08) may pose a serious threat to aquatic life, and urgent restoration and management is warranted to safeguard karst-aquifer systems. Acknowledgments The funding of this study was provided by NSFC (41273139, 41473118), the project of Guangxi Ba-gui Fellowship and Guilin Scientific & Technological Projects (20130116-2).
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Fig. 3 OCPs concentrations in surface sediments from the Lijiang River in comparison to two SQGs: a(ERL/ERM) and b(NC/MPC)
and S08. The concentration of p,p’-DDD was higher than the ERL value at S08, while the concentrations of both p,p’-DDE and p,p’-DDT were below the ERL values at any site. The results show that DDT contamination observed at S02 and S08 may cause adverse ecological effects. HCB data were compared to the (NC/MPC) SQG reported by Crommentuijn et al. (2000) because the (ERL/ERM) SQG did not include a guideline value for HCB in sediments. As shown in Fig. 3, the concentrations of HCB were below the NC value at any site, reflecting the occurrence of adverse effects of HCB in sediments of the Lijiang River should be considered to be negligible. These results suggest that HCHs and DDTs in sediments of the Lijiang River may cause adverse ecological risks, particularly at sites near agricultural areas. This highlights that Lijiang River
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Occurrence, Distribution and Sources of Organochlorine Pesticides (OCPs) in Surface Sediments from the Lijiang River, a Typical Karst River of Southwestern China Dan Zhang • Yinghui Wang • Kefu Yu Pingyang Li • Ruijie Zhang • Yiyin Xu
•
Received: 13 January 2014 / Accepted: 17 September 2014 / Published online: 27 September 2014 Ó Springer Science+Business Media New York 2014
Abstract The Lijiang River is a typical karst river of southwestern China. Karst-aquifer systems are more vulnerable to contamination compared to other types of aquifers. The occurrence and distribution of organochlorine pesticides (OCPs) in surface sediments from the Lijiang River were investigated to evaluate their potential ecological risks. The total concentrations of them in sediments ranged from 0.80 to 18.73 ng/g dry weight (dw) (mean 6.83 ng/g dw). The residue levels of OCPs varied in the order of HCB [ HCHs [ DDTs. Compositional analyses of OCPs showed that HCHs and DDTs were mainly from historical usage. The ecological risk assessment suggested that HCHs and DDTs in Lijiang River sediments may cause adverse ecological risks, particularly at sites near agricultural areas. Keywords Lijiang River Karst river OCPs Sediment contamination Ecological risk Organochlorine pesticides (OCPs) are of great concern around the world, due to their impact on non-target organisms, persistence in the environment, and bioaccumulation in the tissues of animals as well as humans via the
D. Zhang Y. Wang (&) K. Yu P. Li R. Zhang Coral Reef Research Center, Guangxi University, Nanning 530004, China e-mail: [email protected] D. Zhang Y. Wang P. Li R. Zhang School of Environment, Guangxi University, Nanning 530004, China Y. Xu Scientific Research Academy of Guangxi Environmental Protection, Nanning 530004, China
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food chain (Hu et al. 2011; Sojinu et al. 2012). Although the residue levels of OCPs in the environment have considerably declined in the past 30 years (Wang et al. 2012), their long half-lives (DT50-values) and potential adverse effects present a significant threat to the environment. Due to the low solubility in water and high organic carbon partition coefficient values (Koc), OCPs are easily adsorbed on suspended particulate matters and subsequently deposited in sediments. Once disturbed, sediments can be resuspended and the contaminants can reenter the aquatic environment and circulate in ecosystems, resulting in a secondary contamination (Veses et al. 2012; Wu et al. 2013). An investigation of the distribution of OCPs in surface sediments can be notably significant because sediments act both as a pollutant sink and as a secondary contamination source. Approximately one-third of China is karstic. The most extensive karst areas are in southwestern China, including Guangxi. Guilin City, which is located in the northeast of Guangxi, hosts the most typical karst landforms in southwestern China and has important high-quality karst water resources (Guo et al. 2010). Karst regions are characterized by unique surface and subsurface features and complex interactions with the atmosphere, hydrosphere and biosphere. Karstaquifer systems are more vulnerable to contamination compared to other types of aquifers (Guo et al. 2010). Moreover, contaminants introduced into karst aquifers often extended over large distances (Guo et al. 2010). Besides, numerous karst features facilitate the exchange of contaminants between surface and ground waters and the groundwater resources are sensitive to surface water contaminants (Bailly-Comte et al. 2008). The Lijiang River covers an area of 5,585 km2 and flows a distance of about 437 km from the north of Guilin City to the south. It is the main source of drinking water in Guilin City. With the intensive agriculture in Guilin City, large
Bull Environ Contam Toxicol (2014) 93:580–585
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Table 1 OCPs concentrations and basic statistical data in surface sediments from the Lijiang River (ng/g dw) OCPs
S01
S02
S03
S04
S05
S06
S07
S08
Range
Mean
SD
DL
DT50 (days)
HCB
0.61
1.44
0.35
2.88
4.83
1.22
0.35
3.49
0.35–4.83
1.90
1.55
0.05
6,051
Heptachlor
ndc
nd
0.38
0.01
nd
nd
nd
nd
nd–0.38
0.05
0.13
0.01
21,612
Heptachlor epoxide
0.01
nd
0.59
0.03
0.09
0.02
nd
nd
nd–0.59
0.09
0.19
0.01
23,614
Trans-chlordane
nd
0.68
0.90
0.52
1.47
nd
0.29
0.38
nd–1.47
0.53
0.46
0.01
34,543
Cis-chlordane
0.01
0.24
0.31
nd
nd
nd
nd
nd
nd–0.31
0.07
0.12
0.01
34,543
a-endosulfan
0.02
1.42
nd
nd
nd
0.01
0.01
nd
nd–1.42
0.18
0.47
0.01
18,159
b-endosulfan
nd
0.16
0.12
0.02
0.02
nd
nd
nd
nd–0.16
0.04
0.06
0.01
18,159
Aldrin
0.02
nd
1.02
0.01
0.03
nd
nd
3.96
nd–3.96
0.63
1.30
0.01
15,217
Dieldrin
0.03
3.19
1.25
0.06
0.12
0.02
0.06
0.43
0.02–3.19
0.65
1.04
0.02
16,625
Endrin
0.01
1.41
0.88
0.01
0.02
nd
nd
0.44
nd–1.41
0.35
0.50
0.01
16,625
p,p’-DDE p,p’-DDD
0.01 0.04
1.11 1.23
0.01 0.25
0.02 0.03
0.04 0.10
0.01 0.02
0.01 0.03
0.18 2.62
0.01–1.11 0.02–2.62
0.17 0.54
0.36 0.87
0.01 0.01
2,802 2,355
o,p’-DDT
nd
0.01
0.19
0.02
0.01
0.01
nd
0.30
nd–0.30
0.07
0.11
0.01
7,733
p,p’-DDT
nd
0.23
0.10
nd
nd
nd
nd
0.04
nd–0.23
0.05
0.08
0.02
6,767
a-HCH
0.01
0.65
0.98
0.02
0.03
0.05
0.06
0.45
0.01–0.98
0.28
0.35
0.01
3,149
b-HCH
0.02
0.44
0.23
0.04
0.06
0.07
0.09
1.02
0.02–1.02
0.25
0.32
0.01
2,519
c-HCH
0.01
6.14
0.08
0.01
0.01
0.06
0.06
1.13
0.01–6.14
0.94
2.00
0.01
3,149
0.06
0.12
0.03
2,099
1.52
2.45
0.83
1.19
6.83
6.22
d-HCH nd 0.38 0.09 nd nd nd nd nd nd–0.38 P HCHa 0.04 7.61 1.38 0.07 0.10 0.18 0.21 2.60 0.04–7.61 P b DDT 0.05 2.58 0.55 0.07 0.15 0.04 0.04 3.14 0.04–3.14 P OCP 0.80 18.73 7.73 3.68 6.83 1.49 0.96 14.44 0.80–18.73 a P b P HCH = a-HCH ? b-HCH ? c-HCH ? d-HCH; DDT = p,p’-DDE ? p,p’-DDD ? o,p’-DDT detection limit; DT50: half-life; DT50 values (sediment) for OCPs were reported by Shen et al. (2005)
amounts of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and hexachlorobenzene (HCB) were used to protect crops from insects and weeds from the 1950s to 1980s. Other OCPs such as heptachlors, chlordanes, endosulfans and aldrins have been also used in small amounts for agricultural and public health purpose in Guilin City from the 1950s to 1980s (Wang et al. 2011). However, the application of OCPs (beside HCB) has been banned in Guilin City since the 1980s due to their toxicity (Zhang et al. 2006). During recent years, HCB has been applied for controlling the spread of Oncomelania hupensis in Guilin City (Zhang et al. 2006), resulting that karst aquifers are threatened by HCB contamination. Hence it is essential to ascertain the concentrations of OCPs from the Lijiang River, especially in sediments which can integrate OCP exposure over time. The aims of this study were to survey the levels and distribution of OCPs in surface sediments from the Lijiang River, to assess their environmental risks in this region, and to understand their environmental behavior and fate in sediments.
Materials and Methods Sampling was conducted in March 2007 using a stainless steel grab sampler. A total of eight surface sediments
? p,p’-DDT;
c
nd: not detected; DL:
were collected from the Lijiang River. Due to the long half-lives of OCPs (Table 1) (Shen et al. 2005) and the banning of OCPs (beside HCB) in Guilin City in the 1980s (Zhang et al. 2006), the sampling design involving no repeated sampling may reflect the OCP contamination levels in the study area to some degree. Each sediment sample was actually a mixed sample of three sediments randomly collected from an area of around 20 m2 at the centre of the sampling site. These sediments were sampled covering many potential sources of OCP contamination, i.e., agricultural areas, urban areas and sewage treatment plants (Miglioranza et al. 2013; Shi et al. 2011). Details of the sampling sites are shown in Fig. 1. S02 (Mahuang Zhou) and S08 (Wayao) are located near intensive agricultural areas, as well as near the outflow of sewage treatment plants. S03 (Downstream Mahuang Zhou) is the location where Taohua River (a tributary of the Lijiang River) flows into the Lijiang River. Moreover, the main urban settlements are concentrated around S05 (Zi Zhou). The surface sediment samples (top 5 cm) were scooped into pre-cleaned glass jars, and then cooled with ice during transportation to the Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Guangzhou, China where they were stored at -20°C until further analysis.
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rose to 200°C at 4°C/min, then to 230°C at 2°C/min, and at last reached 280°C at a rate of 8°C/min, then held for 15 min. A 2 lL sample was injected into the GC-ECD for analysis. Quantification was based on internal calibration curves made from standard solutions at six concentration levels. The resulting correlation coefficients for the calibration curves of OCPs were all[0.999. A strict regime of quality control was employed before the onset of the sampling and analysis program. Method blanks (solvent) and spiked blanks (standards spiked into solvent) were analyzed. In addition, each sediment sample was analyzed in triplicate (n = 3). The relative standard deviation (RSD) ranged from 4 % to 10 %. The detection limits (DLs) of OCPs were based on a signal-to-noise ratio (S/N) of 3. The DLs of OCPs ranged from 0.01 to 0.05 ng/ g dw (Table 1). The recoveries of TCMX and PCB209 were 69 ± 6 % and 76 ± 7 %, respectively. The data were subjected to statistical analysis. Arithmetic mean and standard deviation values were determined using the SPSS 16.0 statistical software package. Fig. 1 Map of the sampling sites in the investigation area. S01: Yushan Bridge, S02: Mahuang Zhou, S03: Downstream Mahuang Zhou, S04: Jiefang Bridge, S05: Zi Zhou, S06: Lijiang River Bridge, S07: Jingpingshan Bridge, S08: Wayao
Results and Discussion
The procedures for OCPs’ extraction, fractionation and instrumental analysis were described in detail elsewhere (Gong et al. 2007). In brief, sediment samples were homogenized and freeze-dried with vacuum freeze drier before extraction. 10 g of dried sediments were 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 for 24 h. Activated copper granules were added to the collection flask to remove elemental sulfur. The extract was added with anhydrous sodium sulfate and then concentrated by rotary evaporator and solvent exchanged to hexane and further reduced to 2–3 mL. A 1: 2 alumina/silica gel column (both 3 % deactivated with H2O) was used to clean up and fractionate the extract, and OCPs were eluted with 30 mL of hexane/dichloromethane (3:2). The effluents were reduced finally to a volume of 0.2 mL under a gentle gas stream of purified nitrogen. A know quantity of pentachloronitrobenzene (PCNB) was added as an internal standard prior to gas chromatography–electron capture detector (GC–ECD) analysis. OCPs were measured using a HP-6890 gas chromatograph equipped with a 63Ni electron capture detector (GC– ECD) and a HP-5 silica fused capillary column (30 m 9 0.32 mm i.d. 9 0.25 lm film thickness). High purity N2 was used as the carrier gas at a flow rate of 2.5 mL/ min under the constant flow mode. Injector and detector temperatures were maintained at 290 and 300°C, respectively. The oven temperature began at 100°C for 1 min and
The statistical data of OCPs concentrations in sediment samples from the Lijiang River are summarized in Table 1. Due to DT50 values (sediment) for OCPs ranging from 2,099 (d-HCH) to 34,543 days (chlordanes), OCPs concentrations in sediments of the Lijiang River declined to different degrees (Shen et al. 2005). The total concentrations of OCPs were 0.80–18.73 ng/g dw (mean 6.83 ng/g dw). The results show that the concentrations of OCPs varied in different sampling regions. The highest concentration of OCPs was observed at S02 (18.73 ng/g dw), followed by S08 (14.44 ng/g dw). The presence of OCPs (beside HCB) in sediments from the Lijiang River was associated with historical input (Wang et al. 2011). The levels of OCPs in sediments in the present study were compared to those measured in sediments from the Han River, Korea (Kim et al. 2009), the Mekong River, Vietnam (Minh et al. 2007), the Haihe River, China (Yang et al. 2005) and the Tonghui River, China (Zhang et al. 2004). The results show that the contamination of OCPs in sediments of the Lijiang River was at a medium level compared to the other studied rivers. OCPs residue levels varied in the order of HCB [ HCHs [ DDTs. In this study, the concentrations of HCB ranged from 0.35 to 4.83 ng/g dw (mean 1.90 ng/g dw). HCB has never been used directly as a pesticide in China, but it has been used as an intermediate in the synthesis of pentachlorophenol (PCP) and pentachlorophenolNa (PCP-Na). PCP and Na-PCP have been used for more than 30 years in China as either a rice field herbicide or a
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pesticide to control the spread of O. hupensis in many lakes in the southern China (Wen et al. 2008). In order to control the spread of O. hupensis, technical Na-PCP has been sprayed in the Lijiang River (Zhang et al. 2006). There is no chemical plant producing HCB near the sampling locations S01–S08, so the use of Na-PCP near the Lijiang River may contribute to the HCB input. In addition, HCB has relatively high vapor pressure, so long-range transport from chemical plants producing HCB is probably another source in the study area. HCHs and DDTs have been banned from using as pesticides for agricultural purpose in Guilin City since the 1980s (Wang et al. 2011). In this study, the total concentrations of HCHs (a-HCH, b-HCH, c-HCH and d-HCH) ranged from 0.04 to 7.61 ng/g dw (mean 1.52 ng/g dw). The highest concentration of HCHs was observed at S02 (near agricultural areas), showing that large amounts of HCHs have been applied there in the past. A comparison to other studies show that the concentrations of HCHs in sediments of the Lijiang River were lower than those measured in sediments from the Haihe River, China (1.88–18.8 ng/g dw) (Yang et al. 2005), but higher than those of the Tonghui River, China (0.06–0.38 ng/g dw) (Zhang et al. 2004) and the Mekong River, Vietnam (\0.02–1.30 ng/g dw) (Minh et al. 2007). Overall, the data indicate that the contamination of HCHs in sediments of the Lijiang River was at a medium level compared to the other studied rivers. The total concentrations of DDTs (p,p’-DDT, o,p’-DDT, p,p’-DDD and p,p’-DDE) in different sites were in the range of 0.04–3.14 ng/g dw (mean 0.83 ng/g dw). Among DDT and its metabolites, p,p’-DDD (mean 0.54 ng/g dw) was the dominant compound, followed by p,p’-DDE (0.17 ng/g dw) and o,p’-DDT (0.07 ng/g dw). The highest concentration of DDTs was observed at S08 (near agricultural areas) with a concentration up to 3.14 ng/g dw, showing that a relatively larger proportion of DDTs was used at agricultural areas compared to other sites. Compared to other studies, DDTs concentrations in sediments from the Lijiang River were lower than those measured in sediments from the Mekong River, Vietnam (\0.01–110 ng/g dw) (Minh et al. 2007) and the Haihe River, China (0.320–80.2 ng/g dw) (Yang et al. 2005), but comparable to those in sediments of the Tonghui River, China (0.11–3.78 ng/g dw) (Zhang et al. 2004) and the Han River, Korea (1.05–8.94 ng/g dw) (Kim et al. 2009). Overall, the data indicate that the contamination of DDTs in sediments of the Lijiang River was at a medium level compared to the other studied rivers. Compositional differences of HCH isomers and DDT metabolites in the environment could indicate different sources of contamination. Technical HCHs generally contain four isomers: a-HCH (60 %–70 %), b-HCH (5 %– 12 %), c-HCH (10 %–12 %) and d-HCH (6 %–10 %),
583
while lindane comprises over 99 % of c-HCH. The physico-chemical properties of these HCH isomers are different. b-HCH has the lowest water solubility and vapor pressure, which is the most stable and relatively resistant to microbial degradation. Also it should be noted that c-HCH can be converted to a-HCH and subsequently to b-HCH in the environment (Javedankherad et al. 2013; Yang et al. 2005). In this study, the mean compositions of HCH isomers in sediment samples were a-HCH: 29.60 %, b-HCH: 38.82 %, c-HCH: 30.14 %, d-HCH: 1.44 % (Fig. 2a). Therefore, the dominance of b-HCH reflects the long-term migration and transformation of HCH in sediments from the Lijiang River. Technical DDTs and dicofol were the main contamination sources of DDTs in China (Sun et al. 2009). Technical DDTs contain p,p’-DDT (85 %), o,p’-DDT (\15 %) and some other trace impurities (\5 %). Dicofol contains about 3.54 %–10.78 % DDT as impurities, with o,p’-DDT as the major DDT compound (Sun et al. 2009). As shown in Fig. 2b, the mean compositions of DDT and its metabolites varied in the order of p,p’-DDD (61.39 %) [ p,p’-DDE (21.98 %) [ o,p’-DDT (13.09 %) [ p,p’-DDT (3.55 %). The result shows that p,p’-DDD was dominant at most of the sampling sites. Compared to the concentrations of DDT and its metabolites, ‘‘aged (degraded)’’ or ‘‘new (input recently)’’ of DDT can be inferred. The ratio of (DDE ? DDD)/ P DDT [ 0.5 could be indicative of a long period of weathering (degradation) of DDT (Yang et al. 2005). In this P study, the mean ratio of (DDE ? DDD)/ DDT in sediments from the Lijiang River was 0.83, which infers that DDTs input in investigation area was historical, and significant degradation has occurred. In order to evaluate the ecological risks of organic contaminants in this study, the concentrations of HCB, DDTs and HCHs were compared to two sediment quality guidelines (SQGs), i.e., the ERL (effects range-low value; below which adverse effects would be rarely observed) and the ERM (effects range-median value; above which adverse effects would frequently occur) guidelines (Long et al. 1995) as well as the NC (negligible concentration; below which the occurrence of adverse effects should be considered to be negligible) and the MPC (maximum permissible concentration; above which the risk of adverse effects should be considered to be unacceptable) guidelines (Crommentuijn et al. 2000) (Fig. 3). In the case of c-HCH, 75 % of sites did not exceed the ERL value (0.32 ng/g dw). However, c-HCH concentrations in sediments at S02 and S08 were higher than the ERM value (1 ng/g dw). The results indicate that the incidence of adverse effects of c-HCH at the two sites were higher than 75 % (Long et al. 1995). Although the total concentrations of DDTs did not exceed the ERM value at any site, they exceeded the ERL value (1.6 ng/g dw) at S02
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Fig. 2 Compositions of HCH isomers and DDT metabolites in surface sediments from the Lijiang River
sediments at two sites (i.e., S02, S08) may pose a serious threat to aquatic life, and urgent restoration and management is warranted to safeguard karst-aquifer systems. Acknowledgments The funding of this study was provided by NSFC (41273139, 41473118), the project of Guangxi Ba-gui Fellowship and Guilin Scientific & Technological Projects (20130116-2).
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Fig. 3 OCPs concentrations in surface sediments from the Lijiang River in comparison to two SQGs: a(ERL/ERM) and b(NC/MPC)
and S08. The concentration of p,p’-DDD was higher than the ERL value at S08, while the concentrations of both p,p’-DDE and p,p’-DDT were below the ERL values at any site. The results show that DDT contamination observed at S02 and S08 may cause adverse ecological effects. HCB data were compared to the (NC/MPC) SQG reported by Crommentuijn et al. (2000) because the (ERL/ERM) SQG did not include a guideline value for HCB in sediments. As shown in Fig. 3, the concentrations of HCB were below the NC value at any site, reflecting the occurrence of adverse effects of HCB in sediments of the Lijiang River should be considered to be negligible. These results suggest that HCHs and DDTs in sediments of the Lijiang River may cause adverse ecological risks, particularly at sites near agricultural areas. This highlights that Lijiang River
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