Distribution and characterization of organochlorine pesticides and polycyclic aromatic hydrocarbons in surface sediment from Poyang Lake, China

Science of the Total Environment 433 (2012) 491–497

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Distribution and characterization of organochlorine pesticides and polycyclic aromatic hydrocarbons in surface sediment from Poyang Lake, China Mang Lu ⁎, De-Cai Zeng, Yong Liao, Bin Tong School of Materials Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen 333403, Jiangxi Province, China

H I G H L I G H T S ► A first report of POP distribution in sediments of Poyang Lake, the largest freshwater lake in China. ► Potential sources of DDTs and Na-PCP were analyzed. ► PAH metabolites not reported were identified.

a r t i c l e

i n f o

Article history: Received 3 February 2012 Received in revised form 18 June 2012 Accepted 22 June 2012 Available online 21 July 2012 Keywords: Persistent organic pollutants HCHs DDTs PAHs Metabolites

a b s t r a c t The concentrations of organochlorine pesticides (OCPs) and 16 priority polycyclic aromatic hydrocarbons (PAHs) were investigated in the sediments from Poyang Lake, the largest freshwater lake in China. The results showed that the total concentrations of four hexachlorocyclohexane (HCH) isomers (α-HCH, β-HCH, γ-HCH, δ-HCH), three dichlorodiphenyltrichloroethane (DDT) homologs and their metabolites (p,p′-DDD, o,p′-DDD, p,p′-DDE, p,p′-DDT, o,p′-DDT, o,p′-DDE), sodium pentachlorophenate and PAHs varied from 0.536 ± 0.330 to 6.937 ± 2.655, 14.421 ± 5.260 to 82.871 ± 31.258, 15.346 ± 6.935 to 48.254 ± 16.836, and 33.0 ± 11.5 to 369.1± 138.5 μg/kg, respectively. The concentrations of HCH isomers followed the order: γ-HCH> β-HCH > δ-HCH >α-HCH. The most dominant γ-HCH ranged from 0.253± 0.155 to 3.465± 1.010 μg/kg, suggesting a recent input of lindane. p,p′-DDD was the most dominant pollutant of DDTs, with a mean concentration of 31.684± 13.530 μg/kg. The ratios of (DDE+DDD)/DDT ranged from 75± 24 to 360± 115, indicating no recent input of DDTs. The PAHs were mainly originated from liquid fossil fuel combustion and leakage, except at Pojiang River estuary, where the pyrogenic source (coal, grass and wood combustion) was dominant. Several PAH metabolites were identified and the possible degradation pathways were proposed. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Poyang Lake, covering a surface water area of 3050 km 2, is located in the southern part of the PR China. It is the largest freshwater in China and the drainage area of the lake accounts for approximately 97% of Jiangxi Province (Shankman and Liang, 2003). The lake is one of the most important ecological regions recognized by the Global Natural Fund, and one of the six wetlands having the most abundant biodiversity. Over the past decades, because of rapid economic development, the water quality of Poyang Lake is reported to have been degraded markedly (Li et al., 2010). Application of fertilizers, pesticides and herbicides, metal mining and smelting, petrochemical production carry a variety of pollutants into the lake. It has been reported that Poyang Lake region was contaminated strongly by heavy metals such as Cd, Hg, Pb, As and

⁎ Corresponding author. E-mail address: [email protected] (M. Lu). 0048-9697/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.scitotenv.2012.06.108

Cr (Song et al., 2010; Yuan et al., 2011). However, fewer studies have been conducted on the distribution and characterization of persistent organic pollutants (POPs) in Poyang Lake. Sedimentation has been identified as an important fate of pollutants in freshwater ecosystems. Sediments act both as a pollutant sink and as a carrier and secondary source of pollutants. These pollutants are not necessarily fixed permanently to sediments, but may be recycled via chemical and biological processes. POPs such as organochlorinated pesticides (OCPs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), have been detected in sediments from different regions in China (Zhang et al., 2003; Yang et al., 2005; Gao et al., 2008; Zhao et al., 2009). Many of these POPs and their congeners bioaccumulate and are considered potent toxicants capable of producing a wide spectrum of adverse health effects in biota and humans (UNEP/UNDP, 2001). The aims of this study were (a) to determine the levels of OCPs, PAHs, and their metabolites in the sediments collected from Poyang Lake, and (b) to evaluate the potential sources of OCPs and PAHs.

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2. Materials and methods

2.3. Extraction–fractionation

2.1. Chemicals and reagents

The organic matters were extracted using a Soxhlet apparatus as follows: the samples were spiked with surrogated standards, then mixed with anhydrous sodium sulfate and allowed to equilibrate for 24 h. The samples were extracted using dichloromethane (DCM) for 16 h. The extract was divided into three fractions for the analyses of OCPs and their derivations, PAHs, and PAH metabolites, respectively. The extract for OCP analysis was concentrated to 10 mL under reduced pressure using a rotary evaporator. Additional 10 mL n-hexane was added to the pear-shaped flask and evaporated again to nearly dryness. This concentrated extract was loaded onto the silica chromatography column filled with deactivated silica. The column was eluted with n-hexane followed by 7:3 hexane:DCM (v/v) to fractionate OCPs from other interfering organics (Wu et al., 2005). The two eluants were combined and concentrated to 1 mL. The extract for PAH analysis was concentrated to 1 mL using the method mentioned above, but the cleanup was performed using the chromatography column packed with activated silica. The column was sequentially eluted with n-hexane and mixture of 3:2 hexane: DCM (v/v). The former fraction was discarded, and the latter fraction containing PAHs was concentrated to 1 mL and rinsed with n-hexane. The final volume was adjusted to 1 mL under N2 and stored in a sample vial capped with a Teflon-lined septum.

All solvents were analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China), and redistilled by glass apparatus before use. The mixed standard sample of OCPs and the internal standards (2,4,5,6-tetrachloro-m-xylene, TCMX; decachlorobiphenyl, DCB) were purchased from Ultra Scientific, Inc. (North Kingstown, Rhode Island, USA). The PAH standard sample and perdeuterated PAH surrogates (naphthalene-d8, biphenyl-d10, phenanthrene-d10, and chrysene-d12) were purchased from Sigma (St. Louis, MO, USA). The silica gel (80–100 mesh) was extracted for 48 h in a Soxhlet apparatus, activated in the oven at 150 °C for 12 h, then deactivated with distilled water at a ratio of 3 wt.% and stored in a desiccator. The glass ware were cleaned with detergent, K2Cr2O7–H2SO4 solution, tap water and deionized water, respectively and finally baked at 180 °C for 4 h before use.

2.2. Sampling The sediment samples of Poyang Lake were collected in May 2011 from 16 sampling locations (Fig. 1). The top 5-cm layer of sediments was scooped using a pre-cleaned stainless steel scoop into solventrinsed aluminum containers. Five sub-samples were collected for each sample type at each location. The sub-samples were then mixed thoroughly into a composite sample to reduce the possible random variation. The samples were wrapped in acetone-cleaned aluminum foil, stored in ice-coolers, and transported to the laboratory where they were kept at −20 °C before extraction.

Yangtze River

R1 R2

R3 R4 R5 R8

R7 R9

The OCPs and PAHs were analyzed using an Agilent 7890–5975c gas chromatography–mass spectrometer (GC–MS) equipped with an Agilent HP-5MS fused silica capillary column (60 m × 0.25 mm × 0.25 μm). The injection volume was 1 μL. Helium was used as the carrier gas at a flow rate of 1 mL/min. The column temperature was set to 50 °C for the first 1 min, increased 20 °C/min to a temperature of 120 °C, then increased 4 °C/min to 310 °C, and maintained at 310 °C for 30 min. Mass spectrometer conditions were: electron impact, electron energy 70 eV; filament current 100 μA; multiplier voltage, 1200 V; full scan. The extract for metabolite analysis was analyzed without fractionation using a Bruker 9.4T apex-ultra Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with an Apollo II electrospray source. Electrospray ionization (ESI) was used in negative ion mode to characterize the acidic oxygen-containing compounds. The operating conditions for negative ion formation were 4.0 kV emitter voltage, 4.5 kV capillary column front end voltage, and −320 capillary column end voltage. Additional information about the ESI FT-ICR MS technique used in this study is reported elsewhere (Shi et al., 2010). 2.5. Quality control

R6

Xiuhe River

2.4. Instrumental analysis

R10

R11

Ganjiang River

R12 R13 R14 R15 R16

Pojiang River

The recovery was 72±6% for HCHs, 89±12% for HCB, 95±24% for DDTs, 63±17% for cyclodienes, 77±16% for sodium pentachlorophenate (Na-PCP), and 86±15% for PAHs. The samples were extracted with a blank consisted of a Soxhlet thimble containing anhydrous sodium sulfate. The method detection limit was calculated as three times of the mean blank value (n = 5). All results were expressed on a dry weight basis. 3. Results and discussion

Xinjiang River 3.1. OCPs in sediments

Fuhe River Fig. 1. Locations of sampling sites at Poyang Lake, China.

A total of seventeen OCP compounds were measured including hexachlorobenzene (HCB), four hexachlorocyclohexane (HCH) isomers (α-HCH, β-HCH, γ-HCH, δ-HCH), three dichlorodiphenyltrichloroethane (DDT) homologs and their metabolites (p,p′-DDT, o,p′-DDT, p,p′-DDE, o, p′-DDE, p,p′-DDD, o,p′-DDD), four cyclodienes (aldrin, dieldrin, endrin,

M. Lu et al. / Science of the Total Environment 433 (2012) 491–497

heptachlor) and heptachlor metabolite (heptachlor epoxide), and sodium pentachlorophenol (PCP-Na). Measured concentrations of OCPs in the sediments of Poyang Lake are listed in Table 1. 3.1.1. HCB and PCP-Na As shown in Table 1, aldrin and endrin were not detected in all the sediment samples. HCB and PCP-Na were detected at relatively high levels in all the samples. In the major water systems in China, significant amounts of HCB can be detected in sediments (Wang et al., 2010). HCB has never been registered and used as a pesticide in China, but has been used to produce PCP, reagents, and fireworks (Wei et al., 2007). In order to control the spread of snailborne schistosomiasis, technical Na-PCP had been widely sprayed in lakes in south-central China, where schistosomiasis prevailed, since 1960s to up to the middle of 1990s. It is well known that PCP and its derivative Na-PCP contain PCDD/Fs as impurities and are one of the main historic PCDD/Fs sources with contemporary relevance (Weber et al., 2008). PCDD/Fs, a family of compounds including some extremely toxic congeners, are among the 12 POPs of Stockholm Convention. In this study, PCDD/Fs were not analyzed. However, a significant amount of PCDD/Fs has been detected in Dongting Lake, the second largest freshwater in China, where schistosomiasis prevailed like Poyang Lake (Gao et al., 2008). Hence the distribution and level of PCDD/Fs in Poyang Lake deserve our sustainable concerns and special attention. 3.1.2. HCHs The total HCH concentrations were 0.536±0.330–6.937±2.655 μg/kg in the sediments from Poyang Lake (Table 1). Compared with data acquired by studies conducted in other regions in China, ∑ HCH concentrations in the sediments of Poyang Lake was higher than those of Gaobeidian Lake (1.02–1.48 μg/kg) (Li et al., 2008) and Taihu Lake (0.07–5.75 μg/kg) (Zhao et al., 2009), but lower than those of Guanting Reservoir (0.3–10.8 μg/kg) (Xue et al., 2006) and Baiyangdian Lake (9.8–12.8 μg/kg) (Hu et al., 2010). As far as HCH isomers are concerned, the concentration followed the order: γ-HCH> β-HCH > δ-HCH >α-HCH. The most dominant γ-HCH ranged from 0.253 ± 0.155 to 3.465 ±1.010 μg/kg, with a mean value of 1.472 ± 0.335 μg/kg. Composition differences of HCH isomers in the environment can indicate different contamination sources. Typical technical HCHs contain 55–80% α-HCH, 5–14% β-HCH, 8–15% γ-HCH and 2–16% δ-HCH (Lee et al., 2001). It is reported that α-HCH (Zheng et al., 2011), β-HCH (Wu et al., 1999), or δ-HCH (Zhao et al., 2009) may be dominant in sediments from the river or estuary environments after longterm migration and transformation. In this study, the high proportions of γ-HCH in the sediments of Poyang Lake might suggest a possibility of recent input of lindane pesticides (contains over 99% γ-HCH) from agricultural activities into the environments of Poyang Lake region, a major area of crop production in China. In most cases, the degradation of α-HCH and γ-HCH is rapid, but β-HCH and δ-HCH isomers are either not degraded (Sahu et al., 1993) or degraded very slowly (Kumar et al., 2005). Although, the application of HCHs in agriculture has been banned in China since 1983, use of lindane may have been continued for several years in pest control practices (Fu et al., 2003). 3.1.3. DDTs As shown in Table 1, ∑DDT concentrations varied from 14.421 ± 5.260 to 82.871 ± 31.258 μg/kg, with an average value of 46.693 ± 18.520 μg/kg. The highest DDT level (82.871 ± 31.258 μg/kg) occurred at site R8. p,p′-DDD and o,p′-DDD were the principal contaminants of DDTs, with a mean concentration of 31.684 ± 13.530 and 14.179 ± 6.330 μg/kg, respectively. The percentage of individual compounds followed the sequence: p,p′-DDD >o,p′-DDD >p,p′-DDE> p,p′-DDT > o,p′-DDT> o,p′-DDE. Technical DDTs and dicofol were the main contamination sources of DDTs in China. Technical DDTs is typically composed of 77.1% p,p′-

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DDT, 14.9% o,p′-DDT, 4% p,p′-DDE and some other trace impurities, while dicofol contains about 3–7% DDTs as impurities (Zhu et al., 2005). The ratios of the parent DDTs to its metabolites provide useful information on the identification of pollution source. In general, the ratios of (p,p′-DDE + p,p′-DDD)/p,p′-DDT is a useful indicator for new inputs of the technical DDTs (Qiu et al., 2004). The low ratio of (DDE + DDD)/DDT (b1.0) is indicative of fresh DDT application and a ratio much higher than 1.0 is generally expected for old sources in the environment (Jaga and Dharmani, 2003). In this study, the ratios of (DDE + DDD)/DDT in the Poyang Lake sediments ranged from 75 ± 24 to 360 ± 115 (Fig. 2b), indicating that most of the sampling sites have no recent input of DDTs. DDT can be biodegraded to DDE under aerobic conditions and to DDD under anaerobic conditions (Hites and Day, 1992). As Poyang Lake region is located in the subtropical zone, the anaerobic environment dominates the agricultural soils. Hence, the high proportions of DDD in the sediments of Poyang Lake might arise from anaerobic biodegradation of DDT. Wang et al. (2008) also found that DDD dominated the sediments in Daya Bay (South China), a typical subtropical zone. Moreover, the ratio of o,p′-DDT/p,p′-DDT can also be used to distinguish whether the DDT pollution caused by technical DDT or by dicofol. Generally, 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 (Qiu et al., 2005). In fact, the use of DDT has been banned in China since 1983. In this study, the ratio of o,p′-DDT/p,p′-DDT were lower than 1.0 (Fig. 2a), suggesting the application of technical DDTs in these areas for a long time. 3.1.4. Cyclodienes As shown in Table 1, other OCPs like aldrin, dieldrin and endrin, were all at lower levels. These chemicals have never been produced and used for agriculture in China; however they were detected in PM2.5 and PM10 in Beijing, surface water and sediments from Guanting Reservoir of Beijing, and most water samples from Qiantang River (Jiang et al., 2009). These compounds might come from industrial application and/or transportation by air parcels from abroad by global distillation effect, as the three OCPs are still being used in some developing countries around the tropical belt. Heptachlors (including heptachlor and its metabolite, heptachlor epoxide) were detected in the sediments, with mean concentrations of 3.310 ± 1.735 and 0.023 ± 0.018 μg/kg, respectively. Heptachlor was detected in all samples except for sites R5, 6, 10, and 13, with the highest concentration detected at site R3 while the concentrations of heptachlor epoxide ranged from ND (not detected) to 0.011 ± 0.010 μg/kg. 3.1.5. Vertical distribution of OCPs In order to investigate the year distribution of OCPs, sediment samples from various depth levels at sites (R3, 6, 8, and 10) with relatively high OCP levels were collected and analyzed. The concentration values of individual compound at the same depth were averaged, and converted to the corresponding values for years according to the mean sedimentation rate in Poyang Lake (0.48 cm/year). As shown in Fig. 3a, the peak concentration of γ-HCH occurred in 1960, 1975, 1985 and 1995. HCHs have been produced in China since 1952, and the large scale usage of HCHs caused several peak concentrations of γ-HCH. The maximum concentration of δ-HCH (6.853 ± 2.930 μg/kg) was observed in 1985. After 1985, the concentration of δ-HCH has been decreased obviously, which might arise from the restricted application of HCHs in agriculture in China since 1983 (Fu et al., 2003). Fig. 3b describes the distribution of concentrations of p,p′-DDD and PCP-Na with the time in Poyang Lake. The peak concentration of p,p′-DDD occurred in 1955 and 1990, and PCP-Na in 1965 and 2000. Before 1970s, PCP-Na was widely sprayed by plane in Poyang

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M. Lu et al. / Science of the Total Environment 433 (2012) 491–497

Table 1 Levels of OCPs in the sediments of Poyang Lake (μg/kg, mean value ± standard deviation, n = 5). Compound

Sampling site

HCB α-HCH β-HCH γ-HCH δ-HCH p,p′-DDT o,p′-DDT p,p′-DDE o,p′-DDE p,p′-DDD o,p′-DDD Aldrin Dieldrin Endrin Heptachlor Heptachlor epoxide PCP-Na

R1

R2

R3

R4

R5

R6

R7

2.215 ± 1.230 0.325 ± 0.150 1.325 ± 0.730 0.652 ± 0.422 0.585 ± 0.324 0.215 ± 0.153 0.046 ± 0.052 0.538 ± 0.350 0.246 ± 0.152 15.735 ± 5.284 6.753 ± 4.139 ND 0.136 ± 0.065 ND 2.534 ± 1.630 0.015 ± 0.010 35.635 ± 22.537

1.735 ± 0.752 0.147 ± 0.110 0.455 ± 0.230 0.547 ± 0.346 0.465 ± 0.185 0.114 ± 0.105 0.043 ± 0.060 0.274 ± 0.150 ND 9.452 ± 4.265 4.438 ± 1.385 ND 0.051 ± 0.040 ND 1.355 ± 0.438 0.011 ± 0.010 27.346 ± 10.235

0.395 ± 0.163 ND ND 0.253 ± 0.155 0.283 ± 0.105 0.363 ± 0.135 0.105 ± 0.070 0.587 ± 0.314 ND 35.763 ± 22.335 15.856 ± 7.835 ND ND ND 15.243 ± 5.732 0.143 ± 0.085 29.452 ± 14.530

0.824 ± 0.520 0.426 ± 0.090 1.024 ± 0.350 0.586 ± 1.235 ND 0.531 ± 0.141 0.155 ± 0.040 0.635 ± 0.126 0.135 ± 0.310 25.846 ± 16.824 10.473 ± 3.150 ND ND ND 3.275 ± 0.730 0.021 ± 0.015 45.625 ± 15.382

1.328 ± 0.637 0.255 ± 0.070 2.153 ± 0.605 ND 0.372 ± 0.105 0.214 ± 0.061 0.052 ± 0.040 ND ND 28.564 ± 7.283 12.583 ± 3.620 ND 0.145 ± 0.081 ND ND ND 16.475 ± 5.160

1.352 ± 0.725 0.575 ± 0.163 1.422 ± 0.370 3.465 ± 1.010 1.475 ± 0.395 0.135 ± 0.041 0.025 ± 0.012 ND ND 48.593 ± 19.384 23.296 ± 7.520 ND 0.058 ± 0.025 ND ND ND 32.535 ± 10.140

0.315 ± 0.184 0.326 ± 0.240 ND 2.357 ± 1.230 1.327 ± 0.426 0.533 ± 0.310 0.175 ± 0.584 1.485 ± 0.625 0.249 ± 0.080 34.585 ± 12.525 15.735 ± 4.920 ND ND ND 2.482 ± 0.902 0.025 ± 0.020 23.624 ± 8.530

ND: not detected.

Lake in order to skill schistosomiasis host oncomelania. PCP-Na was used again in Poyang Lake at the end of 1990s due to the revival of schistosomiasis endemic.

abundant. Other compounds such as NAP, FLUO and BbF were posteriorly abundant, which was similar with the case of the Three Gorges Reservoir reported by Wang et al. (2009). The highest level of ∑PAH concentrations was found at site R13 (Table 3), Pojiang River estuary,

3.2. PAHs in sediments

(a) 10 HCB α-HCH β-HCH

8

Concentration (μg/kg)

A summary description of detection frequency, range, mean and median concentration for 16 priority PAHs is presented in Table 2. The 16 priority PAHs measured were: naphthalene (NAP), acenaphthylene (AC), acenaphthene (ACE), fluorene (FLU), phenanthrene (PHE), anthracene (ANT), fluoranthene (FLUO), pyrene (PYR), benz[a]anthracene (BaA), chrysene (CHR), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (INP), dibenz [a,h]anthracene (DBA) and benzo[ghi]perylene (BghiP). Total concentrations of 16 PAHs in this study ranged from 33.0 ± 11.5 to 369.1 ± 138.5 μg/kg with a mean value of 157.0 ± 63.2 μg/kg (Table 3). In terms of individual PAH composition, PHE was the most

γ-HCH δ-HCH

6

4

2

(a) o,p'-DDT/ p,p'-DDT

0.6

0

0.5

1950

1960

1970

0.4

1980

1990

2000

2010

Time (year)

0.3

(b)

0.2

100

p,p'-DDD PCP-Na

0.1 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16

Sampling site

(p,p'-DDE + p,p'-DDD)/p,p'-DDT

(b) 600 500 400

Concentration (μg/kg)

0.0

80

60

40

300

20

200 100

0

0 R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16

Sampling site Fig. 2. The ratios of o,p′-DDT/p,p′-DDT (a), and (p,p′-DDE + p,p′-DDD)/p,p′-DDT (b) in the sediments from Poyang Lake.

1950

1960

1970

1980

1990

2000

2010

Time (year) Fig. 3. (a) Variations of HCB and HCHs with the time in Poyang Lake; (b) variations of p,p′-DDD and PCP-Na with the time in Poyang Lake.

M. Lu et al. / Science of the Total Environment 433 (2012) 491–497

495

R8

R9

R10

R11

R12

R13

R14

R15

R16

0.355 ± 0.216 0.463 ± 0.450 ND 2.252 ± 0.502 0.436 ± 0.150 0.436 ± 0.195 0.135 ± 0.070 0.745 ± 0.251 0.315 ± 0.130 55.485 ± 24.636 25.755 ± 7.260 ND ND ND 1.536 ± 0.425 0.016 ± 0.010 48.254 ± 16.360

1.254 ± 0.725 0.258 ± 0.090 0.515 ± 0.182 1.374 ± 0.410 0.472 ± 0.120 0.263 ± 0.725 0.072 ± 0.070 0.357 ± 0.180 ND 35.643 ± 13.637 16.465 ± 5.632 ND ND ND 8.545 ± 3.536 0.024 ± 0.020 21.575 ± 7.932

2.315 ± 1.224 0.632 ± 0.411 0.735 ± 0.450 ND 0.683 ± 0.365 0.158 ± 0.110 0.045 ± 0.040 0.255 ± 0.140 ND 51.536 ± 21.530 22.315 ± 8.390 ND 0.125 ± 0.110 ND ND ND 36.734 ± 13.595

1.335 ± 0.0.537 0.535 ± 0.305 0.487 ± 0.216 0.573 ± 0.385 0.553 ± 0.405 0.352 ± 0.210 0.012 ± 0.015 0.315 ± 0.105 ND 23.575 ± 8.380 9.546 ± 3.550 ND ND ND 2.215 ± 0.825 0.017 ± 0.020 15.346 ± 5.305

2.146 ± 0.1.362 0.385 ± 0.121 ND 2.456 ± 0.710 ND 0.217 ± 0.061 0.076 ± 0.060 ND ND 18.453 ± 8.492 5.645 ± 2.505 ND 0.143 ± 0.051 ND 5.484 ± 2.370 0.032 ± 0.040 26.873 ± 8.467

0.535 ± 0.367 0.353 ± 0.150 0.843 ± 0.362 1.483 ± 0.610 0.537 ± 0.425 0.153 ± 0.113 0.035 ± 0.042 0.648 ± 0.496 0.153 ± 0.172 25.356 ± 11.436 12.415 ± 4.850 ND 0.035 ± 0.038 ND ND ND 38.425 ± 11.530

1.315 ± 0.552 0.637 ± 0.438 0.536 ± 0.330 3.455 ± 1.530 0.493 ± 0.310 0.212 ± 0.205 0.058 ± 0.050 0.525 ± 0.161 ND 34.254 ± 12.350 15.645 ± 5.365 ND 0.065 ± 0.071 ND 5.411 ± 1.350 0.025 ± 0.020 21.435 ± 8.940

1.523 ± 0.851 ND 0.755 ± 0.450 2.562 ± 1.205 ND 0.133 ± 0.104 0.036 ± 0.028 ND ND 28.453 ± 12.537 13.535 ± 5.210 ND 0.027 ± 0.030 ND 3.524 ± 1.840 0.021 ± 0.026 25.625 ± 9.382

2.215 ± 1.513 ND ND 1.529 ± 0.724 0.475 ± 0.350 0.155 ± 0.120 0.024 ± 0.039 0.545 ± 0.480 ND 35.648 ± 11.635 16.413 ± 6.025 ND ND ND 1.355 ± 0.830 0.018 ± 0.023 18.462 ± 6.020

about 150 km upstream of which the Jingdezhen Coking Plant is located. It is known that coking wastewater is composed of complex inorganic and organic contaminants such as ammonia, cyanide, thiocyanide, phenolic compounds, PAHs, etc. PAHs are widespread contaminants throughout the environment, originated mainly from anthropogenic sources such as the combustion of fossil fuels and the direct release of oil and oil products (Simpson et al., 1996). It is known that many of the PAHs with four or more rings are carcinogenic and mutagenic due to their metabolic transformation capacity (Handa et al., 1983). It has been reported that the ratios of PAH with similar molecular weights can be used as indices for source apportionment (Yunker et al., 2002; Mai et al., 2003; Wang et al., 2009). ANT/(ANT+ PHE) b 0.1 and BaA/(BaA+ CHR) b 0.2 are indicative of petrogenic sources; for a pyrogenic source, these ratios would be >0.1 and >0.35, respectively. INP/(INP+ BghiP) ratiosb 0.2 are possibly for a petrogenic source, and 0.2–0.5 for liquid fossil fuel combustion. FLUO/(FLUO + PYR) ratios b 0.4 suggest a petrogenic source, 0.4 to 0.5 a liquid fossil fuel combustion, while ratios> 0.5 are characteristics of coal, grass, or wood combustion. In this study, the ratio of ANT/(ANT + PHE) (mean 0.09) was narrow below 0.1, but the BaA/(BaA+ CHR) ratio (mean 0.36) was above 0.35. In addition, the INP/(INP + BghiP) ratio was in the range of 0.38–0.51,

with the mean at 0.47. Therefore it can be inferred that liquid fossil fuel input is one of the important sources for PAH in Poyang Lake. For the ratio of FLUO/(FLUO + PYR), the peak value was 0.62, found at site R13 (Pojiang River estuary). These results indicated that combustion of coal, grass and wood is a main source of PAH pollution in Pojiang River. The river flows through the north-east of Jiangxi Province, where there are many coal combustion plants such as ceramic factories, non-ferrous metal smelters, and coking plants. 3.3. FT-ICR MS analysis Considering the high cost of analysis and relatively high PAH levels, only the sediment extract from site R13 was subjected to FT-ICR MS analysis. The calibrated negative ion ESI FT-ICR mass spectrum of the extract is presented in Figure S1, Supporting information. Most of the dominant peaks correspond to alkane acids, which might originate from the oxidation of diesel oil leaking from ships. In this study, the interests were focused on the identification of PAH metabolites by the use of ultrahigh mass resolution and ultrahigh mass accuracy of ESI FT-ICR MS. As shown in Table 4, four peaks and their corresponding possible representative structures are listed. To the best of our knowledge, no such PAH metabolite has been reported to date, despite extensive studies on PAH degradation and transformation. In this study, however, accurate quantification of these degradation

Table 2 Levels of PAHs in the sediments of Poyang Lake. PAHs

Detection frequency (%)

NAP ACE AC FLU ANT PHE FLUO PYR BaA CHR BbF BkF BaP BghiP INP DBA ∑PAHs

100 75.0 75.0 100 93.8 100 87.5 93.8 87.5 100 75.0 75.0 62.5 75.0 75.0 56.3 –

ND: not detected.

PAH concentrations (μg/kg) Range

Mean

Median

15.3–44.2 ND–3.4 ND–6.3 2.5–18.6 ND–8.2 14.8–75.2 ND–36.8 ND–31.5 ND–9.2 0.5–16.2 ND–46.3 ND–11.8 ND–19.3 ND–18.5 ND–15.4 ND–8.2 33.0–369.1

23.5 1.1 2.5 7.4 3.3 32.6 15.2 13.7 3.5 6.3 18.4 4.6 7.5 7.2 6.3 3.8 157.0

18.6 0.8 1.6 5.2 2.5 25.3 8.5 7.2 2.1 4.8 12.8 3.1 5.3 5.1 4.8 2.2 109.9

Table 3 Total concentrations of PAHs in the sediments of Poyang Lake (μg/kg, mean value ± standard deviation, n= 5). Sampling site

∑PAH concentration

R1 R2 R3 R4 R5 R6 R7 R8 R9 R10 R11 R12 R13 R14 R15 R16

95.4 ± 38.5 85.4 ± 36.8 166.4 ± 62.0 148.2 ± 55.2 33.0 ± 11.5 108.2 ± 42.6 186.2 ± 72.5 103.2 ± 36.3 205.1 ± 82.1 135.6 ± 55.6 178.5 ± 82.6 253.4 ± 88.4 369.1 ± 138.5 214.0 ± 71.5 135.2 ± 41.3 93.8 ± 38.7

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Table 4 FT-ICR mass spectrometry measurements and putative identifications of PAH metabolites. No.

Observed peak (m/z)

Ion form

Empirical formula

Theoretical ion mass (Da)

1

167.04973

[M–H]−

[C12H7O]−

167.04969

0.24

ACE

2

212.01089

[M–H]−

[C12H4O4]−

212.01096

−0.33

ACE

3

254.05776

[M–H]−

[C15H10O4]−

254.05791

−0.59

PYR

4

197.06038

[M–H]−

[C13H9O2]−

197.06025

0.66

PYR

products is rarely possible due to the lack of analytical reference standards (Radjenovic et al., 2009). Postulated degradation pathways of ACE and PYR are shown in Fig. 4. Fig. 4 was partly based on the results of Selifonov et al. (1998) who investigated ACE metabolism using different liquid bacterial cultures. Generally speaking, biodegradation of ACE occurred predominantly via oxidation of benzylic methylenic groups. The bacterial degradation of PAHs generally begins with a dioxygenase attack on one of the aromatic rings to produce a cis-dihydrodiol, which is then dehydrated to catechol. The ring is cleaved between the hydroxyl groups or adjacent to one of the hydroxyl groups. Ring degradation may appear successively, so that the structure is ultimately transformed to molecules that can enter the central metabolic pathways of the bacteria (Cerniglia, 1984, 1992). However, some studies (Kelley et al., 1993; Casellas et al., 1997) also showed that many other reactions may occur in parallel, especially during cometabolic degradation of PAHs.

Mass error (±ppm)

Proposed structure

Parent PAH

compounds. For PAHs, NAP, FLU, PHE, PYR, and BbF were predominant congeners in sediments studied. Analysis of the possible sources of PAHs indicated an input of petrogenic (liquid fossil fuel combustion and leakage) PAH origin except at site R13 (Pojiang River estuary), where the pyrogenic source was dominant. Several PAH metabolites were identified and possible degradation pathways were proposed. Future studies should be performed to investigate the toxicological effects of POPs and PAHs in sediments of Poyang Lake. In general, our research has significance in providing basic information of POP pollution in Poyang Lake, the largest freshwater lake in China.

Acknowledgments This work was funded by the National Natural Science Foundation of China (No. 41102231). The authors are grateful to professor Quan Shi, China University of Petroleum, for his enthusiastic assistance in FT-ICR MS analysis.

4. Conclusions In this study, the levels of OCPs and 16 priority PAHs were determined in sediment samples collected from 16 sites in Poyang Lake, China. The levels of OCPs in surface sediments were relatively high. With regard to OCPs, γ-HCH and p,p′-DDD were the most abundant

Appendix A. Supplementary data Supplementary data to this article can be found online at http:// dx.doi.org/10.1016/j.scitotenv.2012.06.108.

(a) HOC

O=C

O=C

O=C

O=C

O

O

OH

(b)

OH OH

O

O OH OH COOH

Fig. 4. Postulated degradation pathway of (a) acenaphthene and (b) pyrene in sediments.

O

C=O

M. Lu et al. / Science of the Total Environment 433 (2012) 491–497

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