Occurrence of Polychlorinated Diphenyl Sulfides (PCDPSs) in Surface

Aug 29, 2014 - of twenty-one types of PCDPSs in the surface sediments and in surface water from the Nanjing section of the Yangtze River were examined...
0 downloads 0 Views 746KB Size
Download PDF
Article pubs.acs.org/est

Occurrence of Polychlorinated Diphenyl Sulfides (PCDPSs) in Surface Sediments and Surface Water from the Nanjing Section of the Yangtze River Xuesheng Zhang, Li Qin, Ruijuan Qu, Mingbao Feng, Zhongbo Wei, Liansheng Wang, and Zunyao Wang* State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210023, China S Supporting Information *

ABSTRACT: Polychlorinated diphenyl sulfides (PCDPSs) are dioxin-like compounds that could induce various adverse effects to organisms. However, little is known about the occurrence of PCDPSs in the riverine environment. In the present study, the concentrations of twenty-one types of PCDPSs in the surface sediments and in surface water from the Nanjing section of the Yangtze River were examined. A total of 19 types of PCDPSs were detected and ∑PCDPSs concentrations in surface sediment and surface water ranged from 0.10 to 6.90 ng/g and 0.18 to 2.03 ng/L, respectively. The 2,2′,4,4′,5-penta-CDPS was the dominant congener in sediment (19.9%) and 2,2′,3,3′-tetra-CDPS was the most abundant congener in water (12.2%). The tetra-CDPSs were the dominant congeners both in sediment and in water. Compared with sediment, the percentage of lower chlorinated PCDPSs in water increased distinctly. Source analysis revealed that the PCDPSs in the sediment and in the water mainly came from chemical wastewater rather than domestic sewage. There was a significant linear correlation between ∑PCDPS concentrations and sediment TOC contents, while no linear correlation existed between ∑PCDPS concentrations and water DOC contents. This study demonstrated the prevalent contamination by PCDPSs in sediments and in water from the Nanjing section of the Yangtze River.

■

mouse hepatoma cells.6 Recently, our studies demonstrated that PCDPSs could induce hepatic oxidative stress in fish and mice.7,8 In addition, Zhang et al. examined the aromatic hydrocarbon receptor (AhR) effect of 18 types of PCDPSs, and the results demonstrated that the relative potency (relative to 2,3,7,8-TCDD) values of 2,4,4′,5-tetra-CDPS, 2,2′,3′,4,5-pentaCDPS and 2,2′,3,3′,4,5,6-hepta-CDPS are 1.0 × 10−4, 1.1 × 10−4 and 6.8 × 10−4, respectively.9 The relative potency values of the three PCDPSs are higher than those of several dioxin-like PCBs (DL-PCBs), such as PCB-118 and PCB-189, whose TEF values proposed by the World Health Organization (WHO) in 2005 are all 3.0 × 10−5.10 These studies provided evidence that PCDPSs had certain ecological and health risks. Previous studies revealed that PCDPSs were detected in various environmental samples. Sinkkonen et al. found that PCDPSs existed in the fly ash of metal reclamation plants, and they also detected tri-CDPS isomers in pulp mill effluent samples, as well as tri- and tetra-CDPSs in stack gases from a

INTRODUCTION Polychlorinated diphenyl sulfides (PCDPSs), a series of sulfur analogues of polychlorinated diphenyl ethers (PCDEs), are considered dioxin-liked compounds (DLCs) (Figure 1).

Figure 1. Structural formula of PCDPSs.

PCDPSs contain 209 types of congeners and have wide applications. For example, 2,4,4′,5-tetra-CDPS (Tetrasul) is an efficient acaricide and has been used in fruit production process in many countries (e.g., China, which is also a producer).1−3 Nakanishi et al. implied that some higher chlorinated PCDPSs can be used as high-temperature lubricants in gas turbine or jet engines.4 Naito et al. found that PCDPSs could be used in the prevention and cure of acidophilic granulocyte-related diseases.5 Until recently the understanding of the toxicological effects of PCDPSs has been far from sufficient. Kopponen et al. found that 3,3′,4,4′-tetra-CDPS had CYP1A1-inducing potencies in © 2014 American Chemical Society

Received: Revised: Accepted: Published: 11429

May 4, August August August

2014 19, 2014 29, 2014 29, 2014

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

Figure 2. Sampling sites in the Nanjing section of the Yangtze River. Y1−Y9 (blue marks) are sampling points in the Nanjing section of the Yangtze River; T1-T5 (burgundy marks) are sampling points in five local rivers that flow into the Yangtze River.

■

waste incinerator.11−13 Schwarzbauer et al. identified 4,4′-diCDPS in sediment samples from the Elbe River.14 Because of the lack of pure individual congeners, those reports only focused on several specific PCDPSs. The distribution of PCDPSs in surface sediments and surface water of the river environment may influence the fate of these dioxin-liked compounds, which is an issue that has not received enough attention. The Yangtze River, the longest river in China extends approximately 6400 km from the Qinghai−Tibet Plateau to the East China Sea and is characterized by intense industrial and urban activity, especially in its lower reaches and estuaries in Eastern China.15 Nanjing is one of six major industrial cities located in the Eastern China, as well as the center of petroleum processing and chemical manufacturing in this region.16 The rapid economic expansion, along with improper urban planning, has caused enormous environmental pressures on the Yangtze River. Many pollutants, especially persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and phthalic acid esters (PAEs), have been discharged into the Yangtze River and have accumulated in water, sediments and biota.17−19 However, as a class of DLCs, there was no data to describe the contamination status of PCDPSs in sediment and water from the Yangtze River. The objective of this study is to investigate the levels, compositional patterns, and possible sources of PCDPSs in surface water and surface sediments from the Nanjing section of the Yangtze River. First, we established the analytical method for PCDPSs based on the synthesized pure PCDPSs. Second, the surface water and surface sediments from the Nanjing section of the Yangtze River were collected and the levels of twenty-one types of PCDPSs were analyzed. Third, the congener profiles of PCDPSs and possible sources in water and sediment samples were discussed. Finally, the relationships between the total PCDPS (∑PCDPSs) concentrations, sediment total organic carbon (TOC) content and water dissolved organic carbon (DOC) content were investigated.

MATERIALS AND METHODS Preparation of PCDPSs. Twenty-one types of PCDPSs that were used in the present study were synthesized following the methods from a previous report.20 Structures and purities of all synthesized PCDPSs were characterized by 1H NMR and GC-MS spectra (Supporting Information (SI), Figure S1). Other chemicals and materials that were used in this study are listed in the SI. Sampling. Surface sediments and surface water were collected from the Yangtze River in July, 2013. Nine sites (Y1 to Y9) were selected (Figure 2) and the detailed site descriptions are given in Table S1 (see SI). Surface sediment samples (0−12 cm) were collected using a stainless steel grab sampler. All sediment samples were stored at −20 °C in a refrigerator until analysis. Surface water samples were taken from the top layer (0−40 cm) using a 4 L precleaned stainless steel barrels. Then, the collected surface water samples were transferred into precleaned 4 L brown glass containers and transported to the laboratory within 24 h. Surface water samples were stored at 4 °C in a refrigerator before further analysis. Extraction. Surface sediments were freeze-dried using a freeze drier (FreezeZone, Labconco, Kansas City, MO), and then sieved through a 100 mesh (0.15 mm) sieve. An accelerated solvent extractor (ASE-350, Dionex, Sunnyvale, CA) was used for the extraction of PCDPSs in the sediment samples. Fifteen grams of the sieved sediment spiked with an internal standard (13C-labeled PCB-153) was mixed with 3.75 g of diatomite. The mixture was transferred into a 34 mL extraction cartridge and extracted by dichloromethane and toluene (1:3 v/v) under 1500 psi at 100 °C. The process was carried out in three cycles with 6 min of heating followed by 10 min of static extraction. The flush volume was 60%, and the nitrogen purge time was 60 s. The extracted solution was concentrated to approximately 15 mL in a rotary evaporator (RV-10, IKA, Germany) for subsequent purifications. All surface water samples were filtered using a 45 μm membrane before extraction. Prior to extraction, a 1.2 L water sample was spiked with 5 ng of internal standards (13C-labled PCB-153) and mixed sufficiently. A solid phase extraction (SPE) procedure for the collection of the target compounds 11430

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

Table 1. ∑PCDPS Concentrations in Sediments from Nine Sampling Sites in the Nanjing Section of the Yangtze Rivera

a

no.

compounds

LOQ

Y1

Y2

Y3

Y4

Y5

Y6

Y7

Y8

Y9

1 2 4 5 6 7 8 9 10 11 12 13 15 16 17 18 19 20 21 22 23

DPS 4-mono-CDPS 4,4′-di-CDPS 3,4′-di-CDPS 2,4,5-tri-CDPS 2,4′,5-tri-CDPS 2,4′,6-tri-CDPS 2,2′,3-tri-CDPS 2,4,4′,5-tetra-CDPS 2,3′,4,5-tetra-CDPS 2,2′,3,5′-tetra-CDPS 2,2′,3,6′-tetra-CDPS 2,2′,3,3′-tetra-CDPS 2,2′,4,4′,5-penta-CDPS 2,3,4,5,6-penta-CDPS 2,2′,3,4′,5′-penta-CDPS 2,2′,3,4,5,6-hexa-CDPS 2,3,3′,4,5,6 -hexa-CDPS 2,3,4,4′,5,6-hexa-CDPS 2,3,3′,4, 4′,5,6-hepta-CDPS 2,2′,3,3′,4,5,6-hepta-CDPS ∑PCDPSs (ng/g)

0.025 0.030 0.015 0.032 0.020 0.020 0.060 0.040 0.015 0.020 0.015 0.030 0.025 0.055 0.060 0.065 0.040 0.075 0.085 0.095 0.090

ND ND 0.02 ND 0.02 0.02 ND ND 0.05 0.05 ND 0.04 0.048 ND 0.08 0.07 ND 0.11 0.12 ND 0.12 0.75

0.03 0.07 ND ND ND 0.02 ND 0.04 ND 0.15 0.19 0.03 0.20 0.10 0.07 0.07 ND ND ND ND ND 0.97

0.08 0.03 0.09 0.22 0.28 0.05 ND 0.19 0.02 0.76 0.16 ND 0.81 0.54 0.13 0.49 ND ND 0.53 ND 0.15 4.53

0.07 ND ND ND 0.09 0.03 ND 0.089 0.10 0.31 0.10 ND 0.13 0.29 ND 0.19 ND ND ND ND 0.16 1.56

0.09 0.13 ND 0.04 0.09 ND ND 0.17 0.23 0.18 0.06 ND ND 0.41 ND 0.28 ND 0.18 0.53 ND ND 2.39

ND ND ND ND ND ND ND ND ND 0.02 0.02 ND ND 0.06 ND ND ND ND ND ND ND 0.10

0.08 0.17 0.23 0.15 0.42 0.16 ND 0.97 0.08 0.34 0.10 0.05 0.47 1.28 0.07 0.32 0.10 0.47 0.24 ND 1.20 6.90

0.07 ND 0.06 0.04 0.04 0.02 ND 0.05 0.20 0.22 0.12 0.07 0.27 0.74 0.06 0.38 0.04 0.10 0.56 ND 0.31 3.35

0.11 0.04 0.05 ND 0.18 0.03 ND 0.09 0.03 0.09 0.06 0.08 ND 0.23 ND 0.18 ND ND ND ND ND 1.17

ND: Not detected or lower than the LOQ.

Table 2. ∑PCDPS Concentrations in Surface Water from Nine Sampling Sites in the Nanjing Section of the Yangtze Rivera

a

no.

compounds

LOQ

Y1

Y2

Y3

Y4

Y5

Y6

Y7

Y8

Y9

1 2 4 5 6 7 8 9 10 11 12 13 15 16 17 18 19 20 21 22 23

DPS 4-mono-CDPS 4,4′-di-CDPS 3,4′-di-CDPS 2,4,5-tri-CDPS 2,4′,5-tri-CDPS 2,4′,6-tri-CDPS 2,2′,3-tri-CDPS 2,4,4′,5-tetra-CDPS 2,3′,4,5-tetra-CDPS 2,2′,3,5′-tetra-CDPS 2,2′,3,6′-tetra-CDPS 2,2′,3,3′-tetra-CDPS 2,2′,4,4′,5-penta-CDPS 2,3,4,5,6-penta-CDPS 2,2′,3,4′,5′-penta-CDPS 2,2′,3,4,5,6 -hexa-CDPS 2,3,3′,4,5,6 -hexa-CDPS 2,3,4,4′,5,6-hexa-CDPS 2,3,3′,4,4′,5,6-hepta-CDPS 2,2′,3,3′,4,5,6-hepta-CDPS ∑PCDPSs (ng/L)

0.010 0.012 0.008 0.006 0.008 0.008 0.010 0.012 0.012 0.010 0.008 0.010 0.012 0.015 0.010 0.016 0.012 0.015 0.020 0.025 0.025

ND ND ND 0.01 0.02 ND ND 0.05 ND 0.02 0.01 0.02 0.05 ND 0.01 0.05 ND ND ND ND 0.06 0.30

0.04 0.08 ND 0.04 0.04 0.18 ND 0.16 ND 0.20 0.03 0.05 0.18 0.05 0.02 0.07 ND ND ND ND 0.03 1.17

0.17 0.12 0.02 0.26 0.09 0.17 ND 0.22 0.07 0.33 0.10 0.03 0.17 0.11 0.06 0.06 ND 0.02 0.03 ND ND 2.03

0.06 0.08 ND ND 0.02 0.14 ND 0.11 ND 0.15 0.02 ND 0.06 0.06 0.03 0.06 ND ND ND ND 0.15 0.94

0.09 0.05 ND 0.02 0.01 0.06 ND 0.13 0.01 0.13 0.07 0.02 0.06 0.09 0.03 0.05 ND 0.04 ND ND ND 0.86

0.01 ND ND ND ND 0.01 ND 0.02 ND 0.01 0.02 0.02 0.02 ND 0.02 ND 0.03 0.02 ND ND ND 0.18

0.09 0.08 0.01 0.04 0.04 0.16 ND 0.29 0.03 0.23 0.02 0.04 0.38 0.04 0.05 0.10 0.02 0.04 ND ND 0.12 1.78

0.06 0.02 0.01 0 0.03 0.20 ND 0.02 0.02 0.19 0.03 0.01 0.13 0.04 0.04 ND ND 0.03 0.03 ND 0.17 1.03

0.07 0.04 ND 0.01 0.04 0.19 ND 0.09 0.01 0.04 0.03 0.03 0.09 0.03 0.03 0.04 0.01 ND ND ND 0.08 0.83

ND: Not detected or lower than the LOQ.

concentrated under nitrogen to approximately 1 mL for subsequent column cleanup procedures. Cleanup. The concentrated extracts of sediments were precleaned using an acid−base washing procedure (see SI) before silica gel column purification. The silica gel cleanup columns (30 cm × 1 cm glass columns) were packed with clean glass-wool, silica gel (1 g), 2% (w/w) base silica gel (2.0 g), silica gel (1.0 g), 44% (w/w) acid silica gel (4.0 g), silica gel (2.0 g), and anhydrous sodium sulfate (2.0 g) from bottom to

was used. The C18 cartridges (Con-Bonward, 12 mL, 2 g, 40 μm, Anpel, China) were cleaned and conditioned with 12 mL of toluene, 12 mL of methanol, and 12 mL of Milli-Q water sequentially. Water was then passed through the cartridge and the flow rate was approximately 4 mL/min. After extraction, a 12 mL mixture of methanol and Milli-Q water (1:1, v/v) was used to wash the cartridge and the washed cartridge was dried under a low vacuum. PCDPSs were then eluted with 12 mL of a DCM and toluene mixture (1:1, v/v). The eluent was 11431

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

Figure 3. Average relative abundances of individual PCDPS congeners in surface sediments and surface water.

with deionized water three times, and dried for 12 h at 105 °C in a heating and drying oven (DHG-9123A, Jinghong, China). The TOC content was determined with an elemental analyzer (Elementar Vavio EL II, Hanau, Germany). Approximately 15 mL of surface water was filtered through a membrane (0.45 μm) and acidified with 1 N HCl. Then, the surface water DOC was measured in a TOC analyzer (TOC-5000A, Shimadzu, Japan).

top. The column cleanup procedure was as follows: the columns were prerinsed with 40 mL of hexane and the eluent was discarded. The concentrated extract (approximately 1 mL) was then transferred to the top of the column, and it was rinsed with 120 mL of n-hexane and dichloromethane (4:1, v/v) at a rate of 3 mL/min. The eluent that contained PCDPSs was concentrated to 1−2 mL in a rotary evaporator and then further concentrated to dryness under a gentle nitrogen flow. Finally, an internal 5 ng injection standard, 13C-labled PCB-31, was added, and the volume was increased to 100 μL using nhexane prior to GC−MS analysis. Instrumental Analysis. PCDPS isomer analysis was performed in a Trace Ultra gas chromatograph system coupled to a Trace DSQ II quadrupole mass spectrometer detector (DSQ II, Thermo Scientific, USA). Details of the GC-MS analysis are listed in the SI, and the retention time and quantitative ions of all tested compounds are listed in Table S2 (see SI). QA/QC. Procedural blanks were injected after the analyses of each sample group in the GC−MS to evaluate the interference from the analytical process that could influence the detection and quantification of PCDPSs. The results showed that interference was negligible. The limits of quantification (LOQ) were defined as 10 times the ratio of signal to instrument noise (10 S/N).21,22 Concentrations that were less than the LOQ were reported as not detected (ND). LOQ varied from congener to congener based on 15 g of dry sediment sample (or 1.2 L water sample) and instrument sensitivity (Table 1 and Table 2). Before sample analysis, the matrix spike (n = 4) for each target compound had been evaluated. The recoveries of PCDPSs ranged from 58.3% to 118.6% in the sediment samples and ranged from 63.5% to 123.8% in the water samples, respectively (see SI, Table S3). To ensure the analytical procedures were conducted properly, 13 C-labled PCB-153 was used as the internal standard. For the sediment analysis, the recoveries of the internal standard (13Clabled PCB-153) ranged from 54.5% to 101.8%. For the water sample analysis, the recoveries of the internal standard (13Clabled PCB-153) ranged from 86.3% to 108.4%. Determination of Sediment TOC and Water DOC. Approximately 1 g of freeze-dried, ground and sieved sediment was treated with 1 N HCl to remove inorganic carbon, washed

■

RESULTS AND DISCUSSION PCDPS Concentrations and Distributions in Sediments and Water. Of the 21 types of PCDPS congeners included in the present work, 19 types of PCDPSs were detected in the surface sediments and in the surface water from the Nanjing section of the Yangtze River. The sediment ∑PCDPS concentrations among the nine sampling sites ranged from 0.10 (at Y6) to 6.90 ng/g (at Y7), with a mean value of 2.41 ng/g (Table 1). The surface water ∑PCDPS concentrations among the nine sampling sites ranged from 0.18 (at Y6) to 2.03 ng/L (at Y3), with a mean value of 1.01 ng/L (Table 2). The highest ∑PCDPSs concentration was found in the sediment sample collected from sampling site Y7 and high ∑PCDPSs concentrations were also found in sediments from Y3 (4.53 ng/g) and Y8 (3.35 ng/g). Furthermore, the highest ∑PCDPSs concentration in surface water was found in the water sample collected from Y3 (2.03 ng/L), followed by Y7 (1.78 ng/L) and Y2 (1.17 ng/L). These results implied that there may have been pollution sources near these sampling sites, such as a paper mill, which can release pulping effluents that contains tri-CDPSs.12 The lowest sediment ∑PCDPSs concentration (0.10 ng/g) occurred at sampling site Y6 followed by Y1 (0.75 ng/g) and Y2 (0.97 ng/g) (Table 1). Similar to the sediment PCDPS distribution, the lowest ∑PCDPSs concentration was found in the water sample collected from Y6 (0.18 ng/L) followed by Y1 (0.30 ng/L) and Y9 (0.86 ng/L) (Table 2). Sampling site Y6 is located where the two tributaries of the Yangtze River mix. Similar to many other hydrophobic organic contaminants, PCDPSs can adsorb onto suspended particles.23−25 However, the strong mixing effect of the running water from the two tributaries washed away the suspended particles, resulting in 11432

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

fewer PCDPSs concentrated in the sediments. Sampling site Y1 was located upstream of the Nanjing section of the Yangtze River, and the lower PCDPS concentrations measured indicated that the upstream district produced a smaller contribution to the PCDPS pollution of the Nanjing section of the Yangtze River. PCDPSs Compositional Patterns and Their Possible Sources. The individual congener profiles of surface sediment and surface water are shown in Figure 3. 2,2′,4,4′,5-pentaCDPS was the predominant congener among the 19 detected PCDPSs in sediments, with an average relative abundance of 19.9%, followed by 2,3′,4,5-tetra-CDPS and 2,2′,3,4′,5′-pentaCDPS, with average relative abundances greater than 8.0%. The results indicated that these compounds were resistant to degradation and removal processes in the sediment. Unlike the sediment samples, 2,2′,3,3′-tetra-CDPS was the most abundant congener in surface water samples among the 19 detected PCDPSs, with an average relative abundance of 12.2%. The average relative abundances of 2,3′,4,5-tetra-CDPS, 2,2′,3-tri-CDPS and 2,4′,5-tri-CDPS were also greater than 10%, suggesting that these compounds are the major contents of the ∑PCDPSs in surface water. The present results are partly in accordance with previous theoretical research, which indicated that PCDPSs with paired substituted Cl atoms in two benzene rings are more stable.26 Moreover, 2,3′,4,5-tetra-CDPS was detected in all samples, while 2,4′,6-tri-CDPS and 2,3,3′,4,4′,5,6-hepta-CDPS were not detectable in any of the samples. The PCDPSs homologue profiles of the sediment and water samples are shown in Figure 4. The distribution patterns of the PCDPSs congeners in sediments and water varied according to the sampling sites (Figure 4). The reason may be that the PCDPS sources in the surface sediments and surface water of the Nanjing Section of the Yangtze River vary largely according to the sampling sites. For sediment samples, the PCDPSs were dominated by tetraand penta-CDPSs. The percent contributions of tetra- and penta-CDPSs in sediment from nine sample locations ranged from 15.1−58.8% and 20.0−60.0%, respectively. DPS, mono-, and di-CDPSs only contributed to 0−17.1% of the ∑PCDPSs, and tri-CDPSs contributed to 0−25.6% of the ∑PCDPSs. The tendency of the congener distribution to be dominated by tetra- and penta- CDPSs in sediments from the Nanjing section of the Yangtze River is similar to PCBs distribution patterns in sediment from rivers around the world. Yang et al. found that tetra-PCBs and penta-PCBs were identified as the dominating compounds in the surface sediments from the Wuhan reach of the Yangtze River, having a percent contribution of 36.6% and 23.7%, respectively.27 Jeong et al. suggested that the PCB congeners identified in sediment of the lower Nakdong River were predominated by tetra- (5.4−30%) and penta-PCBs (32−66%).28 The soil sorption coefficient normalized to organic carbon (logKoc), which was used to account for soil−water distribution, could provide some explanations for the distribution patterns of PCDPSs in sediments.29 In general, compounds with a larger logKoc could absorb onto sediment particles more easily. The logKoc of tetra-, penta- and hexa-CDPSs ranged from 4.96 to 6.52, and the logKoc of DPS, mono-, di- and tri-CDPSs ranged from 3.64 to 4.75 (see SI, Table S4), which suggested that tetra-, penta-, and hexa-CDPSs are more easily combined with sediment particles and resulted in a higher sediment concentration.30 Meanwhile, the contents of tetra- and penta-

Figure 4. Percent contribution of different substituted PCDPSs in surface sediments and surface water from the Nanjing section of the Yangtze River. (A) Surface sediment; (B) Surface water.

CDPSs were particularly high, which reflected that those congeners were more resistant to degradation and removal processes, and easily accumulate in the environment and in organisms. Figure 4 shows that the PCDPSs distribution pattern in surface water was obviously different to that in surface sediment. DPS to hepta-CDPSs were detected in the sediment samples from the Y1 sampling site, while no hexa-CDPSs were detected in the water samples, although hepta-CDPSs were detected in a high proportion. The hexa-CDPSs in the sediments may come from the degradation of hepta-CDPSs, which are difficult to release into surface water because of their high hydrophobicity. Highly chlorinated PCDPSs (hexa-CDPSs and heptaCDPSs) were found in surface water from Y2, Y6, and Y9, while these PCDPSs were not found in the corresponding sediment samples. The reason is that the LOQs of high chlorinated PCDPSs in sediment were higher than those in water (e.g., LOQs of hexa-CDPSs in sediment ranged from 0.040 to 0.085 ng/g, while LOQs ranged from 0.012 to 0.020 ng/L in water). Although hexa-CDPSs and hepta-CDPSs were detected in the sediment samples from Y2, Y6, and Y9, the concentration of these compounds were below their LOQs. Hence, the percent contributions of these compounds to the ∑PCDPSs were neglected and resulted in a significant difference. For all sampling sites, the tetra-CDPSs were the dominant congeners in surface water, with its percent contribution ranging from 24.1 to 39.3% (with a mean value of 33.8%). Compared with surface sediment, the percent contribution of 11433

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

The ∑PCDPS concentrations in the sediment and water from site T5 (5.84 ng/g and 2.59 ng/L) and site T3 (4.82 ng/g and 1.80 ng/L) was higher than most sampling sites in the Yangtze River, suggesting that the two tributaries had contributions to the ∑PCDPSs in the Yangtze River. Site T3 was located in the Macha River and site T5 was located in the Chu River. The Macha River flows through an economic development zone of Nanjing, where there were a large number of chemical plants and pharmaceutical companies. In addition, the Nanjing Chemical Industry Park (NCIP) is located west of the Chu River. As expected, a large amount of chemical wastewater with various toxic pollutants was discharged into the two rivers. Thus, we speculated that chemical industrial park effluent was likely to be an important source of PCDPSs. However, detailed sources of PCDPSs need to be verified by the analysis of the chemical effluents of different chemical plants at these sites in future studies. Correlations Between ∑PCDPS Concentrations and TOC/DOC. In this study, the TOC content of the sediments was measured (See SI, Table S5), and the relationships between ∑PCDPSs concentrations and TOC contents were investigated. The statistical examination showed a significant correlation (R2 = 0.64, p < 0.05, n = 14) between ∑PCDPSs and TOC in the studied sediments (see SI, Figure S4). Data in the current study was consistent with the findings of previous studies that reported the distribution of hydrophobic organic pollutants (HOPs), which were mainly influenced by TOC content.36,37 The DOC content of surface water was determined (see SI, Table S4) and the relationship between DOC contents and ∑PCDPSs concentrations in surface water were evaluated. The result revealed almost no linear correlation between the ∑PCDPSs and DOC (R2 = 0.01, p < 0.05, n = 14) (see SI, Figure. S4). The relationship may be explained by the following reason: PCDPSs mainly came from the pollutant discharge of chemical industries, while water from T1, T2, T4, and Y2 were mainly polluted by domestic sewage. Although the DOC contents of water samples from the four sampling sites were high, the ∑PCDPSs were lower, resulting in poor linearity. Implications. The present study demonstrated the prevalent presence of PCDPSs in the Nanjing section of the Yangtze River for the first time. The PCDPS profiles in surface water and surface sediments suggested tetra-CPDSs were the dominant congeners, which is similar to profiles of PCBs. Despite the fact that our results showed the amounts of ∑PCDPSs in sediment and in water were lower, PCDPSs should receive more attention in the future because of their toxic effects. In addition, the Nanjing section of the Yangtze River receives tens of millions of tons of industrial wastewater and domestic sewage from Nanjing city each year. The increasing chemical industrial wastewater in Nanjing may bring more PCDPSs into the Yangtze River. However, the environmental and biological processes of PCDPSs in the water environment and their contamination status in aquatic organisms are still unknown. Therefore, further studies about PCDPSs on these issues should be conducted to evaluate environmental risks.

lower chlorinated PCDPSs (mon-, di-, and tri-CDPSs) in surface water showed a distinct increase. For example, triCDPSs accounted for 16.7 to 38.6% of the ∑PCDPSs in the surface water samples, while tri-CDPSs only contributed to 0 to 25.6% of the ∑PCDPSs in the sediment samples. In parallel, decreases in the percent contribution of medium and highly chlorinated (penta-, hexa-and hepta-CDPS) PCDPSs were recorded (e.g., the content of penta-CDPS in the surface water samples ranged from 7.8 to 20.0%, while they contributed to 20.0 to 60.0% of the ∑PCDPSs in the sediment sample). As aforementioned, the surface water sample profiles were skewed toward lower chlorinated PCDPSs, which is similar to PCBs congener profiles in water samples from other locations. For instance, relatively high proportions of tri- and tetrachlorinated PCBs were detected in surface water from the Yangtze River Delta in a previous study.31 Similar distribution characteristics were also reported in surface water samples from an industrial harbor of Lake Michigan and from sea-surface microlayer and subsurface water samples of the Venice Lagoon.32,33 The surface water investigation revealed the general prevalence of lower and medium chlorinated (e.g., mon-, di-, tri-, and tetra-) PCDPSs. This is due to the smaller logKow (noctanol−water partition coefficient) of lower and medium chlorinated PCDPSs than that of highly chlorinated (hexa- and hepta-) PCDPSs (see SI, Table S4).34 The lower logKow leads to the higher water solubility; therefore, compounds with smaller logKows tend to transition to a water phase. Otherwise, because of the high logKow, highly chlorinated PCDPSs are likely to adsorb to suspended particles in water and then settle into the sediments under the influence of gravity.35 To evaluate the possible sources of PCDPSs, five sample locations (T1 to T5) were selected in the Yangtze River tributaries in the Nanjing Section (Figure 2). The ∑PCDPS concentrations in the sediment and surface water from T1 to T5 were determined (Table 3). Table 3. ∑PCDPS Concentrations in the Surface Sediments and Surface Water from Five Local Rivers That Flow into the Nanjing Section of the Yangtze Rivera

a

sampling sites

∑PCDPSs in sediments (ng/g)

∑PCDPSs in water (ng/L)

T1 T2 T3 T4 T5

0.10 0.32 4.82 0.09 5.84

ND 0.15 1.80 ND 2.59

ND: Not detected or lower than the LOQ.

The ∑PCDPSs concentrations in the sediment and the water from location T1, T2, and T4 were relatively smaller than those in the samples from the Yangtze River, which indicated that the three tributaries had a lower contribution to the ∑PCDPSs in the Yangtze River. The T2 sampling site was located in Qinhuai District, which is a traditional living quarters for residents in Nanjing city. In this area, the discharge of domestic wastewater was the primary pollution source. The ∑PCDPS concentrations in the sediment and surface water from location T2 were lower than those in the Y3 and Y4 sampling sites. The results indicated that domestic pollution sources contributed little to the PCDPS contamination in the Yangtze River, Nanjing section.

■

ASSOCIATED CONTENT

S Supporting Information *

Additional information on the 1H NMR and GC-MS spectra of PCDPSs, acid−base washing procedures, GC-MS analysis, Figure S1-Figure S4, and Table S1-Table S5 can be found in the 11434

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

diphenylsulfides formed in metal reclamation. Organohalogen Compd. 1993, 11, 195−198. (14) Schwarzbauer, J.; Littke, R.; Weigelt, V. Identification of specific organic contaminants for estimating the contribution of the Elbe River to the pollution of the German Bight. Org. Geochem. 2000, 31, 1713− 1731. (15) Wu, B.; Zhao, D. Y.; Zhang, Y.; Zhang, X. X.; Cheng, S. P. Multivariate statistical study of organic pollutants in Nanjing reach of Yangtze River. J. Hazard. Mater. 2009, 169, 1093−1098. (16) Su, G. Y.; Liu, X. H.; Gao, Z. S.; Xian, Q. M.; Feng, J. F.; Zhang, X. W.; Giesy, J. P.; Wei, S.; Liu, H. L.; Yu, H. X. Dietary intake of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) from fish and meat by residents of Nanjing, China. Environ. Int. 2011, 42, 138−143. (17) Yang, H. Y.; Zhuo, S. S.; Xue, B.; Zhang, C. L.; Liu, W. P. Distribution, historical trends and inventories of polychlorinated biphenyls in sediments from Yangtze River Estuary and adjacent East China Sea. Environ. Pollut. 2012, 169, 20−26. (18) Gao, Z. S.; Xu, J.; Xian, Q. M.; Feng, J. F.; Chen, X. H.; Yu, H. X. Polybrominated diphenyl ethers (PBDEs) in aquatic biota from the lower reach of the Yangtze River, East China. Chemosphere 2009, 75, 1273−1279. (19) Wang, F.; Xia, X. H.; Sha, Y. J. Distribution of phthalic acid esters in Wuhan section of the Yangtze River, China. J. Hazard. Mater. 2008, 154, 317−324. (20) Zhang, X. S.; Shi, J. Q.; Sun, L.; Wang, Z. Y. Palladium-catalyzed carbon-sulfur bond formation to synthesize polychlorinated diphenyl sulfides. Chin. J. Org. Chem. 2011, 31, 1107−1113. (21) Zheng, J.; Xiao, Y.; Chen, S. J.; Peng, X. W.; Hu, G. C.; Chen, K. H.; Luo, X. J.; Mai, B. X.; Yang, Z. Y. Polychlorinated biphenyls in human hair at an e-waste site in China: Composition profiles and chiral signatures in comparison to dust. Environ. Int. 2013, 54, 128− 133. (22) Zhou, Z.; Liang, Y.; Shi, Y. L.; Xu, L.; Cai, Y. Q. Occurrence and transport of perfluoroalkyl acids (PFAAs), including short-chain PFAAs in Tangxun Lake, China. Environ. Sci. Technol. 2013, 47, 9249−9257. (23) Schneider, A. R.; Eadie, B. J.; Kaker, J. E. Episodic particle transport events controlling PAH and PCB cycling in Grand Traverse Bay, Lake Michigan. Environ. Sci. Technol. 2002, 36, 1181−1190. (24) Talley, J. W.; Ghosh, U.; Tucker, S. G.; Furey, J. S.; Luthy, R. G. Particle-scale understanding of the bioavailability of PAHs in sediment. Environ. Sci. Technol. 2002, 36, 477−483. (25) Chen, S. J.; Gao, X. J.; Mai, B. X.; Chen, Z. M.; Luo, X. J.; Sheng, G. Y.; Fu, J. M.; Zeng, E. Y. Polybrominated diphenyl ethers in surface sediments of the Yangtze River Delta: Levels, distribution and potential hydrodynamic influence. Environ. Pollut. 2006, 144, 951− 957. (26) Zhu, H. W.; Jiang, J. L.; Wang, Z. Y.; Wang, L. S.; Yu, H. X. DFT Study on the structural parameters and thermodynamic properties of polychlorinated diphenyl sulfides. Acta Chimica Sinica 2008, 66, 1139−1150. (27) Yang, Z. F.; Shen, Z. Y.; Gao, F.; Tang, Z. W.; Niu, J. F. Occurrence and possible sources of polychlorinated biphenyls in surface sediments from the Wuhan reach of the Yangtze River, China. Chemosphere 2009, 74, 1522−1530. (28) Jeong, G. H.; Kim, H. J.; Joo, Y. J.; Kim, Y. B.; So, H. Y. Distribution characteristics of PCBs in the sediments of the lower Nakdong River, Korea. Chemosphere 2001, 44, 1403−1411. (29) dos Reis, R. R.; Sampaio, S. C.; de Melo, E. B. An alternative approach for the use of water solubility of nonionic pesticides in the modeling of the soil sorption coefficients. Water. Res. 2014, 53, 191− 199. (30) Yang, F.; Qu, R. J.; Wang, M.; Tang, Y. Q.; Feng, M. B.; Wang, Z. Y. Experimental and QSPR study of sorption properties of polychlorinated diphenylsulfides (PCDPSs) in Yangtze River plain soil. Geoderma 2013, 193−194, 140−148. (31) Zhang, L. F.; Shi, S. X.; Dong, L.; Zhang, T.; Zhou, L.; Huang, Y. R. Concentrations and possible sources of polychlorinated

Supporting Information. This material is available free of charge via the Internet at http://pubs.acs.org.

■

AUTHOR INFORMATION

Corresponding Author

*Phone/fax: +86 25 89680358; e-mail: [email protected]. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This research was financially supported by the National Natural Science Foundation of China (No. 41071319, 21377051), the Major Science and Technology Program for Water Pollution Control and Treatment of China (No. 2012ZX07506-001) and the Scientific Research Foundation of the Graduate School of Nanjing University (2013CL08).

■

REFERENCES

(1) Verschuuren, H. G.; Kroes, R.; Van Esch, G. J. Toxicity studies on tetrasul I. Acute, long-term and reproduction studies. Toxicology 1973, 1, 63−78. (2) Unger, T. A. Pesticide Synthesis Handbook: Tetrasul; Noyes Publications: Saddle River, NJ, 1996; pp 832. (3) Yang, X.; Zhang, H.; Liu, Y.; Wang, J.; Zhang, Y. C.; Dong, A. J.; Zhao, H. T.; Sun, C. H.; Cui, J. Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography−mass spectrometry: Determination of 88 pesticides in berries using SPE and GC−MS. Food Chem. 2011, 127, 855−865. (4) Nakanishi, H.; Umemoto, N. Thermal-resistant lubricating oil composition for gas turbines or jet engines. 2002, 13 JP 2002003878 A. (5) Naito, Y.; Akaboshi, F.; Goto, T.; Sugyama, N.; Ono, S.; Fukaya, T.; Kuwabara, E.; Kajii, M.; Nishimura, H.; Sugiura, M. Diphenyl sulfides, sulfoxides, and sulfones for prevention and treatment of eosinophil-related diseases. 1995, 21 JP 07048251 A. (6) Kopponen, P.; Sinkkonen, S.; Poso, A.; Gynther, J.; Kaerenlampi, S. Sulfur analogues of polychlorinated dibenzo-p-dioxins, dibenzofurans and diphenyl ethers as inducers of cyp1a1 in mouse hepatoma cell culture and structure-activity relationships. Environ. Toxicol. Chem. 1994, 13, 1543−1548. (7) Li, Y.; Li, M.; Shi, J. Q.; Wang, Z. Y. Hepatic antioxidative responses to PCDPSs and estimated short-term biotoxicity in freshwater fish. Aquat. Toxicol. 2012, 120−121, 90−98. (8) Zhang, X. S.; Liu, F.; Chen, B. Y.; Li, Y.; Wang, Z. Y. Acute and subacute oral toxicity of polychlorinated diphenyl sulfides in mice: Determining LD50 and assessing the status of hepatic oxidative stress. Environ. Toxicol. Chem. 2012, 31, 1485−1493. (9) Zhang, R.; Zhang, X. W.; Zhang, J. J.; Qu, R. J.; Zhang, J. M.; Liu, X.; Chen, J.; Wang, Z. Y.; Yu, H. X. Interaction with AHR1 receptor and avian inter-species sensitivity variation by polychlorinated diphenylsulfides. Environ. Sci. Technol. 2014, DOI: 0.1021/es502641f. (10) Van den Berg, M.; Birnbaum, L. S.; Denison, M.; De Vito, M.; Farland, W.; Feeley, M.; Fiedler, H.; Hakansson, H.; Hanberg, A.; Haws, L.; Rose, M.; Safe, S.; Schrenk, D.; Tohyama, C.; Tritscher, A.; Tuomisto, J.; Tysklind, M.; Walker, N.; Peterson, R. E. The 2005 World Health Organization reevaluation of human and mammalian toxic equivalency factors for dioxins and dioxin-Like compounds. Toxicol. Sci. 2006, 93, 223−241. (11) Sinkkonen, S. Environmental analysis of chlorinated aromatic thioethers, sulfoxides and sulphones. J. Chromatogr., A 1993, 642, 47− 52. (12) Sinkkonen, S.; Kolehmainen, E.; Laihla, K.; Koistinen, J.; Rantio, T. Polychlorinated diphenyl sulfides: Preparation of model compounds, chromatography, mass spectrometry, NMR, and environmental analysis. Environ. Sci. Technol. 1993, 27, 1319−1326. (13) Sinkkonen, S.; Vattulainen, A.; Aittola, J. P.; Paasivirta, J.; Lahtiperä, M. Polychlorinated dibenzothiophenes, thianthrenes and 11435

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436

Environmental Science & Technology

Article

biphenyls in the surface water of the Yangtze River Delta, China. Chemosphere 2011, 85, 399−405. (32) Martinez, A.; Wang, K.; Hornbuckle, K. C. Fate of PCB congeners in an industrial harbor of Lake Michigan. Environ. Sci. Technol. 2010, 44, 2803−2808. (33) Manodori, L.; Gambaro, A.; Piazza, R.; Ferrari, S.; Stortini, A. M.; Moret, I.; Capodaglio, G. PCBs and PAHs in sea-surface microlayer and sub-surface water samples of the Venice Lagoon (Italy). Mar. Pollut. Bull. 2006, 52, 184−192. (34) Shi, J. Q.; Zhang, X. S.; Qu, R. J.; Xu, Y.; Wang, Z. Y. Synthesis and QSPR study on environment-related properties of polychlorinated diphenyl sulfides (PCDPSs). Chemosphere 2012, 88, 844−854. (35) Zhao, L.; Hou, H.; Zhou, Y. Y.; Xue, N. D.; Li, H. Y.; Li, F. S. Distribution and ecological risk of polychlorinated biphenyls and organochlorine pesticides in surficial sediments from Haihe River and Haihe Estuary Area, China. Chemosphere 2010, 78, 1285−1293. (36) Yang, H. Y.; Xue, B.; Jin, L. X.; Zhou, S. S.; Liu, W. P. Polychlorinated biphenyls in surface sediments of Yueqing Bay, Xiangshan Bay, and Sanmen Bay in East China Sea. Chemosphere 2011, 83, 137−143. (37) Tang, L. L.; Tang, X. Y.; Zhu, Y. G.; Zheng, M. H.; Miao, Q. L. Contamination of polycyclic aromatic hydrocarbons (PAHs) in urban soils in Beijing, China. Environ. Int. 2005, 31, 822−828.

11436

dx.doi.org/10.1021/es502197b | Environ. Sci. Technol. 2014, 48, 11429−11436