Environ. Sci. Technol. 2010, 44, 2305–2308
Dechlorane Plus in Surficial Water and Sediment in a Northeastern Chinese River HONG QI,† LIYAN LIU,† H O N G L I A N G J I A , ‡ Y I - F A N L I , †,§ N A N - Q I R E N , * ,† H O N G Y O U , † XINYUAN SHI,† LILI FAN,† AND YONGSHENG DING| International Joint Research Center for Persistent Toxic Substances (IJRC-PTS), State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, China, IJRC-PTS, Dalian Maritime University, Dalian, China, Science and Technology Branch, Environment Canada, Toronto, Ontario, Canada, and IJRC-PTS, College of Ocean and Environmental Engineering, Shanghai Maritime University, Shanghai, China
Received September 7, 2009. Revised manuscript received February 23, 2010. Accepted February 26, 2010.
Surface water and sediment samples concurrently collected in Songhua River in northeastern China from May to October 2006 were analyzed for Dechlorane Plus (DP), a chlorinated flame retardant. Samples were obtained from three main areas: SHRRul (rural area of Songhua River), SHR-Hrb (the section of the river within the city of Harbin), and Hrb (urban waters of Harbin). The majority of SHR-Rul water samples (85%) and SHRHrb water samples (73%) and 33% of urban water samples (Hrb) were below the detection limit. The mean water DP concentration in Hrb (0.55 ( 0.81 ng L-1) was approximately 3 times greater than the levels measured in SHR-Hrb (0.17 ( 0.38 ng L-1) and more than 15 times greater than the levels measured in SHR-Rul (0.03 ( 0.07 ng L-1). DP detection rates in sediment samples were 50% (Hrb), 100% (SHR-Hrb), and 78% (SHR-Rul). The mean sediment DP concentration in SHRHrb (0.11 ( 0.05 ng g-1) was approximately three times greater than that in SHR-Rul (0.04 ( 0.05 ng g-1). These DP concentrations are likely attributable to local sources in urban areas rather than distant sources via long-range transport. The mean fractional abundance of the syn isomer of DP (fsyn) was 0.34 ( 0.10 in all water samples, a value indistinguishable from that of a commercial mixture (fsyn ) 0.35), indicating the source was local. The mean fsyn value of 0.23 ( 0.06 in all sediment samples suggested a stereoselective depletion of syn-DP relative to the anti-DP isomer in sediments. To our knowledge, this paper represents the first report of DP concentrations in Chinese water and sediments.
Introduction Over the past decade, the environmental occurrence of brominated flame retardants such as polybrominated diphenyl ethers (PBPEs) has been of primary interest to * Corresponding author e-mail:
[email protected]. † Harbin Institute of Technology. ‡ Dalian Maritime University. § Environment Canada. | Shanghai Maritime University. 10.1021/es9027106
2010 American Chemical Society
Published on Web 03/08/2010
environmental scientists. Dechlorane Plus (DP), manufactured for over 40 years (1) and used primarily in products such as cable coatings, plastic roofing materials, and hard connectors in computers and televisions (2, 3), is a chlorinated flame retardant (C18H12Cl12) that has been identified as an emerging environmental contaminant only since 2006 (4–7). New research has identified the need for further investigation after demonstrating the biomagnification of DP in Lake Winnipeg and Lake Ontario, Canada (4, 5). It was reported that DP was manufactured in Jiangsu Anpon Electrochemical Company in China since 2004 (http:// www.anpon.com/), and the production of DP in China is not clear. Monitoring of DP in China was first conducted at the International Joint Research Center for Persistent Toxic Substances (IJRC-PTS) by a nationally deployed network of passive air samplers (PASs) (7). Variables measured were ambient DP levels and isomeric composition. Mean DP concentrations in Chinese urban centers (15.6 pg m-3) exceeded those in rural areas (3.5 pg m-3) by a factor of approximately five. A strong correlation (R2 ) 0.57, p < 0.05) was also found between airborne DP concentration in 12 cities and their respective population sizes. It was suggested that DP in these environments probably originated from local sources (7). The objective of this study was to extend the DP study from air to include the two additional matrices of water and sediment. The Songhua River in the Heilongjiang Province in Northeast China is the largest tributary of the Heilong River and formed near the Heilongjiang-Jilin provincial border, where its two large tributaries, the Nen River and the Second Songhua River meet (Figure S1 of the Supporting Information). From this point, it travels east to pass the city of Harbin, capital of the Heilongjiang province. The combined length of the Songhua and Second Songhua Rivers ia approximately 1900 km (Figure S1 of the Supporting Information). In this study, we present DP levels in water and sediment of the Songhua River and additional urban water bodies in Harbin. Isomeric ratio profiles in water and sediment are also discussed.
Materials and Methods Sample Collection. Concurrent surface water and sediment sampling was carried out from May to October 2006. Fourteen surface water and 18 surface sediment samples were collected at 13 sites in the rural area along the river (SHR-Rul) (Figure S1 and Table S1 of the Supporting Information). For comparison, 20 water samples from 10 sites and 4 sediment samples from 2 sites were collected in the urban section of the Songhua River (SHR-Hrb) Furthermore, 14 water samples from 8 sites and 6 sediment samples from 6 sites were collected from urban waters in the City of Harbin (Hrb) (Figure S2 and Table 1 of the Supporting Information). Water samples (1 L for each) collected at sampling sites were placed directly into amber glass acetone-rinsed bottles and capped with Teflon-lined or solvent-washed aluminum foil-lined caps. Samples were stabilized with 100 mL dichloromethane (DCM) to prevent bacterial degradation and stored in darkness at 4 °C. Around 0.5 kg of surface sediment samples were collected using a sediment sampler and transferred to a Teflon-lined, capped glass jar and frozen (-20 °C) until extraction. All processes were carried out following the standard operating procedures (SOPs) of the National Laboratory for Environmental Testing (NLET), Environment Canada (6, 7). Sample Extraction and Analysis. Sediment and water samples were treated, extracted, and analyzed according to VOL. 44, NO. 7, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 1. Total DP concentration levels of water and sediment samples at rural sites in Songhua River (SHR-Rul). the SOPs of the NLET, Environment Canada (6, 7). Water samples were spiked with a recovery standard containing CB-65 and CB-55, which are routinely used in the extraction of compounds exhibiting properties similar to those of DP. Triple liquid/liquid extraction was carried out using DCM, and resulting extracts were cleaned and fractionated using silica chromatography. Packed columns were pre-rinsed with DCM, followed by hexane before eluting samples with a hexane-DCM mixture (1:1, v/v). Resulting fractions were blown down to approximately 1 mL under a gentle stream of ultra high purity (UHP) nitrogen and solvent-exchanged into isooctane. The internal standards CB-30 and CB-204 (Accustandard, New Haven, CT) were added to correct for volume difference. Wet sediment samples were thawed and mixed to homogeneity (4–6), after which 25 g portions were spiked with recovery surrogates CB-65 and CB-155. Soxhlet extraction with acetone and hexane (1:1, v/v) was carried out for 18 h at 80 °C with an hourly recycle rate approximating eight. Extracts were desiccated with sodium sulfate and concentrated to approximately 2 mL, and then cleaned on 10 g silica gel columns. Finally 15 mL of isooctane was added before concentrating to approximately 1 mL. Final volumes were adjusted to 1 mL with isooctane before the addition of internal standards PCB-30 and PCB-204. Analytical grade solutions of the syn-DP and anti-DP isomers were purchased from Wellington Laboratories (Guelph, ON, Canada) and diluted in high purity isooctane (>98%, Caledon, Inc., Caledon, ON, Canada). Details of sample analysis are presented elsewhere (10). Briefly, DP measurements were determined by gas chromatographymass spectrometry analysis under negative ion chemical ionization conditions, using methane on an Agilent 6890 gas chromatograph equipped with a split/splitless injector and an Agilent 5973N mass selective detector. A 60 m DB-5 ms column (J&W Scientific, Folsom, CA, 0.25 mm internal diameter and 0.25 µm film thickness) was operated with a helium carrier gas flow of 1 mL min-1. The instrument was operated in selected ion monitoring mode with the m/z 653.7 2306
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ion used for quantification and the m/z 649.7 and 651.7 ions used for confirmation. Quality Assurance/Quality Control. All samples were spiked with a surrogate recovery standard (CB-65 and CB155, Accustandard, Inc., New Haven, CT) prior to extraction, resulting in observed recovery rates between 71% and 94% for water samples and from 87% to 110% for sediment samples. No recovery correction was applied to the samples. The linear dynamic range of the GC-MS instrument was between 10 and 1200 pg on the column (R2 > 0.990) for both DP isomers. Instrument performance was monitored using quality control standards following every six samples. The ratio of the quantitation and confirmation ions in samples was within 15% of measured standard values in all cases. Values of three times the instrument detection limits (IDL) were used as the method detection limit (MDL), giving MDL values for the syn- and anti-DP isomers of 2.5 and 2 pg g-1 dw, respectively, for sediment and 50 and 40 pg L-1 for water. Neither syn-DP nor anti-DP was detected in any field and method blanks. Samples were not blank corrected. Syn- and Anti-DP Fractional Abundance. The stereoisomer ratios in water and sediment as measured in the environment can be described as the fractional abundance given by (6) fsyn ) [syn-DP]/([syn-DP] + [anti-DP])
(1)
When calculating fsyn values, five data points were excluded because only one isomer was detected.
Results and Discussion DP in Waters and Sediments in Rural Area. Total DP concentrations in water and sediment samples at 13 rural sites along the Songhua River are presented in Figure 1, with statistics given in Table 1. Mean DP concentrations in water and sediment samples, respectively, were 0.03 ng/L and 0.04 ng/g dw (dry weight) with respective ranges from below the detection limit (BDL) to 0.23 ng/L for water samples and BDL to 0.16 ng/g dw for sediment samples. Sverko et al. (6)
TABLE 1. Statistics of DP Data sampling sites
site number
sample number water
detection rate
fsyn
fsyn STDEV
mean
minimum
SHR-Rul SHR-Hrb Hrb total
13 10 8 31
14 20 14 48
0.14 0.20 0.57 0.29
NA 0.31 0.36 0.34
0.15 0.054 0.095
0.03 0.17 0.55 0.21
BDLa BDL BDL BDL
sediment SHR-Rul SHR-Hrb Hrb total a
13 2 6 21
18 4 6 28
maximum ng/L 0.23 1.20 2.40 2.40
STDEV
0.07 0.38 0.81 0.49
ng/g dw 0.78 1.00 0.50 0.75
0.21 0.29 0.26 0.23
0.042 0.032 0.081 0.057
0.04 0.11 0.06 0.05
BDL BDL BDL BDL
0.16 0.14 0.15 0.16
0.05 0.05 0.07 0.06
BDL: Below Detection Limit.
FIGURE 2. Total DP concentration levels of water and sediment samples in SHR-Hrb and Hrb sampling sites. reported DP concentrations in sediment ranges from 0.061 to 8.62 ng/g dw for Lakes Erie and from 2.23 to 586 ng/g dw for Lake Ontario. The DP concentration in Songhua River sediment therefore compares as 1 order of magnitude smaller than that in Lake Erie and 2 orders of magnitude smaller than that in Lake Ontario, which was possibly due to less local sources of DP in the Songhua River Basin than in the Great Lakes Basin. The highest water concentration of DP was found at site S3, possibly due to an unknown local source. With a Log Kow value of 9.3 for both syn- and anti-DP stereoisomers (8), DP stereoisomers in the river have a greater affinity for sediment than water, which is confirmed in our study. In SHR-Rul water samples, DP was detected in only 2 of 14 water samples (detection rate 14%) but in 14 out of 18 sediment samples (detection rate 78%) (Table 1). Greater DP concentrations in air have usually been associated with urban/industrial regions (7, 9), and this observation is also true for the current study. Site S5 in SHRRul, downstream of Harbin (Figure 1), demonstrated greater DP concentrations in sediment than those at Site S4 located upstream. The same pattern was true for sediment and water
samples from sites S11 and S12 located upstream and downstream, respectively, of the city Jiamusi (Figure 1). More detailed discussion on the DP concentrations in water and sediment in the urban section of the Songhua River and urban waters in Harbin, presented in the next section, reiterates this urban influence. Overall, no significant correlations were found for total DP concentrations between water and sediment or for DP concentrations in sediment and their total organic carbon (TOC). DP in Harbin Water and Sediment. Sampling sites are indicated in Figure 2 and Figure S2 of the Supporting Information. DP detection rates in surface water samples were 20% in the segment of the Songhua River within the City of Harbin (SHR-Hrb) and 57% in urban sites (Hrb). DP detection rates in sediment were 100% in SHR-Hrb and 50% in Hrb. Mean Hrb waterborne DP concentration was 0.55 ( 0.81 pg L-1, approximately three times greater than that of SHR-Hrb samples (0.17 ( 0.38 pg L-1) and 18 times greater than that of SHR-Rul samples (0.03 ( 0.07 pg L-1). These concentrations suggest that waterborne DP in and around VOL. 44, NO. 7, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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samples. The mean fsyn for the entire sediment data set was 0.23 ( 0.06, much lower than those in water samples and that of the technical DP profile. A statistical unpaired t-test was performed to analyze the similarity of fsyn between water and sediment samples, and the results showed that at a 99% level of significance (p < 0.01) the difference in fsyn between water and sediment samples is significant. Among the sediment samples, SHR-Rul samples exhibited a lower mean fsyn value (0.21 ( 0.04) than SHR-Hrb sediment samples (0.29 ( 0.03). The mean fsyn value for Hrb sediment was 0.26 ( 0.08, which is comparatively higher than that in SHR-Rul and lower than that in SHR-Hrb. As shown in Figure 3a, there were three Hrb sites where DP was detected (six sediment samples were collected at six Hrb sites), among which the sites H3 and H7 had fractional abundances of DP isomers fsyn > 0.30, close to that of the technical DP. As mentioned in the previous section, the sediments in many urban waters in Harbin have been cleaned almost annually by the municipality, so the values of fsyn in urban sediment samples at these two sites were closer to the value for the technical DP mixture. Site H8, however, had a much smaller fsyn (0.17). Sediment at this site probably has not been cleaned and has accumulated for many years. This is also confirmed by the fact that the DP at this site had the second highest concentration among all sampling sites (Figure 2).
Acknowledgments FIGURE 3. Fractional abundances (fsyn) of DP isomers for (a) sediment samples and (b) water samples at different sites. The red line in the figure is the mean fsyn (0.35) of a technical DP mixture (5). Harbin likely originates from local urban sources rather than distant sources via long-range transport. Mean DP concentration in SHR-Hrb sediment (0.11 ( 0.05 pg g-1) was almost three times greater than that measured in SHR-Rul sediment (0.04 ( 0.05 pg g-1), also indicating the urban source of DP in sediment, However, mean DP concentration in Hrb sediment (0.05 ( 0.07 pg g-1) was approximately equal to concentrations measured in SHR-Rul and was lower than those in SHR-Hrb. This observation does not compare well with the consideration that Hrb water is one of the primary sources of DP in the river. The reason for this is that DP concentrations found in urban sediment may not reflect longterm accumulation patterns because the sediment in many urban waters in the city of Harbin has been cleaned almost every year by the municipality during the dry seasons. Fractional Abundances of Dechlorane Plus Isomers. The fsyn values for water and sediment samples at different sites are shown in Figure 3, and the statistics are given in Table 1 for SHR-Rul, SHR-Hrb, and Hrb. Overall, no significant correlation was evident between fsyn values and total DP concentrations. It is interesting that the fsyn values are below 0.35 for all sediment samples, which is the mean fsyn value for technical DP mixture (5) but larger than 0.35 for most of the water samples. The mean fsyn (0.34 ( 0.10) for all water samples combined is very close to that of a technical DP mixture. Because only one isomer was detected at only one site for the SHR-Rul water samples, fsyn values for these sites are not available. The mean fsyn of SHR-Hrb water samples was 0.31 ( 0.15, slightly lower than that of Hrb (0.36 ( 0.05), but as indicated by the t test, this difference is not significant and is indistinguishable from that of the technical DP profile. A stereoselective depletion of the syn-DP effect relative to the anti-DP isomer, however, was obvious in the sediment
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We are grateful to financial support from the State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin, China (Project 2008DX01). Valuable comments from Yushan Su of Environment Canada and the three anonymous reviewers are highly appreciated, and Ed Sverko and Lindsay A. P. Smith from Environment Canada are thanked for editing the manuscript.
Supporting Information Available This material is available free of charge via the Internet at http://pubs.acs.org.
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