Environ Sci Pollut Res DOI 10.1007/s11356-014-2823-x
RESEARCH ARTICLE
Dechlorane Plus in surface soil of North China: levels, isomer profiles, and spatial distribution Jin Ma & Xinghua Qiu & Di Liu & Yifan Zhao & Qiaoyun Yang & Di Fang
Received: 7 November 2013 / Accepted: 21 March 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Eighty-seven soil samples collected from North China were analyzed for Dechlorane Plus (DP). The concentrations of DP ranged from not detectable (ND) to 12.21 ng/g with a mean of 0.55 ng/g. The mean concentrations of total DP and syn-DP in four regions of North China were in the following order: Jingjin (Beijing and Tianjin)>Shandong> Shanxi>Hebei, while the mean concentrations of anti-DP in the four regions were in a different order: Shandong>Jingjin> Shanxi>Hebei. The mean fsyn values for Jingjin (0.27), Hebei (0.24), and Shanxi (0.24) were close to 0.25, while the mean fsyn value for Shandong (0.31) was closer to 0.35. In addition, the fsyn value for Shandong was significantly higher (P95 %) were purchased from Wellington Laboratories (Guelph, Ontario, Canada). BDE118 was obtained from AccuStandard (New Haven, CT, USA). 13Clabeled PCB-138 was purchased from Cambridge Isotope
Laboratories (Andover, MA, USA). All solvents used for the extraction and cleanup procedures were residue-analysis grade or equivalent and obtained from either Fisher Scientific (Fair Lawn, NJ, USA) or Tedia (Fairfield, OH, USA). Sample extraction and analysis An accelerated solvent extractor (ASE300; Dionex, Sunnyvale, CA, USA) was used for soil sample extraction. About 20-g soil samples were mixed with a piece of copper and spiked with 50 μL BDE118 as surrogate standards and then transferred to stainless steel extraction cells. The extraction cells were pre-cleaned with n-hexane, and a piece of cellulose filter paper was thereafter placed on the bottom of the cell. The extraction conditions were as follows: the solvent was 100 mL n-hexane/acetone (1:1, v/v), the temperature was 100 °C, and the pressure was 1,500 psi (10.3 MPa) with 5 min for heating, 5 min in the static state, and three cycles for extraction. Finally, the extraction cells were flushed with solvent (60 % of the cell volume) and purged with nitrogen (120 s). The extracts were collected in 250-mL bottles with Teflon septa and then concentrated by rotary vacuum evaporation and solvent-exchanged to hexane. The concentrated extracts were cleaned up using mixed column chromatography (25 cm× 1 cm i.d.). A column fitted with a Teflon stopcock was packed from the bottom with glass wool, 3 % deactivated aluminum oxide (6 cm), 25 % sodium hydroxide silica (5 cm), 3 % deactivated neutral silica gel (2 cm), and 50 % acidic silica (8 cm), followed by anhydrous sodium sulfate (2 cm). The extracts were eluted with 30 mL of hexane (discarded) and 60 mL of n-hexane/dichloromethane (1:1, V/V). The eluents were vacuum-evaporated and concentrated to 0.1 mL under a gentle stream of nitrogen. After concentration, 13C-PCB138 was added as internal standards for gas chromatography/mass spectrometry (GC/MS) analysis. We analyzed the target compounds by GC/MS (7890A/ 5975C; Agilent Technologies, Santa Clara, CA, USA) with an electron capture negative ionization (ECNI) ion source. Highpurity helium was used as carrier gas at a constant flow of 1.5 mL/min. The separation was performed on fused silica capillary columns (Rtx-5MS, 15 m in length; 250 μm i.d.; 0.10 μm in film thickness; J&W Scientific, Folsom, CA, USA). The GC oven temperature programs were as follows: hold at 90 °C for 1 min, 20 °C/min to 200 °C, 5 °C/min to 300 °C, and then a hold for 3.5 min. The injector and detector temperatures were set at 280 °C. Then, 1 μL of each sample was injected in the splitless mode. The compounds were monitored at 653.8 and 651.8m/z. Quality assurance/quality control Several quality control criteria were used to ensure the correct identification and quantification of DP. First, the GC retention
Environ Sci Pollut Res Fig. 1 Map of sampling sites in North China
times matched those of the standard compounds within ±0.1 min. Second, the signal-to-noise ratio was higher than 5:1. Third, the isotopic ratios of all pairs were within ±15 % of the theoretical values. The mean recoveries of the surrogate ranged from 52 to 122.6 %. All results were expressed on a dry weight basis. The reported data were not validated by the surrogate
recoveries. The instrument detection limits (IDL) for syn-DP and anti-DP were 0.2 and 0.1 pg/g, respectively. Data calculation Statistical analyses were conducted using SPSS ver. 18.0 (SPSS Inc., Chicago, IL, USA) GS+ ver.9 and ArcGIS ver.9.
Table 1 Concentrations of syn-DP, anti-DP and total DP in soil samples (ng/g dry weight) Region
Number
Jingjin
7
Hebei
29
Shanxi
24
Shandong
27
Total
87
Mean±SD Range FD (%) Mean±SD Range FD (%) Mean±SD Range FD (%) Mean±SD Range FD (%) Mean±SD Range FD (%)
ND not detected, FD (%) frequencies of detection (%)
syn-DP
anti-DP
Total DP
0.45±1.10 0.0007–2.95 100 0.02±0.02 ND–0.10 86.21 0.06±0.26 ND–1.28 87.5 0.30±0.83 ND–3.76 92.59 0.15±0.57 ND–3.76 89.66
0.64±1.51 0.004–4.05 100 0.08±0.12 ND–0.55 93.1 0.42±1.35 0.0003–5.84 100 0.66±1.83 0.0003–8.45 100 0.40±1.31 ND–8.45 97.7
1.10±2.61 0.01–7.0 100 0.10±0.14 ND–0.66 93.1 0.48±1.49 0.0003–5.84 100 0.96±2.66 0.0003–12.21 100 0.55±1.83 ND–12.21 97.7
Environ Sci Pollut Res
Geostatistical analyst extensions were employed for semivariogram fitting and ordinary kriging interpolation.
a
10
Syn-DP
Descriptive statistics of the DP concentrations in the 87 soil samples were shown in Table 1 and Fig. 2. Total DP and antiDP were detected in 85 of the 87 soil samples, while syn-DP was detected in 78 of the 87 samples. The frequency of detection (FD) of syn-DP (89.66 %) was slightly lower than that of anti-DP (97.7 %). Total DP concentrations ranged from not detected (ND, Hebei, while the mean concentrations of anti-DP in the four regions were in a different order: Shandong>Jingjin>Shanxi>Hebei. The highest DP concentration in Jingjin (7 ng/g dry weight) was found at an e-waste recycling site in the town of Ziya, located south of Tianjin City. DP levels fell dramatically with increasing distance away from the recycling site, suggesting that e-waste recycling activities are major point sources of DP emissions in this region. This was in agreement with a previous study conducted at another e-waste recycling site in Qingyuan, located in the south of China (Yu et al. 2010). In addition, the highest DP concentration in this study (12.21 ng/g) was identified in Shandong where no
.1
.01
.001
.0001 Jingjin
b
Hebei
Shanxi
Shandong
Hebei
Shanxi
Shandong
Hebei
Shanxi
Shandong
100
anti-DP 10
Concentration (ng/g)
Concentrations of DP in soil samples
1 .1 .01 .001 .0001 Jingjin
c
100
DP 10
Concentration (ng/g)
Results and discussion
Concentration (ng/g)
1
1 .1 .01 .001 .0001 Jingjin
Fig. 2 Concentrations of syn-DP (a), anti-DP (b), and DP (c) in soil samples from North China The black horizontal line represents the median, and the red horizontal line represents the mean. The box represents the 25th–75th percentiles, and the whiskers represent the 10th–90th percentiles
known e-waste recycling activity occurs. Further research is needed to confirm the exact source of DP in Shandong.
Environ Sci Pollut Res Fig. 3 The fsyn values of all samples
Fractional abundances of DP isomers Technical DP consists of two conformational isomers: syn (Ushaped) and anti (chair-shaped) (Sverko et al. 2011). The stereoisomer ratios in soil can be described as the fractional abundance given by the following (Sverko et al. 2008): f syn ¼ ½syn−DP=ð½syn−DP þ ½anti−DPÞ:
When calculating fsyn values, seven data points, where only one isomer was detected, were excluded. The fsyn values for soil samples from different sites were shown in Fig. 3. As shown in Fig. 3, fsyn values varied greatly between the different regions of North China (range, 0.11~0.51). The mean fsyn value of Jingjin, Hebei, Shanxi, and Shandong was 0.27, 0.24, 0.24, and 0.31, respectively. The fsyn value of technical products from OxyChem has been reported to be 0.25 by Qiu and Hites (2008) and 0.35 by Tomy et al. (2007). Note that the mean fsyn values in Jingjin, Hebei, and Shanxi were close to 0.25, while the value in Shandong was closer to 0.35. In addition, fsyn values in Shandong were significantly higher (P
RESEARCH ARTICLE
Dechlorane Plus in surface soil of North China: levels, isomer profiles, and spatial distribution Jin Ma & Xinghua Qiu & Di Liu & Yifan Zhao & Qiaoyun Yang & Di Fang
Received: 7 November 2013 / Accepted: 21 March 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Eighty-seven soil samples collected from North China were analyzed for Dechlorane Plus (DP). The concentrations of DP ranged from not detectable (ND) to 12.21 ng/g with a mean of 0.55 ng/g. The mean concentrations of total DP and syn-DP in four regions of North China were in the following order: Jingjin (Beijing and Tianjin)>Shandong> Shanxi>Hebei, while the mean concentrations of anti-DP in the four regions were in a different order: Shandong>Jingjin> Shanxi>Hebei. The mean fsyn values for Jingjin (0.27), Hebei (0.24), and Shanxi (0.24) were close to 0.25, while the mean fsyn value for Shandong (0.31) was closer to 0.35. In addition, the fsyn value for Shandong was significantly higher (P95 %) were purchased from Wellington Laboratories (Guelph, Ontario, Canada). BDE118 was obtained from AccuStandard (New Haven, CT, USA). 13Clabeled PCB-138 was purchased from Cambridge Isotope
Laboratories (Andover, MA, USA). All solvents used for the extraction and cleanup procedures were residue-analysis grade or equivalent and obtained from either Fisher Scientific (Fair Lawn, NJ, USA) or Tedia (Fairfield, OH, USA). Sample extraction and analysis An accelerated solvent extractor (ASE300; Dionex, Sunnyvale, CA, USA) was used for soil sample extraction. About 20-g soil samples were mixed with a piece of copper and spiked with 50 μL BDE118 as surrogate standards and then transferred to stainless steel extraction cells. The extraction cells were pre-cleaned with n-hexane, and a piece of cellulose filter paper was thereafter placed on the bottom of the cell. The extraction conditions were as follows: the solvent was 100 mL n-hexane/acetone (1:1, v/v), the temperature was 100 °C, and the pressure was 1,500 psi (10.3 MPa) with 5 min for heating, 5 min in the static state, and three cycles for extraction. Finally, the extraction cells were flushed with solvent (60 % of the cell volume) and purged with nitrogen (120 s). The extracts were collected in 250-mL bottles with Teflon septa and then concentrated by rotary vacuum evaporation and solvent-exchanged to hexane. The concentrated extracts were cleaned up using mixed column chromatography (25 cm× 1 cm i.d.). A column fitted with a Teflon stopcock was packed from the bottom with glass wool, 3 % deactivated aluminum oxide (6 cm), 25 % sodium hydroxide silica (5 cm), 3 % deactivated neutral silica gel (2 cm), and 50 % acidic silica (8 cm), followed by anhydrous sodium sulfate (2 cm). The extracts were eluted with 30 mL of hexane (discarded) and 60 mL of n-hexane/dichloromethane (1:1, V/V). The eluents were vacuum-evaporated and concentrated to 0.1 mL under a gentle stream of nitrogen. After concentration, 13C-PCB138 was added as internal standards for gas chromatography/mass spectrometry (GC/MS) analysis. We analyzed the target compounds by GC/MS (7890A/ 5975C; Agilent Technologies, Santa Clara, CA, USA) with an electron capture negative ionization (ECNI) ion source. Highpurity helium was used as carrier gas at a constant flow of 1.5 mL/min. The separation was performed on fused silica capillary columns (Rtx-5MS, 15 m in length; 250 μm i.d.; 0.10 μm in film thickness; J&W Scientific, Folsom, CA, USA). The GC oven temperature programs were as follows: hold at 90 °C for 1 min, 20 °C/min to 200 °C, 5 °C/min to 300 °C, and then a hold for 3.5 min. The injector and detector temperatures were set at 280 °C. Then, 1 μL of each sample was injected in the splitless mode. The compounds were monitored at 653.8 and 651.8m/z. Quality assurance/quality control Several quality control criteria were used to ensure the correct identification and quantification of DP. First, the GC retention
Environ Sci Pollut Res Fig. 1 Map of sampling sites in North China
times matched those of the standard compounds within ±0.1 min. Second, the signal-to-noise ratio was higher than 5:1. Third, the isotopic ratios of all pairs were within ±15 % of the theoretical values. The mean recoveries of the surrogate ranged from 52 to 122.6 %. All results were expressed on a dry weight basis. The reported data were not validated by the surrogate
recoveries. The instrument detection limits (IDL) for syn-DP and anti-DP were 0.2 and 0.1 pg/g, respectively. Data calculation Statistical analyses were conducted using SPSS ver. 18.0 (SPSS Inc., Chicago, IL, USA) GS+ ver.9 and ArcGIS ver.9.
Table 1 Concentrations of syn-DP, anti-DP and total DP in soil samples (ng/g dry weight) Region
Number
Jingjin
7
Hebei
29
Shanxi
24
Shandong
27
Total
87
Mean±SD Range FD (%) Mean±SD Range FD (%) Mean±SD Range FD (%) Mean±SD Range FD (%) Mean±SD Range FD (%)
ND not detected, FD (%) frequencies of detection (%)
syn-DP
anti-DP
Total DP
0.45±1.10 0.0007–2.95 100 0.02±0.02 ND–0.10 86.21 0.06±0.26 ND–1.28 87.5 0.30±0.83 ND–3.76 92.59 0.15±0.57 ND–3.76 89.66
0.64±1.51 0.004–4.05 100 0.08±0.12 ND–0.55 93.1 0.42±1.35 0.0003–5.84 100 0.66±1.83 0.0003–8.45 100 0.40±1.31 ND–8.45 97.7
1.10±2.61 0.01–7.0 100 0.10±0.14 ND–0.66 93.1 0.48±1.49 0.0003–5.84 100 0.96±2.66 0.0003–12.21 100 0.55±1.83 ND–12.21 97.7
Environ Sci Pollut Res
Geostatistical analyst extensions were employed for semivariogram fitting and ordinary kriging interpolation.
a
10
Syn-DP
Descriptive statistics of the DP concentrations in the 87 soil samples were shown in Table 1 and Fig. 2. Total DP and antiDP were detected in 85 of the 87 soil samples, while syn-DP was detected in 78 of the 87 samples. The frequency of detection (FD) of syn-DP (89.66 %) was slightly lower than that of anti-DP (97.7 %). Total DP concentrations ranged from not detected (ND, Hebei, while the mean concentrations of anti-DP in the four regions were in a different order: Shandong>Jingjin>Shanxi>Hebei. The highest DP concentration in Jingjin (7 ng/g dry weight) was found at an e-waste recycling site in the town of Ziya, located south of Tianjin City. DP levels fell dramatically with increasing distance away from the recycling site, suggesting that e-waste recycling activities are major point sources of DP emissions in this region. This was in agreement with a previous study conducted at another e-waste recycling site in Qingyuan, located in the south of China (Yu et al. 2010). In addition, the highest DP concentration in this study (12.21 ng/g) was identified in Shandong where no
.1
.01
.001
.0001 Jingjin
b
Hebei
Shanxi
Shandong
Hebei
Shanxi
Shandong
Hebei
Shanxi
Shandong
100
anti-DP 10
Concentration (ng/g)
Concentrations of DP in soil samples
1 .1 .01 .001 .0001 Jingjin
c
100
DP 10
Concentration (ng/g)
Results and discussion
Concentration (ng/g)
1
1 .1 .01 .001 .0001 Jingjin
Fig. 2 Concentrations of syn-DP (a), anti-DP (b), and DP (c) in soil samples from North China The black horizontal line represents the median, and the red horizontal line represents the mean. The box represents the 25th–75th percentiles, and the whiskers represent the 10th–90th percentiles
known e-waste recycling activity occurs. Further research is needed to confirm the exact source of DP in Shandong.
Environ Sci Pollut Res Fig. 3 The fsyn values of all samples
Fractional abundances of DP isomers Technical DP consists of two conformational isomers: syn (Ushaped) and anti (chair-shaped) (Sverko et al. 2011). The stereoisomer ratios in soil can be described as the fractional abundance given by the following (Sverko et al. 2008): f syn ¼ ½syn−DP=ð½syn−DP þ ½anti−DPÞ:
When calculating fsyn values, seven data points, where only one isomer was detected, were excluded. The fsyn values for soil samples from different sites were shown in Fig. 3. As shown in Fig. 3, fsyn values varied greatly between the different regions of North China (range, 0.11~0.51). The mean fsyn value of Jingjin, Hebei, Shanxi, and Shandong was 0.27, 0.24, 0.24, and 0.31, respectively. The fsyn value of technical products from OxyChem has been reported to be 0.25 by Qiu and Hites (2008) and 0.35 by Tomy et al. (2007). Note that the mean fsyn values in Jingjin, Hebei, and Shanxi were close to 0.25, while the value in Shandong was closer to 0.35. In addition, fsyn values in Shandong were significantly higher (P
