Bull Environ Contam Toxicol (2014) 93:752–757 DOI 10.1007/s00128-014-1365-8

Levels and Spatial Distribution of Polybrominated Diphenyl Ethers (PBDEs) in Surface Soil from the Yangtze River Delta, China Shuangxin Shi • Lifei Zhang • Wenlong Yang Li Zhou • Liang Dong • Yeru Huang



Received: 31 March 2014 / Accepted: 16 August 2014 / Published online: 29 August 2014 Ó Springer Science+Business Media New York 2014

Abstract Surface soil samples were collected from Suzhou, Wuxi and Nantong in the Yangtze River Delta (YRD), China. Eight BDE congeners (BDE-28, 47, 99, 100, 153, 154, 183 and 209) were measured to determine the levels and compositional profiles in the samples. The concentrations of R7PBDEs and BDE-209 ranged from 0.04 to 2.23 lg/kg dw and 1.48 to 41.7 lg/kg dw in the samples, respectively. BDE-209 was the predominant congener (contributing to 69.2 %–99.8 % of R8PBDEs) in all samples. It was found that small towns and rural economic development zones in this region had also become sources of polybrominated diphenyl ethers pollutants to surrounding areas. Investigation of the pattern of BDE congener profiles showed that deca- and octa- technical formulations as emission sources were identified in the samples collected from the YRD. Keywords Surface soil  Polybrominated diphenyl ethers  Spatial distribution  The YRD Polybrominated diphenyl ethers (PBDEs) are semi-volatile organic compounds and ubiquitous environmental pollutants (de Wit 2002). Studies have shown certain PBDEs possess the properties of persistent organic pollutants (POPs) (de Wit 2002). Due to various health and ecological risks posed by PBDEs, two major commercial PBDE products (penta-BDE and octa-BDE) were listed as POPs

under the Stockholm Convention and have been banned in many countries. Polybrominated diphenyl ethers are ‘additive’ flame retardants and may volatilize into ambient air from products to which they were applied. Soils can receive inputs of PBDEs via atmospheric deposition and plays an important role in the distribution and biogeochemical cycling of PBDEs, as they are a major reservoir and sink for PBDEs (Gevao et al. 2011). A few studies have surveyed PBDEs contamination in soils. However, the focus of these studies was on existing heavily polluted areas, such as industrial and electronic waste polluted areas. To date, there has not been any comprehensive survey for PBDEs concentration in soils from city cluster regions in China. Suzhou, Wuxi and Nantong are the emerging industrial cities in the YRD. Except for Shanghai, they are the most urbanized area in this region. This region covers an area of 21,800 km2, but the urban system in this region is made up of eleven cities, including eight secondary cities, and has a residential population of 18.4 million (Gu et al. 2011). At present, this region is facing serious PBDEs pollution problems, due to the rapid growth of industrial production, energy consumption, construction activities and traffic density. The objective of this study was to determine levels and spatial distributions of soil PBDEs in this region.

Materials and Methods S. Shi (&)  L. Zhang  W. Yang  L. Zhou  L. Dong  Y. Huang Dioxin Pollution Control Key Laboratory of State Environmental Protection Administration, National Research Center for Environmental Analysis and Measurements, Beijing 100029, China e-mail: [email protected]

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Surface soil samples (0–5 cm) were collected from 33 sites across the study area (120.2°–121.0°E, 29.9°–32.1°N; Fig. 1). Soil samples sites were divided into three area groups, urban, urban–rural transition and rural area. All sample sites were chosen to be away from potential sources

Bull Environ Contam Toxicol (2014) 93:752–757

753

Fig. 1 Map of the study area and sampling sites in the Yangtze River Delta, China

([50 m from busy roads or manufacturing companies) to ensure that these sites were not influenced by anthropogenic activities pointedly. All samples were collected from barren land using a stainless steel spade. Each sample was a composite of five subsamples collected from different locations, which were within 10 m from each other. About 200 g of each subsample was bulked together to form one sample. Samples were wrapped in aluminum foil, sealed in polyethylene bags and stored in a portable refrigerator, and then transported to the laboratory. The air–dried samples were ground and sieved through a 0.15 mm sieve, and kept at –20°C until extraction. The mixed standards of eight native PBDEs and 13C12PCB209 were obtained from Accustandard Inc. (USA). The mixed standards of eight 13C12-labeled PBDEs were obtained from the Cambridge Isotope Laboratories, Inc. (USA). All solvents used were of pesticide grade (Tedia, USA). Anhydrous sodium sulfate (Na2SO4), sulfuric acid (H2SO4) and sodium hydroxide (NaOH) were guaranteed reagent (Beijing Chemical Factory, China). Sodium sulfate was baked at 450°C and stored in a sealed container. Silica gel was twice washed with n-hexane in a glass flask and activated overnight at 160°C. An aliquot of 10.0 g of sieved fractions of soil was added to the extraction cell of an ASE system (ASE300, Dionex, USA). Extraction was performed with the same instrumental settings described by our previously established study (Shi et al. 2013). Prior to extraction, all samples were spiked with surrogate standard to monitor the analytical recovery efficiency. The extracts of samples were cleaned by the same method we established (Shi et al.

2013). An internal standard (13C12-PCB-209) was added to the final extract prior to the instrumental analysis. Extracts were analyzed using Shimadzu GCMS-2010 Ultra operated under electron ionization and equipped with a ZB-5HT MS column (15 m 9 0.25 mm 9 0.1 lm). The ion source, quadrupole and transfer line temperatures were set at 260, 150 and 280°C, respectively. One micro liter extract was injected. Pulsed-splitless injection (180 kPa, 1 min) was used to minimize PBDEs degradation in the injector liner. The initial oven temperature was 60°C for 1 min and raised at 30°C/min to 220°C, then raised at 10°C/min to 320°C and held for 5 min. The surrogate recoveries in all samples ranged from 85 % to 119 % (50 % to 148 % for 13C12-BDE209). Concentrations of BDE congeners in all samples were corrected by recoveries of 13C12- labeled BDEs. Procedural blanks were analyzed and no target compounds were detected except BDE-209. The limit of the detection of the method (MDLs) for 7 BDE congeners were determined by replicating the analysis of cleaned samples that were spiked with known amount PBDEs (2.0 ng), and taking three folds of the SD as MDLs. The MDLs of BDE-209 was determined by replicating the analysis of procedural blank (n = 6), taking three folds of the SD as MDLs. MDLs for seven BDE congeners ranged from 0.03 to 0.06 lg/kg and 0.2 lg/kg for BDE-209. In the present study, the concentrations of BDE-209 in most samples were corrected by subtracting mean value of blank (0.47 lg/kg). Four samples with low BDE209 concentrations (1.48–1.74 lg/kg) approached the blank value. Due to the blank value [33 % that found in these samples, these data need not to be

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754

ND \ the method detection limit

Fig. 2 Concentrations of RPBDEs in soils from the YRD and other regions worldwide. Error bars correspond to maximum and minimum, boxes correspond to average value

BDE-28

BDE-47

BDE-100

BDE-99

BDE-154

BDE-153

BDE-183

BDE-209

Detection (%)

93.9

93.9

51.5

90.9

66.7

81.8

84.8

100

Mean

0.041

0.113

0.052

0.107

0.049

0.086

0.094

9.48

Median

0.019

0.039

0.011

0.037

0.026

0.067

0.073

5.41

Maximum

0.168

0.51

0.392

0.761

0.292

0.411

0.343

41.7

Minimum

ND

ND

ND

ND

ND

ND

ND

1.48

SD

0.048

0.139

0.093

0.155

0.065

0.087

0.085

10.2

70

Levels of PBDEs in soils µg/kg

Table 1 Descriptive data of PBDEs in the soil samples from the YRD (lg/kg dw)

Bull Environ Contam Toxicol (2014) 93:752–757

60 50 40 30 20 10 0

the Pearl River Delta

the Yangtze River Delta,

corrected. All concentrations reported in the text are presented in lg/kg dry weight.

Results and Discussion Descriptive statistics for the content of PBDEs in surface soil samples are summarized in Table 1. The detection frequency for 8 BDE congeners was between 51.5 % and 100 % in the soil samples. The high detection frequency may suggest that these compounds have become ubiquitous in soil environments. The detection frequency in the soil samples followed the order of BDE-209 [ 47 = 28 [ 183 [ 99 [ 153 [ 154 [ 100. The concentrations of R8PBDEs in the soil samples from the YRD ranged from 1.05 to 43.2 lg/kg (10.0 lg/kg as mean). The results from this study were compared with PBDEs observed in soils from other regions (Fig. 2). It was found that the PBDEs concentrations in soils from the YRD were higher than those in most regions (Muresan et al. 2010; Schuster et al. 2011; Meng et al. 2011; Chen et al. 2012). Our data were only lower than those in the Pearl River Delta, where significantly higher PBDEs concentrations were detected in soil samples from an e-waste recycling site (Zou et al. 2007). However, when compared to the R7PBDEs (the lighter brominated PBDEs) levels in soils from other regions, the concentrations of the R7PBDEs in the soil samples (0.04–2.23 lg/kg) were at the

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the Paris region

the United Kingdom

the Loess Plateau

the Yellow River Delta

Norway

same levels or lower than those in soils that reported in UK (0.1–3.66 lg/kg, Schuster et al. 2011), Paris (0.2–43.9 lg/ kg, Muresan et al. 2010), Norway (0.01–1.58 lg/kg, Schuster et al. 2011), and the Pearl River Delta (0.13–3.81 lg/kg, Zou et al. 2007). This observation indicated that the serious PBDEs contaminant in this region was mainly caused by the highly brominated PBDEs (BDE209), rather than the lighter brominated ones. In the present study, 13 sample sites were selected from urban areas. The concentrations of R8PBDEs in urban samples ranged from 3.95 to 43.2 lg/kg (15.9 lg/kg as mean), which were higher than those in most cities worldwide, and comparable to those in Kuwait (Fig. 3) (Wang et al. 2009; Chen et al. 2013; Muresan et al. 2010; Harrad and Hunter 2006; Li et al. 2008; Gevao et al. 2011; Thorenz et al. 2010). However, the levels of PBDEs in urban soils were lower than those in the industrial area from 7 cities, south China (Gao et al. 2011). This is not surprising, since the dominant industries of these cities are telecommunications, electronic and electrical equipment, and building and decoration materials. These industries could contribute significant PBDEs to the environment (Gao et al. 2011). In addition, it was also found that the data of R7PBDEs in the present study felt within the ranges and remained at relatively low levels in urban soils from different countries. BDE-209 was the major BDE congener, accounting for over 90.9 % (69.3 %–98.9 %) of R8PBDEs in the soil

Levels of PBDEs in urban soils µg/kg

Bull Environ Contam Toxicol (2014) 93:752–757

s

itie

7c

755

90 80 70 60 50 40 30 20 10 0

,s

a.

hin

hC out

Ku

it

D

wa

Ku

it, wa

ie

Cit

he

ft so

ina

YR

Sh

an

i gha

ina

nce

Ch

aris

P

Fra

Tai

n yua

Ch

Bi

,UK

ham

ng rmi

H

ina

,Ch

in arb

ia

vak

Slo

a, lav

tis

Bra

Fig. 3 Concentrations of RPBDEs in urban soils from the YRD and other cities worldwide. Error bars correspond to maximum and minimum, boxes correspond to average value

samples. Levels of BDE-209 in all samples were approximately 1–2 orders of magnitude higher than R7PBDEs. It was reported that BDE-209 is the main congener in two Deca-formulations, and BDE-209 could be emitted to the environment during production, use and disposal of BDE209-containing products (La Guardia et al. 2006; de Wit 2002). The results were consistent with that reported in other studies that the dominant PBDE mixture production and usage in the YRD is the commercial deca-BDE mixture (Duan et al. 2010; Qiu et al. 2010). In addition, BDE209 could also form or not be completely destroyed in various combustion processes (Wang et al. 2011). Incinerators, power plants, metallurgical processes and vehicles were recently identified as BDE-209 emission sources (Wang et al. 2011). Since1991, the investigated region is growing into a major production center for machinery, metallurgy, chemical, electronics, textiles and telecommunication equipment in east China (Gu et al. 2011). The annual emission of BDE-209 is very high, which could contribute a significant amount of BDE-209 stored in the soil environment. Consequently, BDE-209 pollution in soils should attract more attention in ecological risks. The compositional patterns of the soil samples from each city and the YRD were compared with the commercial PBDEs product. Six samples with very low concentrations of PBDEs were not used in the data processing, since some BDE congeners were not detected from them. The results indicated that the compositional patterns of the soil samples, both in each city and in the YRD, were distinct from those of penta-BDE products (Fig. 4). In particular, relatively higher proportions of BDE-153 were found in all samples than in Bromkal 70-5DE, DE-71 (Fig. 4). Previous research reported that BDE-153 could be from octa-BDE products, and the percentages of BDE-183 and BDE-153 were 42 % and 8.7 % (La Guardia et al.

2006). In the present study, a relatively good correlation (Pearson correlation coefficients r2 = 0.7749, [0.05) was found between BDE-153 and BDE-183 in all samples, indicating the likely additional input from octa-BDE sources in this region, while the quantity was much lower than that of deca-BDE. It was noted that BDE-47and 99 are major congeners of penta-BDE products (la Guardia et al. 2006), and the BDE47: BDE-99 ratios are 1.05 in Bromkal 70-5DE and 0.76 in DE-71. Due to BDE-99 having a higher KOA (octanol–air partition coefficients) relative to BDE-47, the ratio of BDE47 to BDE-99 usually falls below a value of 0.8 in soils (Harrad and Hunter 2006). However, the ratio in the present study was 1.12 with a range of 0.53–2.10 in the samples, which differed from those in penta-BDE product and background soils reported in other literature (Harrad and Hunter 2006; Duan et al. 2010). In addition, the proportions of BDE-28 and BDE-154 in the samples were higher than those in penta-BDE products. Such a difference might result from BDE congener fractionation changing by transport, mixing, degradation and depositional mechanisms in the environment. Another plausible explanation was the observed compositional profile might indicate that a ‘specific penta-BDE formulation’ has been produced or used in this region over a recent time period (Qiu et al. 2010). Hence, a more detailed investigation of penta-BDE sources in this region should be carried out in the future. It was found that the compositional patterns of the samples from Suzhou were similar to those from Wuxi, but distinct from what were found in the samples from Nantong. Notably, the concentrations and the proportions of BDE-183 of R7PBDEs in the samples from Nantong were higher than those in the samples from the other cities. The results indicated that significantly higher octa-BDE emissions occurred in Nantong. According to our site

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756

Bull Environ Contam Toxicol (2014) 93:752–757

The proportions of BDE congeners %

BDE-28

BDE-47

BDE-100

BDE-99

BDE-154

BDE-153

BDE-183

60 50 40 30 20 10 0 Suzhou

Wuxi

Nantong

the YRD

Bromkal 70 5DE

DE71

DE79

Fig. 4 Comparison of BDE congener profile between the PBDE technical mixture and soil samples from each city and the YRD

Fig. 5 Spatial distributions of PBDEs in surface soil from the Yangtze River Delta area. SZ Suzhou, WX Wuxi, NT Nantong, CS Changshu, ZJG Zhangjiagang, JY Jiangyin

investigations, the dominant industries in Nantong are petrochemical, energy, metallurgy and machinery, which could contribute significant octa-BDE to the environment (de Wit 2002; Wang et al. 2011). However, the dominant industries in Wuxi and Suzhou are electronic information, textile, new energy and bio-medicine, which could contribute more penta-BDE to the environment. The spatial distributions of the soil PBDEs in the urban, urban–rural transition and rural areas were established by analyzing data using the Kriging gridding method in Surfer 9.1 software. A contour map of PBDEs in units of lg/kg is shown in Fig. 5. The soil samples with higher PBDEs were observed in the urban sites, while most samples with lower concentration were observed in the rural or suburb sites, which normally are far away from factories and residential

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areas. This finding lends support to the hypothesis that urban area are sources of PBDEs pollutants to surrounding areas (Harrad and Hunter 2006; Qin et al. 2010). In fact, PBDEs emission sources are usually concentrated in urban areas, such as large-scale production, use and disposal of PBDEscontaining products, industrial combustion processes, transportation, and building activities. It was also found that PBDEs pollution in the YRD was not limited to the cities with high human population density, but also included small cities, such as Changshu, Kunshan, Zhangjiagang, Jiangyin etc. In fact, the urban system in this region is made up of many secondary cities mentioned above. Since 1991, the development of rural industries and the construction of small cities and towns are combined together, leading to emergence of rural economic development zones and many small

Bull Environ Contam Toxicol (2014) 93:752–757

cities group (Gu et al. 2011). Therefore, with the development of industrialization and urbanization process in this region, these small cities and rural economic development zones are facing serious PBDEs pollution problems, which should be of grave concern. However, it should be noted that the soil PBDEs levels in the urban area of Wuxi were lower, especially for 7 BDE congeners. There was no clear explanation can be that given at this time. One explanation was that there were no significant PBDEs contaminants in the samples from selected sites. For 7 BDE congeners, the more likely explanation was that lower brominated congeners emitted from urban area of Wuxi were transported in the atmosphere and deposited at downwind distance. Suzhou is bordered on the southeast by Wuxi, and the predominant wind direction in the study area is from the northwest (upwind) to the southeast (downwind). Hence, the higher concentrations of R7PBDEs were found in Suzhou than that in Wuxi. The phenomenon that the levels of lower brominated congeners in the downwind soil samples were higher than that in upwind soil samples happened in the city of Nantong, which demonstrated the ‘‘urban pulse’’ theory postulated by Harrad and Hunter (2006). Acknowledgments We are grateful for financial support from the National Basic Research Program of China (no. 2009CB42160X).

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Levels and spatial distribution of polybrominated diphenyl ethers (PBDEs) in surface soil from the Yangtze River Delta, China.

Surface soil samples were collected from Suzhou, Wuxi and Nantong in the Yangtze River Delta (YRD), China. Eight BDE congeners (BDE-28, 47, 99, 100, 1...
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