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Feb 3, 2010 - Abstract. Purposes Very few data for polybrominated diphenyl ethers. (PBDEs) were available in the Yangtze River Delta (YRD), one of the ...
Environ Sci Pollut Res (2010) 17:948–956 DOI 10.1007/s11356-010-0295-1

RESEARCH ARTICLE

Polybrominated diphenyl ethers in background surface soils from the Yangtze River Delta (YRD), China: occurrence, sources, and inventory Yan-Ping Duan & Xiang-Zhou Meng & Chao Yang & Zhao-Yu Pan & Ling Chen & Ran Yu & Feng-Ting Li

Received: 22 September 2009 / Accepted: 2 January 2010 / Published online: 3 February 2010 # Springer-Verlag 2010

Abstract Purposes Very few data for polybrominated diphenyl ethers (PBDEs) were available in the Yangtze River Delta (YRD), one of the most developed and urbanized region in China. In this study, Chongming Island, located at the estuary of the Yangtze River, was selected as background area to investigate the occurrence, sources, and inventory of PBDEs. Methods Forty-two PBDE congeners were determined in surface soils from farmland, woodland, grassland, tideland, and road collected in Chongming Island. Results The mean concentrations of Σ26PBDE (not including BDE-209) and BDE-209 in soils were 0.76 and 12 ng/g dry weight, respectively. BDE-209 contributed more than 90% of the total of 27 frequently detected BDE congeners, followed by BDE-99 and BDE-47. Weak correlations were found between total organic carbon content and PBDE congeners concentrations in surface soils. PBDE levels varied with land use. Farmland and woodland soils contained higher Σ26PBDE concentrations. BDE-209 levels were the highest in road soils. The mass inventories of PBDEs in soils of Chongming Island were estimated at 3.1 and 310 kg for Σ26PBDEs and BDE-209, respectively. Conclusions The PBDE levels in Chongming Island were similar to those in European background soils, suggesting Responsible editor: Ake Bergman Electronic supplementary material The online version of this article (doi:10.1007/s11356-010-0295-1) contains supplementary material, which is available to authorized users. Y.-P. Duan : X.-Z. Meng (*) : C. Yang : Z.-Y. Pan : L. Chen : R. Yu : F.-T. Li State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China e-mail: [email protected]

minimum influence of pollutants from the YRD via air, and wastewater inputs or few PBDE products were used herein. From the standpoint of eco-inland, more studies are needed to explore the reasons of PBDE difference by land use and to assess people intake PBDEs via agriculture products consumption in this region. Keywords Shanghai . Analysis . Flame retardants

1 Introduction Polybrominated diphenyl ethers (PBDEs) are a group of additive flame retardants, widely used in a variety of consumer products, such as textiles, furniture, cars, computers, and other electronic equipment, that have caused considerable concerns recently with their increasing detectable frequency and levels in environmental media (Law et al. 2006) and human body (Hites 2004). Penta-BDE, octaBDE, and deca-BDE are the three major technical PBDE products. In 2001, the total global market demand for PBDEs was 67,390 metric tons with deca-, penta-, and octa-BDE constituting 83.3%, 11.1%, and 5.6% of the total, respectively (Law et al. 2006). Currently, the productions of penta-BDEs and octa-BDEs have been banned in the European Union (EU) and North America. Also, decaBDEs have also been banned in some countries from the EU and North America, for example, in Norway and the USA since April 2008 and December 2009, respectively. However, these products are still being used in China, and the domestic demand of brominated diphenyl ethers (including PBDEs) has increased at a rate of ∼8% per year (Mai et al. 2005). Furthermore, China has been the destination of electrical and electronic equipment (EEE) waste from developed countries with a percentage of over

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70%. Thus, PBDEs may be released into environment accompanying the recycling process of EEE, such as manual disassembly, acid washing, and open burning (Leung et al. 2007; Meng et al. 2008). In addition, more and more studies strongly support the argument that PBDEs possess similar physicochemical, bioaccumulative, and toxicological properties to legacy “persistent organic pollutants” (POPs; Yogui and Sericano 2009). As a result, tetra-BDEs and penta-BDEs in commercial penta-BDE and hexa-BDEs and hepta-BDEs in commercial octa-BDE were added into the list of POPs established by the United Nations Stockholm Convention in May 2009 to highlight more public concerns (UNEP 2009). Soil is an important reservoir for many POPs including PBDEs and also the major route of entry of POPs into agricultural and wildlife food chains (Mueller et al. 2006). As POPs are released or escape into the environment, the burden in soils globally is a complex function of the balance between inputs and losses. Hence, investigation of PBDEs in soils can provide useful information for further understanding of their environmental processes and fate. PBDEs were measured in many different environmental samples in the Pearl River Delta (PRD), China, including Fig. 1 Map of the study area and sampling sites

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water (Guan et al. 2007), air (Chen et al. 2006b), sediments (Mai et al. 2005), and biota (Meng et al. 2007), suggesting that China is suffering from PBDE pollution. However, very limited PBDE data were available in the Yangtze River Delta, one of the most developed regions in China (Chen et al. 2006a; Shen et al. 2006; Xian et al. 2008). Chongming Island, located at the midpoint of China’s north–south coastal line and lying on the estuary of the Yangtze River and the western coast of the Pacific Ocean (121°09′30″–121°54′00″ E, 31°27′00″–31°51′15″ N), is the third largest island in China and the world’s largest alluvial island with the total area of 1,267 km2 (Fig. 1a). As shown in Fig. 1b, the Yangtze River is divided into a south branch and a north branch, which surrounds the island along with the East China Sea and is the mainly freshwater source. The island is isolated from Shanghai City by the south branch of the Yangtze River (Fig. 1). Except for agriculture and tourism, no other industries exist on the island. Currently, the island has been planned as a world famous eco-island for future development. As a result, the air and wastewater inputs from the YRD maybe PBDE sources to Chongming Island. Therefore, the objectives of this study were to investigate levels and compositional patterns and to make a

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mass inventory of PBDEs in the surface soils from the Chongming Island, which will provide the scientific basis for eco-island construction of this region.

2 Materials and methods 2.1 Soil sampling Five soils types were classified based on soil functions in Chongming Island, China, including farmland, woodland, grassland, tideland, and road soils. In March 2009, several surface soil samples (0–20 cm depth) were taken randomly from each type of soil (Fig. 1; Table S1, “S” designates tables in the Supplemental Information here and thereafter). The handheld corer for sampling was cleaned before and after each sample collection using other vegetation from the site. The first two cores were discarded, whereas the following three cores (taken over an area of several square meters) were combined as one sample. The samples were wrapped in two layers of aluminum foil, sealed in plastic bag, and stored in a cool box with ice. Upon arrival in the laboratory, the samples were freeze-dried, mixed thoroughly, sieved to 100 mesh, and kept at −18°C until analysis. 2.2 Standard materials Forty-two PBDE congeners as targets were purchased from AccuStandards (New Haven, CT, USA), including three mono-BDEs (BDE-1, 2, and 3), seven di-BDEs (BDE-7, 8, 10, 11, 12, 13, and 15), eight tri-BDEs (BDE-17, 25, 28, 30, 32, 33, 35, and 37), six tetra-BDEs (BDE-47, 49, 66, 71, 75, and 77), seven penta-BDEs (BDE-85, 99, 100, 116, 118, 119, and 126), five hexa-BDEs (BDE-138, 153, 154, 155, and 166), four hepta-BDE (BDE-181, 183, 190, and 196), nona-BDE (BDE-206), and deca-BDE (BDE-209). BDE-50 and BDE-172 as surrogate standards were also purchased from AccuStandards. 2.3 Analytical procedure Detailed analytical procedure and instrumental analysis conditions are given elsewhere (Mai et al. 2005). Briefly, about 15 g soils samples were spiked with BDE-50 and BDE-172 and Soxhlet extracted with a mixture of acetone and hexane (1:1 in volume) for 48 h. Activated copper were added into samples prior to extraction to remove elemental sulfur. The extract was concentrated and purified further on a glass column packed with 3% water deactivated silica gel and basic alumina. Target PBDEs were eluted in the 50 mL fraction of 50% DCM in hexane (v/v), and the final extract volume was reduced to 200 μL under a gentle N2 stream.

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Extracts were analyzed with a Shimadzu Model 2010 GC-MS (Shimadzu, Japan) using negative chemical ionization in selected ion monitoring mode. A DB-5 (30 m× 0.25 mm i.d., 0.25 μm film thickness) capillary column (J&W Scientific, Folsom, CA, USA) was used for the determination of PBDE congeners except for BDE-196, 206, and 209. The column temperature was initiated at 110°C (held for 1 min) and increased to 180°C at 8°C/min (held for 1 min), 240°C at 2°C/min (held for 5 min), 280°C at 2°C/min (held for 25 min), and 290°C at 5°C/min (held for 15 min). For BDE-196, 206, and 209, a DB-5 (15 m×0.25 mm i.d., 0.1 μm film thickness) capillary column (J&W Scientific, Folsom, CA, USA) was employed. The oven temperature was initiated at 110°C (held for 5 min) and increased to 200°C at a rate of 20°C/min (held for 4.5 min) and 310°C at a rate of 10°C/min (held for 20 min). Ultrahigh purity helium was used as the carrier gas. The transfer line, ion source, and quadrupole temperatures were maintained at 280°C, 250°C, and 300°C, respectively. Quantification of PBDEs was performed using an external standard method. The limit of detection (LOD) for BDE-209 was 50 pg/g and 3 pg/g for other congeners based on dry weight, respectively. 2.4 Total organic carbon measurements Total organic carbon (TOC) was analyzed with the Shimadzu TOC-VCPN with solid sample module (SSM5000A; Shimadzu, Japan). The overall standard deviation of measurements was better than 3% (n=3). 2.5 Quality assurance/quality control For each batch of 12 soil samples, a procedural blank, a spiked blank, a matrix spiking sample (42 PBDE congeners spiked into sample), and a matrix spiking duplicate were processed. The recoveries of 42 PBDE congeners, BDE-50, and BDE-172 were 83.2±18.4%, 85.8±19.0%, and 87.2± 18.1%, respectively. Only low level of BDE-209, which was either lower or only slightly higher than the LOD, was found in procedural blanks and subtracted from the sample measurement. Reported concentrations were not surrogate recovery corrected. 2.6 Data analysis For samples with concentrations below the LOD, 1/2 LOD were used, and the nondetection were set to zero in the calculation and assessment thereafter. Data regarding TOC content versus PBDE concentration in soil samples were linearly regressed to determine if any significant correlation existed. The level of significance was set to 5% (α=0.05) throughout the present study. All statistical analyses were performed with SPSS software (Ver 13.0; SPSS, Chicago, IL, USA).

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3 Results and discussion 3.1 PBDE levels and distribution Among 42 target PBDE congeners, only those detected in at least 60% of the samples were quantified, including BDE-15, 17, 25, 28, 32, 33, 37, 47, 49, 66, 75, 77, 99, 100, 116, 118, 119, 126, 138, 153, 154, 166, 181, 183, 190, 196, and 209. Here, we defined Σ26PBDEs as the sum of all these congeners except for BDE-209. In addition, Σ7PBDEs was also defined as the sum of seven congeners in this study, including BDE-28, 47, 99, 100, 153, 154, and 183, to compare our results with other studies due to these compounds were routinely detected in soil samples worldwide. Table S1 listed the concentrations of each congener, Σ7PBDEs, and Σ26PBDEs (on a dry weight (dw) basis) in surface soils from Chongming Island, China. The mean Σ7PBDEs was 0.52 ng/g with a range from 0.008 to 1.9 ng/g. For Σ26PBDEs, the mean was 0.76 ng/g with a range from 0.16 to 2.3 ng/g. Clearly, the seven routinely detected compounds were predominated congeners in all samples except for BDE-209, accounting for about 68% of the total. For BDE-209, the concentration was much higher than Σ26PBDEs in our soil samples (mean 12 ng/g; range 0.08– 35 ng/g; Table S1). Possible reasons for the difference between BDE-209 and other congeners will be discussed in detail later. Comparisons with other studies were summarized in Table S2. Generally, the levels of Σ7PBDEs (mean 0.52 ng/g; range 0.008–1.9 ng/g) in the present study were much lower than those in surface soils from e-waste recycling site at Guiyu (0.441–2,768 ng/g; Leung et al. 2007; Wang et al. 2005), Taizhou (824.4–948.6 ng/g; Cai and Jiang 2006), Laizhou Bay (4.8–235.2 ng/g; Jin et al. 2008), Qingyuan (0.1–3,159 ng/g; Luo et al. 2009), and the PRD (1.93–19.5 ng/g; Zou et al. 2007). As for BDE-209, the concentration (mean 12 ng/g; range 0.08–35 ng/g) was much lower than those in soils from e-waste recycling site (Jin et al. 2008; Leung et al. 2007; Luo et al. 2009; Zou et al. 2007). For example, Leung et al. (2007) reported that the concentrations of BDE-209 varied from 2.76 to 1,270 ng/g in e-waste site soils at Guiyu, China. In addition, our results were similar to or slightly lower than those in surface soils from nonpoint contaminated sites (Li et al. 2008; Zou et al. 2007). Li et al. (2008) collected 21 surface soil samples from Taiyuan city, China, and found that the levels of low-brominated congeners and BDE-209 were 0.01–0.226 and 0.006–209 ng/g, respectively. Zou et al. (2007) reported the concentrations of low-brominated congeners (mean 1.02 ng/g; range 0.13–3.81 ng/g) and BDE-209 (mean 13.8 ng/g; range 2.38–102 ng/g) in the surface soils sampled from the PRD. However, our results were much higher than PBDEs in surface soils (including

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upland soil, agriculture soils, meadow soil, and moraine soils) from Tibetan Plateau, China (mean 0.011 ng/g; range 0.004–0.035 ng/g). In that study, no BDE-209 was detected in all soil samples (Wang et al. 2009). Globally, our data were within the PBDE concentration ranges reported in European background soils (Harrad and Hunter 2006; Hassanin et al. 2004). Harrad and Hunter (2006) reported PBDE levels ranging from 0.073 to 3.89 ng/g in soil samples from 11 locations on a transect across the West Midlands of the UK. Hassanin et al. (2004) collected surface soils from remote/rural woodland (coniferous and deciduous) and grassland locations through the UK and Norway and found that the total PBDE concentrations (not including BDE-209) varied from 0.065 to 12 ng/g. In addition, our results were lower than those in sludge application soils in European countries (Eljarrat et al. 2008; Matscheko et al. 2002; Sellström et al. 2005). Matscheko et al. (2002) and Sellström et al. (2005) revealed that the PBDE concentrations from sludge application soils in Sweden were 0.05–840 and 0.035–1,700 ng/g, respectively. Meanwhile, Eljarrat et al. (2008) reported that the PBDE concentrations were 5.4–103 ng/g in Spain. Moreover, soils from polyurethane foam (PUF) manufacturing plant and floodplain in USA contained higher PBDEs than that from Chongming Island (Hale et al. 2002; Yun et al. 2008). In contrast, our results were higher compared to PBDEs in soils from Arctic (de Wit et al. 2006), as shown in Table S1. Overall, PBDEs in surface soils from Chongming Island were at the low end of global contamination levels. Similar conclusion was reported in surface sediments from the YRD (Chen et al. 2006a). The most possible explanation for this is that Chongming Island is less urbanized and industrialized relative to other regions with no activities possibly harmful to the environment than agriculture and tourism. Therefore, this island can be considered as a net “recipient” of POPs, receiving inputs predominantly from the YRD via air and wastewater. On the other hand, the residents of the island were responsible at some extent for POPs in environment via electronic equipment application and waste disposal (Hale et al. 2008). 3.2 PBDE congener pattern in the soils As mentioned above, BDE-209 was the most predominant congener in surface soils from Chongming Island, which accounts for more than 90% of the total. This was also found in soils samples collected from Spain and the PRD, China (Eljarrat et al. 2008; Zou et al. 2007). Moreover, BDE-209 was dominated congener in sediments from the YRD (∼90–100%) and the PRD (72.6–99.7%; Chen et al. 2006a; Mai et al. 2005). There are two possible reasons. Firstly, BDE-209 is extremely hydrophobic (log KOW ≈10),

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and it has been widely expected to possess low bioavailability and tendency to strongly bind to sediment and soil (Hale et al. 2002). Secondly, the consumption of deca-BDE was much larger than those of penta-BDE and octa-BDE. For example, the market demand for PBDEs was 24,650 metric tons in 2001 in Asia, where deca-BDE, penta-BDE, and octa-BDE were 23,000, 150, and 1,500 metric tons, respectively (Hites 2004). In China, the domestic production and demand of PBDEs are enormous and have increased yearly and the predominantly used product deca-BDE amounting to 30,000 metric tons in 2005, followed by octa-BDE and penta-BDE (Zou et al. 2007). The compositional profiles of 26 PBDEs to Σ26PBDEs (excluding BDE-209) in soils are presented in Fig. 2a. BDE-99 was the dominated congeners with a percentage of 28.9%, followed by BDE-47 (10.8%), 153 (9.0%), 196 (5.5%), 100 (4.7%), 154 (4.0%), 183 (3.5%), and 28 (3.2%). As shown in Fig. 2b, congeners pattern of BDE47, 99, 100, 153, and 154 in soils is similar to that of the major components of the two commercial penta-BDE product Bromkal 70-5DE and DE-71, indicating that a penta-BDE commercial mixture may be the other major formula used around this region. Similar PBDE congener pattern were also found in sediments from the Yangtze River (Chen et al. 2006a) and soils from the PRD (Zou et al. 2007) and European countries (Hassanin et al. 2004). As an additive flame retardant, penta-BDE was largely used in PUF of furnishings, cars, textiles, etc. PBDEs can be easily released from these products into the ambient environment when they are used or disposal. BDE-49 with high concentrations found in some soil samples compared to BDE-47 may due to the debromination of high-brominated congeners under natural sunlight, such as from BDE-99 to BDE-49 (Kajiwara et al. 2008; Söderström et al. 2004).

30 25 20 15

3.3 The relationship among PBDE congeners and TOC Generally, POP levels in soil are strongly influenced by the organic carbon/matter content of the soil (Gouin and Harner 2003; Nam et al. 2008). In this study, TOC content of the surface soil samples ranged from 0.67% to 1.61%. Figure 3

(a) Composition (%)

35

50 40

(b)

BDE-28 BDE-47 BDE-99 BDE-100 BDE-153 BDE-154 BDE-183

30 20 10 0 surface soil

DE-71

70-5DE

10 5 0 B D B E-1 D 5 B E-1 D 7 B E-2 D 5 B E-2 D 8 B E-3 D 2 B E-3 D 3 B E-3 D 7 B E-4 D 7 B E-4 D 9 B E-6 D 6 B E-7 D 5 B E-7 D 7 B ED 99 B E-1 D 00 B E-1 D 16 B E-1 D 18 B E-1 D 19 B E-1 D 26 B E-1 D 38 B E-1 D 53 B E-1 D 54 B E-1 D 66 B E-1 D 81 B E-1 D 83 B E-1 D 90 E19 6

% of ∑ 26PBDEs

Fig. 2 a Compositional profiles of PBDE congeners (except BDE-209) in surface soils from Chongming Island. b Congeners patterns of BDE-28, 47, 99, 100, 153, 154, and 183 in surfaces soils and two technical penta-BDE products (70-5DE and DE-71). Error bars represent 1 SD

Moreover, BDE-183 is a marker of octa-BDE products (La Guardia et al. 2006). Hence, the relatively higher portion of BDE-183 in soil samples indicated the likely additional input from octa-BDE products in Chongming Island. Interestingly, the average of ratios between BDE-47 and BDE-99 in soils was 0.52, which differ from those in Bromkal 70-5DE (ratio is ∼0.96) and DE-71(ratio is ∼0.79) employed in China (Fig. 2b). Such difference may result from PBDE congeners fractionation changing during their transport in the environment and partitioning in various environmental media/surfaces due to their different physicochemical properties, i.e., volatilization, log KOW, and water solubility, etc., or vegetation absorption, biodegradation, and photodegradation in soils, and/or a different commercial penta-BDE formulation used around the region (Gerecke et al. 2005; Gouin and Harner 2003; Mattina et al. 2004; Meijer et al. 2003; Vonderheide et al. 2006). Gouin and Harner (2003) developed a model on the environmental fate of PBDEs illustrating that BDE congeners may undergo different degradation processes in soil at the presence of vegetation. Similarly, the ratios of BDE-47 to BDE-99 ranged from 0.53 to 0.88 in soils collected from the UK and Norway (Harrad and Hunter 2006). In that study, Harrad and Hunter (2006) suggested that the lower 47:99 ratios in soils than those in technical penta-BDE were due to BDE-99 has higher KOA relative to BDE-47. As a result, greater atmospheric deposition and retention by soil postdeposition were found for BDE-99 than BDE-47.

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Fig. 3 The relationships between the levels of PBDE congeners and TOC content in soils

500 400

1600

BDE-47 y=99.2x+2.5 r=0.37

1200

BDE-99 y=411.5x-127.7 r = 0.42

300 800

200 400

100

Concentrations (pg/g dw)

0 250 200

0 800

BDE-100 y=41.2x+1.7 r=0.36

600

BDE-153 y=108.3x-21.9 r=0.31

150 400

100 200

50 0

0

250

40000

200

BDE-154

BDE-209 y=7460x+4395 r=0.31

y=54.1x-28.3 r=0.38

30000

150 20000

100 10000

50 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

TOC (%)

3.4 The distribution of PBDEs in soils with land use There is a division between the farmland soils (nine sites), the grassland soils (three sites), the woodland soils (four sites), the tideland soils (three sites), and the road soils (three sites). No significant statistical differences (ANOVA, p>0.05) in the PBDE concentrations were observed in five land use types of soil, which probably indicate that they

TOC (%)

have similar PBDE source. Farmland and woodland soils contained higher Σ26PBDE concentrations (0.21–2.3 ng/g with an average of 0.94 ng/g; 0.05–2.2 ng/g with an average of 1.2 ng/g, respectively) than other three types of soils (Fig. 4; Table S1). In addition, grassland, tideland, and

∑ 26PBDEs (pg/g dw)

10000

1000

100 100000

BDE-209 (pg/g dw)

presented regression data of soil concentration versus TOC for BDE-47, 99, 100, 153, 154, and 209. Weak correlations were found between TOC contents and the concentrations of BDE-47 (r=0.37), BDE-99 (r=0.42), BDE-100 (r= 0.36), BDE-153 (r=0.31), BDE-154 (r=0.38), and BDE209 (r=0.31), which is in agreement with the result reported in Yangtze River sediment (Shen et al. 2006). Poor correlations between the PBDE concentrations and TOC were also observed in sediments from the South China Sea, Beijiang River, and the PRD (Chen et al. 2009; Mai et al. 2005). Lohmann et al. (2000) suggested that some factors such as proximity to sources, land use, influence of wet deposition, degradation in the environment, and atmospheric transport may also exert strong influences on POP distribution in soils. Therefore, more studies are needed to explore the factors influencing PBDE distribution in Chongming Island.

0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

10000 1000 100 10

Farmland Grassland Woodland Tideland

Road

Fig. 4 The concentrations of Σ26PBDEs and BDE-209 in different types of soils (picograms per gram dw)

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road soils have similar Σ26PBDE concentrations, which are 0.40–0.62 ng/g with an average of 0.51 ng/g, 0.16–0.79 ng/g with an average of 0.54 ng/g, and 0.20–0.79 ng/g with an average of 0.42 ng/g, respectively. Previous study has shown that woodland surface soils generally contain higher concentrations of PBDEs than grassland soils (Hassanin et al. 2004). This may be explained by differences in scavenging/ deposition mechanisms between woodland and grassland soils (Wania and McLachlan 2001) and/or the turnover/ mixing processes operating in the different soil systems (Meijer et al. 2003). The highest BDE-209 concentration (35 ng/g) was found in one farmland soil sample, though road soils contained the highest mean concentration with a value of 14 ng/g, followed by farmland soils (13 ng/g), woodland soils (11 ng/g), tideland soils (8.8 ng/g), and grassland soils (5.0 ng/g; Table S1). Apparent variability in PBDE concentrations was found in individual samples in different land use (Fig. 4). The influencing factors of PBDE distribution in soils are complicated. Except for proximity to point sources, the different abilities of soil microbes to degrade different PBDE congeners may alter the PBDE concentrations and patterns in soils with different land use. Gerecke et al. (2005) found that BDE-209 is vulnerable to anaerobic bacteria, while aerobic microbes can preferentially utilize lower-brominated BDEs as carbon sources (Vonderheide et al. 2006). Moreover, plants may be a factor that influence PBDE concentrations and profile in different soils (Mattina et al. 2004; Singer et al. 2003). Furthermore, Mueller et al. (2006) indicated that certain plant species can accumulate PBDEs in root and shoot tissue and may enhance PBDE bioavailability. Therefore, more studies are needed to investigate PBDE distribution in different land soils. 3.5 PBDE inventory in Chongming Island To assess the potential of soils as a source for PBDEs to the agricultural products in Chongming Island, the mass inventories of Σ26PBDEs and BDE-209 in this region were estimated. We used the average concentrations of Σ26PBDEs and BDE-209, respectively, in farmland, grassland, woodland, tideland, and road soils. The inventory (I, kilograms) was calculated by the following equation (Zou et al. 2007): I ¼ kCi Ai dr

ð1Þ

ρ k

is the average density of the dry soils particles (grams per cubic meter) is the unit conversion factor

The soil areas of farmland, grassland, woodland, tideland, and road in Chongming Island are 499.2, 2.93, 78.5, 138.3, and 39 km2, respectively (Shanghai Municiphal Housing Land and Resource Administratic Bureau 2009). With a soil depth of 20 cm and an assumed soil bulk density of 1.5 g/cm3, the mass inventories in soils of farmland, grassland, woodland, tideland, and road respectively estimated to be 2.1, 0.012, 0.42, 0.46, and 0.074 kg for Σ26PBDEs and 197, 0.43, 25, 70, and 17 kg for BDE-209. The inventories of both Σ26PBDEs and BDE-209 in farmland soil appeared to be greater by 1 to 2 order of magnitude than those for other four types of soils. In Chongming Island, agriculture is the main human activity covering an area of about 39% of the total area. Therefore, it is urgent to assess human intake of PBDEs via agriculture consumption products in this region because plant can accumulate PBDEs in root and shoot tissue (Mueller et al. 2006).

4 Conclusions To the best of our knowledge, this is the first study on PBDE levels, profiles, and inventories in surface soils from the Chongming Island, which provides POPs data for the YRD, one of most the developed regions in China. PBDE levels in this area were similar to those reported in European background soils and much lower than those in e-waste contaminated sites in China. BDE-209 contributed more than 90% to the total in all soil samples, followed by BDE-99, 47, 153, 196, 100, 154, 183, and 28. Clearly, technical deca-BDE and penta-BDE were the main products employed in this region. Moreover, the variation of PBDE concentrations among different types of soils may relate with their physical and chemical properties and environmental processes. Furthermore, the increasing textiles and chemical and electronic industries in the YRD may pose a potential influence for PBDE contamination in Chongming Island either via air or wastewater inputs. Hence, more studies need to be conducted to explore the sources and risks of PBDEs in Chongming Island.

where: Ci

Ai d

is the average concentration of Σ26PBDEs or BDE209 in different types of soils (nanograms per gram dry weight) is area of different land usage (square kilometers) is the thickness of the soil sampled (centimeters)

Acknowledgments This study was funded by the National Natural Science Foundation of China (No. 40901251), the Shanghai Committee of Science and Technology, China (No. 09ZR1433700), the Foundation of the State Key Laboratory of Pollution Control and Resource Reuse, China (No. PCRRY09001), and International S&T Cooperation Projects from Ministry of Science and Technology of China (No. 2009DFA90740).

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