environmental toxicology and pharmacology 34 (2012) 358–369 Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/etap The combined effect of decabromodiphenyl ether (BDE-209) and copper (Cu) on soil enzyme activities and microbial community structure Wei Zhang a,b,∗, Meng Zhang a,b, Shuai An a,b, Kuangfei Lin a,b,∗, Hui Li a,b, Changzheng Cui a,b, Rongbing Fu c, Jiang Zhu c a State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology, Shanghai 200237, PR China b School of Resource and Environmental Engineering, East China University of Science and Technology, Shanghai 200237, PR China c Shanghai Academy of Environmental Sciences, Shanghai 200233, PR China article info abstract Article history: Waste electrical and electronic equipment (e-waste) is now the fastest growing waste stream Received 13 August 2011 in the world. It is reported that polybrominated diphenyl ethers (PBDEs) and heavy metals Received in revised form were main contaminants in e-waste recycling site. Among these contaminants BDE-209 5 April 2012 and Cu were widespread, yet their combined effect on soil enzyme activities and microbial Accepted 23 May 2012 community structure are not well understood. In this study, the ecotoxicological effects of Available online 5 June 2012 both combined and single pollution of BDE-209 and Cu at different concentration levels were studied under laboratory conditions. The activities of soil catalase, urease and saccharase Keywords: were sensitive to BDE-209 and Cu pollution. Although the enzyme activities varied over BDE-209 time, the concentration effects were obvious. Statistical analyses revealed that, at the same Cu incubation time, as the concentration of BDE-209 or Cu increased, the enzyme activities Combined effect were decreased. Combined effects of both BDE-209 and Cu were different from that of BDE- Soil enzyme activity 209 or Cu alone. Enzyme activities data were essentially based on the multiple regression Microbial community structure technique. The results showed that the action and interaction between BDE-209 and Cu were Ecotoxicological effect strongly dependent on the exposure time, as the combined effects of BDE-209 and Cu were either synergistic or antagonistic at different incubation times. Soil catalase and saccharase were more comfortable used as indicators of BDE-209 and Cu combined pollution, as the variation trends were similar to the single contaminant treatments, and the responses were quick and significant. Denaturing Gradient Gel Electrophoresis (DGGE) analysis of bacterial 16S rDNA gene showed that BDE-209 and Cu pollution altered the bacterial community structure by promoting changes in species composition and species richness. The existence of BDE-209 and Cu in soils reduced the microbial diversity, and the concentration effects were obvious. Overall, microbial diversity in the combined treatments were lower than the single ∗ Corresponding authors at: State Environmental Protection Key Laboratory of Environmental Risk Assessment and Control on Chemical Process, Shanghai Key Laboratory of Functional Materials Chemistry, East China University of Science and Technology, Shanghai 200237, PR China. Tel.: +86 21 64253244; fax: +86 21 64253988. E-mail addresses: [email protected] (W. Zhang), kfl[email protected] (K. Lin). 1382-6689/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.etap.2012.05.009 environmental toxicology and pharmacology 34 (2012) 358–369 359 ones, and when the concentration of BDE-209 and Cu increased, and the Shannon–Weaver index decreased, which indicated the combined effect of BDE-209 and Cu on the microbial community structure was synergistic. Our results further the understanding of the toxic effects of BDE-209 and Cu on soil enzyme activities and microbial community structure, and suggest the need for more in-depth analysis to increase progressively the understanding of the toxicological mechanisms involved. © 2012 Elsevier B.V. All rights reserved. provide only part of the knowledge necessary to evaluate the 1. Introduction toxic potential for wildlife and human. Also it is difficult to make clearly hazard assessments and predictions of possible With the rapid development of electric technology, waste elec- ecotoxicological effects. As everyone knows, POPs and heavy trical and electronic equipment, also known as e-waste, refers metal that accumulate in the environment and in food webs to end-of-life products including computer, cellular phone result in long-term threats to public health and ecosystem and television is rather striking. It has been estimated that stability (Ariese et al., 2001; Altındag˘ and Yigit,˘ 2005; Opopol, 20–50 million tonnes of e-waste are produced annually in 2007). the world and increases rapidly at a rate of 3–5% per year Soil microflora plays a major role in the decomposition (Robinson, 2009). Taking advantage of inexpensive cost of labor of organic matter and the mineralization of nitrogen, phos- and weak enforcement of environmental laws, much more phorus, and sulfur in the agro-ecosystem, they also play e-waste is being exported to developing countries. It was esti- significant roles in maintenance of soil structure, detoxifi- mated that 50–80% of the global e-waste was imported into cation of noxious chemicals, and the control of plant pests Asia, from which 90% ended up in China (Schmidt, 2002, 2006). and plant growth (Elsgaard et al., 2001; Filip, 2002). Since However, the recycling techniques in these countries are soil microorganisms can respond rapidly, they reflect a haz- often crude and do not have the appropriate facilities (Tang ardous environment and are, therefore, considered when et al., 2010a); waste processing operations such as uncon- monitoring soil status. A number of soil microbiological trolled dismantling, acid stripping and open burning in parameters, notably such as enzyme activities, microbial com- Chinese e-waste recycling sites (EWRSs) have resulted in munity structure, microbial biomass, have been suggested as severe environmental contamination (Wong et al., 2007a). The possible indicators of soil environmental quality, and have hazard of e-waste lies in the high content of many toxic sub- been employed in national and international monitoring pro- stances. As a result of the unprotected recycling techniques, grams (Dick, 1994; Yao et al., 2000; Kakkar and Jaffery, 2005). various high toxic pollutants such as persistent organic pol- Enzymatic activities are sensitive indicators of stress, and lutants (POPs) (e.g. PBDEs) and heavy metals (e.g. Cu), were a reduction in enzymatic activities would be the expected released into the environment (Wong et al., 2007a,b; Ni et al., response to an acutely toxic chemical. Catalase, urease and 2010). For instance, Guiyu, one of the largest EWRSs in South saccharase have been widely used as indicators of the pertur- China, the sum concentrations of PBDEs in combusted residue bation of soil by pollutants (Sahrawat, 1979; Lu et al., 2004; Qian and soil samples were 33,000–97,400 and 2020–4250 ng/g dw, et al., 2007). The activity of urease is known to be sensitive to respectively, and BDE-209 was the most dominant congener pollutants, such as heavy metals (Yang et al., 2006), pesticides (35–82%) among the study sites (Li et al., 2011). In soil near (Sahrawat, 1979), and antibiotics, and the catalase activity printer roller dumping area and plastic burn site, the concen- is often used to indicate the microbial anti-oxidation ability trations of Cu were 712 and 496 mg/kg dw, respectively (Leung (Caldwell, 2005), which is stimulated when slightly toxic com- et al., 2006). Luo and Shen reported that PBDEs concentration pounds are present, and inhibited when the toxicity increases in the farmland soils 2 km from an e-waste recycling work- (Shi et al., 2004). shop were 191–9156 ng/g dw and BDE-209 were ranged from BDE-209 was dominant PBDEs congener (Hale et al., 2003; 69.1 to 6319 ng/g with average of 1539 ng/g (Luo et al., 2009; Christensen et al., 2005; Voorspoels et al., 2007; Law et al., Shen et al., 2009). Tang and Zhang found that paddy soils near 2008). Because of the ubiquitous use of BDE-209 and their an e-waste recycling area were contaminated with Cu (mean lipophilic and inert characteristics, soil is very likely a sink concentration 176.2 or 256.4 mg/kg) (Zhang and Ming, 2009; for BDE-209 (Lacorte et al., 2003; Hassanin et al., 2004). It is Tang et al., 2010b). All these have led to high pollution level reported that BDE-209 can reach toxic concentrations that are in the ambient environment, and further threaten the ecosys- detrimental to the environment as well as to human health tem local and inhabitants’ health (Deng et al., 2006; Yu et al., (Covaci et al., 2008; Harrad and Porter, 2007). Some study has 2006). demonstrated that BDE-209 in soil, although of low bioavail- Some studies have been focused on the environment pol- ability, had an adverse impact on the microbial structure and lution caused by e-wastes in China since the last decade. The function (Zhu et al., 2010; Liu et al., 2011). Furthermore, heavy accumulation of PBDEs and heavy metals in soil has been metal pollution can not only result in adverse effects on var- reported in some sites of e-waste recycling locations (Cai and ious parameters relating to plant quality and yield but also Jiang, 2006; Yu et al., 2006; Hu et al., 2009). However, since these cause changes in the composition and activity of microbial data do not take into account the possible combined effects of community (Giller et al., 1998). Copper is classified as one different contaminants, as well as their bioavailability, they of the most hazardous heavy metals, although it poses risk 360 environmental toxicology and pharmacology 34 (2012) 358–369 only when its quantities exceed natural background.