remediation of polychlorinated biphenyls

Electronic and electric waste (e-waste) has emerged as a critical global environmental health issue because of its massive production volume and insufficient management policy in both developed and developing countries (Ogunseitan et al., 2009; Chen et al., 2011). The disposal, recycling, and part-salvaging of e-waste has polluted the soil, water and air with toxic chemicals, such as heavy metals and persistent organic compounds ( Leung et al., 2006; Wong et al., 2007; Ladou and Lovegrove, 2008; Robinson, 2009). Polychlorinated biphenyls (PCBs), which have been widely used as plasticizers, hydraulic and heat exchange fluids, coolants and lubricants in transformers and capacitors, may also be present in the e-waste stream. Due to its high capacity to store pollutants, soil appears to be the major sink for PCBs in various environments (Dalla Valle et al., 2005). Soil samples collected from several villages in Taizhou e-waste recycling area contained high levels of PCBs (52.0 - 5789.5 μg/kg) (Tang et al., 2010a). PCBs were also detected in soil samples from the open-burning site in the Guiyu e-waste recycling area, with total concentrations ranging from 73.8 to 1443 μg/kg (Wong et al., 2007).
PCBs and other organic/inorganic pollutants present in soil could be toxic to plants, microorganisms and invertebrates (Andreoni et al., 2004; Zhang et al., 2009b). Therefore, microbial indicators, such as respiration rate, enzymatic activity and biomass content, have been used to indicate the effect of pollution on soil quality (Renella et al., 2004; Shukurov et al., 2005). Microorganisms are considered to be the best indicators, due to their function, ubiquitous presence and high sensitivity to pollutant stress (Andreoni et al., 2004; Abd Elsalam et al., 2006). However, as more than 99% of soil microorganisms cannot be cultivated by traditional laboratory techniques (Baker et al., 2001; Zhang et al., 2009a; Lee et al., 2010), culture-independent molecular techniques, such as