A review of the environmental fate and effects of hazardous ...

30 A. Sepúlveda et al. / Environmental Impact Assessment Review 30 (2010) 28–41• Fly and bottom ashes from burning activities• Fumes from mercury amalgamate “cooking”, desoldering, and otherburning activities• Wastewater from dismantling and shredding facilities• Effluents from cyanide leaching, other leaching activities or mercuryamalgamationDumped materials containing heavy metals and brominated andchlorinated flame retardants can affect soils (Fig. 1). The mobility ofthese substances towards other environmental compartmentsdepends on diverse environmental parameters such as pH, organicmatter content, temperature, adsorption–desorption processes, complexation,uptake by biota, degradation processes, and the intrinsicchemical characteristics of the substance (Sauvé et al., 2000;Georgopoulos et al., 2001; Hu, 2002; Gouin and Harner, 2003; Qinet al., 2004). Ionic and occasionally, methylated heavy metals, areparticularly mobile and bioavailable (Dopp et al., 2004; Hirner, 2006).Lower brominated congeners of flame retardants such as PBDEs arealso particularly mobile while higher brominated congeners tend tobond to particles and exhibit lipophilic properties (Gouin and Harner,2003). PBDEs are used as flame retardants in plastic and textilematerials. Three different commercial products exist: PentaBDE,OctaBDE and DecaBDE, which differ in their degree of bromination.All three products can be used in a large variety of polymers, however,PentaBDE has been most widely used in polyurethan foam, OctaBDE instyrene copolymers and DecaBDE in high-impact polystyrene (Alaeeet al., 2003). Thus, especially OctaBDE and DecaBDE can be foundin WEEE. Heavy metals not recovered during WEEE treatmentand residual auxiliary substances like mercury and cyanide canleach through the soil after disposal of effluents and form inorganicand organic complexes within soils (Fig. 1). These effluents can alsoenter water bodies and the subsequent fate of original and auxiliarysubstances will depend on the processes described above as well asscavenging processes (between aqueous phase and sediments) andvolatilisation.Dismantling activities release dust particles loaded with heavymetals and flame retardants into the atmosphere. These particleseither re-deposit (wet or dry deposition) near the emission source orcan be transported over long distances depending on their size. Inaddition, dust directly incorporated in wastewater can enter the soilor water systems and together with compounds found in wet anddry depositions, can leach into groundwater or react with the biota(Fig. 1). The environmental fate of particles, ashes and fumescontaining heavy metals and PBDEs released by burning activities issimilar to that of the emissions released by dismantling activities(Fig. 1). However, the thermal or inadequate metallurgical treatmentof WEEE can lead to the formation of extremely hazardous byproductssuch as polyhalogenated dioxins and furans. They are amongthe most hazardous anthropogenic pollutants (Allsopp et al., 2001;Tohka and Lehto, 2005) and one of their most important formationpathways is the burning of plastic products containing flameretardants and PVC (USEPA, 1997). As copper (Cu) is a catalyst fordioxin formation, Cu electrical wiring coated with chlorine containingPVC plastic contributes to the formation of dioxins (Kobylecki et al.,2001; Gullett et al., 1992). Chlorinated and brominated dioxins andfurans (PCDD/Fs and PBDD/Fs), and mixed halogenated compoundslike the polybrominated–chlorinated dibenzo-p-dioxins (PBCDDs)and polybrominated–chlorinated dibenzofurans (PBCDFs) can beformed during WEEE burning (Söderström, 2003). Once emittedinto the atmosphere, dioxins and furans are dispersed into theenvironment, and because of their semi-volatile and hydrophobicproperties, they tend to accumulate in organic rich media (Adriaenset al., 1995; Smith and Jones, 2000). Higher brominated or chlorinatedcongeners degrade more slowly and tend to partition more into lipidsFig. 1. Principal WEEE recycling activities in China and India, types of produced emissions and general environmental pathways. Ovals: types of substances contained withinemissions. Continuous bold lines: fate of original and auxiliary substances. Dotted bold lines: fate of by-products such as dioxins and furans. Black arrows with a bold dot: materialtransport fluxes between treatments. Fine dashed arrows: general environmental pathways. Environmental fluxes are driven by processes as atmospheric deposition (dry/wet),leaching, adsorption–desorption, complexation (by which heavy metal and cyanide secondary products can be formed), uptake, degradation (chemical/biological) and volatilization.In addition, the environmental fate of pollutants depends on the physico-chemical properties of the media.