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Toxic Chemicals

Volume 702: debated on Monday 23 June 2008

asked Her Majesty's Government:

Whether reed beds provide a method for concentrating or eliminating toxic chemicals such as polychlorinated biphenyls and dioxin from soil and surface water in a manner that is effective and safe for wildlife which access the beds. [HL4089]

Reed bed systems have been found to be effective in reducing levels of suspended solids, metals and organic pollutants from wastewaters. They also provide a habitat for wildlife that might not otherwise be present, and can support a diverse ecosystem including microbes, invertebrates, mammals and birds.

Reed beds reduce the emission of contaminants to watercourses by allowing particulates to settle out, by adsorption of contaminants to sediment and organic matter, the microbial degradation of chemicals and uptake of contaminants by plant roots.

While these processes reduce emissions to the wider environment, some of the contaminants will accumulate within the reed bed system. Research shows that levels of metals increase in the sediment in reed beds, and also within the reeds. We are unaware of similar studies with polychlorinated biphenyls or dioxins, but would also expect these substances to accumulate.