Ravi Naidu¹ and N S Bolan²

¹CSIRO Land and Water, Waite Road, Urrbrae, Adelaide, South Australia 5064
²Fertilizer and Lime Research Centre, Institute of Natural Resources, Massey University

Environmental contamination through anthropogenic activities and pedogenic processes is a widespread and serious problem confronting scientists and regulators throughout the world. The most frequent contaminants include heavy metals (cadmium, lead, copper and zinc), metalloids (arsenic and selenium), pesticides (organochlorines and organophosphates) and industrial organics (polyaromatic hydrocarbons, poly chlorobiphenyls and petroleum hydrocarbons). These contaminants are commonly found in contaminated soils in both urban and rural environments. Noting the potential adverse impacts of such contaminants on environmental and human health many countries have introduced strict legislations to protect environmental biota, animals and humans from potential adverse impacts of these contaminants. However, depending on the nature of contaminant, such legislation measures vary significantly between countries. While regulatory measures are well adopted in developed countries, poor adoption is reported in developing countries. For this reason the extent and severity of environmental contaminated in many developing countries is extensive. Ensuring clean food production, better industrial processes and maintenance of clean water resources are therefore critical for managing contaminated land.

Currently there are over 1 million contaminated sites in Australia, New Zealand, Asia, Europe and USA. It is estimated that remediation costs can exceed $5 billion dollars in the Tasman alone while this could treble for contaminated site remediation in USA. The most common approach to remediation includes excavation and transport of soils to prescribed landfill sites, pump and treat for contaminated water and soil treatment technologies. Amongst the soil treatment technologies, bioremediation of contaminated sites is proving extremely popular, especially for organically contaminated soils. Remediation is often constrained by the huge costs associated with the treatment technologies. The strategies for the remediation of contaminated sites can be established on the basis of risk assessments that rely on ecotoxicity of contaminants of concern. Risk based land management (RBLM) technology is now considered an attractive option in Europe and USA. This involves quantification of risks posed by contaminants to end-users and remediation is recommended only when contaminants are highly bioavailable. Thus RBLM is based on monitored natural attenuation (MNA) of toxic substances. Monitored natural attenuation uses natural processes that decrease the risks posed by contaminants to environmental and human health. One of the assumptions of MNA processes is that the contaminant bioavailability in soil decreases with time (i.e. ageing). Consequently bioavailability is used as the key indicator of potential risk that contaminants pose to both environmental and human health. This paper discusses the sources of contaminants, potential risks to environmental and human health and cost effective strategies including RBLM that could be adopted to minimize environmental impact of such pollutants.

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