Introduction to Organic Contaminants in Soil: Concepts and Risks

This chapter introduces an overview of the main aspects of soil contamination: the types of contaminants, the threats to soil biota and quality, the effects on humans and animals and legislation concerning contaminants, with a focus on European laws and regulations. Although soil is a non-renewable natural resource, humans have increasingly used it as a contaminant sink ever since the Industrial Revolution. Pollution endangers natural soil mechanisms that allow the soil to keep itself in balance and compromises the supply of soil-based goods and services. Detrimental effects of contaminants on soil microbiota may be directly related to loss of biodiversity and functions such as the recycling of nutrients. However, this direct negative effect is still debated among microbial ecologists because microbial communities may be surprisingly resilient (i.e. able to recover from contamination effects) and/or functionally redundant. Likewise, the potential toxicity of soil contamination to humans is controversial as investigations on the mix of different contaminants are very limited. Due to accumulated evidence of the potential toxicity of single contaminants on human health and animals, mostly based on in vitro or in vivo assays, international guidelines, such as the Stockholm Convention on Persistent Organic Pollutants, have established a list of priority contaminants. Despite worldwide concern about soil contamination, Europe still lacks a common soil legislative tool because the proposed Soil Directive Framework is currently under negotiation. The lack of a European directive is nevertheless compensated by national policies at the member state level.