Transport and fate of contaminants in soils: challenges and developments

Human and environmental risk due to contaminants is quantified as the product of hazard and exposure. For many soil and water contaminants, such as heavy metals or organic compounds, the hazards are well known. The challenge is to determine better the exposure pathways. For emerging contaminants, such as nanoparticles, both the toxicity and exposure pathways are unknown. A pollutant’s risk can be due either to the continued residency in the soil, or their subsequent fate in receiving waters. Transport of pollutants through soil defies robust prediction currently due to preferential flow processes along macroporous networks, and this is compounded by spatial heterogeneity in the sources of contamination. However, hardwon biophysical knowledge of chemicals moving through soil is increasingly being incorporated into decision support tools to guide risk assessment policies and to assist with risk-based prevention and remediation practices.