Main author: Richard Thompson (FAO-GSP)
Contributing authors: Erika Santos; Diego Arán; Pilar Bernal; Andrea Ceci; Giada Migliore; Donato Visconti; Pavlos Tyrologou; Susan Wilson; Mojtaba Yahyaabadi
This chapter aims to provide an overview, and by no mean a complete description and list, of the available tools and technologies for remediating polluted soil and groundwater, and of management and adaptation strategies to mitigate the risks from polluted soil. This chapter addresses both polluted soil and groundwater because the migration of contaminants within groundwater can increase their dispersal within soil.
The assessment of the risks that a polluted site poses is the basis of the decision to remediate or to mitigate risk. In both cases, the aim is to break any possible links where the pollution source has an exposure pathway to affect the receptor. Remediation aims to eliminate or isolate the source, whereas management and adaption strategies aim to block exposure pathways or remove the receptors. There are many approaches to assessing risk and developing a decision-making strategy depending on the receptor, type and amount of contaminants, time and pathways for exposure, etc. (Aven, 2016). However, the methodology applied will depend largely on the specific conditions of each site. FAO and the GSP are developing the “Technical Guidelines for assessing, mapping, monitoring and reporting soil pollution” to support governments and technicians in developing these risk analysis and decision-making strategies (FAO, forthcoming). This document is expected to be published in the second half of 2021.
Undertaking a site remediation may be both onerous and expensive depending on the technology and rehabilitation strategy. The main motives for taking action to investigate and address a polluted site are social responsibility, financial and legal compliance. Demonstrating good corporate social responsibility has been a driver for some organizations. Where the value of the site can be enhanced, or financial institutions require remediation before transfer of ownership, there is a financial motive to remediate. Environmental legislation may require those responsible for a polluted site to remediate it or to otherwise reduce the risks that it poses. Governments and Intergovernmental Organizations have intervened directly in cases of sites that represent a high risk to public health and the environment and that have no owner (for example the Superfund programme in the United States of America,1 and the Global Environment Facility’s (GEF) Chemicals and Waste programme2).
As soon as a site is identified as being polluted or threatened of becoming polluted, a risk assessment should be undertaken and measures put in place immediately to protect the population, prevent or reduce the spread of the contaminants and identify those responsible for the site and for the source of the pollution. Potential immediate risk reduction measures are discussed in Section 13.2. Once these safeguarding measures have been done, the site can be investigated in detail to determine the next steps. Identifying the polluter will assist in assigning responsibility for funding the safeguarding measures and subsequent remediation strategy. In the case that the polluter cannot be identified or is unwilling to intervene, the national authorities, or subnational, depending on how jurisdictional power is shared within a country, should take immediate control of the situation. It is recommended that countries maintain a database of contaminated sites which can assist in decision-making on priorities and funding.
Given the possibility of permanent degradation of land, the risks to public health and environment, and the expense and complexity of remediation, the avoidance of soil pollution is an obvious priority. It is important to eliminate or reduce potential sources of pollution before the contaminants start to disperse into the environment. The costs of safeguarding and eliminating a concentrated contaminant before it has leaked are orders of magnitude less than the cost of remediating the soil afterwards as is illustrated in Figure 1 below. The cost of inaction in eliminating global stocks of POPs and obsolete pesticides is particularly significant (Vijgen and Egenhofer, 2009). Addressing this global issue is a priority for the European Union and the GEF, among other organizations, and they have assisted many countries to safeguard and destroy their stocks of POPs in an environmentally sound manner.