A review of green remediation strategies for heavy metal contaminated soil

Heavy metals and metalloids can accumulate in soil, with potentially toxic effects to human health and ecosystems, threatening the sustainable use and management of soil resources. Although a number of remediation technologies, such as Solidification/Stabilization (S/S), soil washing, electrokinetic remediation and chemical oxidation/reduction can be applied for the immobilization, removal or detoxification of heavy metals in soil, the environmental, social and economic impacts associated with these conventional approaches hinder their overall sustainability. More attempts have been made to maximize the 'net environmental benefit' in various ways, including recovering resources, embracing nature-based solutions (NBS), and saving energy with the emergence and development of the 'green and sustainable remediation' (GSR) movement. This review critically discusses these green remediation strategies, and the novel soil amendments being utilized in these sustainable approaches. Iron-based amendments are the most promising candidates in green remediation due to the highest stabilization performances for both oxyanions and metallic cations as well as relatively low disturbance to soil. In comparison, waste-derived materials suffer from risks of contaminant release in the long run, reducing the overall sustainability despite their low costs. It has been found that phytoremediation and green amendment-based S/S are typically the 'greenest' remediation strategies, but wise decisions should be made on the basis of case-specific sustainability assessment results. Finally, it is proposed that integration of several green remediation techniques may have a synergistic effect on remediation efficiency