Developing natural ways to rehabilitate mercury-contaminated soils and evaluating their efficiency using bio-indicators

Mercury (Hg) pollution is a major concern in the Philippines due to the abundance of small-scale mining activities. Despite drastic effects of Hg on soil communities in laboratory experiments (Martinez et al., under review), a field study in the Philippines did not show a strong negative impact of even high Hg-concentrations on soil communities (Martinez et al., 2018). This warrants an investigation on the role of vegetation in reducing metal bioavailability and pollution. Removal of toxic metals by plants, i.e., phytoremediation, has been used in many countries, yet it has received less attention in the Philippines, and its efficacy is both plant species-specific and context-dependent. Here we will explore ways to improve its efficiency by combining phytoremediation with biochar application. Biochar, known to temporarily immobilize soil pollutants, will be derived from local resources. An effective soil remediation strategy, i.e., reducing Hg in contaminated soils, would lead to soil improvement following the re-establishment of soil communities, such as nematodes and microbes, after a pollution impact.