Pathway analysis and guidelines for nature-based remediation of mercury contaminated ASGM sites in Indonesia

Related theme: Soil & Groundwater

Challenge

One of the largest contributors to mercury contamination on earth is Artisanal Small Scale Gold Mining (ASGM), primarily due to the use of mercury in gold extraction from ores. Indonesia ranks as the third-largest contributor to global mercury contamination. Mercury usage and related (atmospheric) deposition result in health and environmental challenges as soil and groundwater in rural communities that practice ASGM are contaminated. A critical global challenge remains: to effectively reduce the world's largest source of mercury contamination.

Thus far, limited soil and groundwater research has been conducted at active and former ASGM sites. The relationship between health issues and environmental contamination is known, but the pathways through which soil and groundwater contamination affects health and the environment are not yet fully understood.

Results and solutions

In collaboration with the Consortium and partners, site visits were conducted at dozens of sites, of which two small-scale ASGM locations in Lombok and West Sumbawa were selected to carry out soil and groundwater investigations to determine mercury concentrations, set up conceptual site models to understand the pathways, and a risk assessment was made to determine the potential exposures. As a solution to reduce risk, a local and nature-based solution was developed for remediation and tested by lab studies, resulting in a guideline document to immobilise mercury at ASGM-contaminated sites.

This resulted in the following insights and milestones while performing fieldwork and developing the guideline document and scientific studies:

• More than 15 site visits and two soil and groundwater investigations conducted in Lombok & West Sumbawa
• Highest mercury concentrations found in (backfill material) sedimentation pond and the top soil (0-10 cm) nearby the ASGM platform. Groundwater mercury concentrations slightly elevated and below WHO drink water norm
• Soil and groundwater analyses, conceptual site model and risk reported
• The conceptual site model and risk assessment indicate exposure pathways through consumption of vegetables grown on site, consumption of meat from livestock feeding on site, groundwater exposure (in case of using groundwater as tap water), indoor air exposure and, soil exposure (mainly soil & vegetable ingestion) as depicted in the figure below
• Most important is to ‘close the tap’, remediation only makes sense when ASGM activities are stopped
• A literature study, lab experiments on biochar and phytoremediation of mercury contaminated soil performed
• Lab studies showed that local made biochar from corn cobs showed highest mercury adsorption in the soil
• The use of vetiver grass in combination with biochar in the soil showed in lab conditions lower adsorption of mercury in vetiver grass, resulting in lower mercury leachate
• Guideline document for installation and maintenance of ASGM contaminated sites. This provides a technical, local and nature based remediation solution for low-cost to contain an immobilize mercury contaminated of soil with the use of biochar and vetiver grass
• Scientific publication on effective biochar to immobilize mercury

Conceptual site modelling including the six identified pathways

Outreach & stakeholder engagement:

• Attendance to COP4 Minamata Convention
• Training Mercury & Contaminated Sites in Lombok and West-Sumbawa
• TAUW international workshop on mercury
• Presentation project at the IHPA symposium
• Social media campaign on ASGM and mercury in Indonesia
• Fieldwork and research by students within and integrated into study program Mataram University
• Methyl-Mercury analyzer provided to Mataram University by Amman Mineral

Collaboration

Within the Consortium comprising TAUW, Nexus 3, and Mataram University, along with partner Amman Mineral, collaborative efforts and expertise have been effectively combined and were as follows:

• Project lead and (local) coordination (Nexus 3)
• Scientific, field, and analytical support in Indonesia (Mataram University)
• Soil and groundwater expert and overall project support and coordination (TAUW)
• Providing a methyl mercury analyser to the Mataram University and including involvement in reducing mercury contamination and ASGM activities in West Sumbawa by Amman Mineral
• Outreach and stakeholder engagement (Nexus 3 and TAUW)

The local partners were met during site visits. While conducting fieldwork, knowledge was exchanged and cultural differences shared. This led to a general understanding of how to work together in the project and the ASGM challenges in Indonesia. Due to close contact we could continue the collaboration from a distance. The local members worked closely with local ambassadors, environmental authorities and other stakeholders to share results, knowledge and experience. The Mataram University successfully involved students in conducting fieldwork, laboratory studies, and scientific research and integrated in there programs. The team demonstrated flexibility in adjusting the project outline based on the results, which resulted in great group effort and outcomes.

Nexus 3: Our collaboration has led to a localized solution for mercury-contaminated soil by transforming agricultural waste into biochar, which effectively immobilizes mercury and the removal by using vetiver has significant impact to uptake the mercury concentration in soil. Sharing our progress at the International Conference on Mercury as Global Pollutant (ICMGP) 2024 conference allowed us to engage with the global scientific community and receive valuable feedback. While our research is currently at the lab scale, we are optimistic that this approach could benefit communities affected by mercury pollution from ASGM activities. For the future, We believe that the multi-stakeholders initiative is highly beneficial in identifying an appropriate method that may be applicable in the community to remediate mercury-contaminated sites from the ASGM activities"

Mataram University: "We, UNRAM Team, really appreciate the very good collaboration that has been built during the Mercury ASGM Project, which has succeeded in achieving a very meaningful result and outcomes for the development of infrastructure and human resources (lecturers and students) in our institution as well as for the community in ASGM areas of Sekotong (Lombok) and Taliwang (Sumbawa). In this occasion we express our highest appreciation and thanks to TAUW Foundation, Amman Mineral, and Nexus-3”