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Overview of the Artisanal Small-Scale Gold Mining Process
INTRODUCTION This chapter provides an overview of the artisanal small-scale gold mining (ASGM) process, including a description of the primary contaminants released or discharged during each step of the process. This chapter also presents a general conceptual site model (CSM) for ASGM sites that identifies the transport mechanisms, exposure pathways, and routes of exposure for local populations who may be exposed to these contaminants. Problem formulation is the process of establishing study objectives, supporting the identification of data-quality objectives associated with statistical analyses, and developing a strategy for characterizing the zone of influence or community footprint associated with ASGM activities in a specific geographic area. A detailed checklist is provided to assist in developing a land-use map of the area and to refine the general CSM for the site of interest based on site-specific existing information and knowledge. The provided checklists highlight key site-specific questions or issues required to inform the selection of participating households and sampling locations at ASGM and reference sites.
DESCRIPTION OF THE ASGM PROCESS Informal small-scale ASGM activities are occurring in many low- and middle-income countries (LMICs). Figure 1.1 provides an overview of the steps involved during typical ASGM operations: • Extraction: During ore extraction, alluvial deposits (river sediments) or hardrock deposits are identified, sediment or overburden is removed, and the ore is mined by surface excavation, which can include pumping sediments from river bottoms and related activities. • Processing: In this step, the gold is separated from the ore. Processing methods vary depending upon the type of ore. Gold particles in alluvial deposits are often already separated and require little mechanical treatment. Crushing and milling are required for hard-rock deposits. Primary crushing can be 1
