Integrated geological mapping and spatial distribution of heavy metal contamination with geoaccumulation index assessment in Juriya’s artisanal gold mining region, Gorontalo, Indonesia

Abs tr ac t This study investigates the geological, geochemical, and environmental characteristics of the Juriya artisanal gold mining area in Bilato District, Gorontalo Regency, spanning approximately 7.25 km² in the northern arm of Sulawesi. By integrating geological mapping, geochemical analysis, and aerial mapping technologies, this research characterizes the geomorphology, stratigraphy, and spatial distribution of heavy metal contaminants associated with artisanal mining activities, as well as assesses the socio-economic impacts on local communities. The study identifies three primary geomorphological units: Volcanic Hills, Denudational Hills, and Alluvial Plains, alongside geological formations including the Andesite Unit (Eocene-Oligocene), Diorite Unit (Middle-Late Miocene), and Alluvial Unit (Holocene). Drone and GIS mapping reveal mining sites situated near the Paguyaman River, highlighting potential contamination risks from mercury and other heavy metals. The spatial distribution analysis, utilizing the Inverse Distance Weighting (IDW) interpolation technique, reveals areas of significantly elevated heavy metal concentrations—specifically arsenic (up to 1628 ppm), cadmium (up to 7.1 ppm), chromium (up to 36 ppm), mercury (up to 151 ppm), and lead (up to 721 ppm)—in rock, sediment, and water samples collected from mining-impacted areas, with levels markedly exceeding natural baselines. This contamination, primarily attributed to the use of mercury in artisanal mining processes, poses significant ecological and health risks to the surrounding communities. The Geoaccumulation Index (Igeo) analysis further substantiates these findings, categorizing contamination levels for mercury, arsenic, and lead as extremely high, especially in areas closest to mining activities. In addition, the research estimates an average daily gold production of 3 grams per miner, providing essential income for local miners but also contributing to environmental degradation and fluctuating production challenges. These findings underscore the urgent need for sustainable mining practices that address heavy metal contamination while supporting local livelihoods, offering critical insights into the environmental and socio-economic impacts of artisanal mining in Juriya.