River sediments geochemical data as a tool to identify improper disposal of lithium-ion batteries in landfills and illegal dumps

The rapid growth in lithium-ion battery use has raised concerns about lithium (Li) and associated metal contamination resulting from improper disposal, particularly in regions lacking regulatory benchmarks and geochemical baseline values. This study presents the first basin-scale evaluation integrating background determination, spatial anomaly mapping, and contamination indexing for Li and battery-related potentially toxic elements (Co, Cu, Ni, and Pb) in fluvial sediments across the principal river basins of Minas Gerais, Brazil. A total of 3,962 stream sediment samples from ten major basins were analyzed to establish geochemical baselines, distinguish geogenic from anthropogenic inputs, and assess contamination using the modified degree of contamination index (mCd). Lithium distribution is markedly heterogeneous, with East Basin 1 and the Jequitinhonha River basin showing the highest density of anomalous micro basins. Spatial coincidence with pegmatite-hosted mineralization indicates strong geogenic control via weathering of lithium-bearing minerals. In contrast, Co, Cu, Ni, Pb, and Li anomalies exhibit limited spatial overlap, reflecting distinct geochemical pathways and lithological controls. Six micro basins in the Lower São Francisco Basin exhibit mCd values > 8 (very high to extremely high contamination). Geological sources explain elevated indices in only two cases; in the remaining areas, contamination is spatially associated with landfills and open dumps, implicating lithium-ion battery and electronic waste disposal as significant diffuse sources. By establishing lithium baseline thresholds and quantifying waste-related contamination, this study provides a methodological and regulatory framework for sediment quality assessment, environmental monitoring, and enforcement strategies aimed at controlling illegal dumping and protecting fluvial ecosystems.