Unveiling watershed-scale transport pathways of anthropogenic lithium from industrial sources

Environmental lithium (Li) inputs are expected to increase as production and use of lithium-ion batteries grow. Yet the transport and fate of human-derived Li in surface-water systems remain poorly understood. Here we investigate watershed-scale migration of Li released from industrial sources located in Jiangxi Province, China. Field surveys show that Li concentrations in river water, tap water, rice, and vegetables downstream of industrial zones are several to more than ten-fold higher than upstream background levels, suggesting increased ecological and health risks. Pathway analysis shows that natural attenuation processes, including sediment sorption, organic complexation, and biological uptake, remove little dissolved Li. In contrast, downstream transport is controlled by human-driven routing and hydrological mixing. Source-apportionment modelling showed that dissolved Li is capable of long-range transport, with industrial Li detectable up to 100 km downstream from discharge points. Agricultural activities were identified as a diffuse and low intensity source of Li, with fertilizers representing the main direct agrochemical input and pesticides making a much smaller contribution. Exposure assessment indicates that cereals and drinking water, rather than vegetables or fish, constitute the principal intake pathways; all sites with target hazard quotients (THQ) > 1.0 are situated within or immediately below industrial areas, implying potential non-carcinogenic risks for nearby residents. These new insights are critical for understanding Li pollution and developing targeted mitigation policies.