Distribution characteristics, sources and risk assessment of heavy metal(oid)s in road dust from a typical lead-zinc mining area in South China

Although the construction of green mines has effectively reduced soil pollution issues, dust contaminants continue to pose potential risks to human health and environment. This study investigated the concentrations, sources, and human health risks of metal(oid)s present in road dust across different functional zones of the largest lead-zinc mine in Guangdong Province, China, namely the Fankou lead-zinc mine. First, a systematic collection of 45 dust samples from six functional zones was conducted, focusing on the concentrations of ten heavy metal(oid)s (HMs), including As, Cd, Pb, and Zn etc. The results indicate that mining and smelting activities at the Fankou lead-zinc mine dictate the accumulation and distribution of HMs in the dust across the various functional zones. Except for Mn, Cr, and Thallium (Tl), the concentrations of other HMs significantly exceed the soil background values. These HMs primarily originate from mixed sources, including natural, traffic, and industrial activities. In particular, the presence of As, Cd, Pb, and Zn in the dust resulted in moderate to severe pollution, posing extremely high potential ecological risks. Furthermore, the bioavailable concentrations of HMs in the dust were analyzed using two in vitro gastrointestinal simulation methods: Physiologically Based Extraction Test (PBET) and Simplified Bioaccessibility Extraction Test (SBET), allowing for a further assessment of metal bioavailability and estimation of (non)carcinogenic risk probabilities for humans. The bioaccessible heavy metal contents extracted through SBET and PBET were relatively low, with most samples exhibiting bioaccessibility below 40%. In comparison to the total concentrations of HMs in the dust, the estimated non-carcinogenic risks (HQ and HI) and carcinogenic risks (CR) associated with bioavailability (PBET and SBET) for As, Cd, Cu, Sb, Pb, and Zn were significantly reduced, falling within safe values for both adults and children. However, the carcinogenic risk posed by total As remains a concern for local adults and children, indicating that the potential carcinogenic risk of As should not be overlooked. Therefore, additional protective measures should be considered to reduce resident exposure to dust, particularly in the core production areas of the mining district.