Heavy metal pollution characteristics and health risk evaluation of soil around a tungsten-molybdenum mine in Luoyang, China

Abstract

Heavy metal pollution in mining area soil and its impact on human health have been becoming one of the most important global environmental problems. This study investigated the heavy metals in the soil around the tungsten-molybdenum mining area in southwestern Luoyang, Henan Province, assessed the level of heavy metal pollution in the soil around the tungsten-molybdenum mining area, and quantified the risks of these pollutants to human health. To assess these potential threat levels, The pollution index, potential ecological hazards and health risk assessment methods recommended by the United States Environmental Protection Agency (USEPA) are applied. The results indicated that the average soil content of the heavy metals Zn, Cr, Cd and As exceeded the soil pollution risk screening value. The Nemerow comprehensive pollution index (PN) was greater than 3, which indicated severe pollution. The potential ecological risk index (RI) of each sampling point was integrated in the order $${\\mathrm{RI}}_{\\#7}$$ RI # 7 > $${\\mathrm{RI}}_{\\#6}$$ RI # 6 > $${\\mathrm{RI}}_{\\#5}$$ RI # 5 > $${\\mathrm{RI}}_{\\#3}$$ RI # 3 > $${\\mathrm{RI}}_{\\#4}$$ RI # 4 > $${\\mathrm{RI}}_{\\#2}$$ RI # 2 \u2009>\u2009 $${\\mathrm{RI}}_{\\#1}$$ RI # 1 . Among the heavy metals, Cd posed the greatest ecological threat, accounting for 91.32% of RI. The effect of heavy metals in soil on the single non-carcinogenic health risk index (HQ) and non-carcinogenic total index (HI) through three exposure pathways, oral intake\u2009>\u2009skin contact\u2009>\u2009respiratory inhalation, was $${\\text{HQ}}_{{{\\text{Zn}}}} {\\text{ < HQ}}_{{{\\text{Cu}}}} {\\text{ < HQ}}_{{{\\text{Cd}}}} {\\text{ < HQ}}_{{{\\text{Pb}}}} {\\text{ < HQ}}_{{{\\text{Cr}}}} { < 1}$$ HQ Zn < HQ Cu < HQ Cd < HQ Pb < HQ Cr < 1 . The sum of $${\\mathrm{HI}}_{\\mathrm{Pb}}$$ HI Pb and $${\\mathrm{HI}}_{\\mathrm{Cr}}$$ HI Cr accounted for 92.96 and 92.98% of adults and children, respectively. In addition to the inhalation route $${\\mathrm{CR}}_{\\mathrm{Cd}}$$ CR Cd , $${\\mathrm{CR}}_{\\mathrm{Cr}}$$ CR Cr and $${\\mathrm{CR}}_{\\mathrm{Cd}}$$ CR Cd in the study area were higher than the maximum acceptable human-level recommended by the U.S. EPA (10 –6 ), and the CR and TCR were higher in children than in adults. Therefore, the heavy metal pollution of soils in the studied tungsten-molybdenum mine area was found to pose a serious threat to the surrounding ecological environment and residents’ health.