Characteristics of heavy metal concentrations and risk assessment for giant pandas and their habitat in the Qinling Mountains, China

High concentrations of heavy metals in the environment threaten the quality of ecosystems and the health of human beings and animals. Giant panda (Ailuropoda melanoleuca), which is endemic to China and a global conservation icon, has the largest density in the Qinling Mountains. This paper investigated the spatiotemporal variation of heavy metal concentrations in soil (N = 44) at the regional scale with three zones of urban areas, mountain edges, and central mountains, the temporal variation of heavy metal concentrations in three bamboo species (N = 19) and two types of feces (N = 10), and assessed the ecological risk and health risk for giant pandas and their habitat in the Qinling Mountains. The results showed that the median concentrations of studied eight heavy metals mercury (Hg), arsenic (As), copper (Cu), manganese (Mn), zinc (Zn), chromium (Cr), lead (Pb), and cadmium (Cd) in soil exceeded the background values of Shaanxi Province except Pb. The median concentrations of Hg, Zn, Cr, Pb, and Cd in bamboo surpassed the reference standard (RS) of national food safety limits in vegetables for human intake, but the concentration of Zn was within the nutrient range in the bamboo plants. Heavy metals were enriched more in feces of captive than the wild giant pandas, which illustrated either higher ingestion or lower digestibility for captive giant panda. Ecological risk assessment of soil by the geo-accumulation index (Igeo) and risk index (RI) showed strong pollution by Hg and moderate pollution by Cd. Health risk assessment by the hazard index (HI) showed a potential to strong risk for giant pandas exposed to Pb, As, and Hg. In addition, the concentrations of heavy metals in feces showed a higher exposure risk for captive giant pandas than wild giant pandas. We suggest that attention should be paid to and all effective measurements should be taken for reducing the emission of Hg, As, Pb, and Cd in the study area.