Heavy metal exposure and ecological risk assessment in the Guizhou snub-nosed monkey (Rhinopithecus brelichi): a fecal biomonitoring study.

Within the "One Health" framework, terrestrial wildlife serves as an effective indicator species for monitoring various pollutants, including heavy metals. In this study, we aimed to characterize heavy metal exposure in Guizhou snub-nosed monkeys (Rhinopithecus brelichi) in the Fanjing Mountain World Natural Heritage Site (FMWNHS) in Guizhou Province, China. To this end, feces samples from Guizhou snub-nosed monkeys were collected at different points within the study area and the concentrations of six heavy metals (Cd, Cr, Cu, Pb, As, and Hg) were quantified. Specifically, concentrations of Cd, Cr, Cu, Pb, and As were determined using inductively coupled plasma mass spectrometry, whereas Hg was quantified by atomic fluorescence spectrometry. The bioaccumulation characteristics, ecological risks and health risk of these heavy metals were also determined based on their bioaccumulation factors, potential ecological risk indices and hazard quotient, respectively. Spearman correlation analysis, combined with non-negative matrix factorization and positive matrix factorization, was performed to determine the sources of these heavy metals and their contributions to the observed pollution levels. The results showed significant variations in the accumulation levels of the investigated heavy metals, with Cu showing the highest accumulation and distinct enrichment characteristics, whereas As and Hg showed the lowest accumulation levels. Ecological risk indices indicated moderate to very high ecological risks, with Niujiaodong and Liujiawan identified as high-risk areas. Hg and Cd were the primary contributors to the ecological risks. However, the hazard quotient values for all study areas were below 1, indicating that exposure to these heavy metals remained within the acceptable safety threshold and posed a low potential risk of adverse health effects in Guizhou snub-nosed monkeys. Source apportionment showed that Cd, As, Pb, and Cr primarily originated from composite pollution sources, Hg from atmospheric pollution sources, and Cu from natural geogenic sources. Overall, fecal based bioaccumulation analysis provides a simple, safe, and non-invasive approach for monitoring exposure to environmental pollutants and their effects on critically endangered species. The findings of this study may also be of great significance in conservation efforts for rare and endangered species.