A Monte Carlo simulation-based health risk assessment of heavy metals in soils of an oasis agricultural region in northwest China

In recent years, heavy metal contamination of soils has been increasing, posing a major threat to food security, human health, and soil ecosystems. This study analyzed the spatial characteristics, contamination sources, risks of heavy metals by collecting topsoil samples from farmland in an oasis agricultural region in northwest China. The results found that soil heavy metals in farmland were at a moderate contamination level. The PMF model classifies soil heavy metals as fertilizer and pesticide sources dominated by As and Mn with 27.8 %, mixed sources of transport and agricultural sources dominated by Cu, Zn, Cd and Pb with 26.9 %, metal processing sources dominated by Cr and Ni with 22.6 %, and the combined pollution sources of Ti, V, Cr, Mn, Fe, As, Pb dominated by natural sources and fuel combustion. The noncarcinogenic and carcinogenic risks values from the ingestion route were higher for children than for adults. The non-carcinogenic risk of heavy metals to adults in the southwestern and central regions of the study area was >1 x 10-4. The carcinogenic risk was >1 in all adults, but >1 in children in the central and southwestern study areas. Monte Carlo simulation takes into account the parameters and their distributions that affect the health risk assessment model by combining the uncertainty assessment with the health risk, which will reduce the uncertainty of the health risk assessment. The results showed that conventional deterministic risk assessment may overestimate health risk outcomes. In addition, As has a 1.85% probability of non-carcinogenic risk to children, and an 85.3 % probability of total non-carcinogenic risk for children for all heavy metals. 69.5 % and 11.4 % probability of carcinogenic risk for children and adults respectively for Ni, and 96.4% and 52.1 % probability of total carcinogenic risk, suggesting that Ni is a priority control heavy metal.

Automated summary

In recent years, heavy metal contamination in soils has become a growing concern due to its potential threats to food security, human health, and soil ecosystems. This study investigated the spatial characteristics, contamination sources, and risks associated with heavy metals in farmland soil samples collected from a northwest China oasis agricultural region. The results showed that the farmland soil was moderately contaminated with heavy metals. The contamination sources were found to be mainly from fertilizer and pesticide usage, transportation and agriculture activities, metal processing, as well as natural sources and fuel combustion. The health risk assessment revealed higher noncarcinogenic and carcinogenic risks for children compared to adults, and the Monte Carlo simulation method was found to reduce uncertainty in the risk assessment model. Additionally, nickel (Ni) was identified as a priority control heavy metal due to its high probabilities of non-carcinogenic and carcinogenic risks.