Spatial patterns, potential sources, and health risks of heavy metals in pore and fissure groundwater: A Monte Carlo-based assessment in northern Hebei, China.

In industrialized regions, groundwater contamination by heavy metals exhibits significant spatial heterogeneity and poses a sustained threat to human health. This study focuses on a typical heavy industrial agglomeration area in northern Hebei Province. Based on 199 groundwater samples, a comparative health-risk assessment is conducted for pore water (PW) and fissure water (FW) using the entropy-weighted water quality index (EWQI), positive matrix factorization (PMF), and Monte Carlo simulation. The framework enables the identification of potential contamination sources, characterization of their spatial patterns, and probabilistic assessment of associated health risks. The results indicate that localized PW samples exhibit very poor quality. These samples show a marked spatial concentration in the industrial agglomeration zone in the southeastern part of the region. In this area, significant exceedances of iron and manganese are observed. The PMF model identifies five distinct pollution sources. The geogenic dust composite source exhibits the highest contribution rate, dominated by iron and manganese, concentrated in the southeast, and controlled by natural reduction processes. Monte Carlo simulations reveal distinct health-risk patterns among population groups. Children exhibit higher non-carcinogenic risks, with a 1.23% probability of HI > 1, whereas adults exhibit higher carcinogenic risks, with a low probability (<1%) of ILCR exceeding 1.0 × 10-4. These results indicate that children are more vulnerable to non-carcinogenic effects, while carcinogenic risks are mainly associated with upper-tail exposure scenarios. This study provides a transferable approach for linking groundwater contamination sources with spatial health risks under hydrogeological heterogeneity.