Abstract

Increasing environmental pollution demands precise tools to assess its effects on human health and food security. This study introduces the combined use of Total Reflection X-Ray Fluorescence (TXRF) and the effective atomic number (Z(eff)), calculated through the Compton/Rayleigh scattering ratio, as a novel and sensitive method for chemical characterization. This method was applied to the Chilean burrowing crayfish Parastacus pugnax, a widely consumed food in rural areas with high ecological, sociocultural, and nutritional relevance. Using hepatopancreas samples from 72 individuals collected across nine locations with varying anthropogenic pressure, the species was evaluated as a bioindicator for geographic differentiation and contamination exposure. Our results show that Z(eff) values differed by location, exhibiting strong positive correlations with Mn, Fe, Co, and Ca (p < 0.05, PCA/GLM), elements linked to human activity. Trace element accumulation varied significantly by sex and size, with males and larger individuals accumulating more As, Cu, and Zn, particularly in industrial zones (p < 0.05, PERMANOVA/Wilcoxon test). Although estimated daily intakes (EDI) remained within FAO/WHO limits, both non-carcinogenic (THQ) and carcinogenic (CR) risk indices exceeded acceptable thresholds in areas with intensive industrial and agricultural development, especially for Cu, Co, and Ni. These results demonstrate that Z(eff) provides a reliable geochemical indicator for both geographic traceability and pollution assessment. The correlation between metal bioaccumulation patterns in P. pugnax and anthropogenic pressures establishes this species as a sensitive sentinel for groundwater quality monitoring. This integrated approach advances an innovative framework combining TXRF spectroscopy, ecotoxicological risk assessment, and food security evaluation in vulnerable groundwater-dependent ecosystems (GDEs).