Spatial distribution and risk assessment of potentially toxic elements in sediments from a National Park on the southern Mexican Pacific Coast

Abstract

Spatial patterns, enrichments and the ecotoxicological risks of potentially toxic elements (PTE: Cd, Cu, Pb, Zn) were evaluated in surface sediments of the Chacahua-Pastoría Lagoon System, the first tropical ecosystem designated as natural protected area along the southern Mexican Pacific Coast. With the exception of a Pb maximum in Chacahua Lagoon, only Cd (0.002-0.48 μg g^-1) and Zn (53.6-145.9 μg g^-1) showed contents above the natural level concentrations, particularly in Pastoría Lagoon. Sedimentary processes controlling PTE accumulation such as scavenging and carbonates precipitation were identified through a factor analysis. Aluminum-normalized PTE enrichment factors ranged from low to moderate, whereas using benchmark values, the risk of Cu, Pb, and Zn for benthic biota was categorized as occasional in both lagoons. In contrast, the single and potential ecological risk indices revealed a specific area of concern in Pastoría Lagoon. This assessment provides a baseline of PTE contamination and highlights environmentally sensitive areas in the Chacahua-Pastoría Lagoon System that should be prioritized in future monitoring and conservation efforts, particularly given the dependence of marginalized communities on its natural resources.

Keywords: Coastal lagoon; Potentially toxic elements; Protected natural area; Tropical environment.