The Transport of Sediments from the Cartagena-La Unión Mining District Leads to the Incorporation of Metal(loid)s into the Marine Environment

Abstract

Extraction activities can have a significant impact on the environment due to the mobilization of trace elements. These elements can pose a risk to soils, biota, water, and human health when incorporated into nearby ecosystems. To evaluate the transfer of As, Cd, Pb, and Zn from mine areas to the marine environment, a study was conducted in the Cartagena-La Union mining district (SE Spain). The study area included the mouth of a stream affected by waste materials from tailing ponds. In addition, a maritime area without mining influence was selected as a control site. Sediment samples were collected (three transects with nine sampling points and three depths) at the El Gorguel shoreline, and analyzed for pH, electrical conductivity, total metal(loid)s content, water-soluble anions, and metal(loid)s in chemical fraction distribution. Water and biota samples (Paracentrotus lividus, Patella vulgata, Hexaplex trunculus, Anemonia viridis, and Trachinotus ovatus) were also collected for metal(loid) content analysis. The results showed that the metal(loid)s concentration in the sediment increased compared to the control site, which was not influenced by mining activities. The chemical composition of metal(loid)s in the sediments revealed that Cd is the most hazardous element due to its high concentration in the labile fractions (20%), suggesting easy transfer to the marine environment. However, transfer mechanisms should be studied in various scenarios with different climatic, wave, and tidal conditions. Marine biota metal(loid)s concentrations showed an increase in specimens collected under the influence of mining activities but without exceeding limits that would affect incorporation into the trophic chain. Consequently, bioaccumulation and biomagnification processes must be considered in a future biomonitoring program.