Heavy Metal Contamination and Ecological Risk Assessment in Fluvial Sediment of San Juan –Taxco River System in Mining Region of Taxco Guerrero, Mexico

Abstract

\n The hydrological system of San Juan-Taxco Rivers in located inside of one of the oldest and major mining district in Mexico. Several communities in the area use the rivers water along its flow for domestic water supply and crop irrigation. Sediment is an essential, integral and dynamic part of river basins, in polluted environments these act as sink of heavy metals and as a source of contaminants on the fluvial system. The management and sustainability of sediment should be assessed and secured to achieve good ecological status of the basins, for this task, approaches as ecological risk identification and geochemical indices are being used.Superficial sediment samples were collected in San Juan-Taxco river system. The results demonstrated that the degree of pollution from thirteen heavy metals and metalloids studied decreases in the following sequence: Cd> Zn > Pb > Cu > As > B > Mn > Ni > Fe > Co > Ba > Al and Cr. Cd made the most dominant contribution. Geochemical indices revealed important external anthropogenic influences in the rivers. The geochemical indices indicated very high enrichment for As, Cu, Pb and Zn, and extremely high for Cd in the three-rivers. The calculation of Pollution Load Index (PLI) showed in Cacalotenago River and in Taxco River are the sites with the highly contaminated sediments. PLI values were very high in all the samples sites due mining tailings erosion, wastewater and agriculture run off. Cd, Zn, Pb, Cu and As were the main potential risk elements that will cause harmful biological effects in the riverine environment.