Trace Element Concentration Patterns in Sediments of the Lower Rio Conchos, Mexico

Abstract

A two-step sequential extraction of B, V,Cr, Ni, Cu, and Pb in sediments from the lower RioConchos, Mexico, was used to identify sections of theriver where accumulation of these elements has takenplace. The concentrations of Mg, Fe and Al insediments were concurrently determined in order toinfer about the possible source of trace elements.According to their extractability, B and Pb werelabeled as more mobile, while Cr was the least mobile.Normalized concentration and partition coefficient(Kd) values along the lower Rio Conchos helpedidentify locations with abnormally large trace elementvalues. Sites near urban centers showed the mostaccumulation with respect to most elements, while thehighest B and Pb K_d values were found at sites farfrom urban areas and irrigation drain returns.Correlation analysis between sediment and waterconcentrations indicated a separate concentrationpattern for the sediments, most likely the result oftheir longer term element storing ability as comparedto water. In contrast, a high correlation was obtainedamong elements in sediments, with the exception of Band Pb. This study is a preliminary effort toquantitatively determine the impacts of irrigation andother human activities to the quality of one ofnorthern Mexico's most important rivers.