Hydrogeochemical processes and trace elements in sediments at the south-eastern Mexican karst aquifer

The chemical characteristics and hydrogeochemical processes that govern the groundwater in the sinkholes ring of the Yucatan Peninsula were assessed. The groundwater of the area studied is of the Ca-Mg-HCO3 type. Local geology (abundance of dolomite) determines Mg2+ enrichment relative to Ca2+. The absence of seawater intrusion was established. Sinkhole water chemistry is controlled by carbonate rock dissolution, with dominance of Ca2+, Mg2+ and HCO3-. The dynamic and controlling factors of trace elements were determined in sediments of the southern part of Mexico. The order of mean concentrations of trace elements in sediments is Sr>Pb>Cu>Zn>Cr>> Cd. With regard to the sequential extraction procedure, the potential importance of fractions in sediments is in the order residual>organic matter>carbonates>exchangeable>water soluble, confirming that sinkhole sediments works as a sink of trace elements, and that no anthropogenic pressure exists in the groundwater of the hydrogeological reserve area. Trace element stability in sediments decreased as follow: Cd>Pb>Zn>Cr>Cu>Sr. The study results describe the groundwater and sediment condition of the hydrogeological reserve area, and provide insights for stakeholders and authorities. Growing population and economic activities may be major threats to the groundwater in coming decades.