Copper and zinc distribution coefficients for sandy aquifer materials

Distribution coefficients (K-d) were measured for copper (Cu) and zinc (Zn) in laboratory batch experiments for 17 sandy aquifer materials at environmentally relevant solute concentrations (Cu: 5-300 mu g/l, Zn: 20-3100 mu g/l). The K-d values ranged two to three orders of magnitude (Cu:70-10,800 1/kg; Zn: 6-22,800 l/kg) and correlating them to the characteristics of the aquifer material (particle size distribution, organic C content, surface area, pH) revealed good correlation with pH in the range 5.3-8.9 (Cu: r(2) = 0.72. Zn: r(2) = 0.94). Including any other of the measured aquifer characteristics improved the correlation only a few percent. The results indicate that the mobility of Cu and Zn in sandy aquifers, as reflected in the measured K-d values, is very restricted at pH values above 6, since the relative migration velocity is less than 1%. However, at lower pH values, Zn seems to become mobile in sandy aquifers. (C) 2000 Elsevier Science Ltd. All rights reserved.