[1] Univ Calif Davis, Dept Land Air & Water Resources, Davis, CA 95616 USA
[2] Natl Inst Med Res, Div Mol Struct, London NW7 1AA, England
[3] Hebrew Univ Jerusalem, Fac Agr Food & Environm Qual Sci, Dept Soil & Water Sci, IL-76100 Rehovot, Israel
[4] Queensland Univ Technol, Sch Phys Sci, Brisbane, Qld 4001, Australia
[5] Univ Calif Riverside, Dept Soil & Environm Sci, Riverside, CA 92521 USA
[6] Univ Calif Davis, Crocker Nucl Lab, Davis, CA 95616 USA