Hydrochemical evolution and contemporary weathering rates in a soil chronosequence, Merced, California, USA

摘要

This study presents the first detailed description of the hydrochemical evolution and contemporary weathering rates in a soil chronosequence. During 3 million years of weathering, the soils become less permeable, progressively isolating pore water solutes from climatic perturbations and increasing the importance of mineral weathering. Mass balance models describe the elemental partitioning between minerals, pore water and exchange reservoirs and the elemental fluxes from precipitation, plants, discharge and weathering. Extrapolation of present day weathering fluxes reproduces observed long-term changes in soil compositions. Plagioclase reaction rates, based on solute weathering gradients, are similar to previously reported geologic rates and are several orders of magnitude slower than experimental rates due to near-equilibrium solute conditions.