The early processes of redox and phosphorus migration through simulated experiments of inundated soil column in the subsidence waters of coal mine areas

Abstract

Simulated experiments were designed to observe the processes of redox and phosphorus (P) migration in inundated agricultural soils of the Panxie Mine Areas. The goal is to address the potential of P transformation and transport from inside soils to "soil-overlying water" interface. The experiments lasted four months. Soil physical and chemical properties, such as organic matters (OM), P fractions and ion oxides, were analyzed before and after the experiments. Moreover, indicators of porewater inside the soil column concerning the important redox processes, including dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), ferric iron (Fe2+), nitrate, ammonium, phosphorus, sulfate, etc., were monitored continuously during the whole experiment period with conserved Cl- as the reference element. Microorganism redox processes were well differentiated. Nitrate and sulfate were depleted due to microbes' anoxia respiration in two weeks. Increase of Fe2+ concentrations were accompanied by the releasing of dissolved reactive phosphorus (DRP) in the porewater of the soil column. "Fe-pumping up" phenomena was observed at the late stage. NH4Cl-P (loosely absorbed P) and OP (organic P) were found to have the transform trends towards NaOH-P (hydrous metal oxides combined P) on the "soil-overlying water" interface, while P migration from bottom to surface soils cannot be verified.