采煤沉陷积水区土壤覆水初期氧化还原反应过程与磷迁移转化的耦合研究

以淮南潘谢某采煤沉陷积水区为研究对象,通过设计室内模拟实验,对其农业耕作层土壤初期覆水条件下的氧化还原过程进行了考察.在此基础上研究了磷(P)自农业土壤内部向"水-土"界面迁移转化潜能,模拟实验持续近4个月.同时,实验采取土壤理化性质分析和孔隙水表征相结合的方法进行,土壤主要分析了淹水前后有机质含量(OM)、铁氧化物、P含量及其赋存形态等相关变化,而孔隙水则分析了pH、氧化还原电位(E_h)、溶解无机碳(DIC)和有机碳(DOC)、Fe²⁺、NO₃^--N、SO₄^2--S,较为保守元素Cl^-作为其他可变指标的参考.结果发现,研究过程中观察到了微生物活动所对应的不同氧化还原过程,1~2周后土柱内部的NO₃^--N和SO₄^2--S由于呼吸作用趋于耗竭,孔隙水Fe²⁺持续升高,并伴随着活性磷(DRP)的释放.此后整个体系氧化还原反应趋于平衡,在"水-土"界面观察到了明显的Fe"泵升"现象,弱吸附态磷(NH₄Cl-P)和有机磷(OP)有向金属氧化物结合态磷(NaOH-P)迁移转化的趋势,但孔隙水内部DRP能否向表层迁移短时间内不能确定.

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

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.