Modelling of Redox Conditions in the Shallow Groundwater: A Case Study of Agricultural Areas in the Poyang Lake Basin, China

Various natural and anthropogenic factors affect the formation of the groundwater chemical composition and geochemical conditions in agricultural areas. However, it is often difficult to evaluate the role of individual factors in these processes. The article is focused on the research of the alteration of redox conditions in the shallow groundwater of the Poyang Lake basin under the influence of agricultural activity with help of thermodynamic modelling. The thermodynamic modelling and field observations demonstrate that the reducing conditions result from joint effects of anthropogenic factors, organic or NH4-fertiliser usage, and proper natural conditions, such as low-level topography, which, in its turn, leads to the decrease in water exchange rate. The modelling also denotes that fertiliser usage may result in the clay minerals formation at lower concentrations of main clay-forming components in aqueous solution than the ones under natural conditions.