Study on the Characteristics of Spatial Distribution of Nitrogen, Phosphorus, Iron and Manganese in Drinking Water Sources - A Case Study of Hefei, China

Abstract This paper focuses on the characterization of the spatial distribution of N, P, Fe, Mn and pH in the soil, water bodies of tributaries and reservoirs upstream of drinking water sources, as well as in the surface sediments. The results of the study showed that the surface soil upstream of the drinking water sources in Hefei has been severely acidified. The organic agriculture should be promoted in the water protection zones to reduce the use of chemical fertilizers. pH and N showed significant negative correlation (P=0.01) in the surface soil of the study area. pH and P were not correlated in the surface soil of the study area. pH and Mn, TFe2O3 showed significant positive correlation (P=0.01) in the surface soil of the study area. Mn and TFe2O3 showed significant positive correlation (P=0.01) in the surface soil of the study area. These results showed that P is relatively stable in the surface soil, while N, Fe and Mn tend to enter water sources during the rainfall season. The deeper soil is in an alkaline environment. pH and N, P, Mn, TFe2O3 were not correlated in the deep soils of the study area. It indicates that N, P, Mn and TFe2O3 are relatively stable in alkaline soil. The chemical index of alteration (CIA) of the surface and deep soils in the study area are higher than 65, which indicates that the surface and deep soils in the study area are moderately weathered. This implies that N, P, Fe and Mn in the surface and deep soils have the possibility of entering the surface water bodies. The concentration of iron in the water body fulfills the conditions for succession from green algae to cyanobacteria. Manganese concentrations affect domestic and industrial water use. Since a large amount of water is diverted from the Pihe river irrigation to the Dongpu Reservoir every year, it is difficult to reflect the real state of water quality in two reservoirs. Therefore, the ecological measures should be taken to cover bare soil, such as the banks of river slopes are converted into ecological berms to reduce soil erosion. It is necessary to strengthen the study of the release law of surface sediments from Dongpu and Dafangying Reservoirs. It will provide scientific data for the waterworks to take water from two reservoirs in a stratified manner. It is strictly prohibited to cause surface and deep soil to be exposed by extensive excavation in water source protection zones.