Source of Nitrate in Surface Water and Shallow Groundwater Around Baiyangdian Lake Area Based on Hydrochemical and Stable Isotopes

Abstract

In order to study the source of nitrate in surface water and groundwater near a domestic sewage discharge river in the Baiyangdian watershed, including the Fuhe River and Baiyangdian Lake, shallow groundwater and deep groundwater samples were collected in July 2014.Water chemistry and stable isotopes (δ2 H and δ18O) were used to study the relationship between the surface water and groundwater. δ15 N was used to explore the source of nitrate. The results show that urban and rural domestic sewage discharge to Fuhe River and then experience evaporation. Shallow groundwater is affected by the Fuhe River, Baiyangdian Lake, and lateral recharge from groundwater in the Taihang Mountain area. There are 16.7% of shallow groundwater samples exceeds the NO3- threshold for drinking water according to the World Health Organization standard. Due to the effect of self-purification capacity, the NO3- mass concentration in the Fuhe River is higher in the upstream area than in the downstream area. Due the regional water flow from northwest to southeast, the NO3- mass concentration in the shallow groundwater is higher in the south bank area than in north bank area. The shallow groundwater near the Fuhe River and Baiyangdian Lake is recharged by surface water. In addition, soil, fertilizer, and point sources are also major sources for groundwater nitrate. Urban and rural residential living and agricultural production activities are the main reasons for surface water and groundwater nitrate.