Factors contributing to nitrate contamination in a groundwater recharge area of the North China Plain

Abstract

Abstract:Nitrate contamination is a common problem in groundwater of the North China Plain (NCP) owing to overuse of fertilizers and discharge of wastewater. Accordingly, it is important to investigate nitrate contamination in recharge areas to understand the fate of nitrate in the plains area. In this study, the spatial and temporal distribution characteristics of nitrate and factors contributing to its sources and transformation in shallow groundwater of the Beiyishui River watershed, NCP, were analysed by a combination of multiple regression and multi-tracer methods. The nitrate concentration of 79% of the samples exceeded the natural environmental standard of 13.3 mg l À1 , while that of 23% of the samples exceeded the World Health Organization (WHO) drinking water standard of 50 mg l À1 . Groundwater age estimation of the hill regions based on chlorofluorocarbons (CFCs) revealed a mix of young water from 1982 to 1990 and old, low CFC water. The analysis based on the variations in land use in past years revealed that part of the grassland was converted into woodland between 1980 and 1995; therefore, the land use at the recharge time was used to determine which surface conditions influence groundwater nitrate concentrations. Multiple regression analysis showed that point source pollution contributed to the high concentration of nitrate in the hill region. Fertilizer application associated with land use change from grassland to woodland was also related to the present nitrate concentration. In the plains area, the contribution of fresh water from fault fractures and denitrification led to 31 to 72% and 6 to 51% reductions in nitrate concentrations, respectively. Our results suggested that controlling point source contamination and fertilizer input to hilly regions of the study will prevent groundwater of the plains area from deterioration in future years by mixing fresh water into the aquifers and decreasing denitrification, and therefore nitrate concentrations.

Combination of CFCs and stable isotopes to characterize the mechanism of groundwater–surface water interactions in a headwater basin of the North China Plain

“…Groundwater CFC apparent ages were determined using concentrations of CFC‐12 and CFC‐113, indicating mostly modern groundwater, subject to flow along two major flow paths—a regional pathway from the upstream mountainous areas to downstream plains and local pathways rapidly conveying water towards the river from the sides of the valley. The estimated CFC derived ages and binary mixing model are consistent with this interpretation, as well as other data collected elsewhere in the Taihang Mountains—the regional recharge area for the NCP (Wang et al, ).…”

Quantification of surface water and groundwater salinity sources in irrigated lowland area of North China Plain

“…Land use controls sources and fate of nitrate in shallow groundwater, domestic sewage from rural area and agricultural increased shallow groundwater nitrate in the head region of NCP (Wang et al, 2016). In lowland area of NCP, land use has potentially relative larger impacts on shallow groundwater salinity since the smaller groundwater depth and significant seasonal changes (Kong et al, 2018).…”

Using multivariate statistical techniques and geochemical modelling to identify factors controlling the evolution of groundwater chemistry in a typical transitional area between Taihang Mountains and North China Plain

“…Application of chemical fertilizers in agricultural activities for a long time to increase food production, is often considered as the main source of nitrate contamination in the NCP. However, few studies were focused on the current situation of nitrate contamination in the headwater basins of the western part of the NCP (Wang, Tang, et al, ). Given that the mountainous area and the western piedmont plain are the primary recharge areas of the NCP, it is urgent to identify the present status of nitrate in groundwater and driving factors in these areas, such as the HSB, to prevent nitrate pollution throughout the NCP.…”

“…Moreover, the diverse land‐use patterns and well‐developed geological structures in mountain‐plain transitional areas make the characterization of geochemical evolution of groundwater more complex. Many previous studies have shown that land‐use variation controls the distribution of nitrate in groundwater (Gardner & Vogel, ; Wang, Tang, et al, ), and geological structures can act as conduits or stagnant zones, affecting groundwater recharge and chemical evolution in such transitional areas (Chen et al, ; H. Guo & Wang, ; Y. Liu & Yamanaka, ). Various methodologies, involving ionic ratios, multivariate statistical techniques, and geochemical modelling, have been frequently applied to characterize the main geochemical processes responsible for evolution of groundwater chemistry (Karroum et al, ; Singh et al, ).…”