Quantify the effects of groundwater level recovery on groundwater nitrate dynamics through a quasi-3D integrated model for the vadose zone-groundwater coupled system

Yongge Zang; Xiaoshu Hou; Zhiping Li; Peng Li; Ying Sun; Bowei Yu; Miao Li

doi:10.1016/j.watres.2022.119213

Quantify the effects of groundwater level recovery on groundwater nitrate dynamics through a quasi-3D integrated model for the vadose zone-groundwater coupled system

Water Res. 2022 Nov 1:226:119213. doi: 10.1016/j.watres.2022.119213. Epub 2022 Oct 6.

Authors

Yongge Zang¹, Xiaoshu Hou², Zhiping Li³, Peng Li³, Ying Sun³, Bowei Yu⁴, Miao Li⁵

Affiliations

¹ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; State Environmental Protection Key Laboratory of Simulation and Control of Groundwater Pollution, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; School of Environment, Tsinghua University, Beijing, 100084, China.
² Chinese Academy of Environmental Planning, Beijing, 100012, China. Electronic address: houxs@caep.org.cn.
³ Beijing Institute of Hydrogeology and Engineering Geology, Beijing, 100195, China.
⁴ Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
⁵ School of Environment, Tsinghua University, Beijing, 100084, China. Electronic address: miaoli@tsinghua.edu.cn.

PMID: 36240711
DOI: 10.1016/j.watres.2022.119213

Abstract

Groundwater level (GWL) recovery in some semiarid regions, attributed to mitigation countermeasures for groundwater depletion, potentially causes nitrate accumulated in the vadose zone to be introduced into the aquifer. However, the extent to which GWL recovery affects interactions between the vadose zone and saturated aquifers, migration pathways of soil nitrogen and groundwater nitrate dynamics have not been explicitly determined. This study established a quasi-3D feedback model for the vadose zone-groundwater coupled system in a typical GWL recovery area and quantitatively evaluated the effects of GWL recovery on nitrate-N leaching fluxes via the vadose zone and groundwater nitrate-N dynamics. Within the framework of the integrated model, both the water/contaminant leaching fluxes and the depth to groundwater were exchanged at each flow time step. The obtained results reveal that the temporal changes in nitrate-N leaching fluxes depended on the behaviors of precipitation, farmland irrigation and lithology of the vadose zone, while its spatial patterns were determined by both the GWL undulation and the vertical profiles of nitrate-N content. Furthermore, the GWL recovery caused the magnitude of the nitrate-N leaching fluxes into the aquifer to increase by 44.4%. Along with the GWL recovery, the phreatic aquifer volume increased by 7.47%, and the nitrate-N mass herein increased by 40.06%, which was largely driven by the nitrate-N leaching flux. Consequently, the average groundwater nitrate-N concentration in the GWL recovery region increased by approximately 2.4 mg/L, apart from the artificial recharge route. This finding suggests that the intensified leaching of soil contaminants, given the circumstances of GWL recovery, has a negative effect on groundwater quality. An appropriate groundwater management scheme is therefore urgently required to achieve an optimal balance between GWL recovery and groundwater environment.

Keywords: Groundwater level recovery; Groundwater nitrate; Nitrate accumulation; Nitrate leaching flux; Vadose zone-groundwater coupled system.

MeSH terms

Environmental Monitoring
Groundwater*
Nitrates / analysis
Nitrogen Oxides
Soil
Water Pollutants, Chemical* / analysis

Substances

Nitrates
Water Pollutants, Chemical
Soil
Nitrogen Oxides