J Environ Sci (China). 2026 May;163:512-521. doi: 10.1016/j.jes.2025.09.011. Epub 2025 Sep 10.
ABSTRACT
High groundwater nitrate associated with agricultural activity is a global environmental problem. However, linking spatial variability of groundwater nitrate and agricultural activity quantification needs to be elucidated. This paper seeks to explain the spatial variability of groundwater nitrate in the loess area of Tongchuan City, China, identify the contributing factors using hydrogeochemical and statistical methods, and analyze the connection between farmland leaching and groundwater nitrate quantitatively. Results indicate that the nitrate of the Quaternary alluvial pore water (QAP) is significantly higher during the wet season (3.60 to 68.24 mg/L) compared to the dry season (3.53 to 37.20 mg/L). QAP nitrate is significantly higher than that in loess fissure-pore water (LFP), which ranges from 0.66 to 5.47 mg/L during the wet season and 0.82 to 5.01 mg/L during the dry season. The thin and loose vadose zone of QAP makes the aquifer particularly susceptible to anthropogenic influences. Following recharge from LFP, the hydrochemical parameters in QAP increased by 1.22 to 3.12 times (except Na+ and pH), the change of average nitrate concentration in QAP (10.11 mg/L) was considerably higher than that in LFP (0.03 mg/L) due to farmland leaching. A significant correlation (R2 = 0.70 exists between groundwater nitrate and farmland leaching in river valleys and on slopes where farmland is prevalent. Fertilizer accumulation in river valleys enhances downward leaching, thereby further exacerbating groundwater nitrate. These findings highlight that river valleys with extensive farmland in the Loess Plateau should be prioritized for preventing and controlling groundwater nitrate pollution from agricultural activities.
PMID:41887870 | DOI:10.1016/j.jes.2025.09.011
