Impact of land use on shallow groundwater quality characteristics associated with human health risks in a typical agricultural area in Central China

Groundwater pollution seriously threatens water resource safety due to high-intensity land use throughout the world. However, the relationship between groundwater pollution characteristics and land use in alluvial plains is still unclear. In this study, the effects of land use on shallow groundwater quality and human health risk were investigated via two sampling campaigns in a typical alluvial plain, namely, Jianghan Plain, China. Results show that the shallow groundwater in this area was polluted by nitrogen (with average concentrations of 5.12 mg/L in the dry season and 4.46 mg/L in the rainy season) and phosphorus (0.29 and 0.13 mg/L in the two seasons, respectively). The nutrient concentrations during the dry season were significantly higher than those during the rainy season (p < 0.05). Correlation analysis indicated that the concentration of nutrients was significantly positively correlated with cultivated land and negatively correlated with water and residence, suggesting that land use patterns can affect the groundwater quality. The best buffer where land use patterns affect the total N concentration was about 1000 m for cultivated land and water, while the optimal ranges for ammonium N were about 1000 and 2500 m for the areas, respectively. For the total phosphorus, a radius of 2000 m leads to the best fitting effect on both areas. Human health risk assessment showed that the total health risk indexes in about 75% of the samples were higher than 1, indicating the potential risk of the shallow groundwater in this area to human health. The results indicate that land use patterns will greatly affect the shallow groundwater quality. Thus, adjusting the land use pattern can improve the water quality and reduce health risks. Identification and selection of appropriate management solutions for the groundwater protection should be based on not only water quality problems but also surface land use patterns.