Deciphering spatio-seasonal patterns, driving forces and human health risks of nitrate and fluoride enriched water bodies in the Inner Mongolia Reaches of the Yellow River Basin, China

Abstract

The ecology and environment of the Yellow River Basin is threatened by fluoride and nitrate contamination induced by anthropogenic activity and geogenic factors. As a result, deciphering the spatiotemporal variability of fluoride and nitrate contamination in this area remains a challenge. 386 samples of surface water and groundwater from the Inner Mongolia Reaches of the Yellow River Basin were taken for this investigation. According to the results of the multivariate statistical and geostatistical analyses, the fluoride pollution was primarily discovered in the middle and lower reaches of the study area and was determined to be more severe during the dry season. In contrast, nitrate contamination was found to be more severe during the wet season while being widely distributed in groundwater and concentrated in areas with intensive agricultural activities. The primary mechanisms governing the spatial-seasonal patterns of NO3− and F− pollution were shown by the principal component analysis, isotopic, and hydrochemical diagrams. The water-rock interaction or evaporation was crucial in the enrichment of NO3− and F−. The human inputs (e.g., fertilizer or sewage) dominated nitrate contamination. Additionally, the alkaline environment played a role in the generation of NO3− and F−. The health risk assessment concluded that the threat of fluoride contamination was greater than that of nitrate contamination. Children faced the greatest health risks, followed by females and males. These findings would serve as a guide for water management and pollution control in the Yellow River Basin.