Hydrogeochemical insights into the signatures, genesis and sustainable perspective of nitrate enriched groundwater in the piedmont of Hutuo watershed, China

Abstract

Groundwater nitrate contamination has been a global issue threatening water supply, especially in arid and semiarid piedmonts. An extensive hydrogeochemical investigation was performed in an intensively human-impacted semiarid piedmont in North China. Groundwater is nearly neutral to alkaline in nature with large variations of salinity. The concentration of nitrate in groundwater ranges from 4.89 mg/L to 402.40 mg/L with 64.29% of values beyond the permissible limit of 50 mg/L recommended by World Health Organization. Hydrogeochemistry changes gradually from fresh HCO3-Ca type waters to moderately saline Cl-Ca type with the increase of nitrate content in groundwater. Anthropogenic inputs from residential land usage are responsible for the nitrate enrichment and salinity increase. The Entropy-weighted water quality index value ranges from 29 to 327 with a mean of 82, and 21.43% of sampled groundwaters under the categories from medium to extremely poor quality for drinking purpose. Non-carcinogenic risks posed by nitrate, nitrite and ammonia via dermal and oral pathways were assessed for infants, children, adult females and males. The overall non-carcinogenic risk of investigated groundwaters ranges from 2.91 × 10−1 to 2.38 × 101 (mean of 4.00 × 100) for infants, 1.29 × 10−1 to 1.06 × 101 (mean of 1.78 × 100) for children, 5.74 × 10−2 to 4.70 × 100 (mean of 7.90 × 10−1) for adult females, and 4.24 × 10−2 to 3.47 × 100 (mean of 5.83 × 100) for adult males. Health risks vary but all population groups are at risk. These health threats are mainly posed by nitrate through the oral ingestion pathway, with minors being more susceptible. Therefore, measures including awareness improvement of local residents, environmental protection, differential water supplies based on water quality, and targeted water treatment are recommended to achieve sustainable groundwater resource development in arid and semiarid piedmonts.