This paper is the result of groundwater contamination assessment.

Objective Nitrate pollution of groundwater in Jianghan Plain has attracted considerable attention. Nitrate in groundwater from the recharge areas surrounding the plain is one of the important sources. Identifying the origins of nitrate in these recharge zones is critical for the sustainable development, utilization, and protection of groundwater resources in the Jianghan Plain.

Methods The research was conducted in the northeastern margin of the Jianghan Plain. This study investigated the sources of nitrate in groundwater and the factors influencing its distribution base on geostatistics, hydrochemistry, hydrogen, oxygen and strontium isotope.

Results The results show that the cations of groundwater are dominated by Ca²⁺ and Na⁺, and the anions are predominantly HCO₃⁻. The main hydrochemical type is Ca·Mg−HCO₃ type, with10 groundwater samples showing NO₃ type. Nitrate constitutes the primary form of dissolution inorganic nitrogen in groundwater. The groundwater with high concentration nitrate is mainly distributed in the transitional zone between hilly areas and the southern sloping field. The principal recharge source of groundwater is atmospheric precipitation. Enrichment of heavy hydrogen and oxygen isotope in surface water indicates strong evaporation. Groundwater chemistry is mainly controlled by silicate dissolution,evaporation, redox processes and agricultural activities.

Conclusions The findings reveal that nitrate in groundwater primarily originates from agricultural fertilizers, followed by mineralization of soil organic nitrogen, as well as manure and domestic sewage. Agricultural activities in the areas surrounding the Jianghan Plain contribute substantial nitrogen input to the groundwater in the plain, posing potential health risks. It is recommended that management of agricultural non−point source pollution in the recharge area around the Jianghan Plain should be strengthened.