Abstract
The community of Randublatung basin and its surroundings (Grobogan, Blora, and Bojonegoro Regencies) using groundwater for agricultural, farming, and daily needs. However, these activities can contaminate the groundwater through nitrate and chloride in fertilizers, pesticides, animal waste, and household waste. Therefore, it is crucial to know the amount of nitrate and chloride content in the groundwater of The Randublatung basin and its surroundings. This research aims to analyze nitrate and chloride content and the ratio between ions in the groundwater of The Randublatung basin and its surroundings to find contaminant resources. The method to analyze the nitrate and chloride content is using Ion Chromatography. The analysis result from 35 samples of groundwater shows that the average nitrate content in dug wells samples is 10.06 mg/L, while the average from pump wells is 6.31 mg/L. The average chloride in dug wells samples is 43.65 mg/L, and the average from pump wells is 54.57 mg/L. These nitrate and chloride level are still in safe category based on Health Ministry Indonesia and WHO. The nitrate: chloride ratio in dug wells is 1:5, 1:9 from pump wells. The ratios indicate that the nitrate’s resource is associated with the on-site sanitation and will increase if there is no mitigation action to the contaminant resource.