Nitrate Contamination of Drinking-water in Three Types of Crop-producing Areas in Liaoning Province

Nitrate content of 189 groundwater samples in drinking water wells on rice,corn,vegetables,three types of crop-producing areas of Liaoning province were taken investigation and analysis.The results showed that the mean value of NO-3-N content in drinking water was 4.63 mg/L in plain area of Liaoning,10.6 % of NO-3-N content in wells exceeded the MAC standard(nitrate content≥10 mg/L),and 2.1% of NO-3-N content seriously exceeded the drinking water quality standards that the National Class Ⅲ drinking water quality standards(nitrate content≥20 mg/L).Of the three types of crop-producing areas,the pollution status in corn-producing areas was the lightest,the average nitrate content was of 2.49 mg/L,the rate over MAC standard was 4.2%,and there is none of the wells in which nitrate content was above 20 mg/L,87.5% of the sampling of well water reflected good water quality;the quality of drinking water in vegetable-producing areas was relatively poor,the mean value of NO-3-N content was 4.48 mg/L,the rate over the standard of MAC and National Class Ⅲ drinking water quality were 7.1% and 1.8%,the good rate of sampling points was 71.4%;the nitrate polluted situation in drinking water of rice-producing areas was the most serious,for which 20.8% sampling wells nitrate content was over the MAC standard and 3.8% seriously exceeded the drinking water quality standards.The application of chemical nitrogen fertilizer had a direct and significant impact on the nitrate content in drinking water of different crop-producing areas in Liaoning province,between the two there were a significant positive correlation.Due to the increased use of nitrogen fertilizer,nitrate contamination of drinking water in Liaoning rice-producing areas showed a trend of deteriorating,at the same time,the nitrate content of drinking water in vegetable-producing areas reflected a decreasing trend after reducing the amount of nitrogen fertilizer in field.The nitrate content of corn-producing areas performed a slight fluctuations change,but with the increased use of nitrogen fertilizer,the pollution in drinking water had already occurred.