Abstract:
In the present, agriculture productions have increased continuously and industrial growth, contributing to insufficient for surface water purposes. Therefore, the trend of groundwater usage is increasing, leading to the decrease in groundwater level. In addition, the quality of groundwater is inappropriate for consumption due to the contaminated groundwater chemistry from anthropogenic activities, especially nitrate contamination. The aim of this study is to find the factors and mechanism affecting to the concentrations of nitrate in groundwater in the intensively agricultural areas. The groundwater samples from Huai Sai royal development, Phetchaburi Province were collected from 66 groundwater wells in October 2014 (rainy) and February 2015 (summer) with different types of geological characteristics and land use. The results showed that nitrate concentration from two groundwater wells were relatively higher than groundwater quality standard in rainy season (<45 mg/L as NO3). The nitrate concentrations were 46.85 and 49.74 mg/L NO3 in the Quaternary Floodplain Deposits (Qfd). In summer, there were not found to exceed the groundwater quality standard. Moreover, the results indicated that the highest of nitrate levels in rainy and summer seasons were found in discharge areas. According to the spreadsheet model, the results revealed that the concentrations of nitrate in soil layer, rainfall infiltration and the groundwater flow process in the aquifer effects on nitrate concentrations in groundwater.