Effects of agricultural activities on nitrate contamination of groundwater in a Yellow River irrigated region

摘要

Agricultural-induced increase of nitrate (NO_3~-) loading in groundwater is a worldwide problem. This study investigates the impacts of agricultural activities on groundwater NO_3~- pollution in a Yellow River irrigated region. The agricultural land use patterns are dependent on the land and water conditions. Besides wheat-maize rotation, the most popular cultivation pattern, other patterns with high production/ income, such as greenhouse vegetables, watermelon-cotton, are also widely adopted. N-fertilizer is excessively applied for all land-use patterns, with the annual amount ranging from 500 to 1420 kg N ha~(-1). The NO_3~- loading in groundwater has large seasonal variation mainly caused by agricultural activities. Even in the best water quality season, 4 out of 27 samples show NO_3~- concentrations in excess of the drinking water standard, with a maximum NO_3~- concentration in well water of 100 mg NO_3~- L~(-1). The shallow groundwater of the study region, combined with poor water and NO_3~- management practices, are creating a long-term legacy of contamination.