Diffuse nitrate pollution

1. Presence of nitrate ions of agricultural origin in water, with 50 mg/l being the maximum permissible concentration and 25 mg/l the guideline level. 2. This refers to the contamination of surface or groundwater due to nitrate of agricultural origin. The term "diffuse" means that this contamination does not occur at a specific point in a watercourse, such as an industrial discharge, but rather occurs spatially in one (i.e., along a river channel) or two dimensions (i.e., across a surface draining into an aquifer) and is therefore difficult to quantify.