Is groundwater flow a controlling factor of denitrification process?

Abstract

Denitrification is one of important processes of nitrate attenuation in groundwater. We reviewed published studies on effect of groundwater flow conditions for the denitrification and discussed future directions of this study topic. The results were summarized as follows: 1) significant denitrification zone in groundwater flow system mainly corresponds to discharge area of shallower groundwater including topographic transition area and deeper aquifers (both confined and unconfined aquifers), 2) residence time of groundwater controls the amount of nitrate removed from the groundwater flow system by the denitrification process, 3) groundwater velocity (e.g, Darcy flux) might be a critical factor controlling occurrence of the denitrification in the flow system. On the basis of these results, we conclude that a future direction of the research topics is the quantification and scale-up of the quantitative evaluation of the denitrification process by considering spatial and temporal variations in groundwater flow conditions. For the quantification, estimation of critical velocity of groundwater required for controlling the denitrification would be important. For the scale-up of the quantitative evaluation, it would be necessary to clarify the relation between geographical factors such as topographic gradient and the denitrification in groundwater.