Denitrification Related to Geomorphic Process in Large Rivers

Abstract:

Denitrification is a microbial process removing dissolved inorganic nitrogen in ecosystems. Most in-stream denitrification studies focused on reach-scale denitrification in small streams and overlooked the variation of denitrification within channel. Despite of increases in channel size and geomorphic complexity in large rivers, denitrification pattern in large rivers in generally assumed similar to that in small streams. In this study, we surveyed the Cahaba River and found various denitrification rates in different locations within a large river channel. We hypothesize that the variation in denitrification rates is correlated to the distributions of benthic sediment size and organic matter content within the large river channel. Following the survey, to assess the temporal and spatial dynamics of denitrification based on what we found in large river, we mapped the channel morphology, estimated sediment spatial distribution, and developed an agent-based model that simulates nitrogen movement in the water and removal via dentrification related to sediment size and organic matter contents. This study advances our knowledge of denitrification in large rivers, and provides guidance for further field experiments on denitrification in large rivers.