Temperature Coefficient for Modeling Denitrification in Surface Water Sediments Using the Mass Transfer Coefficient

Watershed modeling has become an important tool for researchers. Modeling nitrate transport within drainage networks requires quantifying the denitrification within the sediments in canals and streams. In a previous study, several of the authors developed an equation using a term called a mass transfer coefficient to mathematically describe sediment denitrification. This equation takes into account the effect that water column nitrate concentration and flow depth have on denitrification in the sediments. Water column temperature also has a marked effect on the rate of denitrification in the sediments. In the present study, a relationship between denitrification rate and temperature was developed. This relationship was inserted into the original mathematical relationship to improve its ability to predict nitrate removal due to denitrification within drainage networks. The modified equation was tested by comparing predicted and measured nitrate concentrations over time in denitrification tanks at various temperatures. Results show that the modified equation increased the accuracy of predicting nitrate removal by denitrification in drainage canals. Overall Nash-Sutcliffe model efficiency values ranged from 0.72 to 0.76 for the original equation and from 0.90 to 0.97 for the equation developed in this study. The effective temperature range for the equation is 0 degrees C to 40 degrees C. The equation has also only been tested under stagnant/low-flow conditions.