QUANTIFYING DENITRIFICATION RATES IN A BIOMASS PRODUCTION AND NUTRIENT RECOVERY SITE

Fertilized agricultural lands are a major source of nutrient contamination in the Mississippi River basin. Excess nutrients in groundwater and surface water systems create zones of hypoxia, a critical lack of oxygen, disrupting ecosystems and biodiversity. This study is part of an ongoing project aiming to use bioenergy crops as buffers to reduce nutrient runoff and leachate in agricultural settings, specifically focusing on nitrate (NO₃) reduction. The primary mode of NO₃ reduction in this project is through uptake by shrub willows (Salix spp.). However, there are other processes, such as denitrification, which also reduce NO₃ concentrations and need to be accounted for. Denitrification is an anaerobic microbial process which reduces NO₃ to nitrous oxide (N₂O), dinitrogen (N₂), nitrite (NO₂), and nitric oxide (NO). This study aims to measure denitrification rates through collecting soil samples and performing a denitrification enzyme activity (DEA) assay. This process is used to quantify how much N₂O, a primary product of denitrification, the soil sample emits over time. Denitrification rates will be analyzed spatially and compared with pH, NO₃ content, and total carbon content, primary factors influencing rates of denitrification. Quantifying denitrification rates will help to gain a more comprehensive understanding of the nutrient reduction mechanisms in place at the study site.