The Effects of Particulate Organic Carbon Quantity and Quality on Denitrification of Groundwater Nitrate

Background/Need: Groundwater nitrate concentrations are elevated and rising in many aquifers throughout the world, including those in Wisconsin. Elevated nitrate concentration in groundwater can lead to human health problems and can contribute to eutrophication in river networks and coastal ecosystems. Many comparative studies have shown that denitrification rates are positively related to organic carbon quantity in soils and sediments. However, there have been few manipulative studies in field settings that have addressed how organic carbon quantity and quality affects denitrification and nitrate retention in groundwater. The overall objective of the research project was to determine how particulate organic carbon (POC) quantity and quality influences groundwater nitrate removal and retention in stream sediments.
Objectives: The study was conducted in two phases. Phase I included an experimental manipulation of POC quantity and Phase II included an experimental manipulation of POC quality. The main objective of Phase I was to determine how the quantity of POC in sediments affected denitrification and nitrate retention in shallow groundwater. The main objective of Phase II was to determine how the quality of POC affected denitrification rate, nitrate retention, and dissolved organic carbon (DOC) production and quality in shallow ground water.