Denitrification Potential of Lake Sediment at the Davis Pond Mississippi River Freshwater Diversion Site, Louisiana, USA

摘要

Denitrification potential was determined in surface sediment collected from Lake Cataouatche, the receiving basin for the Davis Pond Mississippi River freshwater diversion. Denitrification was measured in the laboratory using sediment microcosms flooded with lake water. Nitrate was added to the microcosms to achieve 1) an initial nitrate concentration similar to the mean concentration (1.4 mg NO sub(3)-N L super(-1)) in Mississippi River water, and 2) a high nitrate concentration to elicit denitrification potential (50.0 mg NO sub(3)-N L super(-1)). Mean denitrification rates in controls (no nitrate added) ranged from < 0.06 to 0.67 mg N m super(-2) d super(-1) and averaged about 0.22 mg N m super(-2) d super(-1). Denitrification potential measured at the primary sampling site (close proximity to outflow) during the most active period (days 3-10) ranged from 43.3 to 94.1 with a mean of 62.3 plus or minus 10.5 mg N m super(-2) d super(-1). Denitrification potential was about 18 times greater compared to the Mississippi River nitrate concentration denitrification rate (3.52 plus or minus 0.42 mg N m super(-2) d super(-1)). Mean denitrification potential of four secondary sites varied from 30.2 to 56.6 mg N m super(-2) d super(-1). Lake Cataouatche sediment has the capacity to remove nitrate from the water column via denitrification and could potentially remove a significant portion of nitrate inputs from the Davis Pond diversion.