Impact of Elevated Copper on the Rate and Gaseous Products of Denitrification in Freshwater Sediments

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Abstract
Application of Cu-containing algicides to water reservoirs for algal control leads to sediment Cu enrichment, but the impact of Cu accumulation on the NO3 −-attenuation capacity of these ecosystems is uncertain. With the knowledge that the reduction of N2O to N2 is mediated by a Cu-dependent enzyme, it is hypothesized that an inverse variation exists between Cu availability and the mole fraction of N2O (FN2O) in denitrification products. A study was conducted to test this hypothesis and also to assess the impact of elevated Cu on nitrification and denitrification. Sediments were collected from areas untreated (NCT) and treated (CT) with the algicide cutrine (Cu ethanolamine) in three central Indiana reservoirs, and were assayed at both in situ Cu content and after amendment with CuSO4 Results showed that Cu addition had a depressive, but short-lived effect on the processes investigated, with nitrification being most sensitive. Past cutrine treatments did not significantly affect either denitrification or FN2O However, a significant difference (P < 0.04) among reservoirs was found with respect to denitrification (Eagle Creek: 3.2; Geist: 1.6 and Morse: 4.2 mg N kg−1 h−1) and FN2O (0.51, 0.24, and 0.31, respectively). Negative relationships (r 2: 0.30–0.64) between FN2O and water extractable Cu were found only when the analysis was conducted separately for each reservoir, suggesting that Cu solubility is controlled by sediment properties specific to each reservoir. Overall, results of this study indicate that neither the NO3 −-removal capacity of sediments nor the composition of denitrification N gases is affected by past treatments with cutrine. Copyright © 2009. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
Funding Information
  • Indiana University-Purdue University Indianapolis