Nitrate removal capacity and nitrous oxide production in soil profiles of nitrogen loaded riparian wetlands inferred by laboratory microcosms

• Published in: Soil biology & biochemistry Vol. 60; pp. 156 - 164
• Main Authors: Lind, Linus P.D., Audet, Joachim, Tonderski, Karin, Hoffmann, Carl C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.05.2013; Elsevier
• Subjects: agricultural watersheds; Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; denitrification; emissions; farming systems; Freshwater; Fundamental and applied biological sciences. Psychology; Greenhouse gas; greenhouse gases; groundwater; leaching; Nitrate; nitrates; nitrogen; Nitrogen removal; Nitrous oxide; nutrients; Physics, chemistry, biochemistry and biology of agricultural and forest soils; risk; soil profiles; Soil science; Wetland; wetland soils; wetlands; Nitrogen removal; Nitrous oxide; Nitrate; Wetland; Greenhouse gas; Gas emission; Microcosm; Nitrates; Nitrogen; Soils; Riparian; Soil science; Soil profile; Nitrogen protoxide; Denitrogenation; Denitration
• ISSN: 0038-0717; 1879-3428; 1879-3428
• DOI: 10.1016/j.soilbio.2013.01.021

Riparian wetlands located in agricultural catchments may often receive a high nitrate (NO3−) load because of the leaching of nutrients derived from upland farming activities. Nitrate can be removed in wetland soils by denitrification which is the reduction of NO3− to the gaseous forms nitrous oxide (N2O) and dinitrogen (N2). However, the release of N2O is detrimental to the environment because N2O is a potent greenhouse gas. Therefore, this study aimed at investigating the factors controlling the production of N2O and at evaluating the risk for N2O emissions from riparian wetland soils. In a laboratory setup, we simulated an upward flow of NO3− enriched groundwater through intact soil cores collected from four wetlands with contrasting soil characteristics. The results showed a rapid reduction of the NO3− fluxes, supporting the effectiveness of wetlands for removal of N. However, during the reduction of NO3− transient accumulation of N2O was observed, but the N2O concentration decreased with declining NO3− availability. In this study, the NO3− load was revealed as the only significant factor controlling both NO3− reduction and N2O production. Our results confirm the capacity of wetlands to remove large amounts of N, but it also showed that substantial emission of N2O might occur if the reduction of NO3− is not complete, a matter to be considered when diverting N rich waters toward wetlands. ► Riparian wetlands soils have the capacity to remove large amounts of nitrate (NO3−). ► High NO3− load increases the ratio between N2O production and NO3− reduction. ► Nitrous oxide (N2O) can accumulate during nitrate (NO3−) reduction in wetland soils. ► Complete NO3− reduction prevents the accumulation and the potential emission of N2O.