Effect of rising atmospheric CO₂ on sediment and water ¹⁵N interactions in experimental riparian wetland

• Published in: Environmental earth sciences Vol. 70; no. 7; pp. 3185 - 3195
• Main Authors: Htar, Swe Hlaing, Zhu, Wei, Huang, Jingyu, Nkrumah, Philip Nti
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 2013; Springer Berlin Heidelberg; Springer
• Subjects: Biogeosciences; carbon dioxide; carbon dioxide enrichment; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Science and Engineering; Exact sciences and technology; Geochemistry; Geology; Hydrology/Water Resources; Isotope geochemistry; Isotope geochemistry. Geochronology; isotopes; Marine and continental quaternary; Original Article; Pollution, environment geology; sediments; Surficial geology; Terrestrial Pollution; wetlands; NO; NH; consumption; N budget; Elevated CO; production; experimental studies; carbon dioxide; stable isotopes; water body; N-15/N-14; concentration; nitrates; ammonium ion; enrichment; wetlands; dilution; riparian environment; export
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-013-2384-1

The experiment was conducted to ascertain net production and consumption rates of ¹⁵NH₄ ⁺ and ¹⁵NO₃ ⁻ for water and sediment in a wetland. This was done using ¹⁵N isotope pool dilution methodology under ambient and elevated atmospheric CO₂ concentrations in experimental riparian wetlands to obtain the gross N transformation rates. The ¹⁵N budget for sediment was also estimated. The results suggested that the differences in high proportion of ¹⁵N concentration in the overlying water body under elevated CO₂ could be attributed to the low production and high consumption rates of ¹⁵NH₄ ⁺ in sediment. The elevated CO₂ effect on production and consumption of NH₄ ⁺ decreased by 144 % (P = 0.014) and increased by 153 % (P = 0.009), respectively. Thereby, ¹⁵NH₄ ⁺ production rates are negatively related with ¹⁵NO₃ ⁻ consumption rates and this accounted for the decreases in net ¹⁵NO₃ ⁻ consumption under CO₂ enrichment in the wetland sediment by 11 % (P = 0.528). Therefore, ¹⁵NO₃ ⁻ production and consumption rates may strongly depend on NH₄ ⁺ production. Inorganic ¹⁵N and total ¹⁵N exported from sediment to overlying water body by the effect of CO₂ were 41 % (P = 0.071) and 18 % (P = 0.000), respectively. Therefore, low net ¹⁵NH₄ ⁺ production and high ¹⁵NH₄ ⁺ consumption rates under elevated CO₂ may partly explain the significant reduction of N from the sediment.