Microbial and hydrological influences on nitrate isotopic composition in an agricultural lowland catchment

Wexler, Sarah K, Hiscock, Kevin M and Dennis, Paul F (2012) Microbial and hydrological influences on nitrate isotopic composition in an agricultural lowland catchment. Journal of Hydrology, 468-469. pp. 85-93. ISSN 1879-2707

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Abstract

The interaction between microbially-mediated nitrogen cycling and catchment hydrology affects the amount and isotopic composition of nitrate exported from catchments in drainage waters. Dominant microbial and hydrological influences were investigated using δ15NNO3 and δ18ONO3 of nitrate from the Wensum catchment in East Anglia, eastern England; a 570 km2 lowland agricultural catchment. Samples were collected from catchment waters, precipitation, dry deposition, agricultural fertiliser and sewage effluent. Catchment water nitrate concentration and isotopic composition can be explained by microbially-mediated cycling of nitrogen inputs through nitrification to denitrification, resulting in a reduced nitrate load exported from the Wensum catchment. Seasonal, transient and through-year constant isotopic signals from nitrogen cycling processes reflect the influence of dynamic and stable hydrological factors. A three-member mass-balance mixing model demonstrates an increasing influence from Chalk groundwater downstream in the Wensum headwaters, and the displacement of shallow groundwater into the river by runoff explains the isotopic and hydrochemical stability seen in the river Wensum under varying flow conditions. Together this demonstrates a powerful application of a dual isotope and hydrological approach in the understanding of an agricultural catchment’s response to nitrogen loading.

Item Type: Article
Uncontrolled Keywords: nitrate,stable isotopes,nitrification,denitrification,agricultural catchment,hydrology
Faculty \ School: Faculty of Science > School of Environmental Sciences
Faculty of Science
Depositing User: Users 2731 not found.
Date Deposited: 19 Apr 2013 12:06
Last Modified: 21 Apr 2020 16:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/42212
DOI: 10.1016/j.jhydrol.2012.08.018

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