Nitrogen isotope hydrochemistry and denitrification within the Chalk aquifer system of north Norfolk, UK

Feast, N. A., Hiscock, K. M. ORCID:, Dennis, P. F. ORCID: and Andrews, J. N. (1998) Nitrogen isotope hydrochemistry and denitrification within the Chalk aquifer system of north Norfolk, UK. Journal of Hydrology, 211 (1-4). pp. 233-252. ISSN 0022-1694

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Although there has been much debate over the potential health risks of nitrate in drinking water, there is a real issue of the costs associated with removing nitrate from drinking water supplies. In the Chalk aquifer system of north-east Norfolk, modem contaminants of a mainly agricultural origin produce high levels of nitrate (> 15 mg/l NO3-N) in the unconfined valley areas, whereas in confined regions the levels of nitrate are low and commonly below detection limits (< 0.04 mg/l NO3-N). To understand the source and fate of nitrate within this aquifer system, a detailed hydrochemical sampling programme has been completed in the River Bure catchment. Nitrogen isotope values (δ15N) for nitrate within the unconfined and semi-confined zones range between + 4‰ and + 10‰, characteristic of nitrified soil organic nitrogen. However, many Chalk groundwaters possess high N2/Ar ratios (39-72) indicating a significant contribution to dissolved N2 from denitrification. Denitrification is believed to be occurring within the overlying glacial deposits, providing a mechanism for naturally improving groundwater quality. δ15N values of low-nitrate groundwaters from the confined zone are isotopically light (-3‰ to + 4‰), inconsistent with an origin from denitrification: it is suggested that these waters have a pre-anthropogenic nitrate signature.

Item Type: Article
Additional Information: Funding Information: Nick Feast particularly wished to thank the late John Andrews for his kindness in allowing the dissolved gas work to be undertaken in his laboratory at the University of Reading and Gavin McNeill and Jason Poole for their assistance, Paul Mansfield is acknowledged for his help with the column experiments. The Natural Environment Research Council supported this research via studentship GT/4/92/P to Nick Feast. Local landowners are thanked for their generous help with groundwater sampling as well as staff at the Environment Agency (Anglian Region) and Anglian Water Services Ltd. The views expressed in this paper are entirely those of the authors. John Tellam and George Wilson are thanked for their constructive reviews of this paper.
Uncontrolled Keywords: chalk,denitrification,groundwater,nitrate,nitrogen isotopes,water science and technology,sdg 3 - good health and well-being,sdg 6 - clean water and sanitation ,/dk/atira/pure/subjectarea/asjc/2300/2312
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 11 Oct 2022 11:32
Last Modified: 24 Oct 2022 07:33
DOI: 10.1016/S0022-1694(98)00245-5

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