Determining the sources of nutrient flux to water in headwater catchments: Examining the speciation balance to inform the targeting of mitigation measures

A - Papers appearing in refereed journals

Lloyd, C. E. M., Johnes, P. J., Freer, J. E., Carswell, A. M., Jones, J. I., Stirling, M. W., Hodgkinson, R. A., Richmond, C. and Collins, A. L. 2019. Determining the sources of nutrient flux to water in headwater catchments: Examining the speciation balance to inform the targeting of mitigation measures. Science of the Total Environment. 648, pp. 1179-1200.

AuthorsLloyd, C. E. M., Johnes, P. J., Freer, J. E., Carswell, A. M., Jones, J. I., Stirling, M. W., Hodgkinson, R. A., Richmond, C. and Collins, A. L.
Abstract

Diffuse water pollution from agriculture (DWPA) is a major environmental concern, with significant adverse impacts
on both human and ecosystem health. However,without an appropriate understanding of the multiple factors impacting on water, mitigation measures cannot be targeted. Therefore, this paper addresses this gap in understanding, reporting the hydrochemicalmonitoring evidence collected from the UK Government's Demonstration Test Catchments (DTC) programme including contrasting chalk and clay/mudstone catchments. We use data collected at daily and sub-daily frequency overmultiple sites to address: (1) How does the behaviour of the full range of nitrogen (N) species and phosphorus (P) fractions vary? (2) How do N species and P fractions vary inter- and intra-annually? (3)What do these data indicate about the primary pollution sources? And (4) which
diffuse pollution mitigation measures are appropriate in our study landscapes?
Key differences in the rates of flux of nutrients were identified, dependent on catchment characteristics. Full N speciation and P fractionation, together with dissolved organic carbon (DOC) enabled identification of the most likely contributing sources in each catchment. Nitrate (NO3-N) was the dominant N fraction in the chalk whereas organic and particulate N comprised the majority of the load in the clay/mudstone catchments. Despite current legislation, orthophosphate (PO4-P)was not found to be the dominant form of P in any of the catchments monitored. The chalk sub-catchments had the largest proportion of inorganic/dissolved organic P (DOP), accompanied by episodic delivery of particulate P (PP). Contrastingly, the clay/mudstone sub-catchments loads were dominated by PP and DOP. Thus, our results show that by monitoring both the inorganic and organic fractions a more complete picture of catchment nutrient fluxes can be determined, and sources of pollution pin-pointed. Ultimately, policy and management to bring nutrient impacts under control will only be successful if a multistressor approach is adopted.

KeywordsNitrogen; Phosphorus; Headwater catchments; Catchment characteristics; Mitigation measures
Year of Publication2019
JournalScience of the Total Environment
Journal citation648, pp. 1179-1200
Digital Object Identifier (DOI)doi:10.1016/j.scitotenv.2018.08.190
Open accessPublished as ‘gold’ (paid) open access
Funder project or codeS2N - Soil to Nutrition - Work package 3 (WP3) - Sustainable intensification - optimisation at multiple scales
FunderBiotechnology and Biological Sciences Research Council
Publisher's versionLloyd et al_STOTEN 2018.pdf
Output statusPublished
Publication dates
Online18 Aug 2018
Publication process dates
Accepted15 Aug 2018
Copyright licenseCC BY
PublisherElsevier Science Bv
ISSN0048-9697

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