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Other publication - Peer-reviewed, 2010

Nitrate concentrations and fluxes in the River Thames over 140 years (1868-2008): are increases irreversible?

Howden, N. J. K.; Burt, T. P.; Worrall, F.; Whelan, M. J.; Bieroza, M.

Abstract

Human activity has doubled the loading of biologically available nitrogen to the terrestrial biosphere compared to pre-industrial levels (Vitousek et al., 1997; Galloway et al., 2004; Schlesinger et al., 2006; Seitzinger et al., 2006). This has led to a sixfold increase in global fluxes of fluvial dissolved inorganic nitrogen (Green et al., 2004) contaminating surface- and groundwater as terrestrial ecosystems become increasingly nitrogen-saturated (Foster et al., 1982; Meybeck, 1982; Aber et al., 1998; Bouwman et al., 2005; Mulholland et al., 2008; Ju et al., 2009; Qiu, 2009; Worrall et al., 2009). Nitrate is one of the most problematic and widespread of water contaminants (Howden and Burt, 2008, 2009): it has been regulated on the basis of its alleged toxicity to humans (Sandor et al., 2001; Addiscott and Benjamin, 2004), but elevated fluvial nitrate concentrations and fluxes are detrimental to both river and marine ecology (Burt et al., 1993). Nitrate originates from land-based, diffuse (spatially distributed) agricultural sources due to land management (e.g. fertilizer application; Goolsby and Battaglin, 2001) or changes in land use (e.g. long-term release of soil nitrogen (N) resulting from ploughing of permanent grassland; Whitmore et al., 1992), and from discharges of sewage effluent direct to rivers (Howden et al., 2009). Inputs may also occur from nitrogen fixation in the soil, atmospheric deposition and bedrock weathering (Holloway et al., 1998). It is essential that we understand the mechanisms controlling the movement of nitrate through river basins to the oceans, such that likely impacts on river ecology, potable water supply and marine tropic status may be identified. A key and poorly understood component is identification of the timescales over which river basin-scale nitrate transport occurs. This is of interest because modelling studies (Young et al., 1976; DOE, 1986; Howden and Burt, 2008) have suggested that changes in land use could be responsible for elevated mean fluvial concentrations persisting for some decades after initial land use change.

Keywords

Nitrate; River Thames; Long-term

Published in

Hydrological Processes
2010, Volume: 24, number: 18, pages: 2657-2662
Publisher: Wiley

    UKÄ Subject classification

    Environmental Sciences

    Publication identifier

    DOI: https://doi.org/10.1002/hyp.7835

    Permanent link to this page (URI)

    https://res.slu.se/id/publ/78264