environmental sciences research institute - University of Ulster

Brian Rippey
References
Rippey, B., N., Anderson, N. J., Renberg, I., and Tom Korsman, T., Estimating the whole-lake accumulation rate of organic
carbon, major cations, phosphorus and heavy metals in sediment, Journal of Paleolimnology, DOI 10.1007/s109330-007-
9080-x, 2007
Research into phosphorus transfers from land to water
Managing the eutrophication of fresh, transitional and coastal waters caused by excessive transfers of nutrients from land
to water remains one of the key water quality challenges of the 21st Century. In Ireland and the rest of the EU, managing
eutrophication will form part of (International) River Basin District Management Plans and Programmes of Measures
under the Water Framework Directive with a view to attaining at least ‘good’ ecological status by 2015.
The drivers of cultural eutrophication are largely excessive inputs of phosphorus (P) and nitrogen (N) from a multiplicity
of sources and each having importance according to water-body type, hydrological regime (and connectivity) and sourcemagnitude
in any given catchment or watershed.
Phosphorus is generally considered to be the greater threat to the ecological status of freshwaters, altering macrophyte
diversity and eventually oxygen regimes, macro-invertebrate and fish ecology. Nitrogen is considered to be the limiting
nutrient in transitional and coastal waters for similar reasons with the extra implications for human health impacts
resulting from excessive nitrate-nitrogen concentrations in drinking water supplies. Both nutrients have inorganic and
organic origins; the added implication of organically sourced N and P is the risk of faecal (and bacterial pathogen)
contamination in drinking water source supplies and recreational waters. The major sources can therefore be summarised
as those originating from human and animal faecal and industrial wastes and those originating from inorganic fertilisers.
These can be further categorised as originating from diffuse (non-point) or point sources in the landscape; or being
dependent on hydrological processes for transfer, or independent, respectively.
Research published by ESRI in 2007 in this area of water quality science were formed from an interlinked series of
scientific investigations centred on the NERC JIF funded Oona Water catchment hydrometeorological infrastructure, in
Co. Tyrone, under the Catchment Hydrology and Sustainable Management (CHASM) initiative.
Linking this CHASM infrastructure in projects funded by the Irish Environmental Protection Agency, Douglas et al. (2007)
investigated the spatial patterns of phosphorus and sediment transfers. The work delineated phases of non-storm and
storm transfers and highlighted the role of sediment as an influential vector of transfer from catchment soils, despite the
catchment being wholly under grassland. Results also showed the dominant role that iron (Fe) and manganese (Mn) is
likely to have in controlling particulate P transfer at the scale from 1st to nth order channels and that increasing soluble
losses with increasing catchment scale were more likely to be contributed from other, non-soil, sources – a theme that
is discussed below.
Datasets and conceptualisations of catchment processes from this work were also used in a modelling effort using
three physically distributed hydrochemistry models (SHETRAN, SWAT and HSPF). Nasr et al (2007) (University College
Dublin collaborators) showed that the partitioning of hydrometeorological processes and hydrochemical processes
within complex models could not provide a generic model structure for use in multiple catchments when validated with
extensive time-series data. Instead it was shown that HSPF provided an optimum modelling solution for hydrological
processes and SWAT a similar optimum solution for P transfers. A combination model using elements of several models
may the most effective and this work is ongoing.
Two of the several conclusions of the EPA/CHASM linked projects were firstly to work towards monitoring P transfers
at a higher resolution and secondly to identify the causes of high, ambient P concentrations during non-storm periods.
Higher resolution monitoring recognises that most nutrient transfers occur in very short time-scales – often called
the 80:20 rule – linked to high energy storm events that are difficult to monitor. Phosphorus monitoring by ion specific
probes is not technologically possible and so Jordan et al. (2007) applied a wet chemistry continuous total P (TP)
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