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| Titel |
Incorporating episodicity into estimates of Critical Loads for juvenile salmonids in Scottish streams |
| VerfasserIn |
E. E. Bridcut, J. McNish, R. Harriman |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 8, no. 3 ; Nr. 8, no. 3, S.366-376 |
| Datensatznummer |
250005609
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| Publikation (Nr.) |
 copernicus.org/hess-8-366-2004.pdf |
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| Zusammenfassung |
| Critical Load (CL) methodology is currently used throughout Europe to assess
the risks of ecological damage due to sulphur and nitrogen emissions. Critical acid
neutralising capacity (ANCCRIT) is used in CL estimates for freshwater systems
as a surrogate for biological damage. Although UK CL maps presently use an ANC value of
0 μeq l-1, this value has been based largely
on Norwegian lake studies, in which brown trout is chosen as a representative indicator
organism. In this study, an ANC value specific for brown trout in Scottish streams was
determined and issues were addressed such as salmon and trout sensitivity in streams,
episodicity, afforestation and complicating factors such as dissolved organic carbon (DOC)
and labile aluminium (Al-L). Catchments with significant forest cover were selected to
provide fishless sites and to provide catchment comparisons in unpolluted areas. Chemical
factors were the primary determinant with land use a secondary determinant of the
distribution of salmonid populations at the twenty-six study sites. ANC explained more
variance in brown trout density than pH. The most significant index of episodicity was
percent of time spent below an ANC of 0 μeq l-1.
An ANCCRIT value of 39 μeq l-1 was
obtained based on a 50% probability of brown trout occurrence. The use of this revised
ANCCRIT value in the CL equation improved the relationship between trout
status and exceedance of CLs. Uncertainties associated with variations in Al-L at any
fixed ANCCRIT, particularly within forested catchments, and the role of DOC
in modifying the toxicity of Al-L are discussed.
Keywords: Critical Load, Critical acid neutralising capacity, brown trout, episodes,
streams |
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