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Control of runoff chemistry by processes in the near-stream zone

Fölster, Jens (1999). Control of runoff chemistry by processes in the near-stream zone. Uppsala : Sveriges lantbruksuniv. , Rapport / Sveriges lantbruksuniversitet, Miljöanalys, 1403-977X ; 1999:5
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[Licentiate thesis]

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Abstract

The near-stream zone has been identified as an important control of runoff
chemistry. In northern forested areas, near-stream zones have been found to be both
natural sources and sinks for acidity. The near-stream zone can be a buffer against acidity
by cation exchange and sulphate reduction. Oxidation of sulphide and leaching of
organic acids are natural sources of acidity from the near-stream zone. A relatively high
pH and base saturation in the near-stream zone favours nitrogen cycling processes. Hence, the near-stream zone has a potential to control nitrogen leaching from the
catchment. Nitrogen can be retained by denitrification, microbial immobilisation and
plant uptake. On the other hand, mineralisation, nitrification and leaching of organic
matter can make the near-stream zone into a source for nitrogen to the stream water. The
geomorphology and the hydrological flow paths are likely to be crucial for the function
of the near-stream zone.

This thesis reports the results from an investigation on a small forested
catchment in central south Sweden, designed to clarify the effect of processes in the nearstream
zone on acidity and nitrogen chemistry in runoff. Both hydrological and water
chemistry data suggested that runoff was dominated by superficial ground water, which
agrees with what is commonly found in Swedish till soils. The Kindla catchment is
heavily affected by acidification with a pH in the stream water between 4.4 and 4.6.
Despite the severe acidification, there were no indications of forest decline at the Kindla
catchment that retains nitrogen in deposition efficiently. The leaching of inorganic
nitrogen was only 3% of bulk deposition. There were no indications that the nearstream
zone acted as a buffer against acidity or nitrogen leaching from upiand soils. The
main function of the near-stream zone at Kindla with respect to runoff chemistry was
rather to serve as a source for organic acids and organic nitrogen and, to a small extent,
nitrate and ammonium. The contribution of organic anions to acidity was however
overshadowed by a high sulphate concentration, except during a spring flood episode
when organic matter was flushed out. Indications of sulphate reduction in the ground
water were found but this probably had no influence on stream water chemistry.
Ammonium was almost only found during the spring flood episode, when 72% of the
annual transport of ammonium in the stream took place. Nitrate was found more
frequently, but mainly at concentrations below 100 µg L⁻¹. This nitrate probably
originated in the near-stream zone.

The results contrasted to what was found by other authors with respect to the
intluence of the near-stream zone on stream water chemistry. This would imply that
since the function of the near-stream zone appears to vary greatly between catchments,
there is a need for further catchment studies that also account for within catchment
variation in order to achieve a more general picture of the impact of near-stream zones on
runoff chemistry.

Authors/Creators:Fölster, Jens
Title:Control of runoff chemistry by processes in the near-stream zone
Series/Journal:Rapport / Sveriges lantbruksuniversitet, Miljöanalys
Year of publishing :1999
Volume:1999:5
Number of Pages:23
Papers/manuscripts:
NumberReferences
I.Fölster, J. Significance of processes in the near-stream zone on stream water acidity in a small acidified forested catchment. Manuscript.
II.Fölster, J. The near-stream zone is a source of nitrogen in a Swedish forested catchment. Submitted to Journal of Environmental Quality
Place of Publication:Uppsala
Publisher:Institutionen för miljöanalys, Sveriges lantbruksuniversitet
ISBN for printed version:-
ISSN:1403-977X
Language:English
Publication Type:Licentiate thesis
Full Text Status:Public
Agris subject categories.:P Natural resources > P01 Nature conservation and land resources
T Pollution > T01 Pollution
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Environmental Sciences (social aspects to be 507)
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Oceanography, Hydrology, Water Resources
Agrovoc terms:watersheds, runoff, forest soils, acidification, eutrophication, air pollution, sulphur, nitrogen, sweden
Keywords:watersheds, runoff, forest soils, acidification, eutrophication, air pollution, sulphur, nitrogen, sweden
URN:NBN:urn:nbn:se:slu:epsilon-e-1898
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-1898
ID Code:11177
Faculty:L - Lantbruksvetenskaplig fakultet (t.o.m. 2003)
Department:(NL, NJ) > Dept. of Environmental Assessment
Deposited By: Staff Epsilon
Deposited On:15 May 2014 09:39
Metadata Last Modified:02 Dec 2014 11:06

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