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- Grip, Harald
(författare)
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Water chemistry and runoff in forest streams at Kloten
- 1982
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Natural variability of stream water composition and discharge was studied in the Kloten area, Central Sweden, by means of statistical methods and simulation technique. The effects of Urea (155 kgN ha-1) and ammonium nitrate (AN, 160 kgN ha-1) fertilization and clear-cutting were studied by comparing treated and reference streams before and after management.The concentrations of the chemical constituents and runoff were mostly inhomogeneous in space and time and the coefficients of variation were considerable.Urea fertilization had a more prolonged nitrogen leaching and a total of 750 kgN km-2 compared with AN treated areas (500 kgN km-2). The difference was due to higher nitrate leaching. Base cation leaching was larger and pH increased after Urea fertilization. pH decreased after AN fertilization.Runoff increased 180 mm year-1 after clear-cutting, while no significant change was found after fertilization. The immediate effect of clear-cutting on stream water chemistry was an increase in dissolved organic matter, followed by increased leaching of ammonia (10x), nitrate (9x) and potassium (4.8x). The total excess leaching of nitrogen was 1 040 kgN km-2 during the first three years after clear-cutting.A Norwegian hydrochemical model, that explained stream water composition, was modified and parameterized (40 parameters) for two catchments to analyse differences between them.The differences in parameters between the catchments were interpreted as differences in slopes close to the drainage net, dilution due to different evaporation, differences in standing biomass and current annual increment and slightly different mineral composition of the soils. pH at high flows could be deduced from stand characteristics.
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- Omstedt, Anders, et al.
(författare)
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Measured and numerically-simulated autumn cooling in the Bay of Bothnia
- 1983
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Ingår i: Tellus. Series A, Dynamic meteorology and oceanography. - : Stockholm University Press. - 0280-6495 .- 1600-0870. ; 35A:3, s. 231-240
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Tidskriftsartikel (refereegranskat)abstract
- Vertical temperature profiles are analysed for the case of cooling of brackish sea water around the temperature of maximum density. Field measurements in the Bay of Bothnia cover a period of 52 days, during which the surface water was cooled from 6°C to 1.5°C. A mathematical model, which is based on the conservation equations for momentum, heat and salt in their one-dimensional forms, is presented. The equation of state is linear with respect to salinity and quadratic with respect to temperature. Turbulent exchange coefficients are calculated with a two-equation model of turbulence.The measured temperature profiles clearly demonstrate the importance of both temperature and salinity gradients in the mixed-layer dynamics. The mathematical model describes these and the general development of the temperature profile in a most satisfactory way.
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