Artikkelit kirjoittajalta Martti Vuollekoski
Kunnostusojituksen pitkän ajan vaikutus valumaveden ominaisuuksiin.
English title: Long-term effects of maintaining ditch networks on runoff water quality.
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The effects of ditch network maintenance on runoff water quality was studied at 23 sites in different parts of Finland. The study included a calibration period of 1–3 years before maintaining the ditches and six years after. No observations were made during winter. After ditch maintenance, which involves either cleaning of old ditches and/or digging of complementary new ditches, the concentrations of suspended solids in runoff water increased immediately. At sites where the ditches cut into fine-textured subsoil, runoff continued to have increased suspended solids concentrations throughout the whole six-year period. However, if the bottom of the ditches consisted of coarse mineral subsoil or peat, the annual mean concentration of suspended solids returned to pre-treatment levels in 5–6 years. Concentrations of mineral nitrogen, especially NH4-N, increased while the concentration of organic nitrogen decreased after ditch network maintenance. These changes persisted for the whole six-year period. The overall effect of these changes resulted in a slight lowering of total dissolved nitrogen concentrations. With the exception of a few sites, runoff water pH increased after ditch maintenance and remained high during the 6-year period. Concentrations of DOC decreased at all sites after ditch maintenance and was still at a low level after six years. Concentrations of base cations (Ca, Mg, K, Na) increased significantly after ditch maintenance and were still high after six years. High concentrations of Al and Fe immediately after the digging operations were observed in a few sites. Concentration of total dissolved P did not change much and tended to decrease rather than increase.
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Joensuu,
Forestry Development Centre Tapio, Soidinkuja 4, FIN-00700 Helsinki, Finland
Sähköposti:
ei.tietoa@nn.oo
- Ahti, Sähköposti: ei.tietoa@nn.oo
- Vuollekoski, Sähköposti: ei.tietoa@nn.oo
Vanhoilta metsäojitusalueilta valuvan veden ominaisuudet.
English title: Discharge water quality from old ditch networks in Finnish peatland forests.
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Runoff water from 75 Finnish ditch networks was sampled for chemical analysis in 1990-1992. In total, 2815 samples were analyzed. Higher mean and median concentrations of total dissolved phosphorus were observed than reported earlier. Except for phosphorus, concentration of most elements increased with increasing site fertility. No clear relationship between phosphorus concentration and the site characteristics could be detected. The median concentration of suspended solids in runoff water from old ditch networks was as low as 2.4 mg l-1.
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Joensuu,
Forestry Development Centre Tapio, Soidinkuja 4, FIN-00700 Helsinki, Finland
Sähköposti:
ei.tietoa@nn.oo
- Ahti, Sähköposti: ei.tietoa@nn.oo
- Vuollekoski, Sähköposti: ei.tietoa@nn.oo
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