title: Increasing lake water and sediment oxygen levels using slow release peroxide.
abstract: The sediment and hypolimnion of many Finnish lakes suffer from anoxia due to increasing nutrient loading. The aim of this research was to develop a method for increasing the oxygen level using granulated calcium peroxide (CaO₂) as a slow oxygen releasing compound. This compound releases oxygen (O₂) in a reaction with water during 5 to 7 months. The method was tested in both laboratory and field conditions. In the field test granulated CaO₂ were then spread manually from a rowing boat over the whole surface of the test pond. The granules sink onto and into the sediment. No mixing was needed. The dissolved oxygen concentration increased significantly during a laboratory experiment with a CaO₂ amendment of 75 g m⁻² and in a pond experiment with a CaO₂ amendment of 50 g m⁻². In the pond experiment, the effect was visible for the entire 40-week experiment. In the laboratory, the abundance of aerobic bacteria increased in the sediment after CaO₂ addition, while the pond experiment gave more mixed results. The organic matter content of the sediment did not change during the experiment in the control pond, but decreased from 18% to 4% in the pond with the CaO₂ amendment. This was possibly due to enhanced microbial activity in the test pond. Although the results show improved oxygen concentrations and effects on the sediment organic matter following CaO₂ amendment, the usability of this method in larger lakes remains to be tested.
authors.affiliation: Department of Environmental Sciences, University of Helsinki, Niemenkatu 73, 15140 Lahti, Finland.
authors.forename: Anne
authors.initials: A
authors.lastname: Nykänen
authors.forename: Heidi
authors.initials: H
authors.lastname: Kontio
authors.forename: Oskari
authors.initials: O
authors.lastname: Klutas
authors.forename: Olli-Pekka
authors.initials: OP
authors.lastname: Penttinen
authors.forename: Silja
authors.initials: S
authors.lastname: Kostia
authors.forename: Juha
authors.initials: J
authors.lastname: Mikola
authors.forename: Martin
authors.initials: M
authors.lastname: Romantschuk