Plants as oxygenators in rivers☆

Abstract

The herbicide terbutryne was shown to act as a photosynthetic inhibitor. Using small artificial ponds, an empirical model which described dissolved oxygen changes after herbicide treatment was conducted. The model was shown to be responsive to changes in water temperature and windspeed which occurred during the experimental period and predictions from the model agreed well with the actual data. The effects of imposing various temperature and wind speed regimes on the model was investigated. Low temperatures and high wind speeds were associated with slight deoxygenation, whilst the reverse increased deoxygenation. The model was applied to the data from a small lake treated with terbutryne and good agreement was obtained between actual and predicted results. The conditions required for terbutryne application with low risk of harmful deoxygenation are low plant biomass, low temperatures and high wind speeds.