Effect of Pond Drying on Nutrient Release from Bottom Sediment in a Eutrophic Pond

Abstract

Pond drying is a traditional method for purifying water bodies; however, its effects have not been extensively studied or quantified. The inhibitory effect and mechanism of pond drying on nutrients released from sediment remain unclear. In this study, the effect of the drying period on bottom sediment and water quality was investigated experimentally and the effect of drying on nutrient released from the bottom sediment was discussed. Sediments were collected from a eutrophic pond, Lake Nanko, Fukushima Prefecture, Japan, for experimentation. The results were as follows. (1) The rate of nutrient release from bottom sediment decreased with a longer pond drying period. After 30 days of drying, the release flux reduction rate was 71% for dissolved-total-nitrogen (DT-N) and 83% for dissolved-total-phosphorus (DT-P) under anaerobic conditions. (2) The decrease in bottom sediment porosity owing to drying reduced the rate of nitrogen release from bottom sediment. (3) Drying reduced the porosity and phosphorus concentration of pore water in bottom sediment, inhibiting phosphorus release from the bottom sediment.