Natural removal of added N-nutrients, reactive phosphorus, crude oil, and heavy metals from the water phase in a simulated water/sediment system

Abstract

Water/sediment simulation systems were constructed by using an aquarium (0.45 × 0.29 × 0.35 m 3), filled with suitable amounts of water and sediment collected from three selected locations: Lan Hua Shan (LHS), Tai Hu (TH), and Loong Yu Tao (LYT) of the Zhujiang (Pearl River) Estuary of China in November 1992 at low-tide period. The salinities of the water samples collected from LHS, TH, and LYT were found to be 0.2, 4.6, and 16.2 g L −1, respectively. Known amounts of ammonium, nitrate, nitrite, reactive phosphorus, crude oil, arsenate (III), cadmium (II), chromium (III), copper (II), and zinc (II) were added as pollutants into each of the water/sediment simulation systems. The rates of the natural removal of each added pollutant in all water/sediment simulation systems were studied by monitoring their concentrations at various intervals in the investigation period. Except for Cr (III) and reactive phosphorus in the water/sediment systems of the LHS, TH, and LYT sites, and nitrate in the TH and LYT sites, the concentrations of the added pollutants in the water phase of the studied systems under a flow-condition simulation were reduced to 8% or less of the corresponding added amount on or before the 12th day by natural processes. The rate of self-purification and the estimated assimulative capacity of each added pollutant in all water/sediment simulation systems is discussed.