Impact of Contaminated Sediment on the Water Quality of Typical Reservoirs

Abstract

The sediment in reservoirs is mainly derived from the sedimentation of suspended grains, such as organic particles and inorganic minerals, carried by runoff scouring from vegetation. There are three parts in this chapter: (1) Effects of pollutants released from sediment on water quality; (2) Effects of metals released from sediment on water quality; (3) Algal blooms and their impact on water quality. The decrease of the oxidation-reduction potential (ORP) in a multiphase interface under anaerobic conditions resulted in the increase of soluble ferrous hydroxide. Phosphate combining with iron hydroxide in sediment is released to interstitial water and then diffused into the overlying water. In addition, the metabolism of microbes resulted in the decrease of the ORP in anaerobic conditions, promoting the release of soluble iron in sediment and then causing the huge release of phosphorus. The release of endogenous phosphorus from sediment under anaerobic conditions resulted in the significant increase of PO 4 3À in the overlying water. The release of phosphorus from sediment depends on the conditions of the ORP. total area of 3.7 km 2 . The maximum design water depth is 32.58 m, and it has a total storage capacity of 4,480,000 m 3 . It was mainly used for irrigation at the beginning of its user, but in recent years, the reservoir has served as a drinking water source due to water shortage.A total of ten representative sampling points at the upstream, midstream, and downstream sections were selected in this study (Table 1). The surface sediment samples were collected by a Pedersen grab type sampler, sealed in the bags, and cryopreserved. The distribution of the sampling points is shown in Fig. 1.The moisture content, ignition loss, and organic content of sediment were determined in the ten sampling points (Fig. 2). The water quality of the interstitial water in sediment was further analyzed (Fig. 3).It can be seen from Figs. 2 and 3 that the differences in the moisture content in sediment are small (with an average of 43 %) due to the different geographic positions and environment conditions. The maximum sediment total nitrogen (STN) is 2.6 mg/g at sampling point S 10 , while the minimum STN is 1.4 mg/g at sampling point S 6 . The average STN is 2.1 mg/g. The maximum SOC is 5.3 % and the minimum SOC is 2.8 %, with an average of 3.8 %. The TN concentration of interstitial water at S 3 , S 6 , S 7 , and S 8 are 18.5 mg/L, 8 mg/L, 7