Levels of Accumulation and Release Mechanism of Pollutants in Sediments of Lihe River as a Water Conveyance Canal

Lihe River as an important water conveyance canal of diversion project from Luanhe River to Tianjin should convey 40-50 m³/s water in each spring and autumn. With the variation of water discharge, the sediments with poor viscosity and great suspension capability were very prone to re-suspension and pollutants release easily. In order to study the effects of pollutants release in sediments on river during water diversion period and set out proper protection scheme to prevent the second pollution, experiments were done to make clear the levels of accumulation and release mechanism of pollutants in sediments. First, compared with those in Haihe River, Wulihu Lake and Xuanwuhu Lake, the average content of organic matters of sediments in Lihe River was 0.21%, lower obviously, TP with the average value of 5.18 mg/kg was much higher, while TN reaching 2.99 mg/kg, a little higher than others. Second, water diversion indeed made pollutants in sediments release quickly and threaten water quality seriously. TN was the main pollutant, a high level in both river and sediments, which kept releasing with the maximum release amount of 9.16 g/m² and intensity 4.2 g/m²/d and had a great negative influence. TP and Fe with the maximum release amounts were 0.248 g/m² and 1.7 g/m² with maximum release intensities of 0.248 g/m²/d and 1.7 g/m²/d respectively. They released fast and deposited also fast, and were the potential pollutants and the release amounts could not be neglected during the initial water diversion period.