Long-term effects of dredging on pollutant distribution in sediments of a heavily polluted inflow river

In order to study the influence of pollutant diffusion in the process of reservoir environmental dredging, this paper took the Tongji-bridge reservoir environmental dredging project as an example to analyze the relationship among the reamer rotating speed, traverse speed and slurry absorption concentration, and thus determined the optimal reamer operation parameters. Besides, this paper also monitored and analyzed the impact of pollutant diffusion dispersion in environmental dredging under the condition of the optimal reamer operating parameters. The results turn out: (1)When the reamer rotating speed and traverse speed were set to 15 r/min and 15∼20 m/min, the slurry absorption concentration was higher and the efficiency of dredging was optimal at the moment. (2)Under the optimal reamer operation parameters condition, the pollutant diffusion in the horizontal direction was obviously affected by water depths. The horizontal diffusion distance was about 20m when the water depth was 15m to 20m and the horizontal was increased to be 40m in the depth of 10m to 15m. (3)Under the optimal reamer operation parameters condition, the pollutant diffusion in the vertical direction was little affected by different water depths. The peak of pollutant concentration from high to low was 1.0m above the bottom, intermediate water depth and 1.0m below the water surface.

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Sedimentary nitrogen fractions and source assignment from different inflows to a receiving lake

Zhao

Wang

et al. 2020

Water Supply

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The spatial distribution of the sediment nitrogen in ten typical estuaries of Lake Taihu was determined. A simple quantitative estimation model and principal component analysis (PCA) method were applied to find the source and major factors of estuarine sediment nitrogen loading. The average concentrations of total nitrogen (TN), organic nitrogen (Org-N), ammonium nitrogen and nitrate-nitrogen in the sediments of the ten estuaries were 1315.5, 1220.1, 82.53 and 6.45 mg/kg, with the organic fraction dominating. Results showed a significant difference for the TN concentration in sediments of different estuaries, which was mainly caused by geographical location, land use type and vegetation restoration measures. An important result was that sediment nitrogen in 80% of the estuaries was mainly originated from autochthonous algae and presettled organic matter, although there has been continuous pollution input from inflow rivers. The source estimation results found that the autochthonous aquaculture excretion, algae and hydrophyte debris and buried biodetritus accounted for 58.9% of the total nitrogen loading, which dominated the nitrogen sources compared with the pollution input. In addition, the PCA method was used to find that phosphorus loading and redox conditions were the major limiting factors affecting the distribution of inorganic and , respectively.

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Long-term effects of dredging on pollutant distribution in sediments of a heavily polluted inflow river

Cited by 3 publications

References 16 publications

Retention of nitrogen and phosphorus in Lake Chaohu, China: implications for eutrophication management

Retention of nitrogen and phosphorus in Lake Chaohu, China: implications for eutrophication management

Influence of Dredge Reamer Operating Parameters on Pollutant Diffusion in Reservoir Dredging

Sedimentary nitrogen fractions and source assignment from different inflows to a receiving lake

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