The Aeration and Dredging Stimulate the Reduction of Pollution and Carbon Emissions in a Microcosm Study

Abstract

Sediment dredging and aeration are used as important technical measures to remediate internal loading of sediment in polluted rivers. However, previous studies have overlooked the impact of dredging and aeration on Greenhouse gases (GHGs) emission. In this study, we established three aeration rate, one dredging treatment and 6 different aeration intervals (dredging) to investigate the effect of aeration and dredging on pollutant removals and CO2, CH4 and N2O emissions (GHGs). The results indicated the pollutants and GHGs at 2.4 L·min-1, 3.4 L·min-1, 4.4 L·min-1 aeration rates reached collaborative emission reduction after more than 3 h or within 1.5 h. Meanwhile, the GHGs effluxes after aeration decreased with the increasing aeration rate, with the mean CO2, CH4 and N2O efflux of 69.74 mg·m-2·h-1, 0.16 mg·m-2·h-1, 7.53 mg·m-2·h-1 and 33.64 mg·m-2·h-1, 0.09 mg·m-2·h-1, 4.17 mg·m-2·h-1 before and after aeration, respectively. With respect to dredging, the pollutants and N2O reached synergic effects between reduction of pollution and carbon emissions after 1h dredging. Specifically, the CO2 and CH4 emissions after dredging was lower than those of before dredging, but the N2O emissions was higher than those of before dredging. In addition, the medium aeration rate has the best removal effect on nitrogen, phosphorus and potassium concentration (NH+ 4-N, AP and AK) in the sediment, and the removal rate increased with the aeration time. Our analysis revealed that the DO, ORP, AK and NH+ 4-N in the sediment influenced GHGs fluxes at the water-air interface in the aeration.

Keywords: Aeration, Dredging, Greenhouse gases (GHGs), Pollutants removals, Reduction of pollution and carbon emissions