Three-component waterborne silicone antifouling coatings, which could cured at room temperature, were prepared, respectively, with cationic (stearyl trimethyl ammonium bromide) or anionic (sodium dodecyl benzene sulfonate) silicone emulsion as a film-forming substance, γ-methacryloxypropyltrimethoxysilane as a curing agent and dibutyltin dilaurate as a catalyst. The effect of emulsifier on the structure and properties of silicone coating was studied. The results showed that the coating with cationic silicone emulsion had high crosslinking density, and its surface is smooth. The surface of the coating prepared by the anionic silicone emulsion is rough. Emulsifier type had no obvious effect on the surface free energy of the waterborne silicone coating. The coatings have the characteristics of low surface energy and excellent bacterial desorption properties. Stearyl trimethyl ammonium bromide in the cured coating can reduce the adhesion of marine bacteria on the coating surface. Both the emulsifiers can inhibit the activity of Navicula Tenera. The waterborne silicone coating prepared by cationic silicone emulsion has better comprehensive mechanical properties and antifouling performance.
In some coal mining areas, the soil will gradually sink and collapse due to underground gouging and form water areas with rainfall, and the mercury and methylmercury accumulated in the soil will enter the water environment and become potential mercury pollutants source. Therefore, in order to understand the temporal and spatial distribution characteristics of mercury in soil under the influence of coal mining activities, total mercury and methylmercury in the soil of subsidence areas located in Huainan, China with different subsidence years were collected and tested. The results show that longer the subsidence years in the soils of different mining areas, lower the methylmercury and mercury methylation rate. In the same mining area, the methylmercury and mercury methylation in the soil will slowly increase with the subsidence time. The total mercury and methylmercury in cultivated soil around the mining area are only close to half of the uncultivated topsoil. The total mercury in farmland soil is mainly concentrated in the topsoil. At the same time, the total mercury continues to decrease with the increase of soil depth. The methylmercury in different farmland soils has a similar trend of methylmercury with the increase of depth, and all peak at the same depth. We find that the main reason is that soil subsidence affects the distribution of soil particle size in depth and then affects the internal structure of soil. This research can provide reference materials for future research on the methylation reaction of mercury in the bottom sediments of subsidence waters.
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