Improvement Effects of Flue Gas Desulphurization Gypsums on Saline-Alkaline Soils from Open-Pit Coal Mine Dumps in Inner Mongolia
In view of soil salinization and barrenness in open-pit coal mine dumps,two sets of tests,leac-hing in soil columns and potting,were set up to explore effects of flue gas desulphurization gypsums(FGD gypsums)with different additive amounts(0,1,2,3 and 4 kg/m2)on physicochemical properties and fer-tility enhancements of saline-alkaline soil.The waste FGD gypsum generated from a power plant in the coal mine area was used as a soil amendment,while saline-alkaline soil was taken from an open-pit coal mine dump as a salinized soil substrate.Astragalus adsurgens,a local plant in semi-arid areas in Inner Mongolia,was used as a test object.Results showed that the soil pH values in the two groups significantly reduced after the application of FGD gypsums,indicating that FGD gypsums can effectively reduce soil al-kalinity through neutralization;when the additive amount of FGD gypsums was less than 2 kg/m2,con-tents of Na+ and HCO-3 in soils of the two groups decreased with increasing additive amounts of FGD gyp-sums,which indicated that moderate application of FGD gypsums can increase ion exchange activities of the soil,so that large amounts of Na+ and HCO-3 resulted in precipitation out of the soil surface,and e-ventually reduction in soil salinity.Therefore,FGD gypsums had a significant effect on salinized soil im-provement;when the additive amount of FGD gypsums was less than 2 kg/m2,contents of available nitro-gen(AN)and available potassium(AK)of the two groups increased notably with increasing additive a-mounts of FGD gypsums,indicating that moderate application of FGD gypsums can significantly increase contents of effective nutrients in soil,which was conducive to soil infertility alleviation and improvement in fertility level of the salinized soil.When the FGD gypsum was applied at 2 kg/m2,the seed germination rate,plant height,root length,biomass,root biomass and carbon and nitrogen ratios of Astragalus ad-surgens in potting tests reached their maximums respectively,while the seedling survival rate was close to the maximum,which indicated that FGD gypsums were effective in ameliorating the salinization of soils in open-pit coal mine dumps,and 2 kg/m2 was the optimum additive amount of FGD gypsum.
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