Effect And Safety Evaluation Of Desulfurized Steel Slag In Improving Saline Alkali Soil

Saline-alkaline soil is an important potential cultivated land resource,and its area of in my country is large and widely distributed.It is a good choice to improve saline-alkaline soil and apply desulfurization by-products.Desulfurized slag is a desulfurization by-product of industrial flue gas desulfurization.Its main components are similar to the traditional saline-alkaline soil amendment desulfurized gypsum.It is predicted that it can be used as a saline-alkaline soil amendment.In this paper,the field experiment was carried out in Inner Mongolia,and alfalfa(Medicago sativa L.)was selected as the test plant to analyze and study the improvement of the salty alkali soil by desulfurized slag.In addition,the pot experiment was conducted to analyze the improvement effect and mechanism of the physical and chemical properties and microbial community structure,and evaluate the risk of heavy metals in order to explore the feasibility of desulfurization slag as an amendment of saline alkali soil.The main results are as follows:(1)Desulfurized slag can effectively repair saline alkali soil in field test.The application of desulfurized slag could significantly(p<0.05)reduce the surface soil(0-10 cm)p H,electrical conductivity(EC),soil salt content,sodium adsorption ratio(SAR)and soil exchangeable sodium percentage(ESP)in the first year.However,due to the salt seeping from the surface soil,the soil EC and salt content of the desulfurized slag treatment group were increased in the deeper soil layer(26-85 cm).This phenomenon was relieved after the third year of application of desulfurized slag.Desulfurized slag significantly increased the content of Ca²⁺in soil and decreased the concentrations of Na⁺,Cl^-,CO₃^2-and HCO₃^-.In addition,desulfurized slag can significantly reduce soil clay dispersion,compressive strength,plasticity index and the formation of cracking,and improve poor physical properties of soil.The reduction of soil cracking is due to the release of calcium ions from desulfurized steel slag,which can exchange sodium ions on the soil colloid,reducing the dispersion of clay in soil.(2)The combined application of desulfurized steel slag and fulvic acid can effectively repair the poor physicochemical properties of saline alkali soil and improve the structure of soil microbial community.In the pot experiment,compared with the control group,10%desulfurized slag and 1%fulvic acid could reduce p H,salt content,SAR and ESP 1.84 units,42.6%,62.7%and 38.6%,respectively.Desulfurized slag and fulvic acid could significantly improve soil specific surface area,plasticity index,porosity,soil cracking and other physical properties.Desulfurized slag and fulvic acid can also significantly improve soil microbial biomass,activity,abundance and diversity parameters.Statistical analysis shows that the activity,abundance and diversity of soil microorganisms in saline alkali soil are negatively correlated with soil p H,salt content,SAR and ESP,but positively correlated with soil nutrients.(3)From the assessment of environmental risk of heavy metals,it is feasible to use desulfurized steel slag as a modifier of saline alkali soil.In pot experiment,the total amount of heavy metals in soil of each treatment group was lower than the screening value of soil quality standard in China.But the total chromium content,available chromium content,chemical form chromium content and alfalfa chromium content increased with the increase of application amount,which had certain environmental risk.The chromium content in alfalfa is far lower than the standard limit of feed in China,and the risk to ecological environment is small.The content of available chromium in soil and the risk of chromium pollution in desulfurized steel slag can be reduced by applying fulvic acid.