| Stainless steel slag is by product of steel-making process, with large amount of discharge. In china, due to the low resource utilization, it is generally used as waste stockpiling, which caused great waste of resources and heavy environmental pressure. Therefore, resource utilization of stainless steel slag has attracted many attentions from society. Stainless steel slag contains a large number of calcium, silicon, iron, magnesium, potassium, sodium and other useful elements, which are beneficial to soil and plant growth. In addition, calcium oxide and silicate derived from stainless steel slag could fix the soil heavy metal. The effective way to comprehensively utilize steel slag is to repair heavy metal contaminated soil, which could not only reduce iron and steel enterprise pressure, but also curb environment pollution, producing considerable social, environmental and economic benefits. At present, stainless steel slag applied to heavy metal contaminated soil repairation research is less.In this essay, stainless steel slag was respectively mixed with humic acid, vinegar residue, corn stover, natural zeolite with different proportion as soil remediation agents. Indoor soil culture experiment was made to compare different ratio of remediation agent effect on soil lead pollution, thus selecting the best restoration ratio; Under simulated rainfall condition, effect of stainless steel slag remediation agent on soil lead migration was conducted by soil column leaching experiments; Effect of remediation agent on ryegrass(Lolium perenneL) growth in lead contaminated soil and the influence of soil physical and chemical properties were conducted through pot experiment. The feasibility of stainless steel slag remediating heavy metal polluted soil was discussed to provide theoretical and technical support for the effective utilization of stainless steel slag and remediation of heavy metal contaminated soil. The main results were as follows:(1) Among the 5 kinds of materials, stainless steel slag, humic acid and vinegar residue could effectively reduce the available lead content in lead polluted soil; it reduced by 28.24%,47.30% and 28.24%, respectively. Compared to different ratio of stainless steel slag/vinegar residue, stainless steel slag/maize straw and stainless steel slag/natural zeolite, stainless steel slag/humic acid has the best remediation effect. With 20%,40%,60% ratio of stainless steel slag, including stainless steel tailings, available lead content reduced by 38.65%,37.97% and 34.32%, respectively. Therefore, in the different ratio of remediation agents, stainless steel slag (20%)/humic acid (80%) had the best remediation effect on lead polluted soil.(2)Under simulated rainfall condition, in the non-remediation agent treatment, the sequence of lead formation distribution is:Fe-Mn oxide form> carbonate combined state> residual state> exchangeable state> organic bond state. After applying repair agent, in the same layer soil, with the increase of stainless steel slag proportion in the repair agent, exchangeable state lead had no significant change, carbonate combined state lead gradually reduced, Fe-Mn oxide form lead gradually increased, the organic bond state and residue lead gradually reduced. Different proportion of repair agent had no significant effect on exchangeable state lead; promoted transformation from carbonate combined lead to Fe-Mn oxide form lead, organic bond state lead and residual state lead, thus reducing lead bio-availability in polluted soil. Various forms of lead had the same changing rule in different soil layer.(3)Application of stainless steel slag remediation agent (stainless steel slag/humic acid, stainless steel slag ratio 20%) could increase soil pH, soil organic matter and cation exchange capacity, with high increase range along with the increase of remediation agent. It effectively enhanced the fixed action of lead in lead polluted soil.(4)Ryegrass has good tolerance and absorptive characteristic to lead. Application of remediation agent could effectively reduce lead absorption in aboveground ryegrass.(5)Effects of repair agent dosage on ryegrass aboveground dry biomass had different rules according to different lead concentration. When applying 1% repair agent into 125 mg/kg of lead pollution soil, ryegrass aboveground dry biomass had no significant change, but can improve biomass in 500 mg/kg lead polluted soil; while dry bimass reduced in 1000 mg/kg polluted soil.2% and 5% repair agents could reduce ryegrass aboveground dry biomass under three kinds of lead concentration level (125 mg/kg and 500 mg/kg and 1000 mg/kg). Applying 1%,2% and 5% stainless steel slag could both effectively increase dry biomass in high concentration of lead polluted soil (2000 mg/kg).(6) Under low lead stress (125 mg/kg), stainless steel slag remediation agent had a certain inhibitory effect on SOD activity of ryegrass leaf; while in high concentrations of lead stress (2000 mg/kg), remediation agent had activate effect on SOD, which could effectively remove excessive superoxide anion in ryegrass leaf to reduce lead stress. In uncontaminated soil and-moderate contaminated soil (500 mg/kg), applying appropriate (2%) remediation agent could activate ryegrass leaf SOD activity, strengthen ryegrass resistance; applying excessive (5%) remediation agent could restrain the leaf SOD activity and lower ryegrass resistance in adversity.(7) Applying stainless steel slag remediation agent into uncontaminated soil could effectively improve ryegrass leaf POD activity and enhance ryegrass resistance. Under high level lead stress (1000,2000 mg/kg), a little amount of remediation agent (1%-2%) could activate ryegrass leaf POD activity; excessive remediation agent (5%) had a certain inhibitory effect on ryegrass leaf POD activity.(8) Appropriate amount (1%-2%) of stainless steel slag remediation agent could reduce the aging condition of ryegrass leaf cells, to a certain degree; and help to relieve lead stress to ryegrass. However, excessive (5%) stainless steel slag remediation agent could promote cell ageing. |
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