Rice Bran Combined With Calcium Oxide And Superphosphate To Passivate Heavy Metal Lead And Cadmium Contaminated Soil

Human beings can't live without the land,it is the basis for human life and production.Therefore,it is vital to keep soil safe and health for humans.With the rapid development of our country's industry,the accompanying pollution problem of heavy metals has become an urgent environmental problem that we must face and solve.Soil heavy metal pollution has the characteristics of concealment,hard to degrade,difficult to migrate,strong bioaccumulation,high toxicity,and difficult to control.The presence of heavy metals in the soil will not only affect the amount of soil microorganisms and population structure,but also will be absorbed by plants into various organisms,and eventually enter the human body through thefood chain,seriously threatening human life and health.Curing/stabilization technology is to add organic or inorganic passivation agent to the soil,change the physical and chemical properties of the soil,and make the passivation agent added to physically and chemically react with the heavy metals in the soil,thereby changing the form of the heavy metal in the soil to reduce its biological effectiveness and mobility.Compared with other repair methods,in-situ passivation technology has the advantages of good repairing effect,short period,low cost,simple operation,and wide range of application in practically polluted sites.Commonly used inorganic deactivators such as calcium oxide and superphosphate have some side effects in the application process,and the use of organic-inorganic combination deactivators can improve the stability of heavy metals while improving the soil,so that the soil While contaminating with heavy metals,it promotes the growth of crops and increases crop yields.Rice bran is a by-product of agriculture.It is green and safe,has no harm to the soil,has a wide range of sources,and is inexpensive,and meets the requirements for soil passivation materials.This paper studied the passivation of heavy metals in soil by the combination of rice bran and traditional inorganic inactivators such as calcium oxide and superphosphate.The main results are as follows:?1?Effect of Rice Bran and Its Combination with Calcium Oxide and Superphosphate on Soil Physical and Chemical Properties.The results showed that:?1?Rice bran could adjust the pH by the ways of the combination of hydroxyl?-OH?and hydrogen ions and the combination of carboxyl?-COOH?and hydroxide ions.?2?.Rice bran increased organic matter that 6.00%rice bran increased organic matter to around 58.62⁶6.36g/kg g/kg.After adding calcium oxide to the soil,the organic matter content is reduced to about 32.49³3.40 g/kg.Under the combination of rice bran with calcium oxide,the content of soil organic matter was about 53.38⁶1.99 g/kg,which relieved the damage of calcium oxide on soil organic matter.?3?Rice bran could increase the enzyme activity of the soil.Adding 6.00%rice bran to the soil,the catalase and urease activities were 1.75².18 mg/g and 2.11×10^-34.39×10^-3 mg/g,which was approximately 2 times higher than that of the blank control group.SSP present substantially no influence on the enzyme activity,while the calcium oxide is too large increase intreatly increased catalase activit and decreased urease activity.The combined use of rice bran+calcium oxide and rice bran+sodium superphosphate promoted the activities of catalase and urease.The catalase activity was increased relatively 3 times and 2 times,the urease activity was increased 2 times compared with the control group?2?The stability of lead and cadmium in soil by adding rice bran and its combination with calcium oxide and superphosphate.?1?When Lead alone contaminated the soil,Pb was obtained with a stabilization efficiency of 38.06%on the 60th day increased with time and dosage.When cadmium alone contaminated the soil,the best stabilization efficiency was6.00%and it reached to 14.76%on the 20th day,positively correlated with the dosage and negatively with time.The trend of Pb and Cd stabilization efficiency in soil polluted by Pb and Cd is the same as that in contaminated soil alone.The stabilization efficiency of Pb is greater than that of Pb alone,and the stabilization efficiency of Cd is less than that of Cd alone.?2?On the 60th day the stabilization efficiency of Pb and Cd at 2.00%calcium oxide was 16.14%and 13.10%.The stabilization efficiencyof Pb and Cd in the soil with rice bran and calcium oxide was 47.36%and 26.09%.After 60 days the stabilization efficiency of2.00%calcium oxide for Pb and Cd was 26.53%and 15.62%in the composite pollution of lead and cadmium,and the efficiency for Pb and Cd in the soil with rice bran and calcium oxide was 46.52%and 22.04%.Compared with soils contaminated by lead and cadmium relatively,rice bran+calcium oxide reduceds the stability of Pb and Cd at the combined polluted soil.?3?After 60 days,At the soil of 0.60%SSP,the stablization efficiency was24.72%of Pb and 16.82%of Cd.Adding rice bran+SSP to soil,the stablization efficiency was44.82%of Pb and 24.42%of Cd.In the soil contaminated with lead and cadmium,SSP lead to 22.96%stablization efficiency of Pb and 11.21%of Cd on the 60th day,rice bran+calcium oxide lead to 44.15%stablization efficiency of Pb and 23.30%of Cd.Compared with soils contaminated by lead or cadmium,the stabilization efficiency of Pb and Cd decreased at the combined polluted soil.?3?Effect of rice bran and its combination with calcium cxide and superphosphate on the morphological changes of Lead and Cadmium in Soil.?1?On the 60th day,with the increase of rice bran dosage,the extractable state of Pb and Cd decreased,and the residue state increased,which reduced the bioavailability of heavy metals.Compared with the control group,the extractable ratio of Pb and Cd acid in the 6.00%rice bran amount decreased by 32.88%and 18.97%.The trends of Pb and Cd acid extractable and residual state in Pb and Cd contaminated soils are the same as Pb or Cd contaminated soils.?2?On the60th day,the extractable content of Pb and Cd in rice bran and calcium oxide soils was reduced by 30.00%and 10.00%compared with calcium oxide alone,and the extractable ratio of Pb and Cd acids was reduced by 39.68%and 21.41%compared with the control group.In the combined polluted soil,the trend of passivation effect of Pb and Cd by rice bran and calcium oxide is consistent with that of single contaminated soil.The acid extractable state of Pb and Cd in rice bran+superphosphate soil was slightly less than that of calcium superphosphate alone.In the combined polluted soil the trend of passivation effect of Pb and Cd by rice bran and superphosphate is consistent with that of single contaminated soil.