Assessment Of Nutrient And Pollution Risk And Influence Factors Of Fly Ash As A Soil Amendments

In order to explore the feasibility of using fly ash as a soil amendment,SEM,EDS,XRD and AAS were used to characterize it.The bulk density,pH value,organic matter,available phosphorus and available potassium,total nitrogen,total potassium and other physical and chemical indicators of the fly ash were determined.The content and morphology of heavy metals Cd,Cr,Co,Ni,Zn,Fe,Pb,Cu and Mn were measured and analyzed.The potential ecological risk of fly ash was assessed by using the Nemerow comprehensive index method and Hakanson potential ecological risk index method.Contamination risk at different pH,temperature and particle size was assessed.The conclusions are as follows:(1)The pH value of fly ash was 8.6.The bulk density is 0.51 g/cm3 and the sand content is smaller than 85%,and the texture is looser.Compared with soil fertility index,available phosphorus and available potassium reached three levels,organic matter reached four levels,and the contents were abundant.Most of the 7 heavy metals exist in the form of residue,relatively stable,and will not cause heavy metal pollution in the soil.The Nemerow comprehensive pollution index of heavy metals in fly ash is 1.39,and the evaluation standard is grade three.RI value of the potential ecological hazard index is 85.45,which is a slight hazard level.(2)With the increase of acidity,the leaching contents of Cd,Co and Pb increase.When the acidity reaches the maximum,the heavy metal content in the leaching solution reaches the maximum,and lead does not leach.The amphoteric leaching of Ni,Cu,Zn and Cr occurred in the leaching test,that is,the variation curve of heavy metal content in the leaching solution showed a "U" shape with the increase of pH.That is to say,with the increase of pH,the content of heavy metals in leaching solution first decreases and then increases.(3)With the increase of temperature,the content of heavy metals in leaching solution increased.Cr first increases and then decreases with the increase of temperature.Zinc,copper,lead,nickel,cadmium and cobalt showed an overall upward trend with the increase of temperature,and the leaching amount was the largest at 35 ?.The leaching content of chromium first increased and then decreased with the increase of temperature.With the increase of mesh number and the decrease of particle size,the content of heavy metals in fly ash leaching solution increases.(4)Under different pH,temperature and particle size conditions,Pi values of the seven heavy metals in fly ash are all less than 1,and there is no pollution in fly ash.At the same time,the Nemerow comprehensive pollution index evaluation standard of fly ash leaching solution under different pH,temperature and particle size conditions is all level 1,and the environmental pollution grade of fly ash is all safety grade.The environmental pollution level of Cd,Ni,Zn,Co,Cr,Pb and Cu is clean level.(5)Under different pH conditions,except Cd,the eir of other heavy metals were lower than 40,and the pollution degree was clean level.The eir of Cd is higher than 40,and the pollution level is low.(6)At 0?,25?,30?,and 35?,the eir of Cr,Cu,Pb,Ni,Zn and Co were lower than 40,and the pollution level was clean.The eir of Cd is higher than 40,and the pollution level is low.At 10?,15? and 20? the eir of Cd,Cr,Cu,Pb,Ni,Zn and Co were lower than 40,and the pollution level was clean.Under the condition of different particle sizes,the eir of the seven heavy metals were lower than 40,and the pollution level was clean level.(7)The RI values of seven heavy metals in fly ash under different pH,temperature and particle size conditions did not exceed 150,which means that fly ash is in a slight ecological hazard level.In conclusion,it is feasible to use fly ash for soil improvement,which has good application prospects for improving soil fertility,absorbing heavy metals and improving soil.Fig 19 Tables 26 Reference 126...