Effect Of Fly-Ash On Bioavailability Of Heavy Metal For Composting And Its Transformation In Environment

The content of heavy metals in manure such as Cu and Zn is increasing day by day.The heavy metals will pollute the surface and groundwater with soil runoff and endanger human health.The effect of fly ash on the heavy manure in manure was studied by composting test,pH-dependent leaching test,pot experiment and column leaching test.This study aimed at analyzing the leaching characteristics of heavy metals in organic fertilizer,evaluating the migration of heavy metal in soil-vegetable system and the impact on the human body,simulating the characteristics of heavy-metal leaching in soil,to find out the effective way to reduce the bioavailability of metal.The study could provide theoretical basis for resource-based harmless and reduce the environmental effects of heavy metals in poultry manure.The main conclusions are as follows:(1)Adding fly ash could reduce the effectiveness of Cu and Zn and make the humus more stable during composting.The total amount of humus decreased,the HA/FA increased during composting process.Changes in humus affected the effectiveness of Cu,Zn.The contents of Cu and Zn decreased the distribution of Cu-OM and Cu-RES was more than 90%.Zn-Fe/Mn OX,Zn-OM and Zn-RES had a distribution rate more than 75%.The distribution of Cu-OM in F5 group increased from 82.82%to 84.18%,and the Zn-RES was increased 18.97%,which indicated that fly ash as stabilizing agent can stabilize zinc more significant than copper.(2)The leaching concentrations of heavy metals and DOM were minimum at neutral pH,but became higher at strongly alkaline and acidic pH,thus displaying strong pH dependence.Addition of fly ash affected the leaching behavior of compost.The concentrations of Cu and Zn leached from the experimental group were lower than those from the reference at minimum concentrations at the pH range of 3-9.It could be summarized that adding fly ash can reduce the environmental risk that caused by heavy metals.(3)Pot experiment showed that the application of organic fertilizer could significantly increase the fresh weight,plant height and root length of plant.But under different treatment conditions,the enrichment coefficient of heavy metals in cole was different.The compost with fly ash could reduce the bioaccumulation coefficient.The humic acid and humin were reduced by more than 30%,the Cu-OM was significantly decreased,and the Zn-Fe/Mn OX were significantly increased during the experiment.Compared with composting without passivating agent,the content of X-Fe/Mn OX was significantly higher in the potting treatment with passivating agent.And the addition of fly ash might affect the humus structure in the soil and the soil fertility.(4)The simulated leaching test showed that the addition of fly ash could reduce the leaching of heavy metals in the soil.The total amount of heavy metals was significantly decreased in the soil leaching test expect the soil with 10%F5 compost.The filtrate concentration of Zn is much higher than that of Cu.The behavior of Cu and Zn in the leaching experiment was similar,which was decreased from high to low.The 5%fly ash compost treatment contains porous structure so that its heavy metal filtration concentration is lower than CK compost.