Amelioration Effect Of Biochar On Heavy Metal Contaminated Soil

The effectiveness of biochars incorporation in ameliorating heavy metal contaminated soils was investigated in this study. The immobilization and bioavailability of heavy metals was examined using naturally contaminated orchard soil (O) from Hongmiao Taian, Shandong Province, Cu spiked farmland soil (SF) from nierby orchard soil and Cu, Pb, Cd spiked woodland soil (SW) from Mountain Tai, Shandong Province. Corn straw derived biochar samples prepared from350℃(Cl) and700℃(C2) were used as soil amendments. Pot experiment of pakchoi, exposure experiment of earthworm, as well as apparent adsorption experiment were conducted. The research results were as follows:1. Incorporation of biochars in soil decreased the activity of heavy metals, and this effect enhanced as their dosage rose. C2had a better modification effect on both the immobilization of metals and increasing of soil pH than C1.2. In general, plant shoot dry weight increased with C1application rate. Pakchoi shoot dry weight increased by39.1%and20.8%in SF and SW, respectively, with C1additions of5%. However, the biomass dry weight did not increase when larger amounts of C2were applied, e.g.5%of C2treatments.3. Of the two soils tested (O and SW), both biochars decreased metal levels in the pakchoi with increasing level of application and C2was more effective in immobilizing metals.4. Treatments of O with2%C1and C2reduced the bioaccumulation of Cu into the worm tissue by26.7%and35.1%, respectively. Worms in the1%C1and C2amendments of SF had copper concentrations that were decresed by10.8and19.8%compared with the control.5. The oxidative stress in E. foetida decreased with an increasing concentration of biochar (0.5,1,2%, w/w) and augmented at the concentration of5%. Toxicity to earthworm was more severe with biochar pyrolyzed at700℃than its counterpart at350℃.6. Generally speaking, alkaline phosphatase and urease activities as well as microbial biomass in soil increased with raising addition of C1. Together, we found that C2did not increase enzymic activity and microbial biomass as much as C1.7. Results indicated that incorporation of the biochars increased metals adsorption by the soils and the effect was enhanced progressively with increasing application rate of biochars. At a given biochar content, sorption enhancement of soil by amended-biochar increased in the order of C2<C1.