The Remediation Of Heavy Metal Contaminated Soil Around A Pb/Zn Mine By Different Biochars Derived From Rice Straw And Pig Manure

With the rapid development of urbanization and industrialization, the heavy metals pollution in soil is becoming increasingly serious. As a noval environment functional material, biochar has great potential for remediation of soil polluted by heavy metals. Bicoahr reduces the biovailability of heavy metals by electrostatic attraction, ion exchange, surface complexation and coprecipitation. Nowadays, a large number of literature has focusd on the influence of biochar derived from single feedstock under different tempreature and its possible mechanisms, however, limit literature is reported about biochar from the blend of two kinds of materials. What’s more, previous studies suggested that straw biochar has large surface area and that manure biochar, with high ash content and pH, has its environmental risk due to high heavy metals concentrations itself.In this study, rice straw was added to pig manure at 3:1,1:1 and 1:3(w/w) straw and manure ratios respectively and then the mixures were pyrolyzed under 400℃ to obtain three kinds of biochar. Besides, straw biochar and manure biochar were also included. The objectives were to:(1) characterize the physicochemical properties of different biochars; (2) study the effects of different biochars on soil pH, electric conductivity and dissolved organic carbon; (3) figure out the changes in bioavailability of Pb, Zn, Cd and Cu after biochar addition; (4) evaluate the effect of different biochars on growth of plant and uptake of Pb, Zn, Cd and Cu. Main results are summarized as follows:1. Basic elements, physicochemical properties and surface characteristics of biochars were closely related to feedstocks. Biochar’s productivity, ash content and total Zn, Pb and Cu contents increased with the addition of manure while moisture content, pH, EC, carbon content and total K content increased with the addition of straw. Different biochars ranked as R<R1M3<R3M<R1M1<M in order of their surface area and total pore volume from small to large. The surface area of manure biochar was 3.462 m2/g.2. Influence of application of different biochars on soil pH, EC and available Zn, Pb, Cd and Cu contents were studied. The results are as follows. Soil pH and EC were obviously enhanced with biochar rates. Under the same rate of the additive, the capacity of biochars to enhance soil pH improved as the addition of manure with the capacity to EC just the reverse. Correlation analysis showed that available Zn, Pb, Cd and Cu contents had a positive correlation with soil pH, EC, and DOC content. To sum up, the efficiency of immobilization of heavy metals had a relationship with physicochemical of both biochr and soil.3. Pot experiemts revealed that the influence of biochars application on the growth of plant and the uptake of Zn, Pb, Cd and Cu contents. A rise in soil DOC content occurred and the differences between biochars were distinct.Biochar could significantly promoted the growth of plant, manure biochar pronounced among five biochars. Moreover, biochar also could reduce the uptake of plant to heavy metals in soil, with straw biochar having the lowest heavy metals concentration in the root. Correlation analysis showed that Zn, Pb, Cd, Cu content in the root had a correlation with soil pH, EC value, DOC content and available Zn, Pb, Cd, Cu content in soil while Zn, Pb, Cd, Cu content in the shoot were affected mostly by soil pH.