Abstract: Effects of 4 kinds of biochars derived from straws of peanut, soybean, canola and rice,separately, on Cu(II) adsorption by the red soil samples from Jiangxi and Guangxi were investigated with batch method,to explore roles of the biochars in remedying heavy metal polluted red soils.Results indicate that incorporation of the biochars in creased Cu(II) adsorption by the soils.The effect was enhanced with decreasing pH of the system and with increasing application rate of biochars as well.With pH at 4.0 and  biochar added at 2%, Cu(II) adsorption increased by 97%, 79%, 51% and 54%,respectively,by application of biochar of canola,peanut,soybean and rice straws in the red soil from Jiangxi,and by 61% and 44%,respectively,by application of biochar of peanut straw and soybean straw in the red soil from Guangxi.The increment reached to 97% and 165%, respectively, when the addition of the biochars of the biochars was increased to 4%. Biochars normally carry negative charges and have ample amount of oxygen-containing functional groups on their surfaces, which greatly  increase electrostatic and specific adsorptions of Cu(II) in the red soils simultaneously,but it is more significant with the latter than with the former.Therefore,incorporation of biochars can effectively reduce mobility and bioavailability of Cu(II) in acid red soils.

Key words: red soil, biochar, crop straw, Cu(II) adsorption