小麦根系溶液活化生物炭吸附态Cd的机制研究

Study on the activated mechanism of Cd on biochars by wheat root solution

为探究根系环境对生物炭吸附态Cd的影响,制备和选取了对Cd吸附机理较为单一的生物炭,并添加到Cd污染的酸性和碱性土壤中,得到生物炭吸附态Cd,研究小麦根系溶液及有机酸(草酸和苹果酸)对生物炭上吸附态Cd的解吸作用.研究结果显示,小麦和猪粪在700℃制备的生物炭(WBC700和PBC700)添加到酸性土壤中约有11.7%和9.2%的Cd迁移到WBC700和PBC700上,高于碱性土壤中Cd向WBC700和PBC700上的迁移率,并且高于Cd向小麦在300℃制备的生物炭(WBC300)上的迁移率.与CaCl_(2)溶液相比,小麦根系分泌物可促进WBC300上Cd的解吸,但对BC700上Cd的解吸影响不显著.草酸和苹果酸均能促进三种生物炭上Cd的解吸,其中对WBC700和PBC700上Cd的解吸影响较大.苹果酸作用下,WBC700和PBC700上Cd的解吸率从35%分别提高到了85%和50%.草酸作用下,WBC700上Cd的解吸率从35%提高到了42%,但抑制了PBC700上Cd的解吸.结合三种生物炭吸附Cd的机理,有机酸可通过溶解和络合作用促进生物炭上Cd的释放,同时低浓度草酸可吸附在生物炭上进而抑制Cd的解吸.

To explore the effect of rhizosphere environment on Cd adsorbed on biochars,the biochars with relative single adsorption mechanism were prepared and added to Cd polluted acidic or alkaline soil.The effects of wheat root solution and organic acids(oxalic acid and malic acid)on the desorption of Cd from biochars were studied.The results showed that when biochars prepared from wheat and pig manure at 700℃(WBC700 and PBC700)were added to acidic soil,about 11.7%and 9.2%of Cd migrated from soil to biochars.And the migration amount of Cd from acidic soil to BC700 was higher than those from alkalinity soil to BC700(WBC700 and PBC700),and those from both acidic and alkalinity soil to WBC300.Compared with the CaCl_(2) solution,the wheat root exudate can promote the desorption of Cd from WBC300,but without affect the desorption of Cd from BC700.Both oxalic acid and malic acid can promote the desorption of Cd from the three biochars,among which the desorption of Cd from WBC700 and PBC700 were significantly affected.By using malic acid,the desorption rate of Cd from WBC700 and PBC700 increased from 35%to 85%and 50%,respectively.Oxalic acid increased the desorption rate of Cd from WBC700 from 35%to 42%,but inhibited the desorption of Cd from PBC700.Combined with the Cd adsorption mechanism on biochars,organic acids can promote the release of Cd from biochars through dissolution and complexation.The adsorption of oxalic acid on biochars can also inhibite the desorption of Cd from biochar.