秸秆和牛粪生物炭对矿区菜地土壤中镉的钝化效果和小白菜生长的影响

Effects of Straw and Cow Dung Biochars on the Cadmium Passivation in the Vegetable Fields around the Mining Area and the Growth of Chinese Cabbage

有色金属矿区大面积稻田土壤重金属污染修复一直备受关注,然而矿区附近零散分布的菜地土壤安全利用问题尚未引起大家足够重视,这将严重威胁当地居民的健康。通过热解制备5种生物炭修复材料(稻壳生物炭、玉米秸秆生物炭、芝麻秸秆生物炭、牛粪生物炭和高铁酸钾改性稻壳生物炭),以铜陵某矿区周边镉污染菜地土壤为修复对象,对当地广泛种植的四季小白菜(Brassica chinensis)开展盆栽修复试验研究,以揭示不同生物炭材料对镉污染土壤的钝化机理、修复效果及小白菜生长的影响。结果表明,按照w=1.5%分别施加不同生物炭材料后,不同盆栽土壤pH和阳离子交换量均有不同幅度提升,有效态Cd含量也分别降低2.87%(稻壳生物炭)、7.03%(玉米秸秆生物炭)、14.38%(芝麻秸秆生物炭)、32.19%(牛粪生物炭)和24.66%(高铁酸钾改性稻壳生物炭)。与对照组相比,施加不同生物炭材料后,小白菜地上部Cd含量均有不同程度降低,生物量(株高和鲜重)也有不同程度增加。其中,芝麻秸秆生物炭、牛粪生物炭和高铁酸钾改性稻壳生物炭的钝化效果较为显著,不仅显著降低小白菜体内镉含量,而且有效促进其生长发育,这可能与这些材料具有丰富的表面官能团和较高的灰分含量有关。综上,本研究可为保障矿区重金属污染菜地土壤安全利用和食品安全提供重要参考。

The remediation of heavy metal contamination for large areas of paddy soils in non-ferrous metal mining areas has received much attention.However,the safe use of soil in scattered vegetable fields near mining areas has not yet been adequately studied,which will seriously threaten the health of local residents.In this study,five types of biochar remediation materials(rice husk biochar,corn straw biochar,sesame straw biochar,cow dung biochar and potassium ferrate modified rice husk biochar)were prepared by pyrolysis method.Taking the vegetable soil around a mining area in Tongling that suffered from cadmium contamination as the object of remediation,potting remediation experimental study of four-season Chinese cabbage(Brassica chinensis),which is widely planted in the local area,was carried out in order to reveal the effects of different biochar materials on the passivation mechanism of cadmium-contaminated soils,remediation effect,and the growth of Chinese cabbage.It was found that the application of different biochar materials at the rate of 1.5%increased the pH and cation exchange of different potting soils by different degrees,and the content of available Cd in soil was also reduced by 2.87%(rice husk biochar),7.03%(corn stover biochar),14.38%(sesame straw biochar),32.19%(cow dung biochar)and 24.66%(potassium ferrate modified rice husk biochar),respectively.Compared to the control group,the application of different biochar materials resulted in different reductions in aboveground Cd content and increases in biomass(i.e.,plant height and fresh weight)of Chinese cabbage.Among five types of biochar,the passivation effect of sesame straw biochar,cow dung biochar and potassium ferrate modified rice husk biochar were more obvious,which not only significantly reduced the cadmium content in Chinese cabbage,but also promoted its growth and development.Such results might be related to the fact that these materials have rich surface functional groups as well as high ash content.In conclusion,this study can provide important reference for the safe use of heavy metal contaminated vegetable land soil in mining areas and for food safety.