不同碳材料增强有机酸对土壤重金属的去除及对土壤化学性质的影响

为了解碳材料和有机酸去除土壤重金属的效果,通过振荡淋洗法分别研究4种碳材料与柠檬酸、乙酸以及它们的复合淋洗剂对土壤重金属的去除。结果表明,单一纳米碳黑、水稻秸秆生物炭、木屑生物炭和果壳生物炭对重金属的去除率均低于0.5%。总体上,碳材料对柠檬酸去除重金属效果的提升作用高于乙酸,其中纳米碳黑对有机酸去除重金属的提升率最高,可达10.1%~11.1%,水稻秸秆次之,果壳和木屑生物炭对两种酸的提升率均低于5.8%。碳材料的加入,主要使酸溶态、可还原态和部分可氧化态的重金属在复合淋洗后显著降低(P0.05),相对于单一有机酸淋洗,复合淋洗更有利于减缓有机酸对土壤速效养分的损失。研究结果表明,纳米碳黑和水稻秸秆生物炭是能改进有机酸淋洗效果的两种材料。

Effects of different carbon materials for enhancement of organic acid-mediated removal of heavy metals and nutrient retention in soil

Four carbon materials, including single nano-carbon black(NCB), rice straw biochar(RSB), wood biochar(WB), and nut-shell biochar(NSB), and two low molecular weight organic acids(citric acid and acetic acid) were tested alone and in combination to determine their efficacy for removal of soil Cd, Pb, and Zn. Single carbon materials showed removal efficiency of less than 0.5%. Generally, citric acid enhanced the removal of heavy metals by carbon materials more than acetic acid. Compared with citric acid alone, NCB significantly improved the efficiency of Cd, Pb, and Zn removal(10.1%~11.1%), whereas RSB enhanced removal efficiency less than NCB(7.8%~10.3%), and WB and NSB weakly increased the efficiency(1.8%~5.8%). The exchangeable, reducible, and partly oxidizable fractions of Cd, Pb, and Zn decreased markedly after washing with the mixed solutions(P<0.05). Soil organic carbon content increased by 8.7%~26.5% for all treatments, whereas total potassium decreased significantly relative to unwashed soils(P<0.05). The total nitrogen and phosphorus contents in different washed soils did not change significantly in comparison with original soils. Compared with single organic acids, the loss rates of available nitrogen, phosphorus, and potassium were reduced by 1.4%~6.1%, 4.4%~11.5%, and 1.3%~10.4%, respectively, in the presence of carbon materials. Therefore, addition of carbon materials, especially nano-carbon black and rice straw biochar, to organic acids could effectively enhance the efficiency of removal of soil heavy metals, as well as alleviate the loss of available soil nutrients.