煤基腐殖酸对土壤砷赋存形态和小白菜生长及砷吸收分布的影响

为探讨部分煤基腐殖酸性质与土壤砷有效性的关系及其在砷污染土壤修复改良中的潜在利用性和应用方向,通过小白菜盆栽试验研究了4种煤基腐殖酸对土壤砷形态和含量及小白菜生长和砷吸收分布的影响。结果表明:6号和10号煤基腐殖酸显著降低了土壤可交换态和碳酸盐结合态砷含量,从而显著降低土壤有效砷含量,抑制砷向小白菜地上部转移和积累;特别是添加10号煤基腐殖酸土壤可交换态砷含量、有效砷含量和小白菜地上部砷总量分别比As处理降低了49.18%,42.22%和15.17%。而9号和11号煤基腐殖酸增加了土壤可交换态和碳酸盐结合态砷含量,显著增加土壤有效砷含量,对小白菜吸收砷并向地上部转移也有一定促进作用,二者土壤可交换态砷含量、有效砷含量和小白菜地上部砷总量分别比As处理增加了10.58%和5.95%,31.11%和22.22%,20.81%和17.21%。4种煤基腐殖酸对小白菜生长均有一定的促进作用,总体表现为10号6号11号9号。因此,E4/E6值小、分子量大、总酸性基含量较低的6号和10号煤基腐殖酸对土壤砷具有明显的钝化作用,可用于轻度砷污染土壤治理中抑制作物对砷的吸收和向地上部转移,实现作物安全生产;而E4/E6值大、分子量小、总酸性基含量较高的9号和11号煤基腐殖酸对土壤砷具有一定的活化作用,在中度和重度砷污染土壤的植物修复中可作为活化剂强化修复速度和效果。

Effects of Coal-based Humic Acid on Soil Arsenic Occurrence Form, the Growth and Arsenic Adsorption and Distribution of Pakchoi

In order to investigate the relationship between some properties of coal-based humic acids and arsenic availability in soil,and potential utilization and application direction of coal-based humic acids in the remediation and improvement of arsenic contaminated soil,a pot experiment was conducted to study the effects of four coal-based humic acids on the content and speciation of arsenic in soil,the growth of pakchoi (Brassica campestris L.ssp.),and the absorption and distribution of arsenic in pakchoi.The results showed that No.6 and No.10 coal-based humic acids significantly reduced the contents of exchangeable arsenic and carbonate bound arsenic,thus the content of available arsenic in soil was reduced significantly,meanwhile,the transfer and accumulation of arsenic from underground part to aboveground part of pakchoi were inhibited.The contents of exchangeable arsenic and available arsenic in soil and the total amount of arsenic in aboveground part of pakchoi in No.10 coal-based humic acid treatment reduced 49.18％,42.22％,and 15.17％ than those in arsenic treatment,respectively.However,No.9 and No.11 coal-based humic acids increased the contents of exchangeable arsenic and carbonate bound arsenic,significantly increased available arsenic in soil,and promoted the arsenic absorption and the transfer of arsenic from underground part to aboveground part of pakchoi.The contents of exchangeable arsenic and available arsenic in soil and the total amount of arsenic in aboveground part of pakchoi in No.9 and No.11 coal-based humic acids treatments increased 10.58％ and 5.95％,31.11％ and 22.22％,20.81％ and 17.21％ than those in arsenic treatment,respectively.The four coal-based humic acids all promoted the growth of pakchoi,and the promotive effect followed the order of No.10＞No.6＞No.11＞No.9.In conclusion,No.6 and No.10 coal-based humic acids,which had lower E4/E6values,larger molecular weights,and lower contents of total acid base,had obviously inactivate effect on arsenic in soil,and could be used to control the arsenic absorption of crops and inhibit the transfer of arsenic from underground part to aboveground part of crops in mild arsenic polluted soil,so as to ensure crop safety production.No.9 and No.11 coal-based humic acids,which had larger E4/E6 values,lower molecular weights,and larger contents of total acid base,promoted arsenic activity and could be used as activator in moderate and severe arsenic polluted soil to strengthen phytoremediation.