腐殖酸对外源砷在土壤中形态转化和有效性的影响

Transformation and Bioavailability of Exogenous as in Soil as Influenced by Humic Acids and Its Active Components

通过室内培养的方法,探讨腐殖酸(HAs)的两种活性组分——富里酸(FA)和胡敏酸(HA)及其不同比例(HA/FA)对土壤As形态转化及有效性的影响。结果表明,HAs的两种组分对土壤As的形态均具有显著影响,其影响程度和方向与其浓度、比例及外源As含量有关。FA和添加量≤1%C的HA能增加土壤交换态As(Ex-As)的含量,添加量≥3%C的HA能降低土壤Ex-As含量;两种组分都能降低土壤铝型As(Al-As)和铁型As(Fe-As)含量,增加残渣态As(Res-As)含量,FA比HA的作用效果更强;在等量(1%C)HAs条件下,HA/FA≥5/5时HAs能降低Ex-As含量,≤3/7时则能增加Ex-As的含量。HAs对土壤有效As的影响是其对As形态分配综合作用的结果,对土壤有效As贡献最大的是Ex-As和Ca-As;HA和添加量较高(≥5%C)的FA能够降低外源As在土壤中的有效性,而添加量较低(≤3%C)的FA能在一定程度上增加土壤As的有效性。因此,掌握有机物料合理的用量和活性组分比例是其作为土壤As活性调控剂的前提。

The mobility, bioavailability and toxicity of arsenate （As） in soils are restricted by its species. Humic acids （HAs） are important factors affecting the fractionation of As in soils. An indoor cultivation experiment was conducted to discuss the effects of the two active components of HAs （fulvic acid, FA; and humic acid, HA） and HA/FA ratio on the transformation of As in soils. The results showed that FA and HA had significant effects on different As species in soils, and the influence degree and direction were connected with HAs concentration, proportion of FA and HA and exogenous arsenic content. FA and HA with carbon content ≤1% increased the content of exchangeable As, but HA with carbon content ≥3% decreased the content of exchangeable As （Ex-As）. FA and HA decreased the content of As combined with aluminum （Al-As） and iron （Fe-As）, and increased residual As （Res-As）, and FA was stronger than HA in effect. Under the condition of the same amount of HAs, when HA/FA ≥5/5, HAs decreased the content of Ex-As, but when HA/FA≤3/7, HAs increased the content of Ex-As. With the increase of exogenous As content, Al-As increased, Ex-As and Res-As decreased, Fe-As first increased then decreased. Ex-As and Ca-As had the largest contribution to effective As in soil. HA reduced the effectiveness of exogenous As in soil, but FA in low concentration （≤3% C） increased the bioavailability of As to a certain extent. It is important to control the reasonable amount and active component ratio of organic material when using it as As regulator in soil.