紫色土外源砷的形态分配与化学、生物有效性

Forms and bio-availabilities of exogenous arsenic in purple soils.

采用盆栽试验与化学分析相结合的方法研究了外源As在酸性、中性、钙质紫色土中的形态分配及其化学、生物有效性特征.结果表明,土壤本底As68%～86%为残留态,外源As加入10d后50.2%～61.1%转化为残留态,至收获期(60d)仅增1%～2%.酸性紫色土中活性态As分配为:A(交换态)As>Al As>Fe As>Ca As;中性紫色土:A As>Al As>Ca As>Fe As;石灰性紫色土:A As>Ca As>Al As>Fe As.浸提剂HCl、NaHCO3、NH4Cl对土壤As的提取能力不同,与植物吸收As的相关性也有差异.NH4Cl主要提取交换态As,对土壤As的原有形态影响最小,与植株吸收量呈极显著相关,可作为不同土壤有效As的通用浸提剂.多元回归表明,酸性紫色土决定植株吸As量的是Al As和Fe As,中性、石灰性紫色土为A As和Ca As.试验发现,Al As分级时存在F-的干扰,1mol·L-1H3BO3可有效掩蔽.

This study showed that after As was added into purple soils for 10 days,50.2%～61.1% of it transformed into residual As,occupying 68%～86% in original soils.For acid purple soil,the As forms were Al-As >Fe-As>Ca-As;for neutral purple soil,they were Ca-As>Al-As>Ca-As>Fe-As>A-As,and for calcic purple soil,they were Ca-As>Al-As>Fe-As>A-As.It is suggested that NH 4Cl could be used as common extractant for different soils,because it slightly affected original As forms in soils,and showed a highly significant correlation (P=0.01) to plant absorption.From pluralistic regressive analysis of plant As content and each As form,Al-As and Fe-As were the main available forms in acid purple soil,but A-As and Ca-As were the most important fractions in neutral and calcic purple soils.The study also showed that H 3BO 3 could restrain the F interference in the operation of As speciation separations.