贵州泥质灰岩中性自然与耕作黄壤镉的表面络合模型
Study on surface complexation model of cadmium in neutral natural and cultivated yellow soils of argillaceous limestone in Guizhou
李万利 1安娅 1李梅 1李治梅 1杨阳 2秦好丽1
作者信息
- 1. 贵州师范大学化学与材料科学学院,贵阳,550001
- 2. 广东省科学院生态环境与土壤研究所,广州,510650
- 折叠
摘要
贵州省黄壤Cd污染形势严峻,而地域性及母质分异会引起土壤表面酸碱性质及其对重金属Cd吸附行为的差异.本研究以贵州省黔西林泉镇泥质灰岩发育的不同深度4层中性自然黄壤和耕作黄壤为研究对象,基于土壤理化性质、连续电位滴定实验、不同pH下两土壤对Cd的吸附实验,利用1-site/2-pKa表面络合模型(SCM)探究两土壤表面酸碱性质,模拟两土壤对Cd的吸附行为及其形态分布,同时探究耕作对土壤表面酸碱性质及其对Cd吸附行为的影响,并通过相关性分析解析两土壤组成与表面酸碱性质的关系.结果表明,基于电位滴定实验和SCM计算所得的两土壤表面位点浓度(Hs)和表面位点密度(Ds)随土层深度基本呈下降趋势,自然黄壤Hs大于耕作黄壤,Ds反之.电荷零点的模型计算值(pHpzc,SCM)与实验值(pHpzc,M)十分接近且变化趋势一致,表明该模型对于泥质灰岩中性黄壤的表面酸碱性质具有较好的适用性.结合不同pH下两土壤对Cd的吸附实验,利用SCM拟合获得的吸附态、溶解态曲线与实验数据吻合好(r≥0.98),模型拟合≡SOH2+、≡SOH、≡SO-的3种表面位点的形态分布揭示Cd在不同pH下的吸附特征,说明1-site/2-pKa SCM可预测不同酸碱条件下Cd的存在形态及其在泥质灰岩中性土壤上的吸附行为.通过土壤酸碱性质参数和组分的相关性分析表明两土壤的表面酸碱活性位点主要受有机质影响,而土壤pHpzc基本由铁铝氧化铁决定.因耕作施肥造成自然黄壤与耕作黄壤之间有机质含量的差异,使耕作黄壤表现出较弱的缓冲能力和较大的缓冲范围;两土壤pHpzc较为接近,导致Cd的吸附行为无明显差异.研究显示,1-site/2-pKa SCM可用于准确描述泥质灰岩中性黄壤表面酸碱性质及Cd的吸附特征.
Abstract
The yellow soil in Guizhou Province is severely polluted with Cd.The differences of soil surface acid-base properties and the adsorption behavior of heavy metal Cd were caused by different regional and parent material.In this study,four layers of neutral natural yellow soil and cultivated yellow soil with different depths developed from argillaceous limestone in Linquan Town,Qianxi,Guizhou Province,were taken as the research objects.Based on the physical and chemical properties of the soil,continuous potentiometric titration experiments,and the adsorption experiments of Cd on the soil at different pH,the adsorption behavior and morphology distribution of Cd on the two soils were simulated with the 1-site/2-pKa surface complex model(SCM),which was used to explore the surface acid-base properties.The relationship between the composition of the two soils and the surface acid-base properties was analyzed by correlation analysis.The results showed that the surface site concentration(Hs)and surface site density(Ds)of the two soils calculated based on the potentiometric titration experiments and SCM exhibited basically a downward trend with the depth of the soil layer.The Hs of the natural yellow soil was greater than that of the cultivated yellow one,and the opposite results for Ds.The calculated value of charge zero(pHpzc,SCM)was very close to the experimental value(pHpzc,M)and their change trend were also consistent,which indicated that the SCM could be good applicability for the surface acid-base properties of argillaceous limestone neutral yellow soil.Combined with the adsorption experiments of Cd on two soils at different pH,the adsorption and dissolution curves obtained by SCM fitting were fitted well with the experimental data(r≥0.98),and the morphology distribution of such three surface sites as ≡SOH2+,≡SOH,≡SO-fitted by the model was revealed the adsorption characteristics of Cd at different pH,which indicated that 1-site/2-pKa SCM could predict the existing form of Cd under different acid-base conditions and its adsorption behavior on the neutral soil of argillaceous limestone.The correlation analysis of soil acid-base property parameters and components showed that the surface acid-base active sites of the two soils were mainly affected by organic matter,while the pHpzc was basically determined by oxides of iron and aluminum.Due to the different content of organic matter between the natural yellow soil and the cultivated ones caused by cultivation and fertilization,the cultivated soil showed weaker buffering capacity and larger buffering range.It was no significant difference in Cd adsorption behavior of the two soils for their relatively close value of pHpzc.Above all,the results showed that 1-site/2-pKa SCM could be applied to describe accurately the surface acid-base properties and Cd adsorption characteristics of the argillaceous limestone neutral yellow soil.
关键词
贵州泥质灰岩/中性黄壤/Cd/表面络合模型/表面酸碱性质/吸附/耕作Key words
Guizhou argillaceous limestone/Neutral yellow soil/Cd/surface complexation model/surface acid-base properties/adsorption/cultivation引用本文复制引用
基金项目
国家自然科学基金(41967003)
贵州省自然科学基金(20201Y182)
出版年
2024
NETL
NSTL
万方数据