广西主要土类表层土壤对铅的吸附解吸特征研究

Characteristics of adsorption and desorption of Pb in different types of topsoil in Guangxi

为研究广西地区主要类型土壤对Pb的吸附解吸特征及其影响因素,采集湿润铁铝土、常湿富铁土、湿润富铁土、潮湿变性土、湿润淋溶土、湿润雏形土、潮湿变性土等7个亚纲9个土类表层土壤,通过等温吸附-解吸实验研究其对Pb的等温吸附与解吸特征及其影响因素。结果表明,供试土壤Pb的等温吸附曲线均可用Langmuir和Freundlich方程进行拟合,拟合相关系数分别为0.926—0.998和0.845–0.998,相关性均达到极显著水平。土壤铅的吸附量在不同铅浓度之间存在显著差异,钙积潮湿变性土在不同原始铅浓度下的吸附量显著高于其他类型土壤。不同类型土壤对铅最大吸附量介于(2776±23)—(19447±4)mg·L^(–1)之间,钙质湿润富铁土>铁质湿润淋溶土>钙积潮湿变性土>简育潮湿变性土>黏化湿润富铁土>铝质湿润雏形土>黄色湿润铁铝土(花岗岩发育)>简育常湿富铁土>黄色湿润铁铝土(浅海沉积物发育)。土壤Pb最大吸附量与pH、CEC、游离氧化铁、黏粒、粉粒含量呈显著正相关,与砂粒含量呈显著负相关,土壤pH和CEC是影响Pb最大吸附量的主要因素。土壤铅的解吸率呈现出随原始铅浓度增加而增加的趋势。

In order to study the characteristics of Pb adsorption and desorption of the main types of soils in Guangxi and its influencing factors,we collected surface soils of 7 subclasses and 9 great soil groups,including Udic Ferralosols,Perudic Ferrosolsl,Udic Ferrosols,Aquic Vertosols,Udic Argosols,Udic Cambosols,and Aquic Vertosols,and set 8 lead concentration gradients(0,25,50,100,200,400,600,800 mg·L^(–1))for isothermal adsorption-desorption experiments.The results showed that the Pb adsorption isotherms of the tested soils could be fitted with Langmuir and Freundlich equations,and the fitting correlation coefficients were 0.926-0.998 and 0.845-0.998,respectively,and the correlations had reached extremely significant levels.There were significant differences in the amount of lead adsorption in soil between different lead concentrations,and the adsorption capacity of Calci-Aquic Vertosols under different original lead concentrations was significantly higher than that of other types of soil.The maximum adsorption capacity of lead on different types of soils was between(2776±23)-(19447±4)mg·L^(–1),which Carbonati-Udic Ferrosols>Ferri-Udic Argosols>Calci-Aquic Vertosols>Hapli-Aquic Vertosols>Argi-Udic Ferrosolsl>Ali-Udic Cambosols>Xanthi-Udic Ferralosols(developed from granite)>Hapli-Perudic Ferrosols>Xanthi-Udic Ferralosols(developed from neritic sediment).The desorption rate of soil lead showed a trend of increasing with the increase of the original lead concentration.The maximum adsorption capacity of soil was positively correlated with the content of pH,CEC,free iron oxide,clay and silt,and negatively correlated with with the content of sand,among which the effect of pH,CEC was the most obvious.