摘要
选取人工合成的无定型氧化铁(AHOsFe)纯矿物,以及两种典型土壤(黑土和砖红壤)的原土(S1和S2)和AHOsFe包被土壤(AHOsFe-S1和AHOsFe-S2)为研究材料,采用批量平衡法,研究AHOsFe对土壤中阿特拉津(AT)吸附—解吸行为的影响及其机理。研究结果表明,各吸附剂对AT的吸附均能采用Freundlich方程进行较好地拟合(r≥0.996,p<0.01),AHOsFe对AT具有较强的吸附性能和较高的吸附非线性,AHOsFe包被黑土和砖红壤后,两种土壤对AT的吸附能力(Kd值)分别增加56.3%和43.8%。各吸附剂对AT均存在解吸迟滞效应,两种土壤及被AHOsFe包被后,其对AT的解吸迟滞系数(HI)在AT低初始浓度时随浓度的增加而降低,而在AT高初始浓度时随浓度的增加略有增加,AHOsFe对AT的HI则随AT初始浓度的增加而增加,说明不同吸附剂在AT不同初始浓度时的解吸迟滞机制不同。与土壤相比,AHOsFe对AT具有较强的解吸迟滞效应,但AHOsFe包被土壤后,却降低了土壤对AT的解吸迟滞效应。
【Objective】Adsorption-desorption is a key factor governing translocation,transformation,fate and bioavailability of organic pollutants,such as atrazine(AT),in the soil. The adsorption-desorption behaviors of organic pollutants in the soil are not only related to physico-chemical properties of the organic pollutants per se,but also affected by soil organic matter(SOM),inorganic minerals and some other important soil components. There have been large volumes of studies demonstrating that SOM is the major factor governing adsorption-desorption of AT in the soil,but some others indicating that soil inorganic minerals may be almost equal to or higher than SOM in such effect in the case that SOM is relatively low in content in the soil. Current researches about soil inorganic minerals affecting AT adsorption-desorption behavior in the soil focus mainly on crystal silicate clay mineral(e.g. montmorillonite and kaolinite),but researches focusing on soil metal oxides,such as iron oxide,were,much less in number. Amorphous Fe oxides(AHOs Fe)is a kind of highly active iron oxide For its relatively high specific surface area and relatively big number of proton donating functional groups,AHOs Fe plays an important role in controlling the fate of organic pesticides. However,AHOs Fe is extremely unstable and ready to transform into crystalline iron oxide(e.g. goethite and hematite)under natural conditions,which makes it difficult to study characteristics of organic pollutants adsorption to AHOs Fe. In addition,what we had done in the past indicate that AHOs Fe in the soil was apt to form complex with SOM into organic-inorganic complexes,so soil adsorption capacity of butachlor was extremely and positively related to AHOs Fe content in the soil. Therefore,mere correlation analysis could not accurately determine contributions of SOM and AHOs Fe to adsorption of organic pollutants,and what is more,the mechanism of AHOs Fe adsorbing organic pollutants is still not clear. 【Method】In this study,artificially synthesized AHOs Fe and two typical types of soils,black soil from Heilongjiang and latosol from Guangdong were used,and half of the soil samples were surface coated with AHOs Fe. AT sorption behaviors were studied using the batch equilibrium method and its desorption behaviors were through one cycle of adsorption-desorption in various sorbents. At the meantime,in order to learn the extent of delay of AT desorption in the sorbents,delays of the initial desorptions in various adsorbents were quantified with Hysteresis index(HI). 【Result】 Results show that the isotherms of AT sorption in all the tested sorbents could well be described with the Frundlich equation(r≥ 0.996, p〈0.01). Compared with the soils,AHOs Fe exhibited a relatively high sorption capacity and high nonlinearity in sorption,Once coated with AHOs Fe,the AT sorption capacities of the two soils,black soil and latosol increased,significantly or by 56.3% and 43.8%,respectively. AT desorption delayed in all the sorbents and coating of AHOs Fe,decreased hysteresis coefficient(HI)of the AT desorption with increasing AT concentration in the case that the initial AT concentration was low,and acted reversely in the case that the initial AT concentration was high,indicating that the mechanism for delaying desorption in the sorbents varied with the initial AT concentration. Compared with the soils,AHOs Fe exhibited high hysteresis effect on AT desorption. But once it was used to coat the soils,it lowered the hysteresis effects of the soils. 【Conclusion】AHOs Fe has a relatively high sorption capacity and affinity for AT. However,in natural soils,complexing with soil organic matter(SOM)inhibits AHOs Fe capacity of directly adsorbing AT,because AHOs Fe has more SOM adsorbed or bonded on its surface,which indirectly affects AT adsorption by soil. Obviously,coating with AHOs Fe improves soil AT adsorption capacity,but also increases reversibility of AT sorption in the soil. All the findings in this study may help further understand roles of metal oxides,like AHOs Fe,in soil adsorbing AT-like organic pollutants and hence provide certain scientific basis for avoiding environmental risks of pollution with organic pollutants.
出处
《土壤学报》
CAS
CSCD
北大核心
2018年第1期148-158,共11页
Acta Pedologica Sinica
基金
国家自然科学基金项目(41571313)
广东省自然科学基金项目(2016A030313772,2015A030313570)
广州市科技计划项目珠江新星专项(201610010131)共同资助
关键词
无定型氧化铁
土壤
阿特拉津
表面包被
吸附
解吸
Amorphous Fe oxides
Soil
Atrazine
Surface coating
Adsorption
Desorption