基于光谱学方法研究土壤对堆肥中可溶性有机物的吸附行为

Study on Adsorption Behavior of Dissolved Organic Matter Onto Soil With Spectroscopic Method

可溶性有机物(DOM)作为土壤有机碳库的重要组成部分,其在碳氮循环、养分转化及污染物迁移等土壤生物化学过程中具有重要作用。研究不同类型土壤对堆肥DOM的吸附行为,可为堆肥在不同类型土壤中合理施用以及研究堆肥DOM的土壤环境化学行为提供理论参考。该研究选取黑土和潮土两种土壤,以石英砂作对比,开展不同吸附时间下三种介质对DOM的吸附试验,并采用紫外-可见光谱和三维荧光光谱结合平行因子法分析吸附反应溶液中DOM的光谱特征。结果表明, DOM在土壤中能很快被土壤颗粒吸附,在最初的20 min内吸附速率最快,随着吸附时间延长,吸附速率会逐渐减慢,并在260 min时达到平衡。在吸附时间为20 min时,黑土、潮土和石英砂对DOM的吸附量,分别占到260 min时吸附量的61.94%, 67.43%和61.57%。在吸附时间达260 min时,黑土对DOM的吸附量为9.30 mg·g^-1,潮土对DOM的吸附量为9.18 mg·g^-1,石英砂对DOM的吸附量为8.90 mg·g^-1。紫外-可见光谱分析结果显示,在200~600 nm波长范围内,不同吸附反应溶液中DOM的吸光度值随吸附时间延长均降低,在最初5 min内降低幅度大于5~260 min时段,此外,吸附反应溶液中DOM的SUVA(254)值先升高再降低。平行因子分析(PARAFAC)结果显示,吸附反应溶液中存在三个有机荧光组分,其中C1组分(325/410 nm)鉴定为UV类腐殖酸, C2组分(主峰为265/440 nm、次峰360/440 nm)鉴定为陆地植物源类腐殖酸, C3组分(主峰为370/485 nm、次峰290/485 nm)为典型的类腐殖质组分。C3组分的相对分子质量高于C1和C2组分,但芳香性构化程度低于C1和C2组分。黑土对C3组分的吸附能力最强,潮土对C1组分的吸附能力最强,石英砂对C2组分的吸附能力最强。综上所述,土壤类型和DOM自身的组成结构特征会影响土壤对DOM的吸附行为。该研究可为堆肥在不同类型土壤上合理施用提供理论依据。

Dissolved organic matter(DOM)is an important component of soil organic carbon pool,which plays a vital role in soil biochemical processes such as carbon and nitrogen cycle,nutrient conversion and pollutant migration.Exploring the adsorption behavior of DOM onto soil can provide a theoretical reference for the application of compost and the behavior of DOM in soil environmental.In this study,two different types of soils(black soil and fluvo-aquic soil),and quartz sand,were selected to carry out the adsorption experiment.UV-Visible spectroscopy and three-dimensional fluorescence spectroscopy combined with parallel factor method was applied to analysis the spectral characteristic of the DOM in the solution.The results showed that DOM was adsorbed by soil particles quickly.The adsorbed amount of DOM would gradually decrease with time.Due to the difference in properties of the three medium,the adsorbed amount of DOM is different.The adsorbed amount of DOM onto black soil,fluvo-aquic soil and quartz sand at 20 minutes,accounts for 61.94%,67.43%,61.57%of the adsorbed amount at 260 minutes.The adsorbed amount of DOM onto black soil,fluvo-aquic soil,and quartz sand up to 9.30,9.18 and 8.90 mg·g^-1 at 260 minutes.The UV-Vis spectroscopy showed that the absorbance of DOM in the solution decreased with adsorption time in the wavelength range of 200~600 nm,and the decrease degree of absorbance was larger in the first 5 minutes than that at 5~260 minutes.In addition,SUVA 254 values increased firstly and then decreased with time.The results of PARAFAC analysis showed that there were three organic fluorescent components in the adsorption equilibrium solution.The C1 component(325/410 nm)was identified as UV humic-like,originating from terrestrially-derived organic matter,and the C2 component(two peaks are 260/435 nm,350/435 nm)identified as humic-like,aromatic and derived primarily from terrestrial plant material,C3 component(two peaks are 280/500 nm,375/500 nm)is a typical humus-like component of terrestrial origin,the poor contribution of macrophytes,allochthonous.The relative molecular weight of the C3 component is higher than that of the C1 and C2 components,but the degree of aromatization is lower than that of the C1 and C2 components.Black soil shows lower adsorption capacity for C1 and C2 components than fluvo-aquic soil and quartz sand,but for C3 component higher than fluvo-aquic soil and quartz sand.Fluvo-aquic soil has the largest adsorption capacity for C1 component,and quartz sand has the largest adsorption capacity for C2 component.In summary,the soil types and the structural characteristics of DOM was the main factor that affect the adsorption behavior of DOM onto the soil.Therefore,this study could provide a theoretical reference for the rational application of compost on different types of soil.