同步荧光结合主成分与二维相关研究盐碱性土溶解性有机质组成与结构特征

为解决同步荧光光谱(SFS)荧光峰重叠而产生的应用局限性,应用同步荧光技术结合二维相关与主成分等方法,对重叠峰进行解析,研究土壤溶解性有机质(SDOM)组成与结构特征。选取河套灌区典型常见的芦苇、白杨、玉米、籽瓜等四种植被覆盖的土壤为研究对象,采集四个样点的土样,每个样点按0~20,20~40,40~60和60~80 cm等四层采集植被下土壤,共计16个土样,提取溶解性有机质,检测SFS。结果表明瓜地和玉米地SDOM荧光强度大于林地和芦苇地SDOM的荧光强度,瓜地SDOM荧光强度随着土层深度的增大而增大,而其他三种植被SDOM的荧光强度随着土壤深度的增大而减小,表明瓜地水浇过程中土层以淋溶作用为主,而其他土层以渗滤作用为主。应用主成分分析方法(PCA),识别出酪氨酸、色氨酸、微生物代谢产物、富里酸和胡敏酸等5种荧光组分,酪氨酸荧光峰出现了红移现象,表明瓜地土壤中的酪氨酸荧光强度明显高于其他三种植被土壤。基于二维相关光谱分析,芦苇土壤中的色氨酸与微生物代谢产物呈正相关变化趋势,光谱波段先后变化顺序为370 nm→337 nm→290 nm,表明组分变化顺序为富里酸→微生物代谢产物→色氨酸;玉米土壤中富里酸与胡敏酸呈正相关,波段变化顺序为318 nm→350 nm→420 nm→274 nm,表明组分变化顺序为微生物代谢产物→富里酸→胡敏酸→酪氨酸;林地土壤中酪氨酸、富里酸和胡敏酸呈正相关,波段变化顺序为270 nm→392 nm→426 nm→305 nm→337 nm,表明组分变化顺序为酪氨酸→富里酸→胡敏酸→色氨酸→微生物代谢产物;瓜地土壤中富里酸与胡敏酸呈正相关,而与酪氨酸呈负相关,波段变化顺序为410 nm→355 nm→334 nm→309 nm→275 nm,表明组分变化顺序为胡敏酸→富里酸→微生物代谢产物→色氨酸→酪氨酸。因此,运用SFS结合PCA与二维相关光谱分析SDOM的荧光光谱特征,识别荧光组分,揭示荧光组分的空间变化规律具有十分显著的效果。

The Composition and Structure of Dissolved Organic Matter in Saline Soil Were Studied by Synchronous Fluorescence Spectroscopy Combined with Principal Components and Two-Dimensional Correlation

In order to solve the research limitations caused by overlapping fluorescence peaks of synchronous fluorescence spectroscopy,the overlapping peaks were analyzed by using synchronous fluorescence technology in combination with two-dimensional correlation and principal components and other methods to study the composition and structural characteristics of soil dissolved organic matter(SDOM).The typical and common reeds,poplar,corn,melon four planted soils in hetao irrigation area were selected as the research objects,and soil samples from the four sample points were collected,a total of 16 soil samples were collected under four layers of vegetation,namely 0~20,20~40,40~60 and 60~80 cm.Dissolved organic matter was extracted and Synchronous fluorescence spectroscopy(SFS)was detected.SFS showed that melon and corn SDOM fluorescence intensity was greater than the woodlands and reed,melon SDOM fluorescence intensity increased with the increase of soil depth,while for the other three plantings SDOM fluorescence intensity decreased with the increase of soil depth,indicating that for the melon soil,in the process of watering soil layer gave priority to eluviation,and other soil layers gave priority to filtration.Principal component analysis(PCA)was used to identify five fluorescence components,including tyrosine,tryptophan,microbial metabolites,fulvic acid and humic acid.Based on two-dimensional correlation spectrum analysis,tryptophan in reed soil was positively correlated with the change trend of microbial metabolites.The change order of spectral bands was 370 nm→337 nm→290 nm,indicating that the change order of components was fulvic acid→microbial metabolites→tryptophan.There was a positive correlation between fulvic acid and humic acid in maize soil,and the change order of the band was 318 nm→350 nm→420 nm→274 nm,indicating that the change order of components was microbial metabolites→fulvic acid→humic acid→tyrosine.There was a positive correlation between tyrosine,fulvic acid and humic acid in woodland soil,and the change order of band was 270 nm→392 nm→426 nm→305 nm→337 nm,indicating that the change order of components was tyrosine fulvic acid→humic acid→tryptophan→microbial metabolites.There was a positive correlation between humic acid and humic acid,but a negative correlation between humic acid and tyrosine in the soil of melons,and the change order of band was 410 nm→355 nm→334 nm→309 nm→275 nm,indicating that the change order of components was humic acid→fulvic acid→microbial metabolite→tryptophan→tyrosine.Therefore,it is very effective to analyze the fluorescence spectral characteristicsof SDOM and identification of fluorescence componentby using SFS combined with PCA and two-dimensional correlation spectroscopy,and to reveal the spatial variation law of fluorescence components.