模拟酸雨淋溶条件下紫壤淋出液中溶解性有机质的三维荧光特性

THREE-DIMENSIONAL FLUORESCENCE CHARACTERIZATION OF DISSOLVED ORGANIC MATTER IN THE ELUATES LEACHED FROM PURPLE SOIL WITH SIMULATED ACID RAIN

运用三维荧光技术分析了模拟酸雨淋溶紫壤淋出液中溶解性有机质(dissolved organic matter,DOM)的组分与酸度及淋溶量的关系.研究结果表明,模拟酸雨淋溶紫壤淋出液中DOM荧光峰主要为类胡敏酸和类富里酸,荧光峰的中心位于Ex/Em=305—370 nm/420—450 nm和Ex/Em=260—270 nm/420—440 nm,在淋溶初期只出现类胡敏酸的荧光峰,当淋溶到750 mL时,出现类富里酸的荧光峰,且类胡敏酸的荧光峰较类富里酸强;随着酸雨淋溶量的增加,不同酸度淋出液中各种溶解性有机质的荧光强度均逐渐减弱,在淋溶初期减弱的幅度较大,溶解性有机质淋失率与酸雨pH呈负相关,表明酸雨作用下紫壤中大部分溶解性有机质在淋溶初期发生大量淋失,且酸度越大,有机质淋失率也越大;不同酸度淋出液溶解性有机碳(dissolved organiccarbon,DOC)随淋溶量和酸度的变化趋势与三维荧光的结果相一致,因此说明应用三维荧光技术分析淋溶液中溶解性有机质的组分和变化是可行的.

In this paper,three-dimensional fluorescence spectroscopy was applied to characterize the components of dissolved organic matter（DOM） in the eluates leached from purple soil with simulated acid rains.The result showed the leached DOM presented two main peaks in the excitation-emission matrix spectroscopy（EEMS）,one related to humin acid-like（HA-like） material,at Ex/Em=305—370 nm /420—450 nm,and the other related to UV fulvic acid-like（FA-like） at Ex/Em=260—270 nm/420—440 nm.Only HA-like were released from purple soil at the very beginning of leaching,while FA-like appeared when the leaching volume reached 750 mL,meanwhile peak-UV fulvic acid-like presents much weaker fluorescence intensity than peak-humin acid-like in all EEMS contour maps.The fluorescence intensities of the organic compounds in eluates decreased with increasing leaching volume of simulated acid rain and it has been reduced to a great degree in the initial phase of the leaching,the leaching ratio of DOM presents negative correlation with pH values of simulated acid rain,indicating that most DOM in purple soil can be lost in the early phase,and the leaching ratio of DOM increased with the decrease of pH values of simulated acid rain.Variation tendency of dissolved organic carbon in eluates with acidity and leaching volume of simulated acid rain is the same as that of DOM in the excitation-emission matrix spectroscopy,which indicating that it is feasible that three-dimensional excitation-emission matrix spectroscopy is employed to characterized the compositions of DOM in eluates.