三峡库区消落带土壤中溶解性有机质(DOM)吸收及荧光光谱特征

利用紫外-可见吸收光谱和三维荧光光谱技术,结合荧光区域积分法,分析了三峡库区消落带土壤DOM的地化特征.结果表明,各区县消落带土壤CDOM平均浓度大小顺序为:忠县丰都涪陵万州巫山云阳奉节开县,其中,忠县、丰都和涪陵土壤CDOM浓度a(355)]、芳香性(SUVA254)和疏水组分(SUVA260)明显高于其它区县,而其腐殖化程度(HIX)均低于其它区县.三峡库区消落带土壤DOM中含有类腐殖质荧光团A、C、M和类色氨酸荧光团T,其中紫外区类腐殖质荧光团A的荧光区域积分比例最大.另外,类色氨酸荧光团T与a(355)呈极显著相关(r=0.674,P0.01),影响CDOM浓度变化的主要因素是类蛋白荧光峰T.3D-EEM总荧光强度(TOT)可作为表征三峡库区消落带土壤CDOM荧光团浓度的指标.消落带土壤DOM腐殖化程度较低,生物可利用性较高.另外,消落带干湿交替作用对不同高程土壤DOM地化特征影响的差异较小,这可能与当地农业活动、沿岸植物生长以及DOM矿化过程有关.

Ultraviolet-Visible(UV-Vis) and Fluorescence Spectral Characteristics of Dissolved Organic Matter(DOM) in Soils of Water-Level Fluctuation Zones of the Three Gorges Reservoir Region

Ultraviolet-visible(UV-Vis) absorption spectroscopy and three-dimensional fluorescence spectroscopy, combined with fluorescence regional integration were conducted to investigate the geochemical characteristics of DOM extracted from soils of water-level fluctuation zones of the Three Gorges Reservoir Region. The results showed that the average CDOM concentrations in soils were in order of Zhongxian>Fengdu>Fuling>Wanzhou>Wushan>Yunyang>Fengjie>Kaixian. Additionally, in Zhongxian, Fengdu and Fuling, the CDOM concentration a(355)], aromaticity(SUVA₂₅₄) and hydrophobicity(SUVA₂₆₀) were all much higher than those at the other sampling sites, but the humification index(HIX) was lower. Four fluorophores were observed in all soil DOM samples, including three humic-like fluorescence peaks(A, C and M respectively) and one tryptophan-like fluorescence peak(T). Proportion of fluorescence regional integration of ultraviolet region humic-like A fluorophore was the highest as compared with the others. More importantly, tryptophan-like fluorophore(T) and a(355) showed significant correlation(r=0.674,P<0.01), indicating the variance of CDOM concentration was possibly dependent on T fluorophore. Meanwhile, the total integrated fluorescence intensity(TOT) of 3D-EEM was an appropriate parameter to characterize the total contributions of fluorophores in DOM. Furthermore, the humification degree of DOM in soils was low in comparison with higher biological availability. Conclusively it seemed that the influence of "alternation of wetting and drying" resulted from water-level fluctuation on the geochemical characteristics of soil DOM was not significant as expected. It might be related to local agricultural activity, littoral plant growth and DOM mineralization process.