Wang Qi-Lei, Jiang Tao, Zhao Zheng, Mu Zhi-Jian, Wei Shi-Qiang, Yan Jin-Long, Liang Jian
Huan Jing Ke Xue. 2015 Mar;36(3):879-87.
As an important geo-factor to decide the environmental fate of pollutants in watershed, soil dissolved organic matter (DOM) sampled from a typical agricultural watershed in the Three Gorges Reservoir area was investigated using ultraviolet-visible (UV-Vis) and fluorescence spectroscopies, to analyze and discuss the effect of different land uses including forest, cropland, vegetable field and residence, on soil DOM geochemical characteristics. The results showed that significant differences in DOM samples amongst different land uses were observed, and DOM from forest had the highest aromaticity and humification degree, followed by DOM from cropland. Although DOM from vegetable field and residence showed the highest dissolved organic carbon (DOC) concentration (average values 0.81 g x kg(-1) and 0.89 g x kg(-1), respectively), but the aromaticity was lower indicating lower humification, which further suggested that the non-chromophoric component in these DOM samples contributed significantly to total DOM compositions. Additionally, in all DOM samples that were independent of land uses, fluorescence index (FI) values were between 1.4 (terrigenous) and 1.9 (authigenic) , evidently indicating both the allochthonous and autochthonous sources contributed to DOM characteristics. Meanwhile, r(T/C) values in most of samples were higher than 2.0, suggesting that soil DOM in this agricultural watershed was heavily affected by anthropogenic activities such as agricultural cultivation, especially, vegetable field was a good example. Additionally, sensitivities of different special spectral parameters for reflecting the differences of DOM characteristics amongst different land uses were not identical. For example, neither spectral slope ratio (S(R)) nor humification index (HIX) could clearly unveil the various geochemical characteristics of soil DOM from different sources. Thus, simple and single special spectral parameter cannot comprehensively provide the detailed information of DOM, and combined application of UV-Vis and fluorescence spectroscopies is highly recommended.
作为决定流域污染物环境归宿的重要地理因素，采用紫外-可见（UV-Vis）光谱和荧光光谱对三峡库区典型农业流域采集的土壤溶解性有机质（DOM）进行了研究，以分析和探讨森林、农田、菜地和居民区等不同土地利用方式对土壤DOM地球化学特征的影响。结果表明，不同土地利用方式下的DOM样品存在显著差异，森林土壤DOM的芳香性和腐殖化程度最高，其次是农田土壤DOM。虽然菜地和居民区土壤DOM的溶解有机碳（DOC）浓度最高（平均值分别为0.81 g·kg⁻¹和0.89 g·kg⁻¹），但其芳香性较低，表明腐殖化程度较低，这进一步表明这些DOM样品中的非发色组分对总DOM组成有显著贡献。此外，在所有与土地利用方式无关的DOM样品中，荧光指数（FI）值在1.4（陆源）和1.9（自生）之间，明显表明陆源和自生来源都对DOM特征有贡献。同时，大多数样品的r（T/C）值高于2.0，表明该农业流域的土壤DOM受农业种植等人为活动的严重影响，特别是菜地就是一个很好的例子。此外，不同特殊光谱参数反映不同土地利用方式下DOM特征差异的敏感性并不相同。例如，光谱斜率比（S（R））和腐殖化指数（HIX）都不能清楚地揭示不同来源土壤DOM的各种地球化学特征。因此，单一的简单特殊光谱参数不能全面提供DOM的详细信息，强烈建议联合应用UV-Vis光谱和荧光光谱。
