光谱学与光谱分析, 2019, 39 (5): 1477, 网络出版: 2019-05-13  

不同海拔下青海草甸土中溶解性有机质的荧光光谱特征

Fluorescence Spectral Characteristics of Dissolved Organic Matter in Meadow Soils in Qinghai under Different Altitudes
作者单位
1 中国科学院科技战略咨询研究院, 北京 100190
2 中国科学院大学, 北京 100049
3 生态环境部环境规划院, 北京 100012
4 中国环境科学研究院环境基准与风险评估国家重点实验室, 北京 100012
摘要
溶解性有机质(DOM)是土壤中对气候变化较为敏感的组分, 在重金属迁移转化、 碳释放等土壤环境化学过程中占有重要地位。 同时, 青藏高原也是对气候变化最为敏感的地区之一。 而应用荧光光谱来探明气候条件的变化对土壤DOM的影响, 从而确定气候变化背景下DOM的环境化学行为方面的研究较少。 通过采集青海板达山不同海拔高度下(2 800, 3 000, 3 300, 3 600和3 900 m)的草甸土, 应用三维荧光-平行因子分析的方法测定土壤中DOM的荧光光谱, 揭示草甸土中DOM的来源、 组成和性质对不同海拔气候条件的响应特征。 结果表明: 海拔对土壤理化性质有重要影响。 随海拔升高, 土壤pH显著降低, 而有机质的平均值则从6.32%提高至13.75%, 但溶解性有机碳含量未有显著性变化。 同时, 海拔对DOM的来源与性质也产生影响。 DOM的BIX指数随海拔升高而升高, 表明: 微生物源对高海拔土壤中DOM的贡献更高, 可能是由于高海拔下的低温限制了植物残体等的分解和有机质的矿化。 而FI指数(1.332~1.621)处于自生源特征值(FI=1.9)和陆生源特征值(FI=1.4)之间, 表明: DOM的来源既有自生微生物活动产生, 又有植物残体与根际分泌物等陆源的输入。 但HIX指数在不同海拔土壤DOM中无显著性差异, 说明: 海拔的升高未显著改变DOM的腐殖化程度。 平行因子分析的结果显示, 在青海草甸土DOM中识别出6个有机组分(C1—C6), 分别是: 两个类胡敏酸组分(C2和C4)、 两个类富里酸组分(C1和C3)、 一个水溶微生物副产物(C5)和一个类蛋白组分(C6)。 其中, 类富里酸和类蛋白分别是DOM中占比最高(54.69%~59.78%)和最低(5.42%~8.47%)的组分, 类胡敏酸则平均占DOM的25.08%。 对不同海拔下DOM的有机组分进行主成分分析, 结果显示: 各海拔土壤DOM的样点基本分散开, 这说明DOM的组成对海拔高度具有响应。 类富里酸组分C3、 类胡敏酸组分C4和类蛋白组分C6对各DOM组成差异的贡献最大。 随海拔升高, C3和C6的相对比重显著升高, C4则显著降低。 这说明高海拔的气候条件对类富里酸和类蛋白的生成有增强作用, 但限制了类胡敏酸的产生。 研究表明: 不同海拔气候条件下, 青海草甸土中DOM的来源、 性质和组成均有重要差异, 研究结果对评估青藏高原地区的土壤碳库, 并为预测全球气候变化背景下DOM对土壤中重金属迁移转化和碳循环等环境化学行为的影响提供理论基础。
Abstract
Dissolved Organic Matter (DOM) is a component that is sensitive to climate change in soil and plays an important role in environmental chemical behaviors such as transportation and transformation of heavy metals and carbon release. Meanwhile, the Qinghai-Tibet Plateau is one of the most sensitive region to climate change all over the world. However, few researches are focusing on the application of fluorescence spectroscopy to ascertain the impact of climate change on soil DOM and to reveal the response of environmental chemical behaviors of DOM to climate change. In this study, fluorescence spectral characteristics of DOM in meadow soils in Daban Mountain, Qinghai, under different altitudes (2 800, 3 000, 3 300, 3 600 and 3 900 m) was determined by using three-dimensional fluorescence spectroscopy and parallel factor analysis to reveal the response of the sources, compositions and properties of DOM to climatic conditions at different altitudes. The results showed that altitude had an important influence on the physical and chemical properties of the soil. With the increase of altitude, the soil pH decreased significantly, while the average organic matter increased from 6.32% to 13.75%. However, there was no significant change in the content of dissolved organic carbon at different altitudes. Additionally, altitude also had an impact on the origin and nature of DOM. The BIX index of DOM increased with the rise of altitude, indicating a more contribution to DOM in high-altitude soils by microbial sources, which may be due to a lower decomposition of plant residues and the mineralization of organic matter induced by low temperature at high altitudes. The FI index (1.332~1.621) was found to be lower than the eigenvalue indicating an autogenous source (FI=1.9) and the one indicating a terrestrial source (FI=1.4), showing that the DOM not only derived from the autogenous microbial activity, but also terrestrial input, such as plant residue and root exudates. However, the HIX index had no significant difference in soil DOM at different altitudes, indicating that elevation of altitude did not significantly change the degree of DOM humification. The results of parallel factor analysis showed that there were six organic components (C1—C6) in the DOM of meadow soil in Qinghai : which are two humic acid components (C2 and C4), two fulvic acid components (C1 and C3), and one water-soluble microbial by-product (5) and one protein-like component (6). Among them, fulvic acid-like and protein-like were the components with the highest proportion (54.69%~59.78%) and the lowest proportion (5.42%~8.47%) of DOM, respectively, while humic acids accounted for an average of 25.08% of DOM. The principal component analysis of the organic components in DOM at different altitudes showed that the samples of DOM at different altitudes were basically dispersed, indicating that the composition of DOM was responsive to altitude. The fulvic acid-like component (C3), the humic acid-like component (C4) and the protein-like component (C6) contributed the most to the differences in DOM compositions. With the increasing altitude, the relative proportions of C3 and C6 increased significantly, while the C4 decreased significantly. This indicated that the climate conditions at high altitude enhanced the production of fluvic acid and protein, but limited the production of humic acids. It could be concluded that the source, nature and composition of DOM in meadow soils of Qinghai have significant differences under different altitude conditions. And the results may provide theoretical basis for the assessment of soil carbon pool in Qinghai-Tibet Plateau and for the prediction of the transportation and transformation of heavy metals and carbon cycle under global climate change.

杨威杉, 李猛, 孙笑蕾, 胡华玲, 黄丽娟. 不同海拔下青海草甸土中溶解性有机质的荧光光谱特征[J]. 光谱学与光谱分析, 2019, 39(5): 1477. YANG Wei-shan, LI Meng, SUN Xiao-lei, HU Hua-ling, HUANG Li-juan. Fluorescence Spectral Characteristics of Dissolved Organic Matter in Meadow Soils in Qinghai under Different Altitudes[J]. Spectroscopy and Spectral Analysis, 2019, 39(5): 1477.

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