三峡库区消落带典型草本植物淹水浸泡后可溶性有机碳的释放特征

Characteristics of Dissolved Organic Carbon Release Under Inundation from Typical Grass Plants in the Water-Level Fluctuation Zone of the Three Gorges Reservoir Area

三峡库区消落带出露时草本植被生长旺盛,每年9月底蓄水后植物被淹没并开始腐解,导致有机体分解释放大量可溶性有机碳(DOC),可能对水质产生负面影响.研究选取三峡库区消落带典型草本植物,通过室内模拟浸泡实验,测定上覆水中DOC浓度变化过程,计算其释放速率与通量,旨在查明消落带草本植物淹水后DOC的释放特征,为库区植被修复与管理提供基础数据.结果表明,几种典型草本植物浸泡后上覆水的DOC浓度变化反映出草本植物淹水后DOC释放呈先增后减,后期趋于平稳的变化过程,在15 d左右达到峰值,表明消落带草本植物淹水浸泡后DOC随植物腐解快速释放,随后释放基本稳定,几种典型草本植物的DOC释放过程符合动力学过程.草本植物浸泡后DOC的释放浓度(最大为苦蒿的486.88 mg·L-1±35.97 mg·L-1,最小为稗子的4.18 mg·L-1±1.07 mg·L-1)、释放量(最大为苦蒿的50.54 mg·g-1,最小为水蓼的6.51mg·g-1)存在显著差异,主要受植物基质的影响,特别是植物基质的C/N值.实验浸泡植物的DOC释放量与相应草本植物基质的C/N值呈显著线性关系.

The water-level fluctuation zone of the Three Gorges Reservoir（TGR） exposes in spring and summer,then,green plants especially herbaceous plants grow vigorously.In the late of September,water-level fluctuation zone of TGR goes to inundation.Meanwhile,annually accumulated biomass of plant will be submerged for decaying,resulting in organism decomposition and release a large amount of dissolved organic carbon（DOC）.This may lead to negative impacts on water environment of TGR.The typical herbaceous plants from water-level fluctuation zone were collected and inundated in the laboratory for dynamic measurements of DOC concentration of overlying water.According to the determination,the DOC release rates and fluxes have been calculated.Results showed that the release process of DOC variation fitted in a parabolic curve.The peak DOC concentrations emerge averagely in the 15th day of inundation,indicating that DOC released quickly with organism decay of herbaceous plant.The release process of DOC could be described by the logarithm equation.There are significant differences between the concentration of DOC（the maximum DOC concentration is 486.88 mg·L-1±35.97 mg·L-1 for Centaureapicris,the minimum is 4.18 mg·L-1±1.07 mg·L-1 for Echinochloacrusgalli） and the release amount of DOC（the maximum is 50.54 mg·g-1 for Centaureapicris,the minimum is 6.51 mg·g-1 for Polygonumhydropiper） due to different characteristics of plants,especially,the values of C/N of herbaceous plants.The cumulative DOC release quantities during the whole inundation period were significantly correlated with plants＇ C/N values in linear equations.