氧化还原环境变化对河口沉积物硅影响的模拟
A simulation study on the effect of redox change on the Si in the estuarine sediment
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摘要: 氧化还原环境变化是水生态系统中普遍存在的环境现象，并可能对营养盐迁移转化产生显著影响.本文通过模拟分析好氧/缺氧状态下，典型河口沉积物硅释放及其赋存形态的差异，揭示了氧化还原环境变化对河口沉积物活性硅迁移转化的影响.研究结果表明，厌氧环境下，上覆水中溶解态硅的含量持续上升，在第30天可达4.23 mg·L-1；而好氧环境下上覆水中溶解态硅的含量维持在2.30 mg·L-1左右.其原因可能是厌氧环境下，表层沉积物中Fe/Mn氧化物发生生物还原，氧化层被逐渐破坏，促进溶解态硅的释放.另外，在短期培养过程当中，对于生物硅含量较低且其早期成岩改变程度较高的长江口沉积物而言，厌氧环境并不能有效促进沉积物生物硅的溶解.Abstract: Transition between oxic and anoxic conditions is a widespread phenomenon in the aquatic ecosystem, which could significantly affect the migration and transformation of the nutrients. In present study, the effects of redox conditions on the release patterns of dissolved silica (DSi) from benthic sediments, the variations of Si speciations of the sediments and mechanism behind these were be explored through simulation experiments using Yangtze Estuary sediments incubated under oxic and anoxic conditions. The DSi in the overlying water under anoxic incubation was increased gradually and could come 4.23 mg·L-1 at the end of the incubation (30 days), while the DSi under oxic incubation was stayed steady at 2.30 mg·L-1. Under anoxic conditions, the oxic layer in the surface sediment was destroyed gradually due to the reduction-reaction of the Fe/Mn oxides, and thus resulted in the release of significant amount of Si into the overlying water. Moreover, the anoxic incubation did not significantly stimulate the dissolution of biogenic silica particles within the experimental period, which may be due to the high extent diagenetic alteration and low contents of biogenic silica particles in the Yangtze estuary sediments.
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Key words:
- redox change /
- estuarine sediment /
- Si release /
- Si speciation /
- simulation research
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