湖泊沉积物孔隙水磷酸盐含量原位监测技术研究进展

传统的沉积物孔隙水磷酸盐含量测定方法通常是采用离心法获取沉积物柱芯孔隙水,然后再进行磷酸盐含量测定。这种常规测定方法不仅破坏了沉积物的原本物理化学结构,而且分样间距多为厘米级,无法满足沉积物-水界面磷酸盐的高分辨率分布特征研究和释放通量的高精度估算要求。为克服传统监测技术破坏系统原始状态和分辨率低的弊端,近年来沉积物孔隙水磷酸盐原位监测技术迅猛发展,较为成熟的有透析装置技术(Dialysis peepers)、薄膜扩散平衡技术(Diffusive equilibrium in thin-films technique,DET)和薄膜扩散梯度技术(Diffusive gradients in thin-films technique,DGT)等。本文综述了透析装置技术、薄膜扩散平衡技术和薄膜扩散梯度技术的基本原理和应用实例,对比分析了他们各自的优缺点和发展应用前景。DGT作为一种新型、廉价的原位被动采样技术,具有原位和高分辨率监测的优点,被广泛应用于水体、沉积物和土壤等研究,在获取沉积物孔隙水磷酸盐含量及时空分布特征等方面优势突出。如何延长DGT胶体的使用寿命、提高监测的空间分辨率和实现多元素同步监测是其主要发展方向。大量研究表明,沉积物内源磷释放与沉积物中Fe-S的耦合循环存在密切联系,深入了解湖泊沉积物P-Fe-S的耦合生物地球化学循环过程是揭示湖泊内源磷释放机制的一把钥匙。快速发展的薄膜扩散梯度(DGT)技术及其与DET技术联用无疑为P-Fe-S耦合循环研究提供了有效手段,亟待在不同类型湖泊中应用和完善,为深刻揭示P-Fe-S耦合循环过程与机制提供独特信息。

Progress in Research on in-situ Monitoring Technology for Determining the Phosphate Contents of Sediment Pore Water

The phosphate contents of sediment pore water are usually obtained by means of centrifugation to get sediment pore water, and by chemical analysis. This traditional method not only destroys the original physical and chemical structures of the sediment, but also has lower spatial resolution (cm level). Thus, it cannot satisfy the high resolution investigation on the phosphate distribution characteristics at the sediment-water interface. In order to overcome the disadvantages of the traditional monitoring technology, in-situ monitoring technology has been developed rapidly in recent years, including dialysis peepers, diffusive equilibrium in thin-films technique (DET) and diffusive gradients in thin-films technique (DGT). This paper introduced the basic principle and application example of dialysis peepers, DET, DGT, and evaluated their respective advantages, disadvantages and development prospects. As a new inexpensive in-situ passive sampling technique, DGT has the advantages of in-situ and high resolution monitoring, and has been widely used in research on water, sediment and soil. How to prolong the service life of the DGT gels, to improve spatial resolution and to carry out synchronous monitoring on multiple elements are the main development directions. A large number of studies showed that the endogenous phosphorus release from sediments is closely associated with the coupled Fe-S cycling. Understanding the process of P-Fe-S biogeochemical cycle in lake sediments is a key to reveal the endogenous phosphorus release mechanism. The DGT technology provides an effective means for investigating the P-Fe-S cycle, and should be widely applied in different types of lakes.