底栖动物对沉积物微界面磷的二维扰动效应及其主要机制

As an important modifier in surface sediments of lakes, the influence of macrobenthos on the material flow in the vicinity of the sediment-water interface (SWI) has attracted high attention. The migration of phosphorus (P) across the SWI is one of the major pathway causing water eutrophication in lake. However, there lacks a clear understanding of bioturbation effects on P migration for a long time due to the use of the techniques capable of obtaining one-dimensional (1D) spatial information at a cm scale. This project will carry out a comprehensive study on bioturbation effects of the three dominant species in an eutrophic Lake Taihu, including corbicula fluminea, limnodrilus hoffmeisterib and chironomid larwae. Several techniques capable of obtaining high-resolution, 2D spatial information, including the fluorescent sediment profile imaging (f-SPI) , the planar optode sensor (PO) and the diffusive gradients in thin films technique (DGT), will be combined and used in a device. The spatial distribution of soluble reactive P (SRP) and effective concentration P will be measured using these techniques, based on which the 2D bioturbation effects will be discovered at a 2D, mm-submm levels. The influences of bioturbation on microenvironments in the vinicity of the SWI will be simultaneously studied, and the major mechanisms responsible for the bioturbation effects on SWI P will be elucidated in combination with the in situ, simultaneous measurements of P and relevant indicators in Lake Taihu.

作为湖泊表层沉积物的重要改造者，大型底栖动物扰动对沉积物界面物质流的影响一直受到高度的关注。沉积物磷界面迁移是造成水体富营养化的主要途径之一，但长期以来大量研究采用一维、低分辨（cm级）的研究手段，造成对界面磷生物扰动效应缺乏明确的认识。本项目以典型富营养湖泊太湖为研究背景，选择优势种河蚬、霍甫水丝蚯、摇蚊幼虫为研究对象，在对荧光示踪-沉积物剖面成像（f-SPI）、平面光极（PO）和薄膜扩散（DGT）等多种二维高分辨技术进行集成和装置化的基础上，通过获取沉积物微界面溶解态和有效态磷的分布信息，从二维、毫米-亚毫米尺度上揭示底栖动物对微界面磷的扰动效应；利用二维高分辨手段同步考察生物扰动对界面微环境的影响，结合湖区现场的原位分析，阐明底栖动物对界面磷扰动效应的主要机制。

沉积物作为湖泊污染物的重要蓄积场所和二次污染“源”，污染物在沉积物-水界面的迁移转化行为和机理一直受到高度的关注。其中生物扰动对沉积物-水界面污染物环境行为的影响更是研究的热点，但长期以来采用1维、低分辨（cm级）的研究手段，造成对生物扰动效应的研究缺乏明确的证据。本项目以太湖沉积物为研究背景，选择河蚬、霍甫水丝蚯、摇蚊幼虫和苦草作为研究对象，研制了实时观测沉积物pH值和DO变化的平面光极（PO）和分析沉积物活性离子的扩散梯度薄膜（DGT）等二维高分辨技术。并实现了两者的初步集成，通过获取沉积物微界面溶解态和有效态磷&铁的二维分布信息，揭示了底栖动物对微界面磷的二维扰动效应；同步考察了生物扰动对界面微环境理化特征的影响，阐明了水土界面生物扰动效应的主要机制。新技术的发展为深入研究沉积物-水界面污染物的环境行为提供了可靠有效的技术手段。