Anoxic sediments as a source of persistent organic pollutants: the role of organic carbon and iron reduction

缺氧沉积物作为持久性有机污染物的来源：有机碳和铁还原的作用

• 批准号: 289028153
• 负责人: Simone Peter, Ph.D.
• 金额: --
• 依托单位: Leibniz-Institut für Ostseeforschung Warnemünde (IOW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/289028153?language=en
• 关键词: Anoxic; sediments; source; persistent; organic

Pollution of the Baltic Sea is of great environmental concern and there is a need to understand processes of transport and transformation of persistent organic pollutants (POPs) in this environment. Sediments constitute a significant reservoir for POPs but can also act as a source of these chemicals to the water column. POPs strongly interact with organic carbon, both the solid and dissolved phase. In sediments organic carbon is one of the most efficient sorbent for POPs and in the dissolved phase, POPs can be transported along with dissolved organic carbon (DOC). Therefore, processes that are regulating organic carbon dynamics in the sediments might be a key to better explain the fate of POPs. Conventionally, anoxic sediments are perceived as zones of high organic carbon burial. However, iron-bound organic carbon can be mobilized under anoxic conditions during reductive iron dissolution and diffuse from the sediment pore water into the water column. Due to the high association of POPs with organic carbon, it is likely that concomitant with organic carbon also POPs are released from the sediment to pore water and consecutively co-diffuse with DOC into the water column. Thus, pollutant fate and dynamics are tightly related to change in oxygen regime in aquatic systems. The relevance of this process in aquatic systems, especially in the Baltic Sea where an increase in anoxia has been reported, is currently not known. We hypothesize that the change in oxygen concentration in sediments will affect the partitioning of POPs between solid and dissolved phase. Specifically, at anoxic conditions, POPs that are associated with iron-bound organic carbon will be remobilized into pore water from where the compounds can diffuse into the water column. For this study we will investigate the effect of oxygen depletion on POPs and DOC dynamics in sediments of the Gotland Deep in the Baltic Sea. The Gotland deep is usually anoxic over several years. But currently, an intrusion of oxygen-rich salt water exposes anoxic sediment layers to oxygen. This phenomenon opens great opportunities to study the effect of changing oxygen conditions on the fate of organic pollutants. In this project, several campaigns are planned to sample sediment and the water column at the Gotland Deep for DOC, iron and POPs concentrations, covering the time during oxic conditions and when anoxic conditions will be re-established. Additionally, fluxes of POPs and DOC from anoxic sediments will be quantified by incubation experiments under different oxygen conditions. The results will contribute (i) to understand the complex interactions of POPs and organic carbon and (ii) to quantify the remobilization of POPs under changing environmental conditions.

波罗的海的污染是一个重大的环境问题，有必要了解持久性有机污染物在这一环境中的迁移和转化过程。沉积物是持久性有机污染物的一个重要储存库，但也可能成为这些化学品进入水体的来源。持久性有机污染物与固态和溶解态的有机碳发生强烈的相互作用。沉积物中有机碳是持久性有机污染物最有效的吸附剂之一，在溶解相中，持久性有机污染物可以沿着溶解有机碳（DOC）迁移。因此，调节沉积物中有机碳动态的过程可能是更好地解释持久性有机污染物命运的关键。传统上，缺氧沉积物被认为是高有机碳埋藏区。然而，铁结合的有机碳可以在缺氧条件下，在还原铁溶解和扩散从沉积物孔隙水进入水柱。由于持久性有机污染物与有机碳的高度相关性，持久性有机污染物很可能与有机碳一起从沉积物中释放到孔隙水中，并连续与DOC共同扩散到水柱中。因此，污染物的命运和动力学密切相关的变化，在水生系统中的氧制度。目前尚不清楚这一过程在水生系统中的相关性，特别是据报道缺氧增加的波罗的海。我们假设，在沉积物中的氧浓度的变化会影响持久性有机污染物之间的分配固体和溶解相。具体而言，在缺氧条件下，与铁结合的有机碳有关的持久性有机污染物将重新进入孔隙水，这些化合物可从孔隙水扩散到水柱中。在这项研究中，我们将探讨缺氧对持久性有机污染物和DOC动态在波罗的海的哥特兰深海沉积物的影响。哥特兰深水区通常在数年内处于缺氧状态。但目前，富氧盐水的入侵使缺氧沉积层暴露在氧气中。这一现象为研究氧气条件变化对有机污染物命运的影响提供了很大的机会。在该项目中，计划开展几次活动，对哥得兰深水区的沉积物和水柱进行采样，以确定DOC、铁和持久性有机污染物的浓度，涵盖了好氧条件期间和缺氧条件将重新建立的时间。此外，缺氧沉积物中的持久性有机污染物和溶解有机碳的通量将量化培养实验在不同的氧气条件下。研究结果将有助于（一）了解持久性有机污染物与有机碳之间复杂的相互作用，以及（二）量化持久性有机污染物在不断变化的环境条件下的再活化情况。