The role of Sphagnum decomposition in metal accumulation and release in peatlands (SMAP)

泥炭地具有保留和储存大量主要和微量元素的潜力。由于大气沉积，来自自然或人为来源的微量元素到达营养型泥炭地（沼泽）的表面。主要和微量元素在以溶质或颗粒形式沉积后，可通过植物吸收、物理夹带或有机物在不同分解阶段的络合作用被保留。北方泥炭地优势种Sphagnum sp.对微量金属积累极为敏感，能有效吸收和保留微量元素可溶性阳离子（如Cu+2、Hg+2和Pb+2）。泥炭地产生的溶解有机质可以被动员起来，并作为金属从泥炭地运输到河流系统的主要载体。众所周知，水文条件——干旱条件之前的大雨事件——决定了泥炭地的金属出口。由于这些条件，泥炭地通气部分的水文连通性受到刺激，连接了先前动员的金属池。然而，泥炭地地表微量元素的吸收和释放以及季节和气候变化对泥炭地退化的影响尚不清楚。基于体外Sphagnum分解和金属吸收实验，本研究（SMAP）旨在确定Sphagnum凋落物的分解过程，即更不稳定的化合物优先降解转化和更耐药的化合物的选择性保存，在多大程度上影响不同微量元素向水文系统的释放或在泥炭沉积物中的保留。这项研究有望解开泥炭形成的第一阶段对泥炭增生过程中金属的积累和释放的作用。此外，预期的结果将提高我们对金属信号形成的关键步骤的理解，这将导致对泥炭记录作为历史大气金属沉积古档案的重新评价。

Peatlands have the potential to retain and store large amounts of major and trace elements. Due to atmospheric deposition, trace elements from natural or anthropogenic sources reach the surface of ombrotrophic peatlands (bogs). After their deposition as solutes or particles, major and trace elements can be retained through plant uptake, physical entrainment or complexation by organic matter at different stages of decomposition. Due to its extreme sensitivity to trace metal accumulation, Sphagnum sp. (the dominant species in boreal peatlands) can effectively take up and retain soluble cations of trace elements (e.g., Cu+2, Hg+2, and Pb+2). Dissolved organic matter produced in peatlands can be mobilized and act as a major carrier of metal transport from peatlands to fluvial systems. Hydrologic conditions – heavy rain events preceded by dry conditions – are known to determine metal export from peatlands. Due to these conditions, the hydrological connectivity in the aerated part of peatlands is stimulated, connecting the pools of previously mobilized metals. However, less well known are the role of Sphagnum sp. degradation for the uptake and release of trace elements in the surface of the peatlands and the effects of seasonal and climatic changes on degradation. Based on in vitro Sphagnum decomposition and metal uptake experiments, the proposed study (SMAP) intends to determine to what extent the decomposition process of Sphagnum litter – i.e., the preferential degradation and transformation of more labile compounds and the selective preservation of more resistant compounds – affects the release of different trace elements to the hydrological system or their retention in the peat deposit. This research is expected to disentangle the role of the first stages of peat formation for the accumulation and release of metals during peat accretion. In addition, the expected results will improve our understanding of the crucial step of metal-signal formation, which will lead to the re-evaluation of the current use of peat records as palaeo-archives for historical atmospheric metal deposition.