Dissolved organic matter in aquatic systems: factors affecting its role in greenhouse gas formation

溶解性有机物（DOM）是一种复杂的物质混合物，对水生态系统的物理和化学环境有着非常重要的影响。 DOM控制或影响许多生物过程，例如许多痕量金属的吸收。 虽然DOM产生于集水区的陆地和水生组成部分，但营养贫乏的北方湖泊中的大部分DOM起源于系统的陆地部分。 当这种物质在生态系统中运输时，它会经历影响其数量和质量的变化。 这些变化主要是由光化学和微生物过程引起的，它们导致DOM化学结构的改变和DOM命运的改变。 DOM在水环境中的损失主要有两种机制。 一些进入湖泊的DOM转化为颗粒物，其中一些最终进入湖泊沉积物，而另一些最终成为二氧化碳，一种重要的温室气体。 DOM对温室气体排放的潜在贡献很大。重要的是要了解这个来源有多大。 导致温室气体的光化学途径的相对重要性随着湖泊pH值的降低而增加，并且还受到其他外部因素的影响。 我们将量化这些因素的重要性。 此外，有关DOM的化学性质的内在因素会影响分解途径;同样，我们将量化这些关系。后一项发现对京都雅阁要求的影响将是本研究的重点。

Dissolved organic matter (DOM) is a complex mixture of substances that affects the physical and chemical environment of aquatic ecosystems very substantially.  DOM controls or influences many biological processes, e.g. the uptake of many trace metals.  Although DOM is produced in both the terrestrial and aquatic components of catchments, most of the DOM in nutrient-poor Boreal lakes originates in the terrestrial part of the system.  As this material is transported through the ecosystem, it undergoes transformations that affect its quantity and quality.  These changes are largely caused by photochemical and microbial processes, and they result in both altered chemical structure of the DOM and altered fate of the DOM.   There are two major loss mechanisms for DOM in the aquatic environment.  Some of the DOM that is input to lakes is transformed into particulate matter, some of which ends up in lake sediments, while some ends up as carbon dioxide, an important greenhouse gas.  The potential contribution of DOM to greenhouse gas emissions is large. It is important to understand how large this source is.  The relative importance of the photochemical pathway which leads to greenhouse gases increases as lake pH decreases, and is also affected by other external factors.  We will quantify the importance of these factors.  In addition, intrinsic factors concerning the chemical nature of the DOM affect the breakdown pathway; again, we will quantify these relationships. The implications of the latter finding to requirements of the Kyoto accord will be the focus of this study.