Global variability in dissolved organic matter: implications for metal bioavailability and risk assessment

溶解有机物(DOM)是地球表面天然水体中普遍存在的一种物质。溶解有机物质对全球碳平衡至关重要，对养分循环和气候变化具有影响/控制作用。碳显然是生命过程中的重要元素，而DOM代表了地球上碳的一个潜在的动态成分。除了DOM在影响生产力和气候方面的作用外，DOM的第二个作用是结合污染物并影响其生物利用度和传输。毒性预测模型，如生物配基模型(BLM)，隐含地考虑了DOM对复杂金属的潜在作用，并减轻了它们的毒性。溶解有机物通常用溶解有机碳(DOC)来定量表示，并以每升毫克碳来报告。DOC是一个有用的指标，因为它可以很容易地使用碳分析仪进行测量，但在理解碳/养分循环、气候变化以及污染物的去向和迁移时，是否需要考虑DOM中的分子差异仍然是一个悬而未决的问题。众所周知，DOM是小分子羧酸和大分子组分的混合物。DOM的来源会影响合成。我的实验室和其他实验室已经证明，在光学性质、对金属和质子的反应性(酸碱和金属滴定)，甚至在毒性缓解方面，所有的DOM都不是一样的(较深的有机物往往比较浅颜色的有机物更具保护性)。这些差异在广泛的地理范围内的重要性还没有被评估，也没有对依赖DOM的建模和风险评估的具体影响。*我实验室的工作重点是来自加拿大安大略省南部的样品(以前的NSERC发现基金)和来自北美沿海的海洋/河口有机质(以前的NSERC CRD基金)。有必要将这项早期工作扩大到更广泛的样本范围，并使用越来越复杂的分析技术。利用探索基金，将从北美收集一套南北样本，并利用合作者和补充资金来源，还将从加拿大西北地区、巴西亚马逊盆地和中国的重庆三峡地区收集样本。*分子光谱学将被用作适用于所有样本的“指纹”技术。为了评估，将使用金属结合滴定法，重点是自由离子测量。对DOM与一套金属的结合进行表征将允许使用统一的模型来解释物种形成。在全球范围内，随着监管机构转向北美和欧洲开发的类似BLM的方法，重要的是确保在分子水平上“驱动”这些模型的DOC是相同的。

Dissolved organic matter (DOM) is a ubiquitous substance in natural waters on the earth's surface. Dissolved organic matter is crucial in global carbon balance with implications/controls on nutrient cycling as well as climate change. Carbon is obviously a significant element in life processes and DOM represents a potentially dynamic component of carbon on earth. In addition to DOM's role in influencing productivity and climate, a secondary role of DOM is to bind pollutants and influence their bioavailablity and transport. Toxicity prediction models such as the Biotic Ligand Model (BLM) implicitly take DOM into account due to its potential to complex metals and mitigate their toxicity.******Dissolved organic matter is often represented quantitatively as dissolved organic carbon (DOC) and reported in milligrams carbon per litre. DOC is a useful proxy because it can be readily measured, using a carbon analyzer, but it remains an open question if molecular differences in DOM need to be taken into account in understanding carbon/nutrient cycling, climate change, as well as pollutant fate and transport? DOM is known to be a mixture of small low molecular weight carboxylic acids along with macromolecular components. The source of DOM influences the composition. It has been shown by my lab, and others, that all DOM is not created equal in terms of optical properties, or in terms of reactivity towards metal and protons (acid-base and metal titrations), or even in terms of toxicity mitigation (darker organic matter tends to be more protective than lighter coloured organic matter). The significance of these differences on a wide geographic scale has not been assessed nor has the specific implications for DOM dependent modelling and risk assessment.******Work in my lab has focused on samples from Southern Ontario Canada (previous NSERC Discovery Grant) and marine/estuarine organic matter from coastal North America (previous NSERC CRD grant). It is necessary to expand this earlier work to a much wider range of samples and also using increasingly sophisticated analytical techniques. Using Discovery funds a North-South set of samples will be collected from North America and using collaborators and complementary funding sources, samples will also be collected from the Northwest Territories in Canada, the Amazon Basin in Brazil and the three gorges region of Chongqing province in China.******Molecular spectroscopy will be used as a "fingerprint'' technique applied on all samples. To assess metal binding titrimetry will be utilized with an emphasis on free ion measurement. Characterization of DOM binding to a suite of metals will allow for unified models to account for speciation. Globally, as regulators move towards the BLM-like approaches developed in North America and Europe it is important to make sure that the DOC that "drives" these models in the same at a molecular level.