Physicochemical insights into the environmental risks of metals

对有机化学品的生态风险(ERA)的评估通常包括对其持久性、生物累积和毒性的确定。对于金属和纳米材料等无机化学品来说，这种方法显然过于简单化了。例如，痕量金属形态的测量，包括络合反应的动力学，在环境系统中往往是至关重要的。同样，对于新出现的污染物，如纳米颗粒，胶体系统的稳定性(关于团聚)和导致颗粒溶解的(通常是非平衡的)反应肯定会强烈影响它们的生物利用度。因此，这项研究计划的总体目标是通过仔细研究导致几种新出现的污染物的生物吸收或迁移的机制，增加我们对环境风险的分子基础的理解。实验旨在得出有助于改进现有环境命运模型的见解。研究将侧重于三个关键的重要领域，这三个领域是更好地量化环境中的金属暴露所必需的：(1)确定新的含金属材料的老化(大致为持久性)；(2)更好地了解金属络合物和金属纳米颗粒的生物积累；以及(3)评估一些新出现的污染物的质量传输。对金属毒性(危险)的洞察，虽然不是本研究计划的主要重点，但仍将在金属生物利用度的转录组测序研究中获得。 发现赠款资金将用于从根本上洞察影响生态风险的关键生物物理化学过程。对于痕量金属，我们的重点将是确定化学形态对痕量金属生物有效性的作用，特别是金属络合物的贡献。项目将集中在有趣的、具有重要经济意义的稀土系列金属上。我们预计，它们(主要是)三价体的性质以及它们与有机物结合的强大能力将导致发现预测模型的重要例外，如生物配体模型。将优化分析技术，以便能够准确地测量化学形态。亲水性金属络合物的生物吸收率将被深入研究，而在生物配体模型等预测模型中通常忽略了这一点。 在某些情况下，有毒化学品的生物利用度可能受到化合物从水、土壤或沉积物转移到生物有机体表面的限制(质量传输限制)。这意味着，了解化学品的物理性质往往与了解其内在的化学反应能力一样重要。我们预计，对于某些化学品(较大的、缓慢扩散的化学品，如纳米材料)和某些环境(生物膜、土壤、沉积物)，质量传输将受到限制，这意味着为了获得对生物利用度的准确预测，必须建立动态模型。对于污染物，如纳米材料，我们的工作将被设计成仔细量化动态的、往往是非平衡的过程，如颗粒聚集和溶解。将探索新的纳米颗粒表征技术，如单颗粒电感耦合等离子体质谱(ICPMS)或分析性超速离心法，目的是在预测的低浓度下测量颗粒/团聚体。重点将放在提高我们对这些环境功能问题的机械理解上，以便在确定具有经济意义的新的(金属)污染物时，可以很容易地对其ERA进行优先排序。

Assessments of the ecological risk (ERA) of organic chemicals typically include determinations of their persistence, bioaccumulation and toxicity. For inorganic chemicals such as metals and nanomaterials, this approach is clearly an oversimplification. For example, trace metal speciation measurements, including the dynamics of complexation reactions are often critical in environmental systems. Similarly, for emerging contaminants such as nanoparticles, the stability of the colloidal systems (with respect to agglomeration) and the (often non-equilibrium) reactions leading to particle dissolution are certain to strongly influence their bioavailability. Therefore, the overall goal of this research program is to increase our understanding of the molecular underpinnings of environmental risk by carefully examining the mechanisms leading to the biological uptake or mobility of several emerging contaminants. Experiments are designed to lead to insights that will help improve existing models of environmental fate. Research will be focused on three key areas of importance that are required to better quantify the metal exposures in the environment: (i) determining the aging of novel metal containing materials (roughly persistence); (ii) developing better insight into the bioaccumulation of metal complexes and metallic nanoparticles and (iii) evaluating the mass transport of some emerging contaminants. Insights into metal toxicity (hazard), although not a main focus of this research programme, will nonetheless be acquired during transcriptome sequencing studies of metal bioavailability. Discovery grant funding will be used to gain fundamental insight into key biophysicochemical processes affecting ecological risk. For the trace metals, our focus will be on determining the role of chemical speciation on trace metal bioavailability with a particular emphasis on the contribution of metal complexes. Projects will be focused on the interesting and economically important lanthanide series of metals. We anticipate that their (primarily) trivalent nature and their strong capacity to bind organic matter will lead to the discovery of important exceptions to predictive models such as the Biotic Ligand Model. Analytical techniques will be optimized so that chemical speciation can be accurately measured. The biouptake of the hydrophilic metal complexes, generally neglected in predictive models such as the Biotic ligand model, will be studied thoroughly. In some cases, the bioavailability of toxic chemicals may be limited by the transfer of the compound from the water, soil or sediment to the surface of the biological organism (mass transport limitation). This implies that it is often just as important to understand the physical properties of chemicals as it is to understand their intrinsic chemical reactivity. We anticipate that for certain chemicals (larger, slowly diffusing chemicals such as nanomaterials) and in certain environments (biofilms, soils, sediments), mass transport will be limiting with the implication that dynamic models will be necessary in order to obtain accurate predictions of bioavailability. For contaminants such as nanomaterials, our work will be designed to carefully quantify dynamic and often non-equilibrium processes such as particle agglomeration and dissolution. Novel nanoparticle characterization techniques such single particle ICP-MS or analytical ultracentrifugation will be explored with the goal of measuring particle/agglomerate at their predicted low concentrations. Emphasis will be placed on improving our mechanistic understanding of these problems of environmental function so that as new (metal-based) contaminants of economic interest are identified, their ERA can be readily prioritized.