Nano-scale Mechanisms of Metal(loid) Rhizostabilization in Desert Mine Tailings

描述(由申请人提供)： 干旱地区的含金属尾矿对附近居民的健康构成重大威胁，因为它们容易受到风的扩散和水的侵蚀。这些问题是广泛和持久的，因为受影响的地点缺乏正常的土壤稳定。植物稳定化是指对尾矿进行植被重建，以改善这些问题，目标是根区金属积累，以避免金属通过地上生物量进入食物链。植物根和微生物在促进矿物溶解-沉淀反应和相关金属固存方面的作用是一个活跃的研究领域，但由于植物-尾矿系统的地球化学异质性和微生物的复杂性，人们对植物-尾矿系统的反应轨迹和颗粒级金属形态的变化知之甚少。由于金属的形态或形态控制着它的生物有效性和毒性，因此需要研究金属形态和微生物动力学之间的耦合对植物稳定性的响应。 拟议工作的总体目标是确定尾矿植物稳定化过程中生物结构和污染物地球化学之间的多尺度过程联系。四个具体目标是：(I)推断金属(Loid)分子环境对特定颗粒风化过程的依赖；(Ii)评估生物(和地源)风化产物与特定微生物细胞和生物膜之间的空间相关性；(Iii)将这些固相生物地球化学的直接观测与尾矿孔隙水的时间和深度分辨测量(重点是金属污染物的移动性和生物有效性)联系起来；以及(Iv)在植物稳定化过程中，测量固相和溶解相动力学[(I)至(Iii)]对根际和散装尾矿中尾矿微生物和地球化学演变的影响。在这些目标中嵌入了另外一个目标，即在统计上整合从纳米到宏观尺度的“地理”和“生物”信息，以便更好地了解植物稳定过程以及与干旱环境中的尾矿场有关的暴露和毒性风险方面的可能结果。生物稳定性将在27个月的中观实验中使用一系列先进的工具进行探索，这些工具可以在高空间分辨率下询问根、微生物、矿物和金属的复杂联系。将产生大量和微观聚焦的X射线光谱、分子生物学/微生物生态学和水化学数据的时间序列，用于分析控制当地污染物环境的耦合过程。为了评估这些过程环节如何影响金属稳定这一更大的目标，我们将协调我们的“生物”和“地球”观测，以便它们探测相同的位置，一起从分子到宏观(介观水平)。这项研究既是及时的，也是必要的，因为美国西南部的增长正在爆炸式增长，社区正在靠近这些尾矿场的地方发展。

DESCRIPTION (provided by applicant): Metalliferous mine tailings in arid regions pose a significant health risk to proximal populations because they are prone to wind-borne dispersion and water erosion. The problems are extensive and persistent as impacted sites lack normal soil stabilization. Phytostabilization is the revegetation of mine tailings to ameliorate these issues with the goal of root zone metal accumulation to avoid metals from entering the food chain through above-ground biomass. The role of plant roots and microbes in promoting mineral dissolution-precipitation reactions and associated metal sequestration is an active area of research, but little is known about reaction trajectories and changes in particle-scale metal speciation of plant-tailings systems, owing largely to their geochemical heterogeneity and microbial complexity. Since the form or speciation of a metal controls its bioavailability and toxicity, research that probes coupling between metal speciation and microbial dynamics in response to phytostabilization is needed. The overarching goal of the proposed work is to identify multi-scale process-links between biological structure and contaminant geochemistry during phytostabilization of mine tailings. The four Specific Aims are: (i) to deduce the dependence of metal(loid) molecular environment on particle-specific weathering processes; (ii) to assess the spatial correlations between biogenic (and geogenic) weathering products and specific microbial cells and biofilms; (iii) to relate these direct observations of solid phase biogeochemistry with time- and depth-resolved measurements of tailings pore waters (focusing on the mobility and bioavailability of metal contaminants); and (iv) to measure the influence of solid and solution phase dynamics [(i) through (iii)] on the evolution of tailings microbiology and geochemistry both in the rhizosphere and in the bulk tailings over the course of phytostabilization. Embedded within these objectives is the additional goal of statistically integrating the nano- to macro-scale "geo" and "bio" information gained to better understand the phytostabilization process and possible outcomes in terms of exposure and toxicity risks associated with tailings sites in arid environments. Biostabilization will be probed over a 27 month mesocosm experiment using an array of advanced tools that can interrogate the complex associations of roots, microbes, minerals and metals at high spatial resolution. A time series of bulk and micro-focused X-ray spectroscopic, molecular biology/microbial ecology, and aqueous geochemical data will be generated for analysis of coupled processes that control the local contaminant environment. To assess how these process-links affect the larger goal of metal stabilization, we will coordinate our "bio" and "geo" observations so that they probe identical locations, together traversing molecular to macroscopic (mesocosm-level) scales. This research is both timely and necessary as growth in the US Southwest is exploding and communities are being developed in closer proximity to such tailings sites.