Carbon Nanotubes in Soils: Transport, Filtration, and Impact on Soil Microbial Community

碳纳米管（CNTs）的应用越来越广泛，包括电子、光学、医疗和结构复合材料技术。由于其在大规模工业生产中的预期作用，毫无疑问，碳纳米管最终将进入我们的水生环境。与其他纳米颗粒相比，碳纳米管具有不同寻常的物理化学特性，特别是其非常大的纵横比和在水溶液中的高度捆绑（聚集）状态，这使得对其聚集和运输行为的有意义的理论预测变得困难。此外，由于缺乏碳纳米管在多孔介质中传输的实验室数据，因此对其在地下环境中的潜在迁移和命运知之甚少。特别令人感兴趣的是需要评估碳纳米管对地下水含水层的潜在污染。碳纳米管污染地下水可能来自垃圾填埋场渗滤液、废水渗透和土地应用。因此，了解碳纳米管在土壤中的运移程度将是预测地下含水层污染风险的关键。此外，由于碳纳米管在土壤剖面中保留，因此必须考虑其对土壤微生物生态的影响，因为最近的研究表明碳纳米管具有抗菌作用。拟议研究的总体目标是评估碳纳米管在土壤中的运输和保留程度，以及保留的碳纳米管对土壤微生物群落的影响。将建立碳纳米管在土壤中运输的最坏情况，这将使他们能够预测潜在地下水含水层受到污染的可能性。此外，他们将建立保留碳纳米管影响土壤微生物生态的条件。两种假设指导了他们的研究：(i)碳纳米管在土壤中的流动性相对有限，因为碳纳米管的大长宽比及其高度聚集（捆绑）状态将促进物理化学过滤和拉伸的广泛去除；（ii）由于碳纳米管的有效保留，特别是通过拉伸，碳纳米管将在土壤中积累，从而影响土壤微生物群落。为完成建议的工作，他们将：(1)选择并表征单壁碳纳米管（SWNTs）和多壁碳纳米管（MWNTs）；(2)选择并表征土壤和模拟多孔介质；(3)评估填充柱中碳纳米管的运输和滞留；(4)评估溶液化学扰动对滞留碳纳米管的动员（释放）；(5)评估滞留碳纳米管对土壤微生物的影响；(6)评估最坏情况和对土壤和地下水的潜在影响。该研究项目将包括培养一名博士生和两名本科生。关于纳米材料在环境中的运输和纳米材料对地下环境的地球微生物学的潜在影响的特殊模块将被添加到本科课程中。他们将与耶鲁皮博迪博物馆合作，为博物馆的学校项目和教师研讨会开发适当的模块，讨论纳米技术对环境和社会的影响。

CBET-0828795ElimelechCarbon nanotubes (CNTs) are emerging in a variety of applications, including electronic, optical, medical, and structural composite technologies. Because of their anticipated role in large-scale industrial production, there is little doubt that CNTs will ultimately find their way into our aquatic environment. The unusual physicochemical characteristics of CNTs compared to other nanoparticles, particularly the very large aspect ratio and highly bundled (aggregated) state in aqueous solutions, preclude meaningful theoretical predictions of their aggregation and transport behavior. Furthermore, because of the lack of laboratory data on CNT transport in porous media, very little is known about their potential mobility and fate in subsurface environments. Of particular interest is the need to assess the potential contamination of groundwater aquifers by CNTs. Contamination of groundwater with CNTs may originate from landfill leachates, wastewater infiltration, and land applications. Therefore, understanding the extent of CNT transport in soils will be the key to predicting the risk of contamination of underlying groundwater aquifers. Furthermore, because of CNT retention within the soil profile, its impact on soil microbial ecology must be considered in light of recent studies indicating antibacterial effects of CNTs. The overall objective of the proposed research is to assess the extent of transport and retention of CNTs in soils and the impact of retained CNTs on the soil microbial community. Worst case scenarios for CNT transport in soils will be established, which will then enable them to predict the potential for contamination of underlying groundwater aquifers. Furthermore, they will establish the conditions under which retained CNTs influence the soil microbial ecology. Two hypotheses guide their research: (i) the mobility of CNTs in soils will be relatively limited as the large aspect ratio of the nanotubes and their highly aggregated (bundled) state will promote extensive removal by physicochemical filtration and straining, and (ii) because of their effective retention, particularly via straining, CNTs will accumulate in soils and thus will influence the soil microbial community. To complete the proposed work, they will: (1) select and characterize single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes MWNTs, (2) select and characterize soils and model porous media, (3) evaluate transport and retention of CNTs in packed columns, (4) evaluate mobilization (release) of retained CNTs by perturbations in solution chemistry, (5) assess the impact of retained CNTs on soil microbiology, and (6) evaluate worst case scenarios and potential effects on soil and groundwater. The research program will include the training of a doctoral student and two undergraduate students. Special modules on transport of nanomaterials in the environment and on the potential implications of nanomaterials on the geomicrobiology of subsurface environments will be added to undergraduate courses. They will work with the Yale Peabody Museum to develop appropriate modules for the museum's School Programs and Teacher's Workshops on environmental and societal impacts of nanotechnology.