Bubble-mediated transport and aerosolization of microorganisms: implications for natural and manual aeration to adjacent communities

气泡介导的微生物运输和雾化：对邻近群落的自然和手动曝气的影响

• 批准号: 2037775
• 负责人: Sarah Preheim
• 金额: $ 32.9万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2037775&HistoricalAwards=false
• 关键词: Bubble; mediated; transport; aerosolization; microorganisms

Aeration (the introduction of air bubbles into water) either through mechanical systems or through wind/wave action represents a common way for oxygen to become dissolved into water bodies. Such processes are important to prevent the formation of “dead-zones”, areas where the oxygen concentration is too low to support animal life. Because bubbles are lighter than water, they naturally rise to the surface. Small particles like sediment, microbes, toxins, and organic matter, as well as gases can be swept along with the bubble as it travels to the surface. When the bubble bursts at the surface, bacteria and other particles and gases can disperse through the air, increasing the chances of human exposure. While we understand the power of bubbles to aerosolize particles into the air, the underlying causes are poorly understood. The goal of this project is to understand how environmental conditions such as bubble size, microbial cell size, and water chemistry affects microbial transport and aerosol generation. This goal will be achieved using both controlled laboratory experiments and field study at Rock Creek (Pasadena, MD, USA), a low oxygen water body that has a mechanical aeration system to prevent dead zone formation. This research is based on the hypothesis that changes in bubble and microbial cell size, as well as water chemistry parameters can be used to predict microbial aerosolization. The public will be engaged in this research through citizen science projects, increasing the scientific literacy of the Nation. Successful completion of this research has potential to protect human and ecological health through prevention and control of pathogens and toxin aerosolization. Microorganisms live in an environment filled with air-water interfaces, such as those found at the surface of a lake, around gas bubbles from aeration, or in water pockets trapped in soils. The behavior of microorganisms at these multiphase interfaces is largely understudied, in spite of their importance in controlling air-water-soil mass transfer. The goal of this research is to address these gaps in knowledge to understand how bubble size, microbial cell size, and water salinity affects bubble-mediated microbial transport and aerosolization. The research is guided by the hypothesis that changes in environmental variables (bubble size, microbe size, salinity) will result in differences in transport and aerosolization that can be predicted from equations and relationship previously derived for model colloids. These predictions will be tested across multiple scales using diverse microorganisms ranging in size from viruses to eukaryotic algae under controlled laboratory conditions to measure interfacial and small-scale transport. Field-scale transport will be measured during mechanical aeration of a low-oxygen aquatic environment (Rock Creek, Pasadena, MD). Interactions and bubble-mediated transport and aerosolization will be quantified with state-of-the-art particle tracking methods, flow cytometry, quantitative polymerase chain reaction, and microbial community characterization. A diverse group of high school, undergraduate, and graduate students will be trained in inter-disciplinary research topics and the public will be engaged in the research through a number of outreach activities. These experiments will result in quantifiable relationships that can be used to understand how bubble-generating processes will impact microbial dispersal within the water column and into aerosols, which can be applied to microbial ecology or microbial risk assessment for novel or worsening microbial threats.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

通过机械系统或通过风/波作用的曝气（将气泡引入水中）是氧气溶解到水体中的一种常见方式。这样的过程对于防止“死区”的形成是很重要的。“死区”是指氧气浓度过低而无法维持动物生命的区域。因为气泡比水轻，它们自然会浮到水面。沉积物、微生物、毒素、有机物等小颗粒，以及气体，都可以随着气泡漂到海面上。当气泡在表面破裂时，细菌和其他颗粒和气体可以通过空气扩散，增加人类接触的机会。虽然我们知道气泡能使颗粒雾化到空气中，但对其根本原因却知之甚少。该项目的目标是了解气泡大小、微生物细胞大小和水化学等环境条件如何影响微生物的运输和气溶胶的产生。这一目标将通过控制实验室实验和在Rock Creek （Pasadena， MD， USA）的现场研究来实现，这是一个低氧水体，具有机械曝气系统以防止死区形成。本研究基于气泡和微生物细胞大小的变化以及水化学参数可以用来预测微生物雾化的假设。公众将通过公民科学项目参与到这项研究中来，提高国民的科学素养。这项研究的成功完成有可能通过预防和控制病原体和毒素雾化来保护人类和生态健康。微生物生活在充满空气-水界面的环境中，比如在湖表面，在曝气产生的气泡周围，或者在土壤中的水袋中。微生物在这些多相界面上的行为在很大程度上还没有得到充分的研究，尽管它们在控制空气-水-土壤传质方面很重要。本研究的目标是解决这些知识上的空白，以了解气泡大小、微生物细胞大小和水盐度如何影响气泡介导的微生物运输和雾化。该研究的指导假设是，环境变量（气泡大小、微生物大小、盐度）的变化将导致运输和雾化的差异，这可以通过先前导出的模型胶体的方程和关系来预测。这些预测将在多个尺度上进行测试，在受控的实验室条件下，使用从病毒到真核藻类大小不等的各种微生物来测量界面和小规模运输。将在低氧水生环境（Rock Creek, Pasadena， MD）的机械曝气过程中测量现场尺度的输运。相互作用、气泡介导的运输和雾化将通过最先进的颗粒跟踪方法、流式细胞术、定量聚合酶链反应和微生物群落表征进行量化。一个由高中生、本科生和研究生组成的多元化群体将接受跨学科研究课题的培训，公众将通过一系列外展活动参与研究。这些实验将产生可量化的关系，可用于了解气泡产生过程如何影响微生物在水柱内和气溶胶中的扩散，这可以应用于微生物生态学或微生物风险评估，以应对新的或恶化的微生物威胁。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。