Volatilization dynamics in wetland systems

jaffe湿地，无论是天然的还是设计的，都是一种具有成本效益的修复地下水的工具，这些地下水被排放到这些湿地的挥发性有机化合物（VOCs）污染。湿地修复的广泛使用受到了修复机制的速率和时间尺度的不确定性的阻碍。挥发可能是这些去除机制中最不为人所知的。初步的实验室和建模结果表明，挥发是主要的去除途径，挥发的强度和机制高度依赖于目标化合物的物理化学性质。然而，我们对挥发途径和速率的物理化学驱动因素的理解仍然不完整，这排除了任何预测建模技术来准确估计湿地VOC通量。为了弥补这一知识空白，必须解决挥发性化合物在饱和浅层植被土壤中运输的根本问题：挥发性化合物通过湿地植物的气相运输和蒸腾驱动的运输之间的平衡是什么？植物介导的挥发在多大程度上随植被类型的变化而变化？如何用预测模型恰当地描述植物对挥发性有机化合物的吸收，以及如何在实地验证这些模型？挥发性化合物在多大程度上分裂成地下气泡，气泡沸腾如何促进大气中挥发性有机化合物的通量，气泡动力学与植物增强气体传输之间的相互作用是什么？PI将通过新兴湿地植物对挥发的基本动态进行全面研究。测量将跨越多个尺度，从控制实验中的单茎到实地试点研究。实验计划将包括：(1)系统的实验室水培研究，使用多种挥发示踪剂和单茎，探索化合物的物理化学性质与其挥发速率和机制之间的基本关系；(2)温室中观研究，验证饱和土壤条件下植物挥发的预测模型，并研究污染物去除率的种间变异性；(3)在淡水湿地进行试点，量化湿地系统VOC去除率的时空异质性。本研究的一个重要目标是开发单井推拉式钻井技术。将在温室生态系统中开发并在现场实施的技术，为评估不同湿地生态系统的挥发率提供了一种新颖而有价值的工具，在其他机制确定湿地系统根际与大气之间的气体交换是不可行的。就更广泛的影响而言，拟议的研究将解决有关化学物质在饱和土壤和植被中的运输的基本问题，这些问题对整个地球科学都有影响。测量地下水-大气气体交换的拟议技术创新将具有多学科应用，包括湿地的设计和管理以及自然湿地衰减的评估。这项工作将资助一名博士生，并为其他研究生的教育做出贡献。他的实验室和外部合作者的实验室，包括罗格斯大学（Rutgers University）和草地研究所（Meadowlands Research Institute）。来自不同学校的本科生将通过正在进行的REU项目参与其中。这个REU项目在招收少数民族和女学生方面取得了成功。本科生将参与毕业论文研究。通过参与QUEST，一个由普林斯顿大学教职员工教授的高年级小学教师的科学研究所，以及参与Stony Brook-Millstone流域协会的教育项目，该协会还积极与市政官员、公民和企业就影响当地环境的决策进行对话，计划向社区推广。这项研究的结果将纳入本科（环境工程实验室）和研究生（水质建模）课程，并将通过在国家会议上的报告和同行评审的期刊出版物向科学界传播。

1133281 PI JaffeWetlands, both natural and designed, can be a cost-effective tool for the remediation of groundwater contaminated with volatile organic compounds (VOCs) that discharge into these wetlands. The widespread use of wetlands for remediation has been hindered by uncertainties surrounding the rates and time scales of remediation mechanisms. Volatilization is perhaps the least understood of these removal mechanisms. Initial laboratory and modeling results suggest that volatilization represents a major removal pathway, with the strength and mechanism of volatilization highly dependent on the physiochemical properties of the target compound. Our understanding of the physiochemical drivers of volatilization pathways and rates remain incomplete, however, precluding any predictive modeling techniques to accurately estimate VOC fluxes from wetlands. Questions of fundamental importance to the transport of volatile compounds in saturated shallow, vegetated soils must be addressed in order to close this knowledge gap: What is the balance between gas-phase and transpiration-driven transport of VOCs through wetland plants? To what extent will plant-mediated volatilization vary as a function of vegetation type? How can plant uptake of volatile organic compounds be described appropriately with predictive models, and how can these models be validated in the field? To what extent do volatile compounds partition into subsurface bubbles, how does bubble ebullition contribute to atmospheric fluxes of VOCs, and what is the interplay between bubble dynamics and plant enhanced gas transfer? The PI will perform a comprehensive study into the fundamental dynamics of volatilization through emergent wetland plants. Measurements that will span multiple scales from single stems in controlled experiments to a field pilot study will be carried out. The experimental program will include: (1) systematic laboratory hydroponic studies using multiple volatile tracers and single stems to probe the fundamental relationships between the physiochemical properties of a compound and the rates and mechanisms for its volatilization; (2) greenhouse mesocosm studies to validate predictive models for phytovolatilization in saturated soil conditions and examine interspecies variability in contaminant removal rates; and (3) a pilot field test in a freshwater wetland to quantify spatial and temporal heterogeneities in rates of VOC removal from wetland systems. An important objective of this research is the development of a single-well ?push-pull? technique that will be developed in greenhouse mesocosms and implemented in the field, providing a novel and valuable tool for the assessment of volatilization rates in diverse wetland ecosystems where other mechanisms to determine gas exchange between the rhizosphere of wetland systems and the atmosphere are not feasible. In terms of the broader impacts, the proposed research will address fundamental questions concerning transport of chemicals in saturated soils and in vegetation that have implications across the earth sciences. Proposed technological innovations in measuring groundwater-atmosphere gas exchange will have multidisciplinary applications including the design and management of wetlands and assessment of attenuation in natural wetlands. This work will fund one Ph.D. student and contribute to the education of other graduate students in the PI?s laboratory and laboratories of outside collaborators, including Rutgers University and the Meadowlands Research Institute. Undergraduate students from different schools will be involved via an ongoing REU program. This REU program has been successful in recruiting minority and female students. Undergraduates will be involved via Senior Thesis Research. Outreach to the community is planned via participation in QUEST, a science institute for upper elementary school teachers taught by Princeton University faculty and staff, as well as by participation with the educational programs of the Stony Brook-Millstone Watershed Association, which also engages in active dialogue with municipal officials, citizens, and businesses concerning decisions that affect the local environment. Results of this research will be incorporated in undergraduate (Environmental Engineering Laboratory) and graduate (Water Quality Modeling) courses, and will be disseminated to the scientific community via presentations at National Conferences and peer-reviewed journal publications.