Volatilization dynamics in wetland systems

湿地系统的挥发动力学

• 批准号: 1133281
• 负责人: Peter Jaffe
• 金额: $ 31.04万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1133281&HistoricalAwards=false
• 关键词: Volatilization; dynamics; wetland; systems

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.

1133281 Pi Jaffe天然和设计的湿地可以作为一种具有成本效益的工具来修复被排放到这些湿地的挥发性有机化合物(VOCs)污染的地下水。湿地用于补救的广泛使用受到围绕补救机制的速度和时间尺度的不确定性的阻碍。在这些去除机制中，挥发可能是最不被了解的。初步的实验室和模拟结果表明，挥发是主要的去除途径，挥发的强度和机理高度依赖于目标化合物的物理化学性质。然而，我们对挥发途径和挥发速率的物理化学驱动因素的了解仍然不完整，这排除了任何预测建模技术来准确估计湿地VOC通量的可能性。为了缩小这一认识差距，必须解决对饱和浅层植被土壤中挥发性化合物运输至关重要的问题：通过湿地植物对挥发性有机化合物的气相运输和蒸腾驱动的运输之间的平衡是什么？植物介导的挥发会在多大程度上随植被类型的不同而变化？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，以及这些模型如何在田间得到验证？挥发性化合物在多大程度上被划分为地下气泡，气泡沸腾如何促进大气中VOCs的通量，以及气泡动力学和植物增强的气体传输之间的相互作用是什么？该项目将对湿地植物挥发的基本动力学进行全面研究。将进行跨越多个尺度的测量，从受控实验中的单个茎到现场先导研究。该实验计划将包括：(1)使用多种挥发性示踪剂和单茎进行系统的水培研究，以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)温室中隔研究，以验证饱和土壤条件下植物挥发的预测模型，并检查污染物去除速率的物种间变异性；(3)在淡水湿地进行试点田间试验，以量化湿地系统中VOC去除速率的空间和时间异质性。本研究的一个重要目标是研制单井推拉？这项技术将在温室生态系统中开发并在实地实施，为评估不同湿地生态系统中的挥发率提供了一种新的有价值的工具，在这些系统中，确定湿地系统根际与大气之间气体交换的其他机制是不可行的。就更广泛的影响而言，拟议的研究将解决与化学品在饱和土壤和植被中的运输有关的基本问题，这些问题涉及到整个地球科学。在测量地下水-大气气体交换方面拟议的技术创新将具有多学科的应用，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，并为皮埃尔？S实验室和外部合作者的实验室(包括罗格斯大学和梅多兰兹研究所)的其他研究生的教育做出贡献。来自不同学校的本科生将通过正在进行的REU计划参与进来。该REU项目在招收少数民族和女性学生方面取得了成功。本科生将通过高级论文研究参与其中。计划通过参与Quest，一个由普林斯顿大学教职员工讲授的小学高年级教师科学研究所，以及参与石溪-米尔斯通流域协会的教育项目，向社区进行宣传，该协会还就影响当地环境的决策与市政官员、市民和企业进行积极对话。这项研究的成果将被纳入本科生(环境工程实验室)和研究生(水质模型)课程，并将通过在全国会议上的演讲和同行评议的期刊出版物向科学界传播。