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Methane Cycling & Atmospheric Emission from Freshwater Ecosystems:

M ethane is an important greenhouse gas whose natural source functions are poorly constrained, in part due to the high variability of emission that is associated with ebullition from aquatic sediments. A novel automated trap design from the Hemond lab has successfully measured ebullition fluxes with 5-minute spatial resolution for periods of months, and is low in cost, enabling many units to be deployed to capture spatial variability. Bubble fluxes from a temperate lake are shown to be a large part of the total methane budget, and their timing is highly associated with atmospheric pressure fluctuations as well as water level changes. Work is ongoing to understand the sediment processes responsible for observed emission behavior. Sponsorship includes NSF.

Anthrobiogeochemical Cycling of a Indium, a Novel Industrial Metal

Indium is an example of a metal whose natural cycling is poorly understood, yet whose use in industry is rising rapidly due to its unique and valuable properties as a constituent of new electronic components, particularly photovoltaic panels and light emitting diodes. Atmospheric cycling if indium is being studied using a combination of source-based studies, atmospheric deposition studies coupled with back-trajectory analysis, and sediment core analysis and dating. Sponsorship includes NSF.

In-Situ Chemical Sensing: The NEREUS Project

NEREUS is the first field-deployable underwater cycloidal mass spectrometer, and can be deployed either from a winch or aboard an autonomous underwater vehicle (AUV). Capable of measuring all the major gases in the water column, it also measures light hydrocarbons and solvents dissolved in water, and has been used as part of our studies of methane cycling. NEREUS has been successfully operated as the payload of an Odyssey-class autonomous underwater vehicle, and a hybrid radio/acoustic network has been developed to provide chemical data from the vehicle in real time. An underwater cycloidal mass spec instrument based on the NEREUS has now been commercialized. Sponsorship has included NSF, MIT Sea Grant, BP, and SMART.

In-situ Chemical Sensing: Laser-Induced and LED-induced Fluorescence

Complementing the capabilities of mass spectrometry, several optical sensors are now being developed to provide information on low-volatility water constituents, such as heavy hydrocarbons, humic substances, and algal pigments. Both laser excitation and low-cost LED excitation are being utilized, and both wavelength-domain and time-domain data will eventually be used to increase the specificity of these techniques. These instruments are also designed with underwater deployment aboard an AUV in mind. Sponsorship by MIT Sea Grant and SMART.

In-situ Chemical Sensing: Electrochemical Analysis with Artificial Neural Net Signal Processing

Complementing both mass spectrometric and optical date, information on the ionic composition of waters is essential to scientists, managers, and industries alike. In this project, we are using standard commercially-available specific ion electrodes (ISEs) and developing signal processing methods to overcome the problems of cross-reactivities (interferences) experienced by most of these electrodes in the presence of interfering ions for which they are not specific. An instrument capable of AUV deployment is ultimately desired. Sponsorship by MIT Sea Grant.

Renewable Energy: Organic Rankine Cycle Power Generation for Remote Communities:

The Hemond Lab and a student-run nonprofit group, STG International, are developing small-scale thermal solar plants and hybrid thermal/photovoltaic power plants, suited to provide free-standing sources of power to remote communities and other users. The key issue of cost is being addressed through novel component design and through repurposing of mass-produced fluid machinery such as air conditioning compressors. A prototype unit is under construction in Lesotho, southern Africa, by STG, and other prototype and test facilities have been built at MIT and also at a site in Florida. Sponsorshop includes the EPA P3 program, NCIIA, and the MIT Energy Initiative.

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