A number of MIR sensing platforms and methods were developed in this research work demonstrating potential applicability of MIR spectroscopy for studying hydrocarbon systems in extreme environments. First of all, the quantitative determination of the diamondoid compound adamantane in organic media utilizing IR-ATR spectroscopy at waveguide surfaces was established. The developed analytical strategy further enabled the successful detection of adamantane in real world crude oil samples. These reported efforts provide a promising outlook for detection and monitoring of diamondoid constituents in naturally occurring crudes and petroleum samples. IR-ATR spectroscopy was further utilized for evaluating and characterizing distribution, variations, and origin of carbonate minerals within sediment formations surrounding a hydrocarbon seep site - MC 118 in the Gulf of Mexico. An analytical model for direct detection of 13C-depleted authigenic carbonates associated with cold seep ecosystems was constructed. Potential applicability of IR-ATR spectroscopy as direct on-ship - and in future in situ - analytical tool for characterizing hydrocarbon seep sites was demonstrated. MIR evanescent field absorption spectroscopy was also utilized to expand the understanding on the role of surfactants during gas hydrate formation at surfaces. This experimental method allowed detailed spectroscopic observations of detergent-related surface processes during SDS mediated gas hydrate formation. The obtained IR data enabled proposing a mechanism by which SDS decreases the induction time for hydrate nucleation, and promotes hydrate formation. Potential of MIR fiberoptic evanescent field spectroscopy for studying surface effects during gas hydrate nucleation and growth was demonstrated. Next, quantifying trace amounts of water content in hexane using MIR evanescent field absorption spectroscopy is presented. The improvement in sensitivity and of limit of detection was obtained by coating an optical fiber with layer of a hydrophilic polymer. The application of the polymer layer has enabled the on-line MIR detection of water in hexane at low ppm levels. These results indicate that the MIR evanescent filed spectroscopy method shows potential for in-situ detection and monitoring of water in industrial oils and petroleum products. Finally, quantification of trace amounts of oil content in water using MIR evanescent field absorption spectroscopy is reported. Unmodified and modified with grafted hydrophobic polymer layer silver halide optical fibers were employed for the measurements. The surface modification of the fiber has enabled the on-line MIR analysis of crude oil in water at the low ppb level. Potential application of MIR fiber-optic evanescent field spectroscopy using polymer modified waveguides toward in-situ low level detection of crude oil in open waters was demonstrated.

Substantial amounts of methane are sequestered in naturally occurring ice-like formations known as gas hydrates. In particular, oceanic gas hydrates are globally distributed in complex heterogeneous ecosystems that typically occur at depths exceeding 300 m. Gas hydrates have received attention for their potential as an alternative energy resource, as marine geohazards, and their role in cycling of greenhouse gases. In addition, chemosynthetic communities often play a vital role in the cycling and sequestration of carbon emanating from cold hydrocarbon seeps surrounding hydrate sites. Research efforts are presently striving to better understand the significance and complexity of these ecosystems through the establishment of seafloor observatories capable of long-term monitoring with integrated sensor networks. In this thesis, infrared (IR) spectroscopy has been implemented for the investigation of molecular-specific signatures to monitor gas hydrate growth dynamics and evaluate carbonate minerals, which are intimately connected with complex chemosynthetic processes occurring in these harsh environments. The first fundamental principles and data evaluation strategies for monitoring and quantifying gas hydrate growth dynamics utilizing mid-infrared (MIR) fiber-optic evanescent field spectroscopy have been established by exploiting the state-responsive IR absorption behavior of water. This has been achieved by peak area evaluation of the O-H stretch, H-O-H bend, and libration modes and assessing peak shifts in the 3rd libration overtone and libration bands during the formation and dissociation of simple clathrate hydrates of methane, ethane, and propane formed from aqueous solution. Hydrate growth and monitoring was facilitated with a customized pressure cell enabling operation up to ~5.9 MPa with spectroscopic, temperature, pressure, and video monitoring capabilities. Furthermore, the initial feasibility for extending the developed IR spectroscopic hydrate monitoring strategies into oceanic gas hydrate ecosystems has been demonstrated through the evaluation of potential spectroscopic interferences from sediment matrices in samples collected from two hydrate sites in the Gulf of Mexico (GoM). With exception of the libration band, the primary IR absorption features of water are readily accessed within hydrated sediment samples. Additional consideration for potential long-term hydrate monitoring applications revealed that the collection of approx. 2 IR spectra per day should enable direct insight into the temporal dynamics of hydrates...