Field Deployable In Situ Excitation Emission Matrix Spectroscopy System for Subsurface Monitoring

Anthropogenic influences and natural processes can have long lasting effects on the health of the subsurface environment. Subsurface water is heavily affected by changes in the environment and its quality is regarded as a powerful metric for evaluating the health of the subsurface environment. Therefore, constant monitoring of groundwater quality to identify influences over the seasonal hydrologic cycle, can be a reliable means for ensuring a secure and safe environment. Detrimental influences may include the discharge of toxic chemicals from industry, nitrate and pesticide contamination, nutrient depletion and atmospheric transport of pollutants into the subsurface. In addition, for water safety purposes, the monitoring of groundwater contaminants is of great importance. Most of the methods used to monitor groundwater quality require manual sample collection, laboratory based metrology systems and skilled personnel. These factors make groundwater monitoring expensive to perform and delay the response time in the case of a major contamination events. Thus, there is an urgent need for a field deployable, self- powered continuous detection system that can provide laboratory-scale characterization on the field without the need of constant human oversight. In this project an integrated monitoring system will be developed for characterizing groundwater quality, allowing installation and autonomous operation in the field for prolonged periods of time. The team will perform the necessary research to develop a prototype system using miniature monochromators, spectrometers and optical detectors operating on a power budget suitable for solar and battery power supply. The groundwater sample will be illuminated by sweeping monochromatic light and the spectral fluorescence, scattering and transmission of the sample will be measured versus the illuminating wavelength. The work will focus on implementing excitation emission matrix spectroscopy, traditional optical spectroscopy and turbidity measurement. Excitation emission matrix spectroscopy is a powerful tool for detecting and characterizing dissolved organic matter by its fluorescence response in natural water systems. The broadband spectral transmission and turbidity measurements will ensure detection of other organic and inorganic compounds and larger particles. The system will include water sampling via a commercially available groundwater sampling system, which allows the sampling of groundwater at different subsurface depths. It will also include remote installation and data collection to perform groundwater monitoring without human oversight. No similar commercial system is currently available. During Phase I the individual characterization techniques will be tested in laboratory environment and an integrated prototype system will be build. The prototype will be tested by measuring multiple groundwater samples from various locations.