Site-Specific Nitrous Oxide Isotope Analyzer for Measuring Bioremediation
DOE is responsible for the remediation of 1.7 trillion gallons of contaminated ground water and 40 million cubic meters of contaminated soil generated at over 7000 sites from past weapons activities. This remediation includes bioremediation, where substances are injected into the subsurface to enhance microbial decomposition. Several methods have been utilized by researchers to quantify bioremediation rates; however, these techniques require extensive sample preparation, making them unsuitable for field deployment. Improved methods are required to quantify bioremediation rates and bacterial activity. Recent studies have shown that denitrifying bacteria produce N2O with a distinct isotope ratio (15N/14N, 18O/16O, and site-specific ratios). By measuring the isotope ratio of N2O extracted from the soil, researchers can obtain a measure of bacterial activity and bioremediation rates. However, current technology involves extensive sampling and isotope ratio mass spectrometery. In this program, LGR proposes to develop a field-deployable analyzer for the accurate determination of N2O isotopes. In Phase I, LGR demonstrated technical feasibility by fabricating a prototype for quantification of [N2O], 15N, 15N15Nand 18O with a precision of 0.05 ppb, 0.4 , 0.45 , 0.6 , and 1.2 respectively. Measurements of calibrated standards demonstrated that the sensor was accurate to 1 ppb and 1 for N2O concentration and isotope ratios respectively with a linear response over a wide dynamic range of [N2O] = 150 10000 ppb. The instrument was deployed with Professor von Fischer (Colorado State University) with 15N-labelling experiments to identify nitrification and denitrification pathways in soil samples obtained from NSF LTER sites. In Phase II, LGR will develop an improved sensor for the isotope determination of ambient N2O emitted from soils and groundwater. The sensor will include provisions for batch gas sampling, chamber measurements, and periodic calibration. LGR will work with the IAEA (at no cost to this program) to compare the system to an established isotope measurement laboratory. Subsequently, the instrument will be deployed for field soil studies with Professor von Fischer. A second instrument will be deployed at the DOE IFRC site in ORNL for long-term, continuous monitoring of bacterial denitrification in soils. LGR will also extend the instrument to measure 17O in concentrated N2O samples. A Phase II funding commitment will be used to utilize the SBIR instrument to make isotope measurements of N2O obtained from bacterial digestion of dissolved nitrates for water pollution attribution. Commercial Applications and Other Benefits: During Phase III, LGR will sell the N2O isotope analyzers to isotope measurement laboratories, environmental research groups, global monitoring stations, and water quality management agencies. A market analysis suggests a 5-year commercial revenue exceeding $40M for these four markets alone.
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