Nitrate (NO3-) contamination in water is a worldwide environmental problem. High nitrate levels can result in adverse human health effects and eutrophication of lakes, rivers, oceans, and terrestrial ecosystems. There are several sources of nitrates, including manure, fertilizers, sewage, industrial wastewater, soil runoff, and atmospheric deposition. In order to effectively manage nitrate pollution in water, it is important to discern these contamination sources. By measuring the isotope ratios of nitrates, researchers can better determine the source of nitrate pollution and more effectively manage these sources to limit water contamination. Despite the high value of measuring nitrate isotope ratios for pollution sourcing and management, its application has been limited by difficulties associated with precisely measuring the isotope ratios. Current technology relies require extensive sample conditioning, high-vacuum, a dedicated operator, and consumable chemicals. The resulting system is difficult to operate, prone to failure, costly, and slow. The proposed SBIR analyzer will replace this conventional technology. It will be comparably accurate, significantly faster, more economical, and substantially more robust. Moreover, the unit will not require a dedicated, highly-skilled operator, thus enabling its use in a much wider range of applications (e.g. routine water quality monitoring, atmospheric monitoring stations, and environmental research laboratories). OBJECTIVES: Nitrate (NO3-) contamination in water is a worldwide environmental problem. High nitrate levels can result in adverse human health effects (e.g. methemoglobinemia and possibly stomach or gastrointestinal cancer) and eutrophication of lakes, rivers, oceans, and terrestrial ecosystems. This eutrophication leads to an increase in primary production, possibly causing decreased biodiversity, changes in species composition and dominance, and animal mortality (e.g. through a decrease in dissolved oxygen or algal blooms). Due to these issues, environmental regulations agencies have regulated nitrate levels in drinking water to ~ 10 mg NO3- - N L-1. There are several biogenic and anthropogenic sources of nitrates, including animal manure, fertilizers, sewage, industrial wastewater, soil nitrogen runoff, and atmospheric deposition. In order to effectively manage nitrate pollution in water, it is critically important to discern and identify contamination sources. Such source apportionment is complicated by the myriad of chemical and microbiological processes that produce and consume nitrates. In this Small Business Innovative Research (SBIR) effort, Los Gatos Research (LGR) proposes to utilize its patented Off-Axis ICOS technology to develop an analyzer for the accurate determination of 15N/14N and 18O/16O isotope ratios in nitrates (del 15N and del 18O). The system will employ the bacterial denitrification method to convert NO3- into N2O, and then utilize a mid-infrared Off-Axis ICOS analyzer to rapidly (< 5 minutes) determine nitrate concentration, del 15N, and del 18O to better than 1 per mil, 0.2 per mil, and 0.5 per mil respectively. Nitrate contamination in water is an ubiquitous, world-wide problem, and the resulting instrument will help provide nitrate source apportionment, identify multiple nitrate sources, study spatial mixing of nitrate pollution, and identify areas in which natural nitrate attenuation processes are taking place. Additionally, the SBIR analyzer can be used to help quantify the nitrate pollution and N2O emission impacts of emerging biofuels. APPROACH: In Phase I, LGR will demonstrate technical feasibility by fabricating a mid-infrared Off-Axis ICOS system for the accurate quantification of N2O, 15N14NO, 14N15NO, and N218O. Initially, the prototype will be tested on certified N2O gas cylinders of varying isotope ratios and concentrations to determine the instrument's accuracy, precision, linearity, dynamic range, and time response. Then, working with collaborators at the University of Washington, LGR will obtain N2O gas samples generated from nitrates via the bacterial denitrification method. These samples will be analyzed by both the Phase I instrument and conventional isotope-ratio mass spectrometry to assess the prototype's accuracy for real-world nitrates. Finally, the Phase I results will be used to develop an autonomous Phase II prototype for water pollution monitoring. In Phase II, Los Gatos Research will develop a fully autonomous sensor for the isotope determination of nitrates in aqueous systems. The sensor will include provisions for bacterial denitrification, batch gas sampling, isotope quantification with periodic calibration, and data reporting. The system will be delivered to an established isotope measurement laboratory (Isolab, Department of Earth and Space Sciences, University of Washington) for a direct intercomparison with isotope ratio mass spectrometry over a wide array of nitrate samples and standards. Finally, LGR will work USDA nitrate researchers to utilize the Phase II analyzer for water quality and N2O emission studies. 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
