John Birks

Understanding nitrogen oxides (NO = NO + NO) measurement techniques is important as air-quality standards become more stringent, important sources change, and instrumentation develops. NO observations are compared in two environments: source testing from the combustion of southwestern biomass fuels and urban, ambient NO. The latter occurred in the urban core of Albuquerque, NM at an EPA NCORE site during February-March 2017, a relatively clean photochemical environment with ozone (O) < 60 ppb for all but 6 hours. We compare two techniques used to measure NO in biomass smoke during biomass burning source testing: light absorption at 405 nm and a traditional chemiluminescence monitor. Two additional oxides of nitrogen techniques were added in urban measurements: a Cavity Attenuated Phase Shift instrument for direct NO and the NO chemiluminescence instrument (conversion of NO to NO by molybdenum catalyst). We find agreement similar to laboratory standards for NO, NO and NO comparing...

A new laboratory source of gaseous hypochlorous acid (HOCl) has been used in two kinetics investigations in a mass spectrometry-resonance fluorescence discharge flow system. Two potential removal reactions of stratospheric HOCl were studied. The rate constant for the reaction OH + HOCl ..-->.. H/sub 2/O + ClO (1) at 298 K was found to be lower than the NASA estimate by a factor of about 2-12; a value in the range (1.7-9.5) x 10/sup -13/ cm/sup 3/ molecule/sup -1/ s/sup -1/ for k/sub 1/ is reported here. The reaction of Cl/sub 2/O + OH interfered in the study of k/sub 1/ and was the subject of a preliminary investigation. Its rate constant was determined to be (9.4 +/- 1.0) x 10/sup -12/ cm/sup 3/ molecule/sup -1/ s/sup -1/ at 298 K. The rate constant for the reaction H + HOCl ..-->.. products (2) was determined to be (5.0 +/- 1.4) x 298 K. Although branching ratios for three possible products channels could not be determined, OH was identified as a product. The results of this work imply that reactions 1 and 2 are not competitive with direct photolysis in the removal of HOCl from the stratosphere.

Presentation of a list of recommendations, from the CHEMRAWN (Chemical Research Applied to Worlds Needs) and concerning global change chemistry, global monitoring, education, stratospheric ozone depletion, climate change, oxidant formation and acid precipitation in the troposphere

The concentration of nitric oxide in a gas is determined by oxidizing NO to NO.sub.2 and then measuring the concentration of NO.sub.2 in the gas, which is proportional to the concentration of NO. Preferably, gaseous NO.sub.2 molecules diffuse through a plurality of capillary membrane fibers and undergo a chemiluminescent reaction with a reagent flowing within; the light from the reaction is measured to determine NO.sub.2 concentration. In another aspect of a preferred embodiment, gas is passed through a scrubber before the concentration of NO.sub.2 is measured, in order to substantially remove carbon dioxide and ambient NO.sub.2 from the gas without substantially affecting the concentration of nitric oxide therein.

The present invention provides a means of greatly reducing or eliminating the interferences of UV-absorbing compounds, mercury, water vapor and particulates in the UV absorbance measurement of ozone by replacing the internal solid-phase ozone scrubber with a gas-phase scrubber. Reagent gases well suited as a gas-phase scrubber of ozone include nitric oxide and bromine atoms. Nitric oxide may be supplied by a gas cylinder or by photolysis of either N.sub.2O or NO.sub.2, both in the absence of oxygen. Bromine atoms are conveniently generated by photolysis of Br.sub.2 supplied by a permeation tube. Bromine atoms have the advantage of having a faster reaction with ozone than NO and of being catalytic in their reaction. Nitric oxide has the advantage of being generally less reactive with other components of air.

This Curriculum for the Global Ozone Project teaches fundamentals of air pollution, ground level ozone formation, and stratospheric ozone depletion at the middle and high school levels. Students in the GO3 Project measure air pollutants outside their schools and upload their data to the GO3 Database for online graphing and display on Google Earth. Students interact on a Social Network where they write environmental blogs, participate in forums and share photos and art work.

The present invention provides a means of producing nitric oxide (NO) by photolysis of nitrous oxide (N2O) at ultraviolet wavelengths. One application is the production of a known concentration of NO in a diluent gas for calibration of analytical instruments that measure nitric oxide in gases such as exhaled breath, ambient air and automobile exhaust. A potentially important medical application is the production of NO for inhalation therapy, an advantage being that very little toxic NO2 gas is produced. The method is useful for producing NO for industrial applications as well. Advantages of this method of NO production include the use of a single, inexpensive, readily available reagent gas of very low toxicity. Furthermore, the concentration of NO produced can be easily controlled by varying the ultraviolet (UV) lamp intensity and relative gas flow rates. The method may also be applied to the production of controlled concentrations of other gases as well such as CO and F2 by using r...

Carbon dioxide is the most important greenhouse gas other than water vapor, and its modulation by the biosphere is of fundamental importance to our understanding of global climate change. We have developed a new technique for vertical profiling of CO2 and meteorological parameters through the atmospheric boundary layer and well into the free troposphere. Vertical profiling of CO2 mixing ratios allows estimates of landscape-scale fluxes characteristic of approximately100 km2 of an ecosystem. The method makes use of a powered parachute as a platform and a new Tedlar bag air sampling technique. Air samples are returned to the ground where measurements of CO2 mixing ratios are made with high precision (< or =0.1%) and accuracy (< or =0.1%) using a conventional nondispersive infrared analyzer. Laboratory studies are described that characterize the accuracy and precision of the bag sampling technique and that measure the diffusion coefficient of CO2 through the Tedlar bag wall. The technique has been applied in field studies in the proximity of two AmeriFlux sites, and results are compared with tower measurements of CO2.

Solid adsorbents have proven useful for determining the vertical profiles of volatile organic compounds (VOCs) using sampling platforms such as balloons, kites, and light aircraft, and those profiles provide valuable information about the sources, sinks, transformations, and transport of atmospheric VOCs. One of the largest contributions to error in VOC concentrations is the estimation of the volume of air sampled on the adsorbent cartridge. These errors arise from different sources, such as variations in pumping flow rates from changes in ambient temperature and pressure with altitude, and decrease in the sampling pump battery power. Another significant source for sampling rate variations are differences in the flow resistance of individual sampling cartridges. To improve the accuracy and precision of VOC measurements, the use of ambient chlorofluorocarbons (CFCs) as internal standards was investigated. A multibed solid adsorbent, AirToxic (Supelco), was chosen for its wide sampling range (C3-C12). Analysis was accomplished by thermal desorption and dual detection GC/FID/ECD, resulting in sensitive and selective detection of both VOCs and CFCs in the same sample. Long-lived chlorinated compounds (CFC-11, CFC-12, CFC-113, CCl4 and CH3CCl3) banned by the Montreal Protocol and subsequent amendments were studied for their ability to predict sample volumes using both ground-based and vertical profiling platforms through the boundary layer and free troposphere. Of these compounds, CFC-113 and CCl4 were found to yield the greatest accuracy and precision for sampling volume determination. Use of ambient CFC-113 and CCl4 as internal standards resulted in accuracy and precision of generally better than 10% for the prediction of sample volumes in ground-, balloon-, and aircraft-based measurements. Consequently, use of CFCs as reference compounds can yield a significant improvement of accuracy and precision for ambient VOC measurements in situations where accurate flow control is troublesome.