By measuring vertical fluxes of carbon monoxide (CO), the amount of air pollutants that originate from local versus transported anthropogenic and biogenic sources can be traced. This study focused on improving the sensitivity of a commonly used instrument that utilizes fluorescence properties of ... Show moreBy measuring vertical fluxes of carbon monoxide (CO), the amount of air pollutants that originate from local versus transported anthropogenic and biogenic sources can be traced. This study focused on improving the sensitivity of a commonly used instrument that utilizes fluorescence properties of CO molecules in the VUV range to measure atmospheric CO mixing ratios and then determine vertical fluxes of CO. To improve its performance, the instrument’s flow cell was modified and applied with a highly absorptive CuO coating. After coating of the flow cell, measurements of CO mixing ratios at dew points of 5°C, 10°C, and 15°C were made with the modified instrument and compared to measurements made with the original instrument. Measurements at different dew points were made in order to check the effect of water interference on the instrument. Comparative evaluations of the different configurations of the instrument were based on its sensitivity to CO and signal-to-noise ratio. The sensitivity to CO of the modified instrument was determined to be about two times higher than the sensitivity to CO of the original instrument. However, large numbers of noise photons caused the signal to noise ratio of the modified instrument to be significantly lower than the signal to noise ratio of the original instrument. To decrease the number of noise photons, future work will be completed in which another layer of CuO coating will be applied to better absorb VUV light. Show less
