2014 Progress Report: Assessing The Synergistic Impact Of Anthropogenic And Biogenic Emissions On Air Pollution Using Novel High-Sensitivity, Real-Time Monitors For Fundamental CarbonylsEPA Grant Number: R835138
Title: Assessing The Synergistic Impact Of Anthropogenic And Biogenic Emissions On Air Pollution Using Novel High-Sensitivity, Real-Time Monitors For Fundamental Carbonyls
Investigators: Keutsch, Frank N
Institution: University of Wisconsin - Madison
EPA Project Officer: Hunt, Sherri
Project Period: February 1, 2012 through January 31, 2015 (Extended to January 31, 2016)
Project Period Covered by this Report: February 1, 2014 through January 31,2015
Project Amount: $250,000
RFA: Developing the Next Generation of Air Quality Measurement Technology (2011) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
The goal of this project is to demonstrate instrumentation that will allow the use of novel high time resolution monitoring data sets as new metrics to determine the contribution of anthropogenic and biogenic emissions to ozone and organic aerosol (PM). We will demonstrate that the proposed novel instrumentation can obtain long-term, low-maintenance and accurate measurements of key carbonyl-containing compounds such as formaldehyde and glyoxal, consistent with the requirements for instrumentation employed in monitoring networks. The project will validate this approach by collecting a yearlong dataset at the Horicon National Core Monitoring Station, a rural site in Wisconsin that is part of the EPA Region 5 Ambient Monitoring Network. An objective of this work is to develop the ratio and absolute concentration of monitored glyoxal/formaldehyde as a metric of the contribution of biogenic and anthropogenic volatile organic compounds (VOCs) to atmospheric oxidation. This metric will allow distinction between the direct contribution of anthropogenic VOCs and the anthropogenic impact on biogenic VOC oxidation (resulting O3 and PM via NOx), an emerging issue in air quality control, in particular for PM. In addition, these data will be compared with WRF-CMAQ model output to evaluate and improve the representation of atmospheric oxidative chemistry in models, thereby helping to provide strategies to control air quality related to O3 and PM. The objectives of the research have not changed from the original application and there has been no change in key personnel.
In year 3 of the project, instrumentation was continued to be deployed at the Horicon site and long-term measurements were conducted. In contrast to year 2 of the project the formaldehyde system functioned well as the laser problems had been successfully addressed. The deployment obtained long-term formaldehyde datasets. Altogether nearly a year of formaldehyde measurements were obtained, a success of the proposed formaldehyde monitor at Horicon, achieving one of the major objectives of the proposed work. The glyoxal laser system continued to encounter problems. Despite extensive effort and communication with the laser company this did not allow obtaining glyoxal data at Horicon, highlighting the need for further advances in laser technology for successful use of laser-induced phosphorescence detection of glyoxal in a low cost compact monitor. The activities conducted in year 3 of the project can summarized into 3 major thrusts: (1) deployment of the formaldehyde monitor and measurements at Horicon with extensive calibrations, (2) further diagnosis of laser performance of the glyoxal laser and addressing electronics problems, and (3) the first steps of leveraging data we obtained at other campaigns to investigate the utility of the glyoxal to formaldehyde ratio as a metric of anthropogenic influence on processes controlling secondary pollutants.
(1) Continued deployment of formaldehyde monitor at Horicon: A major focus of the work conducted in year 3 was deployment of the formaldehyde monitor for long-term monitoring at the Horicon site. In coordination with site personnel we continued to coordinate space and electrical power for the formaldehyde monitor. In addition, calibration units and gas supplies were deployed. The formaldehyde monitor was installed identically to year 2 and measurements conducted June 2014 through January 2015, near continuously (see figure). Combined with the measurements during year 2 this provides an extensive and novel set of high temporal resolution, high sensitivity formaldehyde measurements. This clearly demonstrates the suitability of the monitor as a novel means for unprecedented long-term monitoring of formaldehyde. We are continuing to work up the extensive data, but our initial results clearly demonstrate the importance of our new fast formaldehyde monitor: Slower measurements would have averaged over the often rapid changes in formaldehyde that we observed. As chemical processes are not linear this can result in biases. Overall, this aspect of the proposal work was highly successful and fully achieved this aspect of the proposal goals: Long-term monitoring of formaldehyde with the novel monitor at Horicon providing high time-resolution, high sensitivity data.
The figure shows a 5-day period of formaldehyde measurements obtained at Horicon in June of 2014. Red dots, blue circles, and black crosses correspond to 1 second, five minute and 1 hour averages. The left hand figure shows short-time periods with highly elevated formaldehyde and the right hand figure is a close-up excluding thee periods. Although generally a diurnal cycle with higher concentrations during the daytime is observed, there is significant variability (e.g., day 170 corresponding to unusually low formaldehyde concentrations and clean conditions).
(2) Further diagnosis of laser performance of laser in glyoxal monitor: Troubleshooting of the glyoxal laser continued with considerable time investment. The laser was re-installed in the glyoxal instrument in the laboratory. However, testing highlighted continuing problems with the laser, as it did not meet the specifications provided by the company. Unfortunately, further extended discussions with the company revealed that the system was not viable. We discussed the electronics problem with additional experts and were unable to find a solution. Fundamentally, the laser was not able to achieve a fast enough fall time. We purchased an acousto-optical modulator in order to achieve a fast switching-off time (sub-ms) external to the laser, i.e., not with the laser-driver electronics, but were not able to successfully integrate this with the laser. Our conclusion, especially given the extensive effort we invested, is that until more robust and better designed lasers are available for this monitor the traditional, expensive, large and high-power consumption Ti:Sapphire laser systems are the only ones that can make glyoxal measurements via laser-induced phosphorescence available. However, this limits how easy it is to deploy and also results in a high cost instrument, as the laser system is very high cost. The instrument also has a more than order of magnitude higher power consumption, and takes up about 5 times the amount of space. Nonetheless, to address the additional objectives of the proposal and broader scientific questions surrounding the use of the glyoxal to formaldehyde ratio, we started evaluation of glyoxal data obtained with our Ti:Sapphire laser glyoxal monitor from numerous other sites in combination with formaldehyde data obtained by an analogous instrument to the one successfully deployed at Horicon (see next point).
(3) Leveraging of glyoxal and formaldehyde data obtained at other sites to investigate the use of the ratio of glyoxal to formaldehyde as indicator of the synergistic impacts of anthropogenic and biogenic emissions on secondary pollutant formation:
At the end of the year 3 period, we started taking advantage of glyoxal and formaldehyde data obtained at numerous other sites with costly large glyoxal monitors and a formaldehyde monitor analogous to the one deployed at Horicon. During the final part of year 3, we started assembling these data sets and analyzed them with respect to time periods for which high quality formaldehyde and glyoxal measurements were available. The results will be included in the final report.
The no-cost extension period will be used to work up the long-term formaldehyde data set and analyze the glyoxal and formaldehyde data obtained from numerous locations within the context of point (3) above.