The principal investigators (PIs) plan to carry out an exploratory research campaign in a mega-city environment in Tianjin, China (near Beijing). The PIs will focus on three topics: 1) accuracy and completeness of the gas phase emission inventory with an emphasis upon understanding emission sector contributions; 2) analysis of ozone indicator species, photochemical processing of volative organic compounds (VOCs) and related features of VOC/NOx (nitrogen oxide) limitations in the region; and 3) investigation of particulate emissions and aging with an emphasis upon partitioning of semi-volatile compounds (SVOC) between gas and vapor phases. The end products will be a better understanding of ozone and aerosol formation and fate within this megacity region and a better basis for placing the impact of this megacity in perspective with respect to future change in China. In the three week field program, the PIs will operate from a tall flux tower. This will involve chemical speciation of ambient VOCs and size distributions of aerosols coupled with NOy, CO, SO2, and O3 measurements and boundary layer lidar sensing. This work will be carried out in collaboration with scientists from the local Tianjin University as well as with NCAR scientists, who will be at the field site during the same time period (September 2010).
Gaining an initial understanding of atmospheric chemical cycles within this region will benefit overall understanding of megacity impacts on regional and global chemistry and thus benefit societal decisions regarding global change. The work will also target undergraduate and graduate student education through the PIs' NSF REU atmospheric chemistry program and a new and novel Atmospheric Policy Trajectory (APT) program.
". Our goals in the project were to characterize in detail the urban emissions from a Chinese megacity and to compare these results to available emission estimates and to the emissions fluxes from Mexico City and from other non-Chinese megacities. Our approach for this was to conduct eddy covariance flux measurements using a suite of advanced atmospheric trace gas and aerosol instrumentation using a tall meteorological tower located in urban Tianjin. Unfortunately, in July 2010 we received word from our Chinese collaborators that the project could not take place in Tianjin as originally planned due to concerns raised by the Chinese Meteorological Bureau applying to all foreign scientific field programs, circumstances entirely outside of our control. As an alternative, we identified a new group of Chinese collaborators led by Dr. Junji Cao of the Institute for Earth Environment of the Chinese Academy of Sciences (IEECAS) in Xi’an. Despite these significant mid-project changes to our plan, our chief goal for the project was still to attain a detailed characterization of the primary emissions of major pollutants and greenhouse gases from a major Chinese city. The major data collection effort for the project occurred in Xi’an during August 2011. For the experiment, a ~25 m tower was erected atop a 20-story building on the campus Xi’an Jiaotong University. A full suite of research instrumentation was deployed from Washington State University to measure meteorological conditions and concentrations of several trace pollutants and greenhouse gases. Pollutants and greenhouse gases measured included carbon dioxide, methane, carbon monoxide, ozone, NOx and VOCs, and particles. The project was a success. We have good quality data set to assess the daily concentration patterns for the pollutants monitored. For several gases, including carbon dioxide, methane, and carbon monoxide, the data sets are of high enough quality to calculate emissions at the neighborhood scale. While all findings should be considered preliminary pending peer-review and publication, we found several significant results when analyzing our Xi'an data set. With respect to the greenhouse gases, our most notable findings were: 1) how strongly the vegetation in the immediate vicinity of the flux tower affected the carbon dioxide concentrations and emissions; and 2) the relatively large magnitude of the methane fluxes, likely due to the extensive use of compressed natural gas in the city’s vehicle fleet. Although the project term is complete, we are continuing work on this data set to complete our analysis and disseminate the results to the community. We have already made three presentation based on the data- at the Planet Under Pressure Conference in March 2012, at the AOGS-AGU Joint Assembly in August 2012, and at the IGAC Conference in Beijing in September 2012. Two additional presentations are planned for the AGU Fall Meeting in December 2012. We are preparing two manuscripts for publication based on the study results. In addition to the project's science outcomes, there have also been significant broader impacts associated with the work. Four graduate students have been significantly involved in this project, and the work has been or will be included in the dissertations of two of them. Two of these graduate students were from underrepresented groups. Three participants in an NSF-sponsored REU program have also conducted research projects related to this project's activities. The opportunity to conduct research in China has been a exciting and all of the project participants have had enthusiastic conversations about our study with university colleagues and members of the community. Through these conversations we have been able to educate the public about the nature and importance not only of this work, but also of our broader research programs. The work also provided great opportunities to interact with Chinese researchers with a broad range of research interests and professional experience, to our mutual benefit. A chief outreach activity from this project was to provide informal training to our collaborators on our measurement approaches, and especially to demonstrate the value of open collaboration in environmental science. This occurred frequently during the field study, and has continued in the last year as well.
