A Comparison Between Ground And Air Sampling

A Comparison Between Ground and Air Sampling

Jennifer DeHart SARP 2009 Presentation

Overview Introduction Background

◦ Where/how the samples were collected Methodology

◦ Comparing the three datasets ◦ Coefficient of Variation Results Conclusion Acknowledgements

Introduction Airborne

sample collection

◦ 1000 feet and below Ground

grid study Comparison between data ◦ Confirmation

Background  There

were three separate sample collections ◦ A first flight on July 22nd ◦ A second flight on July 24th  Grid was predetermined by ◦ Ground sampling done

Melissa Yang, Ph.D. o o o

Roughly 25 miles between centers of each box Designed to match up with previous grid studies All samples taken away from possible sources (roads, tractors, etc.)

Background

Methodology  Samples

were analyzed in the Rowland/Blake Lab using gas chromotography  Two systems were utilized: the “big system” and the methane system

Methodology Data

filtered

◦ 1500 feet ◦ Data was included where the three sampling campaigns overlapped Introduction of error

◦ Data from the dairy and vineyard were discarded

Actual Data Used

All data collected during SARP 2009

Methodology Correlation

◦ ◦ ◦ ◦

Average concentrations Coefficient was too high Dominating concentrations Needed a different way to look at how the data varied

Methodology Made

the decision to compare the concentrations separately ◦ Calculated standard deviations from average concentrations ◦ Standard deviation inaccurate ◦ Used the coefficient of variation instead

Results: Coefficients of Variation

All Data sets

Flight 2

CCl4 Conc.

Flight 1

Grid

All Data sets

Flight 2

Propene Conc.

Flight 1

Grid

Results Of

all the gases, 9 have a coefficient of variation greater than .4 Shorter lifetimes Seinfeld, John. "Global Atmospheric Chemistry of Reactive Hydrocarbons." Reactive hydrocarbons in the atmosphere. Ed. C. N.

Conclusions  Overall,

the data correlated well between the two flights and the grid  There were a few gases that varied greatly, but those that are important to the research of the Rowland/Blake lab were generally very consistent  Much of the variation between the data was due to short atmospheric lifetimes  It is important when designing a grid study to be aware of the goal of the study ◦ Stay away from potential sources that might contaminate the data  Sampling

on science flights should still be

Further Work Attempt

to compare datasets that overlay better (though this is difficult when dealing with airplanes) Do a comparison between datasets that is more specific geographically or temporally

Acknowledgements Sherwood

Rowland, Ph.D. Donald Blake, Ph.D. Melissa Yang, Ph.D. NSERC Rowland/Blake Research Group SARP Christina McCluskey for her photos—Team PINK!!!

Questions? Thank

you!