Decadal trends in atmospheric organic aerosol

83 Pages·2016·9.5 MB·English

Decadal trends in atmospheric organic aerosol:
Analysis of network data and method development
by
ARCHVES
MASSACHUSETTS INSTITUTE
Kelsey Jane Boulanger OF TECHNOLOGY
DEC 0 U 2015
B.S. Civil and Environmental Engineering
University of California, Berkeley (2012)
LIBRARIES
Submitted to the Department of Civil and Environmental Engineering
in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE IN CIVIL AND ENVIRONMENTAL ENGINEERING
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
September 2015
2015 Massachusetts Institute of Technology. All rights reserved.
Signature redacted
A uthor............................ ...........
Department of Civil 2 Environmelal Engineering
August 20, 2015
.............. Signature redacted
Certified by......................
Jesse H. Kroll
Associate Professor of Civil, Enviro ental, and Chemical Engineering
Thesis Supervisor
1/
Signature redacted
A ccepted by.......................................
I / I-i i M. Nepf
Donald and Martha Harleman Professor of Civil and Environmental engineering
Chair, Graduate Program Committee
2
Decadal trends in atmospheric organic aerosol:
Analysis of network data and method development
by
Kelsey Jane Boulanger
Submitted to the Department of Civil and Environmental Engineering
on August 20, 2015 in partial fulfillment of the
requirements for the degree of Master of Science in
Civil and Environmental Engineering
ABSTRACT
Organic aerosol (OA) makes up a substantial fraction of atmospheric particulate matter, yet its
sources and controlling factors - and thus its impacts on climate and human health - are not well
understood. Recently-developed analytical techniques have provided new insight into OA
chemistry, but major uncertainty remains in how OA has changed over the past few decades.
Characterizing long-term trends in OA would allow for better calibration of models that
currently struggle to replicate ambient organic measurements as well as answer questions of how
changes in OA relate to changes in emissions sources, anthropogenic-biogenic emissions
interactions, altered chemistry, and more. This work represents a two-fold effort to better
constrain our understanding of OA trends spatially, temporally, and chemically. First, trends in
aerosol species concentrations over the past two decades are examined using existing data from
the U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) network to
provide insight into the long-term OA evolution across the rural U.S. Along with large decreases
in total aerosol amounts (30-50%), OA is found to decrease at a fractional rate nearly equivalent
to the decreases in three other major aerosol species: nitrate, sulfate, and elemental carbon. This
suggests a link between the controlling factors of the different species, but explaining these
observations is made challenging by the lack of chemical characterization of historic OA
measurements that would help point to changing sources and chemistry. Thus, the second part of
this work introduces a technique that enhances our ability to obtain important chemical
information from small-volume environmental aerosol samples, such as filter extracts from
remote regions like those monitored by the IMPROVE network, that were previously excluded
from Aerodyne aerosol mass spectrometer (AMS) analysis due to the prohibitive volumes
required for standard atomization. The Small Volume Nebulizer (SVN) nebulizes microliter-
sized liquid samples, allowing for highly time- and mass-resolved chemical analysis of dissolved
organic species on the AMS and providing valuable insight into the factors that control observed
OA trends. By examining historic trends in particulate matter loading and composition, and
expanding AMS coverage to include small-volume environmental samples, we can begin to
answer the question of how and why OA has changed over the past few decades - and what that
means for OA chemistry, the climate, and regional and global air quality.
Thesis Supervisor: Jesse H. Kroll
Title: Associate Professor of Civil, Environmental, and Chemical Engineering
3
4
Acknowledgements
This project is based upon work supported by the National Science Foundation Graduate
Research Fellowship under Grant No. 1122374, with additional funding from the National
Oceanic and Atmospheric Administration Grant No. NA130AR4310072. For the work on the
Small Volume Nebulizer, I would like to thank our collaborators Manjula Canagaratna,J ohn
Jayne, and Phillip Croteau from Aerodyne Research Inc as well as Jason Surratt and his
research groupf or providing us withfilter extracts.
This work would be incomplete were it not for the incredible members of the Kroll research
group. Anthony Carrasquillo, Kelly Daumit, James Hunter, Eben Cross, Chris Lim, Ellie
Browne, Sean Kessler, Jon Franklin, David Hagan, Gabriel Issacman-VanWertz, and Rachel
O'Brien: thank you all for your generosity of knowledge, advice, energy, and spirit. I will
forever cherish memories of days spent in and out of lab with you all, exploring new cities for
conferences, jumping rope in 5-degree-Fahrenheit weather, consuming excessive amounts of
(non-alcoholic) butterbeer in Harry Potter World, teaching chemistry to eager high school
students, fighting (non-literal and literal) fires in lab, and passing the torch on the SVN (which
remains a boring acronym despite some of your best efforts to make it otherwise!). It's been an
amazing three years with an absolutely stellar research group. You'll all be dearly missed.
I owe my sanity to my friends and family. In addition to the extended Parsons community, who
make this building a home and who are too numerous to name but are all amazing, I want to
specifically thank Katie Dailey for our weekly Skype conversations; Andrea Gutierrez for
internet article swapping; Erin Connor and Jenn Apell for girls' nights; Amy Lu and Ana
Ebrahimi for being my pen pals; Kyle Delwiche, Joseph Abel, and Alex Konings for game
nights; and Anthony Carrasquillo for our shared (questionable) consumption of pop culture.
Many thanks to my amazing sister, Lauren, for philosophizing on our shared upbringing and
subsequent views of the world, and to my incredible mom and dad, for loving, supporting, and
cheering for me more than I can understand. And to my wonderful husband, David: marrying
you was the best thing to come out of my experience at MIT. Thank you for everything you do to
make our lives so fulfilling and enriching. (Also: official apologies to Jesse and Colette for all
the time we wasted while we fell in love instead of working!) Each and every one of these people
gave me the strength I needed to make it to MIT in the first place, to complete this degree, and to
follow my passion into teaching. I'll never be able to thank you all enough.
Most of all, I want to thank my research advisor, Jesse Kroll. Not a single graph or statement of
this thesis would have been possible without his tireless enthusiasm, generous encouragement,
and patient understanding (often undeserved). Jesse, your mentorship and inspirational
leadership are the main reasons I am sad to graduate. You are one of the kindest people I have
ever met; if I could teach while working for you forever, I would without question. I will do my
best to pay forward the grace you have shown me by extending similar compassion to all of my
future students. Thank you so much for everything.
5
6
Contents
1. Introduction .................................................................................................................................... 11
2. Evidence for Decreasing Organic Aerosol Concentrations in the Rural United States
Over the Last Q uarter-Century ............................................................................................ 19
2.1 R ationale .................................................................................................................................................... 19
2.2 M ethod ....................................................................................................................................................... 20
2.2.1 IM PROV E N etwork ........................................................................................................................................... 20
2.2.2 Data A cquisition..................................................................................................................................................23
2.2.3 D ata A nalysis........................................................................................................................................................24
2.3 R esults and D iscussion............................................................................................................................ 26
2.4 Conclusions................................................................................................................................................ 36
3. Development of a nebulization technique for obtaining AMS spectra from small
volum e liquid sam ples........................................................................................................... 39
3.1 M otivation ................................................................................................................................................. 39
3.2 M ethods...................................................................................................................................................... 40
3.2.1 Sm all Volum e N ebulizer...................................................................................................................................40
3.2.2 Standards and Sam ple Generation and Storage..................................................................................... 42
3.2.3 D ata Collection and Processing......................................................................................................................43
3.3 R esults and D iscussion............................................................................................................................ 45
3.3.1 Technique Characterization.............................................................................................................................45
3.3.2 Com parison w ith Standard Atom ization ............................................................................................... 48
3.3.3 Determ ination of the Optim al Sam ple Solvent..................................................................................... 50
3.3.4 Testing Laboratory SOA ................................................................................................................................... 52
3.4 Conclusions................................................................................................................................................ 56
4. Sum m ary ........................................................................................................................................... 59
6. A ppendix............................................................................................................................................ 69
6.1 A verage A erosol Pie Charts for Individual IM PROVE Sites ........................................................... 69
6.2 Com paring SVN Film s..........................................................................................................................................78
6.3 Com paring Extraction Solvents ......................................................................................................................... 82
7
8
List of Figures and Tables
FIGURES
Figure 1: IM PROVE Network Locations ................................................................................ 21
Figure 2: Schem atic of the Im prove Sampler ............................................................................ 23
Figure 3: Regional Average Composition and Total Loading of Particulate Matter for the United
States in 1990 and 20 10 ..................................................................................................... 33
Figure 4: Average Regional Trends in Aerosol Species Relative to their 1990 Values........... 34
Figure 5: Investigating Biomass Burning Effects..................................................................... 35
Figure 6: Investigating Weekday and Weekend Effects.......................................................... 35
Figure 7: Investigating the Relationship Between Organic Mass and Sulfate........................... 36
Figure 8: Sm all Volum e N ebulizer Set Up .............................................................................. 42
Figure 9: Filter Sam ple Extraction M ethod .............................................................................. 43
Figure 10: Comparing the Mass Observed in the AMS to both the Droplet Size and Nebulized
M a ss ...................................................................................................................................... 4 9
Figure 11: Comparing the SVN Technique to the TSI Atomizer ............................................ 47
Figure 12: Particle Size and Signal Produced for Different Solvents........................................ 51
Figure 13: Comparing Online AMS with Offline SVN Measurements for Different Solvents ... 55
Figure 14: Comparing Online ACSM with Offline SVN-AMS Measurements for an SOA
E x p erim en t............................................................................................................................ 5 6
TABLES
Table 1: Data Wizard Selections for IMPROVE Data Used in this Study ............................... 24
Table 2: Ammonium-to-Nitrate and Ammonium-to-Sulfate Ratios for the Solution, the TSI
Atomizer, and the SVN Nebulization Technique. ........................................................... 49
9
APPENDIX
Appendix 1: IMPROVE Site Abbreviations............................................................................. 69
Appendix 2: Sites Locations in the Western United States ..................................................... 70
Appendix 3: Average Aerosol Pie Charts for the Western United States.................................. 71
Appendix 4: Site Locations in the Mid-United States .............................................................. 72
Appendix 5: Average Aerosol Pie Charts for the Mid-United States........................................ 74
Appendix 6: Sites Locations in the Eastern United States........................................................ 75
Appendix 7: Average Aerosol Pie Charts for the Eastern United States................................... 76
Appendix 8: Additional IMPROVE Sites Not Included in the Three Regions ........................ 77
A ppendix 9: Polyester Film Test R esults...................................................................................... 78
Appendix 10: FEP Film Test Results ....................................................................................... 79
Appendix 11: Kapton Polimide Film Test Results ................................................................... 80
A ppendix 12: Teflon Film Test Results.................................................................................... 81
Appendix 13: Comparing Extraction Solvents .......................................................................... 83
10