Optical Measurements of Atmospheric Aerosols: Aeolian Dust, Secondary Organic Aerosols, and Laser-Induced Incandescence of Soot by Lulu Ma, B. S. A Dissertation In Chemistry Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of Doctor of philosophy Approved Jonathan E. Thompson Chair of Committee Dimitri Pappas Carol L. Korzeniewski Dominick Casadonte Interim Dean of the Graduate School August, 2013 Copyright 2013, Lulu Ma Texas Tech University, Lulu Ma, August 2013 ACKNOWLEDGMENTS I would like to thank my advisor, Dr. Thompson for his guidance and encouragement throughout the past 4 years in Texas Tech University. His profound knowledge, diligence and patience encouraged me and has setup a great example for me in the future. I also thank to Dr. Pappas and Dr. Korzeniewski for their help and for taking time as my committee members. I also would like to thank Dr. Ted Zobeck for his help on soil dust measurements and soil sample collection and also Dr. P. Buseck and his lab for TEM analysis. My group members: Hao Tang, Fang Qian, Kathy Dial, Haley Redmond, Yiyi Wei, Tingting Cao, and Qing Zhang, also helped me a lot in both daily life, and research. At last, I would like to thank my parents and friends for their love and continuous encouragement and support. ii Texas Tech University, Lulu Ma, August 2013 TABLE OF CONTENTS ACKNOWLEDGMENTS……………………………………………………………….ii ABSTRACT ……………………………………………………………………………..vi LIST OF TABLES …………………………………………………………………….viii LIST OF FIGURES……………………………………………………..………………ix LIST OF ABBREVIATIONS ………………………………………….………………xi I. INTRODUCTION ......................................................................................................... 1 1.1 Introduction to Atmospheric Aerosols. ................................................................... 1 1.1.1 Natural Sources .............................................................................................. 1 1.1.2 Anthropogenic Sources .................................................................................. 2 1.1.3 Production of Atmospheric Aerosols ............................................................. 2 1.2 Effects of Atmospheric Aerosols ............................................................................ 3 1.2.1 Climate Effects............................................................................................... 3 1.2.2 Health effects ................................................................................................. 5 1.3 Optical properties of Atmospheric Aerosols........................................................... 6 1.3.1 Possible Phenomena of Light Incidence on Aerosols .................................... 6 1.3.2 Extinction, Scattering and Absorption ........................................................... 7 1.4 Optical Measurement of Aerosols .......................................................................... 8 1.4.1 Cavity Ring-down Spectroscopy (CRDS) ..................................................... 8 1.4.2 Nephelometer ................................................................................................. 9 1.4.3 Particle Soot Absorption Photometer (PSAP) ............................................. 10 II. OPTICAL PROPERTIES OF AEOLIAN DUSTS COMMON TO WEST TEXAS ........................................................................................................................................... 17 2.1 Introduction ........................................................................................................... 17 2.2 Experimental ......................................................................................................... 19 2.2.1. Dentition of Fundamental Optical Parameters ............................................ 19 2.2.2 Soil Types, Sampling Locations, and Physical Properties ........................... 19 2.2.3 Soil Textures ................................................................................................ 20 2.2.4 Organic Matter Content and Particle Density of Soil .................................. 20 2.2.5. Generation of Soil Dust .............................................................................. 21 2.2.6. Measurement Instruments ........................................................................... 21 2.3. Results and Discussion ........................................................................................ 22 2.3.1 Observed Particle Size Distributions for Pullman and Amarillo Soils ........ 22 iii Texas Tech University, Lulu Ma, August 2013 2.3.2 Dust Optical Properties: the Spectral Dependence of Dust Extinction and Absorption............................................................................................................. 23 2.3.3 Angstrom Extinction Exponent (AEE) ........................................................ 23 2.3.4 Angstrom Absorption Exponent (AAE) and Diffuse Reflectance ............... 24 2.3.5 Estimate of Single Scatter Albedo (SSA) of Pullman and Amarillo Soil Dust Aerosols ................................................................................................................ 26 2.3.6 Mass-Extinction Coefficient (MEC) of Pullman and Amarillo Soils .......... 26 2.4 Summary and conclusions .................................................................................... 27 III. OPTICAL PROPERTIES OF DISPERSED AEROSOLS IN THE NEAR ULTRAVIOLET (355NM): MEASURMENT, APPROACH AND INITIAL DATA 35 3.1 Introduction ........................................................................................................... 35 3.2 Experimental Methods .......................................................................................... 37 3.2.1 Sample Flow Path ........................................................................................ 37 3.2.2 Generation of Aerosol Particles. .................................................................. 37 3.2.3 Optical measurements. ................................................................................. 39 3.3 Results and discussion .......................................................................................... 40 3.3.1 Calibration Gas Experiments ....................................................................... 40 3.3.2 Size-Selected Ammonium Sulfate Aerosols and Secondary Organic Aerosol (SOA). ................................................................................................................... 41 3.3.3 Soil Dusts and Biomass Burning Aerosols .................................................. 42 3.3.4 Ambient Measurements ............................................................................... 43 3.4 Conclusions ........................................................................................................... 46 IV. LIGHT SCATTERING AND EXTINCTION MEASUREMENTS CCOMBINED WITH LASER-INDUCED INCANDESCENCE WITHIN AN AEROSOL ALBEDOMETER: METHOD DEVELOPMENT AND EFFECT OF SOOT MORPHOLOGICAL CHANGES ................................................................................. 56 4.1 Introduction. .......................................................................................................... 56 4.2 Methods................................................................................................................. 57 4.2.1 Generation and Characteristics of Kerosene Soot ....................................... 57 4.2.2 Description of the Optical Measurements.................................................... 58 4.2.3 Scanning Mobility Particle Sizing (SMPS) and Particle Soot Absorption Photometry (PSAP) ............................................................................................... 59 4.2.4 Discrete Dipole Approximation (DDA) Modeling ...................................... 60 4.2.5 Transmission Electron Microscopy (TEM) Analysis .................................. 60 4.3 RESULTS & DISCUSSION................................................................................. 60 4.3.1 Strategies to Measure the LII Signal ............................................................ 60 4.3.2 Consequences of the LII Measurement: Soot Morphology Changes .......... 64 4.3.3 Suggested Measurement Sequence. ............................................................. 65 iv Texas Tech University, Lulu Ma, August 2013 V. CONCLUSION AND DISCUSSION ........................................................................ 76 APPENDIX ...................................................................................................................... 79 A. OPERATING PROCEDURE FOR USING THE ADDA DISCRETE DIPOLE SOFTWARE FOR MODELING LIGHT SCATTERING AND ABSORPTION BY SMALL IRREGULAR PARTICLES. .......................................................................... 79 REFERENCES ................................................................................................................ 98 v Texas Tech University, Lulu Ma, August 2013 ABSTRACT Aerosols suspended in earth’s atmosphere absorb and scatter sunlight. These optical effects can alter photochemistry or warm or cool the atmosphere and affect climate. This dissertation research contributes to a broader understanding of how aerosols affect our climate system by presenting advances in measurement devices used for optical measurements of aerosols. In addition, the dissertation provides salient optical property data for several aerosol types including Aeolian dusts, ammonium sulfate, secondary