Development, Characterization, and Application of a Light Scattering Module within the Aerodyne AMS

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Ambrose Lang
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1 Development, Characterization, and Application of a Light Scattering Module within the Aerodyne AMS Eben Cross th AMS User s Meeting 5 /7/5 Simple Rules to giving a Successful and Entertaining User s Meeting Presentation Maintain your composure at all times.don t chew gum.don t use your foot as a laser pointer 3.Avoid using four-letter words to describe igor plots of you data This plot is complete #!@&.Avoid using four-letter words in describing the physical geometry of your system There are some big $#! holes in the ellipsoid 5.Find some way to make fun of Doug during your talk,,3,,5.. Cross, E. AMS User s Meeting Presentation, Georgia Tech, Atlanta, GA, Oct.. Cross, E. AMS Poster Presentation, Forschungszentrum Julich, Germany Aug 5.

$Overview Review system geometry LS-AMS Capabilities Laboratory Aerosols (Sensitivity Analysis) Refractive Index Shape Ambient Aerosol Analysis$

2 Overview Review system geometry LS-AMS Capabilities Laboratory Aerosols (Sensitivity Analysis) Refractive Index Shape Ambient Aerosol Analysis with a LS-AMS Chebogue Point, Nova Scotia Schematic of the AMS with a light scattering module installed y x z ELLIPSOIDAL MIRROR BEAM STOP PMT LASER

3 LS-AMS System Capabilities. Provides an independent measure of the particle size (~ ) based on the light scattering signal intensity. Provides an in-situ measure of the effective density of the aerosol distribution 3. Provides an in-situ quantification of the refractory/particle bounce events within the AMS An independent measure of the particle size (~ ) based on the integrated light scattering signal Light Scattering Signal (bits) 3 Integrated Sig =. f(size, refractive index, shape) Integrated Light Scattering Signal Light Scattering Signal (bits) x -3 time-of-flight (s) OUTPUT = (optical) time-of-flight (s).5x -3 x 3 5 3

4 LS-AMS System Capabilities. Provides an independent measure of the particle size (~ ) based on the light scattering signal intensity. Provides an in-situ measure of the effective density of the aerosol distribution In-situ measure of the effective density Eqn. d va = * ρ * S Light Scattering Signal (bits) 3 Eqn. d va = ρ eff * d va 3 5 Time of threshold crossing determines particle velocity d va time-of-flight (s).5x -3

5 LS-AMS System Capabilities. Provides an independent measure of the particle size (~ ) based on the light scattering signal intensity. Provides an in-situ measure of the effective density of the aerosol distribution 3. Provides an in-situ quantification of the refractory/particle bounce events within the AMS In-situ quantification of the refractory and/or particle bounce events for single particles Non-Refractory Particle Event NH NO 3 5 ls_sig tof_sig 3 time-of-flight x -3 Refractory or Particle Bounce Event ls_sig (NH ) SO tof_sig 3 time-of-flight 5x -3 5

6 Point for Discussion Classification of the vacuum aerodynamic diameter based on light scattering signals Remove the uncertainty in t from the chopper Estimates of vaporization/ion flight times as correction to the light scattering signal velocity designation Overview Review system geometry LS-AMS Capabilities Laboratory Aerosols (Sensitivity Analysis) Refractive Index

7 Size detection limit ~ nm. Counting Efficiency (LS/CPC).... LS/CPC Counting Efficiency Oleic Acid. x 3 Dmobility (nm) Refractive index effect on LS-AMS sizing method: spherical particles Integrated Light Scattering Signal.. Oleic Acid n =. x 3 5 (nm) 7

8 Refractive index effect on LS-AMS sizing method: spherical particles Integrated Light Scattering Signal.. Oleic Acid n =. PSL n =.59 x 3 5 (nm) Refractive index effect on LS-AMS sizing method: spherical particles Integrated Light Scattering Signal.. Oleic Acid n =. PSL n = Fomblin n =.3 n H =.33 n ambient aerosol >/=. x 3 5 (nm)

9 Refractive index effect on LS-AMS sizing method: spherical particles Integrated Light Scattering Signal.. Oleic Acid n =. NH NO 3 n =.55 PSL n = Fomblin n =.3 n H =.33 n ambient aerosol >/=. x 3 5 (nm) Refractive index effect on LS-AMS sizing method: spherical particles Integrated Light Scattering Signal.. Oleic Acid n =. NH NO 3 n =.55 PSL n = Fomblin n =.3 Nitrate Calibration Curve = ((LS signal +.37)/.7e-)^(/3.9) y = y +A*x pow LS_signal = y + A* pow = (LS_Signal y )/A /pow x 3 5 (nm) 9

10 Error in LS-AMS sizing due to refractive index difference 5 (. < n <.) Oleic Acid. 5 PSL Oleic Acid.59. NH PSL.59 NO 3.55 NH NO Experimental Fit: slope =.3; R =.99 : : Line (LS-AMS) 3 (LS-AMS) 3 Error in the LS-AMS sizing = +/-5% 3 (SMPS) 3 (SMPS) 5 5 LS-AMS Material Density Determination Spherical Particles Exp. Density (g/cc) Material Density (g/cc) SMPS-AMS diameter Measurments Oleic =.9 Oleic Acid =.9 psl =.5 PSL =.3 Fomblin =. Fomblin =.5 AMS-LS (from Nitrate Calibration Curve) OA.5 psl.3 Fomblin.3 d va 3 5

11 Error in LS-AMS density determination LS-AMS density vs SMPS-AMS density. Density (LS-AMS) Nitrate Calibration (.3 < n <.) Curve Nitrate Fit: Calibration slope =.55; (.3 < n R^ <.) = Curve Fit: slope =.55; R^ = Nitrate Calibration (. < n <.) Curve Fit: slope =.975; R^ = Density (SMPS-AMS) Error in LS-AMS density determination. < n <.= +/-5% Point for Discussion Comparison of the mie scattering curves with the experimental scattering signals for spherical particles Collection geometry specifics Potential for LS-AMS determination of optical properties (refractive index)

12 Overview Review system geometry LS-AMS Capabilities Laboratory Aerosols (Sensitivity Analysis) Refractive Index Shape Effect of particle beam divergence on the LS-AMS sizing method Integrated Light Scattering Signal... Larger variance in light scattering signals. Lower light scattering signal intensity NH NH NO NO 3 n = (NH ) SO n =.53 x 3 5 (nm)

13 Evaluation of Particle Beam Divergence composition refractive index % T wire Center Sigma CE_vaporizer 3nm NHNO nm (NH)SO.53. ~.7 ~..5 mm wire in center blocking position FractionTransmitted Position on Vaporizer Surface (mm) Evaluation of Particle Beam Divergence composition refractive index % T wire Center Sigma CE_vaporizer 3nm NHNO nm (NH)SO.53. ~.7 ~. LS_sig.5 mm wire in center blocking position.5 FractionTransmitted Integrated LS_sig Position on Vaporizer Surface (mm). 3

14 Effect of particle beam divergence on the LS-AMS sizing method 5 NH NO 3 n =.55 (NH ) SO NH NO n = 3.53n = (NH ) SO Fit: slope =.933; R^ =.997 : Line (LS-AMS) 3 Error in LS-AMS sizing due to particle beam divergence = +/-9% 3 (SMPS) 5 Effect of shape and refractive index on LS-AMS sizing Integrated Light Scattering Signal.. NH NH NO NH NO 3 n = NO n = (NH (NH ) (NH SO ) SO n =.53 SO.53 NaNO.53 NaNO 3 n = Pb(NO 3 ) n =.7 x 3 55 (nm)

15 Effect of shape and refractive index on LS-AMS effective density measurement Effective Density (LS-AMS) 5 3 Nitrate Calibration pnts (.3 < n <.) Nitrate Curve: Calibration slope pnts =.9; (.3 < R^ n < =.) Nitrate Curve: slope =.9; R^ = Nitrate Calibration pnts (. < n <.) Nitrate Curve: slope =.9; R^ =.99 refractive index range (. < n <.) particle beam divergence (. < σ <.7) Error in effective density measurement = +/- 7% 3 Effective density (SMPS) 5 Summary of Laboratory Results Validated the use of a general calibration curve based on NH NO 3 particles for LS- AMS sizing and subsequent density measurements Material densities for spherical (S=) particles determined to within ρ = +/-5% (. < n <.) Effective densities of nonspherical (S<) particles ρ eff = +/-7% (. < n <.) and (. < σ <.7) 5

16 Overview Review system geometry LS-AMS Capabilities Laboratory Aerosols (Sensitivity Analysis) Refractive Index Shape Ambient Aerosol Analysis with a LS-AMS Chebogue Point, Nova Scotia Field Application of the LS-AMS Objectives Test the application of an NH NO 3 calibration curve to ambient aerosol characterization Provide a continuous measure of the effective density of the ambient aerosol distribution Provide an in-situ quantification of the refractory number and/or particle bounce events

17 NEAQS-ICARTT (July August 5, ) Ground Site: Chebogue Point, Nova Scotia Northwesterly Flow: Remote Continental Southwesterly Flow: Anthropogenic Dominated Partial Time Trend for the Experiment Frac Comp ug/m 3 SO Org NH NO 3 7// 7// 7// 7/3/ date 7

18 Effective Density(g/cc) Frac Comp Partial Time Trend for the Experiment Effective Density Chemical Composition ug/m 3 SO Org NH NO 3 7// 7// 7// 7/3/ date Effective Density(g/cc) Frac Comp Partial Time Trend for the Experiment Effective Density LS-AMS Effective Density Chemical Composition ug/m 3 SO Org NH NO 3 7// 7// 7// 7/3/ date

19 Comparison of Effective Density Measurements LS-AMS Effective Density (g/cc) : Line Organic Mass Fraction Chemical Composition Effective Density (g/cc) Designation of six distinct plume events SO Org NH NO 3 ug/m // 7// 7// 7/3/ date 9

20 CE for Sulfate Dominated Plumes Light Scattering plume..... plume 3 dn/dlogdva Species Ammonium.+/-.3 Sulfate.37 +/-. Organic.+/-. Organic+Sulfate.39+/ Dva dn/dlogdva Light Scattering Species Ammonium.5+/-. Sulfate.7 +/-.5 Organic.7+/-. Organic+Sulfate.7+/ plume Dva Average CE_bounce ~.7 +/-.5 3 Light Scattering dn/dlogdva 5 5 Species Ammonium.5+/-. Sulfate.53+/-.9 Organic.5+/-.9 Organic+Sulfate.5+/ Dva Designation of six distinct plume events SO Org NH NO 3 ug/m // 7// 7// 7/3/ date

21 CE for Organic Dominated Plumes dn/dlogdva dn/dlogdva plume Light Scattering Species.+/-.3 Ammonium Sulfate. +/-. Organic.3+/-. Organic+Sulfate.+/ Dva plume 5 Light Scattering 5 Species Ammonium.+/-. Sulfate.3+/-. Organic.3+/-. Organic+Sulfate.3+/-. 5 dn/dlogdva plume Light Scattering Species Ammonium.3+/-.9 Sulfate.3+/-. Organic.3+/-. Organic+Sulfate.3+/ Dva Average CE_bounce ~. +/ Dva Summary of Field LS-AMS Analysis LS-AMS allows a continuous measurement of the effective density of ambient aerosol distributions based on a single NH NO 3 curve for optical size calibration Mixed sulfate organic (characterized by southwesterly flow over urban population centers) ρ eff =.59 g/cc Organic-dominated (characterized by northwesterly flow over remote continental land regions) ρ eff =. g/cc LS-AMS counting method provides an in-situ measurement of Mixed sulfate-organic plumes: ~.7 +/-.5 Organic-dominated: ~. +/-.

AMS Introduction Doug Worsnop. AMS Users Meeting

AMS Introduction Doug Worsnop. AMS Users Meeting AMS Introduction Doug Worsnop AMS Users Meeting Aerodyne Caltech Georgia Tech FZ - Juelich University of Minnesota Desert Research Institute October 21/22 October 24, 23 October 8, 24 25 August, 25 16