John G. Watson Judith C. Chow Mark C. Green Xiaoliang Wang Desert Research Institute, Reno, NV

Transcription

1 One Year Survey of Brown and Black Carbon Contributions in the U.S. John G. Watson Judith C. Chow Mark C. Green Xiaoliang Wang Desert Research Institute, Reno, NV Presented at: 17 IMPROVE Steering Committee Meeting Ely, MN October, 17

2 Objectives Examine measurement reproducibility and filter loading effects for ~3, IMPROVE and CSN 1 samples. Demonstrate the separation of brown carbon (BrC) from black carbon (BC) using multiwavelength analysis. Characterize transmittance attenuation for source and ambient samples. Present seasonal and spatial patterns of BrC and BC.

3 Methods to Calculate Aerosol Radiation Absorption AAAAAA λλ = llll FFFF λλ,ff FFFF λλ,ii (1) bb AAAAAA λλ = AAAAAA λλ AA VV () bb AAAAAA λλ 11 bb AAAAAA λλ = λλ 11 λλ AAAAAA (3) AAAAAA λλ = qq BBBB λλ AAAAAA BBBB + qq BBBBBB λλ AAAAAA BBBBBB () Where: AAAAAA is the radiation attenuation FFFF λλ,ii and FFFF λλ,ff represent the filter transmittance before and after thermal carbon analysis, respectively bb AAAAAA is the attenuation coefficient A is the filter deposit area (3.53 cm ) V is the 5 mm IMPROVE sample volume (33.1 m ) AAE is the absorption Angström exponent qq BBBB and qq BBBBBB represent the fitting coefficients

4 High correlations across wavelengths are found for carbon and light attenuation replicates (17 IMPROVE and 11 CSN) Correlation coefficient (r) OCR* IMPROVE CSN Correlation coefficient (r) Light Attenuation IMPROVE CSN Wavelength Wavelength *Organic carbon by reflectance

5 Replicate ATN is less comparable for ATN> (filter loading and multiple scattering effects not compensated) IMPROVE y =.99x +.1 ATN 5 r =.99 ATN 5 Replicate Punch Attenuation Initital Punch Attenuation y = 1.x +. ATN 35 ATN r = Replicate Punch Attenuation Initital Punch Attenuation ATN y =.9x ATN r =.99 9 Replicate Punch Attenuation Initital Punch Attenuation Replicate Punch Attenuation Replicate Punch Attenuation Replicate Punch Attenuation CSN y =.97x +.9 r =.95 Initital Punch Attenuation y =.95x +. r =.97 Initital Punch Attenuation y =.97x +. r =.97 Initital Punch Attenuation AAAAAA λλ = llll FFFF λλ,ff FFFF λλ,ii AAAAAA is the radiation attenuation FFFF λλ,ii and FFFF λλ,ff represent the filter transmittance before and after thermal carbon analysis, respectively

6 ATN 5 becomes less related to EC at higher concentrations* (due to both loading and BrC) IMPROVE CSN ATN at y = -5.1x +.x r =.9 y = 3.x +. r =.9 ATN at y = -1.x x r =.99 y =.7x +. r = ECR 35 (µg/m 3 ) ECR 35 (µg/m 3 ) *Averaged over each 5 th percentile range of ECR by reflectance at 35

7 Wavelength-dependent decrease in attenuation occurs for highest 5% of EC concentrations. 3 ATN λ ( ) Lowest 5% ECR nd 5% ECR 3rd 5% ECR Highest 5% ECR Highest 1% ECR Wavelength () ATN multiplied by wavelength (λ) for the highest 1 th percentile and each 5 th percentile of EC by reflectance (ECR) concentrations for the 1 CSN samples.

8 Spectral Light Attenuation BC and BrC Contributions to Attenuation Diesel Exhaust Spectral attenuation Smoldering Pine Cones Smoldering Peat varies by source (up to 1% BrC with high AAE for smoldering pine cones) Flaming Pine Needles

9 AAE varies with different calculation methods Source AAE (7λ fit) AAE (5_9 ratio) AAE (5_35 ratio) Diesel Diesel Diesel Diesel.5..7 Diesel Diesel Tunnel.1.. Smoldering Pine Cone Flaming Pine Needle Peat Peat Prescribed Burning Prescribed Burning Prescribed Burning Prescribed Burning Yosemite Rim Fire The wavelength ratios at 5 and 35 are used to derive the power-law fit of b ATN

10 Enhanced light attenuation by BrC is found at shorter wavelengths (average attenuation due to BrC 5 is.7% for CSN and 1.9% for IMPROVE) Percent of Attenuation by BrC 5% % 15% 1% 5% IMPROVE CSN y = λ y = λ -.1 % Wavelength () The wavelength ratios at 5 and 35 are used to derive the power-law fit of b ATN

11 IMPROVE 5 35 CSN 5 35 Only.% of IMPROVE and 1.% of CSN samples have >1% attenuation by BrC at 35 (showing that BC is a good indicator at 35 but misses BrC contributions)

12 Higher AAEs in IMPROVE than CSN suggest increased contributions from biomass burning and aged aerosol in non-urban enviroents Average AAE (5-35 ).5 IMPROVE non-urban CSN Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Monthly average AAE values derived from the wavelength ratios at 5 and 35 (Eq. 3) at the non-urban IMPROVE and urban CSN sites.

13 BC light attenuation (b ATN ) at 5 is ~ times higher at CSN than IMPROVE sites 3 b ATN at 5 by BC (mm -1 ) IMPROVE non-urban CSN Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Where: bb AAAAAA λλ = AAAAAA λλ AA VV and AAAAAA λλ = llll FFFF λλ,ff FFFF λλ,ii

14 BrC light attenuation (b ATN ) at 5 increases at CSN sites during winter, indicative of residential wood combustion 3. b ATN at 5 by BrC (mm -1 ) IMPROVE non-urban CSN. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

15 High BC and BrC in fall (non-urban Kaiser Wilderness*) b ATN at 5 (Mm -1 ) b ATN at 5 (Mm -1 ) High BC and BrC in winter (urban Fresno, CA) bᴀᴛɴ- ʙrᴄ bᴀᴛɴ-ʙᴄ AAE bᴀᴛɴ- ʙrᴄ bᴀᴛɴ-ʙᴄ AAE Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month *73 km northeast of the Fresno site, located at 9 m in the Sierra Nevada mountain range AAE (5-35 ) AAE (5-35 ) Elevated AAE attributed to 1-acre fire 3 km southeast Temporal patterns of BC and BrC vary at non-urban versus urban sites 1 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month 1

16 b ATN at 5 (Mm -1 ) Month *15 km northeast of Bronx at 55 m b ATN at 5 (Mm -1 ) Non-urban Mohawk Mountain, CT* bᴀᴛɴ- ʙrᴄ 7 bᴀᴛɴ-ʙᴄ AAE Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Urban Bronx, NY bᴀᴛɴ- ʙrᴄ 7 bᴀᴛɴ-ʙᴄ AAE AAE (5-35 ) AAE 5-35 Possible influence from Flat Rock Fire (elevated hourly CO concentrations, hourly PM.5 [3µg/m 3 ], and -hour OC [.7 µg/m 3 ] were found on 11/1/1 Mohawk Mountain site shows higher AAEs and higher BrC 5 contributions than the Bronx site (% vs..%) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

17 Elevated carbon and light attenuation by BrC is apparent during fires (Long Pine Key Wildfire in the Everglades National Park; /1-17/1) OC and EC Concentrations Light Attenuation and AAE

18 Spectral Light Attenuation Before fire (3/31/1) BC and BrC Contributions to Attenuation Evolution of fire from flaming to During Fire (/1/1) smoldering is apparent After Fire (/1/1)

19 Conclusions BrC and BC can be quantified based on multiwavelength light attenuation using Model 15. Filter loading effect is apparent for ~5% of samples with the highest EC concentrations; loading corrections need to be implemented. Higher BrC absorption (at 5 ) is found for IMPROVE than CSN samples, suggesting the influence of biomass burning and aged aerosol. Pairing non-urban and urban sites shows potential to distinguish local from regional exceptional events, which can be excluded from attaient designations.