Fossil vs Contemporary Carbon at 12 Rural and Urban Sites in the United States Bret A. Schichtel (NPS) William C. Malm (NPS) Graham Bench (LLNL) Graham Bench (LLNL) Charles E. McDade (UCD) Judy C. Chow (DRI) Judy C. Chow (DRI) John Watson (DRI)

Urban & Rural Annual Organic Carbon Speciated PM2.5 monitoring networks: IMPROVE – Rural sites STN – Urban/suburban sites

Urban & Rural Annual Organic Carbon

Carbon Isotope ( 14 C/ 12 C) Network Summer: Jun – Aug ‘04; Winter: Dec ’04 – Feb ‘05 Summer: Jun – Aug ‘05; Winter: Dec ’05 – Feb ‘06 Summer: Jul – Aug ‘02 Lake Sugema Brigantine Proctor Maple Puget Sound Mt. Rainier Sula Rocky Mt. Grand Canyon Phoenix Tonto Great Smoky Mt. Yosemite Six day HI-VOL PM2.5 samples

Contemporary (Biogenic) Vs Fossil Carbon C 14 half life ~5700 yr C 14 half life ~5700 yr f M = 0 for fossil C f M = 0 for fossil C f M ~ 1.08 for biogenic C f M ~ 1.08 for biogenic C Fraction Contemporary = f M /1.08 Fraction Contemporary = f M /1.08 Samples corrected for positive organic artifact on filters Samples corrected for positive organic artifact on filters Summer 2004

Seasonal Contemporary and Fossil C (  g/m 3 ) The error bars represent the range in six day concentrations

Seasonal Fraction Contemporary Carbon The error bars represent the fraction contemporary range

Urban Excess Puget Sound, WA (Blue) – Mt. Rainier, WA (Red) Puget Sound fossil carbon is primarily due to local sources during winter and summer Puget Sound fossil carbon is primarily due to local sources during winter and summer Summer biogenic carbon is regionally distributed Summer biogenic carbon is regionally distributed ~40% of the winter urban excess is biogenic carbon ~40% of the winter urban excess is biogenic carbon Not all biogenic carbon is “natural” Not all biogenic carbon is “natural” Puget Sound Mt Rainier

Urban Excess Phoenix, AZ (Blue) – Tonto, AZ (Red) Phoenix fossil carbon is primarily due to local sources during winter and summer Phoenix fossil carbon is primarily due to local sources during winter and summer Summer biogenic carbon is regionally distributed Summer biogenic carbon is regionally distributed About half of the winter urban excess is biogenic carbon About half of the winter urban excess is biogenic carbon Not all biogenic carbon is “natural” Not all biogenic carbon is “natural” Phoenix Tonto

IMPROVE Fine Particulate Carbon On average HiVol total carbon was 10-20% greater than IMPROVE On average HiVol total carbon was 10-20% greater than IMPROVE All monitors were collocated with IMPROVE monitors measuring OC and EC using thermal optical reflectance (TOR) All monitors were collocated with IMPROVE monitors measuring OC and EC using thermal optical reflectance (TOR) IMPROVE collects 24-hour PM2.5 samples every third day IMPROVE collects 24-hour PM2.5 samples every third day Total Carbon: SummerTotal Carbon: Winter

Fraction Biogenic Vs EC/TC Summer EC/TC Summer EC/TC Fossil ~ 0.36 Fossil ~ 0.36 Biogenic ~ 0.12 Biogenic ~ 0.12 Winter EC/TC Winter EC/TC Fossil ~ 0.45 Fossil ~ 0.45 Biogenic ~ 0.19 Biogenic ~ 0.19 Winter/Summer Winter/Summer Fossil: 1.25 Fossil: 1.25 Biogenic: 1.58 Biogenic: 1.58 Seasonal Averages 6-Day Averages

EC/TC Ratios from IMPROVE Data Edge Analysis Rural 10 th %-ile edge ~ Biogenic EC/TC Rural 10 th %-ile edge ~ Biogenic EC/TC Summer – 0.07 Summer – 0.07 Winter – 0.16 Winter – 0.16 Urban 90 th %-ile edge ~ Fossil EC/TC Urban 90 th %-ile edge ~ Fossil EC/TC Summer – 0.41 Summer – 0.41 Winter – 0.44 Winter – 0.44

Measured Primary EC/TC Ratios Mobile Sources – Fossil Carbon Mobile Sources – Fossil Carbon Adjusted Roadside: EC/TC = 0.39 (Chow et al., 2004) Adjusted Roadside: EC/TC = 0.39 (Chow et al., 2004) 1996 Sepulveda. CA tunnel study: EC/TC = 0.57 (Gillies et al., 2001) 1996 Sepulveda. CA tunnel study: EC/TC = 0.57 (Gillies et al., 2001) Light duty vehicle: EC/TC = 0.3 (Cadle et al., 1997) Light duty vehicle: EC/TC = 0.3 (Cadle et al., 1997) Heavy Duty Diesel: EC/TC = 0.63 (Lowenthal et al. 1994) Heavy Duty Diesel: EC/TC = 0.63 (Lowenthal et al. 1994) Wood Smoke – Biogenic Carbon (McDonald et al., 2000) Wood Smoke – Biogenic Carbon (McDonald et al., 2000) Softwood in fireplace: EC/TC = 0.2 Softwood in fireplace: EC/TC = 0.2 Hardwood in fireplace: EC/TC = 0.1 Hardwood in fireplace: EC/TC = 0.1 Hardwood in woodstove: EC/TC = 0.11 Hardwood in woodstove: EC/TC = 0.11 Texas grass and soft and hardwood: EC/TC = 0.2 (Chow et al., 2004) Texas grass and soft and hardwood: EC/TC = 0.2 (Chow et al., 2004) Cooking Cooking EC/TC = 0.1 (Chow et al., 2004) EC/TC = 0.1 (Chow et al., 2004) Secondary organic aerosol Secondary organic aerosol EC/TC = 0 EC/TC = 0

Comparison of EC/TC estimates Projected fossil and biogenic EC/TC ratios are in line with other estimates Projected fossil and biogenic EC/TC ratios are in line with other estimates Summer Fossil EC/TC ratio is on low side Summer Fossil EC/TC ratio is on low side Literature summer EC/TC higher than C 12/14 and EC/TC edge analyses Literature summer EC/TC higher than C 12/14 and EC/TC edge analyses Literature examined primary aerosol Literature examined primary aerosol Fossil and Biogenic EC/TC is smaller in the summer than the winter indicating some summertime SOA formation for both Fossil and Biogenic EC/TC is smaller in the summer than the winter indicating some summertime SOA formation for both

Fraction Biogenic - Summer The summer (June-August) IMPROVE carbon data were partitioned into fossil and biogenic carbon using the derived fossil and biogenic EC/TC ratios

Fraction Biogenic - Winter The summer (December - February) IMPROVE carbon data were partitioned into fossil and biogenic carbon using the derived fossil and biogenic EC/TC ratios

Estimating Secondary Organic Carbon (SOC) Assume: Assume: All elemental carbon is primary All elemental carbon is primary Winter organic carbon is primary (PC) Winter organic carbon is primary (PC) Summer organic carbon is primary + secondary Summer organic carbon is primary + secondary

Fraction Secondary Organic Carbon for Summer Months 42% of the summertime organic carbon is secondary 42% of the summertime organic carbon is secondary 32% of the summertime fossil carbon is secondary 32% of the summertime fossil carbon is secondary If some winter organic carbon is secondary than these summer SOC contributions are lower bounds If some winter organic carbon is secondary than these summer SOC contributions are lower bounds

Summary Biogenic carbon accounts for Biogenic carbon accounts for 80-95% of the total carbon at the rural sites 80-95% of the total carbon at the rural sites 70-80% of total carbon at near urban sites 70-80% of total carbon at near urban sites 50% of total carbon at urban sites 50% of total carbon at urban sites Little seasonality and total variation in fraction modern carbon Little seasonality and total variation in fraction modern carbon Urban fossil carbon is primarily due to local sources during the winter and summer Urban fossil carbon is primarily due to local sources during the winter and summer Summer biogenic carbon is regionally distributed Summer biogenic carbon is regionally distributed 40-50% of the winter urban excess is biogenic carbon 40-50% of the winter urban excess is biogenic carbon Not all biogenic carbon is “natural” Not all biogenic carbon is “natural”

Summary 42% or more of the summertime organic carbon is secondary 42% or more of the summertime organic carbon is secondary 32% or more of the summertime fossil carbon is secondary 32% or more of the summertime fossil carbon is secondary

Finished