MRPO Nitrate and Organic Speciation Special Studies

Donna Kenski

National RPO Technical Meeting

Dallas, Dec. 3-4, 2002

Bondville

Seney

Key Components at Bondville

• Dasgupta monitor: measures gaseous nitric acid, sulfur dioxide, and ammonia (estimated limits of detection 10, 15 and 100 parts per trillion by volume, respectively) for a 15 min period, and then particulate nitrate, sulfate, and ammonium for the next 15 min period.

• Photolytic (true) NO2 and NOy

• Collocated gravimetric PM2.5, continuous PM2.5, speciated 24-hour PM2.5, continuous EC/OC, ozone, and meteorology (temperature, relative humidity, wind speed

and direction, precipitation). • 24-hour and 6-hour denuder samples

More detail on Dasgupta

• PM2.5 size selector• Particles collected by humidification• Gases collected by wet denuder• Both particles and gases analyzed by IC• Ammonia/ammonium analyzed in

separate detector, using porous membrane and conductivity detector

Current Status and Schedule

• Dasgupta, NO2, Noy will be deployed in January, 2003

• Sampling to continue for at least one calendar year

• Challenges: wintertime measurements with wet denuders, full time use of instruments usually used in shorter-term studies

Air Suction

Air Inlet

Water InWater Out

Particle collector

H2O

H2O2

air out to flow controller and pump

particle sample(aq.)

MB

MB MB

P

P P

Pgas sample(aq) air inlet

Denuder

Particle collector

P

. Liquid and airflow arrangement for the denuder, particle collector

What will we learn?

• What controls the formation of nitrate: HNO3 or NH3:

– HNO3(g) + NH3(g) --> NH4NO3(s)

• What effect will reductions in SO2 and SO4 have on NH4NO3 : additional NH4 available from SO2 reductions could increase NH4NO3

• Diurnal variations in HNO3 and NH4 may lead to answers about sources

Indicator SpeciesExcess Ammonia (Blanchard, et al, 2000) and

Gas Ratio (Ansari and Pandis, 1999)

Excess Ammonia Gas Ratio

EA < 0 NH3-limitedEA > 0.1 HNO3-limited

GR < 0.4 NH3-limitedGR > 1.5 HNO3-limited

Organic Carbon at Seney• Organic matter can account for 50% or more of particle mass in

summer at Seney NWR, Boundary Waters, and other remote pristine sites.

• Origin of OCM not obvious:– transported urban pollution– local biogenic– local and/or transported forest fires– other??

• Source apportionment of IMPROVE data isn’t definitive (but efforts continue), hampered by too few species, degraded air far from sources, similarities among combustion sources (for quantified species).

Seney NWR, Michigan

What is organic speciation?• Method developed by Glen Cass, Jamie Schauer, many others

• Quartz filters, XAD-coated denuders, or PUF cartridges can be analyzed

• Filters extracted with hexane, then benzene/2-propanol, split, one fraction derivatized (to convert organic acids to methyl esters for GC/MS identification), and both fractions analyzed by GC/MS

• 100s of species can be identified, some unique tracers of sources: – resin acids for soft wood combustion– syringols for hard wood combustion– levoglucosan for wood combustion– cholesterol for meat cooking– hopanes and steranes for diesel combustion

Sampling plan for Seney NWR• PI: Jamie Schauer at UW-Madison• Quartz filters collected at Seney (2/3 day) will be

composited by month and analyzed for particle phase organic species for Jan ‘02 - Dec ‘02 period

• Source apportionment will be conducted based on tracer species

• Additional daily high-volume samples were collected and a subset of those will be analyzed and apportioned

• Selected molecular markers will be analyzed for single-compound carbon isotope ratios

• Interim report due Jan. 1 2003, final Nov. 1 2003