Biogenic Emissions In The Central Valley

Biogenic Emissions in the Central Valley Jonathan Wang Brown University 2010

OUTLINE Introduction

• Project outline, objectives, motivation • Description of isoprene, α-Pinene, β-Pinene

Data

• Methods: sampling and analysis • Limitations

Results

• Ozone contribution (MIR and OFP) • Patterns of emissions: grid vs airborne • Patterns of emissions: seasonal variability

Conclusions

• Flight data: elevated levels near strong sources • Spatial Distribution: surprising urban concentration • Seasonal Dependence: reflect ecological condition

Project Outline Aircraft

and ground grid whole air samples Characterize biogenic or “background” natural hydrocarbon emissions Identify temporal and spatial patterns of biogenic emissions

Isoprene: "Trees cause more pollution than automobiles do." -- Ronald Reagan, 1981 Primary biogenic atmospheric emission Emitted by many woody plants as heat stress response Specific mechanism unknown: may also aid in oxidative stress, circadian rhythm, induce flowering Not emitted from crops, grasses Extremely short lifetime: about an hour High ozone forming potential (MIR =

α-Pinene, β-Pinene Volatile emission from conifers Monoterpenes present in pine resin, essential oils Emitted as defense against fungal infection or injury (bark beetle attack) Extremely short lifetime (0.5-3.5 hours) Small ozone forming potential High secondary organic aerosol

Methods Whole air canister samples collected at 1-3 minute intervals on aircraft July 22nd and 24th WAS collected on grid July 24th throughout Central Valley. Grid samples collected away from dairies, no attention paid to vegetation Gas chromatography, FID and MS Google Earth • Earthpoint, Earthplot

Previous study: Melissa Yang, collected 3/6/2008 : colder climate, only grid (no flight)

Limitations No

biological data collected: cannot compare emissions to evidence of damage, leaf temperature, etc No ozone measurements, so cannot test actual ozone production in high biogenics areas

Ozone Forming Potential

From

Carter, 1998: Maximum Incremental Reactivity estimates Ozone Forming Potential Overestimate: does not consider important aspects such as NOx Top 5 OFP Gases: Isoprene a big factor

Patterns of Emissions: Isoprene from Flights •Overall, low background concentrations •Several hot spots where isoprene reaches altitude •Hot spots indicate source locations: short lifespan precludes transport. •No Sacramento data: can’t fly over heavily populated zone •Integrates area: not so influenced by sources

Patterns of Emission: Isoprene on Grid •Points marked where measured concentration breaks scale •Overall higher concentrations than flights: closer to sources •Source-dominated measurements: grid measurements must be careful •2490 point matches with elevated levels in flight •Sacramento, Fresno: heavy urban zone’s isoprene: parks as source

α-Pinene Flight data 2009

Grid data 2009

•Some match up between flight and grid, not robust •Low concentrations throughout •Point sources reaching up to altitude

“Cold” Grid Data Data

collected for a previous study by Melissa Yang. 3/6/08 vs 7/24/09: about 11.6 degree C difference in temperature Expect

changes in isoprene: no heat stress, no isoprene emissions from oaks

“Cold” Isoprene Noted Differences •On a much lower scale •Fewer, different hotspots •No heat stress: isoprene emissions at T = 25 – 40 C •Avg T in ‘cold’ grid: 18 C •Sacramento emissions drastically reduced •Due to sampling near or far from trees?

“Cold” α-Pinene •Much higher levels of α-Pinene in March than in summer •Significant hot spots around Stockton •Rough latitudinal correlation •Elevated levels in Sacramento •Short lifetime: samples never bleed very far out •Elevated levels related to climate: wetter, colder in March than in

Seasonal Changes

•In the early spring (March): relax heat stress and virtually eliminate isoprene emissions •Colder temperatures: α-Pinene drastically increases •α-Pinene known to have longer lifetime in winter/night •Identify periods of heat stress, pest stress in vegetation based on gas emissions?

Seasonal OFP

•Isoprene contributon to ozone drastically reduced (from 4.7%), ranked 23rd (from 5th) •α-Pinene contribution to ozone greatly increased (from 0.33%), ranked 12th (from 23rd) •Isoprene concentrated at specific sources: small, wooded areas •Urban isoprene significant: parks are a major source! Not just “biogenic.”

Further Work Focus

of project was not on biology Grid samples intentionally taken near and far from forests or even single trees: quantify impact of single, definite sources Diurnal and seasonal measurements Species profile of valley: predict patterns Ozone measurements: direct observation of parks’ impact

Conclusions Isoprene emissions heavily source based: must be mindful of oaks when taking grid samples Strong sources bleed to atmosphere: can be identified by plane (more general, less of a single, overpowering point) Significant contribution to total ozone forming potential Temperature dependence: seasonal fluctuations in emissions and OFP Urban parks contribute much isoprene: seasonality to air quality in urban areas with parks? Gases isoprene, pinene are ecosystem’s “breath” that indicate heat, biotic stresses

Acknowledgements Dr.

Melissa Yang Dr. Donald Blake Dr. Sherwood Rowland University of North Dakota NASA Airborne Science Program Thank

you for listening! <3