Ozone Budget From: Jacob

Ozone in the Atmosphere Lifetime: –~1 month –Highly variable – dependent on season, latitude, altitude, etc. Background concentrations: –less than 40 ppbv –can reach over 200 ppb in urban areas

Ozone in the Atmosphere From: Fishman et al., 2005, Atmos. Chem Phys. Discuss., 3, 1453

HO x Sources and Sinks Source: oxidation of VOCs: Sinks:

HO x Cycle

HO x in the Atmosphere Lifetime: –~1 second –highly variable (same reasons as for O 3 ) Typical concentrations: –~5 x 10 6 molecules/cm 3 –higher over oceans and southern hemisphere less anthropogenic CO and methane

NO x Sources and Sinks Sinks: From: Jacob

Nighttime NO x Chemistry There is no NO at night: sink -when the sun comes up

Peroxyacetylnitrates (PANs) Organic radicals of the form: RO ROO R(O)OO can sequester NO 2. The most common is PAN: CH 3 C(O)OONO 2.

NO x Cycle

NO x in the Atmosphere The lifetime of NO x varies, but is about 1 day near the surface and about 1 week in the upper troposphere. Concentrations range from a few pptv to 10’s of pptv. –higher concentrations near the ground. Urban areas may reach concentrations of 10s of ppbv.

NOx in the Atmosphere From: Lamsal et al., 2008, J. Geophys. Res., 113, D16308, doi: /2007JD009235

CO Budget From: Jacob

CO in the Atmosphere The lifetime of CO is about 2 months with respect to oxidation by OH CO is not well mixed globally –remote concentrations: ppbv –over populated continental regions: ppbv –in urban centers: > 1ppmv

CO in the Atmosphere From: Barret et al., 2005, Atmos. Chem Phys. Discuss., 5, 4599

CO in the Atmosphere

Methane Budget From: Jacob

Methane in the Atmosphere The overall lifetime of methane is 8.5 yrs. Current concentrations are about 1.8ppmv. –up from 800 ppbv preindustrial –methane and CO 2 concentrations track each other over geological time periods.

Methane in the Atmosphere

Beyond CO and Methane There are literally thousands of volatile organic compounds (VOCs) present in the atmosphere in trace amounts (pptv-ppbv). Many have short lifetimes –Low concentrations –Big influence on chemistry

Biogenic VOCs Terpene compounds are emitted by trees: Isoprene Monoterpene Sesquiterpene

Biogenic VOCs Globally, about 80% of VOCs emitted to the atmosphere are biogenic. Anthropogenic VOCs dominate only in industrial or some urban areas.

Photochemical Smog

O3O3 OH RO 2 RO HO 2 H2O2H2O2 HNO 3 O3O3 O3O3 P HOx k1k1 k2k2 k3k3 k4k4 k5k5 k6k6

Photochemical Smog

Case 1: Low NO x -O 3 production varies linearly with NO x -independent of hydrocarbons NO x -limited regime

Case 2: High NO x

-O 3 production varies linearly with hydrocarbons -varies inversely with NO x Hydrocarbon-limited regime

Ozone Pollution From: Jacob

Ozone Pollution In the background atmosphere:

Ozone Pollution In the urban atmosphere, there is a competition between NO 2 and RH for the OH radical: As a rule of thumb:

Why too much O 3 is a bad thing Health effects: –Irritation of the lungs (short exposure to high concentrations). –Permanent lung damage (long-term exposure). –Effects are worst for the elderly and people with asthma. Ecosystem effects: –Reduced photosynthesis (low crop yields). –Increased susceptibility to pests. –Leaf scarring.

Ozone Air Quality Standards Federal: –1 hour maximum concentration = 120 ppbv –8 hour average maximum concentration = 75 ppbv State of California: –1 hour maximum concentration = 90 ppbv

Ozone Problem Areas From: EPA

Air Quality Index From: EPA

Air Quality Index

Peak Ozone for California From: Data Not Available AQI

LA Region Maximum Ozone From: California Air Resources Board

LA Region Ozone Exceedance From: California Air Resources Board

Sacramento Region Max Ozone From: California Air Resources Board

Sacramento Region Annual Ozone From: California Air Resources Board

Sacramento Ozone Exceedance From: California Air Resources Board

Sacramento Region Ozone Ozone data from: California Air Resources Board

Data Not Available Ozone data from: AQI