Smog Los Angeles PittsburghDallas

Causes of Smog Smog is caused by: Smoke Particles Ozone NO 2 Many others

Pittsburgh Has always been known as a smoky town Still beats L.A and Dallas for air pollution

Pittsburgh Had many steel mills and made widespread use of cheap West Virgina coal 1944

Pittsburgh The hills trapped the smog and sometimes turned day into night. 8:40 AM, :00 AM 1949

Donora, Pa. Worst air pollution disaster in the United States Killer smog on Halloween 1948 Started the clean air movement Donora, 1946 US Steel open hearth furnace, Donora, Pa.

Donora, Pa. The Largest Zinc Smelting plant in the world, and a U.S. Steel plant too All in the Monongahela River valley, surrounded by hills

The Donora Disaster October 27, 1948 Thick smoky fog lasted for 5 days Couldn’t see Halloween parade 70 people died in a week 6,000 were medically treated because they couldn’t breathe Population was only 14,000 Only 2 hospitals and 8 doctors in town CO 2, NO 2, SO 2, and F 2 were all to blame

Donora, Pa. Donora is remembered as a key event that inspired federal air pollution legislation in the 1960s and 1970s. It contributed indirectly to the establishment of the U.S. Environmental Protection Agency in Regulations were put into place and by 1955 the Pittsburgh area had cleaned up emissions by 97 percent. In 1963, the United States Congress passed the Clean Air Act. Donora, Noon, 1948

Pittsburgh Local regulations and the Clean Air Act of 1963 has had a visible impact Liberty Tunnel – vs 1965

Pittsburgh today 2009

What makes smog so bad? Smog consists of NOX (NO 2 ) and Ozone (O 3 ) It is extremely toxic and corrosive. Virtually all the plant life was dead for a ½ mile around Donora even before 1948.

What makes smog so bad? Repeated exposure may permanently damage lungs or aggravate respiratory infections. It reduces lung function or aggravates existing respiratory conditions such as asthma, emphysema or bronchitis. It causes chest pain, coughing, throat irritation or congestion.

Let’s look at NO 2 Why is it so bad? Why is it so reactive? How many valence electrons does it have? 5 + 2(6) = 17 electrons It’s an odd number 8 pairs and one more electron

Lewis Structure of NO 2 8 ½ pairs of electrons

Lewis Structure of NO 2 Extra stability added due to resonance But still not the most stable compound around Bent molecular structure

Formation of N 2 O 4 Sometimes two NO 2 molecules combine to form N 2 O 4 The Nitrogen has a full octet now. It makes the molecule more stable, but it must not be too strong, because it takes very little temperature to break it.

A constantly shifting balance or equilibrium reaction As the weather temperature climbs into the 100 o F range, the N 2 O 4 breaks back apart into NO 2. N 2 O 4  NO 2 Clear gas Cold days Less reactive Full octet Red-Brown Gas Hot Days More reactive Odd # electrons

NO 2 rears its head on hot days As the temperature climbs into the 100 o F range, a reddish brown haze appears in the sky if NO 2 is present.