E10: Smog (UNMODIFIED)

Word

Word Form: SMoke + fOG

2 

2 Main Types: Pea Soup Smog (reducing smog) Source = fog + SOx + soot +ash Cold and wet weather conditions Combustion of sulfur containing coal (industry, power plants, homes) Photochemical Smog (oxidizing smog) Source: VOCs + NOx + Sunlight (create many secondary pollutants such as O3 and PANS) Sunny and Dry Weather Conditions Vehicle Exhausts

Conditions to the Formation of Photochemical Smog Temperature/ Thermal Inversions- Warm layer of air forms between 2 cool layers- Cool air in lower atmosphere cannot flow upwards- Pollutants remain in the lower atmosphere Bowl Shaped Cities- Surrounded or bordered by mountains- Promote formation of temperature inversions- Night time ground cooling- Movement of warm air masses over mountains Windless Conditions (and many coastal communities)- No horizontal movement of air away from cities- Pollutants build up in the lower layer Ultraviolet Radiation from the Sun- Promotes the existence of free radicals within the atmosphere (which can react with other substances to make photochemical smog)

NOFormula: N2 + O2 --> 2NOSource:High temperature conditions in internal combustion engines in road vehicles

VOCsExample: Unburned HydrocarbonsSource:Incomplete combustion in internal combustion engines in road vehicles

NO2 Where it came from:Oxidizing of NOProperties:Reddish brown in color (gas)Formula: NO + 1/2 O2 --> NO2Another method: Free Radicals Production UV light from sun starts photochemical reactions NO2 absorbs UV light (produce NO and O•) O• = very reactive (will react with other chemicals in the atmosphere)

O3Where it came from:Reaction between O• and O2 at ground levelFormula:O• + O2 --> O3Effects: Very harmful and damaging pollutant Cause eye, nose and throat irritation Damage plants and many materials (e.g. rubbers and metals)

OH•Formula: O• + H2O --> 2 OH•Effects:React with other free radicals in atmosphere to make more photochemical smog

HNO3Where it came from:Hydroxyl free radicals react with NO2 to form Nitric AcidFormula: •OH + NO2 --> HNO3

R•Where it came from:Hydroxyl free radicals react with hydrocarbon VOC (RH) to produce reactive hydrocarbon free radicalsFormula: •OH + RH --> R• +H2O

ROO•Where it came from:Hydrocarbon Free Radicals react with O2 to form extremely reactive peroxidesFormula: R• + O2 --> ROO•

RCHO

RCHOWhere it came from:Peroxides lead to the formation of aldehydes and ketonesEffects:Aldehydes and ketones contribute to the formation of aerosols, which reduce visibility

PAN Where it came from: Smorgasbord of reaction - terminated when perxode free radicals react with a free radical of NO2 to form PAN Formula: ROO• + •NO2 --> ROONO2Properties and Effects: Relatively stable Very powerful lachrymators (eye irritants) Respiratory Irritants

Introduction

Primary Pollutants and Source (of Photochemical Smog)

Secondary Pollutants (of Photochemical Smog)