Air Quality Standards for Ozone Assignment 1: Group 6 Ozone (O3) is a triatomic molecule consisting of three oxygen atoms. Ozone is a pale blue gas at 161 Kelvin (‐112 Celsius) it condenses to form a dark blue liquid. Concentrated gaseous ozone can detonate at boiling point, temperatures below 80 Kelvin (‐193 Celsius) ozone forms a violet‐black solid. Ozone can be beneficial or damaging to the environment depending on the location in the atmosphere. At ground level ozone is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in presence of sunlight. Troposphere, ground‐level or ‘bad’ ozone is an air pollutant that damages human health, vegetation and many common materials. The troposphere extends to a level of about 10 miles above ground level. The stratosphere or ‘good’ ozone layer protects life on earth from the sun’s harmful ultraviolet rays (UV‐b) which extends upward from 10 to 30 miles. Due to growing concern to public health and the environment, the Clean Air Act was amended requiring EPA (U.S Environmental Protection Agency) to set National Ambient Air Quality Standards for pollutants considered harmful to the public health and the environment. There are two types of National Ambient Air Quality Standards: •
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Primary Standards Provide public health protection. Secondary Standards Provide public welfare protection. Protection against decreased visibility and damage to animals, crops, vegetation and buildings. There are six principal or criteria pollutants EPA has set National Ambient Air Quality Standards depending on the category (primary/secondary), averaging time, level and form. Ozone was set as a primary and secondary standards, an averaging time of 8‐hour, level of 0.075 ppm (parts per million) and an annual fourth‐highest daily maximum 8 hr‐concentration averaged over 3 years. In conclusion, industries and machineries that contribute to the air pollutants must be regulated and inspected to meet the requirements set by the EPA. www.policyalmanac.org/environment/archive/ozone.shtml
www.en.wikipedia.org/wiki/Ozone
www.epa.gov/air/criteria.html