Atmospheric Pollution and Reduction Strategies

Q: Which of the following is an important precursor to acid rain? (A) Carbon dioxide, (B) Carbon monoxide, (C) Sulfur dioxide, (D) Radon.
A: (C) Sulfur dioxide ( $SO_2$ ).

Common indoor sources include particulates like asbestos, dust, and tobacco smoke from combustion.
Radon gas is naturally occurring in soil and wells; it is the 2nd leading cause of lung cancer.
Volatile organic compounds (VOCs) are found in furniture paneling, carpets, and lead paint.
Living organisms such as mold, bacteria, and mites require minimized standing water in HVAC systems.
Carbon monoxide ( $CO$ ) acts as an asphyxiant; sources include heaters, gas stoves, and generators used indoors.
Lead found in paint and pipes causes neurological and learning problems.
Sick building syndrome: A building factor or environment with poor ventilation that causes physical symptoms like headaches and respiratory problems.

Major health risks from toxic air pollutants include breathing problems, lung cancer, and asthma.
Total air pollution was ranked 5th in global death risk factors in 2017.
Loss of life expectancy data: - Tobacco: $2\,\text{yr}, 8\,\text{mo}$ - All Air Pollution: $1\,\text{yr}, 10\,\text{mo}$ - Ambient $PM_{2.5}$ : $1\,\text{yr}$ - Household Air Pollution: $9\,\text{mo}$
Concentrations and emissions of major criteria pollutants in the U.S. have decreased in recent decades due to the Clean Air Act.

The Clean Air Act monitors criteria pollutants categorized by the acronym SPLONC: - $S$ : Sulfur dioxide ( $SO_2$ ) and sulfuric acid ( $H_2SO_4$ ). - $P$ : Suspended Particulate matter ( $SPM_{10}$ , $SPM_5$ , $SPM_{2.5}$ ). - $L$ : Lead ( $Pb$ ). - $O$ : Ozone ( $O_3$ ). - $N$ : Nitrogen oxides and nitric acid ( $NO$ , $NO_2$ , $HNO_3$ , $NO_3^-$ ). - $C$ : Carbon monoxide ( $CO$ ).

Catalytic converters: Required on automobiles to convert $CO$ , $NO_2$ , $NO$ , and hydrocarbons into $CO_2$ , $N_2$ , $O_2$ , and $H_2O$ ; they contain the valuable metal rhodium.
Vapor recovery nozzle: Reduces VOCs emitted from gasoline pumps.
Particulate removal: Accomplished via electrostatic precipitators and baghouse filters.
Sulfur dioxide ( $SO_2$ ) reduction: Accomplished via fluidized-bed combustion and wet scrubber units.
Dry scrubbers: Chemically or physically remove $CO_2$ , sulfur dioxide, mercury, and particulates.

Causes: Formed as a secondary pollutant when nitrogen oxides ( $NO$ or $NO_2$ ) and sulfur oxides ( $SO_2$ ) mix with water vapor.
Sources: Natural (volcanoes) and anthropogenic (vehicles and coal factories).
Transport: Effects are often felt far from the source due to long-range atmospheric transport during chemical reactions.
Impacts: Changes soil chemistry, kills trees/vegetation, and acidifies lakes.
Buffering: Soil and bedrock made of limestone can buffer changing pH levels.