Environmental Science: Air Quality and Pollutants

The AQI measures the daily levels of pollutants like ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. It uses a scale from 0 to 500, with higher numbers indicating worse air quality.

Ozone is a gas made of three oxygen atoms. It naturally exists in the Earth's upper and lower atmosphere. It's very reactive and can harm the respiratory system.

Ozone readily reacts with molecules in our bodies, particularly in the respiratory system, leading to breathing problems.

The ozone layer shields the Earth from harmful ultraviolet radiation (UV-B).

Fine particles are less than 2.5 microns in size, so small that you need a powerful microscope to see them.

Fine particles are formed through the condensation of molecules into solids or liquids. Larger particles are made by the breakdown of materials.

Fine particles are formed by the condensation of molecules, while larger particles are mostly formed by the mechanical breakdown of materials.

Particles with diameters between 2.5 and 10 microns, which have a harder time penetrating the body compared to fine particles.

Sulfur dioxide exposure often occurs alongside particulate matter exposure, and the combined effect is worse than each one individually.

Diesel fuel can contain up to 500 ppm of sulfur by weight.

A group of compounds that cause similar health issues, including CDDs, CDFs, and PCBs.

Dioxins are considered likely human carcinogens.

Generic term for fibrous silicate materials, with chrysotile being a type classified as serpentine.

Asbestos air concentrations are measured in nanograms per cubic meter, usually ranging from 0 to 10 ng/m3.

The most common internal combustion engine, a four-stroke, spark-ignited piston engine invented by Nicholas Otto.

The intake stroke is the first stage in the four-stroke engine cycle. During this stage, the intake valve opens, allowing fresh air and fuel to enter the cylinder as the piston moves downward, creating a vacuum.

Sulfur dioxide increases the harmful effects of ozone when both gases are present.

The compression stroke is the second stage in the four-stroke engine cycle. During this stage, both intake and exhaust valves are closed, and the piston moves upward, compressing the air and fuel mixture in the cylinder.

The power stroke is the third stage in the four-stroke engine cycle. In this stage, the compressed air and fuel mixture is ignited by a spark plug, creating an explosion that drives the piston downwards, producing power.

The exhaust stroke is the final stage in the four-stroke engine cycle. During this stage, the exhaust valve opens, and the piston moves upward, pushing the burnt exhaust gases out of the cylinder.

The stoichiometric air-to-fuel ratio is the ideal mix of air and fuel that results in complete combustion with no leftover fuel or oxygen. It's the perfect balance for optimal engine performance and minimal emissions.

Manual monitoring involves collecting air samples using devices like samplers, filtering the samples, and analyzing them in a laboratory. It provides a snapshot of air quality at specific times.

Continuous monitoring involves using automated sensors that constantly measure air quality parameters. This provides real-time data, allowing for quicker responses to pollution events.

Extractive monitoring involves drawing a sample of air from the source and analyzing it in a separate instrument. This technique provides detailed information about specific pollutants.

Air pollution instrumentation is crucial for monitoring and controlling air quality. It helps us track emissions from sources, assess ambient air quality, and develop strategies to reduce pollution.

Source monitoring focuses on measuring emissions from specific pollution sources like factories or vehicles. Ambient monitoring assesses overall air quality in a specific area, like a city or neighborhood.

A device that draws a gas sample from the exhaust stream for analysis. This involves selecting a representative sample and removing interfering substances.

An instrument that measures the amount of light absorbed by a sample to determine its composition. Used in air quality monitoring for identifying gas pollutants.

Directly measure gas concentrations within the exhaust stack without altering the gas composition.

A type of absorption spectrometer that uses infrared light to measure specific gases, including SO2, NO, CO, CO2, and hydrocarbons.

Measures gas concentration across the entire diameter of the stack, providing a comprehensive picture of the emissions.

The two basic types of Source Emission Monitoring Instrumentation are Opacity Monitors (Transmissometers) and Gaseous Emission Monitors. Opacity monitors measure the light transmittance through a gas stream while Gaseous Emission Monitors measure the concentration of specific gaseous components in the exhaust gas.

Opacity Monitors are further classified into Single-Pass and Double-Pass Systems. Single-Pass Systems have a light source and detector on opposite sides of the stack while Double-Pass Systems have both the light source and detector on the same side with a reflector on the opposite side.

Gaseous Emission Monitors are divided into Extractive and In-situ Systems. Extractive Systems remove a sample of the gas for analysis while In-situ Systems analyze the gas directly in the stack.

In-situ gas emission monitors are further classified into In-stack and Cross-stack Monitors. In-stack monitors measure the gas inside the stack, while Cross-stack monitors measure the gas across the stack.

Opacity monitors provide information about combustion conditions and control device efficiency.

A single-pass opacity monitor has a light source on one side of the stack and a detector on the opposite side. It is more economical but requires process shutdown for calibration checks.

A double-pass opacity monitor has both the light source and detector on the same side of the stack, with a reflector on the opposite side. It meets EPA design criteria and allows calibration without process shutdown.

Double-pass systems meet EPA design criteria and allow for calibration without process shutdown, making them more efficient for continuous monitoring.

In-stack monitors measure the gas directly inside the stack, allowing for an accurate assessment of emissions at the source.

A Cross-stack monitor measures the gas concentration across the stack, capturing a more comprehensive view of emissions.

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