cive 230 lec 7 - criteria pollutants and models of air quality

defining air quality

Minimizes public exposure to pollution, reduces global impact of air pollution, does not damage physical infrastructure, and allows for modern economic activities.

Importance of air quality

Globally 6.7 million premature deaths/yr associated with poor air quality. WHO estimated that 2 million people die per year from illness attributed to use of household fuels only. Air pollution kills 5,400 people a day in China, representing 17% of all deaths in the country.

Main reasons for air pollution

Main reasons of air pollutions are anthropogenic processes (human

activities); transportation (mobile sources), industrial activities, energy

production for heating and cooking (stationary sources)

Air Pollutant

Any chemical or substance in the atmosphere that negatively impacts health, the environment, or the economy.

Primary Pollutants

Substances emitted directly into the atmosphere. Example: Carbon monoxide, nitrogen oxides and hydrocarbons emitted when fuels are burned

Secondary Pollutants

Substances created by physical processes and chemical reactions in the atmosphere. Example: Ozone created by chemical reaction of volatile organic compounds (VOCs) and NOx in the presence of sunlight

Criteria Pollutants

Air pollutants with national air quality standards that define allowable concentrations in ambient air. Examples are CO, O3, NO2, SO2, PM10 and PM2.5, Pb.

How are air pollutants are created from fuel

One of the major sources of air pollutants is combustion of fossil fuels (producing CO2, CO, HC). Most fuels have a number of other elements such as N, S, Pb, and Hg that produce emissions

Carbon Monoxide (CO)

Colorless, odorless, tasteless, poisonous gas produced by incomplete combustion of carbonaceous fuels.

Over two-third mass of all the air pollutants

Source of CO

over 80% of total CO emissions from transportation, almost 100% of CO emissions in urban areas from motor vehicles

How is CO produced

carbonaceous fuels are burned under less than ideal conditions, incomplete combustion of fuel yields CO

Reasons of Incomplete Combustion

Inadequate supply of oxygen, Low combustion temperature, Low combustion chamber turbulence

CO's effect on the body

Interferes with blood's ability to carry oxygen by binding to hemoglobin to form carboxyhemoglobin (COHb), reducing oxygen flow.

Ozone (O3)

Natural gas composed of three oxygen atoms, found in two types: Good (stratospheric) and Bad (tropospheric).

Source of ozone

In the stratosphere, it forms naturally when highly energetic solar rays interact with oxygen molecules (O2), splitting them into individual oxygen atoms, which then combine with other oxygen molecules to form ozone. In the troposphere, ozone is created through chemical reactions between volatile organic compounds (VOCs) and nitrogen oxides (NOx), primarily in the presence of sunlight

Good Ozone (Stratospheric Ozone)

Occurs naturally in the upper stratosphere and absorbs harmful ultraviolet radiation.

Bad Ozone (Tropospheric Ozone)

Also known as tropospheric ozone or ground-level ozone, created by human actions through chemical reactions between NOx and VOC.

Impacts of ozone

Ozone can cause respiratory problems, reduce lung function, and harm the environment by damaging vegetation and ecosystems. It also contributes to secondary pollutants and climate change.

Sources of Nitrogen Oxides (NOx)

thermal processes when air is heated during combustion since air has nitrogen; combustion of fuel molecules that have nitrogen compound in themselves.

Which nitrogen oxides are important air pollutants?

• nitric oxide (NO) - 95% of anthropogenic emissions

• nitrogen dioxide (NO2) - reacts with OH to form HNO3, corrodes metal surfaces and contributes to acid rain problem

Nitrogen oxide and oxygen reactions

NO2 reacts with O2 to form O3 in the presence of sunlight: VOCs + NOx + Sunlight = Photochemical smog (O3 + etc)

Nitrogen dioxide participates in ozone formation, so after its concentrations peak, so do concentrations of ozone.

When do ozone concentrations peak

during hours of maximum sunlight, around middle of day

environmental impacts of NOx

• ground level ozone (smog)

• acid rain and acid vapour/particles

• reduces visibility by blocking light

• GHG 300x more damaging than CO2

anthropogenic sulfur dioxide sources

86% of the anthropogenic sulfur oxide emissions are the result of fossil fuel combustion, and most of that is emitted from coal-fired power plants.

Acid Rain

Rainfall with a value of pH between 5 and 5.6 is called this and is the wet deposition of sulfur pollution.

PM10

Particulate matter with a diameter less than 10 microns

PM2.5

Particulate matter with a diameter less than 2.5 microns

Particulate Matter (PM)

Very small matter, solid or liquid mixture, ranging from 0.0005 micrometer (µm) diameter to coarse particles up to 100 µm. also called aerosol.

How are PMs emitted

directly from incomplete combustion of fossil fuels, as carbonaceous particles. NOx and SO2 also transformed into liquid droplets of sulfates and nitrates.

PM2.5 effects

Include increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing, decreased lung function; aggravated asthma; development of chronic bronchitis; irregular heartbeat; nonfatal heart attacks; increased risk of premature death in people with heart or lung disease

How is lead emitted/removed from atmosphere

emitted in atmosphere in form of particulates, removed by settling

effects of airborne lead

Airborne lead affects human population by direct inhalation, and ingested when deposited on soil, water, food crops

Volatile Organic Compounds (VOCs)

• Volatile Organic Compounds that evaporate from solvents, fuels, and other organics, along with unburned and partially burned hydrocarbons emitted from tailpipes and smokestacks when fossil fuels are not completely combusted

• precursors for smog

what sectors are responsible for most of anthropogenic VOC emissions

transportation and industrial facilities (50/50)

Clean Air Act in 1970

Established National Ambient Air Quality Standards (NAAQS) and required States to develop standards and State Implementation Plans (SIPs).

Air Quality Index (AQI)

Widely used performance indicator of air quality, computed based on contaminant levels and threshold values.

sick building syndrome

health and comfort effects experienced by building occupants that are linked to time spent in a building, but where no specific illness or cause can be identified