Particulate Matter - PM

Term is for mixture of solid and liquid particles found in the air.

PM Air Pollutionand

Health Risks

Particle PollutionInhalable course particles – diameter larger than 2.5 micrometers and

smaller than 10 micrometersFine particles – diameter that are 2.5 micrometers and smaller

How small is 2.5 μm?30 times smaller thanyour hair…

What is PM?

Particulate matter (PM) describes a wide variety of airborne material. PM pollution consists of materials (including dust, smoke, and soot), that are directly emitted into the air or result from the transformation of gaseous pollutants. Particles come from natural sources (e.g., volcanic eruptions) and human activities such as burning fossil fuels, incinerating wastes, and smelting metals.

PM

Comes in many sizes Comes in many shapes Can be made up from hundreds of chemicals

Size

Primary Particles

Emitted directly from a source Construction sites Unpaved roads Fileds Smokestacks Fires

Secondary Particles

Formed in complicated reactions in the atmosphere of chemicals such as Sulfur dioxides Nitrogen oxides

Emitted from Power plants Industries Automobiles

Make up most of the fine particle pollution EPA regulates inhalable particles

Fine Coarse

Health

Refer to Dr. Pagnozzi’s presentation Problem with particle pollution – fine particles

Premature death Heart disease Lung disease Aggrevated Asthma Decreased lung function Increased respiratory symptoms

Environmental Effects

Visibility Imparement

Fine particles – PM2.5 – main cause for reduced visibility Haze

Affects many areas including National parks Wilderness

Sunlight encounters tiny particlesleading to haze

Clear day

Hazy day

National ParksAcadia National Park, Maine

Everglades, Florida

Sequoia National Park, California

HAZE

Air pollutants come from a variety of natural and manmade sources Natural sources

Soot Wildfires

Manmade sources Automobiles Electric utility Industrial

Formed: Directly emitted Gases emitted to air forming particles as they are carried out for miles

Singapore

Houston, Texas

Environmental Damage

Particles can be carried out long distances by wind and then settle to ground or water

Settling effect: making lakes and streams acidic changing the nutrient balance in coastal waters

and large river basins depleting the nutrients in soil damaging sensitive forests and farm crops affecting the diversity of ecosystems.

Acid Rain

Aesthetic Damage

Particle pollution can strain and damage Stone Other material

Culturally important objects Statues monuments

Acropolis, Athens, Greece

How is PM Regulated?

PM is one of the six EPA “criteria pollutants” that have been determined to be harmful to public health and the environment. (The other five are ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead.)

EPA is required under the Clean Air Act to set national ambient air quality standards (NAAQS) to protect public health from exposure to these pollutants. Areas that exceed the NAAQS are designated as nonattainment, and must institute air pollution control programs to reduce air pollution to levels that meet the NAAQS.

Where does PM originate from?

Sources may emit PM directly into the environment or emit precursors such as sulfur dioxide (SO2), nitrogen dioxide (NO2), and volatile organic compounds (VOCs), which are transformed through atmospheric chemistry to form PM.

PM Implementation

The Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS) for six criteria pollutants; particle pollution (also known as particulate matter) is one of these.  EPA works with partners at state, local, and tribal air quality agencies to meet these standards.

CAA

Under the Clean Air Act (CAA), as amended in 1990, each state must develop a plan describing how it will attain and maintain the NAAQS.  In other words, how it plans to clean up polluted areas and keep them clean.  This plan is called the State Implementation Plan (SIP) and is required under Section 110 of the CAA (40 CFR Part 51, Subparts F & G).  I

SIP collection of programs

A monitoring program, which is a collection of monitoring devices throughout the country which provide actual measurements of the concentrations in the air, to identify whether an area is meeting the air quality standards, and if not, how much reductions are needed to meet those standards;

air quality calculations and computer modeling, which are used to predict future trends and the effects of emissions reduction strategies;

emissions inventories, which describe the sources and categories of emissions to the air for a given pollutant, and how much is emitted by each source or source category;

control strategy studies whose goal is finding the best way to reduce emissions in order to meet air quality standards;

formal adoption of measures (enforceable by EPA, States and citizens) which ensure that we will achieve the reductions deemed necessary in the planning process;

periodic review to evaluate whether those needed reductions were achieved in reality, and whether they had the predicted result.

PM Research

PM2.5 by understanding the potential health effects Atmospheric science

Chemical reactions in the atmosphere Where it comes from and is going to?

Exposure science To learn how and where people become exposed to PM

Controlling PM emissions History of PM Analysis and measurement

PM Concentration

Weather patterns Wind Stability (vertical movement of air) Turbulence Precipitation Topography Smokestack height and temperature of gases

PM Concentration (cont.)

Nearby natural and built structures may lead to downward moving currents causing aerodynamic or building downwash of smokestack emissions.

Role of Inversions

An inversion is an extremely stable layer of the atmosphere that forms over areas. Temperature inversions trap pollutants close to the ground. These inversions involve layers of hot air sitting above cooler air near ground level. When particles accumulate in the air layer, they are unable to rise into the atmosphere where winds will disperse them.

Tilted Plume Model

Gaussian based Incorporates settling velocity of the particle Settling velocity dependent on size Bigger particles fall faster Maximum falling distance can be calculated

Aerodynamic Diameter

Establishing a particle size definition for irregularly shaped particles necessitates the use of a standardized measure referred to as the aerodynamic diameter, measured in microns or micrometers (μm), a unit equal to one millionth of a meter.

Particle Scrubbers Wet collection devices Particle collection by direct contact with a

liquid (water) Many designs Efficiency calculated

Gin

Gas

Lout

Liquid Gasin Gasout

Liquid

Liquid

Gravity Settling Chambers

Simple Long Chamber Slow gas velocity Manual cleaning Low maintenance Baffels distribute flow

Flow

Baffles

Plug Flow

V

Low v (<0.3 m/s)High residence time

L

H

vTS

Calculate minimum diameter of particle collected at 100% theoretical removalEfficiency in chamber with length L.Assumption: no mixing in horizontal or vertical direction.

Cyclones (centrifugal separators)

Employ centrifugal force generated by spinning gas stream to separate PM from carrier gas

Advantages: Low capital cost Low maintenance High temp.

Disadvantages: low efficiency at small dp high efficiency at high loading Empirical designs

HDirtygas

Clean gas

PM to hopper

BafflesCreatee eddies

cyclonesL1

L2

Bag Houses

Fabric filters Considerations:

Row of fabric tubes Size of tubes Tube material A/C ratio Bag cleaning loading

Wait for presentation by Ms. Farris

Electrostatic Precipitator

Components Charging wires Collection plates Rappers Hoppers

Around since 1907

Also used in indoor air quality

How does it work?

Negative corona (EM field) produced by wires Produces negative ions in the gas Ions adsorb onto sides Solids migrate towards positive plates Solid “cake” develops on the plates Cake removed by rapping and collected in hopper

Advantages

High removal efficiency for dp< 1micrometer Large gas volumes with low loading Wet or dry paricles Relatively low opertaing cost

Disadvantages

High capital cost – up to 10s millions Low flexibility – no variables to change Large space requirement No control of gases – as oppose to scrubbers Problem with PM that has high resistivity Complex system

Fabric Filters and electrostatic precipitators are main option for small dp!

How do humans affect the environment?

Landfills - The size of landfills everywhere and the toxins dumped in them is caused by human failure to recycle and human wastefulness.

Methane gas is created when waste decomposes along with plastic toxins; volatile organic chemicals and other harmful things enter our atmosphere and pollute the air we breathe. While landfills themselves are not bad, the rate at which we are filling them up with toxins is detrimental to our environment.

Air Pollution - Humans create air pollution by driving gas-guzzling vehicles and avoiding hybrid and alternative fuel vehicles. Although some industrial plants are utilizing safer methods of chemical releases into the air, many others still spread gases, smoke, and other chemicals into the air polluting it even further.

Water Pollution - Industry and the chemical toxins it produces have found their way into our rivers, streams, and oceans and this results in water pollution. Often, some of these chemicals pollute bodies of water so intensely that water becomes unsafe for drinking, cooking, and swimming.

Wildlife - Wildlife that call our forests and bodies of water home are being affected by the pollution we create. Some species are even close to extinction. Water clean up is not only costly, not enough is being done to prevent oil spills, industry waste pollution, and human waste violations.

Deforestation - As our population expands so does the need for areas to live. Humans have contributed to the loss of our forest areas by cutting down trees that are home to many animals and wildlife. The trees in our forests also help contribute to our water cycle and plants in our forest prevent soil erosion. Unfortunately, due to deforestation, the planet's forests have shrunk by half its area in the past 11,000 years.

Ozone Layer - The ozone layer that protects us from harmful ultraviolet rays is depleted by the use of chlorofluorocarbons (CFCs). CFCs are man-made chemicals that include aerosols, refrigeration equipment, foam, and other chemicals released by industrial companies. UV rays can cause skin cancer and cataracts in humans. Scientists have found an ozone hole in the Antarctic stratosphere, a great concern considering how many CFCs and greenhouse gases are ruining our ozone layer.

Noise Pollution - With more people comes more noisy cars on the road, more office buildings, more parking lots, more horns honking, and more people talking creating noise pollution that some doctors say contribute to hearing loss and headaches.

Smoking - Even though smoking is not safe for humans, people continue to blow smoke from cigars, cigarettes, and pipes into the air we breathe. Many cities and towns have set high standards and created non-smoking environments, however, the smoke released from smokers is still a concern in many parts of the world.