Transcript Environmental Chemistry - Robert Morris University

Environmental Chemistry
Chapter 4:
The Environmental and Health
Consequences of Polluted Air – Outdoors
and Indoors
Copyright © 2012 by DBS
Haze
• Particles with diameter ~ visible light (0.4-0.8 μm) scatter light
Acid Rain
• Natural rain water has dissolved CO2 which forms carbonic acid
(weak acid)
CO2 + H2O ⇌ H2CO3
Ka = 10-1.5
H2CO3 ⇌ H+ + HCO3-
Ka = 10-6.4
• Natural rain water pH of 5.6. Rain water with pH < 5 is acid rain
• Two predominant acids responsible for the acid rain are
H2SO4 and HNO3
• This pollution is not limited by state or country boundaries!
Effects of Acid Rain
•
•
Acidification of surface water (lakes, rivers, etc), and subsequent
damage to aquatic ecosystems.
– kills aquatic plants, fish and microorganisms in lakes and streams
by releasing ions of Al, Pb, Hg and Cd from soils and sediments.
Damage to forests and vegetation
– Weakens or kills trees, especially conifers at high elevations;
– Makes trees more susceptible to diseases, insects, drought, and
fungi and mosses that thrive under acidic conditions;
– Stunts growth of crops such as tomatoes, soybeans, spinach,
carrots, broccoli and cotton
June 23 1980
Damage to Buildings and Statues
1944
CaCO3(s) + H+ → Ca2+ + HCO3- (aq)
HCO3-(aq) + H+(aq) → H2CO3 (aq) → CO2 (g) + H2O(aq)
2004
The Ecological Effects of Acid Rain
Major problems in Europe
and East Coast.
Ohio Valley pollution is
responsible or the acid
rain in Ontario
Global Pattern of acidity pattern
Neutralization of Soil by Acid Rain
In North America most of
the acidity comes from
the burning of high sulfur
content coal in power
plants
The effect of acid rain on
biological life depends
upon the composition of
soil and bedrock in the
Area
– Acid Neutralizing Capacity
(ANC)
Regions of North America with low soil alkalinity
Neutralization of Acid Rain by soil
CaCO3(s) + H+ → Ca2+ + HCO3-(aq)
HCO3-(aq) + H+(aq) → H2CO3(aq) → CO2(g) + H2O(aq)
Acidity from the rain deteriorates soil by
removing plant nutrients:
K+, Ca2+, Mg2+ attached to –ve sites on
clay and organic matter
H+ trades places and is retained
‘Base cations’ K+, Ca2+, Mg2+ leached into
subsoil or washed away
Neutralization of Acid Rain by soil
Although SO2 emissions have
decreased over the years, rain
acidity remains high(lack of fly ash
emission which used to neutralize
acidity)
Thousands of lakes have become
strongly acidified
The acid rain problem of Northeast
now extends to southeast
Wet sulfate deposition
Neutralization of Acid Rain by soil
Hubbard Brook
New Hampshire experimental station
Half of Ca2+ and Mg2+ leached by 1996, vegetative growth almost stopped
Release of Aluminum into Soil and Water
Bodies by Acid Rain
Acidified lakes also possess elevated concentrations
of Al3+ ions - leached from rocks and soil (exchanged with H+)
Decreases fish populations
Havas and Jaworski, 1986
Human Health Effects
Air Pollution
•
•
Historic air pollution problem was high levels of
smoke and SO2 arising from the combustion of
sulfur-containing fossil fuels
Major threat now posed by automobiles, principally
CO, NOx, VOCs and particulates (PM10)
– Photochemical reactions of NO2 and VOCs
from vehicles leads to the formation of O3, a
secondary long range pollutant
– Acid rain is another long-range pollutant
influenced by vehicle NOx emissions
SO2
CO
NOx
Pb
HC’s/VOC’s
PM
O3
Smog
Acid Rain
Toxic Organics
CO2???
Health Effects of Outdoor Pollutants
Carbon monoxide: binds to hemoglobin in red blood cells & reduces ability of blood to
carry oxygen
Sulfur dioxide: causes constriction of airways & can cause bronchitis
Nitrogen oxides: irritate lungs, cause conditions similar to bronchitis & emphysema
Ozone: causes coughing, chest pain, shortness of breath, & eye, nose & throat irriation
Volatile organics: cause mutations, reproductive problems, & cancer
Read p116-120
AQI
•
•
•
The Air Quality Index is a
scale used to report actual
levels of O3 and other
common pollutants
The higher the AQI value,
the greater the health
concern
As shown in the table, the
AQI scale is divided into
categories that correspond
to different levels of health
concern
Action days are usually called when the AQI gets into the unhealthy ranges. Different air
pollution control agencies call them at different levels. In some places, action days are
called when the AQI is forecast to be Unhealthy for Sensitive Groups, or Code Orange
Source: http://airnow.gov
Health Effects of Outdoor Pollutants
•
•
Inferred from epidemiology
Main target organ – lungs
…The Bad
•
•
•
Damages forests and crops; destroys nylon, rubber, and other
materials; and injures or destroys living tissue
A threat to people who exercise outdoors or with respiratory problems
High concentrations of O3 cause plants to close their stomata ( cells on
the underside of the plant that allow CO2 and H2O to diffuse into the
tissue. This slows down photosynthesis and plant growth. O3 may also
enter the plants through the stomata and directly damage internal cells
Rubber, textile dyes, fibers,
and certain paints may be
weakened or damaged by
exposure to ozone.
Some elastic materials can
become brittle and crack,
while paints and fabric dyes
may fade more quickly
Source: http://www.ucar.edu
Health Effects
Ozone can
inflame the
lung's lining
Ozone can irritate your respiratory system
Ozone can reduce lung function and make it more difficult for you to
breathe as deeply and vigorously as you normally would
Ozone can aggravate asthma. When ozone levels are high, more
people with asthma have attacks that require a doctor's attention or the
use of additional medication. Also, asthmatics are more severely
affected by the reduced lung function and irritation that ozone causes in
the respiratory system
Healthy Lung
Ozone can inflame and damage cells that line your lungs. Within a
few days, the damaged cells are replaced and the old cells are shedmuch in the way your skin peels after a sunburn
Ozone may aggravate chronic lung diseases such as emphysema
and bronchitis and reduce the immune system's ability to fight off
bacterial infections in the respiratory system
Ozone may cause permanent lung damage. Repeated shortterm
ozone damage to children's developing lungs may lead to reduced lung
function in adulthood
Lung Lining
Inflamed by O3
Source: http://airnow.gov
Health Effects of Particulates
•
Increase the risk of
cardiovascular diseases and
mortality
– Ultrafine may be especially
dangerous
(current drive to reduce
PM2.5 may be dangerous)
– Particles penetrate the
lungs, blocking and irritating
air passages
– Toxic substances present in
the particles
Indoor Air Pollution
Indoor air quality is important since people spend more times indoors than
outdoors
Source: burn coal & wood; carpet, tobacco smoke
Formaldehyde: H2C=O,
– Stable intermediate of oxidation product of methane
– Can reach up to 1000 ppb (1 ppm) ……as compared to 10 ppb outdoors
Nitrogen Dioxide: NO2
– Homes that burn of natural gas (stove, heater, furnace) or kerosene have
higher level of NO2
Carbon Monoxide: CO
– Colorless, odorless gas whose concentration indoors increases from
incomplete burning of carbon based fuels.
Tobacco Smoke
– Refers to a family of six naturally occurring silicate minerals that are
fibrous. ……causes lung cancer
Read more about indoor pollutants in the textbook p127-135)
Absorbed: dissolves
Adsorbed: stick to the surface
Question
Carbon monoxide binds to hemoglobin 320 times more effectively than oxygen does. Continuous
exposure of more than 50 ppm CO is accompanied by some observable impairment, 250 ppm results in
loss of consciousness and 750 ppm can result in death. A room having the dimension 4 m x 3 m x 8 m
is kept at 20°C by a natural gas (CH4) space heater.
Write the two balanced chemical equations for the combustion of CH4 to produce (1) CO2 and
water and (2) CO and water
CH4 + 2O2 → CO2 + 2H2O
(1)
CH4 + 3/2 O2 → CO + 2H2O (2)
The fuel-air mixture of the heater is running slightly rich (CH4:O2 ratio of 1.00:1.92)
resulting in some incomplete combustion to CO2. Calculate what percent of the total
carbon oxides produced is carbon monoxide
CH4:O2 is 1:1.92
A combination of the two reactions above (Eq. (1) and (2)) occurs. Let x represent the
contribution of Equation (2) and 1-x the contribution of Equation (1)
1.92 = 2(1-x) + 1.5(x)
x = 0.16
 16% of the total carbon oxide gases are CO.
The heater combusts 10.0 g of methane per hour. Assuming all
the carbon monoxide from the heater is expelled into the room
Question
and there is no ventilation,
how long will it take before there is a
danger of losing consciousness?
Moles (CH4) = mass(CH4) = 10.0 g
M(CH4)
= 0.623 mol
16.042 g/mol
Moles (CO) = (0.623 mol)(0.16) = 9.97 x 10-2 mol
P(CO) = nRT/V = 9.97 x 10-2 mol x 0.0821 atm K-1 mol-1 x 293K = 2.5 x 10-5 atm
9.6 x 104 L
At 1 atm.
ppm (CO) = 2.50 x 10-5 atm x 106 ppm = 25 ppm / hr
1 atm
Time to reach 250 ppm = 250 ppm
=10 hr
25 ppm/hr
In 10 hrs there is a danger of an occupant losing consciousness
Relationship Between PM 2.5 and Daily Deaths in 6 Cities
Fine particles that originated
from auto emissions and
sulfate from burning of coal
are responsible for increased
mortality rate
Cities with high PM2.5
(~20 mg m-3) had 1.4% higher
death rate than cities with 10
mg m-3
A 10 mg m-3 drop results in
36000 fewer earlier deaths per
year
The shaded area represents
uncertainty in data points
NO THRESHOLD!!!
Schwartz et al., 2002
US Death Map
Mega Cities
Source: UNEP/WHO, 1992
Laws
•
In 1955, after many state and local governments had passed legislation
dealing with air pollution, the federal government decided that this
problem needed to be dealt with on a national level. This was the year
Congress passed the Air Pollution Control Act of 1955, the nation's first
piece of federal legislation on this issue. The language of the bill identified
air pollution as a national problem and announced that research and
additional steps to improve the situation needed to be taken. It was an act
to make the nation more aware of this environmental hazard.
Eight years later, Congress passed the nation's
Clean Air Act of 1963. This act dealt with reducing
air pollution by setting emissions standards for
stationary sources such as power plants and steel
mills
Clean air act was amended in 1970 and 1990
Source: http://www.ametsoc.org/sloan/cleanair/
Principal provisions :
1970: Clean Air Act
1. Establishing National Ambient Air Quality Standards (NAAQS). The law requires
that EPA identify and set standards for pollutants identified as harmful to human
health and the environment
The six "criteria" pollutants are:
Carbon monoxide
Nitrogen dioxide
Ozone
Sulfur dioxide
Particulate matter with aerodynamic size less than or equal to 10 μm (PM-10)
Lead.
2. Primary and Secondary Standards. The Clean Air Act establilshes two categories
of air quality standards: Primary standards set limits to protect public health.
Secondary standards set limits to protect against public welfare effects, such as
damage to farm crops and vegetation
3. Leaded gasoline phasedown. The law requires leaded gas to be phased out by
the mid-1980s — one of the single most important and successful environmental
health initiatives of the last century