Envi Sci 114 4
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- PLANTS & OZONE
-
humans: exposure usually = response
plants: exposure may not = response
depends on environmental
conditions being right
- OZONE CONTACT WITH LEAVES
-
uptake via stomata
contact with mesophyll cells
reaction with waxes & cuticle on epidermis
polarity may increase
surface more hydrophobic
cations & other solutes may leak
- OZONE IN THE SUBSTOMATAL CAVITY
-
ozone reacts with moist surfaces of
mesophyll cells
reactive oxygen (Ro) species form
highly reactive and cause oxidative injury
ozone cannot be measured inside the leaf
ozone leaves no break-down products
- DETOXIFICATION
-
excess oxidative capacity dissipated
in a controlled manner
examples of antioxidants
reductants ascorbate
enzymes superoxide
constitutive dismutase
induced
present or produced proportionally to
amount of ozone entering
- OZONE INJURY INCIDENCE
-
occurs in mid-late
summer
occurs on older
lower leaves
occurs on upper
leaf surfaces
injured areas do not
cross leaf veins
- ACUTE OZONE INJURY
-
cell membranes break down
cell contents leak, cells die necrosis
mesophyll cells affected first
then palisade parenchyma cells
phenolic pigments may accumulate in
palisade parenchyma cells
- CHRONIC OZONE INJURY
-
low concentrations on a long-term basis
chloroplasts affected - chlorosis
premature leaf fall & senescence
anthocyanin pigments - bronzing
- PLANT GROWTH EFFECTS
-
photosynthesis affected
changes in allocation patterns
accelerated senescence
reduced flowering and yields
reduced secondary (radial) growth
reduced root systems
reduced mycorrhizal formation
increased incidence of diseases
and insects
- BIOINDICATORS
-
Useful to evaluate relative air quality for ozone
sentinels reliable
special care
non-native
detectors respond when conditions
are right
ecologically relevant
-
PARTICLE SIZE
trimodal distribution -
fine particles:
nuclei mode condensation of vapors
accumulation mode grow in size
coarse particles:
from abrasion
- PARTICLE SIZE
-
.001 - 500 microns
molecular clusters to visible particles
suspended droplets or particles are
called aerosols
- Natural sources of particles
-
natural sources
pollen
fungal spores
salt spray
soil from wind erosion
volcanoes
biological decomposition
trees terpenes
- Human sources of particles
-
human activity
soot from combustion diesel exhaust
fly ash from combustion
iron oxide steel mills
metallic vapors smelting
power plants
fecal dust megaplex areas
stone dust rock crushing
catalytic convertors sulfate aerosol
- Particle Size and Behavior
-
• Size determines effects of gravity
• Nuclei mode particles behave as gases
o Subject to Brownian motion
o Low settling velocities, travel distances
• Capable of coagulation and enlargement
o The process is called “scavengingâ€
o Fine particles do not become course particles!
• Course particles are affected by gravity
- Particle Classes and Sources
-
⬢ Based on origin and formation
⬢ Primary
o Produced by chemical and physical
processes emitted as is
⬢ Do not change much in air
⬢ Rock crushing, grain milling
⬢ Secondary
o Natural sources
⬢ Volcanoes, terpenes from trees,
biological decomposition
o Anthropogenic sources
⬢ Combustion
o Over 50 % of ambient aerosol secondary
sources is from natural sources
- Secondary Aerosols from Anthropogenic Sources
-
⬢ The most common secondary aerosols from anthropogenic emissions
⬢ Sulfate and nitrate aerosol from SO2 and NO2 from combustion
⬢ Involved in visibility reduction
⬢ Involved in acidic decomposition
- Some Changes in Particles in the Troposphere
-
⬢ Grow in size
o Collide and adhere (coagulate)
⬢ Adsorb gaseous molecules on surfaces
⬢ Change electrical charge
⬢ Undergo deliquescence(liquefy)
⬢ Are removed by deposition depending on size
- Aerosol Generation
-
⬢ Fume aerosols
o Combustion and condensation
⬢ Dust aerosols
o Fragmentation of matter
⬢ Mist aerosols
o Atomization of liquids
⬢ Smoke
o Gases, particles, droplets
- Particulate Air Pollution and Human Health
-
⬢ Its all about transfer of oxygen from lungs to blood and/or transfer of toxicants from surfaces of respired particles to blood
⬢ Reduced lung capacity
⬢ Toxins transferred to other organs
- The Human Respiratory System
-
⬢ Air is inhaled via nose (or mouth)
⬢ Passes through nasopharyngeal system
o The upper airway
⬢ Passes through tracheobronchial system
⬢ Ends up in pulmonary system
⬢ Air is exhaled
- The Respiratory Tract
-
⬢ The nasopharyngeal system
⬢ Nasal passages
o Course hairs, cilia, mucus
⬢ Nasopharynx
o Cilia, hairs
⬢ Oropharynx
o Cilia, mucus
- Innate Defense Mechanisms
-
⬢ Nasal Region
o Hairs, cilia, mucus
⬢ Sneeze Reflex
o Upper airway
⬢ Cough Reflex
o Upper part of bronchial tree
- The Respiratory System
-
⬢ The pulmonary system
⬢ Terminal or respiratory bronchioles
o Cilia and mucus
⬢ Alveolar Ducts
o Mucus
⬢ Alveoli
o Mucus, phagocytes(eat bacteria and small
particles, Pacman)
- Alveoli
-
⬢ Transfer of oxygen and or toxicants from air or particles to red blood cells
⬢ Tiny sac-like structures attached to bronchioles
⬢ Capillaries surround alveoli
⬢ Transfer through alveolar membrane to capillaries
⬢ 3 million/person
- Direct Irritant Effect
-
⬢ Sulfate aerosol can become sulfuric acid aerosol on contact with water vapor or moist cell surfaces
⬢ This can lead to irritation of the respiratory system
⬢ More serious when combined with ozone and high temperatures
- Respiratory Deposition and Retention
-
⬢ Particles must penetrate respiratory defense mechanisms
⬢ Particles larger than 10 microns are not retained
⬢ Inhalable : smaller than 10 microns are deposited in the upper respiratory system
⬢ Removable anything larger than 2.5 microns are removed from the upper respiratory system
- Effects of Adsorbed Substances from Pm 2.5 particles
-
⬢ Damage to organs distant from lungs
⬢ Concentrations of adsorbed substances increase with decreasing particle size due to increased surface area
⬢ PAHs
⬢ Metals
o Pb, Cd Zn, Hg
- Lead
-
⬢ Ubiquitous (its everywhere)
⬢ Inhalation of particulate Pb
⬢ Enters blood from alveoli
⬢ Deposited in bone, excreted, or causes problems
⬢ Ingestion of lead paint particles
⬢ Absorbed by blood from intestines
- Symptoms of Lead
-
⬢ Chronic anemia
o Pb inhibits enzymes in hemoglobin synthesis
⬢ Acute (a lot of lead)
o Kidney damage
o Brain damage
⬢ Cross-placental transfer
o Mentally-retarded children - URBAN ADVANTAGES
-
population in small dense areas
jobs
essential services available
cultural opportunities
- URBAN DISADVANTAGES
-
crowding
slums
pollution
poverty
health effects
- MODIFICATIONS CAUSE CHANGES
-
Natural vegetation removed and replaced with
paved surfaces and high density buildings
This affects:
absorption of solar radiation
storage of heat
surface & air temperatures
water absorption & evaporation
turbulence & wind – “urban canyonsâ€
- URBAN CANYONS
-
Streets with rows of high buildings on both sides - like the canyon of a river
Building heights and orientation of the
canyon determines incoming solar radiation,
heat retention, and wind speed
Views of the sky may be obscured
- HUMAN ACTIVITIES CAUSE CHANGES
-
High energy demands by residents:
heating
cooling
appliances, computers
transportation
dining, entertainment
- URBAN HEAT ISLAND (UHI)
-
A metropolitan area which is significantly
warmer than its surroundings
This effect is greatest at night
“On hot summer days, urban air can be
2-10F hotter than the surrounding
countrysideâ€*
* US EPA
- HOW UHI FORM
-
“Heat islands form as vegetation is replaced by asphalt and concrete for roads, concrete and stone for buildings and other structures
needed to accommodate growing populationsâ€
US EPA
- SOLAR RADIATION IS ABSORBED
-
Paved surfaces and buildings absorb and hold solar radiation, rather than reflecting it
This causes surface temperatures and overall
ambient temperatures to rise
- NATURAL COOLING DECREASED
-
The process of water evaporation provides
cooling of ambient air
evaporation from soil: non-paved areas
evapotranspiration from vegetation: well-
watered plants
- ANTHROPOGENIC HEAT INPUT
-
air conditioning in summer
refrigeration
heating in winter
public transport
private cars
factories
- UHIs & RAINFALL
-
Rainfall is usually higher in urban areas
Monthly rainfall can be as much as 28%
higher 20-40 miles downwind of a city
- VEGETATION AND UHIs
-
Vegetation can mitigate UHIs
Directly
by shading heat absorbing surfaces
Indirectly
by evapotranspirational cooling
- TREES & GREEN SPACES
-
Evapotranspiration in tree crowns
cools the air
Air moving through the tree moves the cooler air into the non-tree area
Large numbers of trees can reduce
local air temperatures by 1-5 F
- USING VEGETATION TO REDUCE URBAN HEAT
-
Plant trees to shade roofs and south-, east-,
and west-facing walls
Use trees to shade roads & parking lots
Green roofs reduce heat in buildings
Parks & greenspace cool off neighborhoods
- WATER IN THE CITY
-
The amount of rainfall in urban areas is usually higher than in surrounding non-urban areas
Evapotranspiration is much lower
Surface run-off is greater
Water storage is lower
- WHY RAINFALL IS HIGHER
-
Mainly due to short but intensive rainfall events
Air pollution results in small particles that serve as condensation nuclei for raindrops
UHIs favor cloud formation
Low wind speeds favor high relative humidity
- AIR POLLUTION IN URBAN AREAS
-
Combustion of fuels for transportation and energy generation
Gasoline & diesel oil for transportation
nitrogen oxides
small hydrocarbons (VOCs)
carbon monoxide
photochemical oxidants
ozone
nitrogen dioxide
- SOILS IN URBAN AREAS
-
Most urban soils are either highly disturbed
or man-made soils
The ideal soil, as described in textbooks,
is difficult if not impossible to find in urban areas
Urban soils provide extreme and often severe conditions for plant growth
- CHARACTERISTICS OF URBAN SOILS
-
great verical and horizontal variability
compressed structure leading to compaction
surface crusts on bare soils – hydrophobic
modified pH, usually elevated
restricted water drainage and aeration
interrupted nutrient cycling
restricted microbial activity
presence of pollutants & other materials
modified soil temperatures
- EFFECTS OF COMPACTION
-
normal water and gas movement impaired
this creates conditions that are either:
excessively wet or
excessively dry