anthropogenic disruption of nutrient cycles - air pollution

8/10/2019 Anthropogenic Disruption of Nutrient Cycles - Air Pollution

1/16

Anthropogenic disruption of nutrient cycles

Bio. 152, Chapter 17

Carbon: human activities increase CO2release to

troposphere by 25% (at least) over natural rates of releaseHow is carbon released naturally? ocean degassing,natural fires and respiration

Nitrogen: human activities increase release ofN-compounds by 300% over natural rates (as NO, NO2, N2O

and NH3)

How is N released naturally? bacterial denitrification

(NO3-to N2)

Sulfur: human activities increase sulfur inputs totroposphere by 200% over natural rates (as SO2)

How is S released naturally? volcanoes and asdimethylsulfide gas from oceans

Metals:Arsenic: 200% increaseCadmium: 700% increaseLead: 1700% increase (decreasing with Pb-free gasolineand paints)

Mercury: at least 25% increase, maybe 50%


2/16

Urban Smog

Brown-air vs. Gray-air Smog


Brown-Air Smog:primary source is vehicle emissions, most prevalent duringsummer - more intense uv radiationresults from photochemical reactions that transform primarypollutants into secondary pollutantsNO2, O3and PANs - photochemical oxidants - initiate

oxidation reactions (in atmosphere and inside lungs tocause health problems)worse in the afternoon, after peak pollutant release and sunexposurechemistry: see diagram

Gray-Air Smog:historically associated with coal and heavy oil burning incities for heat, source is primarily industrial, most prevalent

in winter1273: King Edward I banned coal burning in London(later reversed)1911: 1,100 Londoners died from exposure to coalsmoke1948: Denora, PA, which had a steel mill, zinc smelterand sulfuric acid plant

extended thermal inversion trapped pollutants

causing 6,000 citizens (of pop. of 14,000) to becomeill (20 died)


3/16

Urban Smog

Brown-air vs. Gray-air Smog (con't)


Gray-Air Smog:Chemistry:

Coal combustion:C (in coal) + O2 ----- CO2(and 2CO) + soot

S (in coal) + O2----- SO2(sulfur dioxide)

Metal smelters:

PbS + O2----- SO2Then:

2 SO2+ O2----- 2SO3(sulfur trioxide)

SO3+ H2O ----- H2SO4(sulfuric acid)

H2SO4+ 2NH3----- (NH4)2SO4(ammonium sulfate)

Ammonium sulfate and soot give gray color tosmog

Not as big a problem as before 1950 because of tallersmokestacks that disperse pollutants and better air pollutioncontrol laws and devices (scrubbers that remove S andprecipitators that remove soot)

Factors affecting smog formation:climate: rain cleans, wind blow pollutants elsewheretopography: mtns. trap pollutantspopulation density

amount of industryenergy source


4/16

Acid Rain


What is acidity?

How is acid deposition formed?

What areas are sensitive to acid deposition?downwind from major power plants, smelters or cities

Great Lakes states are responsible for more than50% of the acid deposition that falls in NortheasternUS and southeastern Canada1980s: intense disputes between Canada and USover acid rain

Reagan's strategy was to say that moreresearch was required before costly legislationcould be proposed

1990 Clean Air Act: US to cut SO2

emissions to 50% of 1980 levels and NOx

emissions by 33% by 2000.

areas with sensitive soils (low conc. of Ca2+and Mg2+)to buffer acidic inputs - which can happen afterlong-term exposure to acid deposition


5/16

Acid Rain (continued)

Bio. 152, Chapter 17 and Hedin, L.O. and G.E. Likens, 1996. AtmosphericDust and acid rain. Sci. Amer. Dec. 88-92.

What are the effects of acid rain?etching of structuresrespiratory diseases (asthma and bronchitis)in soils (from Hedin and Likens)

clay and humus material are slightly negatively charged,

so these particles attract positive cations (Ca2+, Mg2+,

Na+, K+)H+ in acid rain displaces positive cations from soilparticles, which causes free cations to be mobilizedacidity also increase the formation and solubility of free

Al3+ions, which can also displace Ca2+and Mg2+frombinding sites on soil particles

result: more acidic soils with more free toxic Al3+ions

trees: esp. on mtn. tops where soils are thin and conifersexposed year-roundindirect effect by making trees more susceptible to cold,disease, insects, drought and acid-tolerant fungilower nutrient availability

release of bound Al3+, which damages tree roots


6/16

Acid Rain

Bio. 152, Chapter 17 and Sparling, D.W. 1995. Acid Deposition: a review ofthe biological effects in Hoffman et al. Handbook of Ecotoxicology. LewisPubl. Boca Raton, Fl. pp. 301-329.

What are the effects of acid rain? (continued)lakes: esp. mtn. lakes with slow turnover

1. Al3+leached into lakes binds with phosphorous (P)forming an insoluble complex (at pH 5-6). Less available Pacts to limit nutrient availability, leading to oligotrophicconditions2. high [H+] impairs the ability of invertebrates, amphibians

and fish to maintain ionic balance (Na+, K+and Cl-) which iscritical to cell function

disruption of the ability to maintain ionic balanceresults in many cations being excreted through thegills

Al3+ions cause stimulation of excessive mucousformation in many fish, resulting in asphyxiation anddeathsublethal effects include reduced growth,

deformations, behavioral changes and decreasedreproductive successfish species differ in their sensitivity to acidicconditions, resulting in changes in communitystructure

3. increased availability to other toxic metalsPb and Cd are more soluble or toxic at low pHincreased rates of Hg methylation by anaerobicbacteria - producing the highly toxic methyl-Hg form

4. decrease in species richness (biodiversity), but notnecessarily biomass5. acid shock: spring snowmelt delivers pulse of acidicwaters to which some species cannot adapt


7/16

Acid Rain (con't)

Bio. 152, Chapter 17 and Hedin, L.O. and G.E. Likens, 1996. AtmosphericDust and acid rain. Sci. Amer. Dec. 88-92.

What can be done?prevention approaches:

reduce energy consumption, esp. fossil fuelsswitch from coal to natural gas or renewable sourcesburn low-sulfur coal (lignite or anthracite, not butuminous)remove S from coal before/after combustion

remove nitrogen oxides from motor vehicle exhaustcleanup approaches:lake liming: add CaCO3to buffer lakes

expensive ($8 billion for US) and temporary, kills someplankton

add phosphate fertilizer to neutralize lakes

PO43-ions stimulates phytoplankton populations, which

remove nitrates and produce OH-

Why does it continue to be a problem despite reductions inatmospheric releases of acidic compounds? (Hedins and Likens)

1. Some areas still have enormous releases: Norilsk, Russia2. Decrease in releases of atmospheric dust (particulate matter)

atmospheric dust released primarily through burning fossilfuels, cement manufacturing, and mining and metalprocessingthis dust is high in CaCO3and MgCO3, which act as bases

(the opposite of acids)

atmospheric dust represents the largest single input of basecations to some forest ecosystems


8/16

Clean Air Act Provisions

1970 , and amended in 1977, 1990 and 1997


1. EPA must establish National Ambient Air Quality Standards (NAAQS) forthe seven major outdoor pollutants (revised O3and PM stds. in 1997)

primary pollutants: threat to human healthsecondary pollutants: threat to environment and propertymaximum permissible concentration when averaged over time for agiven area

areas that do not meet NAAQS are called nonattainment areas

2. The priority of sites was established though the policy of prevention ofsignificant deterioration

protect the relatively clean areas first

3. EPA must set national emission standards for 20 classes of compoundsand 300 individual compounds

standards currently exist for only a fraction of this list because:expensive

scientific uncertainty not up to courtroom scrutiny

4. Congress to establish timetables for reductions in emissionscoal plants: cut 1991 SO2emissions by 50% by year 2000

cut 1991 NOxemissions by 33% by year 2000

motor vehicles: reduce CO, HCs, and NOxemissions

1994: further emissions reductions for HCs and NOx2003: emission control mechanisms must operate in cars for100,000 miles (instead of current 50,000)

oil companies: must make cleaner fuels available in dirtiest cities

(highest O3)


9/16

Clean Air Act (con't)


Clean Air Act has been a significant piece of legislation30% reduction in most pollutants between 1970 and1995Pb decreased 78% (Pb-free gasoline), althoughreplacement antiknock agent is carcinogenic....

O3 in urban areas decreased by 50%Economic benefits have outweighed costs by at least6:1

BUT90 million people still live in urban areas in which airquality standards are not met (the nonattainment areas)it does not adequately:

encourage pollution preventionimprove fuel efficiency standardsregulate fine particulates, municipal incineratoremissions, and greenhouse gas emissions

governmental lobbies and Congress is constantly tryingto weaken it

*know some ways to reduce air pollution


10/16

Respiratory Physiology

Structure and importance to effects of air pollutants

Bio. 152, Chapter 17 and Menzel, D.B. and M.O. Amdur. 1986. Toxic responses of therespiratory system in Casarett and Doull's Toxicology (Eds: C.D. Klassen, M.O. Amdurand J. Doull). Macmillan Publishing Co., NY. pp. 330-359.

Important features: respiration involves 40 cell types, including 17specialized types of epithelial cells

nose:hairs to filter out largest particles

upper respiratory tract (trachea or windpipe):sticky mucous lining that captures smaller particles and

some gaseous pollutants (the water-soluble gases)cilia on columnar epithelial cells move mucus and particlesupward (rate of transport = 1-3.5 cm per minute)

lower respiratory tract (bronchioles and alveoli within lungs)bronchioles are bifurcated - successive splitting into 2smaller branches

alveoli have enormous surface area (100 m2when inhaling),and are the site of O2transfer to blood (about 300 million in

an adult human)

Factors affecting air pollutant effectsGases: primary force driving gaseous air pollutants intorespiratory system is DIFFUSION: conc. of gas in tissues


11/16

Respiratory Physiology

Common respiratory ailments


asthma: muscle spasms of bronchiole walls resulting inshortness of breath (usually the result of an allergic reaction)

chronic bronchitis: when the cells lining the bronchi andbronchioles are inflamed and damaged. This causes a buildup ofmucus, coughing and shortness of breath

edema: when cells of airways or alveoli are damaged so that theybecome more permeable, and therefore release intracellular fluidinto airways. When excessive fluids accumulates, then it blocksairways and prevent gas exchange

emphysema: irreversible damage to alveoli and alveolar sacs,causing increased dilation of air spaces (as a compensatorymechanism), loss of lung elasticity, and shortness of breath

fibrosis: lysosomal enzymes released from macrophages (cellsinvolved in immune response) which then digest the macrophageitself and releases the particle eliciting the immune response...theparticle is then engulfed by another macrophage and the samething happens, leading to an increase in the number offibroblasts (which are involved in the production of fibrousconnective tissue)


12/16

Air pollutant and their effects

Outdoor air pollutants


1. ozone - damages alveoli, disrupts membranescauses swelling and rupture of capillary endothelium (cells liningcapillaries in alveoli sacs), resulting in severe edema that can befatalcauses cancer through production of highly reactive intermediatecompoundsincreases sensitivity to broncho-constrictive agents, such as

histamine and allergens

2. nitrogen dioxide - low water solubility, so damage is in lowerrespiratory tract

direct cellular damage via peroxidation of membranes, whichcauses cell membranes to lose structure and function, edemaand then cell death

3. sulfur dioxide:

causes thickening of the mucous layer in trachea (5-fold), whichreduces the effectiveness of the cilia to move gunk out of lungscauses constriction of the bronchioles due to direct effects onsmooth muscle

4. carbon monoxide:source: burning of any carbon-containing compounds, fromwoodstove smoke to cigarettesCO binds to hemoglobin, the molecule in blood responsible forcarrying oxygen to tissues. The binding affinity is stronger thanthat for oxygen, so it displaces the oxygen.causes headaches, dizziness, nausea, brain damage, collapse,coma and death


13/16

Air pollutant and their effects (con't)

Chemicals of greatest concern (EPA) in indoor air pollution


1. cigarette smoke - contains several compounds that causerespiratory ailments and heart disease

see nitrogen dioxide, carbon monoxide, etc.nicotine causes paralysis of cilia, prevent transport of mucus andother gunk out of lungsincreases susceptibility to all respiratory ailments

2. formaldehyde - found in furniture stuffing and the adhesives used inplywood, particleboard and paneling

affects 20 million Americans annuallygas that irritates the eyes, nose, throat, lungs and skin

high water solubility confines effects to upper parts ofrespiratory systemsimilar response as that to sulfur dioxide

causes nasal cancer in rodentscauses nausea and dizziness

if formaldehyde were introduced to the market today, it would bebanned from widespread use in industry and consumer goodsbecause of its carcinogenic properties

3. asbestos - found in pipe insulation and vinyl ceiling and floor tilesbecause they are fire resistant and provide excellent thermalinsulation: the magic mineral...(seeRom, W.N., Environmental andOccupational Medicine)

3,000 uses and 200,000 miles of asbestos-cement pipes carrydrinking water and other materials in USover 50% of autopsies show asbestos fibers in lungstiny silicon fibers of different shapes (hydrated silicon oxides) -amphibole fibers are the most dangerous


14/16

Air pollutant and their effects (con't)

Chemicals of greatest concern (EPA) in indoor air pollution


3. asbestos (con't)asbestosis - chronic respiratory impairment in which ischaracterized by fibrosismacrophages try to ingest lodged fibers, lysosomal membranesdegrade, macrophages die. Fibroblasts are then activated todeposit collagen (or scar tissue), and then alveolar walls become

thickened (preventing gas exchange) and lung loses elasticity.cancer of the lung and chest cavity lining (mesothelioma): noproof that asbestos directly causes DNA mutation, buthypothesis is that particles- are chemically active and serve as acarrier for carcinogens into the lung), and cancer in lungs

4. radon-222 gas: from decay uranium-238 in soil, granite, phosphateor shale rocks

problem when drawn into buildings through cracks, etc. andaccumulates because of inadequate ventilationwhen radon-222 or decay products are inhaled, lungs get a doseof radiation, can result in lung cancersafe indoor concentration of radon-222 is somewhere between 4and 20 picocuries (a picocurie is a trillionth of the radioactivityreleased by 1 gram of radium)

between 50,000 and 5 million homes in US fall in this range

5. fiberglass - see asbestos


15/16

Indoor Air Pollution (IAP)

Risk assessment and sick building syndrome


Considered HIGH-RISK health problem for humans (risk analysts)IAP considered #1 on list of 18 sources of cancer risk (EPA1990)Why?

11 common pollutants are ~2-5x higher indoors thanoutdoors (EPA)

People spend 70-98% of their time insidesusceptible subpopulations: smokers, infants andchildren, sick, elderly, pregnant women, people withrespiratory or heart problems, and factory workers

Sick building syndrome: when 20% of occupants sufferpersistent symptoms that disappear when they go outside

affects 17% of 4 million commercial buildings in USdizziness, headaches, nausea, burning eyes, chronic fatigue,flu-like symptomsusually in buildings with insufficient air exchange whenchemicals are released from new furniture and carpeting

mineral fibers from ceiling tiles and air condition ductliningelectrostatic fields of computer monitors attract thesefibers

$100 billion annually in absenteeism reduced productivity

and health care


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Air Pollution

Occupational Exposure Rates


PollutantNo. of workers

exposedOccupational activity

asbestos 250000mining and

manufacturing

arsenic 1500000pesticide, pigment,

glass and alloyproduction

coal dust 200000 coal mining

nitrogen oxides 1500000silo filling, welding,

explosive

manufacturing

ozone 380000welding,

deodorizing, flourbleaching

sulfur dioxide 5000000

bleaching,fumigation,

refrigeration and

chem.manufacturing

anthropogenic disruption of nutrient cycles - air pollution

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