LL--99Acid rain and Heat Island effectAcid rain and Heat Island effect

Air Pollution and ControlAir Pollution and Control

(Elective(Elective--I)I)

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What is Acid Rain• When the droplets of water of the rain, snow

or fog contain acidic component, it is called acid rain. Normally the pure water has the pH 7.

• pH 7 indicates the neutral, not acidic neither basic. pH is measure of acidic and alkaline nature of a solution.

• Naturally normal rain water has the pH value 5.6. When this value goes under 5.6 then it is considered as acid rain.

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Acid rain Effected Forests

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What Causes Acid RainHuman causes:•• Sulfur dioxide that is used in power Sulfur dioxide that is used in power

plant.plant.

•• Nitrogen oxide that is used in Nitrogen oxide that is used in automobiles.automobiles.

• CO2 and Ozone those are produced by burning of different types of fuel.

• CO released from vehicles.

• CFC gas that is used in refrigerators and air conditioning systems.

Natural causes:

• Forest Fires.

• Volcanic eruption.

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Effects of Acid Rain

• Acidify the water of lake, stream, river.

• Destroys the forest.

• Kills the living things in the water.

• Causes health problems if affected vegetables are Consumed by us.

• Destroys non-replicable buildings and statues etc.

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Steps than can reduce Acid Rain

• Minimum use of electricity which reduces load on power plants

• Desulphurization and denitrification of stack gases.

• Lessening uses of air conditioners.

• Reducing the uses of the fossil fuel.

• The amount of use of motor vehicle should be lessened.

• Try to use ethanol, propane or natural gas rather than other fuels.

• Addition of lime to acidified water bodies

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Most affected Areas by Acid Rain

• Northeastern area of united states

• Southeastern area of Canada

• Central Europe

• Scandinavia

• India and

• China

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Acid rain is a threat for us as well as for the ecosystem of the nature. So, each of us should be careful about it and also try to lessen the factors that causes it.

Acid Rain video clip

Heat Island Effect

• During night, cool air comes in contact with heated vertical building surfaces and roads.

• Gets warmed and moves up. It carries all the pollutional load of the city.

• As it moves up ,cools down and moves down.

• The cycle continues.

• Because of this temperature of city increases during night hours as compared to rural area

• This cycle is broken by strong winds.

What is Heat Island?• As urban areas develop, changes occur in

their landscape. Buildings, roads, and other infrastructure replace open land and vegetation. Surfaces that were once permeable and moist become impermeable and dry.

• These changes cause urban regions to become warmer than their rural surroundings, forming an "island" of higher temperatures in the landscape.

• The term "heat island" describes built up areas that are hotter than nearby rural areas. The annual mean air temperature of a city with 1 million people or more can be 1–3°C warmer than its surroundings. In the evening, the difference can be as high as (12°C).

• Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality, and water quality.

• Communities can take a number of common-sense measures to reduce the effects of summertime heat islands.

Effects-1) Increased Energy Consumption

• Elevated summertime temperatures in cities increase energy demand for cooling. Research shows that electricity demand for cooling increases 1.5–2.0% for every 0.6°C increase in air temperatures, starting from 20 to 25°C, suggesting that 5–10% of community-wide demand for electricity is used to compensate for the heat island effect.

• Urban heat islands increase overall electricity demand, as well as peak demand, which generally occurs on hot hot summer weekday afternoonssummer weekday afternoons, when offices and homes are running cooling systems, lights, and appliances.

2) Elevated Emissions of Air Pollutants and Greenhouse Gases

• As described above, urban heat islands raise demand for electrical energy in summer. Companies that supply electricity typically rely on fossil fuel power plants to meet much of this demand, which in turn leads to an increase in air pollutant and greenhouse gas emissions.

• The primary pollutants from power plants include sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter (PM), carbon monoxide (CO), and mercury (Hg). These pollutants are harmful to human health and also contribute to complex air quality problems such as the formation of ground-level ozone (smog), fine particulate matter, and acid rain.

• Increased use of fossil-fuel-powered plants also increases emissions of greenhouse gases, such as carbon dioxide (CO2), which contribute to global climate change.

• Elevated temperatures can directly increase the rate of ground-level ozone formation. Ground-level ozone is formed when NOxand volatile organic compounds (VOCs) react in the presence of sunlight and hot weather.

3) Compromised Human Health and Comfort3) Compromised Human Health and Comfort• Increased daytime temperatures, reduced night-time

cooling, and higher air pollution levels associated with urban heat islands can affect human health by contributing to general discomfort, respiratory difficulties, heat cramps and exhaustion, non-fatal heat stroke, and heat-related mortality.

• Heat islands can also cause the impact of heat waves, which are periods of abnormally hot, and often humid, weather. Sensitive populations, such as children, older adults, and those with existing health conditions, are at particular risk from these events.

• Excessive heat events, or abrupt and dramatic temperature increases, are particularly dangerous and can result in above-average rates of mortality.

4) Impaired Water Quality• High pavement and rooftop surface temperatures can

heat storm water runoff. Tests have shown that pavements that are 38°C can elevate initial rainwater temperature from roughly 21ºC to over 35ºC. This heated storm water generally becomes runoff, which drains into storm sewers and raises water temperatures as it is released into streams, rivers, ponds, and lakes.

• Water temperature affects all aspects of aquatic life, especially the metabolism and reproduction of many aquatic species. Rapid temperature changes in aquatic ecosystems resulting from warm storm water runoff can be particularly stressful, even fatal to aquatic life.

Mitigation Measures

1. Increasing tree and vegetative cover;

2. Creating green roofs (also called "rooftop gardens" or "eco-roofs");

3. Installing cool—mainly reflective—roofs; and

4. Using cool pavements.

• Trees, vegetation, and green roofs can reduce heating and cooling energy use and associated air pollution and greenhouse gas emissions, remove air pollutants, sequester and store carbon, help lower the risk of heat-related illnesses and deaths, improve storm water control and water quality, reduce noise levels, create habitats, improve aesthetic qualities, and increase property values.

• Cool roofs can lower cooling energy use, peak electricity demand, air pollution and greenhouse gas emissions, heat-related incidents, and solid waste generation due to less frequent re-roofing.

• Cool pavements can indirectly help reduce energy consumption, air pollution, and greenhouse gas emissions. Depending on the technology used, cool pavements can improve storm water management and water quality, increase surface durability, enhance night-time illumination, and reduce noise.

Heat island effect video clip -1

Heat island effect video clip-2

Objective questions

Q1. Acid rain has pH value less than _________.

Q2. _______________________ are island of higher temperatures in the landscape.

Q3. Heat Island occurs in ________ areas.

Q4. Cool roofs reduces ____________ demand

Q5. Acid rain deteriorates common building material, ____________.

Prof S S Jahagirdar,NKOCET 34

Theory QuestionsQ1. What is ‘Acid rain’? Explain its causes,

effects and remedial measures.

Q2. Explain causes, effects and remedies of ‘Heat Island Effect’.

Prof S S Jahagirdar,NKOCET 35