Presentation on theme: "Human Impact on the Biosphere. Presented by Mr. Bijay Ghimire."— Presentation transcript:
Human Impact on the Biosphere
Presented by Mr. Bijay Ghimire
Pollutants are substances with which ecosystems have no prior evolutionary experience and therefore cannot deal with them zCarbon oxidesCO, CO 2 zSulfur oxidesSO 2, SO 3 zNitrogen oxidesNO, NO 2, N 2 O zVolatile organicCH 4, CFC’s, compounds zPhotochemical oxidantsOzone, H 2 O 2 zSuspended particles Dust, soot, lead, pesticides Each day 700,000 metric tons of pollutants are dumped into the atmosphere in the US alone
cooler air cool air SMOG Thermal Inversions are when weather conditions trap a layer of cool, dense air under a layer of warm air. Thermal inversions can trap pollutants close to the ground cooler air cool air warm air cool air warm inversion air cool air Normal air circulation pattern Air pollutants trapped under a thermal inversion layer
cooler air cool air SMOG zIndustrial smog - is gray air found in industrial cities that burn fossil fuel (usually in cities that are cold and wet) zPhotochemical smog - is brown air found in large cities in warm climates, the key culprit is nitric oxide.
Acid Rain Burning coal & metal smelting produces sulfur dioxides Burning fossil fuels, vehicles and fertilizers result in nitrogen oxides Tiny particles of these oxides can fall to the earth in 2 forms: - Dry acid deposition - Acid Rain
Average acidities of precipitation in the United States in 1998 Major coal-burning power and industrial plants > – – – – – – –4.47 >4.3
Ultrafine particlesFine particlesLarge particles metallurgical dust, fumes photochemical smog tobacco smoke carbon black combustion sea salt oil smoke paint pigments cement dust fly ash insecticide dust coal dust pollen milled flour Average particle diameter (µm) Ultrafine particles reach alveoli in lungs and contribute to respiratory disorders. High concentrations can cause lung cancer.
Greening Sudbury CNN 1997
Ozone Thinning - Why is the loss of the Ozone Scary? Ozone protect us from UV radiation! Ozone in the lower stratosphere absorbs most of the UV radiation from the sun. - the thinning of the ozone layer has produced a seasonal ozone “hole” over Antartica - in response, skin cancer has increased, cataracts may increase, and phytoplankton may be affected Chlorofluorocarbons (CFC) seem to be the cause - one chlorine atom can convert 10,000 ozone molecules to oxygen.
ice clouds Ozone Thinning - Top 1979, Middle 1991 Bottom Lowest ozone values are in magenta and purple.
South America Antarctica Seasonal ozone thinning above Antarctica in the fall of 2001
Ozone Thinning zAntarctica zCFC’s zRefrigerators and air conditioning solvents zPlastic foams Each Cl can convert 10,000 O 3 to O 2 CFC’s in Air Light rays Free Cl O3O3 O2O2 + ClO
Ozone Destruction animation…
Where to put Solid Wastes? Where to produce food? In NATURAL ecosystems, one organism’s waste serves as resources for others. Paper products and non-returnable bottles and cans are perhaps our biggest problem. - each week 500,000 trees end up as Sunday newspapers in US - if every reader recycled just 1 out of 10 papers, we could save 25 million trees a year - recycling paper could reduce air born pollutants released by paper manufacturing by 95% and requires 30 to 50% less energy than making new paper We face a challenge to move from a “throw-away” society to one of conservation and re-use. Land fills leak and threaten groundwater. What if we burn wastes instead? - greater amount of air pollution
6% 8% 11% 10% 14% 51% arid lands tropical forest cultivated grazed forests, arid lands ice, snow, deserts, mountains Where to put Solid Wastes? Where to produce food? Converting Marginal Lands for Agriculture - Almost 21% of land is used for Agriculture; another 28% is available but may not be worth the cost - the green revolution has increased crop yields but uses many times more energy and mineral resources - a growing human population is moving into marginal lands to meet our increasing needs
At one time tropical forest cloaked regions that were collectively 2X the size of Europe and home of 50-90% of all land dwelling species. In 4 decades humans have destroyed more than half of the forests and most of the species. Each year another 34 million acres is logged over = to leveling 34 city blocks every minute.
Deforestation - the removal of all trees from large tracts of land for logging agriculture and grazing. In Shifting cultivation (slash-and-burn agriculture) trees are cut, the land used for a few growing seasons and then abandoned as fertility plummets.
Deforestation Forest are watersheds; they control erosion, flooding, & sediment buildup in rivers and lakes. Deforestation can - reduce fertility - change rainfall patterns - increase temperatures - increase carbon dioxide (CO 2 ) Clearing large tracts of tropical forest may have global repercussions, such as altering: - rates of evaporation - rates of transpiration - runoff of nutrients and rainfall - photosynthetic activity rates.
Why are we destroying our forests? Increase demand for lumber, fuel and other forest products as well as for cropland and grazing land When vegetation cover gets stripped away, the exposed soil becomes vulnerable to leaching of nutrients and erosion In logged area, annual precipitation declines and rain swiftly drains from the exposed nutrient poor soil. -desert like conditions might prevail
Desertification is the conversion of grasslands and croplands to desert-like conditions Desertification, also applies when agricultural productivity drops by 10% or more. At least 200,000 sq. kilometers are being converted annually - overgrazing of livestock on marginal lands is the main cause of large scale desertification - prolong droughts accelerate the process
A Global Water Crisis Most of the earth’s water is too salty for human consumption or for agriculture. Desalination (removal of salt from sea water) processes are available and can be used when absolutely necessary. However, desalinization is not cost effective in most locales and it uses valuable fuel reserves to provide the energy for the desalination equipment, also produces mounds of salt. Consequences of heavy irrigation - - large scale agriculture account for nearly 2/3 of the human population’s use of fresh water (“piped in water” - high in mineral salts) - salt buildup (salinization) of the soil and waterlogging can results - withdrawl of underground water causes water tables to drop
A Global Water Crisis Water Pollution - amplifies the problem of water scarcity Causes ? - radioactive materials - human wastes - insecticides - herbicides - chemicals - heat
The Coming Water Wars Water, not oil, may become the most important fluid of the 21 st century. National, regional and global policies for water usage and water rights have yet to be developed. In the past decade, 33 nations have engaged in conflicts over reductions in water flow, pollution, and silt buildup By restricting water flow, countries upstream may attempt to influence political behavior in countries downstream. By building dams and irrigation systems at the headwaters of the Tigris and Euphrates rivers, Turkey could stop the water flow in Syria and Iraq for as long as eight months “to regulate their political behavior”.
Fossil Fuels are limited resources, extraction costs are increasing and atmospheric levels of carbon, nitrogen and sulfur oxides are also increasing.
A Question of Energy Inputs Increases in human population and extravagant life-styles has increased energy consumption. Extraction and use of abundant reserves of oil shale and coal are not “environmentally attractive” - environmental cost Valdez tanker ~ 11 million gallons of oil spilled near the Alaskan coastline Coal burning is primary source of air pollution contributing to acid rain and greenhouse effect. Extensive strip mining of coal reduces the land available for agriculture, grazing, and wildlife; restoration difficult
Coal 25% Oil 37% Natural gas 25% Biomass 3% Hydropower, geothermal, solar 7% Nuclear power 5% Coal 25% Oil 26% Biomass 35% Natural gas 7% Hydropower, geothermal, solar 6% Nuclear power 1% Developed CountriesDeveloping Countries
A Question of Energy Inputs Nuclear Energy - with nuclear energy, the net energy produced is low and the cost is high compared with coal-burning plants - meltdowns may release large amounts of radioactivity to the environment - nuclear waste is so radioactive that it must be isolated for 10,000 years.
April 26, 1986 — Chernobyl in Ukraine Nuclear fuel burned for 10 days right through a 6-foot thick steel and gravel barrier Distribution of radioactive fallout within 2 weeks of the meltdown - Reached Europe Made crops & live stock unfit for consumption
April 27April 30 May 2May 6
After soviet union's breakup, some underpaid workers of a Russian nuclear power plant have been selling fuel elements on the black market. The buyers? Developing nations that want to produce nuclear weapons - possibly deliver them to the hand of terrorist organization
Alternative Energy Sources (1) Solar-Hydrogen Energy Solar-hydrogen energy is an attractive technology b/c it depends on a renewable energy source … The SUN! Photovoltaric cells produce an electric current that splits water into oxygen and hydrogen gas (H 2 ) which can be used directly as fuel or to produce electricity
In these cells generated almost 4 million kwatt hours of net electricity in the US
Alternative Energy Sources (2) Wind Energy - where wind travels faster than 7.5 meters per sec, wind turbines are cost-effective producers of energy - b/c winds do not blow on a regular schedule, wind turbines cannot be the exclusive source of energy
Alternative Energy Sources (3) Fusion Power - temperatures like those on the sun cause atomic nuclei to fuse and release energy -fusion power on earth is possible but many obstacles make the technology a distant possibility -Researchers confine a heated gas of two isotopes of hydrogen in magnetic fields, then bombard it with lasers. The fuel (hydrogen) implodes and energy is released.
“ If we make the transition to an energy- efficient solar-hydrogen age, we can say good-bye to smog, oil spills, acid rain, and nuclear energy, and perhaps to global warming. The reason is simple. As Hydrogen burns in air, it reacts with oxygen gas to produce water vapor – not a bad thing to have coming out of tailpipes, chimneys, and smokestacks.” -G. Tyler Miller, Jr. (Environmental Scientist)