Wednesday, October 21, 2015
Acid rain has been an environmental buzzword since the 1980s, even though it started falling from the sky and eating through lawn furniture and ornaments as early as the 1950s. Although common acid rain isn’t acidic enough to burn skin, the effects of acid rain on plant growth can be dramatic. If you live in an acid rain-prone area, read on to learn about safeguarding plants from acid rain.
What is Acid Rain?
Acid rain forms when sulfur dioxide and nitrogen oxide react with chemicals like water, oxygen and carbon dioxide in the atmosphere to form sulfuric acid and nitric acid. Water containing these acidic compounds falls back to the earth as rain, harming plants and other immobile objects below. Although the acid from acid rain is weak, normally no more acidic than vinegar, it can seriously alter the environment, damaging plants and aquatic ecosystems.
Does Acid Rain Kill Plants?
This is a straightforward question with a not very straightEnforward answer. Acid rain and plant damage go hand in hand in areas prone to this type of pollution, but the changes to a plant’s environment and tissues are gradual. Eventually, a plant exposed to acid rain will die, but unless your plants are incredibly sensitive, the acid rain unusually potent and frequent or you’re a very bad gardener, the damage is not fatal.
The way that acid rain damages plants is very subtle. Over time, the acidic water alters the pH of the soil where your plants are growing, binding and dissolving vital minerals and carrying them away. As the soil pH falls, your plants will suffer increasingly obvious symptoms, including yellowing between the veins on their leaves.
Rain that falls on leaves can eat away the outer waxy layer of tissue that protects the plant from drying out, leading to the destruction of the chloroplasts that drive photosynthesis. When a lot of leaves are damaged at once, your plant may become very stressed and attract a host of pests and diseases organisms.
Safeguarding Plants from Acid Rain
The best way to protect plants from acid rain is to prevent rain from falling on them, but with larger trees and shrubs this may be impossible. In fact, many experts recommend planting more tender specimens under large trees to protect them from damage. Where trees aren’t available, moving these delicate plants to gazebos or covered porches will do. When all else fails, some thick plastic draped over stakes surrounding the plant can hold off acid damage, provided that you place and remove the covers promptly.
The soil is another matter entirely. If you live in an area where acid rain is common, soil testing every six to 12 months is a good idea. Frequent soil tests will alert you to problems in the soil so you can add extra minerals, nutrients or lime when necessary. Staying one step ahead of acid rain is vital to keeping your plants healthy and happy.
Depending on where you live, maybe you've heard of acid rain. Now, acid rain is not pure acid falling from the sky, but rather it is rainfall or atmospheric moisture that has been mixed with elements and gases that have caused the moisture to become more acidic than normal. Pure water has a pH of 7, and, generally, rainfall is somewhat on the acidic side (a bit less than 6). But, acid rain can have a pH of about 5.0-5.5, and can even be in the 4 range in the northeastern United States, where there are a lot of industries and cars.
Causes of acid rain
Acidic precipitation can be caused by natural (volcanoes) and man-made activities, such as from cars and in the generation of electricity. The precursors, or chemical forerunners, of acid rain formation result from both natural sources, such as volcanoes and decaying vegetation, and man-made sources, primarily emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) resulting from fossil fuel combustion. The burning of fossil fuels (coal and oil) by power-production companies and industries releases sulfur into the air that combines with oxygen to form sulfur dioxide (SO2). Exhausts from cars cause the formation of nitrogen oxides in the air. From these gases, airborne sulfuric acid (H2SO4) and nitric acid (HNO3) can be formed and be dissolved in the water vapor in the air. Although acid-rain gases may originate in urban areas, they are often carried for hundreds of miles in the atmosphere by winds into rural areas. That is why forests and lakes in the countryside can be harmed by acid rain that originates in cities.
Effects of acid rain
The environment can generally adapt to a certain amount of acid rain. Often soil is slightly basic (due to naturally occurring limestone, which has a pH of greater than 7). Because bases counteract acids, these soils tend to balance out some of the acid rain's acidity. But in areas, such as some of the Rocky Mountains and parts of the northwestern and southeastern United States, where limestone does not naturally occur in the soil, acid rain can harm the environment.
Some fish and animals, such as frogs, have a hard time adapting to and reproducing in an acidic environment. Many plants, such as evergreen trees, are damaged by acid rain and acid fog. I've seen some of the acid-rain damage to the evergreen forests in the Black Forest of Germany. Much of the Black Forest was indeed black because so much of the green pine needles had been destroyed, leaving only the black trunks and limbs! You also might notice how acid rain has eaten away the stone in some cities' buildings and stone artwork.
Geographic distribution of acid rain
Acidity in rain is measured by collecting samples of rain and measuring its pH. To find the distribution of rain acidity, weather conditions are monitored and rain samples are collected at sites all over the country. The areas of greatest acidity (lowest pH values) are located in the Northeastern United States. This pattern of high acidity is caused by the large number of cities, the dense population, and the concentration of power and industrial plants in the Northeast. In addition, the prevailing wind direction brings storms and pollution to the Northeast from the Midwest, and dust from the soil and rocks in the Northeastern United States is less likely to neutralize acidity in the rain.
Acid rain and stone
When you hear or read in the media about the effects of acid rain, you are usually told about the lakes, fish, and trees in New England and Canada. However, we are becoming aware of an additional concern: many of our historic buildings and monuments are located in the areas of highest acidity. In Europe, where buildings are much older and pollution levels have been ten times greater than in the United States, there is a growing awareness that pollution and acid rain are accelerating the deterioration of buildings and monuments.
Stone weathers (deteriorates) as part of the normal geologic cycle through natural chemical, physical, and biological processes when it is exposed to the environment. This weathering process, over hundreds of millions of years, turned the Appalachian Mountains from towering peaks as high as the Rockies to the rounded knobs we see today. Our concern is that air pollution, particularly in urban areas, may be accelerating the normal, natural rate of stone deterioration, so that we may prematurely lose buildings and sculptures of historic or cultural value.
What about buildings?
Many buildings and monuments are made of stone, and many buildings use stone for decorative trim. Granite is now the most widely used stone for buildings, monuments, and bridges. Limestone is the second most used building stone. It was widely used before Portland cement became available in the early 19th century because of its uniform color and texture and because it could be easily carved. Sandstone from local sources was commonly used in the Northeastern United States, especially before 1900. Nationwide, marble is used much less often than the other stone types, but it has been used for many buildings and monuments of historical significance. Because of their composition, some stones are more likely to be damaged by acidic deposition than others. Granite is primarily composed of silicate minerals, like feldspar and quartz, which are resistant to acid attack. Sandstone is also primarily composed of silica and is thus resistant. A few sandstones are less resistant because they contain a carbonate cement that dissolves readily in weak acid. Limestone and marble are primarily composed of the mineral calcite (calcium carbonate), which dissolves readily in weak acid; in fact, this characteristic is often used to identify the mineral calcite.
How does acid precipitation affect marble and limestone buildings?
Acid precipitation affects stone primarily in two ways: dissolution and alteration. When sulfurous, sulfuric, and nitric acids in polluted air react with the calcite in marble and limestone, the calcite dissolves. In exposed areas of buildings and statues, we see roughened surfaces, removal of material, and loss of carved details. Stone surface material may be lost all over or only in spots that are more reactive.
You might expect that sheltered areas of stone buildings and monuments would not be affected by acid precipitation. However, sheltered areas on limestone and marble buildings and monuments show blackened crusts that have spalled (peeled) off in some places, revealing crumbling stone beneath. This black crust is primarily composed of gypsum, a mineral that forms from the reaction between calcite, water, and sulfuric acid. Gypsum is soluble in water; although it can form anywhere on carbonate stone surfaces that are exposed to sulfur dioxide gas (SO2), it is usually washed away. It remains only on protected surfaces that are not directly washed by the rain. Gypsum is white, but the crystals form networks that trap particles of dirt and pollutants, so the crust looks black. Eventually the black crusts blister and spall off, revealing crumbling stone.
Tuesday, February 3, 2015
Geothermal energy is a renewable energy source that derives from the heat of the earth’s core and has long been used for a variety of purposes. In this article you will find various geothermal energy facts surrounding what this energy source is, how we can use it and the history behind it.
Some interesting facts about geothermal energy
These facts provide a good top-level overview of geothermal energy:
Geothermal energy has been around since the earth formed and is a renewable energy source.
The term “Geothermal” derives from the Greek words “geo” (meaning earth” and “therme” (meaning heat).
Geothermal activity provides the energy behind volcanoes, hot springs and geysers.
Civilisations have been using hot springs heated by geothermal activity for thousands of years.
Geothermal energy is greater along the fault lines in the earth’s crust as liquid rock (magma) can be found closer to the earth’s surface, thus providing more geothermal activity.
The best place for geothermal activity is along the “Ring of Fire”.
Unlike solar, wind and other renewable energy sources, geothermal energy doesn’t rely on solar activity.
Facts specific to geothermal power
These facts are specific to how we can produce electricity from geothermal energy:
The process of generating geothermal power has been in existence for over a hundred years and was first tested in Italy by Piero Ginori Conti in 1903.
Today, geothermal power is only responsible for a small amount of global electricity capacity.
Modern geothermal power generation is performed at either dry steam, flash steam or binary cycle power stations.
Geothermal power can be highly price competitive.
Geothermal power can only be generated cost-effectively in specific areas with enough geothermal activity.
Geothermal power is considered clean and highly efficient.
Geothermal power stations do still produce greenhouse gases but on a very small scale when compared with fossil fuel power stations.
Geothermal power stations are often small and have minimal visual impact on the surrounding environment.
Geothermal power stations can work both day and night with a high uptime.
There are over 40 geothermal power plants in the USA alone with many more dotted across the globe.
In the USA, California has the highest geothermal power capacity and generates just over 80% of the nations geothermal power supply.
Iceland has the world’s most efficient geothermal power stations and is responsible for a large percentage of global geothermal electricity production.
Iceland produces around 26% of its electricity supply from geothermal energy.
New Zealand generates around 13% of its electricity from geothermal activity.
Other countries that generate significant levels of geothermal power are; Indonesia, Italy, Japan, Kenya, Mexico and Philippines.
Facts specific to geothermal heating
These facts are specific to how we can use geothermal energy for heating purposes:
Geothermal energy can also be used to provide heating for homes. This technique makes use of ground source heat instead of the geothermal activity described above.
Geothermal heat pumps can be used to produce part or all of a buildings hot water supply.
Geothermal heat pumps work by burying hundreds of meters of water pipes under ground so that the water absorbs the heat from the earth.
Geothermal Energy is created and stored inside the Earth.
The Geothermal Energy stored inside our Earth, was produced when our planet was formed millions of years ago and from the decay of minerals.
The core of the Earth is extremely hot. Hotter than you could ever imagine, sometimes reaching more than 4000 degrees Celsius! The heat from the core travels to the surface of the Earth.
The word 'geothermal' comes from Greek words: Geo means Earth and Thermal (Thermos) means heat. You will have heard the word 'thermal' many times as it's often used in reference to heat and insulating heat e.g. thermal gloves or a thermal flask which are devices that store heat similar to the geothermal energy of planet Earth.
Geothermal Energy from the Earth can be used in many ways in pumping systems and power stations where the energy can be converted to electricity.
One of the heat sources from the Earth is mineral water which can be heated by geothermal energy. For centuries, people have bathed in natural hot water springs.
Hot water can be run from geothermal power plants. When the water runs underground, it can help to melt ice away. This is particularly useful in countries such as Iceland.
Geothermal Energy has many benefits over many other types of energy and fossil fuels. This is a clean type of energy which doesn't pump harmful chemicals into our atmosphere when it is processed into electricity.
Although geothermal energy is not used as much as it could be, the future is looking brighter as it is being used more and more across the world. The more geothermal energy we can use, the less use of fossil fuels there will be. Fossil fuels can damage our planet as they are rich in carbon and release harmful chemicals when they are burned.
Geothermal Energy is reliable as it is constantly produced. Not all energies are the same, some are inconsistent such as solar power which relies on the sun. During night hours or poor weather conditions, solar energy cannot be received in all places on Earth.
Geothermal is a renewable energy source unlike many other types of energy. Renewable means it can be replenished and it isn't going to run out.
Electricity can be generated from geothermal energy at different types of power plants including binary cycle, dry steam and flash steam power plants.
Flash steam power plants usually function through the use of turbines to generate electricity. This type of power plant uses hot water from the ground which produces steam when it is released from the reservoir to the power plant. Steam is produced due to a decrease in temperature and it is used to power the turbine.
The oldest type of geothermal power plant runs on dry steam. It uses steam without water droplets (the molecules are in gas state not liquid).
Binary cycle power plants, like flash steam power plants, also uses steam from water to power turbines in order to generate electricity. However, the water is not as hot as the water used in flash steam power plants.