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Chemistry of the Earth‘s Atmosphere

Richard Wayne and Ann Holloway examine the basic principles of our atmosphere’s chemical make-up and the role and impact of biological processes.

About 99 percent of our atmosphere consists of nitrogen (78 percent) and oxygen (21 percent). The remainder is a mixture of literally hundreds of different chemical species, mostly gases, the most important of which are shown in the table. Particles of aerosols and cloud droplets are also present. Despite their tiny absolute abundances, they not only have obvious meteorological effects, but also provide surfaces and droplets on and in which important chemical reactions can occur.

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Richard Wayne and Ann Holloway examine the basic principles of our atmosphere’s chemical make-up and the role and impact of biological processes.

About 99 percent of our atmosphere consists of nitrogen (78 percent) and oxygen (21 percent). The remainder is a mixture of literally hundreds of different chemical species, mostly gases, the most important of which are shown in the table. Particles of aerosols and cloud droplets are also present. Despite their tiny absolute abundances, they not only have obvious meteorological effects, but also provide surfaces and droplets on and in which important chemical reactions can occur.

The gases themselves turn out to be a rather peculiar mixture, because several of them are combustible in the presence of oxygen. Chemists would say the mixture is not at equilibrium. The Sun provides the energy required to drive this disequilibrium, but it’s the living organisms on our planet that bring about the remarkable separation of the chemical species. Our lifeless neighbours Venus and Mars possess atmospheres made up of 95 percent or more carbon dioxide. The early atmospheres of all three planets were probably very similar, but life (and liquid water) on Earth have resulted in almost all of our carbon dioxide being converted into carbonate rocks or transformed into buried fossil carbon. Man is determined to get the carbon out of the ground again and let it react with oxygen, thus leading to the small but inexorable rise in atmospheric carbon dioxide levels that’s behind present-day worries about global warming.

Chemical make-up

Where do the myriad constituents of the atmosphere come from? We probably lost the planet’s original remnant solar atmosphere. Quite early on, however, gases trapped within the planet, in particular nitrogen, carbon dioxide and water, began to escape to form an early atmosphere. Continuing emissions from the planet’s interior, most spectacularly from volcanoes, yield a rich variety of gases and particles. Living organisms generate enormous quantities of gaseous material, a subject we examine later in this article. Mankind is a special case, because we deliberately extract Nature’s products and even manufacture gaseous chemicals not found in Nature at all: chlorofluorocarbons (CFCs) are a well-known example of the latter. Added to these inputs of new material to the atmosphere, chemical changes resulting from reactions between the species already there are continually transforming their identity and concentrations. Some of these reactions convert the gases to new particles that, if they remain suspended in the atmosphere, are aerosols. Balancing the input are sink processes such as deposition to solid surfaces (and possible reaction with them) and dissolution in cloud droplets that are subsequently ‘rained out’.

Atmospheric layers

One exceptionally important minor atmospheric constituent exemplifies the formation of new species by chemical reaction. Ozone (O3) results from the addition of oxygen atoms (O) to oxygen molecules (O2). Ozone itself absorbs solar ultraviolet radiation and warms the atmosphere. Most of the ozone is found in a ‘layer’ at altitudes of about 25km, and so causes warming in that region. Simple physics dictates that temperatures fall with increasing altitude. The colder (and thus relatively denser) air lies on top of the warmer portion, and convection currents are set up that are the source of winds and ‘the weather’. The atmosphere is turbulent – we are in the region called the troposphere (from the Greek for ‘turning’). But when ozone warming is encountered, the temperature trends are reversed (an inversion) and a region of vertical stability is found. The atmosphere can be regarded as ‘layered’ (Greek stratos) and the region is the stratosphere. Roughly 90 percent of the atmospheric ozone is found in the stratosphere, with most of the remaining 10 percent in the troposphere. Figure 1 shows in diagrammatic form where these two atmospheric regions lie.

(Copyright P. Biggs)

Ozone

Quite apart from the dramatic effects it has on the temperature structure and meteorology of the atmosphere, stratospheric ozone has another very important role to play. Because it absorbs ultraviolet radiation it is a key part of the atmospheric system that shields living organisms on the surface of the planet from lethal wavelengths in the Sun’s rays. For this reason, there has been great concern about the damaging effects of CFCs on the ozone layer, as demonstrated most strikingly in the polar (especially Antarctic) ‘ozone holes’ that were discovered in about 1978. Ozone in the troposphere is also vital, but for a different reason. It is responsible, by one mechanism or another, for the initiation of much of the oxidation that leads to the removal of other trace gases entering the atmosphere that could otherwise build up and have noxious or toxic effects. This ‘cleansing’ of the atmosphere is, indeed, an important aspect of atmospheric chemistry.

The biological contribution

The biological generation of atmospheric constituents is shown most clearly in the case of oxygen, one of the ‘major’ gases. Photosynthesis by plants is responsible for virtually all the oxygen in our atmosphere. Carbon dioxide (CO2) and water (H2O) are converted by plants’ chlorophyll-based system into oxygen and carbohydrate. Before the evolution of plants, micro-organisms such as cyanobacteria were responsible for the gradual build-up of oxygen.

The natural cycle

At present, all the oxygen in the atmosphere passes through a cycle of consumption and regeneration in a period of about 3,000 years, astonishingly short on geological timescales. We can now illustrate the closure of the oxidation cycle by invoking another microbiological process. One source (out of many) of atmospheric methane is the fermentation of carbohydrate (grass) in the stomachs of ruminant animals such as cows, as illustrated in Figure 2. Despite cows’ protestations to the contrary, they release significant quantities of methane to the atmosphere from each extremity of their anatomy. It’s said to be dangerous to strike a match near either end of a cow! Once in the atmosphere, the methane is oxidised in stages, with the end products being CO2 and H2O. The H2O becomes rain, and it and the CO2 are converted by photosynthesis in the grass to carbohydrate. The cow eats the grass, the carbohydrate ferments, and so the cycle begins again.

(Copyright R.P. Wayne)

Oxygen

What purposes do the atmospheric constituents serve? Oxygen might be regarded by organisms that respire, including us, as essential to life. However, there are plenty of anaerobic microbes that do as well, or better, without oxygen. On the other hand, oxygen is certainly an essential component of the oxidising chemical system that ultimately degrades many other chemical species released to the atmosphere. Perhaps most importantly, it’s the precursor of ozone. Oxygen and ozone, between them, remove from the Sun’s rays the shorter wavelength radiation that would make life impossible on the planet’s surface.

Carbon dioxide

Carbon dioxide is the ‘feedstock’ for photosynthesis; without it neither carbohydrates (and thus fossil fuels) nor oxygen could be formed. Carbon dioxide and water vapour are greenhouse gases – they ‘trap’ solar infrared radiation and act as a blanket to keep our planet warmer than it would be otherwise. With too little carbon dioxide, Earth would be much colder than it is, water would be frozen, and life would not evolve. Of course, the corollary is that too much carbon dioxide might lead to too much warming, a truly serious concern in the 21st century.

Nitrogen

The nitrogen in the atmosphere should not be regarded merely as ‘filler’. For example, it is used by bacteria in the root nodules of leguminous plants to produce nitrate ions that are plant nutrients. Some nitrogen is converted by lightning to nitrate in the atmosphere that is rained out, again fertilising the ground.

The right balance

The quantitative composition of the atmosphere seems curiously ‘right’ for us. Just a little more oxygen and all vegetation would burn up. Just a little less or more carbon dioxide and it would be too cold or hot (for us, at least), and so on. Many of the trace gases found in the atmosphere influence aspects of the relatively hospitable environment in which we and all living creatures exist. Greenhouse gases control temperatures, and have conspired to keep some water liquid ever since life first emerged. Different trace gases (methane, oxides of nitrogen, halogens) can modulate the concentration of stratospheric ozone and thus modify the spectrum of solar radiation reaching us. Yet others such as dimethylsulfide are believed to be able to influence cloudiness, and thus the total intensity of light reaching the surface. The chemical species involved act in some way like ‘messengers’. What’s more: most are produced by the biota, and at the same time affect the living conditions of organisms. These are examples of biogeochemical feedbacks. The Gaia Hypothesis proposed by James Lovelock sees these feedbacks and interactions as so intense that the entire system of atmosphere–geology–biology is to be regarded as a single entity. Trace gases become analogous to the blood in a body: not in itself alive, but essential to the life system and for conveying information chemically around it.

Richard P. Wayne is Emeritus Professor of Chemistry at the University of Oxford. Ann M. Holloway is an Oxford chemist by background and she is now a teacher of mathematics at a secondary school. They co-authored the book Atmospheric Chemistry published by the Royal Society of Chemistry (Cambridge, 2010). ISBN 978-1-84755-807-7 Pbk. Further details can be found at www.rsc.org. The publisher has permitted us to reproduce illustrations from the book.

Economy

How Going Green Can Save A Company Money

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going green can save company money
Shutterstock Licensed Photot - By GOLFX

What is going green?

Going green means to live life in a way that is environmentally friendly for an entire population. It is the conservation of energy, water, and air. Going green means using products and resources that will not contaminate or pollute the air. It means being educated and well informed about the surroundings, and how to best protect them. It means recycling products that may not be biodegradable. Companies, as well as people, that adhere to going green can help to ensure a safer life for humanity.

The first step in going green

There are actually no step by step instructions for going green. The only requirement needed is making the decision to become environmentally conscious. It takes a caring attitude, and a willingness to make the change. It has been found that companies have improved their profit margins by going green. They have saved money on many of the frivolous things they they thought were a necessity. Besides saving money, companies are operating more efficiently than before going green. Companies have become aware of their ecological responsibility by pursuing the knowledge needed to make decisions that would change lifestyles and help sustain the earth’s natural resources for present and future generations.

Making needed changes within the company

After making the decision to go green, there are several things that can be changed in the workplace. A good place to start would be conserving energy used by electrical appliances. First, turning off the computer will save over the long run. Just letting it sleep still uses energy overnight. Turn off all other appliances like coffee maker, or anything that plugs in. Pull the socket from the outlet to stop unnecessary energy loss. Appliances continue to use electricity although they are switched off, and not unplugged. Get in the habit of turning off the lights whenever you leave a room. Change to fluorescent light bulbs, and lighting throughout the building. Have any leaks sealed on the premises to avoid the escape of heat or air.

Reducing the common paper waste

paper waste

Shutterstock Licensed Photo – By Yury Zap

Modern technologies and state of the art equipment, and tools have almost eliminated the use of paper in the office. Instead of sending out newsletters, brochures, written memos and reminders, you can now do all of these and more by technology while saving on the use of paper. Send out digital documents and emails to communicate with staff and other employees. By using this virtual bookkeeping technique, you will save a bundle on paper. When it is necessary to use paper for printing purposes or other services, choose the already recycled paper. It is smartly labeled and easy to find in any office supply store. It is called the Post Consumer Waste paper, or PCW paper. This will show that your company is dedicated to the preservation of natural resources. By using PCW paper, everyone helps to save the trees which provides and emits many important nutrients into the atmosphere.

Make money by spreading the word

Companies realize that consumers like to buy, or invest in whatever the latest trend may be. They also cater to companies that are doing great things for the quality of life of all people. People want to know that the companies that they cater to are doing their part for the environment and ecology. By going green, you can tell consumers of your experiences with helping them and communities be eco-friendly. This is a sound public relations technique to bring revenue to your brand. Boost the impact that your company makes on the environment. Go green, save and make money while essentially preserving what is normally taken for granted. The benefits of having a green company are enormous for consumers as well as the companies that engage in the process.

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Energy

5 Easy Things You Can Do to Make Your Home More Sustainable

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sustainable homes
Shutterstock Licensed Photot - By Diyana Dimitrova

Increasing your home’s energy efficiency is one of the smartest moves you can make as a homeowner. It will lower your bills, increase the resale value of your property, and help minimize our planet’s fast-approaching climate crisis. While major home retrofits can seem daunting, there are plenty of quick and cost-effective ways to start reducing your carbon footprint today. Here are five easy projects to make your home more sustainable.

1. Weather stripping

If you’re looking to make your home more energy efficient, an energy audit is a highly recommended first step. This will reveal where your home is lacking in regards to sustainability suggests the best plan of attack.

Some form of weather stripping is nearly always advised because it is so easy and inexpensive yet can yield such transformative results. The audit will provide information about air leaks which you can couple with your own knowledge of your home’s ventilation needs to develop a strategic plan.

Make sure you choose the appropriate type of weather stripping for each location in your home. Areas that receive a lot of wear and tear, like popular doorways, are best served by slightly more expensive vinyl or metal options. Immobile cracks or infrequently opened windows can be treated with inexpensive foams or caulking. Depending on the age and quality of your home, the resulting energy savings can be as much as 20 percent.

2. Programmable thermostats

Programmable thermostats

Shutterstock Licensed Photo – By Olivier Le Moal

Programmable thermostats have tremendous potential to save money and minimize unnecessary energy usage. About 45 percent of a home’s energy is earmarked for heating and cooling needs with a large fraction of that wasted on unoccupied spaces. Programmable thermostats can automatically lower the heat overnight or shut off the air conditioning when you go to work.

Every degree Fahrenheit you lower the thermostat equates to 1 percent less energy use, which amounts to considerable savings over the course of a year. When used correctly, programmable thermostats reduce heating and cooling bills by 10 to 30 percent. Of course, the same result can be achieved by manually adjusting your thermostats to coincide with your activities, just make sure you remember to do it!

3. Low-flow water hardware

With the current focus on carbon emissions and climate change, we typically equate environmental stability to lower energy use, but fresh water shortage is an equal threat. Installing low-flow hardware for toilets and showers, particularly in drought prone areas, is an inexpensive and easy way to cut water consumption by 50 percent and save as much as $145 per year.

Older toilets use up to 6 gallons of water per flush, the equivalent of an astounding 20.1 gallons per person each day. This makes them the biggest consumer of indoor water. New low-flow toilets are standardized at 1.6 gallons per flush and can save more than 20,000 gallons a year in a 4-member household.

Similarly, low-flow shower heads can decrease water consumption by 40 percent or more while also lowering water heating bills and reducing CO2 emissions. Unlike early versions, new low-flow models are equipped with excellent pressure technology so your shower will be no less satisfying.

4. Energy efficient light bulbs

An average household dedicates about 5 percent of its energy use to lighting, but this value is dropping thanks to new lighting technology. Incandescent bulbs are quickly becoming a thing of the past. These inefficient light sources give off 90 percent of their energy as heat which is not only impractical from a lighting standpoint, but also raises energy bills even further during hot weather.

New LED and compact fluorescent options are far more efficient and longer lasting. Though the upfront costs are higher, the long term environmental and financial benefits are well worth it. Energy efficient light bulbs use as much as 80 percent less energy than traditional incandescent and last 3 to 25 times longer producing savings of about $6 per year per bulb.

5. Installing solar panels

Adding solar panels may not be the easiest, or least expensive, sustainability upgrade for your home, but it will certainly have the greatest impact on both your energy bills and your environmental footprint. Installing solar panels can run about $15,000 – $20,000 upfront, though a number of government incentives are bringing these numbers down. Alternatively, panels can also be leased for a much lower initial investment.

Once operational, a solar system saves about $600 per year over the course of its 25 to 30-year lifespan, and this figure will grow as energy prices rise. Solar installations require little to no maintenance and increase the value of your home.

From an environmental standpoint, the average five-kilowatt residential system can reduce household CO2 emissions by 15,000 pounds every year. Using your solar system to power an electric vehicle is the ultimate sustainable solution serving to reduce total CO2 emissions by as much as 70%!

These days, being environmentally responsible is the hallmark of a good global citizen and it need not require major sacrifices in regards to your lifestyle or your wallet. In fact, increasing your home’s sustainability is apt to make your residence more livable and save you money in the long run. The five projects listed here are just a few of the easy ways to reduce both your environmental footprint and your energy bills. So, give one or more of them a try; with a small budget and a little know-how, there is no reason you can’t start today.

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