Particulate pollution, acid rain, ozone layer, 

global warming

Particulates pollution

Particulates (PM) are tiny subdivisions of solid matter suspended in a gas or liquid. In contrast, aerosol refers to particles and/or liquid droplets and the gas together. The notation PM₁₀ is used to describe particles of 10 micrometers or less and PM_2.5 represents particles less than 2.5 micrometers in aerodynamic diameter.

·         Wind-blown mineral dust

·         Sea salt

·         Elemental carbon

·         Black carbon or soot (smog consists of sulphur dioxide, nitrogen oxides, carbon monoxide, mineral dust, organic matter, and elemental carbon)

Effects

Effects on vegetation:-Particulate matter can clog stomatal openings of plants and interfere with photosynthesis functions. stunting of growth or mortality in some plant species.

Climate effects: Climate effects can be extremely catastrophic; sulfur dioxide ejected from the eruption of Huaynaputina probably caused the Russian famine of 1601 - 1603, leading to the deaths of two million.

The "direct effect" is caused by the fact that the particles scatter and absorb solar and infrared radiation in the atmosphere called Global dimming, a gradual reduction in the amount of global direct irradiance at the Earth's surface, has partially counteracted global warming.

The addition of PM into the atmosphere causes the water to condense on to the particles. This results in more, but smaller droplets in the clouds, which increases the cloud albedo. In addition to increasing the albedo, this effect tends to decrease the chance of precipitation. If precipitation is suppressed, this results in excess water remaining in the atmosphere. Atmospheric soot directly absorb solar radiation, which heats the atmosphere and cools the surface. Climate effects inevitably lead to health effects, which are listed above, but consist mainly of respiratory problems, cardiovascular disease, and premature death

Acid rain

Deposition of wet (rain, snow, sleet, fog, cloudwater, and dew) and dry (acidifying particles and gases) acidic components called  "Acid rain". Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen oxides which react with the water molecules in the atmosphere to produce acids.

It can have harmful effects on plants, aquatic animals, and infrastructure. Nitrogen oxides can also be produced naturally by lightning strikes and sulfur dioxide is produced by volcanic eruptions. The chemicals found in acid rain can cause paint to peel, corrosion of steel structures like bridges and stone statues to begin to appear old and worn down, which reduces their value and beauty.

pH readings in rain and fog water of well below 2.4 have been reported in industrialized areas. Industrial acid rain is a substantial problem in China and Russia and areas down-wind from them. These areas all burn sulfur-containing coal to generate heat and electricity. Example is the low pH of rain (compared to the local emissions) which falls in Scandinavia.

·            Wet deposition- (rain, snow, and so on) removes acids from the atmosphere and delivers it to the Earth's surface. This can result from the deposition of acids produced in the raindrops or by the precipitation removing the acids either in clouds or below clouds. Wet removal of both gases and aerosols are both of importance for wet deposition.

·            Dry deposition in the absence of precipitation occurs when particles and gases stick to the ground, plants or other surfaces (20 to 60% of total acid deposition.

Sources

Natural source

·          Volcanoes. Crater of Poás Volcano create- acid rain and fog with acidity 2 of pH

·         Biological processes - wetlands, and in the oceans. (dimethyl sulfide)

·         Nitric acid in rainwater is an important source of fixed nitrogen for plant life, and is also produced by electrical activity in the atmosphere such as lightning.

·         Acidic deposits - glacial ice

Man made sources

·         Electricity generation, factories, and motor vehicles. Coal power plants are one of the most polluting.

 

Effects

·                     In surface waters pH less than 5 prevents hatching of eggs and  kill adult fish. Biodiversity is reduced.

·                     Soil biology and chemistry-Microbes are unable to tolerate changes to low pHs and are killed. The enzymes of these microbes are denatured by the acid. The hydronium ions of acid rain also mobilize toxins such as aluminium, and leach away essential nutrients and minerals such as magnesium. Soil chemistry can be dramatically changed when base cations, such as calcium and magnesium, are leached by acid rain thereby affecting sensitive species, such as sugar maple (Acer saccharum).

Forests and other vegetation

Adverse effects may be indirectly related to acid rain, like the acid's effects on soil or high concentration of gaseous precursors to acid rain. High altitude forests are especially vulnerable as they are often surrounded by clouds and fog which are more acidic than rain.

Other plants can also be damaged by acid rain, but the effect on food crops is minimized by the application of lime and fertilizers to replace lost nutrients. In cultivated areas, limestone may also be added to increase the ability of the soil to keep the pH stable, but this tactic is largely unusable in the case of wilderness lands. When calcium is leached from the needles of red spruce, these trees become less cold tolerant and exhibit winter injury and even death.

Human health effects

Acid rain does not directly affect human health. The acid in the rainwater is too dilute to have direct adverse effects. However, the particulates responsible for acid rain (sulfur dioxide and nitrogen oxides) do have an adverse effect. Increased amounts of fine particulate matter in the air do contribute to heart and lung problems including asthma and bronchitis.

Other adverse effects

Acid rain can also damage buildings and historic monuments, especially those made of rocks such as limestone and marble containing large amounts of calcium carbonate. Acids in the rain react with the calcium compounds in the stones to create gypsum, which then flakes off.

CaCO₃ (s) + H₂SO₄ (aq) CaSO₄ (aq) + CO₂ (g) + H₂O (l)

The effects of this are commonly seen on old gravestones, where acid rain can cause the inscriptions to become completely illegible. Acid rain also increases the corrosion rate of metals, in particular iron, steel, copper and bronze.

Ozone layer

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O₃). This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth (sunburn; excessive exposure can also cause genetic damage, resulting in problems such as skin cancer). It is mainly located in the lower portion of the stratosphere from approximately 30 to 40 kilometres above Earth, though the thickness varies seasonally and geographically. The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. The "Dobson unit", a convenient measure of the columnar density of ozone overhead, is named in his honor.

Ozone in the Earth's stratosphere is created by ultraviolet light striking oxygen molecules containing two oxygen atoms (O₂), splitting them into individual oxygen atoms (atomic oxygen); the atomic oxygen then combines with unbroken O₂ to create ozone, O₃. The ozone molecule is also unstable (although, in the stratosphere, long-lived) and when ultraviolet light hits ozone it splits into a molecule of O₂ and an atom of atomic oxygen, a continuing process called the ozone-oxygen cycle, thus creating an ozone layer in the stratosphere, the region from about 10 to 50 kilometres above Earth's surface. About 90% of the ozone in our atmosphere is contained in the stratosphere. Ozone concentrations are greatest between about 20 and 40 kilometres, where they range from about 2 to 8 parts per million.

The ozone layer can be depleted by free radical catalysts, including nitric oxide (NO), nitrous oxide (N₂O), hydroxyl (OH), atomic chlorine (Cl), and atomic bromine (Br). While there are natural sources for all of these species, the concentrations of chlorine and bromine have increased markedly in recent years due to the release of large quantities of man-made organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons. These highly stable compounds are capable of surviving the rise to the stratosphere, where Cl and Br radicals are liberated by the action of ultraviolet light. Each radical is then free to initiate and catalyze a chain reaction capable of breaking down over 100,000 ozone molecules.

Approximately 5% of the Earth's surface, around the north and south poles, much larger seasonal declines have been seen, and are described as ozone holes.

Global warming

The instrumental temperature record shows that the average global surface temperature increased by 0.74 °C (1.33 °F) during the 20th century. Climate model projections by the Intergovernmental Panel on Climate Change (IPCC) indicate that during the 21st century the global surface temperature is likely to rise a further 1.5 to 1.9 °C (2.7 to 3.4 °F) for their lowest emissions scenario and 3.4 to 6.1 °C (6.1 to 11 °F) for their highest.

An increase in global temperature will cause sea levels to rise and will change the amount and pattern of precipitation, and a probable expansion of subtropical deserts. Warming is expected to be strongest in the Arctic and would be associated with continuing retreat of glaciers, permafrost and sea ice. Other likely effects of the warming include more frequent occurrence of extreme weather events including heatwaves, droughts and heavy rainfall events, species extinctions due to shifting temperature regimes, and changes in agricultural yields. Warming and related changes will vary from region to region around the globe, though the nature of these regional changes is uncertain. In a 4 °C world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon which human livelihoods depend would not be preserved.

Greenhouse gases

The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in the atmosphere warm a planet's lower atmosphere and surface. It was proposed by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896.

Naturally occurring amounts of greenhouse gases have a mean warming effect of about 33 °C (59 °F). The major greenhouse gases are water vapor, which causes about 36–70 per cent of the greenhouse effect; carbon dioxide (CO₂), which causes 9–26 per cent; methane (CH₄), which causes 4–9 per cent; and ozone (O₃), which causes 3–7 per cent. Clouds also affect the radiation balance through cloud forcings similar to greenhouse gases.

Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from CO₂, methane, troposphere ozone, CFCs and nitrous oxide. The concentrations of CO₂ and methane have increased by 36% and 148% respectively since 1750. These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores. Less direct geological evidence indicates that CO₂ values higher than this were last seen about 20 million years ago. Fossil fuel burning has produced about three-quarters of the increase in CO₂ from human activity over the past 20 years. The rest of this increase is caused mostly by changes in land-use, particularly deforestation.