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Atmospheric gas changes, and their effects life

Atmospheric gas changes, and their effects life



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I was curious how life on Earth, or an Earth-like planet, would be effected by changes in the gases which make up our atmosphere.

Assuming there is a similar level of oxygen in an atmosphere, could other gases be reduced or even replaced and still be able to maintain life as we know it?

Not really biology, but if the following could be kept in mind too that would be amazing:

[To give some context, I would like to ask how a sky could be light blue with a purplish hue, which supports some life larger than what we see on Earth, but still capable of supporting life which we find on Earth.

I am assuming a slightly higher percentage of oxygen is needed, but what other gases which are none lethal, but give a purplish hue?]

Thank you to all who take the time to give an answer, very much appreciated!


The Earth is blue (at least the non-land mass) because of the light our atmosphere refracts from the sun. A planets color is primarily determined by distance from sun, not from gas components.

Most gas does not refract light. Therefore a planet's gaseous composition can not be identified based on color.

To elaborate on your primary question, gas composition balance is essential to most life on Earth. Carbon dioxide, for instance, is responsible for photosynthesis occurring in plants. Different concentrations will affects photosynthetic rates. Another example is that CO2 levels, CO levels, and hexa-fluoro-carbons affect the amount of heat trapped in this planet.

Gas composition is highly delicate and must stay in balance to preserve life on Earth.


Climate changes and photosynthesis

This paper is a review. According to the latest data issued by the UN, global warming causes danger to human health and well-being, as well as to animals and plants. As global warming is mainly caused by anthropogenic activities, it was considered that emission of the so-called greenhouse gases should be reduced and in some cases even prohibited. Plants are more easily exposed to biological damage than any other living organisms. The paper deals with the biochemical measures that will increase plants' biological potential, in particular, their photosynthetic and energy opportunities and, therefore, will contribute to drought resistance and will prevent increase of carbon dioxide concentrations in the atmosphere.

Solar energy is environmentally friendly and its conversion to energy of chemical substances is carried out only by photosynthesis – effective mechanism characteristic of plants. However, microorganism photosynthesis occurs more frequently than higher plant photosynthesis. More than half of photosynthesis taking place on the earth surface occurs in single-celled organisms, especially algae, in particular, diatomic organisms.


The Greenhouse Effect and our Planet

The greenhouse effect happens when certain gases, which are known as greenhouse gases, accumulate in Earth&rsquos atmosphere. Greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and fluorinated gases.

Biology, Ecology, Earth Science, Geography, Human Geography

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The greenhouse effect happens when certain gases, which are known as greenhouse gases, accumulate in Earth&rsquos atmosphere. Greenhouse gases include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and fluorinated gases.

Greenhouse gases allow the sun&rsquos light to shine onto Earth&rsquos surface, and then the gases, such as ozone, trap the heat that reflects back from the surface inside Earth&rsquos atmosphere. The gases act like the glass walls of a greenhouse&mdashthus the name, greenhouse gas.

According to scientists, the average temperature of Earth would drop from 14˚C (57˚F) to as low as &ndash18˚C (&ndash0.4˚F), without the greenhouse effect.

Some greenhouse gases come from natural sources, for example, evaporation adds water vapor to the atmosphere. Animals and plants release carbon dioxide when they respire, or breathe. Methane is released naturally from decomposition. There is evidence that suggests methane is released in low-oxygen environments, such as swamps or landfills. Volcanoes&mdashboth on land and under the ocean&mdashrelease greenhouse gases, so periods of high volcanic activity tend to be warmer.

Since the Industrial Revolution of the late 1700s and early 1800s, people have been releasing larger quantities of greenhouse gases into the atmosphere. That amount has skyrocketed in the past century. Greenhouse gas emissions increased 70 percent between 1970 and 2004. Emissions of CO2, rose by about 80 percent during that time.

The amount of CO2 in the atmosphere far exceeds the naturally occurring range seen during the last 650,000 years.

Most of the CO2 that people put into the atmosphere comes from burning fossil fuels. Cars, trucks, trains, and planes all burn fossil fuels. Many electric power plants do as well. Another way humans release CO2 into the atmosphere is by cutting down forests, because trees contain large amounts of carbon.


People add methane to the atmosphere through livestock farming, landfills, and fossil fuel production such as coal mining and natural gas processing. Nitrous oxide comes from agriculture and fossil fuel burning. Fluorinated gases include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). They are produced during the manufacturing of refrigeration and cooling products and through aerosols.


All of these human activities add greenhouse gases to the atmosphere. As the level of these gases rises, so does the temperature of Earth. The rise in Earth&rsquos average temperature contributed to by human activity is known as global warming.


The Greenhouse Effect and Climate Change

Even slight increases in average global temperatures can have huge effects.

Perhaps the biggest, most obvious effect is that glaciers and ice caps melt faster than usual. The meltwater drains into the oceans, causing sea levels to rise.

Glaciers and ice caps cover about 10 percent of the world&rsquos landmasses. They hold between 70 and 75 percent of the world&rsquos freshwater. If all of this ice melted, sea levels would rise by about 70 meters (230 feet).

The Intergovernmental Panel on Climate Change states that the global sea level rose about 1.8 millimeters (0.07 inches) per year from 1961 to 1993, and about 3.1 millimeters (0.12 inches) per year since 1993.

Rising sea levels cause flooding in coastal cities, which could displace millions of people in low-lying areas such as Bangladesh, the U.S. state of Florida, and the Netherlands.

Millions more people in countries like Bolivia, Peru, and India depend on glacial meltwater for drinking, irrigation, and hydroelectric power. Rapid loss of these glaciers would devastate those countries.

Greenhouse gas emissions affect more than just temperature. Another effect involves changes in precipitation, such as rain and snow.

Over the course of the 20th century, precipitation increased in eastern parts of North and South America, northern Europe, and northern and central Asia. However, it has decreased in parts of Africa, the Mediterranean, and southern Asia.

As climates change, so do the habitats for living things. Animals that are adapted to a certain climate may become threatened. Many human societies depend on predictable rain patterns in order to grow specific crops for food, clothing, and trade. If the climate of an area changes, the people who live there may no longer be able to grow the crops they depend on for survival. Some scientists also worry that tropical diseases will expand their ranges into what are now more temperate regions if the temperatures of those areas increase.

Most climate scientists agree that we must reduce the amount of greenhouse gases released into the atmosphere. Ways to do this, include:

  • driving less, using public transportation, carpooling, walking, or riding a bike.
  • flying less&mdashairplanes produce huge amounts of greenhouse gas emissions.
  • reducing, reusing, and recycling.
  • planting a tree&mdashtrees absorb carbon dioxide, keeping it out of the atmosphere.
  • using less electricity.
  • eating less meat&mdashcows are one of the biggest methane producers.
  • supporting alternative energy sources that don&rsquot burn fossil fuels.

Photograph by James P. Blair

Manmade Gas

Chlorofluorocarbons (CFCs) are the only greenhouse gases not created by nature. They are created through refrigeration and aerosol cans.

CFCs, used mostly as refrigerants, are chemicals that were developed in the late 19th century and came into wide use in the mid-20th century.

Other greenhouse gases, such as carbon dioxide, are emitted by human activity, at an unnatural and unsustainable level, but the molecules do occur naturally in the Earth's atmosphere.

container of liquid material under high pressure. When released through a small opening, the liquid becomes a spray or foam.

the art and science of cultivating land for growing crops (farming) or raising livestock (ranching).

layers of gases surrounding a planet or other celestial body.

chemical element with the symbol C, which forms the basis of all known life.

greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels.

chemical compound mostly used in refrigerants and flame-retardants. Some CFCs have destructive effects on the ozone layer.

all weather conditions for a given location over a period of time.

dark, solid fossil fuel mined from the earth.

edge of land along the sea or other large body of water.

set of physical phenomena associated with the presence and flow of electric charge.

conditions that surround and influence an organism or community.

process by which liquid water becomes water vapor.

overflow of a body of water onto land.

to add or combine with the element fluorine (F).

ecosystem filled with trees and underbrush.

coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.

state of matter with no fixed shape that will fill any container uniformly. Gas molecules are in constant, random motion.

mass of ice that moves slowly over land.

increase in the average temperature of the Earth's air and oceans.

building, often made of glass or other clear material, used to help plants grow.

phenomenon where gases allow sunlight to enter Earth's atmosphere but make it difficult for heat to escape.

gas in the atmosphere, such as carbon dioxide, methane, water vapor, and ozone, that absorbs solar heat reflected by the surface of the Earth, warming the atmosphere.

environment where an organism lives throughout the year or for shorter periods of time.

greenhouse gas often used as an industrial cooling material.

usable energy generated by moving water converted to electricity.

greenhouse gas often used as an industrial cooling material.

area of fewer than 50,000 square kilometers (19,000 square miles) covered by ice.

change in economic and social activities, beginning in the 18th century, brought by the replacement of hand tools with machinery and mass production.

watering land, usually for agriculture, by artificial means.

site where garbage is layered with dirt and other absorbing material to prevent contamination of the surrounding land or water.

animals raised for sale and profit.

freshwater that comes from melting snow or ice.

chemical compound that is the basic ingredient of natural gas.

having to do with very small organisms.

process of extracting ore from the Earth.

smallest physical unit of a substance, consisting of two or more atoms linked together.

type of fossil fuel made up mostly of the gas methane.

greenhouse gas used in medicine and the manufacture of rockets. Also known as laughing gas or happy gas.

large body of salt water that covers most of the Earth.

form of oxygen that absorbs ultraviolet radiation.

industrial facility for the generation of electric energy.

all forms in which water falls to Earth from the atmosphere.

methods of movement that are available to all community members for a fee, and which follow a fixed route and schedule: buses, subways, trains and ferries.


Atmospheric Pollutants: Sources and Effects

Pollutants are emitted to the atmosphere as a result of natural processes as well as due to human activity. The sources of some common pollutant are tabulated in Table 2.2. It should be pointed out here that the list is not a complete one. Natural sources of emission are oceans, volcanoes, swamps, biologically decaying organic matter, desert and semi-desert areas, forests and forest fires, lightning, etc.

Human activities, which give rise to air-borne pollutants, are domestic, transport, agricultural and industrial. The major industrial sources are fossil fuel combustors, mines, quarries, metallurgical and metal processing industries, chemical processing industries food, biochemical and pharmaceutical industries.

Effects of Atmospheric Pollutants:

Air pollutants affect ecosystems in various ways. The effects are manifested by bringing about some changes in an ecosystem directly or indirectly.

The overall effects may be classified as hereunder:

I. Effects on atmospheric properties

II. Effects on vegetation’s

IV. Effects on human beings

V. Effects on land and water bodies

I. Effects on Atmospheric Properties:

The atmospheric properties of the troposphere get affected considerably due to the presence of pollutants and those of the stratosphere to some extent. The properties of the other layers (mesosphere and thermosphere) remain almost unaffected, as pollutants are virtually not present there.

A. Tropospheric Effects:

The gaseous and particulate pollutants which are directly emitted into the troposphere due to natural as well as human activity affect the following properties of the troposphere:

(ii) Fog and haze formation,

(iv) Solar radiation incidence,

(vi) Wind direction and velocity.

When a beam of light passes through air its intensity decreases due to absorption and scattering by the molecules of gases present in air as well as by the suspended particles (particularly by the sub- micron sized ones) present in air.

The major constituents of air, namely, oxygen, and nitrogen do not absorb or scatter light, but the pollutant gas molecules and suspended particles (both liquid and solid) do. The extent of absorption and scattering is dependent on the specific pollutants present and their concentration.

Decreased intensity of light as a result of absorption and scattering decreases visibility. Nitrogen dioxide and aerosols strongly absorb visible light in the blue-green wave length range and produce a yellow-brown haze. Ozone absorbs at wave lengths below 3200 A.

Hygroscopic particles present in air picks up moisture from air as the humidity increase and consequently reduce the visibility further. At a humidity of 70% R. H. and less the effect is not that marked, but above 70% R. H. the effect is considerable.

Visibility being dependent on the concentration of the gaseous pollutants and suspended particles is influenced by the wind speed. With the increase in wind speed up to about 24 kmph the visibility improves as the pollutant concentration decreases due to dispersion. But at higher wind speed, due to scouring effect the concentration of solid particles (dust) increases in air. This leads to more scattering, and consequently visibility becomes poorer.

(ii) Fog and Haze Formation:

Polluted air having a large number of suspended particles is conducive to fog formation under favourable condition. Normally air is unsaturated with water vapour. When air temperature decreases (at night) it may become saturated and with further decrease in temperature air may become supersaturated with water vapour. Under such condition a suspension of fine water droplets in air, that is, a fog is formed. Fine suspended solid particles present in air serve as condensation nuclei.

If the number of particles be large, the water droplets formed would be small in size and the fog would be more stable. Such a fog would be more effective in scattering light and thereby reduce visibility. If fewer suspended particles be present in air the water droplets would be larger in size, hence the resulting fog would be less stable.

When a large number of tiny solid particles are present in air, they absorb and scatter light. This results in reduced visibility. Such a situation is termed as haze. Fine solid particles may get suspended in air due to high wind velocity and or due to emission from industrial units as well as due to aerosol formation.

When the relative humidity (RH) in air becomes sufficiently high the nucleating particles get ‘activated’ and condensation of water vapour in atmosphere is initiated. The mechanism by which the cloud condensation nuclei (CCN) act is not known however, it is known that hygroscopic and water soluble particles are more effective as CCN. The sources of CCN may be natural processes as well as industrial operations. The CCN emitted from industrial sources supplement the natural CCN.

Once the process of condensation is initiated further development would depend on the number and size of the droplets in a cloud. If there are a larger number of smaller droplets, those would not agglomerate easily and hence there would be less precipitation. If the number of CCN be relatively fewer, the size of droplets produced would be larger which would coalesce more readily and thereby would cause more precipitation. The precipitation may be either dry (snow) or wet (rain) depending upon the ambient air temperature.

(iv) Solar Radiation Incidence:

Pollutants present in air interfere with the incidence of solar radiation on the earth’s surface by scattering and absorbing the incoming radiation. Solid and liquid particles generally scatter the incoming radiation whereas the gaseous pollutants and aerosols absorb radiation.

Absorption occurs at specific wave lengths depending upon the pollutants present. For example, nitrogen dioxide absorbs radiation in the wave length range of 3600-4000 A, whereas ozone absorbs at wave lengths below 3200 A.

Due to scattering and absorption of incoming solar radiation by air-borne pollutants less energy would reach the earth’s surface resulting in lower surface temperature. The energy absorbed by gaseous pollutants is released to the atmosphere as heat which causes rise in tropospheric temperature.

Cloud cover also reduces incidence of solar radiation on the earth’s Surface.

During the daytime solar radiation reaches the earth’s surface, a part of which is absorbed. Subsequently the ground transfers a portion of the absorbed radiation to the tropospheric air by re- radiation and convection. At higher altitude of the troposphere the flux due to re-radiation and convection is less.

Consequently the air temperature is less. The variation of temperature with altitude in the troposphere is also due to the decrease in atmospheric pressure with altitude. This decrease is due to adiabatic expansion of ‘air packets’ as they move upward because of convection.

The intensity of solar radiation at a place in the ground level depends on the angle of incidence, which in turn depends on the time of the day (relative to sun rise) as well as on the season. On a cloudless day and the air free from pollutants, the intensity is maximum at mid-day when the sun is overhead. When pollutants are present at a higher concentration in air, and there is cloud cover, the solar intensity is less. Variation of solar intensity results in changing the normal tropospheric temperature profile.

The ground receives solar radiation and re-radiates a part of it during the daytime but at night it re-radiates only. Hence the ground temperature decreases gradually after sunset and after some point of time it becomes less than that of air above it. This situation is termed as ‘inversion’.

Normally after sunrise the ground starts receiving solar energy and its temperature increases gradually, which results in the disappearance of the inversion condition. However, when pollutants are present in air at higher concentration the state of inversion may continue for a longer period even after sunrise because of lesser incidence of solar radiation. In severely polluted atmosphere the inversion may continue for days together.

Vertical convective movement of air in the troposphere occurs due to its negative temperature gradient. Such movement helps in dispersing the pollutants. The factors mentioned earlier affects the ‘normal’ tropospheric temperature gradient and thereby interferes with the pollutant dispersion process.

The tropospheric temperature profile patterns under different atmospheric conditions are shown in Fig. 2.2. It should be noted here that the atmospheric condition is termed as ‘stable’ when it resists the vertical convective movement.

The lapse rate is nearly identical to the dry adiabatic lapse rate. Such a condition prevails on days of moderate solar incidence. When some vertical air movement takes place the situation is referred to as neutral stable.

B. Super-Adiabatic:

The lapse sate is more than that of the dry adiabatic. On days of strong solar incidence such a condition is observed.

The lapse rate is less than that of the dry adiabatic. It happens on days of slight solar incidence. When very little vertical air movement takes place the condition is termed as slightly stable.

Air temperature increases with height up to some altitude and then decreases. Such a situation may occur at late night. Stable inversion occurs when there is no vertical air movement below the break. When the tropospheric condition is neutral, a rising ‘packet’ of air would undergo cooling due to adiabatic expansion and its temperature would be the same as that of the ambient air at that height.

As there would be no difference in density between the rising packet and the ambient air, further vertical motion of the packet would neither be suppressed nor be enhanced.

Under super adiabatic condition a rising packet of air even after cooling due to adiabatic expansion would attain a temperature higher than that of the ambient air at that height. Consequently, it would move further up. Such movement promotes vertical convection.

Under sub-adiabatic or inversion condition as a ‘packet’ of air moves upward due to turbulence, it becomes cooler and denser (because of adiabatic expansion) than the ambient air at that height and hence it tends to slide back. As a result the vertical motion is impeded.

The pollutants present in air not only cause tropospheric temperature profile change but may also cause increase in the average global temperature of the lower troposphere. Some gases, such as carbon dioxide, methane, nitrogen oxides and chlorofluorocarbon (CFC) absorb ground re-radiation (the infrared portion).

With an increase in concentration of the above-mentioned pollutants in air they will trap more of the ground re-radiation and thereby cause increase in the average global temperature of the troposphere. With the rise in tropospheric temperature, the earth’s surface temperature will increase because of heat exchange between them.

This effect is somewhat similar to what happens in a glass greenhouse. In a greenhouse the ground re-radiation is prevented from escaping to the space by a glass enclosure. As a result the temperature inside a greenhouse is always higher than that of the outside. Since the gaseous pollutants mentioned earlier cause waning of the troposphere, in the same way as in a greenhouse, those gases are referred to as greenhouse gases.

Carbon dioxide, which, as such, is considered to be non-polluting, is the major contributor to the greenhouse effect. The concentration of carbon dioxide in the troposphere is the highest compared to those of the other green-house gases.

Moreover, its concentration in the troposphere has been observed to increase at the rate of 3.8 percent per decade since 1970s because of progressive uncontrolled combustion of fossil fuels by man in order to meet his ever-increasing energy need.

The situation is getting aggravated because of deforestation. In view of the above, it is now universally accepted that there is no other alternative but to reduce the emission rate of CO2 particularly from the conventional fossil fuel based power plants.

Serious efforts are presently being made to develop carbon dioxide capture and storage processes as well as processes for converting captured CO2 to algae, methanol, hydrocarbons, etc. Progressive global warming resulting from greenhouse effect is likely to bring about various changes in the biosphere, such as, change in precipitation, decrease in agricultural production and melting of some of the permanent ice packs. If some of the permanent ice packs (glaciers and polar ice) melt, then the ocean level will increase, as a result of which the low-lying coastal areas of the earth would be inundated.

In order to save the earth (the only habitat of man) from not so far away catastrophic situation, the representatives from 160 countries met in Kyoto in 1997 to frame a protocol, which is known as Kyoto Protocol. The objective of the protocol is to make an all-out effort to reduce the rate of emission of the ‘greenhouse gases’.

The target fixed is to reduce the rate of emission progressively, so that by 2012 their concentration in the atmosphere would be 5.2% less than that in 1990. However, because of non-endorsement of the protocol by some of the developed countries there is every doubt that the target would be realized.

(vi) Wind Direction and Velocity:

Wind is generally defined as air movement in the horizontal direction. Vertical movement of air is referred to as updraft or downdraft.

The factors which influence motion of air in the horizontal direction are:

(ii) The Coriolis force, and

The pressure gradient occurs mainly due to uneven rate of heating of land and ocean. Normally during the daytime the land mass gets heated quickly whereas the ocean heats up slowly. As a consequence, pressure gradient develops from ocean to land and sea breeze blows landward.

At night land cools quickly compared to the ocean and land breeze blows seaward. The wind speed depends on the magnitude of the pressure gradient, which in turn is influenced by the intensity of solar radiation, pollutant concentration in air, cloud cover and local topography.

The Coriolis force is caused by the rotation of the earth around its axis. This force deflects wind towards the right and it is proportional to the wind speed. The frictional force opposes movement of air. This force is maximum at the earth’s surface, hence the wind speed at any instant of time is the minimum at the ground level and it increases with the altitude.

The wind speed is generally measured at meteorological stations at a height of 10m. The speed at any other height is calculated using the relation.

Where Uh = wind speed at a height of h in m,

U10 = wind speed at a height of 10 m,

n = an exponent, a positive fraction, 0.5 or less. Its numerical value depends on the atmospheric stability and the local features including its relief (nature and man-made topography).

In the absence of any specific information the following values may be taken depending on the weather condition:

n = 0.2 for unstable conditions,

= 0.25 for neutral conditions, and

The wind speed may be expressed in the unit of m/s or kmph.

The meteorological stations not only report wind speed but also its direction throughout the year. Such data are often presented graphically. Both the frequency and speed of wind in all possible directions (8 to 16) are drawn to a scale normally for a period of one year. Such a diagram is termed as a wind rose. Figure 2.3 shows a typical wind rose for Kolkata City.

The length of a bar segment of a wind rose represents its frequency from a particular direction, while the width/shade of the same represents the range of wind speed from that direction. Such a diagram is accompanied by a scale for the wind speed.

From the discussion so far it is apparent that the prime factor which gives rise to wind is the pressure gradient arising out of unequal heating and cooling of land and ocean. The other factors, which influence wind speed and direction, are the weather condition, the season, the ocean current, etc.

It should be noted here that high wind speed helps to disperse particulate matter and gaseous pollutants, but too high a wind speed scours dusts (during dry season) and thereby increases the solid particle concentration in air.

Particulate matter and gaseous pollutants when present in air at a relatively higher concentration interfere with the incidence of solar radian to the ground, as a result of which the wind speed is adversely affected. This in turn retards the process of dispersal of pollutants.

II. Effects on Vegetation:

The pollutants present in the troposphere affect vegetation in three different ways:

(i) By attacking the cells of the different parts of plants,

(ii) By interacting with enzymes present in plants and

(iii) By interfering with the photosynthesis process.

The effects may be visible or invisible.

The visible injuries to plants may be acute or chronic. Acute injuries occur when plants are exposed to a higher concentration of pollutants. The cell membranes may get ruptured due to chemical actions of gaseous pollutants resulting in loss of cell content and finally cell death.

Pollutants such as SO2, O3, PAN bring about such changes. Pollutants like SO2, NH3, O3, fluorides, and PAN affect chlorophyll, which is the key component for photosynthesis. As a result the leaves wither. Abnormal growth of leaves and stems are induced by ethylene and herbicides. Chronic visible injuries occur due to prolonged and repeated exposure of plants to pollutants at a relatively low concentration.

Invisible damages are manifested in the form of reduced growth, interference with photosynthesis and related processes. Reduction in fruit yield due to attack on the reproductive structure also takes place. SO2, O3, and fluorides adversely affect the growth rate. SO2, NOx, PAN, O3, and fluorides interfere with the photosynthesis process and metabolic pathways. Fluorides, O3 and other oxidants attack the reproductive structure.

Dust particles interfere with the photosynthesis process by covering leaf surfaces and also by blocking the stomata’s. The extent of damage to vegetation in polluted atmosphere depends on the plant species, the specific pollutants present, their concentration and the duration of exposure.

The injury threshold concentrations of some common pollutants are listed in Table 2.3.

III. Effects on Animals:

Fish and domestic animals get affected when they ingest toxic chemicals and heavy metals. Domestic animals may get affected in the same way as human beings by inhaling air-borne gaseous pollutants and particles.

Heavy metals, such as arsenic, lead, molybdenum, mercury and their compounds are emitted during industrial processes, like roasting, smelting, steel making, etc. These may accumulate on vegetation and forages which when consumed by herbivores may affect them. Man may get affected by consuming milk and meat of the affected herbivores.

IV. Effects on Human Beings:

Air-borne gaseous pollutants and suspended particles affect human health and may produce various types of physiological effects. Common pollutants, such as CO, SO2, NOx, hydrocarbons and particulates are directly emitted from industrial sources, whereas, O3, PAN, and some other oxidants are produced due to secondary reactions.

Various other toxic chemicals are emitted and are present in the surroundings of the places where those chemicals are produced, used or handled. The biological/physiological effects of some of the above mentioned pollutants are briefly discussed hereunder and are summarized in Table 2.4.

(i) Effects of Carbon monoxide (CO):

CO is a colorless and odorless gas. It affects by combining with hemoglobin (Hb) in blood. Hemoglobin carries O2 from the respiratory system to the different parts of human body and removes CO2 from those places by forming unstable complexes with O2 and CO2.

The affinity of CO towards hemoglobin is more than that for oxygen. As a result when CO is breathed in, it forms a relatively more stable complex (COHb, carboxyhaemoglobin) with hemoglobin consequently the oxygen carrying and CO2 removal capacity of blood, decrease.

The level of COHb complex in the blood of a person depends on CO concentration in air as well as on the duration of exposure of an individual. If about 0.5 to 2% of the total hemoglobin is complexed with CO there would not be much effect. However, with increasing concentration of COHb in blood, progressively manifested symptoms are headache, dizziness, nausea, vomiting, and difficulty in breathing, collapse, unconsciousness and death.

The reaction between CO and hemoglobin being a reversible one when a person leaves a polluted area with a non-lethal dose of CO he breathes out CO and recovers. CO does not leave any permanent effect. The global average concentration of CO in air is about 0.1 ppmv. Its threshold limit is 50 ppmv. At a concentration of 1000 ppmv or more it is fatal.

(ii) Effects of Sulphur dioxide (SO2):

SO2 combines with water in the respiratory system to produce sulphurous acid (H2SO3) which irritates conjunctiva, upper respiratory tract and throat resulting in airway resistance. When inhaled at a concentration of 5 ppmv or more for about 10 minutes or so the pulse and breathing rate increase.

Symptoms such as nasopharyngitis and coughing develop on prolonged exposure. SO2 combined with benzo (a) pyrene (C2OH12), a product of incomplete combustion, causes pulmonary cancer. The global average concentration of so2 is 0.0002 ppmv. Its threshold limit is 2 ppmv. At a concentration level of 500 ppmv it is fatal.

(iii) Effects of NOx:

Nitric oxide (NO) and nitrogen dioxide are the major nitrogen oxides present in air. Of these two NO is less toxic. Like CO, NO combines with hemoglobin and thereby interferes with the oxygen transfer process. NO gets oxidized to NO2 which on inhalation is converted to nitrous acid (HNO2) and nitric acid (NHO3) in the lungs.

These exert toxic effects on the deep lungs and peripheral airway. At a lower concentration of NOx, the eyes, throat and lungs get irritated. Regular exposure at 10-40 ppmv concentration may cause distention of lungs and scarring of pulmonary tissues. Continued exposure at 500 ppmv or more would lead to death.

The threshold value of NO2 is 5 ppmv.

(iv) Effects of Ammonia(NH3):

NH3 is a colorless gas with a pungent odour. It is an irritant to skin, respiratory tract, mucous membranes and eyes. At higher concentrations it corrodes tissues and causes laryngeal and bronchial spasm and edema. At a concentration of about 5 ppmv it can be detected by its pungent smell.

At concentration around 150-200 ppmv it causes general discomfort and tears in the eyes. When a person is exposed to about 2000 ppmv concentration of ammonia, suffers from burns and skin blisters and progressively experiences serious edema, asphyxia and finally death.

(v) Effects of Hydrogen Sulphide (H2S):

H2S is a colorless gas with a rotten egg smell. It may cause eye irritation at a concentration of about 100 ppmv. Inhalation of H2S at a higher concentration irritates the entire respiration tract.

(vi) Effects of Chlorine (Cl2):

CI2 is a greenish yellow gas with a characteristic pungent smell. It irritates eyes, skin and the respiratory tract. At higher concentration of Cl2 one suffers from skin burns, redness of eyes, blurred vision and lung damage. At a concentration of about 1000 ppmv it becomes lethal.

(vii) Effects of Ozone(O3)

Inhalation of ozone above its normal concentration causes pulmonary inflammatory response. Exposure to ozone at a concentration of 1.5 to 2 ppmv irritates eyes, throat and lung. Continuous or intermittent exposure to ozone may cause chronic bronchitis, bronchiolitis and fibrotic changes of lungs. Ozone is a potential mutagen as it degenerates chromosome in lymphocytes. Its threshold limit value is 0-1 ppmv. Other photochemical oxidants present in polluted air, such as peroxyacetyle nitrate (PAN), peroxybenzoly nitrate cause effects similar to those of ozone.

Threshold Limit Value (TLV):

The Industrial Threshold Limit Value set by the American Conference of Governmental Industrial Hygienists (ACGIH) refer to indoor air-borne concentration of substances and represent the conditions under which it is believed that nearly all healthy adult workers may be exposed eight hours a day, five days per week without adverse effects.

Effects of Suspended Solid Particles (SSP):

Air-borne particles enter the respiratory system and get deposited in the different regions of the respiratory system depending upon their size, shape and density. The large (5 pm and more) and denser particles are deposited in the nasal region and are removed by mucous discharges. Finer and lighter particles penetrate deeper into the system.

Particles about 2 pm in size and finer enter into the lungs. Finer particles having larger external and internal surface areas (per unit mass) adsorb gaseous pollutants present in air and carry them deep inside the lungs. Particles with adsorbed pollutants cause more harm. The particles themselves may be toxic. The effects of some air-borne gaseous pollutants on human beings and their TLV are summarized in Table 2.4.

Time Weighted Average concentration for 8 hours workday and 5 days workweek.

Short Term Exposure Limit: 15 minute time weighted average which should not exceed any time during a workday.

V. Effects on Land and Water Bodies:

Particulate matter emitted from industrial units settle on land, buildings and other structures which give them a grimy look. Such deposits on land may interfere with soil fertility. Acid gases, such as CO2, NOx, SO2 react in the atmosphere and are deposited on land and water bodies either in the form of acid rain by combining with rain water or as dry salt particles.

Such acid deposition on land would adversely affect land fertility and vegetation growth. Plant nutrients and micro-nutrients present in soil would be leached away by acid rain as a result of which the affected land would not be able to support growth of various types of plants. Because of poor vegetation cover, rain water and wind will carry away the top soil layer and finally may turn the area arid.

Acid deposition on water bodies in general would affect the growth of aquatic plants and fish. However, fresh water bodies, which constitute only a very small fraction of the total hydrosphere, would be seriously affected by acid rain and salt deposits. Industrial units and human settlements located near the fresh water bodies would get affected once the water bodies would get affected due to acid rain.

VI. Effects on Materials:

Air-borne gaseous pollutants and particles affect buildings and other structures, equipment and machinery. Gaseous pollutants may directly attack building materials, metals and non-metals by reacting irreversibly. In the case of metals the mechanism of attack may be electro chemical in nature.

The extent of damage would depend on the temperature of the environment and the presence of moisture. Even in those cases where the surfaces are not directly attacked chemically but are covered by particle, they get damaged during the process of cleaning. The surfaces also get corroded by acid rain.

Particulate matter damages surfaces of equipment and machinery by abrasion and by getting lodged in between the moving parts. Particulate matter and gaseous pollutants may affect sensitive components of instruments and equipment either by getting deposited or by reacting chemically.

B. Stratospheric Effects:

In the stratosphere very little emission of pollutants occurs directly. The only direct sources of emission are supersonic air-crafts and rockets. The exhaust from such sources may contain CO, CO2 NOx, SO2, H2O and hydrocarbons depending on the fuel used.

Some pollutants also reach the stratosphere directly due to volcanic eruption. Other than these, some gaseous pollutants, which escape, complete chemical transformation in the troposphere, diffuse into the stratosphere. These are mainly NOx, chlorofluorocarbons and some hydrocarbons.

The above-mentioned pollutants react with the ozone molecules present in the ozone layer (of the stratosphere) and undergo oxidation. Absorption of UV solar radiation by the ozone molecules and the oxidation reactions (of Pollutants) cause a little warming of the stratosphere. This results in a slight positive (vertical) temperature gradient in the stratosphere.

In the ozone layer ozone molecules are produced by photochemical reactions as a result of absorption of solar UV radiation. Some of the ozone molecules get destroyed due to reactions with the pollutants present. As the concentration of the pollutants is increasing in the stratosphere the rate of destruction of ozone molecules is becoming more than its rate of production. This process is causing depletion of ozone molecules in the ozone layer.

The pollutants, which have been identified as the major agents responsible for depletion of ozone, are the chlorofluorocarbons (CFC). CFC is used as refrigerants in refrigerators and air-conditioners. Those are also used as aerosol spray, solvents, cleaning agents, foam-blowing agents, etc. The other ozone depleting substances (ODS) are methyl chloroform, carbon tetrachloride, methyl bromide and halons.

The CFC molecules, which find their way to the atmosphere, do not react chemically with oxygen in the troposphere but diffuse to the stratosphere where UV radiation dissociates them and produces chlorine atoms. The atoms act as a catalyst in the conversion of ozone into oxygen. As a result of this process the concentration of ozone molecules in the ozone layer is getting depleted.

The ozone layer plays a very important role in protecting living beings on the earth by absorbing high-energy solar UV radiation (220-330 nm). Progressive depletion of the ozone layer would result in more infiltration of UV radiation, which would cause more harm to the living beings including man.

Human health gets affected as a result of overexposure to UV radiation as it causes skin cancer, cataracts and immune system suppression. UV radiation also damages plants, marine ecosystem and synthetic as well as natural polymers.

Scientists, politicians and even common people, over the world, are concerned about the progressive depletion of the ozone layer. At some places (for example, at the South Pole) the ozone layer has become very thin, which is referred to as ‘ozone hole’.

To forestall further reduction of the ozone layer and also to enhance its regeneration an Interna­tional Agreement (Montreal Protocol) was signed in 1987 at Montreal. It was agreed that CFC production would be halved by 1995 and completely phased out by 2000. The Protocol was substan­tially amended in 1990 and 1992.

The developed countries agreed to phase out CFC with HCFC (hydro chlorofluorocarbon) by 2000. HCFC mostly undergoes chemical transformation in the tropo­sphere and the lower stratosphere and hence would not affect the ozone layer too much.

It has been envisaged to phase out HCFC with HFC (hydro fluorocarbon) which is more ozone-friendly having zero ozone depletion potential. The United Nation Environmental Programme (UNEP) has proposed that HCFC production should be stopped by 2005.


Other Things to Know About Methane Emissions

Who are the biggest methane emitters?

China, the United States, Russia, India, Brazil, Indonesia, Nigeria, and Mexico are estimated to be responsible for nearly half of all anthropogenic methane emissions. The major methane emission sources for these countries vary greatly. For example, a key source of methane emissions in China is coal production, whereas Russia emits most of its methane from natural gas and oil systems. The largest sources of methane emissions from human activities in the United States are oil and gas systems, livestock enteric fermentation, and landfills.

Why aren’t efforts to capture and profitably use methane emissions more widespread?

Despite multiple benefits, methane recovery is not widespread for several reasons.


CHILLED STORAGE | Principles

Controlled-atmosphere Storage Rooms

Controlled-atmosphere storage rooms were developed for specialized fruit stores, especially those for apples. Interest is growing in the application of this technique to other commodities including meat and fish. In addition to the normal temperature control plant, these stores also include special gas-tight seals to maintain an atmosphere, which is normally lower in oxygen and higher in nitrogen and carbon dioxide than air. An additional plant is required to control the CO2 concentration, generate nitrogen and consume oxygen. (See CONTROLLED-ATMOSPHERE STORAGE | Applications for Bulk Storage of Foodstuffs .)

There is growing interest in the use of controlled atmosphere retail packs to extend the chilled storage and display life of meat and meat products. Since the packs insulate the products, efficient precooling before packaging is important.


A Whale of an Effect on Ocean Life: The Ecological and Economic Value of Cetaceans

What if an animal could entertain and educate millions of people annually, enhance productivity (thereby increasing the number of fish in the sea), mitigate climate change, feed billions of marine animals, generate billions of dollars in revenue globally, and even help get tough stains out of your clothes? Does such an animal exist?

Whales—animals that humans nearly exterminated—can do all that and more. The unsubstantiated claims that whales compete with humans for fish or that they must be killed to ensure global food security are nonsense. Instead, a growing body of scientific evidence demonstrates that saving whales could help save the planet and, in turn, humankind.

Photo by Daniel Benhaim

Approaching Extinction
The era of large scale commercial whaling lasted nearly 400 years, from the early 17th century to 1986. During that period, whalers mercilessly pursued their prey, exploiting and depleting one species after the next. While the exact death toll amassed over these four centuries is not known, scientists have estimated that during the 20th century alone, over 3 million whales were killed, mainly for their valuable oil.

By the time a global moratorium on commercial whaling, approved by the International Whaling Commission (IWC), went into effect in 1986, scientists estimated that whale numbers had plummeted from 66 to 90 percent of their pre-whaling abundance, with some populations, like blue whales in the Southern Hemisphere, declining by 99 percent. While the moratorium remains intact today—saving countless whales—commercial and “scientific” whaling continue, with Iceland, Norway, and Japan killing more than 43,000 whales since 1986.

A previously ignored consequence of the slaughter was that it prevented whales from fulfilling their evolutionary role in the ecosystem. In every ecosystem, every native species has a role in the ecology of their habitat, from the smallest microorganisms to the most dominant predator. In a properly functioning ecosystem, they collaborate in a symbiotic dance that maximizes productivity and abundance within nature’s parameters.

Enhancing Productivity
Far from just providing huge amounts of meat, blubber, and oil for human consumption, whales provide important ecosystem services that have gone overlooked in debates about commercial whaling and whale conservation.

Whale fecal plumes contain valuable nutrients like iron, nitrogen, and phosphorus. They stimulate production of microscopic marine algae, or phytoplankton, which form the base of many marine food chains. Phytoplankton, via photosynthesis, convert chlorophyll, sunlight, and a variety of nutrients including carbon dioxide into energy, while expelling oxygen. Phytoplankton feed zooplankton, tiny animals that live in surface waters, and both are critical food sources for many marine species such as krill and other marine invertebrates, fish, and even marine mammals, including whales.

In a study of blue whales in Antarctica, scientists determined that iron concentration in blue whale feces is 10 million times that of Antarctic seawater. As iron is a limiting micronutrient in the Southern Ocean, its availability triggers phytoplankton blooms. Another study determined that blue whales in the Southern Ocean, via fecal plumes, increase primary production available to support fisheries by 240,000 (metric) tonnes of organic carbon (which all animals in the oceans need to survive) per year. If blue whales recover to pre-industrial whaling levels, this benefit will increase to 11 million tonnes of carbon per year—increasing, not decreasing, fishery yields. While this is only a small fraction of the overall primary production in the Southern Ocean, at the local scale where such fertilization benefits are realized, the impacts may be significant.

Indeed, scientists have determined that the slaughter of baleen whales in the Southern Ocean caused a long-term decline in primary production, which, in turn, caused the krill population to plummet to as low as 20 percent of pre-industrial whaling levels. Today, although whale stocks in the Southern Ocean are recovering—some more quickly than others—krill numbers have not recovered to pre-industrial whaling levels and are now threatened by direct harvest and climate change.

In the Gulf of Maine, scientists found that marine mammals enhance primary production in feeding areas by supplying nitrogen to surface waters through release of fecal plumes and urine. They determined that whales and seals may replenish 23,000 tonnes of nitrogen per year in the Gulf of Maine surface waters, more than the input of nitrogen from all of the rivers feeding the gulf combined.

In another study, endangered right whales in the Bay of Fundy in Canada were found to enhance primary productivity through the release of nitrogen and phosphorus in their fecal plumes. In Hawaii, the feeding behavior of 80 sperm whales transferred 100 tonnes of nitrogen from deep waters to surface waters, enhancing primary production by 600 tonnes of organic carbon per year. Due to the decimation of sperm whales by commercial whaling, however, Hawaiian waters have lost 2,000 tonnes of new nitrogen each year, decreasing primary production in the region by 1,000 tonnes of organic carbon annually.

The deep diving and surfacing behavior of sperm whales and some baleen whales transports nutrients in their fecal plumes from deeper water to the surface and, for gray and humpback whales, by carrying sediment from the sea floor and redistributing it in the water column, to the benefit of sea birds and other marine species. As noted by Drs. Joe Roman and James McCarthy, “Cetaceans feeding deep in the water column effectively create an upward pump, enhancing nutrient availability for primary production in locations where whales gather to feed.” This vertical transport of nutrients is referred to as the “whale pump” and was first postulated in 1983. Scientists have determined that biomixing by marine vertebrates, including whales, contributes one-third of total ocean mixing, comparable to the effect of tides or winds.

Whales also transport nutrients in their fecal plumes, urine, sloughed skin, and placental materials horizontally, a phenomenon referred to as the “whale conveyor belt,” as they migrate between nutrient-rich feeding areas and nutrient-limited breeding/birthing areas. Blue whales in the Southern Ocean, for example, transport approximately 88 tonnes of nitrogen per year from their feeding to their calving grounds. Before commercial whaling, blue whales would have transported 24,000 tonnes of nitrogen via the conveyor belt.

Sequestering Carbon
Phytoplankton use carbon dioxide during photosynthesis. Thus, enhancing phytoplankton productivity via the release of nutrients in whale feces increases the removal of carbon dioxide from the atmosphere. In the Southern Ocean, approximately 12,000 sperm whales deposit an estimated 36 tonnes of iron into surface waters each year, enhancing primary production in phytoplankton. While the carbon contained in some phytoplankton will continue to be recycled by marine animals feeding and defecating in surface waters, 20 to 40 percent of such carbon will settle to the sea floor as phytoplankton die and sink, effectively locking up the carbon for centuries to millennia. Globally, more than 200,000 tonnes of carbon may be sequestered—and its negative effects on climate removed—each year.

Sperm whales, by enhancing primary productivity, effectively remove 240,000 tonnes more carbon from the atmosphere than they add during respiration. Since sperm whale population numbers in the Southern Ocean have not recovered to pre-industrial whaling levels, an extra 2 million tonnes of carbon that could have been removed by a full complement of sperm whales remains in the atmosphere each year. Since Southern Ocean sperm whales represent only 3 percent of all sperm whales globally, the species may significantly contribute to iron fertilization and carbon drawdown.

When whales die, their massive bodies contain a large amount of carbon. As their carcasses sink to the ocean floor—often referred to as “whale fall,” this carbon is effectively stored in the ocean for centuries. Scientists have estimated that the combined global populations of nine great whale species (blue, fin, gray, humpback, bowhead, sei, Bryde’s, minke, and right whales) sequester nearly 29,000 tonnes of carbon per year via whale falls. Due to the significant loss of whales to commercial whaling, current populations of large baleen whales store 9.1 million tonnes less carbon than if their numbers were at pre-exploitation levels. If these whale stocks were rebuilt, they would remove 160,000 tonnes of carbon each year through whale falls, which is roughly equivalent to 110,000 hectares of forest (or an area the size of Rocky Mountain National Park).

Nourishing the Depths
In addition to storing carbon, whale carcasses feed an array of marine and terrestrial species. When whales strand on land, bears, other mammals, scavenging birds, and marine and terrestrial invertebrates benefit from the massive windfall of food and nutrients and, in turn, expand the nutrient flow from the sea to land.

Whale falls, according to the scientific literature, create habitat islands, benefiting scavengers like sharks and hagfish, crustaceans, gastropods, bivalves, clams, shrimp, anemones, bacteria, and a litany of other marine organisms, including some species heretofore unknown. Indeed, scientists have identified 129 new species collected from whale remains, including over 100 considered to be whale-fall specialists, and predict that hundreds of other whale-fall specialist species remain to be discovered.

The frequency of whale falls declined substantially due to industrial whaling and may have caused a substantial number of anthropogenic species extinctions in the deep sea. Whether such species would have had any value to humans will never be known—although, in an interesting twist, enzymes of psychrotrophic bacteria (bacteria adapted to extremely cold environments) found at whale falls have garnered commercial interest from the laundry detergent, pharmaceutical, and food processing industries. One biotechnology company has determined that clones of bacteria found on whale carcasses may be effective in removing stains from laundry during cold-water washing, potentially providing significant energy savings, increased profits, and cleaner clothes.

Creating Value
Whales have an enormous economic value as the popular subject of marine tourism. Globally, whale watching generated over 2 billion dollars in revenue in 2012 and supported some 13,000 jobs while providing millions of people an opportunity to observe and learn about whales and other marine species in the wild. Such revenue is well in excess of the value of whale meat, blubber, or other products sold commercially, demonstrating the obvious fact that a live whale is worth far more than a dead one.

The ecosystem services provided by whales, including increasing primary production, directly and indirectly sequestering carbon, and providing nutrients and habitat to myriad marine species, also have an economic value. Such values have been calculated for other species, including bats and pollinators. While economists have calculated the value of whale watching, no comprehensive assessment has been done of the direct and indirect value of whales and the economic and ecosystem services they provide.

Going Forward
The direct and indirect value of whales warrants attention. At its 2016 meeting, the IWC adopted a resolution that recognizes the contributions of cetaceans to ecosystem functioning and encourages IWC member governments to factor these contributions into decision-making. It further envisions a central role for the IWC Scientific Committee in (1) reviewing the ecological, economic, and other contributions of cetaceans to ecosystem functioning, (2) identifying gaps, and (3) creating a plan for future research needs. It also promotes collaboration with other multilateral environmental agreements to study the issue.

The subject has since been discussed at a conference about whales in Tonga. It was also the subject of an AWI-cohosted workshop in late July, at the Society for Conservation Biology’s International Congress for Conservation Biology in Cartegena, Colombia, that considered how to integrate this emerging issue into global environmental policy—for the good of the whales and the health of the planet. For example, although saving whales will not fully mitigate the impacts of climate change, it should be part of a comprehensive, global strategy to reduce greenhouse gas emissions.

Whales may not swim with capes but, based on the evidence of their immense ecological and economic value, perhaps they should be considered superheroes saving the planet. They should no longer be considered as a source of consumables. Instead, they should be fully protected from commercial and “scientific” whaling, bycatch in fishing gear, and other threats to their survival, so that they can fulfill their role in helping to sustain the planet and humankind.


The effect of greenhouse gases

There are five gases of human origin that contribute most – together up to 95% of the total – to the increase in global warming. Here you will discover the source of their emission, the time they spend in the atmosphere and what percentage they contribute to the greenhouse effect.

Carbon dioxide is responsible for 53% of the level of global warming. It is the result of processes such as fuel use, deforestation and production of cement and other materials. Its permanence in the atmosphere varies, but it’s very high at all times: 80% lasts for 200 years and the other 20% can take up to 30,000 years to disappear.

Methane is the next of the greenhouse gases which has the biggest effect on global warming (15%). This is generated by activities such as livestock production, agriculture, sewage treatment, natural gas and oil distribution., coal mining, fuel use and is also given off from waste tips. It lasts an average of 12 years in the atmosphere.

Halogenated compounds such as CFCs, HCFCs, HFCs, PFCs, SF6and NF3 are responsible for 11 % of global warming and generated as a result of the production of chemicals by diverse sectors such as refrigeration and air conditioning, electrical and electronic equipment, medicine, metallurgy, and so on. Depending on the type of compound, their duration in the atmosphere varies from a few months to tens of thousands of years.

Tropospheric ozone also has an 11% effect on global warming. This is a product of the reaction between the gases carbon monoxide (CO), nitrogen dioxide (NO₂) and VOCs (Volatile Organic Compounds), given off during the burning of fuels. These gases don’t last as long in the atmosphere as others, a matter of months at the most.

Finally, nitrous oxide also contributes around 11% to the global warming total. It comes mainly from the use of fertilizers, fuel use, chemical production and sewage treatment, and lasts longer in the atmosphere, up to 114 years.


Microbial mitigation of climate change

An improved understanding of microbial interactions would help underpin the design of measures to mitigate and control climate change and its effects (see also ref. 7 ). For example, understanding how mosquitoes respond to the bacterium Wolbachia (a common symbiont of arthropods) has resulted in a reduction of the transmission of Zika, dengue and chikungunya viruses through the introduction of Wolbachia into populations of A. aegypti mosquitoes and releasing them into the environment 258 . In agriculture, progress in understanding the ecophysiology of microorganisms that reduce N2O to harmless N2 provides options for mitigating emissions 214,259 . The use of bacterial strains with higher N2O reductase activity has lowered N2O emissions from soybean, and both natural and genetically modified strains with higher N2O reductase activity provide avenues for mitigating N2O emissions 214 . Manipulating the rumen microbiota 260 and breeding programmes that target host genetic factors that change microbial community responses 261 are possibilities for reducing methane emission from cattle. In this latter case, the aim would be to produce cattle lines that sustain microbial communities producing less methane without affecting the health and productivity of the animals 261 . Fungal proteins can replace meat, lowering dietary carbon footprints 262 .

Biochar is an example of an agricultural solution for broadly and indirectly mitigating microbial effects of climate change. Biochar is produced from thermochemical conversion of biomass under oxygen limitation and improves the stabilization and accumulation of organic matter in iron-rich soils 263 . Biochar improves organic matter retention by reducing microbial mineralization and reducing the effect of root exudates on releasing organic material from minerals, thereby promoting growth of grasses and reducing the release of carbon 263 .

A potentially large-scale approach to mitigation is the use of constructed wetlands to generate cellulosic biofuel using waste nitrogen from wastewater treatment if all waste in China were used, it could supply the equivalent of 7% of China’s gasoline consumption 264 . Such major developments of constructed wetlands would require the characterization and optimization of their core microbial consortia to manage their emissions of greenhouse gases and optimize environmental benefits 265 .

Microbial biotechnology can provide solutions for sustainable development 266 , including in the provision (for example, of food) and regulation (for example, of disease or of emissions and capture of greenhouse gases) of ecosystem services for humans, animals and plants. Microbial technologies provide practical solutions (chemicals, materials, energy and remediation) for achieving many of the 17 United Nations Sustainable Development Goals, addressing poverty, hunger, health, clean water, clean energy, economic growth, industry innovation, sustainable cities, responsible consumption, climate action, life below water, and life on land 6 (Box 1). Galvanizing support for such actions will undoubtedly be facilitated by improving public understanding of the key roles of microorganisms in global warming, that is, through attainment of microbiology literacy in society 7 .


Anthropogenic Effect and Time Lag

Since the Industrial Revolution, the amount of CO2 is the atmosphere has been increasing due to human activities, reaching levels likely much higher than any time in approximately the last half-million years. Similarly, global average temperatures have jetted upward. By converting to renewable energy sources and clean-burning fuels, this trend could be reversed, and the proportion of atmospheric carbon dioxide -- and therefore temperatures -- could decrease back toward their natural level. However, even if humans were to completely cease carbon emissions tomorrow, it would probably take thousands of years for the excess carbon dioxide to clear out of the atmosphere, according to the National Aeronautics and Space Administration. It, therefore, remains unlikely that atmospheric CO2 levels will decrease significantly in the foreseeable future. Furthermore, the carbon dioxide already in the atmosphere means that the climate would continue warming until the Earth restores itself to its natural equilibrium.


Watch the video: Παγκόσμια Ημέρα Κατά του Καρκίνου - Ατμοσφαιρική Ρύπανση - Ένα μείζων πρόβλημα Δημόσιας Υγείας (August 2022).