pH as abiotic Factor of Environment - Dr. Vidhin Kamble

 

pH as Abiotic Factor of environment

 pH as abiotic factor

The term "pH" was first described by Danish biochemist Søren Peter Lauritz Sørensen in 1909. pH is an abbreviation for "power of hydrogen" where "p" is short for the German word for power, potenz and H is the element symbol for hydrogen.

pH is determined by the concentration of hydrogen ions (H+ ). It is a measure of the acidity and alkalinity, on a scale from 0 to 14.

1.     Acidic solutions have a pH less than 7,

2.     The basic or alkaline solutions have a pH greater than 7. 

3.     The pH 7 Indicate neutral. An example of a neutral solution is pure water at room temperature.

pH plays an important role in the survival of animals, including human beings? Our body works well within a narrow pH range of 7 to 7.8. If, due to some reason, this pH gets disturbed or change in the body of a person, then many ailments can occur. The pH value of Hcl in stomach is between 1.5 to 3.5.

Pure water has a pH of 7, which is neutral. Higher numbers indicate alkaline water, the greater, the more alkaline. Lower numbers indicate acidity, the lower the pH, the more acid.

The ideal pH level of drinking water should be 6 to 8.5 the human body maintains pH equilibrium on a constant basis and will not be affected by water consumption.

Measurement of pH:

There are multiple methods of measuring pH.

1.     The most common method is a pH meter, which involves a pH-sensitive electrode (usually made of glass) and a reference electrode.

2.     Litmus paper is probably the most familiar pH paper.

It is used to test whether a solution is acidic or basic or neutral  and comes in following three types—

a)     Red

b)    Blue,

c)     Neutral.

Red litmus turns blue in basic solutions,

Blue litmus turns red in acidic solution,

neutral litmus (usually purple) turns red in acidic solutions and blue in basic solutions.

3.     A colorimeter may be used to measure the pH of a sample.

Impact of pH on Plants

pH affects plant growth primarily through its effects on nutrient availability. High or low pH cause deficiencies in essential nutrients that plants need to grow.

Nutrient Availability

In acidic soils frequently occurred deficiencies of calcium, phosphorus and magnesium.

Alkaline soils demonstrate deficiencies in phosphorus and many micronutrients.

Macronutrients, including nitrogen, phosphorus and potassium, are the major nutrients plants need to grow and are less available for plants when soils are acidic, or have a low pH.

Micronutrients are used in smaller amounts by plants, and are less available in alkaline soils, or soils with a high pH. These micronutrients include boron, copper, manganese and iron.

Impact on Soil Microorganisms

The microorganism such as bacteria and other organisms that inhabit the soil, are most active at a pH of 6.3 to 6.8. These organism are helps in the  processes of break down plant waste, such as leaves, are most active at that level.

Some plants, such as blueberries and rhododendrons, like acidic soils, while vegetables and most ornamentals thrive in slightly acidic conditions. Plants such as lily and chrysanthemum are able to tolerate slightly alkaline soils.

Nutrient Availability

Many of the elements most used by plants in their growth are less available when the pH is in the acid range, below 6, and many of the micronutrients, those used in small quantities, are less available when the water, or soil, is alkaline.

Many common vegetables and ornamentals prefer soil with a pH of around 6.5 These include spinach, parsnips, dahlias, chrysanthemums, sweet peas and tulips.

 

Chlorosis

One common effect of the application of water with a high pH, or of a high soil pH, is chlorosis, or the yellowing of the leaves in such a way that the leaf veins remain green

Necrosis in plant;

When a living organism's cells or tissues die or degenerate, the condition is called necrosis.

Incorrect soil pH for the plant can cause nutrient deficiency. Nutrients for which deficiency leads to necrosis include potassium, nitrogen, boron, iron and nickel.

Impact of pH on animal

In aquatic animals like fish can survive in lake or river water within a narrow range of pH change.

Most freshwater lakes, streams, and ponds have a natural pH in the range of 6 to 8. Acid deposition has many harmful ecological effects when the pH of most aquatic systems falls below 6 and especially below 5.

 

Effect on survival:

When the pH of rain water is about 5.6 then it is acid rain. Too much acidic rain makes difficult for the aquatic animals to survive and can even kill the aquatic animals.

Effect on animal distribution:

As the pH of water body approaches 5, undesirable species of plankton and mosses may begin to invade leads to decrease in populations of fishes even though they disappear from the water body. Generally,  below a pH of 4.5, the water is essentially devoid of fish.

Effect on respiration:

Aluminium ions attached to minerals in nearby soil can be released into lakes, where they can kill many kinds of fish by stimulating excessive mucus formation in gill, and death of fish  due to asphyxiation.

Effect on reproduction:

The most serious chronic effect of increased acidity in surface waters appears to be interference with the fish’ reproductive cycle. It affect egg laying capacity of female.

Impact on Ammonia toxicity:

 High pH may also increase the toxicity of other substances. For example, the toxicity of ammonia is ten times more severe at a pH of 8 than it is at pH 7.

 It is directly toxic to aquatic life when it appears in alkaline conditions. Low concentrations of ammonia are generally permitted for discharge.

Acid rain

Acid rain can be caused by volcanic eruptions, but recently it has been attributed to the burning of fossil fuels along with industrial byproducts being spewed into the atmosphere.

1.     Damage to Forests, Plants, and the Food Web

2.     Reduced pH Level in Water.

3.     Poisoning of the Soil

Ex.

Acid rain leached calcium from the soil, which was the primary source of calcium for snails in that environment.

The snails soon died off, which was the primary source of calcium for birds in that habitat. The birds had to look to other sources for their calcium, such as insects. The birds were not able to receive a significant amount of calcium and began to lay defective eggs.

Maintaining pH

1.     Natural processes such as rainfall lower pH by leaching out minerals that make soils alkaline.

2.     Fertilizers that contain ammonium, urea or organic matter also tend to lower pH.

3.     The most common additive used to raise pH is lime.

4.     calcium carbonate is added to acidic lake water to neutralise the acid that comes from acid rain. This prevents the aquatic animals from being killed.