What is Pollutant?
If the concentration of a substance already present in nature is increased to unrequired ratio due to human activity, which ultimately has a detrimental effect on the environment either by reducing the quality of life or affecting the health then it is known as a pollutant.
Example: sulphur dioxide, carbon monoxide, lead, mercury, excess heat, sound etc.
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What is a contaminant?
A contaminant is a substance that does not occur in nature but is introduced by human activity into the environment. A contaminant is called a pollutant when it exerts a detrimental effect on human health. It is also a pollutant.
What is the receptor in environmental science?
A receptor may be any thing which is affected by the pollutant. For example, man is a receptor of contaminated water because cholera and gastroenteritis are caused by it.
What is the sink in environmental science?
It is the medium, which interacts and retains the long lived pollutant. The oceans are the sinks for atmospheric carbon dioxide. Ground water and subsoil water act as sinks for pesticides employed in agriculture.
What do you mean by the term Threshold limit value (TLV)?
This value indicates the permissible level of a toxic pollutant in the atmosphere to which a healthy industrial worker can be exposed during an eight hour day without any adverse effect. TLV of a pollutant is found by experimentation on animals, medical knowledge and experience, and environmental studies.
What is biochemical oxygen demand (BOD)?
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present at a certain temperature over a specific time period. The BOD value is most commonly expressed in milligrams of oxygen consumed per liter of the sample during 5 days of incubation at 20 °C. BOD can be used as a gauge of the effectiveness of wastewater treatment plants.
What is the chemical oxygen demand (COD)?
The chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. In these methods, a fixed volume with a known excess amount of the oxidant (KMnO4, K2Cr2O7) is added to a sample of the solution being analyzed. After a refluxing digestion step, the initial concentration of organic substances in the sample is calculated from a titrimetric or spectrophotometric determination of the oxidant still remaining in the sample.
BOD is similar in function to chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matter.
References:
- Environmental Chemistry, S. Manahan, Lewis Publisher
- Air Quality, Thad Godish, Lewis Publishers
- Environmental Chemistry ( 7th Ed), B.K. Sharma, Goel Publishing, Meerut