Contaminant, Receptor, Sink, Treshold limit Value, Lapse Rate and Temperature Inversion

Contaminant
The unfavorable substances which do not occur in nature but are introduced by human activity into the environment (affecting its composition) are known as contaminant.

Example: Chlorine gas(Cl2) which is not present in nature but to the escaption of derailed railway tank car its occurs in nature, which is contaminant.
CFC (Chlorofluoro carbon) one of the most important contaminant is introduced in nature due to the use of the re-frigerator, circular, etc.
The process by which contaminants are introduced in our fresh environment is known as contamination.

Receptor
The medium which accept pollutants is called receptor. Human beings, plants are the example of receptor.
We can also say that the medium which is affected by pollutant is known as receptor.


Sink
The medium which retains and interacts with long live pollutants. A marbal wall will act as a sink for atmospheric sulphuric acid and ultimately get damage.

Threshold limit value
This indicates the permissible level of toxic pollutants in atmosphere to which a healthy industrial worker is exposed during an eight hour day without any adverse effect.

If an industrial environment contain 0.002 mg/m3 Be and 1.00 mg/m3 Zn, then a healthy industrial worker, worked that environment without any adverse effect. Thus the threshold limit vakue for Be is 0.002 mg/m3 and for Zn is 1.00 mg/m3 .

Lapse Rate
The change of atmosphere air temperature with attitude is called lapse rate.
Lapse rate is of two types:
1. Positive Lapse Rate
2. Negative Lapse Rate

Positive Lapse Rate
The decrease of temperature with increasing altitude is called the Positive Lapse Rate.

For example: In troposphere the temperature decreases as 15°C to -56 °C with the increase of altitude. It is positive lapse rate.

Negative Lapse Rate
The increase of temperature with increase of altitude is called negative lapse rate.

For example: In stratosphere, the temperature increases as -56 °C to -2°C as the increase of increase of altitude. Thus this negative lapse rate.

Temperature Inversion
The transition from positive lapse rate to negative lapse rate at the top is called temperature inversion. In other words, the increase of temp. with the increase of altitude is known as temperature inversion. Thus temp. inversion is also called negative lapse rate. Temperature inversion occurs in the atmosphere due to two reactions.
1. Radiation Inversion: This occurs when the air near the earth’s surface get cooled because of the loss of the heat by earth by emitting long wave radiations.
2. Subsidence inversion: This occurs when the upper layers of air subsides during a developing anticyclone.