Air Pollutiondocx

=== Air pollution ===

Air Pollution

Air pollution is defined as an atmospheric condition in which substances are present at concentrations high enough, above their normal ambient levels, to produce a measurable effect on man, animals, vegetation, or materials. Such polluants may be present as solid particles, liquid droplets or gases.

Air polluants classification.

According to chemical composition:

Sulfur-containing compounds,

Nitrogen-containing compounds.

Carbon-containing compounds.

Halogen-containing compounds.

Toxic substances (any of about).

Radiative compounds.

According to physical state:

Gaseous.

Liquid (aqueous).

Solid.

According to the manner in which they reach the atmosphere:

Primary pollutants (those emitted directly from the sources).

Secondary pollutants (those formed in the atmosphere by chemical interactions among primary pollutants and normal atmospheric conditions).

According to the space scales of their effects:

Local (or indoor).

Regional.

Global. 

Levels (concentrations )definition:

limit value – the level set based on scientific knowledge in order to avoid and prevent the occurrence of damaging events and reducing their effect on human health and the environment as a whole; is reached in a given period and not to be exceeded once was achieved;

critical level – the level set on the basis of scientific knowledge, which if exceeded, direct adverse effects may occur on some receptors, such as trees, plants or natural ecosystems but not on humans;

tolerance – the percentage of the limit value by which that value may be exceeded under the conditions set out in this law;

air quality plans – plans setting out measures to achieve the limit values ​​or target values;

target-value – the level set in order to avoid and prevent the occurrence of harmful events and reducing their effect on human health and the environment as a whole, which should be achieved as far as possible within a certain period;

alert threshold – the level which, if exceeded, there is a risk to human health from brief exposure for the population in general and the need to act immediately;

information threshold – the level which, if exceeded, there is a risk to human health from brief exposure for particularly sensitive sections of the population and for which immediate and appropriate information is necessary;

upper assessment threshold – the level below for which, if is needed to assess ambient air quality, it can be used a combination of fixed measurements and modeling techniques and / or indicative measurements;

lower assessment threshold – the level below for which, if is needed to assess ambient air quality, it is sufficient to use modeling techniques or objective estimation;

Determination of air pollution

The process of determining the air pollution has two stepts: providing the air sampling and analyzing it.

Collecting air sample

Collection through suction -method

Process: The air gets sucked by the – Air Pump – tap into a retainer – Collection Media – (where there is a specific filter for each unit), then passes through a device for measuring the volume of air – Flow Adjust – (it’s necessary to know the volume of intake air in order to make determinations and analysis).

Allows the determination of air pollution when the polluants concentration is very low and also with polluants that are smaller than 5µm in diameter (those one don’t sediment),

The collection can be done by filtration impact or absorbtion.

Retaining through filtration

It involves using a filtering material inserted into a specific retainer : glass wool, papper, a filtrant membrane.

Collection through impact

It involves projecting the polluted air towards an obstacle, where the polluted particles are retained; the obstacle cand be solid or liquid (alcoholic solutions)

Collection through absobtion

It is used for gas polluants that are retained from the air with an absorbant substance (charcoal).

Collection by sedimentation – method

It’s used to determine air’s pollution with sediment particles (bigger than 5µm in diameter) and consists in exposing cilindric glass vessels containing 15-200 ml distilled water for 30 days where particles will sediment.It is a cheap method.

Using this method can have some disadvantages:

Not knowing the volume of air of which the sediments where collected (imprecise results)

The quantity of sediment particles depends on how long the retained vessels were exposed.

Allows only the determination of sediment particles bigger than 5µm in diameter

Sanitary rules in European Union