Environmental Monitoring Methods
Environmental Monitoring is process of understanding the level of harmful pollutants present in atmosphere and its effects on environment, human life, animals and trees.
Objectives of Environmental Monitoring
Data obtained from Environmental monitoring can be used to draw trends for future complications. Also it allows us to identify natural calamities before time and precautionary measures can be taken to soften the impact.
Type of environmental monitoring is purely depends upon the objective or purpose. Environmental monitoring methods change on number of locations, duration of survey, time of survey.
Environmental monitoring methods can be classified into three types: Planned emission, fugitive emission and accidental emissions.
Source Emission Monitoring
Source emission monitoring is carried out to determine emission rate for particular source and its effects to environment. Environmental Monitoring Methods vary based on source of emission.
Stationary Source or Stack Monitoring
There are two important points in stack monitoring. First the sample taken should be accurate representative of pollutant emission at particular point and at particular time. Also the frequency and duration of sampling should be kept at particular interval so that combined reports or results can become complete source emission.
In monitoring process of a circular stack sampling points at equal distance ensures the emission variation are counted. In rectangular stack monitoring sampling points should be located at equal distance from each other. Generally 8-12 sampling points are enough to overcome any deficiencies in the location of stack.
Mobile Source Monitoring
Mobile source monitoring means monitoring emission released from Vehicles and air crafts. While monitoring mobile sources state of engine (idling, accelerating, braking or cruising etc.) is also should be taken into consideration.
Waste Water Monitoring
Waste water sampling is also like stack monitoring as liquids are also irregular like gases. In waste water sampling samples are taken from different cross section points for sample to be representative of source. Sampling from vertical pipes is less liable to affected by deposition of solids as compared to horizontal pipes.
Whenever there is variation of effluents with time then grab samples or auto samplers are used to get more representative sample. Grab sampling is one of traditional environmental monitoring methods.
Solid Waste Monitoring
Solid waste are more inhomogeneous than gases and liquids. Solid waste are generated after waste water treatment, remained residue from municipal furnace, wastes from coal fired from power plants. In Solid waste sampling composite sampling method is used to get more representative sample.
Ambient Environmental Monitoring
Environmental monitoring can be carried out for different reasons, but the most important reason is to get more representative sample of particular place and time. Air pollution vary place to place, time to time and pollutant to pollutant, therefore sampling methods, duration, time, frequency vary depending upon factors.
Site selection in environmental monitoring is very important as it directly affect the samples and results.
Environmental Monitoring Methods
There are many types of sampling methods are available for Air, Water and Soil. We will see only those which are used widely.
In this method based on type of pollutants needs to monitored filtration method is selected.
Very high velocity air is passed through wet or dry impingers based on collecting surface. If collecting surface is dry then dry impingers are used and when collecting surface is wet then wet impingers are used.
This is a very simple environmental monitoring method to air sampling. In this process a open container is placed in open outdoor area which is free from overhead obstructions. This method is widely used to determine fallout or dust fall in particular area.
This method is very simple, does not required electrical power or moving parts. Only disadvantage is lack of precision and inability to distinguish peak dust fall as entire sampling period may go till 30 days.
This method is very efficient to collect small samples. On entering into sampler particles pickup charge and get deposited on electrodes.
The adsorption of gases is surface phenomenon. Gas molecules are deposited on the surface of solid Surface. Materials like activated carbon, silicagel, alumina etc. are used in adsorption process.
In this method sample collected is cooled down to below boiling point of the anelyte and sample becomes concentrated. Generally there are two traps one is at zero 00 degree as water vapour becomes water and same can be removed from sample as it is in liquid state. And then sample again cooled down till -1960C.
In grab sampling high volume samplers are used with filters in air quality monitoring process. Filters are consist of glass fibres and have efficiency of 99% particles with 0.8 µ diameter. Sampling is desirable where people work. Sample collected by high volume samplers are further analysed in laboratory chemically, by microscopes, gravimetric and extraction techniques
In Water sampling sample is collected from different locations, different depths and sent to laboratories for analysis.
In composite sampling sample is collected from different locations,different time to make sample more representative of source. This type of sampling method gives an average condition of presence of pollutants.
Do you know new environmental monitoring methods which are not listed here? Let us know by commenting below.
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