Ambient air sampling and monitoring Topic 5 Ms. Sherina Kamal

Ambient air quality measurement Used to Determine areas and time periods when the levels of pollution exceeds the acceptable values Evaluate parameters for air pollution modeling Establish and evaluate control measures

Sample collection Gaseous air pollutants Common gases SOX NOX O3 HS2S HCl Hydrocarbons vapors Particulate air pollutants PM10 PM2.5

Gaseous air pollutants Methods for collection Absorption in reagent solution Adsorption on solids Condensation at lower temperature Grab sampling

Gaseous air pollutants Absorption in reagent solution Most frequent method employed to collected the gaseous pollutants Collection takes place either through solubility/by chemical reaction

Gaseous air pollutants Adsorption on solids Hydrocarbons and other high boiling pollutants are best adsorbed on solids  Activated carbon  Alumina  Silica gel

Gaseous air pollutants Condensation at lower temperature Condensate out the gaseous pollutants in air by passing the sampled gas through series of coils immersed in containers cooled by freezing mixture

Gaseous air pollutants Grab sampling Use an evaporated flask or an inflatable bag Taken at particular location and time within few seconds up to a minute or two Taken in one of the following ways: Using an evacuated container Purging or displacing the air Displacing the liquid Inflating a plastic bag Using a syringe Using an adsorbent cartridge

Particulate air pollutants Required for two situations: Ambient air measurement Involves the measurement of particulate concentration in the ambient air that people breathe Source measurement Concerns of air/gas flowing in the channels/stack of an industry

Particulate air pollutants: sample collectors for ambient air Two commonly used ambient air samplers: Dust-fall sampler Made from polyethylene, glass or stainless steel Particles larger than 10um-setteable Particles smaller than 10um-suspended

Particulate air pollutants: sample collectors for ambient air High volume sampler Allows unrestricted access of ambient air from all directions using a suction blower of a known capacity

Particulate air pollutants: sample collectors for source measurement Aim of particulate matter measurement: To determine the amount and nature of pollutant contained in gases emitted from a source

Particulate air pollutants: sample collectors for source measurement The particles concentration data can be used to: Determine the compliance and non-compliance standards Select and design air pollution control equipment Determine the efficiency of processes and control equipment Determine the emission factor for an activity or process Suggest way to improve the efficiency of controlling equipment

Analysis of pollutants: analytical methods Collected gas sample can be one of the following forms Absorbed in a liquid, often with a chemical reaction Adsorbed on a solid Filtered of a filter Quantity of air collected in a container/bag

Analysis of pollutants: analytical methods For some pollutants, the concentration can be easily measured By gravimetric method Direct weighing In a higher volume sampler Weight of the filter is determined before and after a known volume of air has been sampled

Analysis of pollutants: analytical methods Other analytical methods: Colorimetry Concentration of a colored substance is determined by measuring the light pass through it Commonly employed for SO 2 and NO 2 Coulometry Quantity of electrons is required to oxidize/reduced a substance is measured

Analysis of pollutants: analytical methods Chemiluminescene Measuring ozone uses the reaction of Rhodamine B impregnated on actibvated silica gel with ozone Can measure ambient level of NO and NO 2 IR and UV Passed through a chamber containing the air sample The dispersed radiation is then detected Can measure CO

Analysis of pollutants: analytical methods Flame isolation Has a wide application as a continuous monitor for hydrocarbons Sample to be analyzed is mixed with hydrogen and passed through a small jet; the air supplied supports combustion Gas chromatography Technique for separation of closely related compounds  Mixture of hydrocarbons Sensitivity is very high particularly used for VOCs and toxic air pollutants  benzopyrene