Theory & Procedure, Study of Pollutants in Air | Additional Study Material for NEET PDF Download

Aim

To study the presence of suspended particulate matter in the air at different sites.

Theory

Pollution is the addition of any substances into the natural environment that makes it harmful to humans, animals and plants. Substances that cause pollution to the environment are called pollutants. Pollutants can be either foreign substances/energies or naturally occurring contaminants. The three main forms of pollution are air pollution, water pollution and land pollution. We will look at the air pollution in this experiment.

Air pollution

Air pollution is the contamination of the air, by the introduction of particulates, smoke or harmful gases into the atmosphere.  Some air pollutants are poisonous, which makes it difficult for plants, animals and humans to survive. The atmosphere in highly populated areas are very rich in dust, smoke and suspended particular matter, all due to vehicular exhausts and industrial emission. Air pollution causes major respiratory and heart problems in our bodies.

Let’s look at some of the major air pollutants.

Major air pollutants are following:

• Carbon Monoxide: Emitted from combustion processes.
• Ground-level Ozone: Secondary pollutant formed by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.
• Lead: Lead can be released into the air through metal refineries, battery manufacturing, volcanic eruptions, sea spray and bushfires.
• Nitrogen Dioxide: NO2 forms from power plants, by fuel combustion and wood burning.
• Particulate Matter: Particulate matter is a sum of all extremely small particles and liquid droplets suspended in air. This is formed through chemical reactions, fuel combustion (e.g., burning coal, wood, diesel), industrial processes and farming (plowing, field burning).

Learning Outcomes:

• Students understand the term pollution.
• Students understand different air pollutants.
• Students do the experiment better in the real lab having gone through the animation and simulation.

Materials Required

Real Lab Procedure

• Take 8–10 feet long piece of twine thread.
• Take five leaves and tie them on the thread leaving a foot distance in between.
• Make three such long threads tied with leaves.
• Take some petroleum jelly and apply an extremely thin layer of petroleum jelly on surface of each leaf.
• Make a bundle of these leaves and pack them in polythene bags.
• Make three such bundles of smeared leaves and mark them as A, B and C.
• Carefully weigh each bundle of leaves along with the polythene bags and record values in the table.
• Select three different spots in a manner that one has heavy vehicular traffic, one has moderate traffic and one has no vehicular traffic.
• At spot ' heavy vehicular traffic ' expose each leaf of bundle 'A' by stretching the attached thread and tie the two ends to two poles at 10 feet height above ground.
• Similarly expose leaf bundle 'B' at ‘moderate traffic' and leaf bundle 'C' at ' no vehicular traffic'.
• Keep leaves exposed for about two hours.
• After exposure, collect the leaves from the spot and carefully re-bundle exposed leaves and place them, along with the string, in the corresponding polythene covers.
• At the end of the experiment, return to the laboratory.
• Reweigh each bundle of exposed leaves along with their respective polythene covers and record the values in the table.
• The weight of suspended particles can be calculated by the difference between the weight of leaves after exposure and weight of leaves before exposure.

Observations

The atmosphere in highly populated area is very rich in dust, smoke and suspended particulate matter all due to vehicular exhausts and industrial emission. From the table we can see that the weight of suspended particles in heavy vehicular traffic spot and moderate traffic is greater when compared to the no vehicular spot.

Simulator Procedure (as performed through the Online Labs)

• Note the weight of the leaf bundle displayed in the weighing machine.
• You can enter the value in the corresponding site in the worksheet.
• Click and drag the leaf bundle from weighing machine and drop into the particular site.
• A timer is shown and you need to wait till the timer stops.
• Click and drag the leaf bundle back onto the weighing machine to weigh it again.
• You can enter the value in the corresponding site in the worksheet.
• Based on the values entered, the worksheet gives the weight of suspended particles.
• You can redo the experiment by clicking on the ‘Reset’ button.