Category Archives: Environmental engineering

aeroponics, Environmental engineering

Aeroponic Farming – Process, Types, Advantages – Full Details

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Aeroponic farming is one of the major techniques in indoor farming. This techniques is becoming popular these days due to greater yields. It also allows the ability to control the growing environment. Greenhouse and vertical farming are the two main types of indoor farming.

Vertical farming is becoming a more cost-effective method in horticulture, allowing for more resource utilization and land efficiency. Plant cultivation in vertically stacked irrigation systems using artificial or natural light is known as vertical farming. This method frequently employs soilless growing settings as well as hydroponic or Aeroponic irrigation systems.

  1. What is Aeroponic Farming?
  2. Aeroponic Farming
  3. Different Types of Aeroponic Systems
    1. Low-Pressure Aeroponics (LPA)
    2. High-Pressure Aeroponics (HPA)
  4. Hydroponics vs Aeroponics
  5. Tools used in Aeroponics
  6. Aeroponics Advantages
  7. Drawbacks of Aeroponics
  8. Conclusion

What is Aeroponic Farming?

Aeroponics involves growing plants in an air or mist environment. It does not use soil or an aggregate medium. Sounds unbelievable right? You would be shocked to know that mother nature has employed aeroponic growing in plants such as epiphytic orchids and bromeliads. These plants absorb naturally occurring aerosols like mist through their leaves and aerial roots.

Read on to find more about aeroponics, its types, equipment, benefits etc. as I take you on a short trip through an Aeroponic farm. Let’s begin by understanding the process of Aeroponic farming.

Also read: Green Walls – Vertical Gardens – Top 10 healing benefits

Aeroponic Farming

  • Aeroponic farming involves growing plants hung in a closed or semi-closed environment. This is achieved by spraying a nutrient-rich water solution onto the plant’s dangling roots and lower stem.
  • We insert the plants into the holes on top of a reservoir and placed into a sealed container.
  • We need to provide a support collar to keep stems in place. There’s no root zone medium for them to anchor in. These collars must be hard enough to hold plants upright. They also need to keep roots in place. Additionally, they should be flexible enough to allow roots to grow.
  • The pump and sprinkler system produces vapour from the nutrient-rich solution. This vapour is a hydro-atomized spray mixture of water, nutrients, and growth hormones.
  • The dangling plant roots absorb the nutrients while spraying this mist in the reservoir. The spray delivers just the right amount of moisture to encourage the plant’s growth and development.
  • The timer provides the plants with pre-programmed spray intervals and durations.

Because of the sensitivity of root systems, sometimes we pair aeroponics with traditional hydroponics. It acts as a backup “crop saver” if the aeroponic equipment fails. Let’s have a look at the common types of aeroponics.

Aeroponic Farming
Aeroponic Farming

Different Types of Aeroponic Systems

Depending on the intensity of pressure to atomize the water droplets there are two types of Aeroponic systems. They are:

Low-Pressure Aeroponics (LPA)

  • Plant roots are held above a nutritional solution reservoir or inside a channel connected to a reservoir in low-pressure aeroponic gardens.
  • A low-pressure pump delivers nutritional solution via jets or ultrasonic transducers into the reservoir, where it drips or drains.
  • Plants in these units tend to develop dry parts of their root systems as they mature, preventing appropriate nutrient uptake.
  • Due to its ease of setup, availability at any hydroponic shop, and low cost, this is the most common aeroponic farming technique.
Aeroponic system
Aeroponic system

Also read: Methods of Irrigation- 3 Methods Full Guide

High-Pressure Aeroponics (HPA)

  • The HPA system operates at extremely high-pressure to atomize water into small water droplets of 50 microns or less.
  • A high-pressure (80 pounds per square inch (550 kPa)) diaphragm pump feeds nutrients to the roots via 20–50 micrometre mist heads.
  • Since this system produces such small droplets it provides more oxygen to the root zone than the LPA. Thus it is the most efficient aeroponic system available.
  • High-Pressure Aeroponics is more complicated and more expensive to put up due to the specialised equipment required. As a result, they find frequent use in commercial production rather than home growers.

Hydroponics vs Aeroponics

Aeroponics is distinct from hydroponics, aquaponics, and in-vitro (plant tissue culture) cultivation. Hydroponics relies on nutrient-rich water to provide nutrition to plants. In contrast, aeroponics uses nutrient-rich mist for plant nutrition. Unlike hydroponics, which uses a liquid nutrient solution as a growing media and critical minerals to support plant growth, and aquaponics, which uses water and fish waste to support plant growth, aeroponics does not use a growing medium.

Aeroponically Cultivated Cabbage
Aeroponically Cultivated Cabbage
AspectHydroponicsAeroponics
Growing MediumUses water with dissolved nutrients and a substrate like coco coir or perliteDoes not require a substrate; plants are suspended, and roots are misted with nutrient solution
Water UsageRequires a large amount of water but recycles it efficientlyMore water-efficient as it uses a fine mist for root nourishment
Nutrient DeliveryNutrients are delivered through water in a continuous or timed flowNutrients are delivered via misting, making absorption more direct and efficient
Space EfficiencyRequires larger space for setup due to containers or tanksMore space-efficient; plants can be vertically stacked for aeroponic farming
Setup ComplexityEasier to set up with fewer technical requirementsMore complex setup with misting systems, requiring regular maintenance and monitoring

Having understood the basics of aeroponics, let me introduce you to the tools used in it.

Tools used in Aeroponics

If you are planning to set up an aeroponic farm, you will need:

  • A reservoir/container to hold the nutrient solution
  • Nutrient pump
  • Mist nozzles
  • Tubing to distribute water from the nutrient pump to the mister heads in the growing chamber
  • Baskets to suspend plants
  • Enclosed growing chamber for the root zone
  • Watertight containers for the growing chamber
  • Timer to turn on and off the pump

Next, we are moving to the advantages of aeroponics.

Aeroponics Advantages

The following are some of the advantages of aeroponics:

  • Due to the lack of a growing substrate, plant roots can absorb the maximum amount of nutrients. This leads to greater plant yields. Studies report that Aeroponically grown plants like basil, parsley, cherry tomato, squash, bell pepper and red kale increased their yield by 19%, 21%, 35%, 50%, 53% and 65% compared to soil culture, respectively
  • Plant roots get oxygen 24 hours a day, seven days a week, resulting in massive plant growth. This encourages plants to develop quickly.
  • Because of the higher nutrient absorption rate, relatively fewer nutrients and water are consumed on average compared to conventional plants.
  • Aeroponic systems offer greater mobility. You can simply transfer plants or even entire nurseries around because all you have to do is move the plant from one collar to the next.
  • Only a small amount of room is necessary. This system does not require a lot of areas to set up. Plants are stacked on top of one another. You can make the most of limited space with this type of modular system.

Drawbacks of Aeroponics

Aside from its numerous benefits, aeroponics has several drawbacks that can’t be overlooked, including:

  • Since aeroponic systems are highly sensitive to external conditions, it necessitates continual monitoring of pH and nutrient density ratio.
  • Understanding and applying the proper ratio for nutrients, water supply can be challenging for beginners, and should only be tried by people who are more experienced with such systems.
  • Initial setup can be expensive, costing hundreds of dollars per person.
  • Demands constant monitoring of the growing conditions.

Shall we wrap up?

Conclusion

As compared to other systems, the most significant advantages of aeroponics are the huge plant growth and higher yields. These benefits, however, come at a price. The cost of installing the system is high. It also requires technical know-how. Additionally, you need sophisticated knowledge of pH and nutrient density ratio. If you are new to hydroponics, carefully assess the pros and cons. Then choose the method you believe will work best for you now.

Environmental engineering, Water pollution

What are Water Pollutants? – Definition, Sources and Types

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Water Pollutants kill more people every year than from all forms of violence including war, according to the UNDESA. Every day, 2 million tons of sewage, industrial, and agricultural waste reaches water bodies all over the world. With the growth of the human population, industrial and agricultural activities the hydrological cycle got disrupted. As a result, declining water quality has become a global issue of concern.

In this blog, I will take you on a short trip exploring the various water pollutants, its sources and effects.

Water Pollutants Definition

Water Pollutants are the organic or inorganic chemicals and microbes that degrade the water quality of a water body and renders it hazardous for human consumption and the aquatic life thriving in it. Toxic compounds from farms, cities, and factories easily dissolve and combine with it, polluting the water.

Water, also known as a “universal solvent,” can dissolve more chemicals than any other liquid on the planet. It’s also the reason why water gets easily polluted.

Water pollution
Water pollution

Water Pollutants Sources

The sources of water pollutants belong to two categories.

  • Point Source Water Pollutants
  • Non-Point source Water Pollutants

Point Source Water Pollutants

Point source water pollution occurs when contamination arises from a single source. Examples of point source water pollutants include contamination from leaking septic systems, chemical and oil spills, effluent released illegally by an oil refinery, or wastewater treatment plant . While point source water pollutants originate in a single location, it has the potential to pollute miles of streams and the ocean.

Non-Point Source Water Pollutants

Water Pollutants arising from dispersed sources is referred to as non point source water pollutants. Agricultural or storm water runoff, pond ash from ash dykes, as well as debris blown into streams from land, are examples. Above all, it’s tough to control because there’s no single, recognisable source.

Water Pollutants Types

Water Pollutants are classified into nine types as shown below.

  • Oxygen Demanding Wastes
  • Disease-causing Agents
  • Synthetic Organic Compounds
  • Plant Nutrients
  • Inorganic Chemicals and Minerals
  • Sediments
  • Radioactive Substances
  • Thermal Discharges
  • Oil

Oxygen Demanding Wastes

  • Organic wastes which demand a high amount of dissolved oxygen for their microbial decomposition are referred to as oxygen demanding wastes.
  • Such kind of organic wastes arises from sewage, food processing plants, tanning operations etc.
  • Biochemical Oxygen Demand or BOD measures the water pollution potential of the organic waste.
  • The amount of dissolved oxygen (DO) required by aerobic biological organisms to decompose the organic waste present in a given water sample at a particular temperature over a given time period is known as biochemical oxygen demand (BOD).
  • Oxygen demand is directly proportional to the organic waste concentration in the water.
  • In other words, the higher the BOD of the wastewater, the higher is the amount of oxygen required for the degradation of waste.
  • Oxygen demanding wastes pose a hazard to aquatic life by using up the dissolved oxygen in the water for its degradation.
Water pollution effects on aquatic life
Water pollution effects on aquatic life

Disease-causing Agents

Sewage and wastes from farms and industries like tanning and meat packaging industries carry pathogens into the water bodies. As a result, water contains bacteria which causes cholera, typhoid, amoebic dysentery and viruses responsible for polio, coxsackie fever. These pathogens enter the human body through drinking water and other activities.

Escherichia coli is a harmless bacteria found in high concentrations in human faeces. They are used to assess the hygienic quality of water. Since the coliforms usually travel together with the pathogens, a high concentration of E. coli indicates faecal contamination and the presence of pathogens.

Synthetic Organic Compounds

  • Pesticides, insecticides and herbicides used in the crop fields reach the water bodies via surface runoff from agricultural lands and stormwater.
  • The commonly used chlorinated pesticides include aldrin, dieldrin and DDT.
  • They are highly stable, volatile and soluble in fats and oils and they accumulate in the bodies of aquatic organisms.
  • Through biological magnification, it gets more concentrated from one trophic level to the next in the food chain.
  • Fishes and predatory birds are the victims of pesticide pollution. For instance, dieldrin affects the calcium metabolism in predatory birds and leads to thinning of their eggshells.
  • Through drinking water and consumption of fishes, pesticide residues enter the human body.
  • The surfactants present in detergents create foam in water bodies and hamper the oxygen absorption of water. And, higher levels of phosphate act as a plant nutrient and generate eutrophic conditions.

Plant Nutrients

  • Phosphates, nitrates and ammonia are the major plant nutrients. They find their way into water bodies via effluents from fertilizer, food and textile industries.
  • As the concentration of these nutrients increases in the water bodies, algae absorbs them and grows excessively, resulting in eutrophication.
  • The process through which a water body gets enriched in dissolved nutrients is known as eutrophication.
  • This leads to algal bloom and develops a green slime layer over the surface of the water.
  • Therefore, sunlight can’t reach the bottom of the water bodies and this hampers atmospheric reoxygenation.
  • After that, the algal growth dies down and its degradation results in anaerobic conditions.
  • An anaerobic bacterium, Clostridium botulinum can flourish in this environment. It secretes a powerful toxin, botulinum that kills the algae feeding birds and humans.
  • Nitrate enters the human body through drinking water. It forms a complex, methaemoglobin which reduces the oxygen-carrying capacity of the blood. This leads to a fatal condition called methaemoglobin anaemia or blue baby disease.

Inorganic Chemicals and Minerals

The water pollutants like inorganic salts, mineral acids, finely divided metals and metal compounds fall under the category of inorganic chemicals and minerals. Municipal and industrial wastewater and mine runoffs are the main sources of these pollutants. Sulphur and coal mining leads to acid mine drainage consisting of sulphuric acid and iron compounds. In addition to this, tanneries, textiles and coke oven operations release alkalies to the water bodies.

  • Cadmium, Chromium, Lead, Mercury and Silver are metals found in industrial wastewater that requires serious attention.
  • Effluents from chemical plants, electroplating and textiles generate cadmium. The use of cadmium contaminated water for irrigation may have been the reason for itai-itai disease in Japan.
  • Wastewaters from aluminium anodizing, paint and dye industries, ceramic and glass industry brings both trivalent and hexavalent chromium to the water bodies.
  • Lead is present in industrial effluents from battery manufacture, printing and painting operations. It is a cumulative poison and concentrates mainly on the bones.
  • The most toxic aquatic pollutant is mercury owing to its rapid methylation in the aquatic environment. It builds up in the food chain and reaches toxic levels at the top of the trophic level.
  • Severe mercury poisoning causes Minamata disease, a neurological disease. Industrial effluents from chlorine and caustic soda, fertilizers and pesticides are the main culprits of mercury pollution.
  • The main sources of silver in wastewater are electroplating and photographic operations.
Water Pollution by chemicals
Water Pollution by chemicals

Sediments

Soil, sand and mineral particles reaching the aquatic environment through floodwaters constitute the sediments. The presence of sediments increases the turbidity of water bodies. Therefore, sunlight can’t penetrate to the bottom and its availability to aquatic plants decreases. Moreover, they cause the thickening of fish gills and asphyxiation of the fish and sediments also destroy the spawning sites of fish on the river bed.

Radioactive Substances

The radioactive material used in industrial, medical, or scientific activities creates nuclear waste. Uranium and thorium mining and refining are also sources of nuclear waste. Radium is the most important radioactive waste product and is a health hazard in drinking water.

Thermal Discharges

  • Heat is a water pollutant because it reduces the capacity of water to carry dissolved oxygen and raises the rate of metabolism in fish.
  • The practice of releasing cooling water from power stations into rivers is a major source of heat since the released water can be up to 15 degrees Celsius warmer than naturally occurring water.
  • Firstly, some fish species, such as trout, cannot survive in water with very low dissolved oxygen levels. Secondly, their eggs will not hatch at temperatures higher than 14.5 degree Celsius.
  • Moreover, there is a decline in oxygen saturation percentage with the increase in temperature.
  • Due to the density difference, hot water forms a separate layer above cold water.
  • This prevents the reaeration of the cold water underneath, as it has no atmospheric contact.
  • Due to the normal biological activities in the lower layer, the Dissolved Oxygen level falls rapidly and generates anaerobic conditions.

Oil

Every year, nearly half of the estimated 1 million tonnes of oil that enters marine habitats comes from land-based sources such as factories, farms, and towns. In addition, oil can ooze out from the ocean’s depths and eroded sedimentary rocks. Since oil does not dissolve in water and instead forms a thick sludge, it suffocates fish and sticks to the feathers of marine birds, preventing them from flying. Also, it prevents photosynthetic aquatic plants from receiving sunlight.

water pollution
water pollution

To sum up, the concentration of pollutants in water can be reduced by treating the effluents. To know more about wastewater treatment methods, please check our blogs, Wastewater Treatment- Stages and Process full details.

Air Pollution, Environmental engineering

Air Pollution Control measures – Top 9 Air pollution control devices

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It’s the need of the hour to take measures for air pollution control and prevention since millions of Indians are constantly exposed to polluted air. For instance, they breathe up to 25 micrograms/cubic metre of the lethal, microscopic pollutant PM 2.5 on a 24-hour average. This is well above the World Health Organization’s (WHO) limit of 10 micrograms/cubic metre.

To begin with, let’s first look at the causes of air pollution.

Air Pollution Causes

Industrialisation and urbanisation have technologically upgraded our lives. But, they had some negative byproducts like degradation of the environment, air pollution etc. The air quality index in most of the metropolitan cities is alarmingly high. Let’s have a quick glimpse at some of the major causes of air pollution:

  • Emissions from Industries and Power Plants
  • Construction and Demolition
  • Mining
  • Vehicular Emissions
  • Burning of waste and stubble

If you wish to dig deeper into the causes of air pollution, please check our blog Air Pollution Causes – A Comprehensive Guide

 If we can prevent the release of toxic gases by removing them from the flue gas stream or converting it into harmless compounds, we can control air pollution to a great extent. Similarly, if we can collect the dust and dispose of it properly, we can avoid particulate pollution. 

Also read: Air Pollution Effects and Causes – A complete overview

Air Pollution Control Measures and Devices

Air pollution control equipment refers to devices and facilities used in industries to control and prevent the emission of particulate matter and toxic gases. Fans or blowers direct industrial emissions and pollutants into air pollution control equipment and systems. Subsequently, they eliminate or reduce air pollutants using one or more of the following procedures:

  • Combustion i.e., destroying the pollutant.
  • Conversion i.e., chemical conversion of the pollutant to a less harmful compound.
  • Collection i.e., removal of the pollutant from stack gas before releasing into the atmosphere.

Having understood the basic mechanism of pollution control devices, let’s have a closer look at each of the devices.

Scrubbers

  • Scrubbers are the most widely used air pollution control devices in production and manufacturing facilities.
  • They use a physical process called scrubbing to remove particulates and gases from industrial emissions before releasing them into the atmosphere.
  • Scrubbers are of two types: dry scrubbers and wet scrubbers.
Industrial air scrubber- Air pollution control device
Industrial air scrubber- Air pollution control device

Dry Scrubbers

  • Dry scrubbers inject dry, neutralising chemical agents such as sodium bicarbonate into the exhaust stream.
  • Subsequently, the gaseous pollutants undergo a chemical reaction that either neutralises or transforms the pollutants into harmless compounds.
  • When the chemical reaction is finished, the expended agents are collected and removed from the cleansed emission gas by filters within the scrubber chamber.
  • Dry scrubbers are typically used to neutralise acid gas in oil refineries, wastewater treatment plants and metallurgical plants

Wet Scrubbers

  • Also known as wet adsorption scrubbers or wet collectors.
  • Wet scrubbers capture and remove water-soluble gas and particulate emissions from industrial emissions using liquid solutions—typically water.
  • A gas stream is passed through a liquid solution or a liquid solution is injected into a gas stream in the wet scrubbing process.
  • The solution on coming in contact with the gas stream absorbs the pollutant.
  • This process eliminates the pollutants from the gas and clean gas is released into the atmosphere.
  • The types of wet scrubbers include venturi, packed bed and bubbling scrubbers.
  • Flue gas desulphurisation employs wet scrubbing with a slurry of alkaline sorbent, usually limestone or lime.

Air Filters

  • Air filters are air pollution control systems that use a certain type of filtration media such as fabric, sintered metal, ceramic, etc.
  • They capture and remove dry particles and contaminants from air passing through them, such as dust, pollen, microorganisms, chemicals, and so on.
  • These devices remove pollutants from exhaust air and enhance the air quality in residential, commercial, and industrial buildings.
  • There are various types of air filters available for industrial purposes, including HEPA filters, fabric filters, and cartridge dust collectors.

Bag Filters

  • Also known as baghouses or fabric filters.
  • The bag filter uses cylindrical fabric bags to trap and remove dust and other pollutants in the air.
  • Particulates aggregate on the filter’s surface as the polluted air travels through a baghouse.
  • This particle buildup improves the filter’s efficiency by reducing the surface area of openings.
  • This allows even smaller particles to be collected.
  • Fabric filters usually offer collection efficiencies exceeding 99.9%.
  • These filters find wide applications in industrial processes, such as power plants, metal processing centres, and foundries.

Periodic cleaning is crucial due to continuous dust accumulation and the associated pressure differential. Baghouses use a variety of methods to remove the accumulation from the filter bags, including:

  • Shaking the filter bags.
  • Increasing the air pressure on the bag such that the bag collapses or deforms and dislodges the accumulated dust. 

Particulates fall from the filter cloth to the bottom of the baghouse enclosure into a collection hopper for processing and disposal.

Bag Filter
Bag Filter

HEPA Filters

  • Also known as high-efficiency particulate air filters.
  • These filters use fibreglass filter mats to physically remove airborne particulates like pollen, smoke, dust, and bio-contaminants from the workspace.
  • Fibres in fibreglass filter mats typically range in size from 0.5 to 2 metres.
  • According to the US Department of Energy (DOE), a filtering system maintaining a 99.97% efficiency for collecting particulates more than or equal to 0.3 m in diameter can be designated as a HEPA filter.
  • Widely used in pharmaceuticals, computer and electronics manufacturing, aerospace applications and nuclear power plants.
HEPA Air filters
HEPA Air filters

Cyclones – Air pollution control measures

  • Cyclones, also known as cyclone dust collectors, are air pollution control equipment that collects and remove particulates using centrifugal force.
  • When gas streams enter a cyclone, they spiral around the cylindrical chamber.
  • The centrifugal force experienced by the spinning gas stream is considerably higher than gravity.
  • Hence the centrifugal force throws the larger particles against the chamber wall, slowing their inertia and forcing them to fall into the collection hopper below.
  • The treated gas streams proceed upward and out of the cyclone.

The separation factor of a cyclone is defined as the ratio of centrifugal force to gravitational force. The higher the separation factor, the better is the cyclone performance. 

Electrostatic Precipitators

  • Electrostatic precipitators (ESPs), like air filters and cyclones, collect and remove particulate matter, such as dust, from industrial emissions and exhaust.
  • ESPs establish a large static electrical potential difference between charging electrodes and collecting plates, using transformers.
  • At very high DC voltages of the order of 50 kV a corona discharge adjacent to the negative electrode.
  • This creates an electric field between the positively charged collecting surface and the emitter.
  • Consequently, the electric field ionises the dust particles as the particle-laden gas flows upwards.
  • The electrostatic force directs ionised particles towards the grounded plates.
  • Particulate Matter deposit is periodically removed from the collecting plates and dumped in a collection hopper below.
  • Wet ESPs uses water to rinse off the dust particles.
  • ESPs’ efficiency reaches 99% since they have several collection plates.
  • The Deutsch equation gives the collection efficiency of an ESP.
Electrostatic Precipitator (ESP)
Electrostatic Precipitator (ESP)

Mist Collectors

  • Also known as mist or moisture eliminator filters.
  • These air pollution control devices remove moisture and vapour from gas streams, such as smoke, oil, mist, etc.
  • Fine mesh-like filters separate liquid droplets from gas and collect them in a separate chamber.
  • Finds wide applications in food and chemical processing, desalination plants, paper and pulp mills etc.
  • For submicron liquid particles, mist collectors have exceptional filtering efficiencies, with some collectors offering 99.9% efficiency for particles 0.3 μm in diameter.

Shall we wrap up?

Conclusion – Air pollution control Measures

In this blog, we saw some air pollution control measures and For the effective control of air pollution, the National Green Tribunal and the pollution control boards should strictly monitor and ensure the usage of these devices in the industries. We are still in need of green technologies like solar cells for power generation instead of coal-fired power stations, clean coal technologies, electric vehicles etc. Together, it is possible to reduce and control air pollution for a green future.

Air Pollution, Environmental engineering

What are air pollutants? | Types,sources and effects of air pollution

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Most of the times you can’t see it or smell it, but air pollutants kill. As the level of air pollutants in our atmosphere are rising at an alarming rate we must be aware of them. In the previous blogs, we had described the causes and effects of air pollution. Today let’s dive deep into various air pollutants.

Let’s get started.

What are Air Pollutants ?

Air pollutants are substances that can contaminate the air and are hazardous to human and other living species’ health. They can be either primary pollutants like dust, smoke, ammonia etc that are emitted directly from their sources or secondary pollutants.

Secondary Pollutants are formed in the atmosphere by chemical reactions between primary pollutants and the other atmospheric constituents. The common examples include ozone, sulphur trioxide, Peroxy Acetyl Nitrate (PAN), ketones etc.

Air Pollutants Types

The Environmental Protection Agency regulates three types of pollutants:

  • Criteria air pollutants
  • Air Toxics
  • Greenhouse Gases

Criteria air pollutants

Criteria Air pollutants include Particulate matter (PM), photochemical oxidants (e.g., ozone), carbon monoxide, sulphur oxide, nitrogen oxide, and lead. They can have a significant impact on public health and wellbeing, the atmosphere and environment, and neighbouring structures.

Air Toxics

The term “air toxics” consists of a list of over 180 air pollutants such as organic chemicals, volatile organic compounds (VOCs), metals, metal compounds, solvents, mercury, arsenic, asbestos, and benzene etc. Even when existent in trace amounts and emitted by fewer sources than criteria pollutants, they have harmful health and environmental impacts.

Greenhouse Gases

Greenhouse gases (GHGs) are gases such as carbon dioxide, chlorofluorocarbons (CFCs), methane, and ozone. They can harm human health. In addition, they contribute to the acceleration of the greenhouse effect on Earth and the resulting impact on global climate.

Major Air Pollutants – Sources and Effects

The sources of air pollutants can be natural or anthropogenic. Check out our previous blog Air Pollution Causes – A Comprehensive Guide for detailed information on various sources of pollutants. Let me describe each of the air pollutants in detail.

Nitrogen Oxides

  • Nitrogen oxides, notably nitrogen dioxide, are ejected from high-temperature combustion and created by electric discharge during thunderstorms.
  • This reddish-brown poisonous gas has a distinctive sharp, biting stench.
  • They appear as a brown haze above cities or as a plume downwind.
  • High levels of NO2 can irritate and inflame the lining of your airways.
  • This results in asthma or COPD flare-up, as well as symptoms like coughing and difficulty in breathing.

Carbon Monoxide

  • CO is a poisonous gas that is colourless and odourless.
  • It causes a smog-like buildup in the air.
  • CO reacts with haemoglobin in the blood to generate carboxyhaemoglobin when inhaled.
  • CO has a 200-fold higher affinity for haemoglobin than oxygen.
  • The tissues are deprived of oxygen as a result of this situation.
  • When carboxyhaemoglobin saturation levels are about 20%, it affects the heart and destroys tissues by preventing oxygen from reaching them.
  • This has been related to a variety of pulmonary ailments as well as environmental problems.

Sulphur Oxides

  • Sulphur compounds are common in coal and petroleum, and their combustion produces sulphur dioxide.
  • Further oxidation of SO2, usually in the presence of a catalyst like NO2, produces H2SO4, which results in acid rain.
  • It also arises from chemical, paper, and fuel manufacturing plants.
  • People with asthma or emphysema may find it more difficult to breathe after being exposed to sulphur dioxide.
  • It can also irritate the eyes, noses, and throats of people exposed to it.
  • Sulphur dioxide can injure trees and crops, cause structural damage, and impair people’s ability to see over long distances.
sulphur dioxide Pollution- Petroleum refinery
sulphur dioxide Pollution- Petroleum refinery

Volatile Organic Compounds

  • Compounds with high vapour pressure and low water solubility are known as volatile organic compounds.
  • VOCs are man-made substances that are utilised and created in the production of paints, medicines, and refrigerants.
  • Industrial solvents, such as trichloroethylene; fuel oxygenates, such as methyl tert-butyl ether (MTBE); or chlorination by-products, such as chloroform, are examples of VOCs.
  • The aromatic non-methane VOCs such as benzene, toluene, and xylene are suspected carcinogens. They can cause leukaemia in those who are exposed to them for a long time. 

Carbon Dioxide

  • The major greenhouse gas emitted by human activity is carbon dioxide.
  • Fossil fuel combustion, industrial emissions, wildfire etc. are the main sources of CO2 emissions.
  • It traps the solar radiations reflecting from Earth and increases the average temperature of Earth.
  • Due to its contribution to the greenhouse effect and climate change, it is often called the worst climate pollutant
  • It reaches the Earth’s surface as acid rain.

Particulate Matter

Fine particles, also known as atmospheric particulate matter, are microscopic solid or liquid particles suspended in a gas. Volcanoes, dust storms, forest and grassland fires, and sea spray are all sources of particulate matter. Particulate pollution comprises the following:

PM10:  inhalable particles with a diameter of 10 micrometres or less.

Can you imagine how small is 2.5 micrometre? Consider a single hair on your head. The average human hair is 70 micrometres in diameter, which is 30 times the size of the smallest microscopic particle. I hope this makes it clear how they penetrate deep into our lungs.

Aerosols

Aerosols are produced by human activities such as the combustion of fossil fuels in automobiles, power plants, and numerous industrial processes. Anthropogenic aerosols, or those produced by human activity, currently make up around 10% of our atmosphere. Increased fine particle levels in the air have been related to health risks such as heart disease.

Chlorofluorocarbons

  • CFCs are gases emitted by air conditioners, freezers, aerosol sprays, and other similar devices.
  • CFCs reach the stratosphere after being released into the atmosphere.
  • They interact with other gases here, causing harm to the ozone layer.
  • This allows UV radiation to reach the earth’s surface, which are hazardous.
  • This can result in skin cancer, eye problems etc.
  • As a result, they are currently restricted from usage in products.
Air Conditioners - Source of Chlorofluorocarbons
Air Conditioners – Source of Chlorofluorocarbons

Ammonia

Ammonia is a gas that is emitted primarily by agricultural waste. As a precursor to foodstuffs and fertilisers, it contributes considerably to the nutritional demands of terrestrial species. It is both corrosive and toxic, despite its widespread use. Ammonia combines with nitrogen and sulphur oxides in the atmosphere to generate secondary pollutants.

Ozone 

  • Carbon monoxide (CO), methane (CH4), or other volatile organic compounds (VOCs) are oxidised in the presence of nitrogen oxides (NOx) and sunlight to form ozone.
  • As a result, ozone is most abundant in the summer.
  • Ground-level ozone is a primary component of photochemical smog.
  • It is a significant health hazard connected to breathing issues, asthma, deterioration of lung function, and respiratory disorders.
  • People with asthma may experience more frequent asthma attacks as a result of ozone exposure, as well as sore throats, coughing, and breathing difficulties.
  • It could potentially result in premature death. Plants and crops can be harmed by ozone.

Lead

Lead is a neurotoxin. It was earlier used in petrol as an antiknocking agent. The fine particles emitted through automobile exhausts reaches the lungs and settles down there. At higher levels in the blood, it interferes with haemoglobin production. This results in oxygen starvation and anaemia. Higher levels lead to behavioural disorders.

Cadmium

Cigarette smoking is the main contributor to cadmium in the atmosphere. It can cause hypertension, cardiovascular diseases, kidney and liver damage.

Cigarette Smoke - Source of Cadmium
Cigarette Smoke – Source of Cadmium

Nickel

Finely divided nickel can react with carbon monoxide and forms Nickel Carbonyl. It is also formed in cigarette smoke. When it reaches our lungs it breaks down and deposits finely divided nickel inside our lungs. This is the main cause of lung cancer.

Mercury

Mercury enters the aquatic systems and soil from the atmosphere through acid rain. The adverse effects of mercury poisoning include chromosomal aberrations, neurological damage and even death. It can damage the cerebellum and cortex of brain by penetrating the membranes separating bloodstream from the brain.

So, we had taken a quick trip understanding all the major air pollutants. In case of any doubts, feel free to ask in the comments.

Happy Learning!

Air Pollution, Environmental engineering

Air Quality Index in Delhi – AQI categories and Causes

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The air quality index (AQI) is a daily reporting index for air quality. According to the recently released IQAir AirVisual 2020 World Air Quality Report, India is home to 15 of the world’s 20 most polluted cities. Would you believe it if I say that a public emergency was declared after the air quality index in Delhi plunged to ‘severe plus’ levels of about 530? Read on to find more about the Delhi Air Quality Index and what were the causes of this extreme level of pollution. To understand the severity of air pollution in Delhi, we should first know about Air Quality Index and its categories. So let’s look into the details of AQI and its categories.

Air Quality Index

The air quality index (AQI) is a daily reporting index for air quality. It’s an indicator of how air pollution impacts one’s health over a short period. The AQI’s objective is to inform individuals about how local air quality affects their health. 

AQI disseminates the air quality information in real-time. It is necessary to be aware of daily levels of air pollution, especially for people who suffer from ailments related to exposure to air pollution.

The AQI is calculated by the Environmental Protection Agency (EPA) for five primary air pollutants for which national air quality guidelines have been set to protect public health. They are listed below:

  • Ground-level ozone
  • Particulate matter (PM2.5/PM10)
  • Carbon Monoxide
  • Sulphur dioxide
  • Nitrogen dioxide
Air pollution in delhi
Air pollution in delhi

The higher the Air Quality Index value, the more polluted the air is and the higher the health risks. For the past three decades, many developed countries has widely applied the principle of AQI.

Also Read : Air pollution Effects and Causes – A complete overview

How Air quality index (AQI) is calculated?

To report air quality, different countries use different point scales. For instance, the United States employs a 500-point scale, with a score of 0 to 50 deemed satisfactory. A rating of 301 to 500 is considered dangerous. India, too, uses the 500-point scale. 

Everyday air pollution monitors record the major contaminants’ concentrations. EPA-developed standard equations are used to translate these raw values into a separate AQI value for each pollutant (ground-level ozone, particle pollution, carbon monoxide, and sulphur dioxide and nitrogen dioxide). The highest of these AQI values gives the the AQI value for that day

Air pollution in delhi
Air pollution in delhi

Categories of Air Quality Index

Depending on the level of pollutants in the air and the health effects it can cause, AQI has the following categories.

  • Good (0 to 50) – Minimal Impact
  • Satisfactory (51 to 100) – In sensitive people, this may cause slight breathing difficulties.
  • Moderately Polluted (101 to 200) – May cause breathing difficulties in individuals with lung disorders such as asthma, as well as discomfort in persons with heart disease, children, and the elderly.
  • Poor (201 to 300) – May cause breathing issues in persons exposed for an extended period, as well as discomfort in persons who have heart ailments.
  • Very Poor (301–400) – May cause respiratory sickness in individuals exposed for an extended period. People with lung and heart issues may experience a stronger effect.
  • Severe (401-500) – May cause breathing problems in healthy persons, as well as major health problems in persons who have lung or heart diseases. Difficulties can arise even when engaging in light physical activity.
  • Severe Plus or Emergency ( Above 500 ) – Extremely high levels of air pollutants.

Goals of  Air Quality Index

Let’s have a look at the objectives of calculating the Air Quality Index.

  • Compare air quality conditions in various locations or cities.
  • It also aids in the detection of incorrect standards and insufficient monitoring programmes.
  • The Air Quality Index (AQI) helps to monitor the changes in air quality (improvement or degradation).
  • The Air Quality Index (AQI) provides information to the public regarding environmental conditions. Therefore it’s particularly beneficial for persons who have ailments that are intensified or triggered by air pollution.

Who is most vulnerable to air pollution?

  • People who suffer from lung disorders such as asthma, chronic bronchitis, and emphysema.
  • Teenagers, as well as children
  • People of all ages who exercise or work outdoor often
  • Even individuals who are healthy can be sensitive to certain pollutants like ozone.

Now, we are done with the basic information about AQI. Keeping this in mind, lets analyze the AQI in Delhi.

Air Quality Index in Delhi

According to the AQI report, PM2.5 (particulate matter) is the most prevalent pollutant in Delhi and its outskirts, consistently exceeding the standard. It was the second most polluted city in India, barely behind the number one most polluted city, Ghaziabad, with an exceptionally high value of 110.2 g/m3 for PM2.5. In addition, Delhi came in the fifth rank out of every city in the world.

For the past few years, the concentration of NO2 in the air ranges from high to critical as per the AQI values. Also, the pollution level of particulate matter (PM10) crosses the critical level every year.

Surprised about such drastic levels of pollutants? Well, I have the answer for how this had happened. Read on to find the main causes of air pollution in Delhi.

Air Pollution in Delhi – Causes

Following are the main causes which made Delhi the second most polluted city.

Stubble Burning

To begin with, agricultural stubble burning by farmers produces nearly 15% of Delhi’s air pollution during the winter months. Farmers in the neighbouring regions burn the stubble to clear land after the September harvest, which contributes to the poor air quality. This is accompanied by changes in the weather, such as lower wind speeds and less rain in the winter season. Thus the smog remains in the atmosphere persistently. 

Stubble burn - Reason for air pollution
Stubble burn – Reason for air pollution

Topographical Factors

Due to its location as well as how the wind and its direction deposits pollutants in the air, Delhi is at a significant disadvantage in terms of topography. Winds blowing towards Delhi bring enormous volumes of smoke and particulates from neighbouring states as well.

When winter arrives, these winds typically die down, trapping the accumulated pollutants in Delhi’s atmosphere. This has a bigger impact on pollution levels than one might think. A 2019 estimate claims that dust brought in by the winds amounted to 21.5% of the entire pollution in Delhi.

Also read : Air Pollution Meteorology and Plume Types

Construction Activities and Vehicular Emissions

In addition, construction activities contribute significantly to the city’s pollution burden. According to the Delhi Pollution Control Committee, dust from construction sites is responsible for 30% of air pollution in the city. A large number of cars in the city, many of which have problematic engines, emit massive amounts of smoke and haze. Thus, coating the city in soot and black carbon (BC). It is a form of carbon that is exceptionally hazardous to all living organisms. 

Air pollution due to construction activities
Air pollution due to construction activities

Industrial Emissions

The industrial sector is responsible for an estimated 18.6% of total air pollution in Delhi. The industries alone release hundreds to thousands of tonnes of pollutants into the atmosphere each year. It should come as no surprise that PM2.5 levels have reached 829.2 g/m3. This was more than 80 times the WHO’s (World Health Organization) recommended yearly level.

Now it’s time for some good news.

Conclusion

The National Green Tribunal is entrusted with delivering adequate and sustainable remedies in situations involving the protection of the environment, forest and pollution prevention. The Tribunal has authority over all civil matters involving significant environmental issues, including the implementation of any environmental legal right. It is playing a key role in bringing down pollution levels in Delhi.

The National Green Tribunal (NGT) ruled in 2015 that all diesel vehicles older than ten years will be prohibited from operating in Delhi-NCR. In 2017, the NGT issued an interim ban in Delhi on plastic bags having a thickness lesser than 50 microns. This was because they were causing animal deaths, blocking sewers, and polluting the environment.

Let’s hope that the National Green Tribunal along with the Delhi Pollution Control Board is able to bring positive changes in curbing Delhi’s air pollution. That’s it about Air Quality Index in Delhi. Let us know your opinions in the comments.

Air Pollution, Environmental engineering

Air Pollution Effects and Causes – A complete overview

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Air pollution is one of our era’s biggest scourges, not only because of the impact it causes on climate change but also because it influences public and individual health due to chronic illness and death. The effects of air pollution range from environmental effects like global warming to even financial and health effects like coma and death.

Here’s the truth. According to WHO figures, air pollution-related diseases claimed the lives of 6.5 million people globally in 2012. That’s more than HIV/AIDS, TB, and road accidents combined, accounting for 11.6% of all world deaths. Shocking, right?

In this blog, I will show you the different effects of air pollution in detail. Let’s get started with the classification of the effects.

Also read : Causes of Air Pollution

Classification of Air Pollution Effects

The adverse effects of air pollution can be divided into two classes.

Acute Effects

Acute effects of air pollution appear immediately upon short term exposure to the pollutants at relatively high concentrations.

Chronic Effects

Chronic effects don’t appear immediately, rather become evident only after long term exposure to low levels of air pollutants.

Air Pollution Effects on Environment

Not only does air pollution impair our health, but it also harms the environment in which we live. The following are the most significant environmental effects.

Air Pollution Effects
Global Warming

Global Warming 

One of the most alarming effects for scientists and environmentalists is likely global warming. The greenhouse effect, which is caused by the excessive emission of CO2 and methane into the atmosphere, causes global warming. 

Climate Change

Another effect of global warming is climate change. When the planet’s temperature rises, the typical climatic cycles are disrupted, accelerating the changes of these cycles noticeably.

Acid Rain

Sulphur dioxide (SO2) and nitrogen oxides (NOx) are two gases released into the atmosphere as a result of fossil fuel combustion. When those compounds build up in the atmosphere and react with water, they produce dilute nitric and sulphuric acid solutions. They mix with the rain and reaches the surface of Earth as acid rain.

Effects of Air Pollution - Smog
Effects of Air Pollution – Smog

Smog

  • The smog effect, sometimes known as the beret effect, occurs when a dense dark fog forms over cities and fields. This fog is made up of pollutants.
  • There are two varieties of smog: sulphurous smog and photochemical smog.
  • The smog of both forms is a result of industrial and urban activity.
  • When nitrogen oxides and volatile organic compounds (VOCs) combine with sunlight, photochemical smog is created, resulting in a brown cloud above cities.
  • Sulphurous smog, on the other hand, is mostly caused by the usage of coal in numerous industrial operations.

Deterioration of Crop Fields

  • The Earth’s surface is degraded by acid rain, climate change, and smog.
  • Polluted water and gases infiltrate into the ground, altering the soil’s makeup.
  • This has a direct impact on agriculture, as crop cycles change and the composition of the food we eat changes.
  • In India, it was reported in 2014 that air pollution from black carbon and ground-level ozone had cut crop yields in the most impacted areas by nearly half in 2011 compared to 1980 levels in the most afflicted districts.

Extinction of animals

  • Many animal species that rely on oceans and rivers for existence are threatened as the poles’ ice melts and sea levels rise.
  • Because currents, ocean temperatures, and migratory cycles fluctuate, many creatures are driven to seek food in unfamiliar environments.
  • Ecosystems and habitats are also disappearing as a result of deforestation and low soil quality. And, without a doubt, this leads to the extinction of many wild animals.

Deterioration of construction materials

Because air pollutants degrade and modify the composition of building materials, many structures and infrastructure are weakened, degraded, or destroyed at a faster rate over time. The air pollution has been turning the Taj Mahal yellow-brown.

Destroys Vegetation

The pollutants penetrate the inner leaf tissues through stomata and destroy the chlorophyll. This disrupts photosynthesis. The damages caused ranges from chlorosis, necrosis, epinasty to the death of the plant. Cement dust deposits along with mist or rain cause incrustations in the leaves. 

Air Pollution Effects on Materials

Pollutants in the air have the following effects on materials, resulting in economic losses.

  • Abrasion
  • Materials deposition
  • Chemical attack 
  • Corrosion 

Sulphuric Acid mist in the atmosphere leads to the deterioration of structural materials like marble and limestone. Leather readily absorbs sulphur dioxide and gets disintegrated. Ozone causes the weathering of fabrics like acetate, cotton, nylon and polyester. At atmospheric levels of 0.01 to 0.02 ppm, it can cause the cracking of synthetic rubber. Particulates erode the exposed surface of materials and accelerate their corrosion.

Air Pollution Effects on Human Health

Air pollution has a variety of negative health consequences. Even on days when air pollution is low, vulnerable and sensitive people’s health can be harmed. COPD (Chronic Obstructive Pulmonary Disorders), cough, shortness of breath, wheezing, asthma, and respiratory disease are all linked to short-term exposure to air pollution.

Let me describe the health effects caused by each of the major air pollutants.

Oxides of Sulphur

  • When people are exposed to an atmosphere with sulphur dioxide concentrations above permissible levels, they get respiratory ailments.
  • At higher temperatures, their visibility is also affected.
  • Even at low concentrations of 1.6 ppm, it can cause bronchoconstriction in healthy individuals.
  • At higher concentrations, it leads to throat and eye irritation and immediate coughing. 

Carbon Monoxide

  • Carbon monoxide is released as a result of incomplete combustion of fuels in petrol engines, industrial operations, and other sources.
  • When CO is inhaled it mixes with the haemoglobin in the blood and forms carboxyhaemoglobin.
  • The affinity of CO towards haemoglobin is 200 times that of oxygen.
  • This condition deprives the tissues of oxygen.
  • When carboxyhaemoglobin saturation levels are about 20%, it affects the heart and also damages tissues by restricting oxygen.
  • Since the blood supply to vital organs including the brain is obstructed it can lead to mental impairment, visual acuity and even fatal coma at higher COHb levels in the blood. 

Oxides of Nitrogen

When NO2 is inhaled it reaches the moist alveoli of the lungs. There it is converted to nitrous and nitric acids which are highly irritating. They can damage the lung tissues. Long term exposure leads to symptoms resembling emphysema and biochemical alterations in blood.

Particulate Matter

  • Particulate matter of size less than 0.5 micrometres gets deposited in the alveoli and damage the respiratory tissues.
  • They can also act as carriers of toxic gases such as SO2 and produce synergistic effects.
  • Long-term exposure to PM2.5 raises the risk of non-accidental mortality by 6% for every 10 micrograms/m3 increase in concentration.
  • PM2.5 exposure was also linked to an elevated risk of lung cancer mortality ranging from 15% to 21% per 10 micrograms/m3 increase.

Shall we wrap up?

Conclusion

To sum up, air pollution affects not only humans but also our mother nature and other living beings. The effects of air pollution include environmental, economical and health effects. So it’s our responsibility to keep air pollution in check for a better tomorrow.