A BRIEF OVERVIEW OF THE PREVIOUS CLASS (1:15 PM)

WATER POLLUTION (1:20 PM)

• Any undesirable change in physical, chemical, or biological characteristics of air, land, water, or soil is called pollution
• The agents bringing the change are called pollutants
• Undesirable changes in the quality of water through the addition of undesirable substances or undesirable levels of existing compounds are called water pollution
• Source of water pollution

• Point Source	Non-Point Source
  It has a single identifiable source of pollution	There is no single identifiable source and the pollutants originate from a very wide area
  The pollutants enter the water bodies at specific locations directly from the source	The pollutants enter the water bodies at multiple locations from wide areas
  They can be regulated and monitored easily	They can not be regulated or monitored easily
  E.g. Industrial effluents, municipal sewage outlets, oil spills, etc.	E.g. Urban runoff, agricultural runoff, atmospheric deposition (like dried deposition of acid rain), etc.

• Impacts of some specific pollutants

• Pollutants	Impact
  Mercury	Minimata disease, dropsy (particularly in fish)
  Lead	Dyslexia
  Cadmium	Itai-Itai
  Fluoride	Fluorosis
  Arsenic	Black-foot disease
  Chromium	Allergies and asthma
  Nickle	skin issues, pneumonia
  Uranium	Cancer, kidney failure
  Iron	Skin issues
  Nitrate	Blue-baby syndrome

• Impacts of water pollution (1:54 PM)
• Decreased dissolved oxygen
• The amount of oxygen dissolved in the water is called dissolved oxygen
• It is measured in mg/liter
• A non-polluted water contains at least 8 mg/l of dissolved oxygen
• With pollution, oxygen demand increases
• Oxygen demand has an inverse relation with dissolved oxygen
• Oxygen demand can be classified into biochemical oxygen demand (BOD) and chemical oxygen demand (COD)
• Biochemical oxygen demand represents the amount of oxygen consumed by bacteria and other microorganisms to decompose biodegradable organic material present in the water under aerobic condition
• Chemical oxygen demand (COD): It is the amount of oxygen consumed to break down both biodegradable and non-biodegradable organic matter present in water through chemical oxidation process
• While COD measures oxygen demand for all organic matter, BOD measures only biodegradable organic matter, therefore, COD is always greater than BOD
• Both BOD and COD indicate the level of water pollution and harm to aquatic ecosystem
• Eutrophication
• The enrichment of water bodies with nutrients is called eutrophication
• It can be due to natural factors such as erosion, rainwater runoff, etc.
• It is a part of the natural aging process of water bodies
• The rapid increase in nutrients available due to anthropogenic factors is called cultural eutrophication
• Sources of eutrophication:
• 1. Excessive use of fertilizers particularly nitrogenous, phosphorus
• 2. Flood-irrigation method and agricultural runoff due to rainfall
• 3. Discharge of sewage water into water bodies
• 4. The release of industrial effluents
• 5. Urban runoff
• 6. Religious and cultural practices
• Impacts of eutrophication:
• 1. Increase in oxygen demand (both COD and BOD)
• 2. Decrease in dissolved oxygen
• 3. Large-scale growth of algae, water hyacinth, duckweeds, and various phytoplanktons
• 4. No. of species in the water bodies decreases due to low levels of oxygen and sunlight
• 5. Harmful algal blooms
• Reasons for algal blooms include an increase in water temperature, global warming, thermal pollution, and excessive uncontrolled eutrophication
• The impact of harmful algal bloom includes:
• 1. Very low levels of dissolved oxygen
• 2. Rapid decrease in other species and very low biodiversity
• 3. Large-scale fish kill
• 4. Discoloration of water with a foul smell making it unfit for use
• 5. Certain toxic microorganisms survive like Clostridium Botulinum
• 6. Increased pH level
• 7. Gradual emergence of dead zones or hypoxic condition
• Controlling eutrophication:
• 1. Stop the runoff and divert rain waters
• 2. Increase aeration and water movement
• 3. Remove blooms manually
• 4. Adding some artificial particles like clay which binds with algae and sinks
• Bioaccumulation and Biomagnification
• Bioaccumulation is the process through which the concentration of certain chemical substances increases continuously in the body tissues of an organism within a trophic level due to absorption from food and environment
• Biomagnification or bio-amplification is the process by which certain chemical substances become more concentrated in the body tissues of organisms as one moves up the food chain
• Properties of compounds suitable for biomagnification:
• 1. They are long-lived or don't decompose easily
• 2. They are persistent and cannot be disintegrated easily
• 3. They are water-insoluble
• A few examples include most heavy metals (e.g. lead, mercury, copper, cadmium, tin, etc.), cyanide compounds, and poly-nuclear aromatic hydrocarbons
• Impacts the nervous system and immune system, increases cancer risk, impacts fertility, child growth, and failure of eggs due to the thinning of eggshells in birds

AIR POLLUTION (3:29 PM)

• It refers to the release of pollutants into the air that are detrimental to human health and the ecosystem
• Primary Pollutants
• They are the air pollutants released directly from the source in the atmosphere
• For example, sulfur dioxide, carbon dioxide, etc.
• Secondary Pollutants
• They are not released directly from the source but are formed due to the reaction of primary pollutants in the atmosphere
• For example, smog, acid rain, etc.

• Pollutants	Sources	Harmful Impacts
  Carbon monoxide (CO)	Incomplete combustion of wood, biomass, coal, petroleum, etc.	Reduced oxygen levels in the blood (have an immediate impact on humans)
  Carbon dioxide (CO2)	Burning of any fossil fuel	Global warming, ocean acidification
  Oxides of sulfur, SOx (sulfur dioxide or SO2, hydrogen sulfide or H2S)	Thermal power plants, petroleum refineries, volcanic eruptions; decomposition releases H2S	Acid rain, respiratory issues, chlorosis (loss of chlorophyll pigment in plants)
  Oxides of nitrogen, NOx (nitric oxide NO, nitrous oxide N2O, nitrogen dioxide NO2)	Fossil fuels, fertilizers, denitrification, automobile exhausts	Acid rain, respiratory issues, eye irritation, reduced plant productivity
  Hydrocarbons (benzene and ethylene)	Burning of fuels	Respiratory issues, carcinogenic
  Particulate matter (PM)	Construction activities (demolition), stubble burning, industrial exhaust, automobile exhaust, waste burning, biomass burning, cement industries, spraying of chemicals in agricultural fields, textile and carpet industries, sandblasting	Respiratory diseases, headache, nausea, carcinogenic, reduced visibility resulting in the formation of smog
  Black carbon and brown carbon	Black carbon- High-temperature combustion in diesel engines, incomplete combustion in coal thermal power plant Brown carbon- burning of organic matter, cow dung	Greenhouse gases, they are particulate matter, impact the albedo of glaciers leading to faster melting

Topic for the next class: Air pollution (continued), Land degradation