Pollution PDF

What is Pollution ? Addition of any substance (solid, liquid or gas) or any form of energy (such as heat, sound, or radioactivity) to the environment at a rate faster than it can be dispersed, diluted, decomposed, recycled, or stored in some harmless form. Types: 1. Air Pollution 2. Water Poll...

What is Pollution ? Addition of any substance (solid, liquid or gas) or any form of energy (such as heat, sound, or radioactivity) to the environment at a rate faster than it can be dispersed, diluted, decomposed, recycled, or stored in some harmless form. Types: 1. Air Pollution 2. Water Pollution 3. Noise Pollution 4. Land Pollution Primary and secondary air pollutants Primary pollutants are air pollutants emitted directly from a source. E.g. Carbon monoxide (CO), Sulphur dioxide (SO2), oxides of nitrogen (NOx), Volatile organic compounds (VOCs), Particulate matter (some part like dust, black carbon) Secondary pollutants are air pollutants which are not directly emitted but are formed in the atmosphere when primary pollutants react with each other or undergo transformation in the absence/presence of sunlight. E.g. Ozone (formed from NOx and VOCs in the presence of sunlight), Particulate matter (nitrates, sulfates formed from NOx and SO2etc.) 2 Credit: Dr. Amit Sharma  3 Credit: Dr. Amit Sharma Criteria Pollutants Criteria pollutants are the commonly talked about pollutants as they are the indicators of air quality Include - Particulate matter (PM), Ground level ozone, CO, SO2, NO2 and lead (Pb) Source - http://www.alamoareampo.org/images/top-pics/pollutants.jpg 4 Credit: Dr. Amit Sharma Why ‘Criteria’ Pollutants? Pollutants are characterized as “Criteria Pollutants” (defined by EPA) because they are regulated by developing human health-based and /or environmental protection-based criteria for setting permissible limits. Primary standards: based on public health protection. Secondary standards: based on public welfare protection, including protection against environmental and property damage. 5 Credit: Dr. Amit Sharma  Pollutant Major sources of emission Removal Mechanism SO2 Fuel (coal) combustion, combustion of S-containing fuels Conversion to particulate (ships & non-road machinery); Industrial processes SO4 and removed by dry or (Petroleum refinery, cement, paper & Al); Volcanic wet deposition eruptions NOx Automobiles & fossil fuels combustion; Conversion to HNO3 and Natural fires and soil; Lightning and NH3 oxidation particulate NO3; Together with VOCs lead to O3 formation CO Automobiles; Combustion of coal, oil and wood; Forest Reaction with OH* to form fires and other type of smokes; Industrial activities; CH4 CO2 eventually; Soil uptake and NMHC oxidation Tropospheric O3 Photo-chemical reactions of VOCs and NOx; Global CH4 Oxidation reactions with oxidation; Stratospheric O3 intrusion other pollutants; Dry deposition Lead Gasoline; Paint; Smelting of metals; Coal burning Dry or wet deposition PM Agricultural practices; Dust storms; Fossil fuel Dry or wet deposition combustion; Industrial processes; Forest fires; Plant emissions, vehicles, secondary processes  Air Quality Index (AQI) Way to report daily Air Quality Inputs to AQI: 1. Reporting area 2. Reporting period 3. Critical pollutant (the pollutant with the highest AQI value) 4. AQI value 5. Category descriptor and color 6. Sensitive groups for all pollutants with an AQI over 100 https://aqicn.org/city/india/jodhpur/collectorate https://www.airnow.gov/sites/default/files/2020-05/aqi-technical-assistance-document-sept2018.pdf Air Quality Index (AQI)…Contd.. AQI>500; Stay Indoors and Reduce activity levels AQI Calculation Criteria Pollutants Most important out of the six pollutants are PM and ozone PM and Ozone known to significantly impact human health Ozone impact plants and agricultural crops Both have impact on climate Source - http://www.alamoareampo.org/images/top-pics/pollutants.jpg 12 Credit: Dr. Amit Sharma Ground level ozone Source - http://www.alamoareampo.org/images/top-pics/pollutants.jpg 13 Credit: Dr. Amit Sharma  Composition & Structure of Earth’s Atmosphere Troposphere: ❑ ~80% of total mass (most dense layer) due to Earth’s gravity ❑ Weather, Cloud formation, Turbulence and mixing, and Pollution ❑ Higher at equator and lower at poles (Temp., Gravity, Centrifugal force) Stratosphere: ❑ Contains O3 layer absorbing UV radiation === 45-55 Kms Warms the atmosphere ❑ Temperature increase with altitude ❑ O3 layer destruction by CFCs and N2O (Antarctica ozone hole in 1985) ❑ Montreal Protocol 1987 ❑ Some airplanes and jets fly low in the 10-15 Kms stratosphere to avoid turbulent weather in Free Troposphere Troposphere. < 1 Km Planetary boundary layer (PBL) Seinfeld and Pandis, 2016, Atmospheric Chemistry and Physics  Composition & Structure of Earth’s Atmosphere Mesosphere: ❑ Coldest layer: less solar heating, Rapid vertical mixing ❑ Meteors and comets fall on this layer and burn up due to friction with the air molecules. 80-90 Kms Thermosphere: ❑ Hottest layer; temperature increases with altitude up to 1000 °C ❑ Absorption of UV and X-rays ❑ Least dense layer ❑ Ionosphere is located in this layer consisting of charged particles and light gases (causing Aurora or 45-55 Kms Northern/Southern Lights from polar regions). Radiations interacting with ions. ❑ No clear boundary. Credit: google images Exosphere: ❑ > 500 Km altitude 10-15 Kms ❑ Merges with outer space. Free Troposphere ❑ Very few molecules with increase in altitude ❑ Contains lighter gases like H2 and He. Satellites < 1 Km Planetary boundary layer (PBL) Seinfeld and Pandis, 2016, Atmospheric Chemistry and Physics Ozone layer Ozone layer present in the stratosphere Stratospheric ozone formed from photolysis of oxygen by highly energetic ultra violet radiation (UV-C and UV-B) and then combination of oxygen atom with oxygen molecule Source - https://byjus.com/chemistry/wp-content/uploads/2015/12/Ozone-layer_1.jpg 16 Credit: Dr. Amit Sharma Stratospheric Ozone reactions O2 + ℎν (λ