An air pollutant can be considered as a substance in the air that, in high enough concentrations, produces a detrimental environmental effect. An environmental effect is defined as a measurable or perceivable detrimental change resulting from contact with an air pollutant.Ambient air is the air towhich the general public hasaccess, i.e. any unconfinedportion of the atmosphere.
The two basic physical forms of airpollutants are • Particulate Matter • GasesParticulate Matter includes small solid andliquid particles such as dust, smoke, sand,pollen, mist and fly ash.Gases include substances such as carbonmonoxide (CO), sulfur dioxide (SO2),nitrogen oxides (NO2), and volatile organiccompounds (VOCs).
A primary pollutant is onethat is emitted into theatmosphere directly from thesource of the pollutant andretains the same chemicalform. A secondary pollutant is one that is formed by atmospheric reactions of precursor or primary emissions. Secondary pollutants undergo a chemical change once they reach the atmosphere.
Man Made Sources (Anthropogenic)Mobile Sources • Automobiles • Trains • Aeroplanes Stationary Sources (Non Moving Sources) • Power Plants • Industrial Facilities
Point SourceA point source refers to a source ata fixed pointArea SourceAn area source refers to a series ofsmall sources that together can affectair quality in a region.
Criteria pollutants • common • detrimental to human welfare These criteria pollutants are • Carbon Monoxide (CO) • Sulfur Oxides (SOx) • Nitrogen Oxides (NOx) • Ozone (O3) • Lead (Pb) • Particulate Matter (PM)
Criteria PollutantsCarbon Monoxide• colorless odorless gas• formed when fuel is not burnt completelySources • 50-60% produced by motor vehicles • Heavy construction equipment • max at heavy traffic congestions • forest fires (Natural) • Industrial processes • Gas stoves, wood stoves, heaters, cigarettes
Criteria PollutantsSulfur Oxides (SOx)• colorless gases• formed by burning sulfur• fuel, oil or gas containing sulfur is burnt• SO2 criteria pollutant• SO2 dissolves in water to form acids• SO2 interacts with other gases &particles to form sulfates (harmful)Sources • Power Plants running on furnace oil rich in sulfur • Industrial facilities • Oil refineries • Large ships, non road diesel equipment
Criteria PollutantsNitrogen Oxides (Nox)• mostly colorless, odorless• NO, NO2, N2O• NO2 criteria pollutant• highly reactive gases• play an important role in the formation of ozone• formed when fuel is burnt at high temp.• NO2 along with other particles forms a brownish layerSources • Motor vehicles • Industrial activities • Electric utilities
Criteria PollutantsOzone (O3)• gas composed of three oxygen atoms• colorless gas, electric discharge type odor• secondary pollutant• not emitted directly into the air• at ground level, created by a chemical reac.b/w Nox and VOCs in sunlight and heatGood Ozone • Stratospheric ozone protects us from harmful ultraviolet radiations Bad Ozone • ground level ozone harmful to humans and environment
Criteria PollutantsFactors affecting Ozone concentration • concentration of VOCs • concentration of NOx • local weather conditions • intensity of sunlight
Criteria PollutantsParticulate Matter (TSP, PM10, PM2.5)• mixture of solid particles and liquiddroplets• includes dust, soot, smoke and liquiddroplets• can be primary as well as secondarypollutant• can remain suspended in air for long periodof timePM10 • all particles less than or equal to 10µm in diameter (one seventh the dia. Of human hair PM2.5 • all particles less than or equal to 2.5µm in dia
Criteria PollutantsLead (Pb)• metallic element• found naturally in environmentSources • vehicular emissions • industrial processes • lead batteries • leaded gasoline • battery manufacturers • metal refineries • iron and steel producers
Table 1: Sources, Health and Welfare Effects for Criteria Pollutants. Pollutant Description Sources Health Effects Welfare EffectsCarbon Monoxide (CO) Colorless, odorless gas Motor vehicle exhaust, Headaches, reduced Contribute to the indoor sources include mental alertness, heart formation of smog. kerosene or wood burning attack, cardiovascular stoves. diseases, impaired fetal development, death.Sulfur Dioxide (SO2) Colorless gas that Coal-fired power plants, Eye irritation, wheezing, Contribute to the dissolves in water vapor petroleum refineries, chest tightness, shortness formation of acid rain, to form acid, and interact manufacture of sulfuric of breath, lung damage. visibility impairment, with other gases and acid and smelting of ores plant and water damage, particles in the air. containing sulfur. aesthetic damage.Nitrogen Dioxide (NO2) Reddish brown, highly Motor vehicles, electric Susceptibility to Contribute to the reactive gas. utilities, and other respiratory infections, formation of smog, acid industrial, commercial, irritation of the lung and rain, water quality and residential sources respiratory symptoms deterioration, global that burn fuels. (e.g., cough, chest pain, warming, and visibility difficulty breathing). impairment.Ozone (O3) Gaseous pollutant when it Vehicle exhaust and Eye and throat irritation, Plant and ecosystem is formed in the certain other fumes. coughing, respiratory damage. troposphere. Formed from other air tract problems, asthma, pollutants in the presence lung damage. of sunlight.Lead (Pb) Metallic element Metal refineries, lead Anemia, high blood Affects animals and smelters, battery pressure, brain and plants, affects aquatic manufacturers, iron and kidney damage, ecosystems. steel producers. neurological disorders, cancer, lowered IQ.Particulate Matter (PM) Very small particles of Diesel engines, power Eye irritation, asthma, Visibility impairment, soot, dust, or other matter, plants, industries, bronchitis, lung damage, atmospheric deposition, including tiny droplets of windblown dust, wood cancer, heavy metal aesthetic damage. liquids. stoves. poisoning, cardiovascular effects.
Mobiles Sources • responsible for more than half of the air pollution • cars are primary source • vehicles produce 75-90% less pollution for each mile driven than their 1970 counterpart • no. of vehicles have increased immenselyMobile Sources Pollutants • 45% VOC emissions • 50% NOx emissions • 60% CO emissions • 50% hazardous air pollutants in urban air
Air Quality IndexThe Air Quality Index (AQI), also known asthe Air Pollution Index (API) or PollutantStandard Index (PSI) is an index forreporting daily air qualityHow does the AQI work?Think of the AQI as a yardstick that runsfrom 0 to 500. The higher the AQI value, thegreater the level of air pollution and thegreater the health concernAn AQI value of 100 generally corresponds tothe national air quality standard for thepollutant, which is the level EPA has set toprotect public health
Air Quality Index NumericalLevels of Health Concern Meaning Value Air quality is considered satisfactory, Good 0-50 and air pollution poses little or no risk. Air quality is acceptable; however, for some pollutants there may be a Moderate 51-100 moderate health concern for a very small number of people who are unusually sensitive to air pollution. Members of sensitive groups may Unhealthy for 101-150 experience health effects. The general Sensitive Groups public is not likely to be affected. Everyone may begin to experience health effects; members of sensitive Unhealthy 151-200 groups may experience more serious health effects. Health alert: everyone may Very Unhealthy 201-300 experience more serious health effects. Health warnings of emergency Hazardous > 300 conditions. The entire population is more likely to be affected.
To convert from concentration the equationis used, where:I = the (Air Quality) index,C = the pollutant concentration,Clow= the concentration breakpoint that is ≤ C,Chigh= the concentration breakpoint that is ≥ C,Ilow= the index breakpoint corresponding to Clow,Ihigh= the index breakpoint corresponding to Chigh.
For example, suppose a monitor records a 24-houraverage fine particle (PM2.5) concentration of 12.0micrograms per cubic meter. EPAs table ofbreakpoints for PM2.5 is: Clow Chigh Ilow Ihigh Category 0 15.4 0 50 Good 15.5 40.4 51 100 Moderate Unhealthy for 40.5 65.4 101 150 Sensitive Groups 65.5 150.4 151 200 Unhealthy 150.5 250.4 201 300 Very Unhealthy 250.5 350.4 301 400 Hazardous 350.5 500.4 401 500 HazardousThe equation above results in an AQI of:corresponding to air quality in the "Good" range.If multiple pollutants are measured at a monitoringsite, then the largest or "dominant" AQI value isreported for the location
Particulate Matter Sampling Numbering of filters Filter drying and conditioning Filter (200C, 50% R.H), 24 hrsPreparation Weighing (before) by balance Filter setting to the sampler Perform Sampling 24 hrs Sampling Remove and collect the filter sample Sample drying and Sample conditioning (200C, 50% R.H),Measurement 48 hrs Weighing (after) by balance Calculate the concentration and store the sample
CalculationsInitial wt. of filter paper Wi= ----- gWt. of filter paper + particulate matter Wf= ------ gWt. of Particulate matter W= (Wf – Wi) X 106 µgAvg. flow rate over the entire duration of samplingperiod Qavg= ----- L/minDuration of the sampling period t= ----- minTotal sample volume V= Qavg X t X 10-3 m3Concentration of particulate matter PM 10/2.5 C = W / V = ----- µg/m3
SamplePreparation for HCl (1+1) 30mLMetal Analysis H2O2 (30%) 5mLof HV Filter 120 C, 1Hr in a draft chamberSamples Funnel / Whatman 41 Filter Paper soon before dry up HNO3 (2+98) after cooling HNO3 (2+98) Polyethylene Bottle
Calculation of Lead Concentration in Air (AAS) C= (c1-cb) X v X (S/s) / Vo (µg/m3)wherec1: Pb concentration in the solution of samplecb:Pb concentration in the solution of blankfilter (µg/mL)v: Sample solution volume (25 mL)S/s: Ratio of Sampled filtered area by theanalyzed areaVo: Sampling air volume at standard cond. Vo = V X 298 / T (m3)V: Sampling air volume at present state (m3)T: Average Temperature during sampling (K)
Acid Rain / Acid DepositionAcid deposition occurs when emissions ofsulfur dioxide and nitrogen oxides in theatmosphere react with water, oxygen, andoxidants to form acidic compoundsThese compounds fall to the earth in eitherdry form (gas and particles) known as DryDeposition or wet form (rain, snow, and fog)known as Wet DepositionDuration of the reactionIt takes days or weeks for atmospheric SOxand NOx to be converted to acids anddeposited on the earths surface, aciddeposition occurs in a multistate scalehundreds of miles away from its sources
SmogSmog is thick, choking,dangerous. It happens whentiny particles of dust, smokeand dangerous gases likesulfur dioxide mix withwater vapor. And it’s noaccident: it is all carefullymanufactured by one species– human beings!
Dispersion of Air PollutantsConingA coning plume occurs under essentially neutralstability, when environmental lapse rate is equalto adiabatic lapse rate, and moderate to strongwinds occur. The plume enlarges in the shape ofa cone. A major part of pollution may be carriedfairly far downwind before reaching ground.
Dispersion of Air PollutantsLoopingUnder super-adiabatic condition, both upwardand downwind movement of the plume ispossible. Large eddies of a strong wind causeslooping pattern. Although large eddies tend todisperse pollutants over a wide region, highground level concentrations may occur close tothe stack.
Dispersion of Air PollutantsFanningA fanning plume occurs in the presence of anegative lapse rate when vertical dispersionis restricted. The pollutants disperse at thestack height, horizontally in the form of afanning plume.
Dispersion of Air PollutantsLoftingWhen the stack is sufficiently high and theemission is above an inversion layer, mixing inupper layer is uninhibited, but downwardmotion is restricted. Such lofting plumes donot result in any significant concentration atground level. However, the pollutants arecarried hundreds of kilometers from thesource.
Dispersion of Air PollutantsFumigationWhen the emission from a stack is under aninversion layer, the movement of the pollutantin the upward direction is restricted. Thepollutants move downwards. The resultingfumigation can lead to a high ground levelconcentration downwind of the stack.
Inversion Layer In meteorology, the atmospheric layer in which the usual temperature gradient— warm air below cold air— is reversed, preventing the mixing of warm and cold air as the warmer air rises. This traps dangerous concentrations of pollutants in the cool air below, sometimes causing dense smog over urban areas.
NEQS for Ambient AirStandards for theminimum ambient airquality needed to protectpublic health and welfarewhich are applicable tothe ambient air all overPakistan
National Environmental QualityStandards NEQS for Ambient Air Pollutants Time-weighted Concentration in average Ambient Air Effective from 1st January, 2009 Sulfur Dioxide Annual Average 80 µg/m3 24 hour 120 µg/m3Oxides of Nitrogen as Annual Average 40 µg/m3 NO 24 hour 40 µg/m3Oxides of Nitrogen as Annual Average 40 µg/m3 NO 24 hour 80 µg/m3 Ozone 1 hour 180 µg/m3Suspended Particulate Annual Average 400 µg/m3 Matter 24 hour 550 µg/m3 SPM Particulate Matter Annual Average 200 µg/m3 PM10 24 hour 250 µg/m3 Particulate Matter Annual Average 25 µg/m3 PM2.5 24 hour 40 µg/m3 1 hour 25 µg/m3 Lead (Pb) Annual Average 1.5 µg/m3 24 hour 2.0 µg/m3Carbon Monoxide (CO) 8 hour 5 mg/m3 1 hour 10 mg/m3
Attainment Area / Non-Attainment AreaAttainment AreaAn area considered to have air quality as goodas or better than the National EnvironmentalQuality Standards as defined in the draft byPak-EPA.Non-Attainment AreaAn area that does not meet one or more of theNational Environmental Quality Standards asdefined in the draft.An area may be an attainment area for onepollutant and a non-attainment area forothers.
Tunnels concentrate AirPollution by upto 1,000 times