 Alright, so maybe we should begin now with the fourth session of air quality. The learning objective for this module for students is that the students will be able to qualify air pollutants. So one part is to quantify, but then they will also be able to qualify. Just one thing to say air is polluted and maybe read in the newspapers or look at the, they've developed an air quality index which is now being used across the country, it will soon be implemented which will tell you in some sense health of the air. So if it is green means it's safe, maybe you can go out jogging, but if it's red then you know it's probably a good idea to stay indoors. So there's a whole range, there's a scale that has been developed for air quality index. Now that's good for citizens, for people who might be affected, people who are not necessarily engaged with the dealing of air quality or aren't professionals in the area of air quality or aren't students and teachers in the area of air quality. But for people who are engaged in the area of air quality as teachers, students, professionals it's not adequate to be able to say, okay I just need to know whether air is breathable or not, you actually need to be able to qualify. So with that said, there are two kinds of pollutants in the air, this is quite obvious, but for students to be able to say that smoke is particulate matter, dust is particulate matter, but oxides of nitrogen or H2S is gaseous in nature. So we will spend a little bit of time in making a distinction between these because the nature, the chemical engineering, the environmental engineering, the control engineering that's associated with these is very distinct. So when we say air pollutants, one of the first things we deal with is the concentration and I think on one of the earlier lectures we've already talked about the concentration of sulphur dioxide. So it is typically mass of pollutant in a certain volume of air, mass of pollutant, a particular pollutant in a certain volume of air. And when it comes to particles, you actually can do mass of particles or you can also do number of particles and we will get into the details of why the two could be different and just sometimes the mass concentration is not adequate to be able to fully represent the impact of different kinds of particles. The third one I've said opacity and that's the third bullet is the reason why I have put concentration as in inverted commas. We talked about opacity yesterday, we talked about the grayscale, I'd even attempted to crack a joke about fair and lovely and how they have this skin gradation, skin scale. So we have similar grayscale going from all the way from white to black and you put it against the smoke coming from a chimney and based on that you'll be able to say how bad is the pollution. But you know it's qualitative measure, it's not necessarily quantitative measure. Second aspect of the air pollutants is exposure, how many hours you are exposed and both of these actually come into the standards in the national ambient air quality standards. These come in, they come in both as concentration as well as exposure. So how much concentration will you oppose for how much time whether it's detrimental for you or it's healthy to breathe. The next thing I introduce to the students then is criteria pollutants. And the way I relate with it is that when you go to the doctor, normally the doctor will look at your body temperature, would look at your pulse rate and maybe put a stethoscope on your chest and those are the two, three things that a doctor would do to figure out the general state of your health. So that you know is a good criteria for health for a human body. So when we are looking at air quality, we don't want to get into the nitty gritty of every single molecule in the air because that will get too tedious and it will get too difficult to kind of understand. It's not that it's not required, it's required but when you get into diagnostics and you try to get into sources of the pollution etc etc then you do have to do some very rigorous chemistry. But for general purposes and as a general health of air, these are pollutants that are used to measure the criteria for quality. So they are oxides of sulphur, oxides of nitrogen, carbon monoxide, PM10, I will describe what PM10 means. It is basically particulate matter, particulate lead, these are all primary, primary meaning that they are emitted directly from a source. And there is a secondary pollutant which is ozone which is not directly emitted but is actually formed in the atmosphere. Now just ozone, ozone, ozone, ozone hole, ozone layer, lot of times students have this confusion. So I usually tell them that ozone which is above the troposphere in the stratosphere is good ozone. Thank God for that ozone otherwise life as we know it on the planet would not exist. That is the ozone which actually developed a hole, that is the one which we are trying to fill up now by eliminating use of certain compounds. But this ozone is at our nose level, it is at the level of us as receptors, it is at the level of we being exposed to it. This is not good ozone, this is bad for health. So but that is not really getting directly emitted from somewhere, it gets formed in the atmosphere through some atmospheric chemistry. So basically we are left with that as a secondary pollutant. Primary pollutants are usually coming from some human activity, typically. So if you are living in a city or if you are living in a village, if you are living in a small town, there is human activity and we want to know how much of an influence the human activity is having on the quality of the air. So for example, any diesel, any coal that is burnt has sulphur. So the sulphur dioxide would come from the sulphur there. Oxides of nitrogen, because you are using air for combustion, because you are using air for combustion and air has 78% nitrogen, that nitrogen at high temperatures would combine with oxygen to give oxides of nitrogen. So you have oxides of nitrogen coming from combustion also. Carbon monoxide, anytime there is combustion there will be carbon dioxide, but then if it is incomplete combustion, there will be carbon monoxide. So carbon monoxide also is a result of combustion. PM10 is particulate matter and particulate matter can come from various sources and we will discuss that in great detail today. Particulate lead is associated with the leaded petrol that used to be used, it is not there so much now. And the ban or the elimination of the use of leaded petrol has eliminated this particulate lead. There is not much talk about it anymore. However, one of the things I always ask the students is what did they do really? If they replace, if they remove the lead, tetraethyl lead, what did they do? I mean did the engine design suddenly become such that knocking is no more a problem or are we using a fuel which is doing the same job in the additive as lead was doing? And the answer is that some other additives are being used to have the same effect as tetraethyl lead and there is still a question whether those are harmful, not harmful and we should begin to monitor those etcetera. So engines are still knocking and therefore the fuel does require anti-knocking agents and instead of tetraethyl lead they are using some other things which is something which is right now we will not discuss in this particular course. Okay, so we are left then with criteria pollutants primary and secondary and these criteria pollutants are going to be used as an indicator of the health. So if there are standards for these and these standards are met in a city then you as a collector do not have to worry about the quality of the air in your city. However if they are not met then the whole investigative process begins as to where which sources are contributing most to these pollutants or one of these pollutants and how best to control these. I think today we will focus on PM 10 which is the particulate matter. So one of the things you know students usually do not know how these are measured, how is pollution measured. So I spent quite a bit of time on this particular flow chart it is really straight forward and the question to be answered is how do you measure the mass concentration of particulate matter PM in the atmosphere. So you assume now that there is some polluted space polluted area it could be a room in which agarbatti is being burnt or it could be outside near the traffic signal or it could be near in a kitchen or it could be near an industry it could be in the desert area it could be in some commercial area does not matter there is some space of air which is polluted or we want to know how polluted it is and so we have this arrow here really represents a small tube plastic tube sometimes we can put a funnel at the end of it so that it collects from a larger area but it is a tube which is suspended in that particular so in this room if I wanted to check the quality of air I will just take a tube and hang it somewhere and have that tube then come and connect up with this particular cartridge and all this cartridge is there is a filter paper it could be a glass fiber filter paper cheaply available and the cartridge is an assembly that you can unscrew and put this filter. Now this filter is something that you have weighed already okay and you have to be careful some of these filter papers have an affinity for moisture so if it is a humid environment then they will tend to absorb moisture so you have to make sure that you have put it in a desiccator for 24 hours and then you remove it and you wait and then you put it in this cartridge and after you put it in the cartridge you connect the second part of the outlet of the cartridge to a flow meter so you want to know what is the volume that you are going to be sampling and then you basically have a vacuum pump a small vacuum pump which could be driving this flow so you know you run it let's say at 10 liters per minute for 10 minutes so 10 liters per minute for 10 minutes would mean 100 liters so you have sampled 100 liters of air in this room or at a traffic junction or in a kitchen or you know wherever you want to sample and then after 10 minutes you stop you actually remove this filter paper from here and if the place is polluted you'd probably see some deposit on it okay some gray brown black depending on where you are in a kitchen you'd probably see a lot of gray black in a traffic junction you'll probably see a lot of black in a desert area you'll probably see a little light brown light gray kind of a dust so different places different sources would have different kind of colors or gradations of colors and so you take this sample and again a good idea because there is moisture in the air and you have sampled a large volume through this filter some of the moisture from the air that is passing through the filter would have gotten adsorbed onto the filter paper so you don't want the filter paper to be affected the mass of the particulate matter to be affected by this moisture so you again put it in a desiccator for 24 hours take it out and the difference between the before and after is delta M which is the mass okay that's a total mass collected now this total mass was collected in how much volume the volume was 10 liters per minute Q for time 10 minutes so in 100 liters how much was so that would give you micrograms per meter Q okay that is where you would do it I even encourage students to do this on their own we have found a lot of times when you have set up a lab for them and they just come and do the measurements of your time and flow rate etc it doesn't quite give them and hands on hands on experience so a lot of times actually just give them these as equipment that's available in the lab you know there'd be four or five pumps available that be stopwatches available that these cartridges available just have to be careful with them sometimes that they don't the weighing balance is a little sensitive so usually we would not if they have not don't have training on a weighing balance and I wouldn't let them touch the weighing balance because we use it for a lot of other MTech and PhD research so you don't want to damage it but other than that you know this is like toys for them to play and get get a hands-on experience a lot of times I even encourage them to damage equipment so that they can actually learn how to damage it so next time they won't actually damage it okay so that's what we do this is now like you know some kind of building blocks like Lego or something that they can use I'll stop at this for a moment let you talk to each other take a minute to just you know sort it out if you have some questions you can talk to each other and get it sorted out so I'll stop for a minute let you discuss what's on the display over there and then I will come back so here's a minute for you to discuss please go ahead and discuss if you were to tell your students how to measure particulate matter in a polluted environment how you would do it please go ahead discuss now okay alright that you know what we just did in this previous method is we actually looked at the total mass okay total mass of the particulate matter not really paying too much attention to the size the only limitation of the size is something that can go through this tube for sure it'll be like a big boulder that has to go through this you may not even find it in the air because it'll be so large that it'll probably have dropped by gravity to the ground but small enough particles small enough that are suspended over here that come through and the only limitation is how much can this filter stop can it stop the smallest of particles and how small is small is a question that we don't but assuming that let's say this can capture all that this is fictitious it's an assumption assuming that it can catch all the particles that are there and only allows gas molecules to go through then in some sense this method is only giving you the total particulate matter okay total particulate matter no size just total okay so when we look at that and let's say now I put myself in a situation in which I do this same measurement in a village in a desert area on a stormy day versus in a busy urban junction some kind of a traffic junction on a busy day would they measure the same the chances are that the measurement that is made in the desert village would be much higher than what you would measure in a busy urban traffic junction okay so then which is really bad is the desert dust bad or is it the traffic emissions that are bad that is something which we will not be able to say if we just take a look at the total particulate matter as a measure so we cannot use total particulate matter because the health effect that a dust particle would have from sand in your nose or in your lungs would be very different the suit particle or the emissions particle that is coming from a diesel engine okay so the health effects are different and aesthetics is one thing but we really more concerned always about the health what is the health effect of these pollutants so we therefore need to look at is there another dimension other than just the total mass concentration is there another aspect is there another dimension we need to look at to be able to qualify it based on the health effect okay so that's what we will talk about now so like all human beings are created equal is something we all know I just want to say not can't say the same about all particles so not all particles are created equal and we will try and qualify this assertion oh I don't know what you're seeing on your screen but I think on my screen I'm seeing a small ant here another small ant here another small ant here another small ant here and another small ant here oh many ants over here okay and what is this the color gray looks like that of an elephant I think but because I can't fit it on the screen so probably it is an elephant maybe we are seeing only a part of the elephant so this is like a now a little game I play with the students and I usually do this on the board so I'll just do some work on the writing pad now to share with you this is a large class okay so what I do is I actually make a small dot on the black board and ask people if they're at the back of the room there that they can see it and it's small enough they actually cannot see it so I said that's correct because what I drew on the board is an ant so just for the sake of argument I'm going to make that as a bigger ant okay so you can see this bigger ant here okay you can see this big ant and this big ant if I were to look at a dimension of this big ant what would be the dimension of this big ant so invariably now you know people will start making a guess and it turns out we agree upon that in a small red ant is about two millimeters okay now on the same board what I do is I draw an elephant okay now this is all to scale I'm making it all to scale and you already know that my drawing is very good so now I'm going to draw an elephant so this is the elephant can you see the elephant that is the elephant it's on scale it's to scale sorry I can't make the ant and the elephant on the same scale so this is you'll just have to you know extend your imagination and understand that this is this is an elephant okay now what is the size of an elephant I know you know most of us we've been very productive people and we have not used our time to go with a scale and measure ants and measure elephants but just let's take a guess okay just to make it easier consider a spherical elephant okay a baby spherical elephant okay so I think a baby spherical elephant would be about six feet across is that a good idea six feet is okay everybody agree six feet okay six feet so about six feet which is about two meters okay so which means that we are talking about ten to the power of three okay so the scale is ten to the power of three why is that important why are we doing this we're really doing it because what I want to highlight to the students is that when we are dealing with gaseous pollutants when you're dealing with gaseous pollutants when you're dealing with carbon monoxide when we are dealing with oxides of sulfur when we're dealing with oxides of nitrogen hydrocarbon molecules etc we're dealing with ants we're dealing with ants and when we are looking at particulate matter when you're looking at smoke and dust we're actually dealing with elephants so these are elephants when you see dust you see dust because it has a certain size and it scatters light but around each of this dust particle there will be lots and lots and lots of ants or gas molecules so these are elephants suspended in an ocean of gas gaseous ants so to say okay so the order of magnitude is 3 the order of magnitude is 3 so you cannot deal with particulate matter the physics of the particulate matter the same way as we deal with gaseous gaseous we explain quite well kinetic theory of gaseous we understand very well and students have been doing it it's a part of their DNA to actually you know P1 V1 is equal to P2 V2 they know all of that that's gases as we've known it the ideal gas we've known it since class 8th but particulate matter as elephants now suspended in that gas is something which is not so well understood so that appreciation needs to come in and that's what you know I use as an indicator of what they would be so now I even ask them to imagine themselves to be zoomed to the size of a gas molecule so when they are zoomed to the size of a gas molecule like like in a science fiction movie and they see a particle of dust from sand coming from Tart desert then they actually seeing who this is like a elephant coming or this is like you know a dinosaur coming okay so when when they begin to see that they actually say okay they can actually distinguish why we have to deal with gaseous pollutants distinctly from particulate pollutants okay so that's ants over here and that's an elephant and sometimes even dinosaurs okay so we will talk about that so I hope this is clear that when we're dealing with particles suspended in air as pollutants or as dust or as sand we are really dealing with elephants and sometimes dinosaurs an ocean of ants okay so just to get the scales right an ant is about two millimeters a spherical baby elephant about two meters the order of magnitude is three factor of order of magnitude is three nitrogen molecule is about that much respirable particle is about that much order of magnitude is same okay so it's I spent quite a bit of time on this to emphasize to the students that distinction okay now all the well established physics of ants ideal gas is not applicable to the elephants all the magic of nano is in this new world of elephants all the nano technology nano particles nano this nano that it's all in that domain now the ability to understand this range of sizes has become possible during the development of instrumentation last 30 40 years okay so if you looked at some of the chemical engineering handbooks or mechanical engineering handbooks or civil engineering handbooks by and large they would stop when they any time they're talking about particle analysis they probably stop at two micrometers or so sometimes one micrometer but by and large two micrometers this was still about 20 years ago okay so when I was doing college my handbook I still have a copy of my handbook from that edition it doesn't go the the scale for particulate matter does not go less than two micrometers so it's almost like anything which is smaller than two micrometers used to be dealt with now this is too small to handle and therefore it needs to be handled as a gas okay that's not the case anymore we talking about elephants which are still in suspense that dimension that scale of size is in not really gas molecules not really large particles but somewhere in between so the last three decades has been exciting times for aerosol sands and engineering so when we're dealing with particulate matter in atmosphere or synthesis we're dealing with aerosol sands in engineering and there are many aspects of it so powder production material sciences nano products atmospheric pollutants medical sciences medical sciences you know so we'll talk about that in a little bit but there's been a lot of application of nano particles because we have a better understanding of how to make these particles how to transport these particles within the human body okay so now this is really to give students a sense of the relative sizes of particles okay so let's start at the bottom this is visible to the naked eye and if I were to add something over here I'll probably add human hair so human hair is about hundred micrometers so the way you see it is that if you take ten hair and put them all one next to each other on a centimeter scale then they will cover one millimeter so ten hundred micrometer hair would fit on a one millimeter in a millimeter gradation on a scale I usually you know do this in the class and of course then I have to caution the students not to pull each other's hair to do that experiment but that's a way of being able to communicate to them that's the size so hair is visible hundred micrometers is visible people by and large have also used optical microscope and in an optical microscope they have looked at blood cells they have looked at other cells bacteria for example so bacteria blood cells they are in the size range of 1 to 10 micrometers and optical microscope has a limit of about half a micrometer because if you using the optical waveband the wavelength that you're using is of the order of half a micrometer so anything smaller than half a micrometer then you cannot resolve with that wavelength so the limit of the optical microscope is about half a micrometer half a micrometer is still an elephant for us okay talking about elephants half a micrometer is still an elephant for us so we actually then have to if you want to understand these particles which are elephant like in atmosphere then we need to go to electron microscopy or now there are some other methods in one of the lectures I will devote on how to measure these so electron microscopy is also available this is the range where we will normally be operating for when looking at the elephants there let's look at look at some of the other other sizes also this is bacteria here this is dust fumes okay fumes this is fumes coming from smoke coming from welding for example welding arc welding operations etc this is smoke coming from oil it could be different kinds of oil that are being burnt kerosene oil other oil that is being burnt viruses are here viruses cannot be seen by an optical microscope they're too small to be seen by an optical microscope and oh gas molecules are here answer here and elephants are here okay answer here and elephants are here but the three orders of magnitude the same three orders of magnitude applies over here okay anything else that's interesting tobacco smoke tobacco smoke tobacco smoke okay now we'll talk about I'm so excited about tobacco smoke I'll tell you why okay but before I go into that excitement I will actually tell you why we are interested in these sizes from the perspective of breathability what is respirable what is not respirable so I put a sign by the way this red line over here I think I'm not too sure but I think it represents the wavelength of light so in some sense it is the limit of the optical microscope I drew this red line over here by the way that's the URL for this website what is respirable so the nose is the human nose is designed a particular way and including the hair inside the nose okay it's designed a particular way and it actually does a very good job of removing particles larger than a certain size okay so for a normal adult human nose 10 micrometers is the size which gets stopped in the nose okay 10 micrometers the size 10 micrometers so anything which is larger than 10 micrometers you can expect that it will get stopped in the nostrils anything smaller than 10 micrometers is considered respirable okay so when we say PM 10 particulate matter 10 10 is an indicator of the size so 10 micrometers 10 really represents 10 micrometers so anything smaller than 10 micrometers is respirable now at this point in time again I do some very disgusting things in the classroom so I'm going to go ahead and share with you what I do in my classroom okay ready okay so what I do is I tell students to do an experiment okay they're not supposed to do this in the class when they go home in the privacy of the room they're supposed to do this so you take this finger and not that you don't do it already okay you do it all the time it's just that you just make sure nobody's watching okay so I'm here on public display now so what you know you do is you take this finger and you put it in your nose and you turn it over there and something comes out some disgusting looking thing comes out right okay now that disgusting looking thing if you're in a clean environment happy it would probably look like a light green color like that of cement color okay oh most of you have not seen it because you actually do it in the dark or something like that and you know you kind of look nobody seeing and then you know sometimes you it's disgusting where you actually go and wipe your finger after that okay but usually keep a handkerchief okay when you're doing this experiment it's a part of the material setup that you require the handkerchief and a finger okay that's what you need so you know you look at that you should really see it okay you should see it observe it maybe even get a lens and see you know what's going on over there and that's a part of the system by the way doctors would do it okay any lab pathology lab would do this that's a part of the work that they do it's not disgusting for them it's actually their bread and butter they actually do a lot of scientific analysis through that okay so you take a look at that and you say okay this is what it looks like and then on another day if you've gone out to the city sometime you've gone in a dusty area you've gone in a polluted area etc etc you come back and you do another experiment this time of course with the clean finger again you do that and you observe and sometimes you do selfies you know most of us so love doing selfies these days so instead of doing a selfie of your face do a selfie of your finger okay and look to see if this color was any darker than the light green cement color that you had actually seen earlier okay why I'm why I'm doing this and this is something which students go hmm huh and you know they're they're very embarrassed by this adult over here but it's important for us to be able to kind of appreciate the function that the nose does okay and we not so much for this class but for one of the m-tech classes I do the same work but we actually get into the details of calculating is really 10 micrometer the size that'll get stuck in nose by virtue of the fluid dynamics okay if a particle is moving at a certain breathing rate okay you're breathing at a certain rate and air is going in and the particles are suspended these elephants are suspended in that in this ocean of ants called gas molecules they're coming into your nose and they actually are now experiencing an obstacle called the hair in the nose okay that hair in the nose that elephant will be coming and the ants will be coming so will that elephant bypass that particular hair or will it actually go and impact it okay so they actually go and do a calculation for that and figure out whether the 10 micrometer is actually the correct number or not but that's way beyond the scope of this particular class but you know we I even give them an assignment in which say you know what would be the respirable particle size for an elephant now elephant has a long trunk right so you know there's a certain rate at which the elephant breeds so I don't know what is respirable for me is the same which is respirable for an elephant never mind that a baby's breathing rate and the baby's nostril size whether the respirable is PM 10 or not okay that's something that we have to deal with even if we don't have to deal with the elephant trunks okay enough said I think about this are you all convinced that knows does a good job yes yes okay very good all right so this is stopped in the nose okay anything which is greater than 10 micrometers this is 10 micrometers get stopped in the nose so why I was excited about tobacco smoke is that when you smoke I'm not promoting it I'm not saying you should but when people smoke and they shouldn't not good for health but when they smoke the smoke actually is respirable if it is not respirable they'd be wasting money on the cigarettes okay so it's respirable now the physics of tobacco smoke when we go back to some of our traditional medicine systems there are still places where of course there's abuse of drugs but then there are places where they would actually have like a hookah or a chillum in which they put a little bit of medication and that medication actually gets inhaled and gets to the lungs and actually has people be well and I'm pointing to it also from the perspective of that there's abuse to it so drug abuse but the point the physics is not right so let's just extend a little more I'm sure you have you have people or some of you actually deal with this that you carry a little can for people who have asthmatic issues they carry a little spray can which from time to time you're actually going to okay you take that you put that in your mouth and you do that spray now whether that droplet will actually get to your lungs or not the physics of the respirability is still the same what size of that particular droplet should be there such that it actually gets to your lung because once it gets to your lungs once it gets to the alveolus that's where it is effective if it gets stuck somewhere in the throat and a lot of times 70 80% of it gets stuck in the throat only 20% has some chance of being able to go through you suddenly therefore have an interest in what is the size distribution of the spray that comes out from that aerosol can well what I'm pointing to is that the physics okay physics the understanding of physics when we said medical delivery you know medical applications the same physics is applicable over there okay I say another thing which is not in this particular slide I also talk about materials okay for example paint pigment paint pigment there is a particular brand which is got two kinds of paints one is white deluxe white they call it and one is super deluxe white the super deluxe white is 10 times more expensive than the deluxe white how come both are white no but there's a difference the difference is that the deluxe white is just white pigment where is deluxe super deluxe white has pigment which has a very narrow size range and that narrow size range is selected in such a way that it scatters maximum amount of light so if you use just one 20th of that paint it will scatter as much light as one unit of the deluxe white paint okay so the amount of paint that you need is 20 times lesser okay so the whole aspect of what application can you use the size and their function and the interaction with light interaction with the body interaction with blood cells interaction with you know magnetic fields interaction with your nose all of those the entire range is available in this domain of elephants suspended in ants okay also here's the website here's the URL for that please go ahead and see it okay now relative sizes I think we've talked about this already again one more time paint pigments this is where if your paint pigment was within size it will scatter maximum amount of light viruses are in this size range respirable for sure tobacco smoke we just discussed is also when I also said delivery delivery meaning from the perspective of medication okay here's another I should put the URL for that but this is again one of those free to use images this is a very complicated figure okay so I'll spend a little bit of time on it I spent a lot of time on this with my students so I would appreciate you you know getting behind this and understanding it in a way that actually then students would be able to appreciate it from you so the x-axis is the diameter of the particles okay this is 10 micrometers so everything here is respirable everything on this graph is respirable this over here is some kind of a concentration and as is some kind of a concentration because there are two types of graphs over here one is the mass and the other is number okay so this axis is representing both mass and number but it's normalized so when you go ahead and look at the particles in the atmosphere there are three distinct modes normally when we deal with Gaussian distributions we deal with unimodal single mode one mode okay but what's been observed across the world is that the atmospheric the ambient aerosols ambient particulate matter have three modes the first one is called the coarse mode these are particles which are large particles which are huge elephants dinosaurs okay and they stay in the atmosphere for some time but why enlarge they'll settle out because they're large enough gravitational settling would be effective and they tend to settle out they usually benign they come from crustal material geological material they're not coming from any reactions they're not coming from any chemicals these are just geological dust material so even if you were to breathe it it is inert so it will not have much of a health effect much of it will get stuck either a little past the nose or you know upper part of the trachea then there is this other mode on this side which is called the nuclei mode or the nucleation mode okay nucleation mode is something which is coming from I don't know how to say this but this is where the particles are born that's probably the best way I can say it these particles have existed for centuries okay for thousands of years they just happen to be on the ground happen to get reentrain with the movement with either wind or traffic etc etc so these are dust materials inert material they've been around for thousands of years whereas these particles over here the nuclei mode are particles that are just born okay let me explain when I say they're just born so when we were kids you know we used to I used to live in Deradun I grew up in Deradun and winter time it really used to get cold so I don't know you know for some of you who live in colder cities during December sometime January sometime we used to pretend like we were smoking okay so we would put a take a fake cigarette fictitious cigarette like that and do this and actually smoke would come out of a mouth okay so what is the smoke really it's not very different probably from the smoke that comes out from a chimney the white smoke that you see coming out from a chimney a similar smoke okay and that is what that's basically water droplets so inside the mouth at 37 degree Celsius the air is 100% humid you know just very if not 100% maximum you know it's like 95% human you should sometime do that actually so one experiment was to test what's going on in your nose you and I have always put a thermometer in a mouth to see what the temperature of the body is maybe you should also get a humidity meter relative humidity probe and see what is the humidity in your mouth just check it out probably close to 100% so when this fully humid 100% humid comes out of the mouth it suddenly experiences a cold environment and in some sense the vapor molecules get together and form droplets okay so till it was in the mouth if I opened the mouth and I showed it to somebody you would not see the smoke all you would see is my tongue and my teeth and you know part of my throat but you would not see the smoke but when I do like that smoke comes out so actually smoke didn't come out what came out was the water vapor which under these cold conditions nucleated nucleated okay not condensed nucleated distinct from condensation so if I were to take two bottles of water and one had normal room temperature water and the other one had cold water okay even from far you'd be able to tell me that this one has cold water why because there would be some condensation outside it okay that is condensation as we know it okay a nucleation is not the same as condensation it is distinct from it because it does not require a surface it's called homogeneous nucleation so the physics is something that is a little complicated so we won't get into the details of that but you should just know that that is the birth of a particle for the first time many ants of a particular kind many ants which are water molecules got together at some point in time and formed is the start or start of a baby elephant okay so that's the birth of a particle that's the birth of a droplet okay so that's what nucleation is that's one way of particles being formed another way of particles being formed is from chemical reactions so for example if you are burning a candle if you're burning a candle you can actually see that at the top of the flame there's these carbon particles that are emerge emerging okay if you take a candle with the flame over here and you put this paper white paper just above it not close enough otherwise it'll burn the paper just far enough you'll actually get deposit of these carbon particles where did these particles come from they came from some chemical reactions that took place within the flame the wax melted it went through that wick and after that wick it burnt in that flame and after the flame whatever was unburnt actually came out or some reactions that took place that gave rise to that suit you can see it in an agarbatti you take an agarbatti and you light it as long as the yellow flame is there you will see some black smoke coming out of it okay that is birth of particles that is formation of particles if you then take the agarbatti and you remove the yellow flame you extinguish as you look and it goes off and then instead of black smoke in a flame you start seeing white smoke or gray smoke coming out of it now that gray smoke in terms of the chemistry is very different from the black smoke which is coming out from a candle or which is coming out from an agarbatti and which is very different from the chemistry of the smoke that came out of my mouth when I was a child and I was trying to pretend that I was smoking okay so the whole aspect of what size of the particle what chemistry of the particle is something which is going to be of interest to us because that chemistry and that size is going to decide how detrimental it's going to be for my health okay so this is the nucleation mode then very small size sometimes so small that it actually behaves like a gas almost so if I take this room put a little bit of perfume over there somebody at the other end of the room will be able to smell it very quickly our nice smell okay same thing with an agarbatti if I light an agarbatti in that corner and I have somebody say and they'll say yeah I can smell it so it's almost like these particles are small enough that they behave in terms of the transport they behave almost like ants or they behave like gas molecules so a lot of times in the atmosphere they will disappear very quickly they will not accumulate in one particular place but some of these particles also tend to coagulate and I'll go into the next details of it in the next slide or so these particles collide with each other and become bigger and some of these particles are particles now and they provide a surface on which now instead of nucleation condensation can take place so these particles are now getting bigger now these particles when they get bigger they stop behaving like gases they cannot dissipate so quickly like gases so they begin to now accumulate in the atmosphere so this mode over here the third mode is referred to as the accumulation mode it is the mode which will be in the atmosphere for the longest time okay so this slide shows you that particle diameter this is the particle diameter and this is the collection or removal efficiency from the atmosphere particles which are larger than one micrometer they are large enough that gravity would act on them and the sedimentation rates are high enough that they will be taken away by gravitation okay these particles over here on this side which are much smaller the smaller they are the more they act like a gaseous molecule and they tend to diffuse out so these are particles which are large enough that gravity will do the work these are particles which would be small enough that it'll act like gases and diffuse out somewhere in between these two sizes there is a particular size which is neither small enough to diffuse out like a gas nor large enough to sediment out like a large particle okay somewhere near one micrometer is the size which will stay in the atmosphere for the longest time so if you really take this over here and you flip it flip it horizontally you flip it horizontally you actually see this particular mode okay so this mode over here this mode over here is somewhere near one micrometer these particles are small enough that they will diffuse out these particles over here anything larger over here is large enough that they will sediment out but somewhere in this range are particles that are neither small enough to diffuse out nor large enough to sediment out so they tend to accumulate in the atmosphere and that is these are particles which you and I tend to get exposed to maximum because they are in the air for the longest time these will disappear these will disappear but these will remain for the longest time okay so that is a very critical aspect of size and the three modes that students need to get because that's at the heart of most of the research that we've been doing in the area of air quality okay now I'll switch my attention to the pink plot okay so this was the dashed blue plot that we talked about I'm now going to talk about the pink plot pink plot is not mass it is the number of particles okay it is the number of particles so if I were to take a 10 micrometer particle and there's a certain mass that this 10 micrometer particle would have and I take a small one micrometer particle and this has certain mass if I were to make these equal I'd have to take some number of particles to be able to balance the two masses okay so that number over here is 1000 because the dimension is 10 times the size is 10 times in terms of the volume it is dp cube so 10 multiplied by 10 multiplied by 10 which is a thousand so the point is that a one 10 micrometer particle is equal in mass to thousand one micrometer particles okay so 10 micrometer particles is thousand times as heavy as a one micrometer particle so the wider dimension the linear dimension increases by one order the mass dimension increases by three orders of magnitude okay so the smaller particles therefore don't contribute much to the mass there may be very high in number but they don't contribute much to the mass so this pink line over here is the number so while the number concentration is extremely high the number of particles that in my fake smoking or from a candle or from a agarbatti the number of particles is very high but the contribution to the mass is very small because they because of this dp cube relationship okay over here the particle number is small but the mass is quite high because of the thousand factor okay and over here in fact the pink disappears almost all completely there may be very few particles which contribute so you know if you were to do this is where the debate is right now the debate is should we have mass based measurements for standards or should we have number based measurements because if you remove a one hundred micrometer particle one hundred micrometer particle it is equivalent of removing in mass one million one micrometer particle so you know it's like oh so what I'm saying is that I can get rid of one large particle and that will compensate for a million small particles you can't compare the two because the size that we are dealing with the breathable size that we're dealing with the numbers are very high there's another aspect it's not just the number is high the surface area of course will also be high but the source of these particles okay they're coming from some chemical reaction they're coming from some human activity they're coming from some combustion source they're coming from some combustion which is incomplete so all the reactions that would take place in a combustion domain all of those the incomplete combustion lead to these many byproducts which are not necessarily complete in their reactions so they are not stable they will tend to get into your lungs and then just go ahead and start actively start participating in the reactions so we got two things to deal with one the size is such that it is respirable the size is such that it is large in numbers in surface area and the size is such that the chemistry of it is coming from chemical reaction so we are in a situation with this particular window over here is the most dangerous and the least understood in a lot of ways also okay so that's what this particular pink plot is about okay now these are several pathways that particles from one mode can move to the next mode so I mentioned to you about coagulation and condensation so this is just a description of that this over here was what's happening in the atmosphere the particles are already there vapor is already there ants are there elephants are there ants will go and sit on elephants so that's condensation elephant elephant will combine with each other and a big bigger elephants okay so all that is going on it's a you know it's a dynamic process in fact the entire process we deal with this aerosol dynamics lot of the atmospheric chemistry lot of particle formation in the atmosphere that happens which leads to secondary aerosols so all that is there beyond the scope of this particular course but that's happening and you know that's being researched upon and that's well documented then this one is slightly different it is different it is saying what happens during combustion and this particular case they're saying let's say if you were to burn coal so when you begin to heat up the coal a lot of the volatiles from the coal will actually volatilize they'll evaporate okay and then some of the char will burn and some of the metals heavy metals that are available in the char at that temperature will volatilize so now what you have in the vapor phase may be some hydrocarbons some metal vapor and some other compounds and then the coal will burn out and some of the mineral material fly ash for example what is referred to typically the ash will come out as bottoms which are large particles but these small particles small vapor the vapor and the gash etc etc they tend to react or they tend to nucleate out into smaller particles which are very difficult to control even in the best available control options and these tend to then get emitted from the chimney okay so if you look at the chemistry of particles which are coming from here and particles which are coming from in the chimney these particles will be rich in SiO2 okay basically ash whereas these particles the smaller particles are preferentially enriched in heavy metals so what is being emitted is actually something which is enriched in heavy metals which is not good for health okay so then again the whole issue comes up are you going to do mass-based measurements are you going to do number-based measurements that issue comes up so this is something which is hot research which has been going on for the longest time mercury is an issue over here a lot of times people want to mercury again it's liquid at room temperature it volatilizes and you know so it's very trace quantities sometimes even not even measured by you know we recently did some XRF we couldn't catch mercury so for mercury you have to go for another method which can go to be parts per billion level rather than parts for million level etc so those are some of the concerns from a chemistry perspective okay now we said not all particles are created equal we said you know that these particles have different chemistry they get formed differently they have different sources but we have another aspect to look at which is how many of these particles will actually go through the nose but once they go through the nose what happens to them where will they deposit in the lungs or in the alveolus so this again is a little complicated graph and I think if you're not seeing it clearly it's because the image itself is not clear over here but you know you should really focus on this particular solid blue plot which is the deposition okay and this is the deposition inside the lungs and these are our three modes that we had talked about first mode this is the coarse mode this is the accumulation mode and this is the nucleation mode the nuclei mode and if you notice that the maximum deposition is happening in this particular size range so this is how you may want to look at it that when we breathe anything which is greater than 10 micrometers will get stuck in the nose but anything less than 10 micrometers will get inhaled all the way into the alveoli which is the last part of the balloon in the lungs I remember from my class 11-12 biology that we had to draw you know the lung the detail of the lung and there was this little balloon or a collection of balloons and around the balloons there would be a capillary or many capillaries and the different thing about this particular capillary was that it was the arteries were bringing in blue blood which was deoxygenated blood and the veins were carrying blood which was enriched in oxygen which was red in color this is opposite to all the other parts of the body where you the arteries are bringing in oxygenated blood and taking away the deoxygenated blood okay so that detail of that alveolis is kind of etched in my memory and that alveolis is where you know the air tends to stay for a certain fraction of a second before it is exhaled out so there's a lot of physics that goes into the understanding lot of modeling that goes into the understanding of what are these particles what is the size and where in which parts of the lungs they might deposit so the you breathe in and then you breathe out so for example if you see somebody smoking they breathe in the smoke and then they exhale you know much of the smoke comes out okay so similarly when we breathe in particular in the pollutants in the air you breathe in you can't see them because the concentrations are fairly low but you breathe them in and then most of them you breathe out but there's a certain fraction over there certain fraction over there that has a good 70 to 80 percent chance that it will deposit in your lungs and that is in this particular size range okay see this over here it's about 70 percent 70 percent of these particles have a good chance that they will deposit out okay so that's the size dependence of where the particles will deposit within the lung or different parts of the lungs similarly this is now they break it up they break it up in terms of the beginning of the you know in the head then they talk about the bronchioles then the alveoli different parts and this is the total okay this is the total and somewhere here is the highest deposition okay and different physics models would give you different results but predominantly everybody's agreeing that somewhere in this size range somewhere in this range size range the deposition in the alveoli is highest okay so again the URL is given and you're more than welcome to look at it okay now I'm going to share some slides from the PhD work of one of my students his name is Dr. Nitin Goyal he completed some seven eight years ago these are still relevant so I'm going to share some of these slides he went and did some measurements of size distributions in two places in Mumbai okay these are the two places in Mumbai one was in the Worley area which is near in in Mumbai you can't be too far away from the ocean at any point in time but this is about maybe about a kilometer away from the ocean this would be about maybe another five six kilometers away from the ocean okay so these are two places where we did measurements these are the size distributions these are done at different times of the day this gray one over here the last one over here is the 24 hour average this is PM 10 by the way the blue line is PM 10 so everything on the left hand side the way this is plotted is that if you were to take area under this curve okay so if you take this line over here and you take area under any of these curves it'll give you the total mass concentration total mass concentration of particulate less than 10 micrometers so different times of the day the size distributions change which is likely because there are different sources that daytime you'd have all the vehicle movement nighttime we don't have any vehicle movement so you expecting that the size distributions would be different because the sources are different at different times of the day I've also put over here a red line which is PM 2.5 okay as PM 10 is 10 means less than 10 micrometers PM 2.5 means less than 2.5 micrometers okay that's pretty straightforward and we started with PM 10 but then realized that a large part of the mass contribution to PM 10 may be coming from the course mode so you know large part of the mass contribution may be coming from the course mode but the particles that are generated by human activity are not necessarily in the course mode that they are in a mode which probably falls under 2.5 micrometers so we now have made yet another classification PM 10 is fine but then there is a subset of PM 10 which is more associated with anthropogenic activity or human activity so if you want to really be able to measure human activity you want to be able to take PM 10 as well as PM 2.5 to see how much contribution is coming from course mode and how much is coming from human activity okay so PM 2.5 got introduced at some point in time and we've been very commonly now using the ratio of PM 2.5 to PM 10 okay PM 2.5 to PM 10 the ratio it's an indicator of anthropogenic to combustion activities or human activities so the smaller the ratio that means human activity is contributing less larger the ratio that means more and more of particulate matter in the atmosphere is coming from human activity okay ratio is large most of the particles will reach lungs and they are possibly more toxic so PM 2.5 to PM 10 ratio being large is not a good idea so you're qualifying PM 10 even further you're not just saying PM 10 as a total mass concentration of particles smaller than 10 micrometers you're also saying within that mass concentration how much of it is coming from human activity how much of it is likely to be toxic okay now these are some measurements that we had made in Pune and Mumbai and this is PM 10 over here on the x-axis on the y-axis is PM 2.5 okay and this is the slope so slope is actually the ratio okay the slope gives the ratio and the ratio is 0.58 0.51 which is typical in India this is for Mumbai this is for Pune not very different we thought Pune being an inland city it may be very different it's not very different again ranges around 0.5 or so okay then we put all of these together this is Mumbai Pune everything together this over here is measurements made during Diwali we expected that during Diwali time that because a lot of firecrackers are being burned a lot of combustion is happening so the chances of smaller particles would be higher but you know it somehow seems to fall on the same line as the rest of the graphs that's probably because there's a lot of traffic movement to a lot of dust is also in the air but if we did just take this particular set and do the PM 10 to PM 2.5 ratio the PM 2.5 to PM 10 ratio is actually greater than the rest of the average now just one last thing I'll show you this little box over here this box this box is showing that this box is basically the CPCB standards for compliance so as long as you are inside this box for PM 10 and PM 2.5 you're in compliance so the bad news is that most of the time in Pune in Mumbai we are outside the box now I know out of the box is considered to be good and all that stuff in you know creative thinking but here when we're taking out of the box it's not a good thing it's saying most of the time we're not in compliance okay all right so again this is just to reinforce that PM 2.5 to PM 10 if the ratio is less then it's a good thing if the ratio is high then the pollutants are toxic okay I'll stop here thank you very much bye bye