 So, this is where actually lysiometric studies become very useful or the pore solution sampling becomes very useful. A bit more about the lysiometric studies, they will simulate the effect of percolating rainfall on the release of contaminants from the waste forms. Waste forms are nothing but different types of waste which are either stored on the ground or dumped in the soil mass. These studies will provide insight in understanding the site as well as validating water balance studies and radionuclide magnation in the unsaturated zones. This is where our profession matches very well with hydrogeologists, they also do the same thing, but then their perception is mostly on ground water flow, our perception is mostly on the what is happening to the soil mass alright. So, these are two different perceptions for the same problem, for us porous media becomes more important, for them flowing water becomes more important. So, data obtained from this study provide a link between the laboratory and fuel conditions and thus aid in predicting radionuclide migration from shallow land disposal facilities. I have used the word radionuclide migration, it could be any hazardous toxic waste for that matter. So, lysimeters are nothing but pore solution collection devices, zero tension lysimeters they collect pore solutions from saturated soils. So, there is no suction pressure in the soil mass. This is a typical conceptual figure which shows what is meant by a lysimeter. Now, this is a control volume which has been created in the Nc2 conditions. Now, this is a soil which is back filled and then you insert something sort of a pervious material like gypsum block, yes this come contaminant length testing means yeah. So, again this is the same thing you can you can check the concentration at the source itself and downstream is this the what you are asking in which in this one ok, I think yeah I will try to answer your point here. So, first thing is you install a control volume in the ground and then you insert something which is pervious, it could be a sand layer, it could be gravel mixed with sand, it could be a perforated pipe, it could be a gypsum block or whatever and then you refill the native soil clear, but what has happened in the process of refilling we have destroyed the matrix of the soil. So, that is one of the limitations of these studies. Second thing is there could be preferential flow from the sides of the control volume the same thing as it happens in your falling head test, there is a preferential flow between the sample and the container. Now, coming back to your point either I can dump the waste over here or I can bury the waste over in the soil mass ok and then you start saturating it that means percolating water. So, if the waste is lying on this system the moment it come in contact with water the leachate will be moving into the soil mass and they will be collected from this pervious fill to a collection bottle, is this correct? Even if you bury it inside what is going to happen this percolating water will subsequently percolate into the soil mass first then it will interact with the waste whatever leachates leachates out leachates are they will be collected into pervious fill and this fill can be used to suck out the sample, is this part clear to your question this is what you are asking. Then you should understand one thing we are civil engineers we always talk in terms of factor of safety of 2 and 3 what is the meaning of this? We always want to get an answer within 30 percent limits clear. So, these are very indicative test and again the bottom line is something is better than nothing, but yes you can get an answer to a real life problem within a bracket of uncertainty. So, the biggest question is even if you get some answer within some uncertainty limits there is no harm and you can define it further. So, subsequently you will see that there are methodologies which have been developed which will cater to your needs very well and you need not to disturb the soil mass. So, it is very good that you have raised this issue all these lysimeters you know they have been in practice since 1940s, but over the years what has happened is because of good electronics because of more sophisticated instrumentation the practices has improved a lot. And now we are in a situation or in a stage where the best possible sampling can be done I will take you through these three line you know you may realize that this is the development which is happening. So, conceptually is this part clear that how a lysimeter will work. So, basically you have a soil mass in which some previous system is embedded and then this system can be used to suck whatever leachers are coming out of the waste matrix in the best possible manner. Now, this is another good example of a field lysimeter which was developed incidentally you design your landfill liners like this have you ever seen a landfill liner cross section some of you must be working on landfill liners design is it not when you are working yes. So, your emotions can tell me that you are associated with these studies and this reminds you that you have to start to study your topic. So, anyway look at this you have the gravel at the bottom most point followed by again a thick gravel followed by again a gravel layer followed by a sand layer followed by percolating water and then this is where you can dump the waste material. So, essentially what is this doing is a reverse filter. So, everything which filters out of this gets collected over here you can provide two suction chambers at the bottom and you can put a motor over here or a pump over here. So, that you can pump the leachers on to the ground depending upon the depth of the lysimeter. So, there are few lysimeters which are instrumented so well that you have pumps submersible pumps also at the bottom of the lysimeters so that you can pump out the leachers quite easily. So, this is another design of a lysimeter this is ok, but again you cannot stop potential flow taking place from this lysimeter. Another thing is if you want to study how many collides what fraction of collides is passing out of the mines this is a good technique. So, influence of mobile collides on contaminant mobility sometimes extra organic materials in the soil can reduce the collide migration because of the cohesion between the particles. So, fines may not move out. These type of studies will be very good for identifying the materials which should be the best candidate materials for designing a lysimeter system so that under hydraulic overhead the fines should not get washed out from the soil mass. I have been talking about this situation earlier where because of contamination the fines from the soil may get washed out because of eating up of cementing materials. Now, this is also a typical design of a lysimeter where you have a sand cushion below the soil sample though it is written that this is undisturbed soil core what normally you have to do is you have to go to the field cut out a thick slab of the soil and then place it on the sand bed and below the sand bed there is a cavity and what this cavity does everything percolates into this there is a sloping bottom and then the whole idea of providing the sloping bottom is so that you can collect the leeches easily from this end and then you have a air inlet and a pore solution extraction alright. You can design your own lysimeter for that matter depending upon your requirement the basic idea is it should be able to collect the pore solution continuously this is a very interesting liner system particularly when you use them below the clay liners. You have a clay liner and there is a glenual backfill in which a pipe perforated pipe is buried what the perforated pipe does this pipe will simply collect whatever leaching out you attach the system to a pump and you can drain out all the leeches from the land cells. So, this is nothing but a integral part of landfill leecher collection system alright. So, as I said this is basically used for detection of leakage underneath the clay liners. You can devise an electronic circuitry and put that electronic system somewhere here. So, the moment heavy concentration of leeches comes and touches this immediately the circuitry will go completed and this becomes a automatic leecher collection indicator or alarm. So, this type of instrumentation can be done the biggest question is how would you do that? So, these systems are developed for testing your design philosophy. So, the whole clay liner philosophy can be tested it is a sort of a performance test. So, you load it with water and then see what type of contaminants are going to percolate through this ok. These systems can also be used for determining in-situ hydraulic conductivity of the liners to demonstrate proper functioning of the clay liner whether the clay liners are intact or not whether the fractures have taken place whether the concentration of ions is passing through it or not. So, all in short the basic philosophy is like this that you have a upper layer which is the fill material here you can put lot of sensors moisture sensor temperature sensors humidity sensors ok PS sensors salinity sensors and so on. And then there will be a lower compartment which is going to collect leeches. So, this is the basic design philosophy how good a design would be depends upon how best possible way you can do it. So, basically these type of philosophies are used for performance assessment of solidified radioactive waste units or toxic waste units and to study the attenuation properties of the soils. I think Vinil you are asking this that I have embedded now here a waste body ok. Now, the rain it starts interacting with the rain. So, what happens the leeches will come out alright. So, you can collect now leeches because of the influence of the rain water or the ground water even suppose there could be a ground water. So, because of the fluctuation of the water ground water the leaching may start and whatever leeches you are collecting you can find out their concentration to again validate the theoretical models and you can make a mathematical model for leaching material data. So, this is the basic idea about these type of studies is this clear no any doubts yes please. Yeah. Actually I am unable to follow what is the meaning of giving waste just let him let him complete. See whenever somebody asks a question you let him complete let him discuss ok. It is not a very good way to you know dissect somebody and start talking yes please external substance means some waste yes yeah I mean like your question is basically what I could follow is either this unit will be sitting over here or this unit could be inside the soil mass and slowly and slowly it is going to interact with the water is this your question now you explain what is that you have followed. We are not giving any contaminant we are not giving any contaminant the idea is your waste is either sitting inside the soil mass here like this or this unit could be piled up over here. Now slowly and slowly this unit will interact with the rain water or the ground water and then what happens this unit will leach out something and that leachate is going to percolate into the soil mass. So, how you are going to capture it how you are going to tap it. So, this is where you are going to collect the leachate and once you have collected here you can take it out from here by pump or by suction or whatever you can analyze it and you can find out how much is leaching out of this arrangement is this part clear now ok. Let us talk a bit about tension lysimeters so by now you know that these are the lysimeters which are used for collecting pore solutions from unsaturated soils. This is a simple suction lysimeter or a tension lysimeter which you may call as there is a PVC tube and there is a porous disc at the bottom of this PVC tube insert this in the ground and then apply some vacuum. So, because of this application of vacuum what will happen the leachate will rush towards the porous disc and then it gets filled up into the PVC pipe. You can lift it up with the with the help of a pump collect it in a sample bottle and do the analysis this I had shown you when you had visited my lab some of the slides I will show you today again to reiterate it this is ok. So, this is one advancement you may say since 1940 1930s all right. So, here the disturbance to the soil masses minimal not minimal minimal very less this another type of a system which was designed quite in back in street 1940s I suppose very preliminary design the same thing here only difference is they used to keep a bottle in a ditch and then there used to be a perforated plate below the soil mass, but again you are disturbing the entire soil. So, conceptually this is from where people started working on you know tension lysimeters, but then the state of the art has improved a lot and you need not to do this type of studies. So, whatever soil sample is leaching can be collected in a porous plate which goes into the bottle and ultimately you can lift from the bottle with the help of a vacuum pump. Soil salinity sensors these are used for in situ measurements of soil salinity, but this is a very blind term I hope you will appreciate salinity is a very blind term because you cannot be specific of the species of ions which are present we agree Benin you got this point. So, you can always say yes there is some thing leaching out of the facility, but you cannot be sure what is the species of the contaminant which is leaching out. So, there you have to go for pore sampling and then check the species of the cations with the help of ICP, MS, ICP or atomic absorption. Absorption techniques some sort of a spawn material can be used as an absorbent for sampling the pore solution is a very primitive way and it requires large surface area of this point which will improve the efficiency, but then the biggest problem is not a fully harness method it is not a very well developed method of course, some people tried in the earlier days. Now, let me move on to the pore solution extraction by centrifugation this is a laboratory technique centrifuge the sample and with the help of the centrifugal force you can display some amount of pore fluid if that is not sufficient enough then what you should do. Soil is mixed with CCl4 what is CCl4 carbon tetrachloride or chloroform and then you centrifuge it in a tube sorry this is the carbon tetrachloride somebody said chloroform I said yes CCl, so carbon tetrachloride. So, when you mix it with the CCl4 and then centrifuge it then what happens CCl4 will displace the pore fluid. So, CCl4 goes into the soil mass and the pore solution comes out you can collect it and you can analyze and you can find out what is the concentration of decontamination. The best technique for even doing with the dry soils because the pores get filled out with the carbon tetrachloride and whatever pore solution comes out this can be the concentration of the pores. However, the biggest limitation of this technique is that the type of solution which is coming out will depend upon the soil type alright. So, it is very difficult to centrifuge clays it is very difficult to remove pore solution from the clays by this method. However, if you have sandy salty type of soils it is very easy and that is the reason that the results which you obtain from centrifuge cannot be generalized because there is an effect of the external forces which are acting. Now, this is where I will try to give you some more idea about the lysiometric studies till now I think you must be clear about what is meant by lysimeter, a device which creates a control volume of the soil for studying various contaminant transport mechanisms under Nc2 conditions. Now, when you do field studies unfortunately you do not have any control on the boundary conditions and they are very expensive both in terms of financially as well as time wise. If you match them with laboratory studies you will notice that laboratory studies cannot simulate feeding conditions, special variability cannot be taken into account and this is where lysiometric studies become very important. So, this is the intermittent approach between the field test and the and the laboratory test and what I mean to say by intermittent approaches that this simulates the Nc2 conditions with better control on boundary conditions. And this technique has been identified as one of the best techniques to study the interaction and migration of contaminants in the NGO environment. I will show you the efforts which were made by my group in installing a lysimeter at one of the sites at waste disposal sites at BARC for the real radioactive waste. So, this is the facility which was installed you have a ring of stainless steel 1.2 meter diameter which was embedded into the ground and then we embedded two tubes for measuring the moisture content volumetric moisture content with the help of TDR probes time domain refractometry probes. You can see S1, S2, S3, S4 as the suction samplers which were embedded at different depths below the ground surface. So, what we are speculating here is that we are trying to find out how contaminant migrates if a layer of dosed soil is placed on a natural soil. So, this is how we are again simulating a lysimeter. The top layer happens to be a contaminant is spiked soil and when you recharge it with water either manually or because of the environmental conditions, these contaminants have a tendency to migrate into the soil mass. So, we are trying to find out concentration as a function of Z depth and time. So, the moment a concentration front reaches over here the sample gets collected in S3, the moment it reaches over here the sample gets collected in S2 and similarly S1 and S4. Now, these TDR basically give you the value of moisture variation along the depth over a prolonged duration. These experiments are done for 3 to 4 years regularly and what we did is that this layer we spiked with cesium, cobalt and tritium which are the radioisotopes and groundwater table can also fluctuate within the control volume outside the control volume and so on. Now, this is how the whole setup looks like that these are the TDR probes 1, 2, 3 and 4 points are the suction samplers and these are the excess tubes which can be used for measuring the moisture content of 1.2 meter, 1.5 meter soil column which is lying below this. This top collar which you are seeing the soil was excavated and this was refilled with spiked material spiked sand. Now, when you are drilling these holes for installing the TDR tubes there will be a cavity form between the native soil and the TDR tube. So, you have to fill it up with the help of a slurry of the soil so that there is no preferential flow again taking place between the suction sampler and the TDR tubes. Now, this is a close view of how suction samplers can be installed and how can you take out a pore solution from the well alright. So, this is the well which is connected to the suction sampler. There is a caution because right now you do not find any contaminant over here, but once it has this spiked with radioactive contaminants it was a health hazard to go to near to this place and collect a sample, but then everybody has a limit of exposition for the radioactivity you know. So, the moment that limit is over the second person has to go for collecting the samples you cannot continue collecting samples like this. So, you learn a lot when you are dealing with these type of problems. This is a typical suction sampler which goes inside the ground this is connected to a collection sampler then you can apply vacuum to collect it in the sample the training is done in this type of a CBR mold. Now, this is how the instrumented instrumented site looks like you can see a lot of wires coming out of the units this is the installation of the TDR probes and the suction samplers and this is how the dosing is been done you can see the statuary notice over here that this is not a place for everybody to come close to the vicinity and then this is how the sampling is dosing is being done of the sand with the radioactive material and then is a strontium which is crimson in color is being spread on the entire soil mass. So, you have to take some safety measures for doing this. These studies were done by my PhD scholar Dr. Ravi Ranjan Rakesh who is a BRC stalwart right now. Just to show you what type of TDR results you will get if you do the analysis over depth versus volumetric moisture content and you can notice from here that every month we used to take the samples and this was the famous deluge of Bombay you know 26 July which occurred in between and we lost the instrumentation we could not continue these experiments we have to replace them. So, incidentally what it gives you is the function of the volumetric moisture content up to 2 meter depth. So, this is where we can simulate you know saturated and saturated flow conditions and those of you are interested you can check it out this work is published in geotechnical and geological engineering 2009 very recent publication. Now, this is a peculiar graph which you can notice I think you were there you were talking about how activities can be or the concentration can be you know monitored. If you look on the y axis this is the treasome activity in bacharyl per milliliter and on the x axis you have time. So, as time increases you will notice there is a spike and after which this spike fades away. So, this is the maximum activity place where the sample was taken it is something like the front of contaminant is moving and the moment it crosses over a certain depth of lysimeter there is no sample available to enter into the lysometric tube and hence you can get only one spike all right. Now, you will appreciate this point that over 500 days how these activity is changing with respect to depth. So, what we established here is that cesium and cobalt sorry there their sorption capacities are very high. So, they get solved within the top layer of the soil they will not reach even after 500 days beyond 20 centimeters. So, is this something good or bad it is good yes that means, even if you dispose of something on the ground even after almost more than a year you will not find any trace of this activity in the bottom surface. So, you need not to be worried about most of the activities which are being taken up by nuclear scientists. So, this was a very good study which tells you how to plan the activities and you need not to spend more money designing barrier system and containment system and so on. The nature takes care of itself you know it is a good example. Yes let us talk about pressure membrane extractor which is a laboratory method. This unit you must have seen in the laboratory where we have a pressure membrane extractor chamber which is connected to a compressor unit air compressor unit and a retainer unit. What happens essentially is that this retainer and compressor unit pushes in compressed air into the chamber and details of the chamber you can see that looks like this type of arrangement where you have pressure gauge connected to read what is the pressure inside and what is the air inlet. Keep several disks on a typical membrane which is known as cellulose state membrane. This experiment you will be shown when you come to our lab for doing experimental geotechnics and then because of this application if these containers are having slurries water will come out and then you can check what is the concentration of the contaminant will be draining of water. So, this is connected to the sampling bottle at the bottom of the pressure membrane extractor unit. Now, these several studies we have utilized for two purpose. We have differentiated first of all whether a soil is contaminated or not simply by doing the pore analysis, pore selection analysis with the help of AIS or ICT and then second is you can find out the metric suction of the soil also because in literal terms what you are doing? You are doing a sort of a triaxial cell in which the cell is filled up with air and then you are trying to squeeze the water out of the soil sample alright. So, the amount of pressure which you are reading in the pressure gauge happens to be the suction pressure. So, this way and if you can measure the moisture content repeatedly alright. So, you can get the soil water characteristic. Now, this work is further being continued by SEMA. So, whenever you get time you can attend seminars and you can see what he is doing.