Okay, well let's start with some the simple models that you can go out there and get and download for free for both the plume and the source zone. Now Dave just a reminder what is the advection dispersion equation used for? >> That's for modeling faton transport processes within the plume. >> Okay and we talked about these simple box models can be used to model the source >> And one of our themes is that for MNA modeling, you need to consider both attenuation in the source and the plume. And many of these analytical models that we're going to talk about have the capability to model both, but with a number of simplifying assumptions. >> Mm-hm, okay, well let's start maybe by looking at a list of some of the commonly used analytical models. We got the BIOSCREEN AND BIOCHLOR. REMChlor AND REMFuel then Matrix Diffusion Toolkit and this slide talks about the first thing as what contaminants are used for. Some of them are Hydrocarbon specific with BIOSCREEN. Others are for Chlorinateds like the REMChlor model. Some you can use for anything. And then a key thing as this idea that Matrix Diffusion is becoming a more and more important process particular for MNA. Day which models can handle matrix diffusion. >> Well it looks like for REMChlor you can do that in the source. REMFuel same thing, you can model matrix diffusion in the source. And then obviously Matrix Diffusion Toolkit, that's one of the focuses of that. >> You can do both. Analyze remediation sort of the answer is no for the BIOSCREEN BIOCHLORs. MNA only. The REMFuel REMChlor they can do both. And then we talk about the platforms, some of these are Excel models and some of them are stand-alone. So that's a little bit about this. Now for us, we're going to, sort of, go through this talk and really just take one of them, which is this REMChlor model, and really sort of focus on it to tell you how it works and how you can use it to analyze MNA. >> Maybe before we do that, one more popped up on here, this REMChlor-MD at the bottom, you want to describe what that is? Yeah so that's actually a new version of this REMChlor model that's not out yet. But it will handle MD is matrix diffusion. I got two slides in the end, we'll talk about it there. Okay but here if you get this REMChlor model is built by Dr. Ron Falta at Clemson University, just Google USEPA and REMChlor. Ask the Google and they'll send you here, it's a free download and then you can run this thing. And so the way this works is, it's got both the source model and a plume model and they're connected. So in this one, you can see it's a mass balance type model on the left. It predicts this discharge. Including the effects of natural attenuation on the source but also you can analyze remediation. Then, it's connected to this analytical model over here and what does that do? >> Yeah, so, that's the plume model and you basically can simulate a mass balance you're using advection and dispersion, retardation, different degradation reactions and you can also then Seemed that you were doing some sort of remediation in there as well. >> RIght, so, Dave, just a quick question, maybe a little off topic. Who's the character in mythology who's got all the snakes in her head? >> That is Medusa. >> That's right. So the connection there is that the way that these models are connected is that that there are thousands of what are called stream tubes that are coming out of that orange box there that are then going to the plume. So the way Dr. Folta wrote this is that each stream tube then has a concentration he can sort of tune the way these thousands of stream tubes and thinking of being like thousand of snakes coming out of Medusa's head right? And then they sort of form that plume but then they will basically, these stream tubes, then will help you Its a simulate dispersion and absorption and degradation. So that's the cowder connective in there with the thousands of snakes from Medusa's head, it's the one way to think about it. So let's go a little bit more about in terms of a box models we talked a little bit about that in the last lecture, there's more power to these guys specifically what's called the power function. So, let's look at this again, this is the connection of the both terms, these are some of the key variables but then, I'll do the sources. You can put in our source to K constant just naturally there's some degradation occurring in that source material. But then, you could just, it will calculate how much is naturally washed away and then, you could actually remove some source. Then basically in the plume, what are some of the key dials that you can change? >> We got a whole separate decay rate that you can put in there to simulate remediation at the source of that lambda, you've also got dispercivity terms in the 3-dimensional directions x, y, and z. And so you can incorporate those as well. >> That's right. And one note is that you can have natural attenuation in this plume, or if you're doing some sort of remediation, you can turn up that first order decay in that plume itself and sort of make all stuff happen. But let's go to the source and we'll talk something about a little more flexibility of how you model this stuff. The graph here has got some different things, but basically it maps the progression or age of a source starting from the top right, you see where it says start, and things go down to the bottom left. The x axis is just how much mass is remaining. And if you get all the way to the left It's completely cleaned up. And on the y axis is what is that concentration? And the key point is that in rem clor and rem fuel you can turn this dial. There's something called the gamma function and with that you could sort of get these different patterns. And so on the top right it's almost like one of those step functions we talk about the previous lecture if it's really a number that close to zero the concentration stay the same even though that mass is being depleted and all of a sudden, it just hurdles down. And then on the very middle, there gamma equals 1, that's a first order decay. That's sort of like what we talked about with a first order decay, slow tail is developed. >> Sort of middle of the road. >> That's right, then you can do this. And then gamma greater than 1, sort of gets into this function where it's very dominated by this very slow matrix diffusion processes. So there a little bit of mass but it's coming out really slowly. So some people try to connect this to source architecture and what actually happening out there. So here is just some ideas that if you have sort of NAPL and it mostly it needs high conductivity zones or it pulls in homogeneous media, well, maybe you want to use a gamma that's less than one. Then this NAPL in the right-hand side, if it's mostly in the low permeability zones and it's a lot heterogeneity, well maybe you want to use something that's closer to one. But it's hard to actually connect this to real field data. So this, as you said, the middle road I think most people might simulate their sites as being this gamma of 1 and sort of use this classic first order k type process in there. >> Okay, just a couple examples how this gamma might actually be used. Let's look at data from three different TCE sites. And what's on the y axis? >> Well, that's the normalized concentration. So that's looking at concentration at sort of times zero and then plotting the concentration at other time divide by that. >> Okay, if so we're going to try to use one of these models the x axis is this time we're looking at the concentration versus time things. Here's how the different gammas might be. The green line, hey, let's use a gamma < 1, because it looks those concentrations aren't changing very much. And the blue line here, the sort of these concentrations taking a dive, but then it sort of leveled out, and so then you might use this gamma > 1. And then the red, sort of a straight line, it's this first-order decay. So that's a little bit about how the source works. Let's go a little bit into the plume. And Dave, quickly, what's going on here? >> Well these can incorporate the fact that you see degradation going on within the plume. So the y-axis is your normalized concentration then. We're starting with TCE as the parent compound here, but you see it degraded as you move down in distance from the source. That radiant from the source can we see that DCE line that blue line there have pop up and then VC cord as well >> Okay so theres a first order decay rate for each one of this but what REMChlor does says you can do this not just one place but actually >> In three different places. So here, you take that plume and you [SOUND] chop it up into three pieces. And in each piece, you can have separate decay coefficients. And sort of the thinking is is that in that red zone, maybe that's something where there's high anaerobic degradation going on. Maybe you don't need remediation in there. Then you get to this zone 2, maybe it's more aerobic, or actually they've sparging something to get rid of the vinyl chloride. Then zone three, maybe those little background rates. But then there's in each one of these boxes then you can put separate decay rates. >> So separate reaction zones basically. >> That's right, but actually it's more complicated than that. You can see here. This is our whole Plume Remediation Models and there are these nine boxes and the key ideas that each one of these space time zones can have a different decay rate for each of the chemical specie. Okay. >> And so it's sort of like, I like the term space time, it sort of reminds me a little bit about Star Trek. >> I know you are a big Star Trek fan so yeah. >> And so when you go home today, you can tell your daughter and your wife that you were dealing with space time issue at work. But if you see this today, the Y-axis is time, the X-axis is distance and so you can say in the first say the bottom part of that graph, the first basically 30 years, all natural attenuation in all three of the zones. Then you go in there from 2005, 2025, they're doing this remediation. And you can put these separate terms in there. And then basically you can populate all these different boxes with different amount of degradation going on in each one of the different boxes. >> Pretty neat, lots of options of time and space there. >> Yeah, let's just take a quick look at what the input data look like. This is for this REMChlor model again. It's got these different to zones in here but you're going to basically do the same thing. We talked about in the last lecture, there's some hydrogeology, there's some transport and there's all this degradation, the top right stuff, you'd see the nine boxes there, that's the space time stuff that you're going to put in there and you fill one of those and out for each one of the different constituents. Now one node is sort of focused on REMChlor which is this a very powerful model. You can use it to analyze sort of mediation or you can use it for analyzing MNA. But there's a new one out called REMFuel and so it handles a basically the different chemicals that are associated with the fuel degradation and particularly MTBE will degrade to what compound? >> MTBA. >> Exactly, so let has that decay change in there again, with the nine boxes, the nine space times kind of thing. Okay, let's talk about coming attraction. Okay here is the REM Chlor-MD model. Again Dr. Falta is working on this and brilliant guy, his is the guy who thought about all the snakes, the medusas, and these stream tubes, but now his reading back in all these sort of really great papers from long time ago about heat conduction. And so he's reading these things and he says I can take those same mathematical equations and approaches and put them into REMChlor and so that's what he's doing there. >> Mm-hm. >> Or he does that because heat conduction works a lot like chemical diffusion, right? >> Same type of equations. Like the Tice Equation or the Teem Equation, those are all based on heat transport type stuff. So it's a similar idea that heat's translating this stuff. This model is being funded by ESTCP, should be out sometime in 2016. But with it you can get some really nice flexibility in modeling not only the matrix fusion and the source, which REMChlor does now, but also in the plume itself. And you can model two-layer things on the right, fractured media the bottom right, multiple layers, so quite a bit of power on this thing. Coming attraction, so we'll watch out for that. But let's sort of wrap up what we did, just try to give you a quick overview of powerful but relatively simple groundwater models that can be used to evaluate MNA. The key one that we looked at here was REMChlor. >> Yeah, REMChlor is nice, it's gotta source term sort of innovative that you can control when and how the contaminants leave the source on this gamma term. >> And then the plume has a Space-Time zones to model >> Different times and places that biodegradation occurs. >> And then we touch a little bit on REMChlor-MD, and this should be an important tool because it includes matrix diffusion.
