 My name is Analyne Peterson. I'm a master's student in the cell science department at North Dakota State University. And the title of my talk today is Kelsa Mass State, an alternative to gypsum for improving brine impacted soils. So first I just want to start off with some background information and this is a graph showing oil production in North Dakota over about the last 40 years or so. And as you can see since just before 2010 there was a major increase in oil production in North Dakota. And since 2012 North Dakota has been the second leading producer of oil natural gas in the United States only second to Texas. And the reason we saw this abrupt increase in oil natural gas production in North Dakota is because of horizontal drilling and cracking. And this is what a typical horizontal oil well in North Dakota looks like today. And it was only in 2006 that the first successful horizontal drilling and cracking effort was that happened. And I can explain this briefly I'm sure a lot of you know a lot more about these parts than I do. But first the well bore is drilled and that is drilled to the kickoff point which is the 90 degree turn. And that extends into the oil holding rock units and then a perforating gun is then dropped down into this that's after this is lined with some sort of pipe or casing cement concrete. And once this perforating gun is lowered into the oil holding rock units this then busts through the pipe and also busts through the in this case the upper and lower rocking scale and that's represented by the stone with the triangles there. And then this perforating gun is then removed and your fracking fluids are then pumped into this well which then helps to extend the cracks and then you can start your oil pumping operations. And so this is a map of North Dakota and this shows the amount of wells that have been drilled in North Dakota from 2007 to 2018. So this is after 2006 of course and so all these wells use horizontal drilling techniques and this also shows the bucket and three pork formation and these are our main rock reservoirs that hold most the oil and natural gas than North Dakota produces. And so since I'm kind of a geology nerd I wanted to go more into the geology of these rock units so this is a map that shows the Williston basin in North Dakota. So the far left side shows the western border between North Dakota and Montana and then as you continue further right that represents the eastern part of the state and just for some further geographical context there's an eastern river that's labeled there and then you can see the bucket and the three forks formation represented by the really light blue rock unit and an arrow there pointed towards it. So as you can see the depth of these rock units various across the state and I think the Williston basin is just a really cool sequence of rocks because there's not many places in the world where you get such a complete collection of sedimentary rocks but this is an example of one of them here in North Dakota. And so the bucket and before exclamation were deposited during the late Devonian period and early Mississippian period and this coincided with what's known as the Kaskaskia transgression this also happened during the late Devonian and early Mississippian period. So the Kaskaskia transgression is one of six well-known major rises in sea levels that we have recorded in our sedimentary rocks here and so when we have a major rise in sea level that means our marine waters inundate our continental lands and maybe large packages of marine deposits so that explains why we see so many of these marine deposits in North Dakota today and I also wanted to include a map of what our continents looked like during this time so you can see North Dakota's kind of in the center there it's part of Larasia at the time and it's also music waiter so it's kind of a tropical environment during this time and the part of this map that's represented in the blue represents land that we see today but at the time was underwater so also explains why we have such large marine sedimentary packages. So now going back to what we came here to talk about which was brine and oil production so this is what a typical brine solution can look like and as you can see a lot of the salts in the solution are precipitated out so brine is primarily composed of sodium chloride and this makes sense because we're pumping up the solution from our ancient marine deposits and the amount of brine that is produced alongside our oil varies through time but usually at the beginning of our drilling operations we see about a two to one ratio of oil to brine that's produced but through time we see that this ratio of brine to oil typically increases but on average over the total longevity of the well we see about an 18 to 1 ratio of brine to oil that's produced and brine also has electrical conductivity measurements that are often greater than 200 decibels per meter you also have total dissolved solid measurements that are also often greater than 250 000 milligrams per year and this is a map showing Montana, North Dakota and South Dakota and then we also have bocking formation again that's outlined by the red line and it's a little bit hard to see what's going on here so I blew it up just a little bit but the points on this map represent samples of brine that were taken and their color corresponds to the amount of total dissolved solids that are in these solutions so as you can see the amount of total dissolved solids is kind of all over the place but nonetheless I think it's also obvious to see that sorry that a lot of these measurements contain total dissolved solids that are greater than 321 000 milligrams per liter so why are we so concerned about brine well there's multiple reasons and first we'll start out with the negative effects that brine can have on our plant communities so if we have an excess of salts in our soils this can cause ionic stress upon our plants this can disrupt any enzyme activity and protein synthesis and if there is too many salts in our soils this can also cause osmotic stress which induces drought like conditions upon our plants this can stunt growth inhibit water uptake can also cause our leaves to wilt and if there's too much sodium in our soils this can cause oxidative stress which leads to the accumulation of reactive oxygen species and if there's too many reactive oxygen species that accumulate in our plants then this ultimately leads to the death of our plants we're also concerned about brine because it also has multiple negative effects on soil chemical and physical health so if there's too much sodium on our soil absorption sites then this poses the potential of soil dispersion so what this looks like is showing up right so the first image shows our stable flocculated soil aggregates and we can see how the water is moving through them at an appropriate rate as what's depicted by the arrows but if there's too high of an sar and they go through a wetting period then these aggregates begin to swell and we can see the water begin to pool and our water doesn't want to move through our soil aggregate so readily and if there's too much sodium on our soil absorption sites these aggregates swell to the point of dispersion and then we get little to no water movement through our soil and so the relationship between the sodium and absorption ratio and electrical conductivity is shown in the graph in the upper left so for example we have a high sar and a low ec will likely be some soil structural problems but we have a high sar and a high ec and it's likely we'll see a more stable soil structure and what this looks like is showing this slide here so we have two play surfaces that are represented here one has sodium on this absorption site and one has PM and both of these go through a wetting period so on the top we see that sodium exhibits extensive swelling and eventually leads to dispersion of our soil aggregates whereas calcium only exhibits limited swelling and the reason sodium on our absorption sites causes dispersion in our soils is because sodium has an affinity to be hydrated whereas calcium is not and the reason we see this is that it essentially comes down to sodium having a low charge density so sodium has a relatively large ionic radius too with this comparatively small charge whereas calcium has a charge density that's twice that of sodium so this promotes fluctuation in our soils so we know that we want calcium on our soil exchange sites rather than sodium and so historically gypsum has been the most common institute amendment that's used for our sodic and brine impacted soils and an example of what this looks like is shown in the picture right below the caption there so we have brine impacted soil aggregate and it's put into a petri dish with just water versus we have a similar aggregate that's put in the calcium sulfate solution and I think it's pretty clear to see that there's improved aggregate stability when the soil aggregate is introduced to a calcium sulfate solution and some examples of pelletized gypsum that we have on campus at NDSU so we have two examples here and so the pros of pelletized gypsum is that it's easy to find you can find the stuff in any garden section and it's also pretty inexpensive but the issue with gypsum is that it's pretty insoluble at about two to two point five grams per liter and also another issue specifically with pelletized gypsum is that there's a relatively low surface area so that this is even less conducive for it going into solution and the only way for our calcium amendments to be effective in our brine impacted areas is we need these to go into solution and another type of gypsum I want to talk about is flue gas desulphurization gypsum and many of you may be familiar with it because it's produced in North Dakota so flue gas desulphurization gypsum is produced in the coal refinery process so in these pre-treatments of coal a lot of the times there's SO2 gas that's emitted and to prevent this SO2 gas from being emitted directly into the atmosphere they go through our wet scrubbers so this gas goes through the wet scrubber and either a calcium permeate flurry or solution is then sprayed with the gas and this reacts to form calcium sulfide and calcium sulfide has no use to us so then it's horse oxidated to form calcium sulfate which then can either be used in construction scenarios or for us in our agricultural settings and brine remediation and so some of the pros of flue gas gypsum is that there's a significantly higher surface area than pelletized gypsum as it's usually kind of a powder and it's produced locally and it's even cheaper than our pelletized gypsum at about $10 per ton but I still gypsum so it's still relatively insoluble at 2 to 2.5 grams per liter and you might be thinking that there's other calcium sources that are much more soluble and one that may come to mind is calcium chloride and it is much more soluble at about 745 grams per liter and another pro associated with calcium chloride is it's easily accessible but some of the cons of calcium chloride is that chlorides are usually highly regulated especially in North Dakota so the maximum contaminant level of chlorides in our surfacing groundwater is just 250 milligrams per liter and another con associated with calcium chloride is that it's relatively expensive costing over $1,000 per ton another example of a calcium source that might come to mind is calcium nitrate this is also an extremely soluble amendment and it's also readily accessible and it's produced as a fertilizer for specialty crops such as potatoes um and but the issue with calcium nitrate is that nitrate concentrations are also regulated in our surfacing groundwater is in the maximum contaminant level of nitrates in North Dakota is only 10 milligrams per liter and I put this as a con because the price is essentially dependent on the cost of nitrogen which is a highly variable and there's other products that are sold for the purpose of sodic soil or brine spill remediation and there's a whole ton I could list here but I chose to list diesel plus which is a common one I've been seeing around lately and some of the pros of diesel plus is highly soluble it's sold as a solution and like I said it's really important to consider this in our amendments for our brine spill remediation because we need our amendments to be in solution for them to be effective but some of the cons associated with diesel plus is we still have to keep in mind our nitrate concentrations there's a little typo here I noticed that but the maximum contaminant level of nitrate is 10 milligrams per meter and so through nitrification the potential for ammonium to turn into nitrate is still there so it's something to consider and then also it's listed that there's active potassium in diesel plus I wasn't sure how much there was because I didn't find a clear chemical composition of diesel plus it was only listed that there was active calcium potassium and ammonium but we still have to keep in mind that potassium is still considered a soil dispersive agent such as like sodium although it only has half of the dispersive properties of sodium so something to consider in something like diesel plus and the price of diesel plus is unclear I couldn't find the price of just buying the solution or even the services or services associated with applying it so that was kind of unclear for me and also like I said the composition of something like diesel plus is created here so we have our insoluble salt such as gypsum we have our other calcium sources that pose threats to our ground water safety and other things that are marketed for brine spill cleanup but I mean I feel like there might be other options so this prompted the idea of why not use calcium acetate as an alternative to gypsum for brine spill mediation and calcium acetate has about the same amount of calcium that gypsum does and it's much more soluble than gypsum and calcium acetate is much more expensive than gypsum but the thought is that less time and less water is needed to put calcium acetate into solution and to allow calcium to replace sodium on soil exchange sites to ultimately improve the saturated hydraulic connectivity and just to hone home kind of the importance of our amendments liability here's a map of North Dakota and this shows precipitation values from April to September over a 30-year period and as you can see in our western oil producing counties their rainfall really exceeds 14 inches so something important to consider so to investigate to see if calcium acetate is a good alternative to gypsum I use a brine impacted soil from Mackenzie County North Dakota and the corresponding soil information is shown in the upper right hand corner so I tested this against other amendments pelletized gypsum and flue gas gypsum and I mixed these different amendments with my soil at five different rates at zero tons per acre one five ten and then finally 20 tons per acre and so just to recap that's a lot of numbers we had three amendments at four different rates and then four rates or four reps of those and then four reps of control which equals 52 total runs for measuring my saturated hydraulic conductivity and this was my saturated hydraulic conductivity methods so my soils were packed into tempi cells using methods similar to those by Sommerfeld at all so about a centimeter of my soil is now to the cell at a time then I would tap the edge of the cell to allow the soil and to settle and compact a little bit and then I disturbed this surface to prevent any artificial boundary from forming within the tempi cell and once all of these were assembled I randomized them amongst the tempi cell holders this is kind of shown in the upper right hand corner there and then I attached these to a main water reservoir and that's shown in the lower left hand there and once the water was turned on I collected the leachate that moved through the tempi cells in increments of 15 to 25 milliliter increments and this is determined to be about a half of a pore volume and so then my saturated hydraulic conductivity was then determined by the time it took for the volume of water to move through the tempi cells and just an example of what a tempi cell looks like shown on the lower right so we have the top and bottom of the tempi cell which above and below that is a stainless steel screen so this just helps to distribute the water over the soil surface a bit more evenly and then we also have our filter paper which helps to retain so particles and then the main form the center which holds the soil and these were the results so this graph shows my average saturated hydraulic conductivity values on the y-axis is the case that measured in centimeters per hour and then on the x-axis we have our amendments with their corresponding rates so I'll just start with the furthest left columns which kind of serves as our control and you see very minimal saturated hydraulic conductivity in those soils and then next I want to talk about maybe our pelletized gypsum so we can see that at all rates of our pelletized gypsum these are all labeled D's this means that we didn't see a significant difference in any of the rates of our pelletized gypsum from our control and then moving on to our flue gas gypsum these are labeled C and BC and then C and C so this means that amongst any rate of flue gas gypsum we didn't see any significant difference between each of those runs but we did see a significant difference between the flue gas gypsum amendments and the control and then finally moving on to the calcium acetate um with calcium acetate we did see a significant difference in parts from the control and we also saw that with increasing rates of calcium acetate we did see an increase in saturated hydraulic conductivity so where do we go next so I only did this in the lab ideally we could bring this to a field setting and this is what something like that may look like so of course we'd start with our brine impacted soil we have our high ec values our high sar values and a lot of the times in this situations we see a soap crust that accumulates on the surface and sparse vegetation and then we would apply our calcium acetate to the surface and then we would irrigate this would allow ourselves to solubilize and an important thing to consider during this step is we need to maintain the ratio between our sar and our ec just to maintain flocculation and once everything is in solution then our calcium is able to replace sodium on our soil absorption sites this is going to decrease the sar increase our saturated hydraulic conductivity and reduce the risk of plate dispersion and so once we have calcium on our soil exchange sites and we could collect sodium and chloride through something like tile drainage and then we would safely dispose of the solution through something like deep injection and then another next step in this process would be to investigate if the acetate anion from calcium acetate serves as an available carbon source for soil microbes and this would be good for promoting microbial activity as this is kind of a part of reclamation but a lot of work has yet to be done on that but it looks pretty promising and here are some sources that I use to talk together today and that concludes my talk of using calcium acetate as an alternative to gypsum for improving brine impacted soils