Water+Chemistry

Alkalinity and the Effects of Acid Mine Drainage in Hurricane Creek

Water's ability to dissolve more substances than any other liquid have coined it as the "Universal Solvent". The dissolved minerals and gasses it collects during its cycle affect the chemistry and buffering capacity of it.  Alkalinity is a measure of the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. This is not the same thing as pH, but it does serve as an indicator for pH values. The more alkaline a solution is, the higher the pH value, ergo, the less acidic. Conversely, if a solution has very low alkalinity, it is usually more acidic. In regards to streams and river systems, most organisms can only survive within a certain range of pH values. The pH scale ranges from 0.0 to 14. Pure water has a pH of 7.0, but water as found in streams and rivers usually has a slightly more acidic value, usually around 6.8 due to run off, polution, or chemicals. If those streams become too acidic, or on the other hand too basic, very little will be able to survive within them (Wetzel, Likens 1991).

Mine drainage poses a major threat to streams across the world because it usually becomes it is usually very acidic. The EPA cites acid drainage from abandoned coal mines as the primary water quality problem in Appalachia (Appalachian Regional Commission 1973). Acid mine drainage is polluted water that normally contains high levels of iron, aluminum, and acid (Hadley, Snow 1974). Drainage acidity arises from oxidation of pyrite, the crystalline form of iron sulfide (Hadley, Snow 1974). The contaminated water is often reddish-brown in color, indicating high levels of oxidized iron (Hadley, Snow 1974). Mining disturbs pyrite and, as a result, pyrite weathers and reacts with oxygen and water in the environment (Todd, Reddick 1997).

 pH Scale:

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Why are we learning about the alkalinity of our fresh water systems? Because we need water in order survive and we need very clean water that is suitable for our bodies. Dr. Cherry explains: “Water is considered the “universal solvent” because of its ability to dissolve more substances than any other liquid. As water moves through the hydrologic cycle, it picks up many minerals, chemicals, and nutrients, and also many dissolved gases.” So, now you ask, what is alkalinity? The alkalinity of water works as a buffering capacity. “It is also a measure of the concentration of ions capable of neutralizing acids, such as carbonate and bicarbonate,” states Dr. Cherry. Precipitation picks up gases and aerosols in the atmosphere and by the time water reaches rivers, streams, and wetlands, in watersheds on the Earth, it has picked up other gases and minerals. These are acids that cause an imbalance within the water chemicals. Dr. Cherry explains, “When more acids are added, carbonate will react with them forming bicarbonate until all of the carbonate is used up. Bicarbonate will continue to react with acids forming carbonic acid until all of the bicarbonate is used up.” Basically, if we have enough carbonate and bicarbonate within our water to neutralize the acids, the pH level will remain in good shape.

We wanted to measure the alkalinity of Hurricane Creek, a watershed containing several active and many old coal mines,as well as the effect of acid mine drainage on the creek. Dr. Cherry collected water sample from five spots along the river: 1) upstream from a mine draining point, 2) The point at which mine drainage enters the creek (Point of Discharge), 3) slightly downstream and across the river from that point of discharge, 4) Further downstream at a spot known as the “M Bend,” and 5) towards the end of the creek at a spot known as “Watson’s Bend.” For this experiment then, it was hypothesized that water sampled at a point upstream from the source of acid mine drainaige would have a higher alkalinity compared to the point of discharge and then the samples taken downstream would recover and the alkalinity would go back up and have a similar alkalinity to the control water sample.

In order to test the alkalinity of Hurricane Creek, a simple titration experiment was conducted. The first step of the experiment was to fill a burette with sulfuric acid, and an Erlenmeyer flask with water sampled from Hurricane Creek. Then, the lab group placed the flask beneath the burette and added four to five drops of phenolphthalein to the water sample. If there had been any change in the color, if the soultion changed to a pink color then it would be apparent that carbonate was present in the soultion. There appeared to be no change, thus there was no carbonate present in the water. Next, the group added three to four drops of bromcresol green-methyl red indicator to the water sample. This solution determined if there was bicarbonate present. The water did change color, indicating the presence of bicarbonate. After the drops were added, a group member slowly titrated the sulfuric acid into the beaker containing 50mL of creek water until the water turned a pinkish-grayish blue color. Since bicarbonate ions are associated with known pH levels, the indicator fluid is made to change color at the point that all bicarbonate ions are neutralized. We recorded the volume of acid added to the water sample when the color change occurred. The more acid that had to be added to the solution, the higher the alkalinity was.

When adding the first indicator fluid, phenolphthalein, no change in the color occured which demonstrated no carbonate was present, only bicarbonate. This is to be expected since carbonate corresponds to a pH higher than 8.3 and Hurricane Creek averages a pH close to 7 (neutral). Resulting in the fact that there was no carbonate present, the Phenolphthalein Alkalinity was equal to zero (using the equation below). This same result was true for every water sample. Thus, all alkalinity present within the water samples was bicarbonate.

When the second indicator was added, there was a definite color change, indicating that the solutions contained bicarbonate. For our group’s particular water sample, we had to add 2.65mL of sulfuric acid to the solution in order for the indicator fluid to change colors. Each volume was plugged into the equation below in order to calculate Total Alkalinity at the site of each water sample. Table 1 below summarizes our results and matches each site with its corresponding pH value.

T µeq/L= Total Volume of Acid Used(mL) **X** Normality of Acid x 10 6 _

Volume of Water Sample (mL)

where normality of acid is 0.02, and the volume of the water sample is 50mL.


 * Table 1**.

Alkalinity data, including the amount of acid added to each water sample, the total alkalinity, and the pH.
 * = **Sample Site** ||= **P mL** ||= **T mL** ||= **Total Alkalinity** ||= **pH** ||
 * < Control (Upstream) ||= 0 ||= 2.6 ||= 1040 ||= 6.62 ||
 * < Point of Discharge ||= 0 ||= 0.95 ||= 380 ||= 6.21 ||
 * < Downstream 1 ||= 0 ||= 2.65 ||= 1060 ||= 6.97 ||
 * < Downstream 2 (M Bend) ||= 0 ||= 1.6 ||= 640 ||= 6.42 ||
 * < Downstream 3 (Watson’s Bend) ||= 0 ||= 1.7 ||= 680 ||= 6.46 ||

It was hypothesized that Hurricane Creek would have a higher alkalinity prior to the point of discharge of the acid mine drain. The results of the titration tests supported this hypothesis. As can be seen in Table 1 above, the Total Alkalinity is much higher at the sample site prior to the discharge of the acid mine drainage. It is interesting that the Downstream 1 sample also has a relatively high alkalinity. One might expect for this point to have a rather low alkalinity because it is so close to the point of discharge. However, several factors likely affected this. First, the Downstream 1 sample site is on the other side of the creek and rather close to the point of discharge. Second, there is no indication as to how wide the creek is at this point, how deep, or what the discharge is. Third, there is no measurement of the overall discharge at the point where the acid mine drain meets the creek. So, for example, if the creek is very deep and moving swiftly at this point, and the acid mine drain is moving slowly and is very shallow, the affects of that discharge would not be felt immediately, thus not at the Downstream 1 sample site.

There can be no argument, however, that the water coming from the abandoned mine is more acidic than the average pH of Hurricane Creek. With a pH of 6.21 and Total Alkalinity of 380 µeq/L, the mine drainage adversely affects the pH and thereby the health of Hurricane Creek. Drainage points like this along the creek should be stopped in order to maximize the health of Hurricane Creek.

The sample sites of Downstream 2 and Downstream 3 have a lower alkalinity relative to the other two spots along the river. There is not enough evidence to support that this particular acid mine drainage is the cause of this lower alkalinity. However, it can be assumed that there is some outside force acting on the creek that is lowering the alkalinity at the spots downstream. There is a great deal of land development along the creek after the Downstream 1 sample site that is causing large amounts of sediment to be washed into the creek. This sediment also affects the alkalinity of the creek by changing the overall water chemistry. If this sediment were to contain large amounts of limestone, for example, the creek would become more alkaline.

As stated previously, we were attempting to measure the alkalinity of the water samples from Hurricane Creek. This is necessary information because organisms within the Creek can only survive within a fairly narrow window of pH values.

In conclusion, the alkalinity of Hurricane Creek can be used to measure the habitability of the creek. It is expected for fresh flowing water to maintain a pH slightly below 7. However, if there are large amounts of acid mine drainage or sediment flowing into the river, the pH can become too acidic, thereby making it impossible for organisms to survive within the creek. The results that the class found are important because they inform concerned citizens about how companies attempt to fix the harm that they are causing our watershed. The total alkalinity raises back up after the point of discharge and is similar to the control sample which means that the water is able to neutralize the acids that may be present so that the living conditions for plants and animals are ideal. Water systems are very delicate and complicated ecosystems. They have a huge impact on the environment surrounding them, and vice versa. Thus, to protect the environment around streams and rivers is to protect those streams and rivers themselves. If Hurricane Creek is to be protected, acid mine drainage must be curtailed. In doing so, Hurricane Creek could flourish as a natural habitat for a plethora of organisms. However, this will take a concerted effort of those living and working around the creek, as well as policy makers. We can only hope that those who affect the creek can learn of its natural value and will do everything possible to keep Hurricane Creek clean and healthy.

Dr. Julia Cherry collecting a water sample at the point of discharge of an abandoned mine into Hurricane Creek. Photo by John Wathen.

Condition of water draining into Hurricane Creek at the point of discharge. Photo by John Wathen.

Dr. Cherry’s class (New-243) is concerned with measuring the Alkalinity of Hurricane Creek to monitor the new changes happening to the water chemistry in the stream. Therefore, another alkalinity lab was preformed in November-2011.
 * Methods:**

The lab performed in November had the same method as previous alkalinity tests.

In order to measure the alkalinity of Hurricane Creek water, we had to use the titration with color indicator solutions method. Hydroxide and carbonate ions are associated with pH levels above 8.3, while bicarbonate is associated with pH levels below 8.3. By using the color indicator, phenolphthalein, it is possible to determine if carbonate or hydroxide ions are present in the water sample. If it is added to water and the water turns pink, then carbonate or hydroxide is present. If phenolphthalein is added and no pink color appears, then there is bicarbonate alkalinity.

We then added acid into this solution, these ions react with the acid until all of the hydroxide and carbonate ions, and half of the bicarbonate ions are exhausted. At this point, the pink color will disappear. However, if no pink color appears then continuing to add acid will clash with the bicarbonate ions until all of the bicarbonate has been converted to CO2 and then, released to the atmosphere.

//1) Begin by completely filling a burette with N/50 (0.02N) sulfuric acid.// //2) Pipet 50 mL of water sample into an Erlenmeyer flask containing a metallic stir bar.// //Place the flask on the spin plate beneath the burette.// //3) Add 4 – 5 drops of phenolphthalein indicator to the flask. Make sure the spinner is on// //to mix the indicator into the water sample.// //4) If pink, add N/50 (0.02N) sulfuric acid slowly until the pink color disappears. If no pink// //color appears, skip ahead to #6.// //5) Record the volume of acid used up to this point to calculate phenolphthalein alkalinity.// //6) Add 3 – 4 drops of bromcresol green=methyl red indicator to the water sample.// //7) Continue adding N/50 (0.02N) sulfuric acid slowly until the solution turns a pinkish gray// //with a slight bluish tint// //8) Record the total volume of acid used up to this point to determine total alkalinity.//

Equations Used:

As stated before, the point of this lab is to measure the effect of coal mining on the water chemistry in Hurricane Creek. Moreover, Alkalinity is associated with the pH in water, which gives us an idea about whether specific organisms can survive there or not. The hypothesis was the water’s alkalinity would have been higher (basic water) before the coal mining (Control point up stream) and would have a very low alkalinity (high acidity) around the coal mining area at the point of discharge. Also, it would be very close to neutral after the point of discharge. By determining the water’s alkalinity we determined the effect coalmine pollution has on Hurricane Creek. Analyzing the control sample of water allowed us to compare it to the rest of the samples to see the significance of the pollution’s effect on the water. The results of the experiment supported this hypothesis, and the following table and chart show more illustration for the result’s details.
 * Results:**





The water was treated with Phenolphthalein, but the water sample didn’t react, which means the carbonate is absence, and according to that we can sum the result to (0mL). However, when adding bromcresol green-methyl red indicator, and 3 to 4 drops of N/50 (0.02N) sulfuric acid, the water reacted, which means that bicarbonate is present. In the upstream water sample, the total alkalinity used an average of (2.05mL) to react. By using the equation given in the method’s part, the result was Total Alkalinity (T) =820. Here is a n example of the equation: Moreover, the point of discharge used an average of (0.53mL). After using the same equation the result was T=212. At Down Stream 1 was T=764, Down Stream 2 was T=692, and Down Stream 3 was T=664. We can sum the this result in this chart:
 * T µeq/L= __2.05mL x 0.02 x 106__ = 820**
 * /50mL**



As illustrated in the previous chart, the area of discharge had lower alkalinity, which means that the water at this area has more acid. However, at the first down stream point (D.S.1) the alkalinity became high again, which means the water became basic very quickly. This means that either the alkalinity at the down stream point(s) held up against the acid level or that pure water ran down and entered the stream, diluting the acid level.

After the point of discharge, however, it is clear that the alkalinity continued to decline. Granted, it was at a much slower rate than at the point of discharge, but it is likely that Highway 216 (between D.S.1. and D.S.2.) had an effect on the acid level rising. Since the road is slightly tilted, the residue from vehicles likely washed into the water stream and effected the alkalinity level. Without further tests though, it would be difficult to determine how much the roadside impacted the alkalinity in addition to the acid from the point of discharge.

The total alkalinity chart shows that upstream Hurricane Creek has a higher alkalinity, meaning it has a high buffering capacity and ability to neutralize acids. However, the point of discharge has a very low alkalinity level, meaning that it is unable to buffer as much acidity. The buffer capacity picks back up downstream. This shows the creeks ability to neutralize the acid. Limestone, a fairly prevalent material in Alabama, helps form calcium bicarbonate in the water. When water runs over limestone and already contains carbonic acid, the limestone can be dissolved and form calcium bicarbonate. The fairly high alkalinity protects the creek from having an acidic or base pH level. It is encouraging to see that Hurricane Creek some-what regain its strong alkalinity, despite the point of discharge from the coal mining. This area has quite a low alkalinity/ buffering capacity against acids. The alkalinity definitely regains its strength at the first downstream point. The alkalinity buffers against acids and other harmful things to the ecosystem. This buffers allows the pH level to remain fairly stable around 7 on Hurricane Creek.

Coal mines exist all over this country. And streams like Hurricane Creek are often in the local area being affected. It is important to understand the affects coal mining has on the local watersheds because it drastically affects the ecosystems of the area. By testing the alkalinity of Hurricane Creek we can see how the pollution decreases the total alkalinity of the stream. The lab dated supports the hypothesis, which was found true. The total alkalinity affects all life in the stream. The pH must be at or near a neutral level in order for most organisms to live. This information can be used to inform coal mines of their repercussions. This should be done because it is important for them to provide bother preventative measures and treatment to streams like Hurricane Creek. It is important because, “Successful control of acid mine drainage usually involved both elements of prevention and treatment” (Rabenhorst).

Sources Cited Appalachian Regional Commission. The Economic Impact of Public Policy in the Appalachia Coal Industry and the Regional Economy. Charles River Associates, Inc. 1973. <span style="font-family: Arial,Helvetica,sans-serif;">Hadley,R; Snow,D., eds.Water Resources and Problems Related to Mining. American Water Resource Association, MN. 1974.

Rabenhorst, M. Acid Sulfate Soils: Problems. Encyclopedia of Soil Science. 2006 CRC Press.

<span style="font-family: Arial,Helvetica,sans-serif;">Todd, J; Reddick, K., Acid Mine Drainage. Civil Engineering Department, Virginia Tech. 1997.