nickch675
Registered: December 2015
City/Town/Province: Washington
Posts: 1
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I went camping for the first time years ago in Harpers Ferry, VA. The first week was like summer camp, where we would sleep in cabins and eat in the dining hall. The second week we would canoe to our campsite and bring along our gear. Initially I hated it, a boy from the city getting eaten up by flies in a hot and humid setting without an air conditioner. However, the experience opened up my eyes to another world far from the hustle and bustle that is the city. I came out enjoying the overall experience with a greater appreciation of Mother Nature and have ever since taken steps to contribute by joining environmental-related clubs and programs, becoming a more aware and active person because of it.
In my junior year I joined EnvironMentors, a program that aims to educate youth on the environment through a hands-on approach by facilitating fields trips and providing resources so they can perform their own independent research project, as well as a mentor whose job is in the environmental field to help with that. EnvironMentors enabled me to conduct research on the effects of types and amounts of deicing salts on the growth of plants, for which I ended up presenting at the local science fair.
Problem Statement
State and local agencies spend more than $2.3 billion annually on deicing salts, workers, and equipment for snow and ice control. According to an NBC report, about 19 million tons of salt are used in the U.S annually. Many worry about the over application of salts, especially sodium chloride, since it may contaminate our water sources, cause damage to concrete, and harm vegetation. Sodium chloride is commonly used because it’s comparatively cheap, but cities are switching to alternatives such as calcium chloride as they become aware of the environmental effects. Researchers are still trying to understand how different salts impact our ecosystem to find the most affordable, safest, and effective deicing agent.
Research Question
What are the effects of deicing salts such as sodium chloride, calcium chloride, and calcium magnesium acetate on plant growth?
Hypothesis
- Calcium Magnesium Acetate will increase soil pH because it is composed of dolomitic lime, which is commonly used in gardening to increase soil pH. It will also sustain plant growth since calcium and magnesium are elements needed for plant growth.
- Calcium chloride will cause leaf scorch because the chloride ions are absorbed by the roots, transported to the leaves, and accumulate there to toxic levels. It too will sustain plant growth since it has calcium.
- Sodium chloride will lower soil pH, show aggressive leaf scorch compared to calcium chloride, and will not sustain plant growth since sodium displaces plant nutrients, such as calcium and magnesium.
- Because salt absorbs moisture, the moisture of the soil of all plants treated will be lower since it’s taking water away from the plant. In the plants treated with higher concentrations of salt, the effects will be more obvious compared to tolerable lower concentrations.
Experimental Procedure
- Step 1: Measure the soil pH and moisture of all 21 plants to establish baseline.
- Step 2: There will be 3 salts (CMA, CaCl2, NaCl), 2 concentrations (“Low” =0.41 g/L and “High” = 1.65 g/L), and 3 plants for each concentration of each salt for replicability. There will also be 3 plants that will not be treated with salt to act as the control. Pour 100 mL of solution of each concentration for each of the three salts onto the appropriate plants.
- Step 3: Record both quantitative (i.e. dependent variables) and qualitative data (e.g. signs of leaf scorch or any other noticeable effects) and take observatory notes at regular intervals, roughly every two-three days.
Materials
- calcium magnesium acetate (CMA)
- 250 mL beaker
- sodium chloride (NaCl)
- soil
- calcium chloride (CaCl2)
- 21 plastic pots
- Water
- 21 small plants
- soil pH and moisture tester, Kelway HB-2
- American Weigh 100g x 0.01g Digital Scale
Variables
- Independent: types of salt, salt concentration
- Dependent: soil pH, soil moisture, leaf and flower color, plant height, signs of leaf scorch
- Control: type of plant, amount of water, amount of sunlight, amount of soil
Discussion
- Key Finding 1: You can see that at a certain point, the soil pH of plants treated with higher concentrations diverged downwards from the plants treated with lower concentrations. At day 14, it's a small, but substantial disparity.
- Key Finding 2: Originally, I thought since salt absorbs moisture, less water will be available to the plants, therefore the soil moisture will be lower as you add more salt. I assumed water availability was directly correlated to the moisture of the soil. These results show the complete opposite, that adding more salt will actually cause the soil to retain its moisture. Since the salt dissolved stays in the soil, so will the moisture. This does not mean however, that the water absorbed by the salt is used by the plant. It's a battle between the salt and the plant to pull in as much water as they can.
- Key Finding 3: At day 14, nearly all plants were taller than before, showing clear growth of the plants. The decrease in pH and pull for water were either tolerable by the plant or did not occur to a severe degree. Plant growth was most evident in plants treated with 1.65 g/L CaCl2 maybe because there are more atoms of calcium than there are of calcium and magnesium in a CMA solution of the same concentration since CaCl2 is lighter.
Conclusions
- The concentrations tested on the plant was not enough to cause any noticeable negative effects.
- More moisture was retained in the soil of plants treated with high concentration of salts since the presence of more salt means more absorption of water.
- The slight difference in pH between plants treated with 0.41 g/L versus 1.65 g/L suggests that a higher concentration will result in lower pH.
- If I were to do this experiment again, I would use arabidopsis thaliana plants instead because of their small genome size, ease of culture in the lab, short stature and life cycle.
- For the most accurate results when using the soil tester, it has to be deep enough into the soil until the metal plates were fully covered, which most of the times it was not. I would also use a better, more accurate scale that can read to the 0.001g because the scale used in this experiment could only read to the 0.01g and was unsteady at times.
- Lastly, I would add permeability to the list of dependent variables, which is the flow of water throughout the plant in order to see how much water it is able to get from the soil when it is absorbed by the salt.
- Because the plant was growing instead of dying, further research is needed in order to find the threshold at which each salt causes damage to the plant, and see how that compares to how much salt DC uses every winter and it's effect on the environment.
My project included 2 tiring weeks of applying salt solution to 24 plants in an effort to determine how much salt these plants could tolerate. Afterwards I was angry at the state of the plants, none of them were dying! I thought all the plants' growth, except ones that were given just water, were going to be negatively affected in some way, especially ones treated with sodium chloride. I had to figure out how to analyze data that completely opposed my hypothesis, learning in the process that science can sometimes be very surprising, and frustrating for that matter. Eventually I was able to interpret the data by looking more specifically into the parts that didn't make sense with Google and my mentor's support. My mentor, Randy, has helped me throughout my entire project, from developing a research question to presenting it. Sharing his own stories dealing with research as a grad student and how he overcame the challenges helped me to learn from his experience and overcome challenges in my research.
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