Effects of Phosphate and Nitrate on Pond

WaterBy Claudia PhillipsSeptember 6, 2014

Block Two

INTRODUCTION

This lab was designed to study and observe the effects of phosphate and nitrate applied to pond water (1). Phosphorous, commonly used in fertilizers, is a necessary and vital element for life but can enhance the effects of eutrophication (the over-enrichment of nutrients in water) (2). Nitrate is a common source of food for most algae, but too much can make living conditions in water harsh (3). They are both common pollutants found in fresh water systems throughout the world.

The lab’s main objective was to analyze how the two compounds physically affect fresh water. Through a daily detailed analysis and recording of data, my group and I modeled the large-scale effects that pollutants such as phosphate and nitrate can have on fresh water systems.

The lab was designed to test the hypothesis that if nitrate and phosphate were applied to pond water repetitiously over the course of 10 days, then the phosphate would kill off any algae or bacteria growing and the nitrate would enhance and feed it. Recalling that phosphorous is used in fertilizers and manure, and knowing that it is a pollutant, I surmised that the compound would have a negative effect on the pond water. Nitrate, also used in fertilizers, is also found in private and public water and is regulated by the EPA (4). Drawing from this, and knowing that algae feed on nitrate, I predicted that the algae would grow due to its excess in food supply.

METHODOLOGY

The methods followed in this lab are outlined in Lab-Aids™ #20 Pollutant Effects of Phosphates and Nitrates (5). My group and I filled 7 containers with pond water and throughout the course of 8 days, applied a consistent amount of phosphate, nitrate, and phosphate and nitrate solution to the cups (Table 1).

Cup # Solution1 None - Control2 9 drops phosphate solution3 18 drops phosphate solution4 9 drops nitrate solution5 18 drops nitrate solution6 9 drops phosphate and nitrate solution7 18 drops phosphate and nitrate solution

Table 1 Drops of each solution added per day per cup

Every day after adding the drops, we monitored the cups and recorded our observations into a data table. After we were finished each day, we placed a white paper towel across all cups and placed it under a heating lamp to be turned on until it was time again the next day to monitor the investigation.

RESULTS

Overall, we found that the nitrate and phosphate solution produced more algal growth than any other solution.

The first day, each cup of water had a similar green-tinted appearance (Figure 1). The sample of water was taken from West Lake in Apex, North Carolina. This day, all we did was record its appearance and administer the drops.

Fig. 1 Water containers at day one. Cups were a greenish-brownish tint and contained few particles of dirt, algae, and other miscellaneous material found in ponds. Photo courtesy of Adrian

Pavone.

As time went on, a very clear pattern began to show itself. Cup 6 promptly began to grow more algae than the others (Figure 2). Cup 6 contained 9 drops of phosphate and nitrate solution.

Fig. 2 Cup 6 at day two. Some algae growth at the bottom around the edges. Photo courtesy of Adrian Pavone.

The only other cup to show growth from days 2 to 3 was Cup 3, which contained 18 drops of phosphate solution (Figure 3). Day three showed the same results. Only until day four did the other cups begin to show signs of algae growth (Figure 4). Cups 3, 6, and 7 showed the most algae growth at this point in time (Figures 5-7).

Fig. 3 Cup 3 at day two. Some algae growth at bottom, few particles around edge of bottom. The effects of the solutions began to show in most cups around this day. Photo courtesy of Adrian Pavone.

Fig. 4 All cups on day four. Green color and particles can be seen at the bottoms of all cups. Cup 6 (second row, far right) has the most growth at this point. Photo courtesy of Adrian Pavone.

Fig. 5 Close up of Cup 6 on day four. Cup 6 showed the most substantial growth. Photo courtesy of Adrian Pavone.

Fig. 6 Close up of cup 7 on day four. This cup showed the second most substantial growth at this point. Photo courtesy of Adrian Pavone.

Fig. 7 Cup 3 on day four. This cup displayed the third most substantial growth on day four. A few particles were seen at the bottom. The rest of the cups showed very little but still significant growth

compared to the days prior. Photo courtesy of Adrian Pavone.

The next three days, school was not in session therefore we could not record data for the experiment. As a precaution, the day before the 3-day weekend my partners and I added triple the amount per day of each solution to each cup. Returning to school the following Tuesday, we found a drastic change to each cup than what we had previously been observing. Every cup had a very noticeable amount of algae, even Cup one, which was the controlled cup. Still, some cups had more than others. Cup 6 yet again displayed the most algae growth on day 8 of the lab (Figure 8). Several algae particles and a mass of green growth was found at the bottom of the cup, mostly in the grooved edge. On Day 8, we added double the amount of solution drops to account for the previous day.

Fig. 8 Cup 6 on day 8, the day upon returning to school. Exceptional amount of algal growth on the bottom of the cup after applying triple the amount of phosphate and nitrate solution. Photo courtesy of

Adrian Pavone.

Day 9 of the experiment, the last day of observation, showed little change from that observed on day 8 (Figure 9). More algae grew at the bottom at the same pace, but no drastic changes occurred except of that in Cup 3. Cup 3 showed a dramatic change overnight it seemed. A lot more algae growth occurred. Although nothing like Cup 6, Cup 3 showed significant growth in just over a day compared to the other cups that showed either a staggered or slow amount of growth. This can more than likely be attributed to the doubled amount of drops we applied the previous day.

Fig. 9 All cups on day 10, the last day of the lab. Cup six (column one, middle) having the most growth while the others had significant particles. Cup four displayed the least amount of growth in this lab. Photo

courtesy of Adrian Pavone.

Overall throughout the duration of the experiment Cup 6 displayed the most amount of growth while Cup 4 showed the least.

DISCUSSION

To some extent, the original hypothesis that the nitrate solution added to the pond water would produce algae and the phosphate solution would kill off the algae was supported. We found that in Cup 5, the cup that received 18 drops of nitrate a day produced a lot of algae; however Cup 4, which received 9 drops of nitrate per day, produced the least. Still, the cups that produced the most algae were Cups 6 and 7, ones that received a nitrate and phosphate solution. So, to a certain extent, yes, the phosphate solution did produce the least amount of algae, but the nitrate solution alone did not produce the most amounts of algae.

The faults of the hypothesis can be contributed to the fact that a mixture of nitrate and phosphate solutions together causes a perfect balance to grow more algae. We believed that one of the solutions would cause growth while the other would inhibit it. That is not true at all. Both nitrate and phosphate result in a growth of algae. An increase in nitrate can sometimes be followed by an increase in phosphate, which in turn encourages algae bloom (6). Had I or my lab mates known that, the hypothesis would have been altered to reflect this information. The lab could have been improved by studying these samples for a longer time or having a more quantifying way to measure the algae. Recording only observations sufficed for this short-term experiment, but having a way to physically record the growth of the algae in a numerical format would have been more beneficial to see the full extent of algae growth.

CONCLUSION

This models human activity’s effect on fresh water environments. Through research and these observations, I learned exactly how this occurs. Too much nitrogen and phosphorous in water, especially drinking water, can result in nutrient overproduction which results in polluted water.  Excess nutrients cause algal and bacterial growth. When this occurs at the surface of water, the layer of algae prevents light from reaching the bottom of the body of water, killing or reducing the life quality of plants below the surface (8).

CITATIONS

1. Perlman, Howard. "Phosphorus and Water." Phosphorus and Water: The USGS Water Science School. USGS Water Science School, 17 Mar. 2014. Web. 04 Sept. 2014. <http://water.usgs.gov/edu/phosphorus.html>

2. "Eutrophication and Hypoxia." Eutrophication and Hypoxia. World Resources Institute, n.d. Web. 04 Sept. 2014. <http://www.wri.org/our-work/project/eutrophication-and-hypoxia>

3. "Nitrates and Their Effect on Water Quality." Wheatley River Improvement Group, n.d. Web. 4 Sept. 2014. <http://www.wheatleyriver.ca>.

4. "Nitrate in Drinking Water." EPA, 5 Feb. 2014. Web. 04 Sept. 2014. <http://water.epa.gov/drink/contaminants/basicinformation/nitrate.cfm>

5. "Lab Aids." Pollutant Effects of Phosphates and Nitrates. Course Handout. Aug 29 2014.6. "Water What-ifs." Science Junction. North Carolina State University, 24 Feb. 2000. Web.

04 Sept. 2014. <http://www.ncsu.edu/sciencejunction/depot/experiments/water/lessons/np/>.

7. "Nutrient Pollution." The Problem. EPA, 16 Mar. 2014. Web. 03 Sept. 2014. <http://www2.epa.gov/nutrientpollution/problem>.

8. Khan, Fareed A., and Abid Ali Ansari. "Eutrophication: An Ecological Vision."The Botanical Review 71.4 (2005): 449-82. Web. 6 Sept. 2014.