Duckweed Experiment

Analysis, Discussion and Interpretation of Findings:

As can be seen on the first graph, a general gradual decreasing trend in the concentration of nitrates can be observed in each of the trays excepting the control (with A experiencing a decrease of 8mg/l, B 10mg/l, C being the control remained the same, D 7mg/l and E 9mg/l respectively). Since the nitrate concentration in the control remained unaffected at around 40ml, any possible external causes of nitrate removal, other than the duckweed itself, can be eliminated. Thus, as stated in both the first part of the hypothesis and the literature (Tan 2001, Journey, Skillicorn & Spira 1991, Yang 2013, Skillicorn 2008) duckweed is indeed capable of acting as a nitrate sink. However, as can be seen

Additionally, tray B displayed both the highest rate of removal (1.11 mg/l per day) and total amount removed (10mg/l), despite having a relatively low initial nitrate concentration at 30mg/l. The inverse applies for Tray D, which, despite having a relatively high initial nitrate concentration at 40mg/l, displayed the lowest rate of removal (with an average of 0.78mg/l removed per day) and total amount of nitrates removed (7 mg/l). This is in contradiction with both the literature (Yang 2013) and the second point of the hypothesis which stated that higher concentrations would result in faster removal rates, which, from the above, can clearly be seen is not the case, thus proving it incorrect. What difference did occur is likely due to either slightly different conditions with certain samples, namely tray B receiving more sunlight due to a slight difference in positioning and thus more favourable conditions or differing amounts of duckweed present due to the non-precise measuring technique used when distributing the duckweed.

Additionally, during testing, it was discovered using the pH section of the testing

However, the rate of the removal was shown to be incredibly slow (with tray B featuring the highest removal rate at a mere 1.11mg/l per day) and, in agreement with the literature (Vanitha, Nampoothiri, Menon & Sivapragasam 2013), would suggest that duckweed would not make a fitting alternative to current means of reducing nitrate pollution in terms of practicality and efficiency, though this may be negated by massive amounts of duckweed in large scale applications such as that used in the experiments carried out in the literature (Yang 2013, Skillicorn