Group 6 Laboratory Work

Laboratory Work 

On the 7th of November 2017, we completed our final assignment in the Field Works of Environmental Technology course at the Labor of the Savonia University of Applied Sciences. Our task was to carry out measurements of various parameters that are important for the representation of the water quality. We have divided our group into 3 teams of 2 persons. Each team performed different measurements and later we combined the results.

The following measurements were carried out by us:

1. Color
2. Nitrate (NO₃^-)
3. Ammonium (NH₄⁺)
4. Total Nitrogen (N TN TNT)

Color

We used the HACH 2800 meter to determine different color levels of the 15 water samples.

In the following steps we proceeded:

1. Open the measuring machine and press the button STORED PROGRAMS.
2. Select the model 120 color, 455 nm
3. Make the blank preparation: fill the first square sample cell to the 10mL marked with deionized water.
4. Prepared sample: fill 1-15 square sample cells with 10mL of water sample 1-15 respectively.
5. Wipe the blank with tissue and insert it into the cell holder with the fill line facing right.
6. Press ZERO. The display showed: 0 units PtCo
7. Prepared sample: insert the 1-15 square sample cells into the cell holder and press READ to mark the data respectively.

We have determined the following data: 

The mean of the values is 31.6 (we used only the data of 1.-14. as number 15 is probably an outlier).

The maximum of the value is 45 and the minimum is 10.

Analysis:

Considering all the 15 water samples, 13 of them are ranging from 20-45, one is below 20 and one is over 100. According to the teacher, the maximum one should be underground water.

Here are some reasons we think over about the different colors of lake water:

1. When there is much more suspended mass, the lake water will be blue-green, green, yellow or brown. When there is more humus, the lake water will be brown.
2. There is also a closed connection between lake water color and transparency: the greater the transparency is, the lake water color will be higher.
3. The general law of water color changing is: deep lake water has deep color and shallow lake water has shallow color, saltwater has deep color and fresh water has shallow color.
4. There is diurnal and annual change of lake water:for example the lake water color differs in the morning and evening. For spring and summer, water color is affected by runoff carrying sediment and for autumn and winter, color is higher.

Nitrate

Also for the determination of nitrate content in the samples, we used to measure the HACH 2800 Spectrophotometer.

Here we proceeded as follows:

1. press stored programs
2. Select the test
3.  Fill a square sample cell with 10ml of sample
4.  Perpared sample: Add the contents of NitraVer 5 Nitrate R Powder Pillow. Insert stopper into the sell
5. Press TIMER>OK. A one-minute reaction period will begin. Shake the cell vigorously until the timer expires
6.   When the timer expires, press TIMER>OK. A five-minute reaction period will begin. An amber color will develop if nitrate is present
7. Blank Preparation: When the timer expires, fill a second square sample cell with 10ml of sample
8. Insert the blank into the cell holder with the fill line facing right Press ZERO.

We got the experimental data of water samples from 1. to 15.:

Conclusion

The values of nitrate nitrogen measured by each water sample are similar, this can be used as an important parameter for analyzing water quality samples.

Nitrogen Ammonia

For this experiment our group measured the nitrogen ammonia of sample 1-8. The first step is entering the stored program number for nitrogen ammonia.  Then we rotated the wavelength dial until the small display shows: 425mm. We took 25 mL from each of the 1-8 water samples into the cuvettes and filled another 25 mL mixing graduated cylinder with deionized water, which was marked as Sample 0. We added 3 drops of mineral Stabilizer to each cylinder and inverted several times to mix. Same as before, 3 drops of Polyvinyl Alcohol Dispersing Agent were added to each cylinder and we Inverted several times to mix. We pipeted 1.0 mL of Nessler Reagent into each cylinder and invert several times to mix. For the last step, we put the sample 0 into the cell holder and press ZERO. Then we placed other samples to the cell holder one by one to measured the nitrogen ammonia.

Conclusion

Most of the data results range from 0.1-0.2 mL. Individual data are bigger than 0.2 may be due to the fact that nitrogen is usually generated due to the decomposition of nitrogen-containing organic matter in the absence of oxygen, or due to the reduction of nitrogen compounds by denitrifying bacteria.

Total Nitrogen 

 In this measurement, we have determined the total nitrogen in the water samples.

The listed devices were used in this experiment:

• HACH COD-Reactor 
  
  
• Total NItrogen Persulfate Reagent Powder Pillow
• Reagent A Powder Pillow
• Reagent B Powder Pillow
• TN Reagent C Vial
• HACH DR 2010 "spectrometer"
• funnel
• pipette

HACH COD-Reactor

The sample tubes were numbered 1-15. Each tube was added at a laboratory pipette 2 mL of a water sample. Next, Reagents A and B Powder Pillows were added to the samples. Both reagents had let dissolved well before adding the other.

addition of the reagent powder pillows

After addition of the Reagent Powder Pillows A and B, the samples were heated to 105°C for half an hour. The samples had to be cooled down to room temperature after heating in the next step.

While the heating of the samples we install the right measuring program for the measuring. We used the measuring program 350 for the Test 'N Tube Total Nitrogen with the wavelength of 410 nm.

After cooling, each sample was taken 2 ml and placed in a separate TN Reagent C Vail. All of them were also numbered 1-15.

extraction of the sample with pipette

Samples number 1-15

Each sample vial with TN Reagent C and the water sample was mixed 10 times. But it had to be worked carefully, since an exothermic reaction takes place here. 

Now the measurements can be performed, which gave the following results.

For the Zero sampling we used the zero sample, after feedback from Laura, from the group one week before.

Conclusion

Samples 1, 4, 7 are for the inflow of Iso-Valkeinen, samples 2, 5, 8 are representing the inflow of Pieni-Valkeinen, samples 3, 6, 9 are for outflow of Pieni-Valkeinen.  All three results are varying quite a lot, one being negative, and one being zero makes them irrelevant to make any reliable conclusion. Only samples 8 to 11 are indicating some existence of Nitrogen. Lakes that are containing humus and are not eutrophicated by human activities are having levels for total nitrogen 400 – 800 µg/l, which is 0,4 – 0,8 mg/l. According to this knowledge levels of total nitrogen are at a normal level. 


Samples 10 to 15 contain one exceptional outcome, but the reason for high nitrogen level most probably is a long cap from the last pumping. Groundwater task contained two samples, first was taken right at the beginning and second after pumping groundwater for 15 minutes. 2.1 mg/l was the result of the group that did this task first time in this semester, so levels had grown higher than normally. Fieldwork took a place every Tuesday, so there was one week break which during water in the well settled. Also, possible rainfalls might have affected nutrition levels in a groundwater. 


We realized during the assessing total nutrition that way of using pipet was incorrect. And the reason for this was lack of experiment of lab work. Pipetting work was done by two-person and the other one new well how to use laboratory pipet and therefore mistakes did not occur in all the vails.