1. By IRIS Mbani Kabory AND fatai Balogun
Determination of Potassium levels in water samples from 4 Monitoring wells ON Isle of hope, Wormsloe, GA. By
IRIS Mbani Kabory AND fatai Balogun

2. OUTLINE INTRODUCTION METHODOLOGY RESULTS Possible sources of error CONCLUSIONS

3. INTRODUCTION
Ocean surges onto low-lying coastal areas, caused by tropical storms have been known to have major impacts on ground water in such areas.
Salt water intrusion and presence of bacteria are usual indicators for the encroachment of salt water into fresh water aquifers. However, the former will be examined for the purpose of this work.
Ca/Mg, Cl/Si, Na/Cl and Br ratios are typical salt water intrusion indicators. However, other elements such as Ca, K and Sr are not necessarily strong indicators of saline water intrusion.
For the purpose of this work, concentration levels of Potassium in four monitoring wells on the Wormsloe State Historic Site, Georgia will be investigated using the Atomic Absorption Spectrometry.

4. INTRODUCTION Cont’d
Figure showing network of wells on the Wormsloe Historic Site
Figure showing water classification based on the USGS system
Diagrams were adapted from a conference presentation by Bush, Farley and Meyer (2016).

5. Methodology cont’d
Ground water samples from 4 monitoring wells were collected in a 5l plastic container and stored in the refrigerator at a temperature of 4⁰C.
100ml aliquot was collected from each bottle, into 4, labelled 250ml Erlenmeyer beakers.
3, 30ml replicate samples was syringed from each beaker and filtered using a 0.22µm PES filter membrane.
The filtrate was collected in 12 labelled, 50 ml centrifuge tubes and stored back in the refrigerator for further preparation.

6. Methodology cont’d AAS Specifications
The method adopted for this work was modelled after the u.s.e.p.a. Method 258.1(Methods for Chemical Analysis of Water and Wastes) for detection of Potassium using the Atomic absorption, direct aspiration technique.
Using the method, optimum Concentration range of the instrument is : mg/l at λ of nm.
However, turning the burner head a complete 90⁰, reduces the sensitivity for Potassium, but the maximum operating range increases from 2 mg/l to 20 mg/l. Another option of increasing the dynamic range is to use λ of nm
Sensitivity : 0.04mg/l
Detection Limit: 0.01 mg/l
Hollow Cathode Lamp: Potassium
Fuel/ Oxidant : C2H2/ Air

7. METHODOLOGY cont’d
100 mg/l of KCl stock solution was prepared by weighing grams of KCl crystals into a 1L volumetric flask and filling to the mark with DI Water.
15 ml preliminary calibration standards of concentrations (1mg/l, 10 mg/l and 20 mg/l )respectively were prepared by diluting original stock solution with 18.2ΩM DI water . Calculations for preparation of the standards are given below;
Using dilution equation C1V1 = C2V2 Where; C1 and C2 are concentrations of the stock solution and required standards respectively. V1 and V2 are required volumes of the stock and standard solutions respectively.
1 mg/l : 100mg/l x V1(ml) = 1mg/l x 15ml V1= 0.15ml C2 : 0.15ml ml DI Water
10 mg/l : 100mg/l x V1(ml) = 10mg/l x 15ml V1 = 1.5ml C2 : 1.5ml ml DI Water
20 mg/l : 100mg/l x V1(ml) = 20mg/l x 15ml V1 = 3ml C2 : 3ml + 12ml DI Water
Preliminary investigations were also made on the samples. 15ml of undiluted water sample from each Monitoring well was prepared for AAS analysis

8. Concentration of standard (mg/l)
METHODOLOGY cont’d
“Getting our feet wet”
Standards prepared from 100mg/l KCl Stock solution
Concentration of standard (mg/l)
Absorbance
1.0
0.141 10
1.827 20
2.700
Reconnaissance analysis of undiluted samples
Unknown Samples ID
Absorbance
MW1
0.041
MW2
0.312
MW3
2.768
MW4
0.956

9. METHODOLOGY cont’d “The real deal”
200 mg/l of KCl stock solution was prepared by weighing grams of KCl crystals into a 1L volumetric flask and filling to the mark.
30 ml preliminary calibration standards of concentrations (0.25mg/l, 0.5 mg/l , 1.0 mg/l, 1.5mg/l , 2.0mg/l and 3.0mg/l). Calculations for preparation of the standards are given below;
Using dilution equation C1V1 = C2V2 Where; C1 and C2 are concentrations of the stock solution and required standards respectively. V1 and V2 are required volumes of the stock and standard solutions respectively.
0.25 mg/l : 200mg/l x V1(ml) = 0.25mg/l x 30ml V1= 37.5µl C2 : 37.5µl ml DI Water
0.5 mg/l : 200mg/l x V1(ml) = 0.5mg/l x 30ml V1 = 75µl C2 : 75µl ml DI Water
1.0 mg/l : 200mg/l x V1(ml) = 1.0mg/l x 30ml V1 = 150µl C2 : 150µl ml DI Water
1.5 mg/l : 200mg/l x V1(ml) = 1.5mg/l x 30ml V1= 225µl C2 : 225µl ml DI Water
2.0 mg/l : 200mg/l x V1(ml) = 2.0mg/l x 30ml V1 = 300µl C2 : 300µl ml DI Water
3.0 mg/l : 200mg/l x V1(ml) = 3.0mg/l x 30ml V1 = 450µl C2 : 450µl ml DI Water

10. METHODOLOGY cont’d “The real deal”
Due to the low absorbance values obtained from analysis of water samples from wells 1 and 2, no dilution was carried out on them.
However, absorbance values of and btained for Wells 3 and 4 respectively, gave an indication that dilutions are required for these water samples. The six (6) water samples were diluted by 10 fold.
Using dilution equation : Dilution Factor = Solution Volume/ Concentrate Volume . Where; DF = 10 & Final solution vol. =30ml
10 fold = 30ml/Concentrate volume. Therefore, Volume of Concentrate needed is 3ml.
To achieve a final solution of 30ml, 3 ml of concentrate was diluted with 27ml of DI water.

11. METHODOLOGY cont’d “The real deal” Absorbance values for the standards
Concentration (mg/l)
Absorbance
Standard Deviation
0.000
0.25
0.032
0.0007
0.5
0.056
0.0011
1.0
0.125
0.0082
1.5
0.173
0.0025
2.0
0.236
0.0063
3.0
0.359
0.0066

12. RESULTS Sample ID Absorbance Standard Deviation MW1-1 0.060 0.0013
0.0009
MW1-3
0.058
0.0011
MW2-1
0.302
0.0083
MW2-2
0.0023
MW2-3
0.298
0.0039
MW3-1
0.125
MW3-2
0.126
0.0028
MW3-3
0.123
0.0015
MW4-1
0.075
0.0014
MW4-2
0.076
0.0010
MW4-3
0.074 12

13. “Bracketing the samples”
Sample ID
Absorbance
Standard Deviation
0 mg/l
0.000
0.0000
0.25 mg/l
0.031
0.0064
MW1-1
0.063
0.0009
MW1-2
0.065
0.0088
MW1-3
0.060
0.0011
0.001
0.5mg/l
0.055
0.0008
MW4-1
0.077
MW4-2
0.076
0.0020
MW4-3
0.074
1.0 mg/l
0.126
0.0024
MW3-1
0.127
0.0021
MW3-2
0.0082
MW3-3
0.123
0.0017
0mg/l
1.5 mg/l
0.170
0.0018
MW2-1
0.302
0.0040
MW2-2
0.305
0.0037
MW2-3
0.306
3.0 mg/l
0.352
0.0043

14. RESULTS cont’d Sample ID Absorbance (average) Standard Deviation
Concentration
(mg/l)
MW1
0.062
0.0025
0.51
MW2
0.304
0.0020
2.56
MW3
0.125
0.0021
10.51
MW4
0.076
0.0013
6.39

15. SOURCES OF ERROR Loss of KCl crystals while preparing stock solution.
CsCl wasn’t added, therefore, ionization interference from Sodium could have affected the results.
Concentrated HNO3 wasn’t added to the filtered samples at the time of preparation.
Since the flame works on C2H2/air combination; the burner head’s slot is probably about 10cm in length. This could result in higher percentage of aerosol reaching the flame. Hence, larger sizes of droplets are formed

16. CONCLUSIONS
Investigation of concentration levels of metals using the AAS requires a good understanding of the instruments mode of operation. Without this, Preparation of calibration standards, and sample dilutions could be a laborious task.
Samples from wells 1 and 2 showed low levels of Potassium concentration as opposed to 10.51ppm and 6.39ppm observed for wells 3 and 4.
Observation the placement of Well 3 in the LIDAR map, it appears to lying in an area of lower elevation in comparison to Well 4. Therefore, there is a possibility of inundation of this area by rainwater.
However, the absence of addition of CsCl in the standards and Samples could be responsible for the “low” concentration values observed in Wells 3 and 4, when compared to 19ppm and 51ppm (ICP results) obtained for these two wells, pre-Mathew.

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