Measured EC and Ion Sums

Both the anion and cation sums should be 1/100 of the measured EC value. If either of the two sums does not meet this criterion, that sum is suspect; reanalyze the sample. The acceptable criteria are as follows:

100 × anion (or cation) sum, meq/L = (0.9–1.1) EC

Reference

 American Public Health Association, American Water Works Association, Water Environment Federation(1999)Standard Methods for the Examination of Water and Wastewater.

Dear Mr. Wesal Fakhri Hassan,

Thank you very much for your answer regarding my question. As a follow up question, I have read about using EC/100 as it is needed for overestimation and underestimation of ion summation (for cation and anion), first of all, I have read from my lecture notes in HTW Dresden, that this is under the assumption that the temperature is 25C, and yet the temperature is not given. Would it be safe to have this assumption? Another assumption is that, that the EC value is supposed to be under 2000 uS/cm in order for this to be credible. Yet some of the EC values are above 2000 uS/cm, which is around 2300 uS/cm. Can this still be done? I apologize for such inconvenience.

Best Regards,

Adi Seno Abyoga

Maybe this attachment will help on the iron question. The cations are sometimes evaluated without anions as for their nutrient or toxicity balance to certain plants, as plants need a certain amount of say calcium, potassium and magnesium, but not too much sodium.  

Dear Mr. William F. Hansen,

Thank you very much for your nice insights and article! I would therefore read it and as such try to find correlation to my project.

Best Regards,

Adi Seno Abyoga

Following up on Mr. Hassan's approach you can try the following. Convert your complete data sets to total cations and total anions as meq/L. Assume a +3 valence state for elevated iron in water contacting aerated agricultural water.  But try a reduced +2 valence state and see if the CAB makes a significant difference.  Cross plot the data and regress them and the correlation should be linear and positive with a high correlation coefficient.  The data points should fall directly on a 1:1 line. Use the best available data preferably 30 or more samples) to cross correlate the total dissolved ion concentration against EC  and note the slope and intercept of the line (which at low concentrations should be linear). Then take your cation only data, multiply the total cation meq/L concentration by 2, and cross plot those data against EC.  Draw a line on that cross plot that corresponds to the slope and intercept you calculated with complete ion data.  Any samples falling significantly off that line could be suspect. This approach also assumes that the calibration of your EC sensor was checked at least once a day, otherwise your EC data may be suspect.

Dear Mr. Anthony W. Gorody,

Thank you very much for your well explained and extensive methods. This is in line with my data as I also had been checking other cations as well, by doing the same thing as you said but with different cations and cross correlate it with anions, for example, after converting everything to meq/l, I made a plot out of Ca vs SO4, and Na vs Cl, to see whether there is a point in which it is not in the average distribution near the line. This way I could check whether the data is valid or not. However, It has never crossed my mind that I could also do as you have said, which is comparing the trivalence and bivalence state of the iron content. Once again, thank you very much for this, I will update my progress as soon as possible after I had done with the pre-analysis.

Best Regards,

Adi Seno Abyoga

Dear Mr. Anthony W. Gorody,

As a follow up, what's the best way to do line fitting and equation, is it possible to do it from excel, or would it be better to do it with Matlab or other softwares? I was thinking about Matlab, but I sanction about the accuracy of the equation I will received later.

Best Regards,

Adi Seno Abyoga

Any statistical software program should do. Excel is not very useful for that application.

YOU CAN USE SPSS PROGRAM TO DO LINE FITTING AND EQUATION

Adi your problem is very interesting . As I understand  Your problem is related to water for irrigation purpose. Only cations concentration are known. Problem is to know the anions. following exercise may help upto some extent.

- cations which include Ca, Mg, Na , K , Fe and others may be converted from ppm to equivalent parts per millions ( epm ). Sum  the epm of cations which will be approximately equal to summation of anions. Based on total ions ( cations + anions ) , Total Dissolved solids ( TDS ) and Electrical conductivity can be calculated by simple factors.

Dear Mr. Virendra Kumar Saxena,

Thank you very much for your insight, this is quite interesting as I have never seen in this point of view before. I am however curious, what is the reason using the conversion from ppm to epm? 

Best Regards,

Adi Seno Abyoga

Adi, thanks for your appreciation. Sum of cations must be equal to sum of anions in terms of epm only. This is the way to see the accuracy of chemical analysis of water.

 I agree that the water cation and  anion balance can be done only in terms  epm. So without knowing the analysis of the single anions and cations, a balance of ions can not be tested as the summation of cations in epm should be equal to equal to the summation of anion in epm.

Dear Mr. Aly Islam Metwally Aly,

Thank you for your reconfirmation. This is highly valuable insights to the addition of my analysis, I am going to have a discussion to my supervisor and make an update about this as soon as possible. Once again, thank you very much for everyone that was willingly and genuinely helping me.

Best Regards,

Adi Seno Abyoga

I agree with Dr. Ali and Dr. Virendrera and without knowing anions and cations concentration balance cannot be obtained to calculate electrical nuetrarility.

Dear Mr. Mohamed Hassaan,

Thank you very much for your input again. The incomplete data is one of the challenge that we met and recollection of such data is a little bit difficult due to difference in location. However, I will discuss the results again today with my supervisor and will post again the updates as soon as possible.

Best Regards,

Adi Seno Abyoga