Since the ionic species have different oxidation numbers, one can not extrapolate a value of TDS expressed in meq / l. It would at least need to know the relationship between the dissolved ionic species, information obtainable having the data represented on a diagram of Piper and Schoeller. Sorry.. ;)
It 'available some diagram showing the ionic ratios of your water samples?
Total dissolved solids (TDS ) is sum of cations and anions in water. This is reported in mg/l or in ppm. Where as Milli equivalent per litre( meq/L) is also based on individual meq/L values of cations and anions. If such unit conversion is require than ppm value should be elaborated to concentration of individual ions and further converted to meq/L.This is require to check the accuracy of chemical analysis. Furthermore, the meq/L of cations must be equal to meq/L of anions. Thus error can be quantify from this.
Dear Dr. Enrico, I used different diagrams (such as piper, Durve,...) for water type and I have ionic ratios in Meq/L for my samples. Do you mean we can calculate TDS in Meq/L by these ionic ratios?
The ideal situation would obviously know the contents of individual species; However, when they have diagrams, working on it, you can get the reports and then roughly estimate quantities in eq/l starting from the value of the TDS. It 'a manual job that requires time; therefore, it all depends on the number of samples to be considered
I am really grateful Dr Enrico and Liguang. Actually, I think it will be time consuming task. I have TDS values in mg/l and all ionic ratios in Meq/l. I just found some groundwater chemistry analysis in a research paper, which compare TDS and some ionic ratios both in Meq/L . since report TDS in Meq/l is not usual I tried to find answer for that. I try to do my analysis based on TDS in Mg/l, seems it is more reliable.
TDS is the mass of all dissolved components in the water sample. So the first attempt needs to include an estimate of the mass of inorganic compounds; thus excluding the organic fraction. Then there are some different empiric relations depending on the ionic composition of the water. At the moment I have none available, but i could support you if you can describe the composition.
In directly and approximately this is possible to covert, mg/lit to meq/lit. Usually in water composition, Na,K,Ca, Mg are major cations and Cl2, HCO3, SO4 are major anions and these reported in mg/lit or in ppm and these ions can be converted into meq/lit by using simple indusual factors. It is noted, these are the ions those have major contribution for TDS. Thus adding these may be very approximately TDS value in meq/lit.
Try with cryoscopic delta T. It depends on total molarity of solble inorganic ions.
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Since Equivalent Weight of Total Dissolved Solids in each case is variable( not constant) , hence TDS in mg/l can not be converted into meq/l
Supriya, you are correct, because TDS is sum of total cations and anions and each ions have different equivalent weight hence it is not possible to convert TDS in mg/lit to meq/lit. It is better you convert each ions in meq/lit and than sum it.
Dear Tahoora Sheikhy Narany
you can find the answer on your question in bellow file or link ,
regard
Alaa Ghadhban Khalaf
Msc Geomatics engineering
PhD student / Geomatics engineering
https://www.dropbox.com/s/rqq9y8lbxevps2s/convert%20mg%20to%20meg.pdf?dl=0
Yes, you can follow the following rule.
meq/L = (mg/L) / EW
where,
meq/L = Millie equivalent per liter
mg/L = milligram per liter
EW = equivalent weight)
Same view with Dr V.K. Saxena for his good explanations in a brief way, thank you.
You can follow the following rule.
meq/L = (mg/L) / EW
where,
meq/L = Millie equivalent per liter
mg/L = milligram per liter
EW = equivalent weight)
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