The primary source of dissolved silica in groundwater is the chemical breakdown of silicate minerals/rocks by chemical weathering process. Therefore, high silica content in groundwater implies more intense water–rock interaction that in turn is related to the residence time of contact of subsurface water with the silicate rocks, permeability and lithology.
When dissolve silica content shows a negative correlation with TDS, then what it indicates? - The majority of solute acquisition (TDS) would not have resulted from water–rock interaction? - Means TDS are related to anthropogenic rather than geogenic. What is your opinion?
Silica is insoluble in water in normal temperature and pressure conditions. TDS is the sum of total cations and anions present in water. Thus in normal condition it is not possible to have negative correlation of dissolved silica and TDS.
Ashkan very correctly pointed out the reference of Hem. It is surprising to get negative relationships between silica and TDS. I personally believe to repeat the analysis if any such problem arise, before making any conclusion.
Dr Ashkan Vafadar - Yes, the ions like Al3+ , Ca2+ , Mg2+ , Fe3+ have influence on silica solubility; it is found in literature. My question was different - it was regarding correlation between SiO2 and TDS and origin of TDS - geogenic/ anthropogenic. Thanks for reply
Dr Virendra Kumar Saxena - Sir, in general, TDS is the sum of the cations and anions in the water. The TDS comprise inorganic salts and some small amounts of organic matter that are dispersed within a volume of water. By definition, the solids must be small enough to be filtered through a sieve measuring 2 micrometers.
The solubility of SiO2 refers to a mineral containing SiO2. As per the literature, the solubility product of quartz, K=10-3.98 at 25oC and for amorphous SiO2 (s) the solubility product is about 10-2.7 (25oC).
Regarding the relation of SiO2 and TDS, the question came in my mind from an article (Khan and Umar, 2010; attached and concerned portions are highlighted). I have also confusions on findings of the paper that's why I placed the question. Thanks for your intervention. Please see the paper and provide your valuable comment/explanation. Regards - Dr Asit
Asit, mentioned published paper is related to Silica thermometer which is well known for the evaluation of aquifer/ reservoir temperature of the geothermal/ hydrothermal system. For detailed study following references may be useful : Ellis and Mahon; Fournier & Truesdell; Donal. E white and our work too.
Dr Saxena - You please see the highlighted portion of the paper - regarding SiO2 -TDS plot - here the question lies.
I will see the references you mentioned. Can you send the papers?. Regards
- Related references are classical and well known.
- available on line also.
Dr. Kenneth M Towe - Sir, the article you provided would be of very much useful to understand the sources of silica cement in sedimentary rocks. Good papers related to sources of silica in groundwater, if any more in your knowledge - please send me the same. Many thanks to you
Best regards - Dr. Asit