Dear Sudip,

Major cations: Na +; K +; Ca2 +; Mg2 +;

Regards

Bachir ACHOUR

I confirm Major cations of river samples: Na +; K +; Ca2 +; Mg2 +

Well,

Some information about the sources of Ca in river water.

Cation: - Calcium:

         Calcium is one of the most important positive ions (cations) in water.There are many sources of calcium ions in water, such as non-silicate minerals such as fluorite, anhydrite, gypsum, dolomite, aragonite and calcite, as well as silicate minerals such as lbite, anorthite, pyroxene and amphibole. Since the solubility of the metallic constituents of igneous and metamorphic rocks is low, the calcium content in these rocks is low and in sedimentary rocks there is calcium in the form of calcium carbonate, aragonite, dolomite, gypsum and anhydrite. In general, groundwater extracted from limestone and some sedimentary rocks is often difficult because of their solubility. The presence of hydrogen in water facilitates the dissolution of calcium, and carbonic acid is the most important source of hydrogen ion. Note that increasing pressure and heat increase the amount of calcium in the water.

  The concentration of calcium in potable water ranges from (10 to 100) mg / l. This amount may sometimes reach 500 to 1000 mg / l. Increasing the calcium content will change the taste of the water and reduce its ability to dissolve the soap. In water it has no harm to human health and other living organisms but it helps in building and maintaining human health. It plays an important role in reducing sodium content in agricultural wastewater. Hot water coming out of limestone and dolomite limestone contains a large amount of calcium.

Regards

It depends, but most likely : calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K) .

In some cases sodium dominates over calcium. I am awaiting to know the reasons.

Dear Sudip,

Sodium is the most abundant of all alkali metals, and constitutes 2.6% of the earth's crust. Its compounds are widespread in nature. The dissolution of rock salt deposits and the weathering of igneous rocks are two natural sources of sodium in the environment. Most soils contain 0.1 to 1%, mainly in the form of silicates such as amphiboles and feldspars. Sodium lands contain large amounts of soluble and exchangeable sodium. Usually, when the sodium content of the suspended soil is high, the groundwater content is also high, increasing the salinity of streams and rivers.

Regards

Bachir ACHOUR

Dear Sir (Professor Bachir Achour),

I am pleased to express my thanks to you for your amazing explanations.

I completely agree with you dissolution of amphiboles and feldspars can contribute Sodium to the groundwater as well as riverwater.

Sincerely

Sudip Saha

Dear Sudip,

You are welcome.

Regards

Bachir ACHOUR

calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K)

Greetings,

Four Major: Na, K, Mg +2, Ca +2;

Minor: Al +3, NH4+,As+, Cu2+, Fe2+, Fe3+, Mn2+ ( due mineral deposite sediments)

Human activities, Industrialization,. As+3, Ba2+,Cd2+, Cr2+, Cr6+, Pb 2+, Hg 2+, Ag2+, Zn 2+

Regards,

Alok

We came to know that the principal cations are Ca, Mg, Na and K. Do the composition of riverwaters change with the stages of the rivers?

Well,

The dominants pair cations in the upstream stage are Ca + Mg, while the dominant cations within the downstream stage Na + K.

Regards

The upper course of the river is dominated by Ca+Mg while in the lower course the riverwater contains more Na and K. Thank you Sir, Professor Bayan Hussein. I am interested to know if these changes in chemical composition of riverwater affect the pH and SEC of the riverwater.

Well, Cationic exchange is one of the process that make changes in chemical composition of river water , while the concentrations of the anions (Carbonate/ bicarbonates, sulfates, etc) ammonia, ammonium, nitrate/nitrite, dissolved gasses(CO2, O2, H2S, etc), and their Redox potential processes may affect the pH values between up and downstream.

Regards

In lower course when a river falls into a bay, sea or ocean the mixing freshwater with saline water may change the composition of riverwater. But when a river falls into another river can that change the composition?

Very effective discussions thank all of you for their valuable contribution. To me also, major cations in river water are Ca, Mg, Na and K. The level of these cations may vary depending on the nature and types of rock minerals over which the water is flowing.

Dear Saha,

Basically, Na, K, Mg and Ca are major cations in river water and Al, Cu and Fe are minor cations which may vary with the soil composition and catchment characteristics.

Considering the highland waters to down stream water several ions are mixed together due to different characteristics of the catchments. If its a major river basin, it has several other tributaries and those are related with different catchment characteristics. Therefore, the composition of water can be changed due to tributary water and some times getting dilute the pollutants may due to increase of amount of water in main river.

Normally Na, K, Mg ions are in increasing trend towards to the down stream due to sea water intrusion to the inland waters. Therefore, conductivity values may higher than up stream water.

Al, Cu and Fe concentrations may depends with the soil characters, industries and land use practices in the study area.

In Sri Lankan water:

Major (Na, K, Mg, Ca), Next group (Fe, Al, Mn) in river water

Referances:

https://www.researchgate.net/publication/280830950_Variation_of_Trace_Metals_in_Liquid_and_Suspended_Phases_of_Water_in_Middle_and_Lower_Catchments_of_River_Mahaweli_Sri_Lanka?_sg=MzK-gZTUXqvy58S_XUrAUWiGCbJIiUFo-Rm1541nwyawuK1fpKPWoUH3R2XGKQcgdv0Vkj9lyYa4twhSS95oAesKtlPx_-tNjfNVn2if.uJChj66xMw6SW3eRsVVcN1KylsLjINcKwA0OIbaHmOUjH1SH0VIA6yEQr4n942-AaLnLBsyuNfFIWZrzhnaGKA

Seasonal Variations of Water Quality of Downstream Catchment of River Mahaweli

Piyal

I am very pleased to know about the chemical composition of Sri Lankan water, Sir Dr. A. G. Piyal Aravinna. Sir is the amount of sodium greater than Ca. Thanks Sir.

Sudip Saha

Dear Sudip Saha,

Please read this Paper given below It shows the situation of the largest river basin in Sri lanka.

https://www.researchgate.net/publication/309575221_Seasonal_Variations_of_Water_Quality_of_Downstream_Catchment_of_River_Mahaweli?_sg=MzK-gZTUXqvy58S_XUrAUWiGCbJIiUFo-Rm1541nwyawuK1fpKPWoUH3R2XGKQcgdv0Vkj9lyYa4twhSS95oAesKtlPx_-tNjfNVn2if.uJChj66xMw6SW3eRsVVcN1KylsLjINcKwA0OIbaHmOUjH1SH0VIA6yEQr4n942-AaLnLBsyuNfFIWZrzhnaGKA

https://www.researchgate.net/publication/309575221_Seasonal_Variations_of_Water_Quality_of_Downstream_Catchment_of_River_Mahaweli?_sg=MzK-gZTUXqvy58S_XUrAUWiGCbJIiUFo-Rm1541nwyawuK1fpKPWoUH3R2XGKQcgdv0Vkj9lyYa4twhSS95oAesKtlPx_-tNjfNVn2if.uJChj66xMw6SW3eRsVVcN1KylsLjINcKwA0OIbaHmOUjH1SH0VIA6yEQr4n942-AaLnLBsyuNfFIWZrzhnaGKA

Major cations (Ca, Mg, Na, K) and metals ( Fe, Al, Mn) minor or trace in water samples.