Physico-chemical parameters of traditional salt producing springs of Ancient Assam, Northeast India

Abstract

Three salt springs of ancient Assam (currently in a part of Assam and Arunachal Pradesh, Northeast India) situated in the Mohong area (Phullung and Khela) and Samkhor have been studied to bring out their physico-chemical characteristics by using ionic concentration ratios along with SEM and EDS techniques. The high TDS values of the studied salt springs (wells) under investigation infers mildly brackish water type. The Disang Group of rocks are the dominant lithotypes connected with the spring. The positive correlation between Na⁺ and Cl^- indicates the samples have an origin including halite (NaCl) dissolution, which may imply that the study area's saline and salty springs come from the incongruent dissolution of halite. The larger concentrations of almost all ionic values of Cl^-, SO₄^2-, Ca²⁺, Mg²⁺, and K⁺ were found in Phullung and Khela, while lower values were found in Semkhor, which suggests that from Semkhor to Phullung and Khela (i.e., towards northeast), the concentration of salinity increases. The occurrences of the development of crystal phases in the SEM and EDS results also substantiate the salinity increasing trend towards the northeast. The studied samples have lower Na⁺/Cl^-, K⁺/Cl^- and SO₄^2-/Cl^- indicating a deeper aquifer source and minimal anthropogenic impact. The average value of sodium absorption ration (SAR) of 30.62 indicates that the studied water quality is not permissible for agricultural use. The negative BEX values ranging from -20.58 to -203.74 suggest that the aquifer of the studied well are being salinized.