An assessment of the hydrogeochemistry of two wetlands located in Bihar State in the subtropical climatic zone of India

A total of 30 water samples and 8 sediment samples were collected and chemically analysed for major ions (Na + , K + , Mg 2+ , Ca 2+ , HCO 3 − , SO 4 2− , Cl − , NO 3 − , silica, PO 4 3− , F − ), trace elements (Fe, Mn, Ni, Cd, Zn, Pb, Cu), minerals and nutrients to determine the factors that control the chemistry of water in the Kawar-Tal and Kusheshwar-Asthan wetlands in the Bihar State of India. These analyses indicate that Ca 2+ and HCO 3 − ions are the most dominant ions in both of the wetlands. It also indicates rock weathering is a major source of ions in these wetlands, particularly the dissolution of carbonate minerals. The hydrogeochemistry of water in Kusheshwar-Asthan is favouring kaolinite formation and in Kawar-Tal favouring kaolinite–gibbsite formation. Quartz (~36%), clay minerals (~21%) and chlorite (~10%) are the dominant minerals in both the wetlands. Orthoclase (~12.49%), calcite (~7.51%) and illite (4.89%) minerals are only available in Kawar-Tal surface sediment, while albite (6.29%) and biotite (~13.6%) minerals are only available in Kusheshwar-Asthan. Total carbon (~3%), inorganic carbon (0.9%), organic carbon (~2.1%), total sulphur (~0.0008%), nitrogen (~0.55%) and phosphate (~0.96%) are available in Kawar-Tal surface sediments, while total carbon (~2.38%), inorganic carbon (0.55%), organic carbon (~1.84%), total sulphur (~0.001%), nitrogen (~0.62%) and phosphate (~0.64%) are available in Kusheshwar-Asthan surface sediments. The study indicates wetlands are rich in nutrient for biological activities and are sufficient to support the biodiversity, but few locations are influenced by anthropogenic activities which cause the increase of sulphur, chloride, iron and lead.