Delineating sources of groundwater recharge and carbon in Holocene aquifers of the central Gangetic basin using stable isotopic signatures |
| |
Authors: | Manoj Kumar AL. Ramanathan Abhijit Mukherjee Ravi Sawlani Shyam Ranjan |
| |
Affiliation: | 1. School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, India;2. Department of Environmental Science, School of Earth, Environment &3. Space Studies, Central University of Haryana, Jant-Pali, India;4. Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur, India;5. Radio and Atmospheric Sciences Division (RASD) of CSIR-National Physical Laboratory, New Delhi, India |
| |
Abstract: | Stable isotopes of water (δ2H, δ18O) and δ13CTIC were used as a tool to trace the recharge processes, natural carbon (organic and inorganic) source and dynamics in the aquifers of the central Gangetic basin, India. Stable isotope (δ2H, δ18O) record of groundwater (n?=?105) revealed that the groundwater of Piedmont was recharged by meteoric origin before evaporation, while aquifers of the older and younger alluvium were recharged by water that had undergone evaporation loss. River Ganges and its tributaries passing through this area have very little contribution in recharging while ponds play no role in the recharging of adjacent aquifers. The connectivity of shallow aquifers of aquitard formation (comprised of clay/sandy clay with thin patches of fine grey sand), i.e. 25–60?m below ground level (bgl) with the main upper aquifer (at a depth of >120?m?bgl) was found to be higher in older and younger alluvium. Negative values of δ13CTIC (median ?9.6 ‰; range ?13.2 to ?5.4 ‰) and high TIC (median 35?mM; range 31–46?mM) coupled with low TOC (median 1.35?mg/L; range 0.99–1.77?mg/L) indicated acceleration in microbial activity in the younger alluvium, especially in the active floodplain of river Ganges and its proximity. |
| |
Keywords: | carbon-13 d-excess evaporation hydrogen-2 isotope hydrology meteoric water oxygen-18 refractory organic matter shallow aquifers total organic carbon |
|
|