Dr. Shiba Shankar Acharya

My central research theme focuses on the dynamic behavior of elements in natural systems, particularly through the lens of geochemistry. I explore how low-temperature geochemical reactions and surface processes influence elemental mobility. Additionally, I examine how climate change and human activities impact the chemistry of riverine and oceanic systems. These works integrate theoretical approaches and observational data to enhance our understanding of geochemical processes that shape Earth's environments and provide insights relevant to planetary sciences.

Publications (Peer-Reviewed)

10. Guha, S., Acharya, S. S., & Panigrahi, M. K. (2026). Multiproxy evidence for natrojarosite–natroalunite solid solutions in western Kutch: jarosite formation, preservation, and Martian implications', Journal of Geophysical Research: Planets, 131, e2025JE009601.

This study documents a natural natrojarosite–natroalunite solid solution in the western Kutch basin, revealing that aluminum substitution enhances structural stability and makes sodium-jarosite more abundant than potassium-jarosite. The research demonstrates that Kutch jarosite formation is an ongoing process driven by the meteoric oxidation of precursor pyrite, independent of host-rock composition. Ultimately, these mineral assemblages are preserved through a combination of regional aridity and localized acidity buffering, providing a robust terrestrial analog for understanding the evolution and stability of acid-sulfate systems on both Earth and Mars.

9. Acharya, S. S., & Dey, P. (2024). Geochemical insights into the 5.4 ka event in the eastern Arabian Shelf. Journal of Earth System Science, 133(2), 1-14.

This study examined geochemical evidence from a sediment core in the eastern Arabian Shelf to investigate the climatic changes associated with the 5.4 ka event. The findings suggest a significant intensification of the Indian Summer Monsoon (ISM) during this period, coinciding with a shift in chemical weathering patterns. This intensified monsoon phase is believed to have played a crucial role in shaping the historical development of the Harappan civilization.

8. Roy, S., Acharya, S. S., & Chakrabarti, R. (2024). Mobilization of rare earth elements during extreme weathering of basalt. Geochemistry, 84(1), 126086.

This study explores how rare earth elements (REEs) are redistributed during the intense weathering of Rajmahal Trap basalts in Eastern India. It reveals that light REEs are more retained than heavier ones, and traditional weathering indices like the Chemical Index of Alteration (CIA) fail to capture the extreme chemical weathering seen here. The findings offer insights into REE behavior in weathered environments, useful for understanding Earth's geochemical processes and provenance analysis.

7. Acharya, S. S., Hishamunda, V., & Chakrabarti, R. (2022). Natural Sources and Anthropogenic Influences on the River Water and Groundwater Chemistry of the Lower Mahanadi Basin: Insights From Radiogenic Sr Isotopes and Major Ion Chemistry. Frontiers in Water, 4, 846438.

This article investigates the sources and influences on river water and groundwater chemistry in the Lower Mahanadi Basin, India. By analyzing radiogenic strontium isotopes and major ion chemistry, it reveals that both natural processes, such as weathering of rocks, and human activities, like agricultural runoff, significantly affect water quality. The study provides crucial insights into the complex interactions between geological processes and human impacts on water systems, contributing to better water resource management and environmental sustainability.

6. Acharya, S. S., & Chakrabarti, R. (2019). Variations in trace metal concentrations and Sr, Nd isotopic compositions in sediments from two contrasting settings in the Eastern Arabian Shelf: Implications for provenance and paleoclimate reconstruction. Chemical Geology, 509, 134-151.

This article examines the major and trace element concentrations, as well as Nd and Sr isotopic ratios, in sediments from two gravity cores in the Eastern Arabian Shelf, specifically in areas influenced by the Mandovi and Zuari Rivers. It aims to evaluate the effectiveness of various paleo-redox proxies and provenance indicators in a high-sediment flux environment. The study finds that while some proxies accurately reflect deposition conditions in oxygenated waters, they fail to do so in areas impacted by an oxygen minimum zone, suggesting that U and Mo-based proxies are more reliable under such conditions.

5. Chakrabarti, R., Mondal, S., Acharya, S. S., Lekha, J. S., & Sengupta, D. (2018). Submarine groundwater discharge derived strontium from the Bengal Basin traced in Bay of Bengal water samples. Scientific reports, 8(1), 4383.

This article investigates the flux of strontium (Sr) derived from submarine groundwater discharge (SGD) from the Bengal Basin into the Bay of Bengal (BoB) and its isotopic composition. Measurements from water samples indicate that high Sr concentrations and radiogenic 87Sr/86Sr ratios, particularly at depths of 100–120 meters, suggest a significant contribution from saline groundwater. The study estimates a SGD Sr flux of 13.5–40.5 × 10^5 mol/year to the BoB, contributing up to 7% to the Sr composition of water samples from that depth, and offers insights into anomalous variations in barium concentrations and the δ18O-salinity relationship in the region.

4. Acharya, S. S., & Panigrahi, M. K. (2016). Eastward shift and maintenance of Arabian Sea oxygen minimum zone: Understanding the paradox. Deep Sea Research Part I: Oceanographic Research Papers, 115, 240-252.

This study investigates the Oxygen Minimum Zone (OMZ) in the eastern Arabian Sea, focusing on the paradox of its hypoxic nature despite the region's lower productivity compared to the west. The research identifies that Persian Gulf Water (PGW) and Red Sea Water (RSW) significantly contribute to the OMZ's eastward movement, as determined by extended optimum multiparameter (eOMP) analysis. Seasonal variations reveal a 30% intensification of the OMZ during spring and summer, even as net primary production increases by 100%, indicating a complex balance between organic matter remineralization and oxygen-rich water circulation that sustains the OMZ throughout the year.

3. Acharya, S. S., & Panigrahi, M. K. (2016). Evaluation of factors controlling the distribution of organic matter and phosphorus in the Eastern Arabian Shelf: A geostatistical reappraisal. Continental Shelf Research, 126, 79-88.

This study focuses on the Eastern Arabian Shelf (EAS), a region characterized by high primary productivity and an intense oxygen minimum zone. Through rigorous geostatistical analyses, including Empirical Bayesian kriging and geographically weighted regression, the research refines the distribution of organic carbon and phosphorus in the EAS, revealing that primary productivity does not correlate positively with organic matter accumulation. Instead, the study finds a significant negative correlation between bottom water oxygen concentration and organic matter, suggesting that anoxic conditions play a crucial role in preserving organic matter in sediments, with sedimentation rates being the primary control on organic carbon and phosphorus accumulation.

2. Acharya, S. S., Panigrahi, M. K., Kurian, J., Gupta, A. K., & Tripathy, S. (2016). Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea. Continental Shelf Research, 115, 65-75.

This study examines the distribution of various forms of phosphorus (P) and their relationship with sediment geochemistry in core sediments near Karwar and Mangalore offshore, utilizing the modified SEDEX procedure and bulk chemical analysis. It represents the first systematic quantitative analysis of phosphorus speciation in the Eastern Arabian Shelf. The findings indicate low to moderate weathering of granodioritic to tonalitic source rocks, despite high rainfall in the area, and reveal that organic bound P and detrital P are the predominant forms, followed by iron-bound and authigenic P. The study highlights that high sedimentation rates and the absence of winnowing effects significantly influence phosphorus speciation in the region.

1. Acharya, S. S., Panigrahi, M. K., Gupta, A. K., & Tripathy, S. (2015). Response of trace metal redox proxies in continental shelf environment: The Eastern Arabian Sea scenario. Continental Shelf Research, 106, 70-84.

This study explores the geochemistry of sediments from a gravity core in the Eastern Arabian Sea's oxygen minimum zone (OMZ), focusing on redox-sensitive elements like V, Cu, Zn, Mo, Ni, and U. The findings reveal that despite the suboxic environment, the sediments consistently show an oxic signature across various geochemical proxies, suggesting that seasonal fluctuations in oxygen concentration significantly influence sediment geochemistry. The research indicates that reliance on trace element proxies alone may not accurately reflect depositional redox conditions in areas with high sediment input and varying oxygen levels.

Publications (Conference Abstracts)

8. Biswal L., Acharya, S.S., Chemical Weathering Pathways of Basalt: Mineral Transformation and Element Mobility. AGU Fall Meeting Abstracts (2024), EP01-44

7. Guha, S., Acharya, S.S., Formation and preservation mechanisms of jarosite on the earth’s surface: A coupled theoretical and experimental approach. American Chemical Society (ACS) Spring, 2023,

6. Basu, A., Acharya, S.S., Evaluation of the efficacy of water-rock interaction in granitic & basaltic terrains in the present and past climate change episodes as a potential negative feedback on atmospheric pCO2 on the earth. American Chemical Society (ACS) Spring, 2023

5. Roy, S., Acharya, S.S., Mobilization and redistribution of rare earth elements during extreme weathering of basalt. American Chemical Society (ACS) Spring, 2023

4. Ganguly, S., Acharya, S.S., Chakrabarti, R., Stable Strontium Isotopic Variability in River Water and Groundwater Samples from the Mahanadi River Basin, India–Implications for Carbonate Precipitation and Clay Formation. AGU Fall Meeting Abstracts 2022, 2022, Chicago.

3. Chakrabarti, R., Acharya S.S., Mondal, S., Large Stable Ca Isotopic (δ44/40Ca) Variation in Open Ocean Samples from the Bay of Bengal. Goldschmidt, 2018. Boston

2. Chakrabarti, R., Mondal, S., Acharya S.S., Sreelekha, J., Sengupta, D,. Strontium Isotopic Evidence for Submarine Groundwater Discharge (SGD) in Bay of Bengal Water. Goldschmidt, 2017. Paris

1. Panigrahi M.K., Acharya S.S., A Microsoft Excel 2007 and MS Visual Basic Macro based software package for computation of density and isochors of fluid inclusions. Proc. ACROFI-3 and TBG XIV, 15-20 Sep, 2010, Novosibirsk, Russia, pp160-61

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