Coupling between chromophoric dissolved organic matter and dissolved inorganic carbon in Indian estuaries.

Autor: Sarma NS; Marine Chemistry Laboratory, Department of Chemistry, Andhra University, Visakhapatnam 530003, India. Electronic address: sarmanittala@gmail.com., Chiranjeevulu G; Marine Chemistry Laboratory, Department of Chemistry, Andhra University, Visakhapatnam 530003, India., Pandi SR; Marine Chemistry Laboratory, Department of Chemistry, Andhra University, Visakhapatnam 530003, India., Rao DB; Marine Chemistry Laboratory, Department of Chemistry, Andhra University, Visakhapatnam 530003, India., Sarma VVSS; CSIR-National Institute of Oceanography Regional Centre, 176 Lawsons Bay Colony, Visakhapatnam 530017, India.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2023 Dec 20; Vol. 905, pp. 167120. Date of Electronic Publication: 2023 Sep 17.
DOI: 10.1016/j.scitotenv.2023.167120
Abstrakt: This study investigates the coupling between Chromophoric Dissolved Organic Matter (CDOM) and Dissolved Inorganic Carbon (DIC) in eighteen Indian estuaries across salinity gradient of the east and west coasts during the monsoon season, characterized by significant river discharge. The hypothesis that humic acids (HA) and fulvic acids (FA), prominent in estuarine CDOM, closely correspond to the 'organic alkalinity' (A org ) component of total alkalinity is examined. In most estuaries, specifically those along the northeast coast (NE) and southwest coast (SW), a significant linear relationship exists between DIC, CDOM abundance, and pH level. Notably, minor estuaries along the southeast coast (SE) and northwest coast (NW) exhibit elevated DIC levels beyond what this relationship predicts. These estuaries also reveal heightened ammonium levels, increased δ 15 N values, and decreased δ 13 C values, indicative of anthropogenic influence. CDOM properties, such as spectral slope (S 300-500 ) and spectral slope ratio (SR, S 275-295 :S 350-400 ), align with these findings, with SE and NW estuaries displaying higher values. On average, CDOM contributes 110.5 μM (6.8 %) to DIC in NE, 390.7 μM (11 %) in SE, 24.4 μM (4.8 %) in SW, and 122.2 μM (4 %) in NW estuaries. The relationship between total alkalinity minus DIC (TA-DIC) and pH 25 suggests that CDOM, mediated by HA/FA, buffers the inorganic carbon system in estuaries. This buffering capacity weakens at elevated DIC levels, and this condition is marked by anomalous SR values compared to the baseline salinity-SR linear regression. This Study suggests that estuarine CDOM could largely represent "organic alkalinity" and could help monitor acidification in estuaries.
Competing Interests: Declaration of competing interest On behalf of all authors, I hereby declare no competing interest.
(Copyright © 2023 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
Externí odkaz: