Biogeochemistry of the dissolved organic matter (DOM) in the estuarine rivers of Bangladesh-Sundarbans under different anthropogenic influences

Nahin Mostofa Niloy; Mashura Shammi; Md Morshedul Haque; Shafi M Tareq

doi:10.1016/j.heliyon.2022.e10228

Biogeochemistry of the dissolved organic matter (DOM) in the estuarine rivers of Bangladesh-Sundarbans under different anthropogenic influences

Heliyon. 2022 Aug 12;8(8):e10228. doi: 10.1016/j.heliyon.2022.e10228. eCollection 2022 Aug.

Authors

Nahin Mostofa Niloy¹, Mashura Shammi¹, Md Morshedul Haque^{1

2}, Shafi M Tareq¹

Affiliations

¹ Hydrobiogeochemistry and Pollution Control Laboratory, Department of Environmental Sciences, Jahangirnagar University, Dhaka 1342, Bangladesh.
² Department of Environmental Science and Engineering, Bangladesh University of Textiles, Tejgaon, Dhaka 1208, Bangladesh.

Abstract

The Bangladesh-Sundarbans is the Outstanding Universal Value (OUV) articulated by UNESCO, is under different anthropogenic stress. The present study focused on the status of estuarine biogeochemistry of the dissolved organic matter (DOM) of the Bangladesh-Sundarbans using different optical methods. Four fluorophores: Peak A (230-265/408-488 nm), Peak M (290/414 nm), Peak C (365/488 nm), and Peak W (320/410 nm), and three fluorescent dissolved organic matter (fDOM) components (two humic-like, one detergent-like) were identified in the Sundarban mangrove Rivers by Excitation-Emission Matrix (EEM) and Parallel Factor (PARAFAC) analyses. Among the three components, the terrestrial-derived humic-like Component had a high intensity in five samples among six in the Bangladesh-Sundarbans. The total fluorescent intensity and calculated dissolved organic carbon (DOC) concentration were maximum in Harbaria and minimum in Kotka and Dublar char, respectively. Synchronous fluorescence spectroscopy (SFS) identified protein-like component besides humic-like DOM. The optical indices described that natural fDOM components were from terrestrial sources, were matured, and autochthonous fDOM production was low. The DOM components were relatively lower in molecular size and aromaticity in Harbaria. However, water samples in Harbaria contained organometallic compounds that had much absorbance at 254 nm wavelength. DOM components had low energy and more π-conjugated molecules in structure in the Dublar char and Kotka. Components in Dublar char had comparatively higher molecular size and weight than other sampling stations. The Harbaria and Mongla port contained more hydrophobic and less polar substances than other stations. This study will firmly add diversified notions to future research regarding mangrove forest.

Keywords: Dissolved organic matter; Excitation-emission matrix; Optical indices; Parallel factor analysis.