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

The deciphering of microplastics‐derived fluorescent dissolved organic matter in urban lakes, canals, and rivers using parallel factor analysis modeling and mimic experiment

“…It was strongly and significantly related to the fluorophore's total peak intensity (Pearson's r = 0.97, p < 0.001). The levels of DOC in the surface water of Dhaka City were similar to those observed in the Sundarbans Mangrove Forest (0.9 ± 0.1 mg/L) and the Brahmaputra, a significant river in the Bengal delta, during the dry season (1.03 ± 0.23 mg/L) Niloy, Shammi, et al, 2022).…”

“…Peaks T and T uv intensity were 0.30 ± 0.08 and 0.48 ± 0.10 RU in lakes, 0.57 ± 0.32 and 0.80 ± 0.27 RU in canals, and 0.19 ± 0.04 and 0.44 ± 0.06 RU in rivers (Figure 3a). The peak W uv indicates a detergent‐like substance in the water sample (Mostofa et al, 2010; Niloy, Shammi, et al, 2022). The peak intensity was 0.34 ± 0.12, 0.44 ± 0.24, and 0.27 ± 0.11 RU in the lakes, canals, and rivers, respectively (Figure 3a).…”

“…The BIX quantifies the extent of autochthonous or biological generation of DOM within the aquatic ecosystem. BIX values ranging from 0.6 to 0.7 suggest low levels of autochthonous organic matter production in water, while value from 0.7 to 0.8 indicates intermediate and greater than 0.8 signify high level (Huguet et al, 2009; Niloy, Shammi, et al, 2022). The BIX value in the lakes was 0.70 ± 0.08, in the canals 0.81 ± 0.05, and in the rivers 0.72 ± 0.02 (Figure S2).…”

“…From the fluorescent EEM data, a number of fluorescence indices were estimated, including the fluorescence index (FI), humification index (HIX), and biological index (BIX). The indices were utilized to characterize uniform sources of organic matter and their production and decomposition processes (Niloy, Shammi, et al, 2022). FI was determined from the ratio of fluorescence intensities at emission wavelengths 450 and 500 nm and excitation wavelength 370 nm (Gao et al, 2016).…”

“…HIX < 4 specifies the existence of autochthonous, microbially degraded, and less humic DOM components. HIX > 6 denotes an increasing humic character in the components, and HIX > 10 reveals the samples contain extremely humified, highly carbon-containing, and aromatic humic DOM components (Niloy, Shammi, et al, 2022). HIX values were 2.62 ± 0.77, 2.26 ± 0.61, and 2.62 ± 0.23 in Dhaka City's lake, canal, and river water (Figure S2).…”