Tracing fluorescent dissolved organic matter (fDOM) characteristics and water quality parameters: Insights from an urban industrial river to marine zone

This study aims to identify continuous water quality changes and identify fluo-rescence properties from urban rivers to marine zones. Various types of naturaland anthropogenic sources derived dissolved organic matter (DOM) have beenidentified in this study. These include soil-derived DOM, plant remnants, andsoluble particles produced when organic material partially decomposes and isreleased by microorganisms, such as bacteria, algae, and plants. DOM wascharacterized using a three-dimensional excitation-emission matrix (3DEEM),parallel factor analysis (PARAFAC), and water quality parameters from theBuriganga River, Dhaka to Patenga Seaport, Chittagong, along with the Shita-lakshya River, a small portion of the Padma River, and the Meghna River. Tobetter understand the data analysis, the study area was divided into three cen-tral regions: urban industrial rivers, industrial estuarine rivers, and marinezones. In the urban industrial river, 3DEEM and PARAFAC identified fivefluorophores (peaks: A, C, M, T, and T-uv) with five components: detergent-like,fulvic-like, tryptophan or protein-like, fulvic-like (C-type), and protein-like,which might originate from the industrial activities and sewage pollution. Inthe industrial estuarine river zone, three fluorophores have been identified(peaks: A, C, T-uv) with two known components, namely, fulvic acid (A-type)and fulvic acid (C-type), with an unknown photoproduct at Ex/Em=295/368(peak T-uv). Components in the industrial river zone may originate from terres-trial sources, indicating vegetation along the river. In the marine zone, fourfluorophores have been identified (peaks: T-uv, A, T, C) with two components,that is, protein- or tryptophan-like and humic acid-like from coral origin. Theintensities of both fulvic-like and protein-like substances were high in urbanindustrial river water owing to industrial activity and sewage pollution.SUVA254suggests high aromaticity in all three regions, whereas the opticalproperties suggest that terrestrial and microbial components are present in theurban industrial and estuarine rivers. This further indicates that urban indus-trial river water quality is highly polluted. The lowest degradation potential index (DPI) in the marine zone might result from the presence of the highestnumber of dissolved solids in the water, and the highest DPI of industrial estu-arine rivers explains the comparatively high presence of terrestrial-derivedhumic (A)- and humic (C)-like components in the ratio to the unknown photo-product of mid-wavelength.