Tracking fluorescent dissolved organic matter in multistage rivers using EEM-PARAFAC analysis: implications of the secondary tributary remediation for watershed management

Abstract

Profound understanding of behaviors of organic matter from sources to multistage rivers assists watershed management for improving water quality of river networks in rural areas. Ninety-one water samples were collected from the three orders of receiving rivers in a typical combined polluted subcatchment (diffuse agricultural pollutants and domestic sewage) located in China. Then, the fluorescent dissolved organic matter (FDOM) information for these samples was determined by the excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). Consequently, two typical humic-like (C1 and C2) and other two protein-like (C3 and C4) components were separated. Their fluorescence peaks were located at λ ex/em = 255(360)/455, <250(320)/395, 275/335, and <250/305 nm, which resembled the traditional peaks of A + C, A + M, T, and B, respectively. In addition, C1 and C2 accounted for the dominant contributions to FDOM (>60 %). Principal component analysis (PCA) further demonstrated that, except for the autochthonous produced C4, the allochthonous components (C1 and C2) had the same terrestrial origins, but C3 might possess the separate anthropogenic and biological sources. Moreover, the spatial heterogeneity of contamination levels was noticeable in multistage rivers, and the allochthonous FDOM was gradually homogenized along the migration directions. Interestingly, the average content of the first three PARAFAC components in secondary tributaries and source pollutants had significantly higher levels than that in subsequent receiving rivers, thus suggesting that the supervision and remediation for secondary tributaries would play a prominent role in watershed management works.

Comprehensive study of the occurrence and characteristics of carbon, nitrogen, and phosphorus in sediments and riparian soils of large drinking water reservoir

“…Interestingly, despite the fact that riparian soils had a higher degree of humi cation than sediments, the uorescence index revealed that humus in both sediments and riparian soils was mostly produced from biogenic sources (Nebbioso &Piccolo 2013). Compared with C1, C2 has an obvious red shift in emission wavelength, indicating that C2 has higher aromatization and molecular weight, and its molecular structure is relatively stable (Nie et al 2016). The C3 component (Ex/Em = 270,360 nm/460 nm) has only one excitation peak and one emission peak, which is de ned as the tryptophan-like uorescent component and is also believed to be increased by polypeptide substances produced by microbial activities, such as human sewage or algae eutrophication.…”

Bioremediation of Polluted Kamla River Water by Physical, Biological and Ecological Processes

“…These contaminants originate from both point and non-point sources. Stormwater runoff is another major contamination transport route, which brings treated and untreated sewage, industrial waste, petroleum hydro-chemicals and road dust into the river water [6].…”

“…The construction of hydraulic structures such as irrigation weirs or irrigation infrastructure reduces water flow velocity but increases hydraulic retention time, which facilitate sedimentation, aeration, sunlight irradiation and anaerobic reactions, resulting in improving water quality of river [6,8].…”

“…The moving bed biofilm reactors show high efficiency in the removal of COD and organic matter. The direct mixing of microbial agents with river water moderately removes NH 3 -N, COD and TP, whereas engineering-based applications of microbial agents significantly degrades organic matter and removes COD, BOD and nutrients [1,6,10,12]. However, their application should be monitored cautiously to avoid microbial contamination.…”

“…Inclusion of high capacity adsorbent materials in the matrix of floating mats enhances their contaminant removal efficiency. The hybrid, integrated, sequential and engineering-based floating bed wetlands can demonstrate the maximum water purification, efficiency and overcome the drawbacks of single constructed floating beds or wetland [2,6,8].…”