Seasonal Variations of Dissolved Organic Matter by Fluorescent Analysis in a Typical River Catchment in Northern China

Abstract

Fluorescence (excitation-emission matrices, EEMs) spectroscopy coupled with PARAFAC (parallel factor) modelling and UV-Vis (ultraviolet visible) spectra were used to ascertain the sources, distribution and biogeochemical transformation of dissolved organic matter (DOM) in the Duliujian River catchment. Dissolved organic carbon (DOC), chromophoric dissolved organic matter (a335) (CDOM), and hydrophobic components (a260) were higher in summer than in other seasons with 53.3 m−1, while aromaticity (SUVA254) was higher in spring. Four fluorescent components, namely terrestrial humic acid (HA)-like (A/C), terrestrial fulvic acid (FA)-like (A/M), autochthonous fulvic acid (FA)-like (A/M), and protein-like substances (Tuv/T), were identified using EEM-PARAFAC modelling in this river catchment. The results demonstrated that terrestrial HA-like substances enhance its contents in summer ARE compared with BRE, whilst terrestrial FA-like substances were newly input in summer ARE, which was entirely absent upstream and downstream, suggesting that rain events could significantly input the terrestrial soil-derived DOM in the ambient downward catchments. Autochthonous FA-like substances in summer BRE could derive from phytoplankton in the downstream waters. The results also showed that DOM from wetland exhibited lower fluorescent intensity of humic-like peak A/C and fulvic-like peak A/M, molecular weight (SR) and humification index (HIX) during the low-flow season. Built-up land, cropland, and unused land displayed higher a335 (CDOM). A higher proportion of forest and industrial land in the SCs showed higher SUVA254 values. Humic-like moiety, molecular weight and aromaticity were more responsive to land use during stormflow in summer. Rainfall could increase the export of soil DOM from cropland and unused land, which influences the spatial variation of HIX. The results in this study highlighted that terrestrial DOM has a significant influence on the biogeochemical alterations of DOM compositions and thus water quality in the downward watershed catchments, which might significantly vary according to the land-use types and their alterations by human activities.

Dissolved organic matter spectroscopy reveals a hot spot of organic matter changes at the river–reservoir boundary

“…SUVA mean values measured in the different environments sampled (Ter River, plunged river, surface water in the reservoir, Riera Major, and effluents and impaired streams) showed no significant differences and hardly deviated from ~ 2.5 (Table 1). These values are in the lower end of figures previously reported in other systems where variability is observed (Jaffé et al 2008;Han et al 2021), and suggested low aromaticity (~ 20%, Weishaar et al 2003). The β:α ratio was homogeneous in the reservoir and in the Ter River (Fig.…”

The Impacts of Precipitation on Fluorescent Dissolved Organic Matter (FDOM) in an Urban River System

“…Based on the excitation-emission peak location, both autochthonous and allochthonous components were recognized. Component 1 (C1, Ex/Em = 235, 255, 295/385 nm) was categorized as terrestrial fulvic-like substances [47]. Component 2 (C2) was defined as terrestrial humic-like fluorophores (two peaks: Ex/Em = 260/460 nm and Ex/Em = 360/460 nm) [48,49].…”

Eficiencia de la remoción de materia orgánica mediante electrocoagulación para tratar aguas residuales procedentes de mataderos

“…La materia orgánica soluble presente en el agua residual (Meyo et al, 2021), tiene influencia directa sobre la conductividad eléctrica, por lo que resulta importante su evaluación en la determinación de la calidad del agua (Han et al, 2021). Al realizar la evaluación de la conductividad eléctrica, esta disminuye desde 1579 µS/cm hasta 359,35 µS/cm en el tratamiento E12V y 129 µS/cm en el tratamiento E24V (χ² = 8,366; p = 0,004), lo cual representa una eficiencia en la remoción del 77,230 % y 91,836 % respectivamente (Tabla 1).…”