Chromophoric and fluorescent dissolved organic matter in the Red River (Northern Vietnam): Hydrological-period contrasts and spatial variability

Thi Quynh Mai Duong; Nguyen Hoang Anh Chu; Van Hoi Bui; Catherine Guigue; Marc Tedetti; Vincent Grossi; Cam Tu Vu

doi:10.15625/2615-9783/25087

Author affiliations

Authors

Thi Quynh Mai Duong 1-University of Science and Technology of Hanoi (USTH), VAST, Hanoi, Vietnam; 2-Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, Marseille, France
Nguyen Hoang Anh Chu Institute of Ecology, Tallinn University, Narva mnt 25, 10120 Tallinn, Estonia
Van Hoi Bui University of Science and Technology of Hanoi (USTH), VAST, Hanoi, Vietnam
Catherine Guigue 1-University of Science and Technology of Hanoi (USTH), VAST, Hanoi, Vietnam; 2-Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, Marseille, France
Marc Tedetti 1-University of Science and Technology of Hanoi (USTH), VAST, Hanoi, Vietnam; 2-Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, Marseille, France
Vincent Grossi Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, Marseille, France
Cam Tu Vu University of Science and Technology of Hanoi (USTH), VAST, Hanoi, Vietnam

DOI:

https://doi.org/10.15625/2615-9783/25087

Keywords:

Red River, Vietnam, Dissolved organic matter, CDOM, FDOM, EEM-PARAFAC

Abstract

Dissolved organic matter (DOM) dynamics in large tropical rivers play a key role in aquatic carbon cycling, yet remain poorly documented in Vietnamese systems, particularly for chromophoric and fluorescent DOM (CDOM and FDOM). In this study, 68 surface water samples were collected along the main channel of the Red River (northern Vietnam), from upstream regions to the estuary, during the dry (March) and wet (July) periods of 2019. CDOM and FDOM characteristics were investigated using UV-visible absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). A three-component PARAFAC model identified two humic-like components (C1 and C3) and one tryptophan-like component (C2). Significant differences between the two sampling periods, representing contrasting hydrological conditions, and marked spatial variability were observed. CDOM and FDOM concentrations were significantly higher during the wet period, with CDOM absorption coefficient at 350 nm [a(350)] of 4.8±2.2 m^-1 (wet) and 1.9±0.8 m^-1 (dry), specific ultraviolet absorbance (SUVA₂₅₄) of 10.0±2.6 L mg C^-¹ m^-¹ (wet) and 4.3±0.8 L mg C^-¹ m^-¹ (dry), C1 of 118±25 QSU (wet) and 66±29 QSU (dry), C3 of 74±10 QSU (wet) and 47±23 QSU (dry), and C2 of 418±85 QSU (wet) and 119±63 QSU (dry). These patterns reflected enhanced terrestrial inputs driven by monsoon runoff and soil leaching, resulting in more aromatic, higher-molecular-weight DOM. Along the river continuum, upstream waters were dominated by humic, terrestrially derived material (higher values of DOC, a(350), C1, C3). In contrast, the Red River Delta exhibited lower DOM concentrations and greater material processing, consistent with dilution and in-river processing. The higher relative contribution of tryptophan-like compounds (higher %C2, C2/C1, and C2/C3 ratios) in the delta during the dry period may reflect enhanced biological activity and/or possible anthropogenic inputs. These findings highlight the combined influence of monsoon hydrology, in-stream processes, and human pressures on DOM dynamics in a major Southeast Asian river.

Downloads

Download data is not yet available.

References

Andrew A.A., Del Vecchio R., Subramaniam A., Blough N.V., 2013. Chromophoric dissolved organic matter (CDOM) in the Equatorial Atlantic Ocean: Optical properties and their relation to CDOM structure and source. Marine Chemistry, 148, 33–43. https://doi.org/10.1016/j.marchem.2012.11.001.

Bricaud A., Morel A., Prieur L., 1981. Absorption by dissolved organic matter of the sea (yellow substance) in the UV and visible domains. Limnology and Oceanography, 26(1), 43–53. https://doi.org/10.4319/lo.1981.26.1.0043.

Carstea E.M., Bridgeman J., Baker A., Reynolds D.M., 2016. Fluorescence spectroscopy for wastewater monitoring: A review. Water Research, 95, 205–219. https://doi.org/10.1016/j.watres.2016.03.021.

Coble, P.G., 1996. Characterization of marine and terrestrial DOM in seawater using excitation-emission matrix spectroscopy. Marine Chemistry, 51(4), 325–346. https://doi.org/10.1016/0304-4203(95)00062-3.

Coble P.G., 2007. Marine Optical Biogeochemistry: The Chemistry of Ocean Color. Chemical Reviews 107(2), 402–418. https://doi.org/10.1021/cr050350+.

Coble P.G., Lead J., Baker A. (Eds.), 2014. Aquatic organic matter fluorescence. Cambridge University Press. Aquatic organic matter fluorescence. Cambridge Environmental Chemistry Series, Cambridge University Press, New York, NY, USA, 75–122.

Cory R.M., McKnight D.M., 2005. Fluorescence spectroscopy reveals ubiquitous presence of oxidized and reduced quinones in dissolved organic matter. Environmental Science and Technology, 39(21), 8142–8149. https://doi.org/10.1021/es0506962.

D'Andrilli J., Silverman V., Buckley S., Rosario-Ortiz F.L., 2022. Inferring ecosystem function from dissolved organic matter optical properties: a critical review. Environmental Science and Technology, 56(16), 11146–11161. https://doi.org/10.1021/acs.est.2c04240.

De Haan H., De Boer T., 1987. Applicability of light absorbance and fluorescence as measures of concentration and molecular size of dissolved organic carbon in humic Lake Tjeukemeer. Water research, 21(6), 731–734. https://doi.org/10.1016/0043-1354(87)90086-8.

Dittmar T., Lennartz S.T., Buck-Wiese H., Hansell D.A., Santinelli C., Vanni C., Blasius B., Hehemann J.-H., 2021. Enigmatic persistence of dissolved organic matter in the ocean. Nature Reviews Earth and Environment, 2, 570–583. https://doi.org/10.1038/s43017-021-00183-7.

Dittmar T., Stubbins A., 2014. Dissolved organic matter in aquatic systems, In: H.D. Holland, K.K. Turekian (Eds.), Treatise on Geochemistry, Second edition. Elsevier Science, 2, 125–156. http://dx.doi.org/10.1016/B978-0-08-095975-7.01010-X.

Duursma E.K., 1974. The fluorescence of dissolved organic matter in the sea, In: N.G. Jerlov, E. Steemann Nielsen (Eds.), Optical Aspects of Oceanography. Academic Press, New York, 237–256.

Fabre C., Wei X., Sauvage S., Le T.P.Q., Ouillon S., Orange D., Herrmann M., Sánchez-Pérez J.-M., 2023. Assessing fluvial organic carbon flux and its response to short climate variability and damming on a large-scale tropical Asian river basin. Science of The Total Environment, 903, 166589. https://doi.org/10.1016/j.scitotenv.2023.166589.

Fellman J.B., Hood E., Spencer R.G.M., 2010. Fluorescence spectroscopy opens new windows into dissolved organic matter dynamics in freshwater ecosystems: A review. Limnology and Oceanography, 55(6), 2452–2462. https://doi.org/10.4319/lo.2010.55.6.2452.

Ferretto N., Tedetti M., Guigue C., Mounier S., Raimbault P., Goutx M., 2017. Spatio-temporal variability of fluorescent dissolved organic matter in the Rhône River delta and the Fos-Marseille marine area (France, NW Mediterranean Sea). Environmental Science and Pollution Research, 24(5), 4973–4989. https://doi.org/10.1007/s11356-016-8255-z.

Fourrier P., Dulaquais G., Guigue C., Giamarchi P., Sarthou G., Whitby H., Riso R., 2022. Characterization of the vertical size distribution, composition and chemical properties of dissolved organic matter in the (ultra)oligotrophic Pacific Ocean through a multi-detection approach. Marine Chemistry, 240, 104068. https://doi.org/10.1016/j.marchem.2021.104068.

Han Z., Xiao M., Yue F., Yi Y., Mostofa K.M.G., 2021. Seasonal Variations of Dissolved Organic Matter by Fluorescent Analysis in a Typical River Catchment in Northern China. Water, 13, 494. https://doi.org/10.3390/w13040494.

Hansen A.M., Kraus T.E.C., Pellerin B.A., Fleck J.A., Downing B.D., Bergamaschi B.A., 2016. Optical properties of dissolved organic matter (DOM): Effects of biological and photolytic degradation. Limnology and Oceanography, 61(3), 1015–1032. https://doi.org/10.1002/lno.10270.

Helms J.R., Stubbins A., Ritchie J.D., Minor E.C., Kieber D.J., Mopper K., 2008. Absorption spectral slopes and slope ratios as indicators of molecular weight, source and photobleaching of chromophoric dissolved organic matter. Limnology and Oceanography, 53(3), 955–969. https://doi.org/10.4319/lo.2008.53.3.0955.

Hosen J.D., Aho K.S., Fair J.H., Kyzivat E.D., Matt S., Morrison J., Stubbins A., Weber L.C., Yoon B., Raymond P.A., 2021. Source Switching Maintains Dissolved Organic Matter Chemostasis Across Discharge Levels in a Large Temperate River Network. Ecosystems, 24(2), 227–247. https://doi.org/10.1007/s10021-020-00514-7.

Hosen J.D., McDonough O.T., Febria C.M., Palmer M.A., 2014. Dissolved organic matter quality and bioavailability changes across an urbanization gradient in headwater streams. Environmental Science and Technology, 48(14), 7817–7824. https://doi.org/10.1021/es501422z.

Hudson N., Baker A., Reynolds D., 2007. Fluorescence analysis of dissolved organic matter in natural, waste and polluted waters a review. River Res. Applic., 23(6), 631–649. https://doi.org/10.1002/rra.1005.

Huguet A., Vacher L., Relexans S., Saubusse S., Froidefond J.M., Parlanti E., 2009. Properties of fluorescent dissolved organic matter in the Gironde Estuary. Organic Geochemistry, 40(6), 706–719. https://doi.org/10.1016/j.orggeochem.2009.03.002.

Huong P.T.T., Everaarts A.P., Neeteson J.J., Struik P.C., 2013. Vegetable production in the Red River Delta of Vietnam. II. Profitability, labour requirement and pesticide use. NJAS - Wageningen Journal of Life Sciences 67, 37–46. https://doi.org/10.1016/j.njas.2013.09.003.

Ishii S.K.L., Boyer T.H., 2012. Behavior of Reoccurring PARAFAC Components in Fluorescent Dissolved Organic Matter in Natural and Engineered Systems: A Critical Review. Environmental Science and Technology, 46(6), 2006–2017. https://doi.org/10.1021/es2043504.

Jaffé R., Ding Y., Niggemann J., Vähätalo A.V., Stubbins A., Spencer R.G., Campbell J., Dittmar T., 2013. Global charcoal mobilization from soils via dissolution and riverine transport to the oceans. Science, 340(6130), 345–347. https://doi.org/10.1126/science.1231476.

Jaffé R., Cawley K.M., Yamashita Y., 2014. Applications of excitation emission matrix fluorescence with parallel factor Analysis (EEM-PARAFAC) in assessing environmental dynamics of natural dissolved organic matter (DOM) in aquatic environments: a review, In: Advances in the Physicochemical Characterization of Dissolved Organic Matter: Impact on Natural and Engineered Systems. American Chemical Society, 27–73. https://doi.org/10.1021/bk-2014-1160.ch003.

Kang W., Hu X., Feng R., Wei C., Yu F., 2023. DOM associates with greenhouse gas emissions in Chinese rivers under diverse land uses. Environmental Science and Technology, 57(40), 15004–15013. https://doi.org/10.1021/acs.est.3c03826.

Kellerman A.M., Guillemette F., Podgorski D.C., Aiken G.R., Butler K.D., Spencer R.G.M., 2018. Unifying Concepts Linking Dissolved Organic Matter Composition to Persistence in Aquatic Ecosystems. Environmental Science and Technology, 52(5), 2538–2548. https://doi.org/10.1021/acs.est.7b05513.

Korak J.A., McKay G., 2024. Critical review of fluorescence and absorbance measurements as surrogates for the molecular weight and aromaticity of dissolved organic matter. Environmental Science: Processes & Impacts, 26(10), 1663–1702. https://doi.org/10.1039/d4em00183d.

Kamjunke N., Herzsprung P., von Tümpling W., Matoušů A., Znachor P., Sanders T., Brix H., Bussmann I., Weitere M., Lechtenfeld O.J., 2026. Longitudinal dynamics and transformation of riverine dissolved organic matter from source to sea. Water Research, 288, 124613. https://doi.org/10.1016/j.watres.2025.124613.

Laane R.W.P.M., Koole L., 1982. The relation between fluorescence and dissolved organic carbon in the Ems-Dollart estuary and the Western Wadden Sea. Netherlands Journal of Sea Research, 15(2), 217–227. https://doi.org/10.1016/0077-7579(82)90005-9.

Lambert T., Teodoru C.R., Nyoni F.C., Bouillon S., Darchambeau F., Massicotte P., Borges A.V., 2016. Along-stream transport and transformation of dissolved organic matter in a large tropical river. Biogeosciences, 13(9), 2727–2741. https://doi.org/10.5194/bg-13-2727-2016.

Le N.D., Le T.P.Q., Phung T.X.B., Duong T.T., Didier O., 2020. Impact of hydropower dam on total suspended sediment and total organic nitrogen fluxes of the Red River (Vietnam). Proceedings of the International Association of Hydrological Sciences, 383, 367–374. https://doi.org/10.5194/piahs-383-367-2020.

Le T.P.Q., Billen G., Garnier J., Chau V.M., 2015. Long-term biogeochemical functioning of the Red River (Vietnam): past and present situations. Regional Environmental Change, 15(2), 329–339. https://doi.org/10.1007/s10113-014-0646-4.

Le T.P.Q., Dao V.N., Rochelle-Newall E., Garnier J., Lu X., Billen G., Duong T.T., Ho C.T., Etcheber H., Nguyen T.M.H., Nguyen T.B.N., Nguyen B.T., Da Le N., Pham Q.L., 2017. Total organic carbon fluxes of the Red River system (Vietnam): TOC fluxes of the Red River. Earth Surface Processes and Landforms 42(9), 1329–1341. https://doi.org/10.1002/esp.4107.

Le T.P.Q., Garnier J., Gilles B., Sylvain T., Van Minh C., 2007. The changing flow regime and sediment load of the Red River, Viet Nam. Journal of Hydrology, 334(1–2), 199–214. https://doi.org/10.1016/j.jhydrol.2006.10.020.

Shin-Ah L., Kim G., 2018. Sources, fluxes, and behaviors of fluorescent dissolved organic matter (FDOM) in the Nakdong River Estuary, Korea. Biogeosciences, 15(4), 1115–1122. https://doi.org/10.5194/bg-15-1115-2018.

Lee M.-H., Osburn C.L., Shin K.-H., Hur J., 2018. New insight into the applicability of spectroscopic indices for dissolved organic matter (DOM) source discrimination in aquatic systems affected by biogeochemical processes. Water Research, 147, 164–176. https://doi.org/10.1016/j.watres.2018.09.048.

Leenheer J.A., Croué J.P., 2003. Characterizing aquatic dissolved organic matter. Environmental Science and Technology, 37(1), 18A–26A. https://doi.org/10.1021/es032333c.

Li P., Hur J., 2017. Utilization of UV-Vis spectroscopy and related data analyses for dissolved organic matter (DOM) studies: A review. Critical Reviews in Environmental Science and Technology, 47(3), 131–154. https://doi.org/10.1080/10643389.2017.1309186.

Lin H., Guo L., 2020. Variations in colloidal DOM composition with molecular weight within individual water samples as characterized by flow field-flow fractionation and EEM-PARAFAC analysis. Environmental Science & Technology, 54(3), 1657–1667. https://doi.org/10.1021/acs.est.9b07123.

Luu T.N.M., Garnier J., Billen G., Le T.P.Q., Némery J., Orange D., Le L.A., 2012. N, P, Si budgets for the Red River Delta (Northern Vietnam): How the delta affects river nutrient deliveries to the sea. Biogeochemistry, 107(1), 241–259. https://doi.org/10.1007/s10533-010-9549-8.

Martinot P.L, Guigue C., Bui V.H., Gourdon L., Mari X., Canh N.T., Dang V.Q.D., Duong T.Q.M., Tedetti M., Vu C.T., 2025. Seasonal and spatial variability of dissolved black carbon in the Red River delta (North Vietnam). Biogeochemistry 168(6), 85. https://doi.org/10.1007/s10533-025-01278-9.

Massicotte P., Asmala E., Stedmon C., Markager S., 2017. Global distribution of dissolved organic matter along the aquatic continuum: Across rivers, lakes and oceans. Science of The Total Environment, 609, 180–191. https://doi.org/10.1016/j.scitotenv.2017.07.076.

McKnight D.M., Boyer E.W., Westerhoff P.K., Doran P.T., Kulbe T., Andersen D.T., 2001. Spectrofluorometric characterization of dissolved organic matter for indication of precursor organic material and aromaticity. Limnology and Oceanography, 46(1), 38–48. https://doi.org/10.4319/lo.2001.46.1.0038.

Mielnik L., Kowalczuk P., 2018. Optical characteristic of humic acids from lake sediments by excitation-emission matrix fluorescence with PARAFAC model. Journal of Soils and Sediments, 18(8), 2851–2862. https://doi.org/10.1007/s11368-018-1947-x.

Murphy K.R., Stedmon C.A., Waite T.D., Ruiz G.M., 2008. Distinguishing between terrestrial and autochthonous organic matter sources in marine environments using fluorescence spectroscopy. Marine Chemistry, 108(1–2), 40–58. https://doi.org/10.1016/j.marchem.2007.10.003.

Murphy K.R., Stedmon C.A., Wenig P., Bro R., 2014. OpenFluor an online spectral library of auto-fluorescence by organic compounds in the environment. Analytical methods, 6(3), 658–661. https://doi.org/10.1039/c3ay41935e.

Nelson N.B., Siegel D.A., 2013. The global distribution and dynamics of chromophoric dissolved organic matter. Annual review of marine science, 5(1), 447–476. https://doi.org/10.1146/annurev-marine-120710-100751.

Nelson N.B., Siegel D.A., Carlson C.A., Swan C., Smethie Jr W.M., Khatiwala S., 2007. Hydrography of chromophoric dissolved organic matter in the North Atlantic. Deep Sea Research Part I: Oceanographic Research Papers, 54(5), 710–731. https://doi.org/10.1016/j.dsr.2007.02.006.

Niloy N.M., Shammi M., Haque M.M., Tareq S.M., 2022. Investigating dissolved organic matter dynamics in the downstream reaches of the Ganges and Brahmaputra Rivers using fluorescence spectroscopy. Frontiers in Earth Science, 10, 821050. https://doi.org/10.3389/feart.2022.821050.

Nguyen H.D., Dang D.K., Lai T.A.T., Tran D.D., Shahabi H., Bui Q.T., 2025. Predicting Soil Salinity in the Red River Delta (Vietnam) Using Machine Learning and Assessing Farmers' Adaptive Capacity. Natural Hazards and Earth System Sciences, 25(9), 3505–3524. https://doi.org/10.5194/nhess-25-3505-2025.

Nguyen H.Q., Tran Q.V., 2023. Long-term analysis of sediment load changes in the Red River system (Vietnam) due to dam-reservoirs. Journal of Hydro-environment Research, 51, 48–66. https://doi.org/10.1016/j.jher.2023.10.002.

Nguyen T.M.H., Le T.P.Q., Hoang V.V., Vu C.T., 2022. Biodegradable and Seasonal Variation of Organic Carbon Affected by Anthropogenic Activity: A Case in Xuan Thuy Mangrove Forest, North Vietnam. Water, 14(5), 773. https://doi.org/10.3390/w14050773.

Nguyen T.M.H., Le T.P.Q., Van Hoang V., Nhu D.L., Vu C.T., Thi Thuy D., 2021. Seasonal and spatial variation in biodegradability of organic carbon along the Red River, Vietnam. Carbon Management, 12(5), 549–557. https://doi.org/10.1080/17583004.2021.1980110.

Obrador B., von Schiller D., Marcé R., Gómez-Gener L., Koschorreck M., Borrego C., Catalán N., 2018. Dry habitats sustain high CO2 emissions from temporary ponds across seasons. Scientific Reports, 8(1), 3015. https://doi.org/10.1038/s41598-018-20969-y.

Ohno T., 2002. Fluorescence inner-filtering correction for determining the humification index of dissolved organic matter. Environmental Science and Technology, 36(4), 742–746. https://doi.org/10.1021/es0155276.

Osburn C.L., Handsel L.T., Peierls B.L., Paerl H.W., 2016. Predicting sources of dissolved organic nitrogen to an estuary from an agro-urban coastal watershed. Environmental Science and Technology, 50(16), 8473–8484. https://doi.org/10.1021/acs.est.6b00053.

Para J., Coble P.G., Charrìère B., Tedetti M., Fontana C., Sempere R., 2010. Fluorescence and absorption properties of chromophoric dissolved organic matter (CDOM) in coastal surface waters of the northwestern Mediterranean Sea, influence of the Rhône River. Biogeosciences, 7(12), 4083–4103. https://doi.org/10.5194/bg-7-4083-2010.

Parr T.B., Cronan C.S., Ohno T., Findlay S.E.G., Smith S.M.C., Simon K.S., 2015. Urbanization changes the composition and bioavailability of dissolved organic matter in headwater streams. Limnology and Oceanography, 60(3), 885–900. https://doi.org/10.1002/lno.10060.

Park J.H., Jin H., Yoon T.K., Begum M.S., Eliyan C., Lee E.-J., Lee S.-C., Oh N.-H., 2021. Wastewater-boosted biodegradation amplifying seasonal variations of pCO2 in the Mekong-Tonle Sap river system. Biogeochemistry, 155(2), 219–235. https://doi.org/10.1007/s10533-021-00823-6.

Parlanti E., Worz K., Geoffroy L., Lamotte M., 2000. Dissolved organic matter fluorescence spectroscopy as a tool to estimate biological activity in a coastal zone submitted to anthropogenic inputs. Organic Geochemistry, 31(12), 1765–1781. https://doi.org/10.1016/S0146-6380(00)00124-8.

Peuravuori J., Pihlaja K., 1997. Molecular size distribution and spectroscopic properties of aquatic humic substances. Analytica Chimica Acta, 337(2), 133–149. https://doi.org/10.1016/S0003-2670(96)00412-6.

Piton V., Ouillon S., Vinh V.D., Many G., Herrmann M., Marsaleix P., 2020. Seasonal and tidal variability of the hydrology and suspended particulate matter in the Van Uc estuary, Red River, Vietnam. Journal of Marine Systems, 211, 103403. https://doi.org/10.1016/j.jmarsys.2020.103403.

Redfern S.K., Azzu N., Binamira J.S., 2012. Rice in Southeast Asia: facing risks and vulnerabilities to respond to climate change. Build Resilience Adapt Climate Change Agri Sector. Proceedings of a Joint FAO/OECD Workshop 23–24 April 2012, 23(295), 1–14. http://www.fao.org/docrep/017/i3084e/i3084e18.pdf.

Brogi S.R., Balestra C., Casotti R., Cossarini G., Galletti Y., Gonnelli M., Vestri S., Santinelli C., 2020. Time resolved data unveils the complex DOM dynamics in a Mediterranean river. Science of the Total Environment, 733, 139212. https://doi.org/10.1016/j.scitotenv.2020.139212.

Roebuck Jr J.A., Seidel M., Dittmar T., Jaffé R., 2020. Controls of Land Use and the River Continuum Concept on Dissolved Organic Matter Composition in an Anthropogenically Disturbed Subtropical Watershed. Environmental Science and Technology, 54(1), 195–206. https://doi.org/10.1021/acs.est.9b04605.

Shi Y., Zhang L., Li Y., Zhou L., Zhou Y., Zhang Y., Huang C., Li H., Zhu G., 2020. Influence of land use and rainfall on the optical properties of dissolved organic matter in a key drinking water reservoir in China. Science of the Total Environment, 699, 134301. https://doi.org/10.1016/j.scitotenv.2019.13430.

Shin Y., Lee E.-J., Jeon Y.-J., Hur J., Oh N.-H., 2016. Hydrological changes of DOM composition and biodegradability of rivers in temperate monsoon climates. Journal of Hydrology, 540, 538–548. https://doi.org/10.1016/j.jhydrol.2016.06.004.

Sohrin R., Sempéré R., 2005. Seasonal variation in total organic carbon in the northeast Atlantic in 2000–2001. Journal of Geophysical Research: Oceans, 110(C10). https://doi.org/10.1029/2004JC002731.

Spencer R.G., Aiken G.R., Wickland K.P., Striegl R. G., Hernes P.J., 2008. Seasonal and spatial variability in dissolved organic matter quantity and composition from the Yukon River basin, Alaska. Global Biogeochemical Cycles, 22(4). https://doi.org/10.1029/2008GB003231.

Spencer R.G., Butler K.D., Aiken G.R., 2012. Dissolved organic carbon and chromophoric dissolved organic matter properties of rivers in the USA. Journal of Geophysical Research: Biogeosciences, 117(G3). https://doi.org/10.1029/2011JG001928.

Stedmon C.A., Bro R., 2008. Characterizing dissolved organic matter fluorescence with parallel factor analysis: a tutorial. Limnology and Oceanography: Methods, 6(11), 572–579. https://doi.org/10.4319/lom.2008.6.572.

Stedmon C.A., Cory R.M., 2014. Biological origins and fate of fluorescent dissolved organic matter in aquatic environments, In: P.G. Coble, J. Lead, A. Baker, D.M. Reynolds, R.G.M. Spencer (Eds.), Aquatic organic matter fluorescence. Cambridge Environmental Chemistry Series, Cambridge University Press, New York, NY, USA, 278–299.

Stedmon C.A., Markager S., 2005. Resolving the variability of dissolved organic matter fluorescence in a temperate estuary and its catchment using PARAFAC analysis. Limnology and Oceanography, 50(2), 686–697. https://doi.org/10.4319/lo.2005.50.2.0686.

Stedmon C.A., Markager S., Bro R., 2003. Tracing dissolved organic matter in aquatic environments using a new approach to fluorescence spectroscopy. Marine Chemistry, 82(3–4), 239–254. https://doi.org/10.1016/S0304-4203(03)00072-0.

Tedetti M., Guigue C., Mahieu L., Martinot P.L., Benavides M., Dupouy C., Nunige S., Pulido-Villena E., Dimier C., Tilliette C., Bonnet S., Guieu C., Lefèvre D., 2026. Dissolved organic matter (DOC, CDOM, FDOM) in the Western Tropical South Pacific: Depth- and subregion-resolved variability, and hydrothermal influence. Progress in Oceanography, 242, 103664. https://doi.org/10.1016/j.pocean.2025.103664.

Tedetti M., Longhitano R., Garcia N., Guigue C., Ferretto N., Goutx M., 2012. Fluorescence properties of dissolved organic matter in coastal Mediterranean waters influenced by a municipal sewage effluent (Bay of Marseilles, France). Environmental Chemistry, 9(5), 438–449. https://doi.org/10.1071/EN12081.

Twardowski M.S., Boss E., Sullivan J.M., Donaghay P.L., 2004. Modeling the spectral shape of absorption by chromophoric dissolved organic matter. Marine Chemistry, 89(1–4), 69–88. https://doi.org/10.1016/j.marchem.2004.02.008.

Vinh V.D., Ouillon S., Thanh T.D., Chu L., 2014. Impact of the Hoa Binh dam (Vietnam) on water and sediment budgets in the Red River basin and delta. Hydrology and Earth System Sciences, 18(10), 3987–4005. https://doi.org/10.5194/hess-18-3987-2014.

Vu C.T., Chu D.B., Mai H., Herrmann M., Bui V.H., Le P.T., Chu N.H.A., Tedetti M., Behra P., 2023. First hydrological study on the seasonal occurrence of glyphosate, glufosinate, and their metabolites in the Red River system, North Vietnam. Environmental Nanotechnology, Monitoring and Management, 20, 100833. https://doi.org/10.1016/j.enmm.2023.100833.

Wei X., Sauvage S., Le T.P.Q., Ouillon S., Orange D., Vinh V.D., Sanchez-Perez J.-M., 2019. A Modeling Approach to Diagnose the Impacts of Global Changes on Discharge and Suspended Sediment Concentration within the Red River Basin. Water, 11(5), 958. https://doi.org/10.3390/w11050958.

Weishaar J.L., Aiken G.R., Bergamaschi B.A., Fram M.S., Fujii R., Mopper K., 2003. Evaluation of specific ultraviolet absorbance as an indicator of the chemical composition and reactivity of dissolved organic carbon. Environmental Science and Technology, 37(20), 4702–4708. https://doi.org/10.1021/es030360x.

Wilson H., Xenopoulos M., 2009. Effects of agricultural land use on the composition of fluvial dissolved organic matter. Nature Geoscience, 2(1), 37–41. https://doi.org/10.1038/ngeo391.

Xue L.I., Yungang L.I., Jiaonan H.E., Xian L.U.O., 2016. Analysis of variation in runoff and impacts factors in the Yuanjiang-Red River Basin from 1956 to 2013. Resources Science, 38(6), 1149–1159. https://doi.org/10.18402/resci.2016.06.14.

Yamashita Y., Maie N., Briceño H., Jaffé R., 2010. Optical characterization of dissolved organic matter in tropical rivers of the Guayana Shield, Venezuela. Journal of Geophysical Research: Biogeosciences, 115(G1). https://doi.org/10.1029/2009JG000987.

Yamashita Y., Nosaka Y., Suzuki K., Ogawa H., Takahashi K., Saito H., 2013. Photobleaching as a factor controlling spectral characteristics of chromophoric dissolved organic matter in open ocean. Biogeosciences, 10(11), 7207–7217. https://doi.org/10.5194/bg-10-7207-2013.

Yan P., Wei S., Chen Y., Ning Q., Hu Z., Guo Z., Xie H., Wu H., Zhang J., 2023. Fluorescence spectroscopic characterization of dissolved organic matter in the wastewater treatment plant and hybrid constructed wetlands coupling system in winter: A case study in eastern China. Environmental Technology and Innovation, 32, 103399. https://doi.org/10.1016/j.eti.2023.103399.

Yuen K.W., Hanh T.T., Quynh V.D., Switzer A.D., Teng P., Lee J.S.H., 2021. Interacting effects of land-use change and natural hazards on rice agriculture in the Mekong and Red River deltas in Vietnam. Natural Hazards and Earth System Sciences, 21(5), 1473–1493. https://doi.org/10.5194/nhess-21-1473-2021.

Zhang H., Zheng Y., Wang X.C., Wang Y., Dzakpasu M., 2021. Characterization and biogeochemical implications of dissolved organic matter in aquatic environments. Journal of Environmental Management, 294, 113041. https://doi.org/10.1016/j.jenvman.2021.113041.

Zhang D., Meng F., Wang Y., Zhang L., Xue H., Liang Z., Zhang J., 2023. Seasonal and Spatial Variations in the Optical Characteristics of Dissolved Organic Matter in the Huma River Basin, China. Water, 15(8), 1579. https://doi.org/10.3390/w15081579.

Zheng S., Feng F., Liu D., Qian F., Xie X., Yu H., Song Y, 2026. Hydrological Seasonality Drives DOM-Bacteria Interactions in the Rushan River Basin. Microorganisms, 14(1), 110. https://doi.org/10.3390/microorganisms14010110.

Zhuang W.E., Chen W., Cheng Q., Yang L., 2021. Assessing the priming effect of dissolved organic matter from typical sources using fluorescence EEMs-PARAFAC. Chemosphere 264, 128600. https://doi.org/10.1016/j.chemosphere.2020.128600.