The Optical Characterization and Distribution of Dissolved Organic Matter in Water Regimes of Qilian Mountains Watershed

The constituents and content of dissolved organic matter (DOM) in the Qilian Mountain watershed were characterized with a spectroscopic technique, especially 3-DEEM fluorescence assisted by parallel factor (PARAFAC) analysis. The level of DOM in the surrounding area of Qinghai lake (thereafter the lake in this article specifically refers to Qinghai Lake)was highest at 9.45 mg C·L−1 and about 3 times less (3.09 mg C·L−1) in a cropland aquatic regime (the lowest value). In general, DOM was freshly autochthonously generated by plankton and plant debris, microorganisms and diagenetic effects in the aquatic environment (FI > 1.8). Component 1 (humic acid-like) and 3 (fulvic acid-like) determined the humification degree of chromophoric dissolved organic matter (CDOM). The spatial variation of sulfate and nitrate in the surrounding water regime of the lake revealed that organic molecules were mainly influenced by bacterial mediation. Mineral disintegration was an important and necessary process for fluorescent fraction formation in the cropland water regime. Exceptionally, organic moiety in the unused land area was affected by anespecially aridclimate in addition to microbial metabolic experience. Salinity became the critical factor determining the distribution of DOM, and the total normalized fluorescent intensity and CDOM level were lower in low-salinity circumstances (0.2–0.5 g·L−1) with 32.06 QSU and 1.38 m−1 in the grassland area, and higher salinity (0.6~0.8 g·L−1) resulted in abnormally high fluorescence of 150.62 QSU and absorption of 7.83 m−1 in the cropland water regime. Climatic conditions and microbial reactivity controlled by salinity were found to induce the above results. Our findings demonstrated that autochthonous inputs regulated DOM dynamics in the Qilian Mountains watershed of high altitude.

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Temporal and Spatial Distribution and Fluorescence Spectra of Dissolved Organic Matter in Plateau Lakes: A Case Study of Qinghai Lake

Water ◽

10.3390/w13243481 ◽

2021 ◽

Vol 13 (24) ◽

pp. 3481

Author(s):

Zheng Li ◽

Zhenghui Fu ◽

Yang Zhang ◽

Yunyan Guo ◽

Feifei Che ◽

...

Keyword(s):

Organic Matter ◽

Spatial Distribution ◽

Dissolved Organic Matter ◽

Fluorescence Intensity ◽

Rapid Development ◽

Water Environment ◽

Anthropogenic Sources ◽

Qinghai Lake ◽

Total Fluorescence ◽

Temporal And Spatial

Dissolved organic matter (DOM) has a great impact on the main pollution indicators of lakes (such as chemical oxygen demand, COD). Therefore, DOM is the research basis for understanding the meaning of the water environment and the laws of the migration and transformation of pollutants. Qinghai Lake is one of the world’s typical inland plateau lake wetlands. It plays important roles in improving and regulating the climate and in promoting a virtuous regional ecological cycle. In recent years, with the acceleration of urbanization and the rapid development of tourism, under the background of climate change, and with grassland degradation and precipitation change, the whole basin of Qinghai Lake has been facing great ecological pressure. In order to comprehensively explore the water environment of Qinghai Lake and to protect the sustainable development of the basin, a systematic study was carried out on the whole basin of Qinghai Lake. The results show the following: (1) from 2010 to 2020, the annual average value of CODCr in Qinghai Lake fluctuated in the range from class III to class V according to the surface water environmental quality standard, showing first a downward trend and then an upward trend. (2) The concentration of CDOM in Qinghai Lake had obvious temporal and spatial changes. (3) The spatial distribution of the total fluorescence intensity of FDOM in water was also different in different seasons. However, in the three surveys, the area with the highest total fluorescence intensity of FDOM in the water body appeared near Erlangjian in the south of Qinghai Province, indicating that anthropogenic sources are the main controlling factors of dissolved organic matter in the lake.

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Dynamics of dissolved organic matter in a wastewater effluent-impacted Japanese urban stream: characteristics, occurrence and photoreactivity of fluorescent components

Water Science & Technology ◽

10.2166/wst.2018.468 ◽

2018 ◽

Vol 78 (10) ◽

pp. 2036-2045

Author(s):

Kenshi Sankoda ◽

Chieko Yamamoto ◽

Kazuhiko Sekiguchi ◽

Jun Kobayashi ◽

Qingyue Wang

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Treatment Plant ◽

Urban Stream ◽

Aquatic Environments ◽

Fluorescent Intensity ◽

Parafac Model ◽

Wwtp Effluent ◽

Release Area ◽

Parallel Factor

Abstract We report the results of using the excitation–emission matrix (EEM) method combined with parallel factor analysis (PARAFAC) to investigate the characteristics and occurrence of dissolved organic matter (DOM) in an urban stream impacted by effluent from a wastewater treatment plant (WWTP). The PARAFAC model divides the bulk EEM spectra into six individual fluorescent components with three humic-like components (C1–C3), two protein-like components (C4 and C5) and a wastewater-derived component (C6). In general, intensities of fluorescent components are abundant in WWTP effluent impacted samples, thus showing that such an effluent is a major source of DOM in urban rivers, but C5 is considered to have autochthonous sources within the stream. In areas where the effluent is released, the fluorescent intensity from components (except C5) gradually decreases as these components are transported downstream. However, concentrations of dissolved organic carbon remain almost constant downstream of the release area. These results would be attributed to degradation and/or modification of fluorophore. Photolysis experiments confirmed that fluorescent intensities can decrease with increase of irradiation times. C6 particularly showed a rapid photodegradation, remaining only 24.1% after 48 h photolysis. These findings would be important when assessing DOM source and water quality in aquatic environments by EEM-PARAFAC.

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Correlation between Fluorescent and UV Absorbance in Dissolved Organic Matter of the Effluent from the Pulp Mill

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.726-731.1463 ◽

2013 ◽

Vol 726-731 ◽

pp. 1463-1467

Author(s):

Shao Wei Liao ◽

Jing Wen Cao ◽

Chung Yi Chung ◽

Hwa Sheng Gau ◽

Chang Gai Lee ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Water Samples ◽

Membrane Filter ◽

Pulp Mill ◽

Secondary Treatment ◽

Uv Absorbance ◽

Fluorescent Intensity ◽

Parafac Model ◽

Explained Variation

During the interval from Oct.2011to April.2012, water samples were collected from the effluent treated by the secondary treatment of pulp mill. The measurements of EEFM (Excitation Emission Fluorescent matrix) by the fluorescent spectrometry as well as the value of UV absorbance were analyzed for water samples filtered by 0.45μm membrane filter. The EEFM information of dissolved organic matter of filtered water samples were characterized as 8 components with 89.7% of explained variation using PARAFAC model. Four substances had high loading, including the wavelength of Excitation /Emission (Ex/Em) of 360/420 nm, 280/270-430 nm, 350/430 nm and 300/420-480 nm. The fluorescent characteristic of 270/310 nm and 270/450 nm had a high correlation with UV254 value (R=0.838); however, the fluorescent intensity of 240/410 nm had a negative correlation with the value of UV200-400.

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Contrasting the Optical Characterization of Dissolved Organic Matter in Water and Sediment from a Nascent River-Type Lake (Chongqing, China)

Water ◽

10.3390/w13010070 ◽

2020 ◽

Vol 13 (1) ◽

pp. 70

Author(s):

Fengxia Niu ◽

Fangying Ji ◽

Qian Zhang ◽

Qiushi Shen

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

High Sensitivity ◽

Optical Characterization ◽

Pore Waters ◽

Overlying Water ◽

Fluorescent Intensity ◽

Water And Sediment ◽

Doc Flux

Carbon cycling in rivers is altered by the creation of impoundments through dam construction. This paper seeks to identify the source and composition of dissolved organic matter (DOM) in both water and sediment in Lake Longjing by contrasting the optical characterization of DOM. By comparing the dissolved organic carbon (DOC) concentrations, we show that the sediment (53.7 ± 16.6 mg/L) acts as a DOC source to the overlying water (23.1 ± 1.4 mg/L). The estimated DOC flux in the original reservoir region (88.3 mg m−2 d−1) is higher than that in the newly submerged region (26 mg m−2 d−1), whereas the latter has larger contribution to the DOC annual load because of its larger sediment area. Spectroscopic analysis suggested that pore waters had higher aromaticity and lower proportion of fresh DOM than those in surface waters and benthic overlying waters. Through Parallel Factor Analysis, four fluorescent components were identified, i.e., two terrestrial humic-like components, one protein-like, and one microbial humic-like. Spearman correlation and Non-Metric-Multidimensional Scaling (NMDS) analysis manifested that fluorescent DOM in surface sediments is mainly contributed by autochthonous source, the others by allochthonous source. Due to the high sensitivity of the fluorescent intensity of the protein-like component, it is a useful indicator to reveal the changes of source of DOM.

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Temporal and Spatial Distribution and Fluorescence Spectra of Dissolved Organic Matter in Plateau Lakes -- A Case Study of Qinghai Lake

10.21203/rs.3.rs-1084038/v1 ◽

2021 ◽

Author(s):

Zheng Li ◽

Zhenghui Fu ◽

Yang Zhang ◽

Yunyan Guo ◽

Feifei Che ◽

...

Keyword(s):

Organic Matter ◽

Spatial Distribution ◽

Dissolved Organic Matter ◽

Lake Water ◽

Water Body ◽

Mean Value ◽

Qinghai Lake ◽

Temporal And Spatial Distribution ◽

The Mean ◽

Temporal And Spatial

Abstract Dissolved organic matter (DOM) has a great influence on the main pollution indexes of lakes (such as COD). Therefore, DOM research is the basis for understanding the water environmental quality and the law of pollutant migration and transformation in the basin. In this study, the water quality monitoring data of Qinghai Lake water body and 8 rivers around the lake from 2010 to 2020 were collected, and the dissolved organic matter (DOM) was synchronously sampled in May, September and October 2020. The optical characteristics of DOM, the temporal and spatial distribution of CDOM and the fluorescence spectrum and fluorescence component characteristics of FDOM were analyzed and studied. The results show that: (1) From 2010 to 2020, the annual mean value of CODCr of Qinghai Lake water body fluctuates in the range of Class III to Class V according to the environmental quality standard of the surface water, and shows a downward trend first and then an upward one. In general, the mean value of CODCr concentration in Qinghai Lake water body is at a high level and varies slightly among different months. (2) The mean value of CODCr concentration of the eight main rivers entering Qinghai Lake from 2010 to 2020 can be sorted from lowest to highest as follows: Ganzi River, Buha River, Jilmeng River, Hargai River, Shaliu River, Quanji River, HeMa River, and DaoTang River. (3) The concentration of CDOM in Qinghai Lake shows not only obvious seasonal variation (October, September and May, in the descending order) but also spatial variation. (4) The three-dimensional fluorescence spectrum matrix data of DOM in Qinghai Lake were analyzed by PARAFAC model, and four DOM fluorescence components with single maximum emission wavelength were analyzed.

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

Water ◽

10.3390/w13040494 ◽

2021 ◽

Vol 13 (4) ◽

pp. 494

Author(s):

Zenglei Han ◽

Min Xiao ◽

Fujun Yue ◽

Yuanbi Yi ◽

K. M. G. Mostofa

Keyword(s):

Molecular Weight ◽

Land Use ◽

Organic Matter ◽

Dissolved Organic Matter ◽

Fulvic Acid ◽

Low Flow ◽

Fluorescence Excitation ◽

Fluorescent Intensity ◽

River Catchment ◽

Unused Land

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.

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