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

Water ◽  
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.

scholarly journals Discharge and Temperature Controls of Dissolved Organic Matter (DOM) in a Forested Coastal Plain Stream

Water ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 2919
Author(s):  
Yuehan Lu ◽  
Peng Shang ◽  
Shuo Chen ◽  
Yingxun Du ◽  
Marco Bonizzoni ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
High Temperatures ◽  
Coastal Plain ◽  
Stream Water ◽  
Water Discharge ◽  
Low Flow ◽  
Fluorescence Excitation ◽  
In Situ Modification ◽  
Total Fluorescence

Streams in the southeastern United States Coastal Plains serve as an essential source of energy and nutrients for important estuarine ecosystems, and dissolved organic matter (DOM) exported from these streams can have profound impacts on the biogeochemical and ecological functions of fluvial networks. Here, we examined hydrological and temperature controls of DOM during low-flow periods from a forested stream located within the Coastal Plain physiographic region of Alabama, USA. We analyzed DOM via combining dissolved organic carbon (DOC) analysis, fluorescence excitation–emission matrix combined with parallel factor analysis (EEM-PARAFAC), and microbial degradation experiments. Four fluorescence components were identified: terrestrial humic-like DOM, microbial humic-like DOM, tyrosine-like DOM, and tryptophan-like DOM. Humic-like DOM accounted for ~70% of total fluorescence, and biodegradation experiments showed that it was less bioreactive than protein-like DOM that accounted for ~30% of total fluorescence. This observation indicates fluorescent DOM (FDOM) was controlled primarily by soil inputs and not substantially influenced by instream production and processing, suggesting that the bulk of FDOM in these streams is transported to downstream environments with limited in situ modification. Linear regression and redundancy analysis models identified that the seasonal variations in DOM were dictated primarily by hydrology and temperature. Overall, high discharge and shallow flow paths led to the enrichment of less-degraded DOM with higher percentages of microbial humic-like and tyrosine-like compounds, whereas high temperatures favored the accumulation of high-aromaticity, high-molecular-weight, terrestrial, humic-like compounds in stream water. The flux of DOC and four fluorescence components was driven primarily by water discharge. Thus, the instantaneous exports of both refractory humic-like DOM and reactive protein-like DOM were higher in wetter seasons (winter and spring). As high temperatures and severe precipitation are projected to become more prominent in the southeastern U.S. due to climate change, our findings have important implications for future changes in the amount, source, and composition of DOM in Coastal Plain streams and the associated impacts on downstream carbon and nutrient supplies and water quality.

scholarly journals Linkage between the temporal and spatial variability of dissolved organic matter and whole stream metabolism

2012 ◽  
Vol 9 (12) ◽  
pp. 18253-18293 ◽  
Author(s):  
S. Halbedel ◽  
O. Büttner ◽  
M. Weitere
Keyword(s):  
Molecular Weight ◽  
Land Use ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Primary Production ◽  
Gross Primary Production ◽  
Low Molecular Weight ◽  
Stream Metabolism ◽  
First Time ◽  
Dom Composition

Abstract. Dissolved organic matter (DOM) is an important resource for microbes, thus affecting the whole stream metabolism. The factors influencing its chemical composition and thereby also its bio-availability are complex and not thoroughly understood. We hypothesized that the whole stream metabolism itself can affect the DOM composition and that the coupling of both is influenced by seasonality and different land use forms. We tested this hypothesis in a comparative study on two pristine forestry streams and on two non-forestry streams. The investigated streams were located in the Harz Mountains (Central Europe, Germany). The whole stream metabolism was measured with a classical two station oxygen change technique and the variability of DOM with fluorescence spectroscopy. We take also into account the geochemical and geophysical characteristic of each stream. All streams were clearly net heterotrophic, whereby the non-forestry streams showed a higher primary production in general, which was correlated with irradiance and with the total phosphorus concentration. The whole stream metabolism but also the chromophoric DOM (CDOM) showed distinct seasonal patterns. We detected three CDOM component groups (C1, C2, C3) by the use of the parallel-factor-analysis (PARAFAC) and found temporarily variable, typical component fingerprints (C1:C2, C1:C3, C3:C2) for CDOM originated from forestry streams and from non-forestry streams. Based on comparative literature studies and correlation analysis with different indices, we demonstrate that two of the components are clearly from terrigenous sources (C1, C3) and one is rather autochthonously (C2) derived. The whole CDOM matrix was dominated by humic like, high molecular-weight substances, followed by humic like, fulfic acids, low molecular-weight substances, and with minor amounts of amino-acids and proteins. We showed for the first time a correlation between the gross primary production (GPP) and the autochthonously derived, low molecular weight DOM. The amount of autochthonously produced DOM increased overall with increasing GPP, as indicated by a tight, positive correlation between the fluorescence index (FI, R2 = 0.84) or C2 (R2= 0.48) and the ratio of GPP and the daily community respiration (CR24). This study showed for the first time the linkage between whole stream metabolism and DOM composition, based on a new integrated approach. We demonstrated that this relationship is influenced by seasonality and different land use forms. These complex mechanisms lead to typical DOM fingerprints for streams pass through the different land use forms.

scholarly journals Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land use

2013 ◽  
Vol 10 (11) ◽  
pp. 6969-6986 ◽  
Author(s):  
E. Asmala ◽  
R. Autio ◽  
H. Kaartokallio ◽  
L. Pitkänen ◽  
C. A. Stedmon ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Land Use ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Agricultural Land ◽  
Natural Forest ◽  
Bacterial Growth Efficiency ◽  
Co2 Fluxes ◽  
Natural Forests ◽  
Degradation Rates

Abstract. The microbial degradation of dissolved organic carbon and nitrogen (DOC, DON) was studied in three Finnish boreal estuaries with contrasting land use patterns (Kiiminkijoki – natural forest and peatland; Kyrönjoki – agricultural; Karjaanjoki – mixed/urban). Bioassays of 12–18 d long durations were used in 3 seasons at in situ temperatures. Besides the bulk parameters, a suite of dissolved organic matter (DOM) quality parameters were also investigated, including colored DOM (CDOM), fluorescent DOM and the molecular weight of DOM. Bioavailable DOC and DON pools varied significantly between the estuaries, from 7.9 to 10.6% and from 5.5 to 21.9%, respectively. DOM originating from the catchment dominated by natural forests and peatlands (Kiiminkijoki) had the lowest DOC and DON degradation rates, as well as the lowest proportions of biodegradable DOC and DON. A greater proportion of agricultural land in the catchment increased the bioavailability of DON, but not the bioavailability of DOC (Kyrönjoki). Additionally, DOM quality varied significantly between the estuaries, and DOM originating from the agricultural Kyrönjoki catchment sustained higher DOC and DON degradation rates and higher bacterial growth efficiency (BGE) compared to those of the natural forest and peat dominated Kiiminkijoki catchment. The quality of DOM, indicated by differences in CDOM, fluorescent DOM and molecular weight, varied between estuaries with differing land use and was concluded to be major driver of BGE of these systems and thereafter to the microbial CO2 fluxes from the estuaries. The differences in BGE resulted in a 5-fold difference in the calculated daily bacterial CO2 emissions between the study's estuaries due to bacterial activity, ranging from 40 kg C d−1 in the Karjaanjoki estuary to 200 kg C d−1 in the Kyrönjoki estuary. Lower DOC:DON ratios, smaller molecular weight and higher CDOM absorption spectral slope values of DOM resulted in higher proportion of the initial DOC and DON being transferred to microbial growth and therefore to the pelagic food web. The pristine, peatland and forest-dominated Kiiminkijoki catchment had the lowest BGE, and therefore proportionally highest CO2 fluxes.

scholarly journals Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land-use

2013 ◽  
Vol 10 (6) ◽  
pp. 9819-9865 ◽  
Author(s):  
E. Asmala ◽  
R. Autio ◽  
H. Kaartokallio ◽  
L. Pitkänen ◽  
C. A. Stedmon ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Land Use ◽  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Agricultural Land ◽  
Natural Forest ◽  
Bacterial Growth Efficiency ◽  
Co2 Fluxes ◽  
Natural Forests ◽  
Degradation Rates

Abstract. The microbial degradation of dissolved organic carbon and nitrogen (DOC, DON) was studied in three boreal estuaries with contrasting land use patterns (Kiiminkijoki – natural forest and peatland; Kyrönjoki – agricultural; Karjaanjoki – mixed/urban). Bioassays conducted for 12–18 days were used in 3 seasons at in situ temperatures. Besides the bulk parameters, a suite of dissolved organic matter (DOM) quality parameters were investigated, including colored DOM (CDOM), fluorescent DOM and the molecular weight of DOM. Bioavailable DOC and DON pools varied significantly between the estuaries, from 7.9% in Kiiminkijoki to 10.6% in Karjaanjoki and from 5.5% in Kiiminkijoki to 21.9% in Kyrönjoki, respectively. DOM originating from catchment dominated by natural forests and peatlands had the lowest DOC and DON degradation rates, as well as the lowest proportions of biodegradable DOC and DON. A greater proportion of agricultural land in the catchment increased the bioavailability of DON, but not the bioavailability of DOC. Also DOM quality varied significantly between the estuaries, and DOM originating from the agricultural Kyrönjoki catchment sustained higher DOC and DON degradation rates and higher bacterial growth efficiency (BGE) compared to those of the natural forest and peat dominated Kiiminkijoki catchment. The quality of DOM, indicated by differences in CDOM, fluorescent DOM and molecular weight, varied between estuaries with differing land use and was concluded to be major driver of BGE of these systems and thereafter to the microbial CO2 fluxes from the estuaries. The differences in BGE resulted in a 5-fold differences in the calculated daily bacterial CO2-emissions between the study estuaries due to bacterial activity, ranging from 40 kg C d–1 in Karjaanjoki estuary to 200 kg C d–1 in Kyrönjoki estuary. Two of the study systems (Karjaanjoki, mixed land use; Kyrönjoki, intensive agriculture) in which the DOM pool had lower DOC : DON ratio, smaller molecular weight and higher CDOM absorption spectral slope values resulted in higher proportion of the initial DOC and DON being transferred to microbial growth and therefore to the pelagic food web. The pristine, peatland and forest-dominated Kiiminkijoki catchment had the lowest BGE, and therefore proportionally highest CO2 fluxes. The slope coefficient S275–295 was a good proxy of molecular weight across estuaries and seasons, and also for different diagenetic stages of DOM during biological degradation.

Characteristics of fouling due to clay-organic substances in potable water treatment by ultrafiltration

1996 ◽  
Vol 34 (9) ◽  
pp. 157-164 ◽  
Author(s):  
Kim C.-H. ◽  
M. Hosomi ◽  
A. Murakami ◽  
M. Okada
Keyword(s):  
Molecular Weight ◽  
Organic Matter ◽  
Humic Acid ◽  
Fulvic Acid ◽  
Size Distribution ◽  
Ultrafiltration Membrane ◽  
Organic Substances ◽  
Decomposition Products ◽  
Microbial Decomposition ◽  
Fouling Materials

Effects of clay on fouling due to organic substances and clay were evaluated by model fouling materials and kaolin. Model fouling materials selected were protein, polysaccharide, fulvic acid, humic acid and algogenic matter (EOM:ectracellular organic matter, microbial decomposition products) and kaolin was selected as the clay material. Polysulfone membrane (MWCO(Molecular Weight Cut-Off) 10,000, 50,000 and 200,000) was used as an ultrafiltration membrane. In particular, the flux measurement of solutions containing algogenic matter used an ultrafiltration membrane of MWCO 50,000. The flux of protein and polysaccharide with coexistence of kaolin increased in the case of the ratio of MW/MWCO being greater than one, but did not increase in the case of the MW/MWCO ratio being below one. In contrast, the flux of fulvic acid and humic acid with coextence of kaolin decreased regardless of the ratio of MW/MWCO. The addition of dispersion agent and coagulant in the organic substances and kaolin mixture solution changed the size distribution of kaolin, and resulted in a change of the flux. EOM and microbial decomposition products decreased with the increase of the fraction of organic matter having molecular weight more than MWCO of membrane. The flux of the algogenic organic matter with coexistence of kaolin decreased with the increase of the amount of kaolin. It was suggested that the decline of the flux with coexistence of kaolin was due to the change of the resistance of the kaolin cake layer corresponding to the change in kaolin size distribution with charge.

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