Dissolved organic carbon and fluorescence in Lake Hovsgol: factors reducing humic content of the lake water

Hayakawa, Kazuhide; Sekino, Tatsuki; Yoshioka, Takahito; Maruo, Masahiro; Kumagai, Michio

doi:10.1007/s10201-003-0092-3

Cited by 36 publications

(24 citation statements)

References 31 publications

(31 reference statements)

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“…DOC concentrations close to those we found in Lake Biwa (73-138 mol L Ϫ1 ) have been reported in other large lakes, including Hovsgol (80-100 mol L Ϫ1 , Hayakawa et al 2003), Superior (110-120 mol L Ϫ1 , Biddanda et al 2001), and Constance (121-192 mol L Ϫ1 , Weiss and Simon 1999), but our data are among the first that demonstrated the downward transport and subsequent mineralization of DOM in a large freshwater lake. We found that DOC and DON accumulate in the epilimnion during the stratification period to be redistributed into the deeper layer during the winter overturn period, followed by the mineralization at depth as indicated by significant decreases in concentrations in the hypolimnion over the stratification period.…”

Section: Discussionsupporting

confidence: 89%

Role of dissolved organic matter in hypolimnetic mineralization of carbon and nitrogen in a large, monomictic lake

2006

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We tested the hypothesis that dissolved organic matter (DOM) is delivered to deep layers by convective mixing in winter, where it contributes to the mineralization of C, N, and P in the oxygenated hypolimnion of large (surface area 674 km 2 , maximum depth 104 m), monomictic Lake Biwa. Basin-scale, seasonal measurements of DOM concentrations revealed that dissolved organic carbon (DOC) and nitrogen (DON) accumulated in the epilimnion during warm seasons and were redistributed into the deeper layer during winter overturn. Hypolimnetic DOC and DON decreased in concentration over the stratification period, indicating mineralization; the contributions of DOM to the total mineralization of C and N were 8% and 30%, respectively. Higher contribution of N relative to C suggests that the N-rich DOM was mineralized at depth. We failed to detect a significant contribution of dissolved organic phosphorus to P mineralization in the hypolimnion, which could be explained by substantial depletion in P relative to C and N of DOM; C : P and N : P ratios were 1,978 and 147, respectively. The data suggest that convective mixing in this monomictic basin delivers DOM to hypolimnetic depths, where it is mineralized during subsequent periods of stratification.

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Section: Discussionsupporting

confidence: 89%

Role of dissolved organic matter in hypolimnetic mineralization of carbon and nitrogen in a large, monomictic lake

2006

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“…In Lake Baikal, Russia, an oligotrophic lake, DOC was present at concentrations of 1.08-1.32 mg C l Ϫ1 in the summer, and DOC concentrations in the main basin were controlled by loading from the Barguzin River and the Selenga River, its main inflowing rivers (Yoshioka et al 2002). In Lake Hovsgol, Mongolia, DOC levels were 0.96-1.2 mg C l Ϫ1 and humic substances were considered to be the main component of DOC (Hayakawa et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Distribution of dissolved organic carbon in lakes of different trophic types

et al. 2004

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The distributions of dissolved organic carbon (DOC) in the warm season were elucidated in ten lakes of different trophic types in Japan, Russia, and China. DOC showed similar vertical distributions in all the lakes in summer when thermal stratification occurred. DOC in the epilimnion was higher than the value of 0.8 mg C l Ϫ1 found in the hypolimnion. In three Japanese lakes, hypolimnion DOC was negatively correlated with apparent oxygen utilization (AOU), reflecting the net oxidation of DOC using the dissolved oxygen in lake water. The DOC : O 2 ratios (0.115-0.179), calculated by the slopes of the regression lines of DOC versus AOU in hypolimnion water, were as low as those of deep-sea water, which indicates low bioavailability of lake water DOC for heterotrophic bacteria. DOC and conductivity did not correlate well except in two Japanese lakes: one showed a positive correlation and the other a negative correlation, indicating DOC loading from the inflowing rivers. Eutrophic lakes tended to have higher DOC values than meso-and oligotrophic lakes, and DOC values in the surface water negatively correlated with Secchi depths.

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“…It was reported that the fluorescence properties of terrestrial FDOM changed due to natural solar effects from upstream to the lacustrine environments at the watershed level (Mostofa et al, 2005b;Hayakawa et al, 2003). The upstream DOM has unique characteristic properties due to the sole sources of origin, such as forests or swamp ecosystems (Steinberg and Münster, 1985;Malcolm, 1985Malcolm, , 1990.…”

Section: Introductionmentioning

confidence: 99%

Photodegradation of fluorescent dissolved organic matter in river waters

et al. 2007

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Photodegradation of dissolved organic matter (DOM), collected from two upstream and one downstream sites in the Lake Biwa watershed in Japan, was investigated using fluorescence properties of three-dimensional excitation emission matrix (3-D EEM). Solar irradiation caused a decrease in the dissolved organic carbon (DOC) concentration and in the fluorescence peak intensity (FI) of fulvic acid (FA)-and protein-like substances in DOM. Mineralization of DOC during an irradiation period (13 days) was observed to be higher in upstream samples (32-36%) compared to that in downstream sample (16%). DOC concentration in samples stored in the dark significantly decreased in the downstream sample (16%), while those in upstream samples hardly decreased (1-8%). The FI of FA-like substance decreased by 72-84% during 13-days irradiation (integrated solar intensity = 176 MJ m -2 ). The protein-like fluorescence was only observed in the downstream sample and the net decrease in the FI was 59% in the irradiated sample. The first-order reaction kinetics was applied to analyze the photodegradation of DOM. Two-step photodegradation was suggested for the fluorescent DOM (FDOM), while not for the DOC. Results obtained here suggested that FA-like FDOM is more susceptible to photodegradation compared with those of protein-like substances and DOC.Keywords: dissolved organic carbon, fulvic acid-like fluorescence, protein-like fluorescence, photodegradation, streams as benzene containing carboxyl, methoxylate and phenolic groups, hydroxycoumarin-like structures, and fluorophores containing the Schiff-base system, chromone, xanthone, and quinoline derivatives (Senesi, 1990;Leenheer and Croue, 2003). On the other hand, amino acids in freshwaters have been detected in a combined form, mostly humic bound or colloidal in river waters (Volk et al., 1997;Baker et al., 2007) and affected by anthropogenic sources (Baker, 2001(Baker, , 2002a(Baker, , 2002bMostofa et al., 2005a). FA-and protein-like substances are the major components of the fluorescent dissolved organic matter (FDOM) in natural waters (Senesi, 1990;Coble, 1996; Yamashita and Tanoue, 2003 and references therein). The florescent components such as FA-and protein-like substances have been investigated by the three-dimensional excitation emission matrix (3-D EEM). Due to simplicity of the 3-D EEM technique, it is now widely used for characterization of FDOM and for determinations of the nature, sources and quantity of FDOM in natural waters (Baker, 2001(Baker, , 2002aCoble, 1996;Yamashita and Tanoue, 2003;Mostofa, 2005; Mostofa et al., 2005a, b). The 3D-EEM of FA-or humiclike substances in the aquatic DOM, in general, has been shown a major fluorescence peak within a range of excitation/emission (Ex/Em) wavelengths of 320-390/420-490 nm (Coble et al

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Dissolved organic carbon and fluorescence in Lake Hovsgol: factors reducing humic content of the lake water

Cited by 36 publications

References 31 publications

Role of dissolved organic matter in hypolimnetic mineralization of carbon and nitrogen in a large, monomictic lake

Role of dissolved organic matter in hypolimnetic mineralization of carbon and nitrogen in a large, monomictic lake

Distribution of dissolved organic carbon in lakes of different trophic types

Photodegradation of fluorescent dissolved organic matter in river waters

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