Fractionation of Dissolved Organic Matter (DOM) as Precursors of Trihalomethane in Lake Biwa and Yodo Rivers

The objectives of this research were to characterize dissolved organic matter (DOM) by excitation-emission matrix (EEM) fluorescence spectroscopy and to apply humification index (HIX) to differentiate the origin and extent of humification of DOMs in watersheds of Lake Biwa and Lake Kasumigaura, Japan. EEM and HIX techniques were applied to lacustrine, riverine, and effluent organic matters. EEM spectra suggest that algal activity and the thermocline formation are critical to composition and distribution of DOM in Lake Biwa. Lake Kasumigaura DOM is evenly distributed over the lake. The effects of allochthonous sources are more conclusive for Lake Kasumigaura DOM than for Lake Biwa DOM. Seasonal and vertical variations in HIX were observed in Lake Biwa similar to results by EEM approach. Upstream DOMs were mostly humified fulvic acid originating from forest soil. DOM from a paddy field and municipal wastewater had the lowest HIX value and consisted mainly of less humified, fresh organic materials. Lacustrine and effluent DOMs demonstrated the same extent of humification in watersheds of Lake Biwa and Lake Kasumigaura. Allochthonous sources such as elution from a paddy field and municipal wastewater are more responsible for the composition of Lake Kasumigaura DOM compared to that of Lake Biwa DOM.

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Seasonal and spatial variations in characteristics of Lake Biwa dissolved organic matter: sorption of pyrene and its derivatives and fluorescence properties

Water Science & Technology ◽

10.2166/wst.2008.743 ◽

2008 ◽

Vol 58 (8) ◽

pp. 1609-1614

Author(s):

T. Kusakabe ◽

K. Ikeda ◽

Y. Shimizu ◽

S. Higashi ◽

Y. Kawabata ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Lake Biwa ◽

Vertical Mixing ◽

Three Dimensional ◽

Spatial Variations ◽

Fluorescence Properties ◽

Sorption Coefficient ◽

Suwannee River Fulvic Acid ◽

Seasonal And Spatial Variations

The objectives of this research were to investigate seasonal and spatial variations in (1) sorption of pyrene and its derivatives onto dissolved organic matter (DOM) and (2) fluorescence properties of DOM in Lake Biwa, Japan. In the case of pyrene, sorption coefficient (Kdoc) of Lake Biwa DOM seasonally changed from 1,200 to 3,800 L/kgC. Vertical distribution of Kdoc was affected by thermocline formation in summer, while it was uniformly distributed as a result of vertical mixing in winter. Functional groups affected sorption of pyrene onto Lake Biwa DOM in different manner from that onto Suwannee River fulvic acid. Three-dimensional excitation emission matrices (3D-EEMs) fluorescence spectroscopy was applied to characterize Lake Biwa DOMs and indicated the existence of at least two fluorophores. The two major peaks at Ex230/Em300 and Ex230/Em425 originated from protein-like and fulvic/humic-like substances, respectively. The peak at Ex230/Em300 showed the maximum fluorescence intensity at a depth of 5 m and could be affected by stratification of the water column in summer. On the other hand, the peak at Ex230/Em425 showed similar profiles both in summer and in winter. These results demonstrably showed that sorption of micropollutants and fluorescence properties of Lake Biwa DOMs were seasonally and spatially varied.

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