Microbial Changes in Selected Operational Descriptors of Dissolved Organic Matters From Various Sources in a Watershed

2013

CLEAN Soil Air Water

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Changes in the apparent characteristics of dissolved organic matter (DOM) upon photodegradation and their influences on disinfection by‐products formation potentials (DBPFP) were examined using biodegraded DOM from six different sources (leaf litter, algae, compost, paddy water, treated sewage, and headwater). After seven day UV irradiation, no substantial changes occurred in the dissolved organic carbon (DOC) concentrations, but significant decreases were observed for the specific UV absorbance. In general, fulvic‐like and humic‐like fluorophores appear to be more affected by photodegradation than protein‐like fluorophores (or DOM components) and/or than the DOM structures associated with a shorter excitation wavelength. Size exclusion chromatograms revealed that UV absorbing molecules of intermediate size ranging from 1 to 5 kDa were most vulnerable to the UV irradiation. Except for leaf litter‐derived DOM, UV irradiation did not lead to substantial changes in specific DBPFP (i.e. disinfection by‐product (DBP)/dissolved organic carbon) comparable to those of the DOM characteristics, suggesting that many of the DBP precursors were not easily removed by photodegradation or some photochemically produced compounds could operate as DBP precursors. All the DOM samples exhibited greater formation potential for haloacetic acids per organic carbon than trihalomethanes irrespective of the sources. In general, correlations between DOM properties and specific DBPFP became stronger after photodegradation. The intermediate sized UV‐absorbing moieties appear to be actively involved in forming DBPs for photodegraded DOM. An integrated region of protein‐like fluorescence intensities may be suggested as an estimation index for specific DBPFP independent of the DOM sources.

Section: Resultsmentioning

confidence: 99%

Photodegradation‐Induced Changes in the Characteristics of Dissolved Organic Matter with Different Sources and Their Effects on Disinfection By‐Product Formation Potential

Lee

2013

CLEAN Soil Air Water

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“…Instead, %FLF and % HLF increased with the water level. Synchronous fluorescence spectra of plant-derived DOM are generally characterized by high PLF and low FLF while FLF is predominant for those of soil-derived DOM (Hur 2009). Considering that soil and plant (or forests) leaching are possible mechanisms to provide DOM in rivers during rainfall, our results suggest that the compositional changes in DOM during the storm runoff may be dominated by the inflow of soilderived DOM.…”

Section: Changes In Spectroscopic Characteristicsmentioning

confidence: 99%

Changes in Spectroscopic and Molecular Weight Characteristics of Dissolved Organic Matter in a River During a Storm Event

Nguyen

Shin

2010

Water Air Soil Pollut

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Changes in dissolved organic matter (DOM) characteristics were investigated during a storm event in the Kyungan River using UV-visible, fluorescence spectroscopy, resin fractionation, and size exclusion chromatography (SEC). Water samples were collected at nine sampling times to reflect a variation of the river water level. A dramatic increase was observed for chemical oxygen demand (COD) versus biochemical oxygen demand, suggesting that non-biodegradable organic components may be more contained in the organic matters driven by the storm. Specific UV absorbance values increased from 2.15 to 3.16 L/mgC-m, reaching the maximum level at the highest water level. The storm runoff resulted in the reduction of protein-like fluorescence (PLF), the increase of fulvic-like and humic-like fluorescence for the synchronous fluorescence spectra of DOM. Weight-average molecular weight (MW w ) values increased from 1,100 to 1,510 Da due to the increment of high MW fractions in the SEC chromatograms. Overall changes in DOM composition may be explained by the inflow of soil-derived DOM from the upstream basins brought by the storm. The humification index (HIX) exhibited a positive correlation with MW w values, suggesting that HIX may be suggested to a prediction descriptor for DOM MW during the storm event. PLF presented a negative correlation with DOM MW, suggesting that protein-like fluorescent compounds are associated with low MW components in the river. More input of humic substances by the storm runoff appears to shift DOM into a higher MW value as revealed by a positive correlation between MW w and hydrophobic fraction.

“…SUVA values are known to have a positive relationship with aromatic carbon content of DOM (Weishaar et al 2003). In addition, SUVA value may be enhanced by microbial decomposition of DOM and thus higher SUVA value may reflect higher humification, more hydrophobic nature, and lower biodegradability of DOM (Hur 2010). In this respect, the high SUVA value observed at the S1 site appears to be associated with decomposed organic matters from dead algae and vegetation, and terrestrial debris in the sediment near the dam.…”

Section: Resultsmentioning

confidence: 97%

Multivariate analysis for spatial distribution of dissolved organic matters in a large river-type dam reservoir

Nguyen

Shin

2011

Environ Monit Assess

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In contrast to extensive studies of dissolved organic matters (DOM) in natural lakes, the distributions and the characteristics of DOM in artificial dam reservoirs have not been well documented despite a growing demand for the construction worldwide. For this study, spatial variations in the concentrations and the characteristics of DOM in Lake Paldang, a large river-type dam reservoir, were investigated using the concentrations, the specific UV absorbance (SUVA), the synchronous fluorescence spectra and the molecular weight (MW(w)) values. In addition, environmental factors determining the DOM spatial distribution were examined based on a principal component analysis (PCA). Variations in the DOM characteristics were greater than those for the concentrations (1.1-2.4 mg C/L). In contrast to typical lakes, vertical variations with a depth were much smaller than those observed among horizontal sampling sites within the reservoir. Irrespective of the depth, four individual sampling locations were easily distinguished by comparison of some selected DOM characteristics. The protein-like fluorescence (PLF), MW(w) and SUVA values observed at the location near the dam exceeded the corresponding values for the sampling locations near major influent rivers, suggesting that, even for the river-type dam reservoir, the downstream DOM characteristics may be governed by in-lake DOM production processes such as the release from sediments and algal activities. The results of principal component analysis (PCA) revealed that approximately 61% of the variance in DOM distribution might be explained by allochthonous/autochthonous carbon sources and predominant presence of either total nitrogen or total phosphorous over the other.