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Your search keyword '"TAKAOKA, MASAKI"' showing total 362 results
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362 results on '"TAKAOKA, MASAKI"'

27. Assessing the complexation of dissolved organic matter with heavy metals (Cu2+, Pb2+) in leachate from an old Japanese landfill site using fluorescence quenching.

Author

Nguyen, Thi Ngoc, Takaoka, Masaki, Kusakabe, Taketoshi, and Shiota, Kenji

Abstract

Dissolved organic matter (DOM) in landfill leachate impacts the toxicity, bioavailability, and migration of heavy metals. The present study investigated the complexation of heavy metals (Cu2+ and Pb2+) with DOM from two landfill leachate samples, representing an old landfill site containing incineration residues and incombustible waste. The logarithms of the stability constant (log KM) and percentage of complexed fluorophores were calculated using both the Ryan–Weber non-linear model and the modified Stern–Volmer model, yielding good agreement. The log KM values (at pH = 6.0 ± 0.1) calculated using both methods for the two sampling points were 5.02–5.13 and 4.85–5.11 for Cu2+–DOM complexation, and 5.01–5.13 and 4.46–4.87 for Pb2+–DOM complexation, respectively. Log KM was slightly higher for binding of DOM with Cu2+ than Pb2+, and the quenching degree was stronger for complexation with Cu2+ (28.5–30.6% and 38.0–45.9%) than Pb2+ (6.5–7.1% and 10.0–15.4%) in both leachate samples. While log KM values were similar, differences in the contributions of functional groups and molecular composition led to varying degrees of quenching. This study reveals the potential for heavy metal binding by DOM in landfill leachate with a unique solid waste composition and emphasizes variations in fluorescence quenching between Cu2+ and Pb2+ despite similar log KM levels. These findings may be useful for assessing heavy metal behavior in landfill leachate and its impacts on the surrounding environment. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Characterization and spatiotemporal variations of fluorescent dissolved organic matter in leachate from old landfill-derived incineration residues and incombustible waste.

Author

Nguyen, Thi Ngoc, Kusakabe, Taketoshi, and Takaoka, Masaki

Subjects
DISSOLVED organic matter, LEACHATE, INCINERATION, FLUORESCENCE spectroscopy, TRACE metals, LANDFILLS
Abstract

Dissolved organic matter (DOM) influences the bioavailability and behavior of trace metals and other pollutants in landfill leachate. This research characterized fluorescent dissolved organic matter (FDOM) in leachate from an old landfill in Japan during a 13-month investigation. We employed excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC) to deconvolute the FDOM complex mixture into three fluorophores: microbial humic-like (C1), terrestrial humic-like (C2), and tryptophan-like fluorophores (C3). These FDOM components were compared with findings from other studies of leachate in landfills with different waste compositions. The correlations among EEM-PARAFAC components, dissolved organic carbon (DOC) concentration, and ultraviolet–visible and fluorescence indices were evaluated. The FDOM in leachate varied spatially among old and extended leachate collected in the landfill and leachate treatment facility. The FDOM changed temporally and decreased markedly in August 2019, November 2019, and April 2020. The strong positive correlation between HIX and %C2 (r = 0.87, ρ = 0.91, p < 0.001)) implies that HIX may indicate the relative contribution of terrestrial humic-like components in landfill leachate. The Fmax of C1, C2, and C3 and the DOC concentration showed strong correlations among each other (r > 0.72, ρ > 0.78, p < 0.001) and positive correlations with leachate level (r > 0.41, p < 0.001), suggesting the importance of hydrological effects and leachate pump operation on FDOM. [ABSTRACT FROM AUTHOR]

Published
2024
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