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著者：S. Nagao1, H. Kodama2, T. Miyajima3, T. Tanaka4題名：Radiocarbon of aquatic humic and fulvic acids in the Chikugo River waters発表情報：4th Asia-Pacific Symposium on Radiochemistry '09キーワード：概要：Humic substances are a heterogeneous and complicated mixture of organic materials with wide range of molecular sizes. They are the largest fraction of dissolved organic matter in natural waters and act as a complexing ligand for trace elements in aquatic environments. The characteristics of aquatic humic and fulvic acids are important to understand the sources and dynamics of aquatic humic and fulvic acids in river systems. This study reports the downward trend in ∆14C and 13C of dissolved humic and fulvic acids isolated from river waters along the Chikugo River, which is located in Kyushu Island in Japan.
The humic substances were isolated from 5.3 to 18.8 ton of the river waters at five stations from the upper to lower Chikugo River, which is 143-km long and 2863 km2 of watershed, using the XAD extraction method on November 7–11 in 2005. The percentage of fulvic acid is 70±5% to total humic substances. Stable carbon isotopic ratio is determined by mass spectrometry and is reported in 13C notation versus the VPDB standard. Radiocarbon in humic samples was determined using accelerator mass spectrometry (AMS) at the Japan Atomic Energy Agency. Radiocarbon values are reported as ∆14C corrected for sample 13C.
The ∆14C of dissolved humic and fulvic acids ranges from –64 to -15‰ and –35 to +20‰, respectively. The 13C values have –25.7~-23.6‰ for the humic acids and –27.3~-26.2‰ for the fulvic acids. The averaged values of ∆14C and 13C are –39±18‰ and –25.0±0.9‰ for the humic acids, respectively, and -8±21‰ and –26.8±0.5‰ for the fulvic acids. The ∆14C and 13C values of fulvic acids are younger and lighter than those of humic acids. The ∆14C of fulvic acids decrease from +20‰ in the upper site to -35‰in the lowest site. The downward trend is similar with that of humic acids. The differences in ∆14C between humic and fulvic acids also decrease with increasing the distance from the upper stream. These results suggest that the supply of older humic and fulvic acids from watershed increase downward along the Chikugo River.抄録：英語フィールド
Author：S. Nagao1, H. Kodama2, T. Miyajima3, T. Tanaka4Title：Radiocarbon of aquatic humic and fulvic acids in the Chikugo River watersAnnouncement information:4th Asia-Pacific Symposium on Radiochemistry '09An abstract：Humic substances are a heterogeneous and complicated mixture of organic materials with wide range of molecular sizes. They are the largest fraction of dissolved organic matter in natural waters and act as a complexing ligand for trace elements in aquatic environments. The characteristics of aquatic humic and fulvic acids are important to understand the sources and dynamics of aquatic humic and fulvic acids in river systems. This study reports the downward trend in ∆14C and 13C of dissolved humic and fulvic acids isolated from river waters along the Chikugo River, which is located in Kyushu Island in Japan.
The humic substances were isolated from 5.3 to 18.8 ton of the river waters at five stations from the upper to lower Chikugo River, which is 143-km long and 2863 km2 of watershed, using the XAD extraction method on November 7–11 in 2005. The percentage of fulvic acid is 70±5% to total humic substances. Stable carbon isotopic ratio is determined by mass spectrometry and is reported in 13C notation versus the VPDB standard. Radiocarbon in humic samples was determined using accelerator mass spectrometry (AMS) at the Japan Atomic Energy Agency. Radiocarbon values are reported as ∆14C corrected for sample 13C.
The ∆14C of dissolved humic and fulvic acids ranges from –64 to -15‰ and –35 to +20‰, respectively. The 13C values have –25.7~-23.6‰ for the humic acids and –27.3~-26.2‰ for the fulvic acids. The averaged values of ∆14C and 13C are –39±18‰ and –25.0±0.9‰ for the humic acids, respectively, and -8±21‰ and –26.8±0.5‰ for the fulvic acids. The ∆14C and 13C values of fulvic acids are younger and lighter than those of humic acids. The ∆14C of fulvic acids decrease from +20‰ in the upper site to -35‰in the lowest site. The downward trend is similar with that of humic acids. The differences in ∆14C between humic and fulvic acids also decrease with increasing the distance from the upper stream. These results suggest that the supply of older humic and fulvic acids from watershed increase downward along the Chikugo River.