17:15 〜 18:30
[AHW22-P09] 水酸化鉄(III)共沈濃縮法による琵琶湖水中溶存態メチルホスホン酸の検出
キーワード：溶存態メチルホスホン酸、共沈、リン制限湖沼、琵琶湖、イオンクロマトグラフィー
Introduction
Bacteria possibly utilizes P(III) species such as organophosphonates as P resources in freshwater lakes. At the subsurface layer of Lake Saiko (P-limited lake: Yamanashi, Japan), maximum methane concentration is observed under stratified condition in summer. This subsurface methane maximum (SMM) is considered to be formed by metabolism of methylphosphonate (MPn) by cyanobacterium Synecococcus to ingest phosphorus [Khatun et al., 2019]. In Lake Biwa (Shiga, the largest in Japan), mesotrophic lake, methane maximum layer is also formed in the epilimnion during summer stratification, but it is not sure this layer is formed by the same reason. We examined the existence of MPn in both lakes but it was not detected as dissolved form yet. However, MPn extracted from particulate matter was detected in Lake Saiko and eutrophic Lake Fukami-Ike (Nagano, Japan) [Tsuji et al., 2020].
We applied the ion chromatographic determination methods to detect dissolved MPn in water of Lake Biwa in combination with pre-concentration method of MPn with iron(III) hydroxide co-precipitation to enhance detection limit and remove matrix in water.
Methods
Analytical condition for the determination of MPn in water was already established by ion chromatography with high volume injection [Tsuji et al., 2019; Maruo et al., 2016]. Condition of MPn co-precipitation with iron(III) hydroxide was investigated by varying pH and amount of iron(III) hydroxide and MPn concentration. In fundamental investigation, MPn in 500 mL sample solution was concentrated by addition of freshly prepared iron(III)hydroxide from iron(II) chloride in the solution. Iron(III)hydroxide was collected on Nuclepore membrane filter (pore size; 0.4 micrometer), and MPn was released by immersing the filter in 25 mL ammonia solution (pH 10). Released MPn was analyzed by ion chromatography.
This method was applied to the determination of dissolved MPn in water samples of Lake Biwa (Shiga, Japan). Waters were sampled by Niskin-X sampler by Research Vessel “Hassaka”, The University of Shiga Prefecture, on Sep. 10, 2020, at St. T4 (close to Takeshima Island, max. depth 43 m).
Results and Discussion
pH ranges preferable to the preconcentration of MPn was investigated from pH 4 – 10. Finally, pH around 6 was preferable, and recovery of MPn in the concentration range 0.05 – 5 nM in the standard solution was stable (49 - 53%) independent of MPn concentration. Recovery of 5 nM MPn in 5 replicates was constant at the value of 50% (CV 1.6%). MPn was concentrated by 10 folds. Application of this method enabled the detection of MPn up to 0.03 nM in water. From the concentrated sample, dissolved MPn was detected in the concentration around 0.1 nM at the depth 0 – 30 m. At the bottom (43 m), 0.2 nM of MPn was detected probably because of bacterial activity in lake sediment.
References
Khatun S, Iwata T, Kojima H, Fukui M, Aoki T, Mochizuki S, Naito A, Kobayashi A, Uzawa R (2019) Aerobic methane production by planktonic microbes in lakes. Science of the Total Environment 696: 133916.
Maruo M, Ishimaru M, Azumi Y, Kawasumi Y, Nagafuchi O, Obata H (2016) Comparison of soluble reactive phosphorous and orthophosphate concentrations in river waters. Limnology 7: 7-12.
Tsuji K, Maruo M, Obata H (2019) Determination of trace methylphosphonate in natural waters by ion chromatography. Bunseki Kagaku 68: 275-278. (Japanese with English abstract)
Maruo M, Tsuji K, Iwata T, Oyagi M, Obata H (2020) Detection of prganophosphonates and phosphite in suspended matter of P-limited lakes. Abstract of JpGU2020 session #A-HW32.
Bacteria possibly utilizes P(III) species such as organophosphonates as P resources in freshwater lakes. At the subsurface layer of Lake Saiko (P-limited lake: Yamanashi, Japan), maximum methane concentration is observed under stratified condition in summer. This subsurface methane maximum (SMM) is considered to be formed by metabolism of methylphosphonate (MPn) by cyanobacterium Synecococcus to ingest phosphorus [Khatun et al., 2019]. In Lake Biwa (Shiga, the largest in Japan), mesotrophic lake, methane maximum layer is also formed in the epilimnion during summer stratification, but it is not sure this layer is formed by the same reason. We examined the existence of MPn in both lakes but it was not detected as dissolved form yet. However, MPn extracted from particulate matter was detected in Lake Saiko and eutrophic Lake Fukami-Ike (Nagano, Japan) [Tsuji et al., 2020].
We applied the ion chromatographic determination methods to detect dissolved MPn in water of Lake Biwa in combination with pre-concentration method of MPn with iron(III) hydroxide co-precipitation to enhance detection limit and remove matrix in water.
Methods
Analytical condition for the determination of MPn in water was already established by ion chromatography with high volume injection [Tsuji et al., 2019; Maruo et al., 2016]. Condition of MPn co-precipitation with iron(III) hydroxide was investigated by varying pH and amount of iron(III) hydroxide and MPn concentration. In fundamental investigation, MPn in 500 mL sample solution was concentrated by addition of freshly prepared iron(III)hydroxide from iron(II) chloride in the solution. Iron(III)hydroxide was collected on Nuclepore membrane filter (pore size; 0.4 micrometer), and MPn was released by immersing the filter in 25 mL ammonia solution (pH 10). Released MPn was analyzed by ion chromatography.
This method was applied to the determination of dissolved MPn in water samples of Lake Biwa (Shiga, Japan). Waters were sampled by Niskin-X sampler by Research Vessel “Hassaka”, The University of Shiga Prefecture, on Sep. 10, 2020, at St. T4 (close to Takeshima Island, max. depth 43 m).
Results and Discussion
pH ranges preferable to the preconcentration of MPn was investigated from pH 4 – 10. Finally, pH around 6 was preferable, and recovery of MPn in the concentration range 0.05 – 5 nM in the standard solution was stable (49 - 53%) independent of MPn concentration. Recovery of 5 nM MPn in 5 replicates was constant at the value of 50% (CV 1.6%). MPn was concentrated by 10 folds. Application of this method enabled the detection of MPn up to 0.03 nM in water. From the concentrated sample, dissolved MPn was detected in the concentration around 0.1 nM at the depth 0 – 30 m. At the bottom (43 m), 0.2 nM of MPn was detected probably because of bacterial activity in lake sediment.
References
Khatun S, Iwata T, Kojima H, Fukui M, Aoki T, Mochizuki S, Naito A, Kobayashi A, Uzawa R (2019) Aerobic methane production by planktonic microbes in lakes. Science of the Total Environment 696: 133916.
Maruo M, Ishimaru M, Azumi Y, Kawasumi Y, Nagafuchi O, Obata H (2016) Comparison of soluble reactive phosphorous and orthophosphate concentrations in river waters. Limnology 7: 7-12.
Tsuji K, Maruo M, Obata H (2019) Determination of trace methylphosphonate in natural waters by ion chromatography. Bunseki Kagaku 68: 275-278. (Japanese with English abstract)
Maruo M, Tsuji K, Iwata T, Oyagi M, Obata H (2020) Detection of prganophosphonates and phosphite in suspended matter of P-limited lakes. Abstract of JpGU2020 session #A-HW32.