Ayako Nagano’s research while affiliated with Kagoshima University and other places

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Publications (3)


Background levels of atmospheric mercury in Kagoshima City, and influence of mercury emission from Sakurajima Volcano, Southern Kyushu, Japan
  • Article

November 2000

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52 Reads

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28 Citations

The Science of The Total Environment

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Ayako Nagano

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Hayao Sakamoto

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Norinobu Yonehara

Vapor phase mercury concentration was determined daily for 1 year (Jan. 1996-Jan. 1997) in order to present the levels of atmospheric mercury in Kagoshima City and to estimate the influence of mercury emission from Sakurajima Volcano, southern Kyushu, Japan. The atmospheric mercury was collected on a porous gold collector at Kagoshima University and was determined by cold vapor atomic absorption spectrometry; Kagoshima University of Kagoshima City is located approximately 11 km west of Sakurajima Volcano. The mercury concentration obtained was in the range 1.2-52.5 ng m(-3) (mean 10.8 ng m(-3), n = 169). The atmospheric concentration varied from season to season; the concentration was high in summer and lower in winter. A linear relation was obtained by plotting ln[Hg/ng m(-3)] vs. 1/T for the north, south and west winds with correlation coefficients of -0.76, -0.79 and -0.83, respectively, but no such dependency was found for the east wind (r = -0.035). When the wind is blowing from the east, Kagoshima City is on the leeward side of the volcano. The impact of the fumarolic activity of the volcano on ambient air in the city was evident in the disappearance of temperature dependency with the appearance of the east wind. Atmospheric mercury concentration except for the east wind was considered to be background levels of Kagoshima City. As background levels, 8.1 +/- 5.3 ng m(-3), 14.8 +/- 7.9 ng m(-3), 13.9 +/- 11.7 ng m(-3) and 4.4 +/- 1.6 ng m(-3) (mean +/- S.D.) were obtained for spring, summer, autumn and winter, respectively.


Mercury contamination in the Yatsushiro Sea, south-western Japan: Spatial variations of mercury in sediment

September 2000

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107 Reads

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92 Citations

The Science of The Total Environment

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Ayako Nagano

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Norinobu Yonehara

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[...]

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Hirokatsu Akagi

Mercury-contaminated effluent was discharged into Minamata Bay from a chemical plant over a 20-year period until 1965 (from 1958 to 1959, effluent was discharged into Minamata River), causing Minamata disease. In an effort to characterize the extent of the contamination in the Yatsushiro Sea, the vertical and horizontal distributions of mercury in sediment were investigated. Sediment was sampled at 62 locations in the southern part of the sea from 4 to 6 March 1996. In the lower layers of the long cores of sediment, the total amount of mercury was at a relatively uniform low concentration. We interpret these low values to represent the background concentration absent of anthropogenic influence. The background value thus estimated for the Yatsushiro Sea was 0.059±0.013 mg kg−1 (mean±S.D., n=51). The highest concentration in each sample ranged from 0.086 to 3.46 mg kg−1 (mean, 0.57 mg kg−1). The higher values were obtained at stations near Minamata Bay and the Minamata River (the sources of the pollution). Concentrations decreased with distance from the source. An inspection of the vertical profiles of mercury concentration in cores suggested that the deposited mercury had not been fixed in sediment but had been transported, despite 30 years having past since the last discharge of contaminated effluent. At nine stations, extractable inorganic and organic mercury concentrations were determined differentially. Inorganic mercury is the predominant species in sediment and organic mercury comprising approximately 1% of the total.


Differential Determination of Organic Mercury and Inorganic Mercury in Sediment, Soil and Aquatic Organisms by Cold-Vapor Atomic Absorption Spectrometry

June 1996

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39 Reads

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20 Citations

Analytical Sciences

A method has been proposed for the differential determination of inorganic and organic mercury in environmental and biological materials, based on their successive extraction followed by a cold vapor atomic absorption spectrometric (CVAAS) determination. Mercury was first extracted by shaking a sample with 1 M hydrochloric acid containing 3% sodium chloride in the presence of copper(I) chloride. In order to separate organic mercury from inorganic mercury, the extract was shaken with chloroform to extract only organic mercury. The chloroform phase was transferred into a 50 ml volumetric flask and 0.4 ml of 0.2% dithizone-chloroform solution was added. The contents of the flask was evaporated to dryness, followed by addition of 2 ml of 1 : 1 nitric acid-perchloric acid solution and 5 ml of concentrated sulfuric acid and heating at ca. 230 degrees C for 30 min. The hydrochloric acid phase containing inorganic mercury was transferred into a 50 ml volumetric flask, followed by addition of 1 mi of 60% perchloric acid and 5 ml of concentrated sulfuric acid and heating at ca. 230 degrees C for 30 min. After cooling, the digested sample solution was diluted with water to 50 mi. The mercury in each solution was determined by CVAAS. When 0.5 g amounts of artificial standard soil samples spiked with a given amount of organic mercury and inorganic mercury {20 ng (as Hg) of mercury(II) chloride and methylmercury chloride} were treated by the above-mentioned procedures, the recoveries were 102% and 97.0% with the relative standard deviations of 1.0% and 2.8%, respectively. This method was successfully applied to a differential determination of mercury in sediment, soil and fish meat samples.

Citations (3)


... The org-Hg concentrations were determined by the method of Tomiyasu et al. (1996) with some modifications (Tomiyasu et al. 2020a, b). This method does not require special equipment; mercury species were separated by solvent extraction and measured by CVAAS. ...

Reference:

The dynamics of mercury around an artisanal and small-scale gold mining area, Camarines Norte, Philippines
Differential Determination of Organic Mercury and Inorganic Mercury in Sediment, Soil and Aquatic Organisms by Cold-Vapor Atomic Absorption Spectrometry
  • Citing Article
  • June 1996

Analytical Sciences

... In addition, mercury is mainly concentrated in sediments and migrates along with the sediments. The sediment acts as a record of deposition, and its geographic distribution of mercury could indicate the temporal behavior of discharged mercury 9) . Therefore, the prediction of mercury migration based on sediments was regarded as an effective way. ...

Mercury contamination in the Yatsushiro Sea, south-western Japan: Spatial variations of mercury in sediment
  • Citing Article
  • September 2000

The Science of The Total Environment

... Mercury in the atmosphere is released from two emission sources: (1) natural and (2) anthropogenic emission sources. As for natural sources, volcanic activity; volatilization from mercury deposits; volatilization from soil, plants, and surface sea water; the weathering of rocks; and the kicking up of soil dust are potential sources of emissions (e.g., Tomiyasu et al., 2000). Anthropogenic sources include the burning of coal, mining of gold, production of cement, and the incineration of non-ferrous metals and wastes (Schroeder & Munthe, 1998). ...

Background levels of atmospheric mercury in Kagoshima City, and influence of mercury emission from Sakurajima Volcano, Southern Kyushu, Japan
  • Citing Article
  • November 2000

The Science of The Total Environment