Yuzuru Nakaguchi

An off-line automated preconcentration system with ethylenediaminetriacetate chelating resin for the determination of trace metals in seawater by high-resolution inductively coupled plasma mass spectrometry

A novel automated off-line preconcentration system for trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb) in seawater was developed by improving a commercially available solid-phase extraction system SPE-100 (Hiranuma Sangyo). The utilized chelating resin was NOBIAS Chelate-PA1 (Hitachi High-Technologies) with ethylenediaminetriacetic acid and iminodiacetic acid functional groups. Parts of the 8-way valve made of alumina and zirconia in the original SPE-100 system were replaced with parts made of polychlorotrifluoroethylene in order to reduce contamination of trace metals. The eluent pass was altered for the back flush elution of trace metals. We optimized the cleaning procedures for the chelating resin column and flow lines of the preconcentration system, and developed a preconcentration procedure, which required less labor and led to a superior performance compared to manual preconcentration (Sohrin et al.). The nine trace metals were simultaneously and quantitatively preconcentrated from ∼120 g of seawater, eluted with ∼15 g of 1M HNO3, and determined by HR-ICP-MS using the calibration curve method. The single-step preconcentration removed more than 99.998% of Na, K, Mg, Ca, and Sr from seawater. The procedural blanks and detection limits were lower than the lowest concentrations in seawater for Mn, Ni, Cu, and Pb, while they were as low as the lowest concentrations in seawater for Al, Fe, Co, Zn, and Cd. The accuracy and precision of this method were confirmed by the analysis of reference seawater samples (CASS-5, NASS-5, GEOTRACES GS, and GD) and seawater samples for vertical distribution in the western North Pacific Ocean.

Species and Concentrations of Selenium and Nutrients in Tanabe Bay during Red Tide due to Gymnodinium nagasakiense

A red tide due toGymnodinium nagasakiense was observed in August 1988 in Tanabe Bay, Wakayama Prefecture, Japan. The maximum cell concentration ofG. nagasakiense reached 1×105 cells ml−1 at the surface water. From May to September 1988, the following were monitored: water temperature, salinity, chlorophylla, D.O., dissolved nutrients (NO2−N, NO3−N, NH4−N, PO4−P DON, DOP), particulate nutrients (PON, POP) and three dissolved selenium species [Se(IV), Se(VI), Organic Se]. Dissolved inorganic nitrogen (NO3−N, NH4−N) decreased but PON, POP, DON, DOP and inorganic phosphate increased at the peak of the bloom. The concentration of organic selenium increased up to the bloom initiation period which started on 5 July, and then the concentration of Se(IV) increased as the concentration of organic selenium decreased at the peak of the bloom (3 August). The strong relationship was found between the concentration of Se(IV) and the cell concentration ofG. nagasakiense (r2=0.98). The Se(IV) requirement ofG. nagasakiense was 2.89×10−17 moles cell−1, which was agreed well with 4.4×10−17 moles cell−1 found in a laboratory experiment onG. nagasakiense using selenium spiked artificial sea water medium. The average ratio of Se(IV) to dissolved inorganic nitrogen (DIN) during the red tide bloom was 1∶1441, the ratio of Se(IV) to DIN at the surface with the maximum cell concentration ofG. nagasakiense of 1×105 cells ml−1 was 1∶137. These results suggested that selenium may play an important role in red tide outbreak ofG. nagasakiense.

Simultaneous monitoring of aerosols and PM2.5 over Osaka

For a better understanding of aerosols, simultaneous measurements of aerosols and suspended particulate matter(SPM) have been undertaken at Kinki University campus in Higashi-Osaka. The relationship between aerosol properties obtained from radiometry with a multi-spectral photometer as a NASA/AERONET station and SPM concentrations such as TSP, PM10, PM2.5, and OBC with SPM-613D (Kimoto Electric) is examined. It is found that there is a linear correlation between SPM concentrations and aerosol properties, which indicates that aerosol characteristics can be estimated from SPM data, and vice versa. It is also shown that the air quality of the Higashi-Osaka site is poor due to not only anthropogenic particles produced by local emissions, such as diesel vehicles and chemical industries, but also due to dust particles coming from continental desert areas by large scale climatic conditions. As a result, long term simultaneous monitoring of aerosols and SPM provides us with three types of particles according to the season for atmospheric aerosols at an industrial city of Higashi-Osaka.

Aerosol retrieval over urban cities

In order to understand the atmospheric constituents over the urban area, the aerosol properties obtained from radiometry with AERONET are compared with the suspended particulate matter (SPM) simultaneously measured with a new instrument (SPM-613D). It is found that the SPM measurements classified as fine particles (PM2.5) and coarse particles (TSP/PM10) are very useful for determining the dominating of particle size and air quality. There was a strong correlation between the PM2.5 concentration and aerosol index (AI). It indicates that aerosol characteristics can be estimated from SPM data, and vice versa.