Kazuhiro Norisuye

Multielemental Determination of GEOTRACES Key Trace Metals in Seawater by ICPMS after Preconcentration Using an Ethylenediaminetriacetic Acid Chelating Resin

GEOTRACES is an international research project on marine biogeochemical cycles of trace elements and their isotopes. GEOTRACES key trace metals in seawater are Al (8-1000 ng/kg), Mn (4-300 ng/kg), Fe (1-100 ng/kg), Cu (30-300 ng/kg), Zn (3-600 ng/kg), and Cd (0.1-100 ng/kg), of which global oceanic distribution will be determined on a number of research cruises. This work introduces a novel method of solid-phase extraction to determine Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater by adjusting the pH of the sample to 6 and carrying out a single preconcentration step. The trace metals were collected from approximately 120 mL of seawater using a column of a chelating resin containing the ethylenediaminetriacetic acid functional group and eluted with approximately 15 mL of 1 M HNO3. Mn and Fe in the eluate were measured by inductively coupled plasma mass spectrometry (ICPMS) using the dynamic reaction cell mode, and the other metals were measured using the standard mode. Using this procedure, the trace metals were collected quantitatively, while >99.9% of alkali and alkaline earth metals in seawater were removed. The procedural blank was <7% of the mean concentration in deep ocean waters, except 16% for Pb. The overall detection limit was <14% of the mean concentration in deep ocean waters. The RSD was <9%. Our values for the trace metals in the certified reference materials of seawater NASS-5 and nearshore seawater CASS-4 agreed with the certified values (except that there is no certified value for Al). This method was also successfully applied to the reference materials of open-ocean seawater produced by the SAFe program. Our Fe concentrations were 5.9 +/- 0.7 ng/kg for surface water (S1) and 50.4 +/- 2.9 ng/kg for deep water (D2), which are in agreement with the interlaboratory averages of 5.4 +/- 2.4 and 50.8 +/- 9.5 ng/L, respectively. The data for other metals were oceanographically consistent.

Biosynthesis and release of methylarsenic compounds during the growth of freshwater algae.

Arsenic transformations by freshwater algae have been studied under laboratory conditions. By the use of a new analytical method, we identified methylarsenic(III) species in the growth medium of green-alga Closterium aciculare incubated under axenic conditions. The arsenate concentration in the experimental medium began to decrease just after inoculation, and the levels of arsenite and methylarsenicals increased with the growth of C. aciculare. Initially, most of the arsenate was converted into arsenite, which peaked in concentration during the exponential phase. Methylarsenicals accumulated rapidly in the stationary phase. DMAA(V) production was enhanced when the ratio of phosphate to arsenate decreased in the culture medium. The levels of DMAA(V) increased continuously toward the end of the experiment. On the other hand, methylarsenic(III) species remained relatively steady during the stationary phase. Methylarsenic(III) species accounted for 0-35% of methylarsenicals. These results suggest that arsenite and methylarsenicals (containing methylarsenic(III) species) are supplied by phytoplankton, and serve as evidence of the origin of methylarsenic(III) species in natural waters.

Iron-catalyzed aromatic amination for nonsymmetrical triarylamine synthesis.

Novel iron-catalyzed amination reactions of various aryl bromides have been developed for the synthesis of diaryl- and triarylamines. The key to the success of this protocol is the use of in situ generated magnesium amides in the presence of a lithium halide, which dramatically increases the product yield. The present method is simple and free of precious and expensive metals and ligands, thus providing a facile route to triarylamines, a recurrent core unit in organic electronic materials as well as pharmaceuticals.

Precise isotopic analysis of Mo in seawater using multiple collector-inductively coupled mass spectrometry coupled with a chelating resin column preconcentration method.

It is widely recognized that the natural isotopic variation of Mo can provide crucial information about the geochemical circulation of Mo, and the ocean is an important reservoir of Mo. To obtain precise isotopic data on Mo in seawater samples using multiple collector-inductively coupled plasma mass spectrometry (MC-ICPMS), we have developed a preconcentration technique using 8-hydroxyquinoline bonded covalently to a vinyl polymer resin (TSK-8HQ). By optimizing the procedure, Mo in seawater could be effectively separated from matrix elements such as alkali, alkaline earth, and transition metals. With this technique, even with a 50-fold enrichment factor, the changes in the 98Mo/95Mo ratio during preconcentration were smaller than twice the standard deviation (SD) in this study. Mass discrimination of Mo isotopes during the measurement was externally corrected for by normalizing 86Sr/88Sr to 0.1194 using an exponential law. We evaluated delta98/95Mo to a precision of +/- 0.08 per thousand (+/-2 SD); this value was found to be less than one-third of previous reported values. Moreover, we were able to determine an accurate ratio for every pair of stable Mo isotopes, which was impossible with previous methods owing to the isobaric interference from the external elements (Zr and Ru). In this study, delta92/98Mo in seawater was first determined so that it had the smallest relative error. We applied the proposed method to four kinds of seawater samples. The Mo compositions were constant among them, with average delta98/95Mo and delta92/98Mo values of 2.45 +/- 0.11 and -4.94 +/- 0.09 per thousand (+/-2 SD), respectively. Our data indicate that seawater is enriched in heavy Mo isotopes than previously reported.

The budget of dissolved trace metals in Lake Biwa, Japan

A comprehensive study on the dynamics of dissolved elements (Mg, Al, Si, P, Ca, V, Cr, Mn, Fe, Ni, Zn, As, Sr, Y, W, and U) in Lake Biwa was carried out using a clean technique. Lake water samples (n = 523) were collected from six stations in the North Basin and three stations in the South Basin. River water samples (n = 178) were collected from 14 major rivers flowing into the North Basin. Rainwater samples (n = 89) were collected at Otsu. The river water was enriched with Mn, Al, Fe, P, and Zn and the rainwater was enriched with Zn, Al, Fe, and Mn compared to North Basin water during winter mixing. The residence times of dissolved species were estimated on the basis of input through the rivers and rain. The residence times for Ca, Mg, and Sr were about 8 years, the same as that for water. Mn, Al, Fe, and Zn showed the shortest residence times (0.05–0.19 year). A budget calculation suggested that more than 60% of the input of dissolved Si, P, V, Cr, Mn, Fe, Ni, and Zn was scavenged and retained in the lake sediments and/or discharged as suspended particles.

Recent distribution of lead in the Indian Ocean reflects the impact of regional emissions

Significance Humans have altered the earth surface environment by massive injection of certain chemicals into our air and water. In some cases these injections are detrimental to environmental health and must be monitored to limit the damage (e.g., freons and the ozone layer); in other cases (e.g., freon dissolving into the ocean) there are no harmful consequences, but the chemicals are useful as tracers of ocean circulation patterns. Lead remains a major hazard when it is proximate to humans (e.g., plumbing, housepaint, and contaminated soils); in the open ocean, lead serves as an inadvertent experiment demonstrating how metals move through the marine environment. To our knowledge, this study is the first to examine the fate of human-injected lead in the Indian Ocean. Humans have injected lead (Pb) massively into the earth surface environment in a temporally and spatially evolving pattern. A significant fraction is transported by the atmosphere into the surface ocean where we can observe its transport by ocean currents and sinking particles. This study of the Indian Ocean documents high Pb concentrations in the northern and tropical surface waters and extremely low Pb levels in the deep water. North of 20°S, dissolved Pb concentrations decrease from 42 to 82 pmol/kg in surface waters to 1.5–3.3 pmol/kg in deep waters. South of 20°S, surface water Pb concentrations decrease from 21 pmol/kg at 31°S to 7 pmol/kg at 62°S. This surface Pb concentration gradient reflects a southward decrease in anthropogenic Pb emissions. The upper waters of the north and central Indian Ocean have high Pb concentrations resulting from recent regional rapid industrialization and a late phase-out of leaded gasoline, and these concentrations are now higher than currently seen in the central North Pacific and North Atlantic oceans. The Antarctic sector of the Indian Ocean shows very low concentrations due to limited regional anthropogenic Pb emissions, high scavenging rates, and rapid vertical mixing, but Pb still occurs at higher levels than would have existed centuries ago. Penetration of Pb into the northern and central Indian Ocean thermocline waters is minimized by limited ventilation. Pb concentrations in the deep Indian Ocean are comparable to the other oceans at the same latitude, and deep waters of the central Indian Ocean match the lowest observed oceanic Pb concentrations.

Determination of bismuth in open ocean waters by inductively coupled plasma sector-field mass spectrometry after chelating resin column preconcentration

A novel low-blank method is described for the analysis of bismuth in seawater based on preconcentration using an ethylenediaminetriacetic acid chelating resin column followed by determination with inductively coupled plasma sector-field mass spectrometry (ICPSFMS). A sample is siphoned into and drains through the column with the flow rate being kept constant by using a flotation device. Bi in 250 mL of acidified seawater is extracted onto the column in this process and eluted with 2 mL of 3 M HNO(3) followed by 3 mL of ultra-high purity water. The concentration of Bi in the eluate is measured by ICPMS. The benefits of the method compared to others are its simplicity, a smaller amount of seawater, and lower procedural blanks and detection limits at pg kg(-1) levels. Data on dissolved Bi in open ocean reference samples of SAFe and GEOTRACES programs are presented for the first time.

A method for preconcentrating Zr from large volumes of seawater using MnO2-impregnated fibers

A method for preconcentrating Zr from large volumes of seawater using MnO(2)-impregnated fibers is described. The manganese dioxide-impregnated fibers were synthesized from polypropylene cartridge filters by a redox reaction between KMnO(4) and MnCl(2). Seawater samples were introduced into an extraction system and Zr was extracted from the samples by the MnO(2)-impregnated fibers. Zirconium was recovered from the fibers through two steps of elution into aqueous solutions and measured by inductively coupled argon plasma atomic emission spectrometry. The average extraction efficiency for Zr was 59% on a single pass of 50-1000 l sample at flow rates of 8.1-15 l min(-1), and 100% on continuous circulation of 200 l sample at 15 l min(-1). The results indicate that Zr can be rapidly and easily preconcentrated onto MnO(2)-impregnated fibers from large volumes of seawater. This simple method can be applied to the preconcentration of trace dissolved Zr in natural water and removal of radiozirconium from radioactive waste fluid.

Erratum to: Stoichiometry among bioactive trace metals in seawater on the Bering Sea shelf

‘‘The stoichiometry of D-M in the Bering Sea shelf showed enrichment of trace metals, especially Al, Mn, Fe, Co and Cu compared with that in the North Pacific.’’ 2. In Fig. 10, there were mistakes in the calculation for the Pacific deep water. The original figure should be replaced by the following figure. -6 -5 -4 -3 -2 -1 Pacific outer/middle (BR003) middle (BR005) coastal (BR09-BR012) near Bering Strait (BR013)