Takejiro Takamatsu

The role of Mn2+-rich hydrous manganese oxide in the accumulation of arsenic in lake sediments

Arsenic is present at high concentrations in the upper layer of Lake Biwa sediments and shows a depth profile similar to that of Mn. Adsorption experiments of As onto synthetic hydrous Mn oxide (HMO) in the presence of Mn2+ and the speciation of Mn in the sediment cores, suggest that the accumulation of As at the sediment surface results from post-depositional migration of arsenite in the sediment pore water followed by oxidation to arsenate at the sediment surface and adsorption onto Mn2+-rich HMO.

Uptake and translocation of radiocesium in cedar leaves following the Fukushima nuclear accident.

Cryptomeria japonica trees in the area surrounding Fukushima, Japan, intercepted (137)Cs present in atmospheric deposits soon after the Fukushima nuclear accident in March 2011. To study the uptake and translocation of (137)Cs in C. japonica leaves, we analyzed activity concentrations of (137)Cs and the concentration ratios of (137)Cs to (133)Cs ((137)Cs/(133)Cs) in old and new leaves of C. japonica collected from a forest on Mount Tsukuba between 9 and 15 months after the accident. Both isotopes were also analyzed in throughfall, bulk precipitation and soil extracts. Water of atmospheric and soil origin were used as proxies for deciphering the absorption from leaf surfaces and root systems, respectively. Results indicate that 20-40% of foliar (137)Cs existed inside the leaf, while 60-80% adhered to the leaf surface. The (137)Cs/(133)Cs ratios inside leaves that had sprouted before the accident were considerably higher than that of the soil extract and lower than that of throughfall and bulk precipitation. Additionally, more than 80% of (137)Cs in throughfall and bulk precipitation was present in the dissolved form, which is available for foliar uptake, indicating that a portion of the (137)Cs inside old leaves was presumably absorbed from the leaf surface. New leaves that sprouted after the accident had similar (137)Cs/(133)Cs ratios to that of the old leaves, suggesting that internal (137)Cs was translocated from old to new leaves. For 17 species of woody plants other than C. japonica, new leaves that sprouted after the accident also contained (137)Cs, and their (137)Cs/(133)Cs ratios were equal to or higher than that of the soil extract. These results suggested that foliar uptake and further translocation of (137)Cs is an important vector of contamination in various tree species during or just after radioactive fallout.

Lead accumulation and location in the shoots of the aquatic liverwort Scapania undulata (L.) Dum. in stream water at greenside mine, England

Lead accumulation in the shoots of the aquatic liverwort Scapania undulata (L.) Dum. collected from a stream at an abandoned lead mine in England was studied with respect to its concentration, localization and chemical forms in the cells. The concentration of Pb in the stream water was 0.02 mg 1−1, and that of Pb in the shoots ranged from 0.7 to 2.4% Pb on a dry weight basis, giving an enrichment ratio of 3.5×105-1·2×106, Energy-dispersive X-ray microanalysis (XMA) of the cells showed localization of Pb in the cell wall, while Pb was not detected in the nucleus and other cell components. A study of sulphur speciation in the shoot showed that sulphide-S, which would indicate the presence of PbS, was undetectable at a distinguishable concentration ( <5 μg g−1). A insoluble sulphate-S concentration of 78 μg g−1, which may occur as PbSO4 was equivalent to about 3% of total Pb in the shoots of S. undulata.

Mechanisms of precipitation of manganese(II) in Lake Biwa, a fresh water lake

Abstract The precipitation mechanisms of Mn(II) were studied from the viewpoint of adsorption onto suspended solids (SS) and microbial oxidation of Mn in Lake Biwa. In aerobic water samples maintained in the laboratory, the concentration of dissolved Mn [Mn(II)] decreased at pH > 7 by microbially mediated oxidation. Filtration, autoclaving and irradiation of u.v. light of the water samples and the addition of NaN 3 inhibited the precipitation of Mn(II). The adsorption of Mn(II) onto SS was also appreciable at pH > 7, and attained equilibrium within at least 30 min. The oxidation rate of Mn(II) was much less than the adsorption rate. In various environments of the lake (bottom water, sediment surface, river mouth, etc.) the initial adsorption of Mn(II) and subsequent slow oxidation mediated by bacteria may be essential to the mechanisms of Mn(II) precipitation.

Simultaneous determination of atmospheric sulfur and nitrogen oxides using a battery-operated portable filter pack sampler

We developed a method to analyze atmospheric SO(x) (particulate SO(4)(2-)+ gaseous SO(2)) and NO(x) (NO + NO(2)) simultaneously using a battery-operated portable filter pack sampler. NO(x) determination using a filter pack method is new. SO(x) and NO(x) were collected on a Na(2)CO(3) filter and PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl) + TEA (triethanolamine) filters (6 piled sheets), respectively. Aqueous solutions were then used to extract pollutants trapped by the filters and the resulting extracts were pre-cleaned (e.g. elimination of PTIO) and analyzed for sulfate and nitrite by ion chromatography. Recoveries of SO(2) and NO(x) from standard pollutant gases and consistency of the field data with those from other instrumental methods were examined to evaluate our method. SO(x) and NO(x) could be analyzed accurately with determination limits of 0.2 ppbv and 1.0 ppbv (as daily average concentrations), respectively. The sampler can determine SO(x) and NO(x) concentrations at mountainous or remote sites without needing an electric power supply.

LUXURY PHOSPHATE UPTAKE AND VARIATION OF INTRACELLULAR METAL CONCENTRATIONS IN HETEROSIGMA AKASHIWO (RAPHIDOPHYCEAE)1

The effectr of phosphate starvation and subsequent uptake on distribution and concentration of phosphate metabolic intermediates and metals were studied in Heterosigma akashiwo (Hada) Hada by 31P‐NMR spectroscopy, neutron activation analysis and ESR spectroscopy. Excess orthophosphate (4.5 μM Pi, as NaH2PO4) added to a medium with P‐depleted H. akashiwo cells was rapidly taken up resulting in an increase in P cell quota (qp)from 68.2 to 99.6 fmol. cell‐1in 2 h and to 156.3 fmol. cell‐1in 6 h. After three days, qp approached about 190 fmol. cell−1. Polyphosphate (PPi) rapidly increased from 0 to 11.4 fmol· cell−1in 2 h and to 24.7 fmol·cell−1in 6 h. Diel variation of cell quota indicated that cellular Pi increase was synchronized with cellular PPi decrease and vice versa. The average chain length of PPi increased from ca. 0 to ca. 10.2 phosphate residues in 2 h after addition of Pi and one day later, from ca. 9.8 to ca. 12.5.

Annual Changes in Some Physiological Properties of Cryptomeria Japonica Leaves from Kanto, Japan

C. japonica leaves were sampled monthly in a heavily damaged area (a-I: Saitama), a slightly damaged area (a-II: plains in Ibaraki), and a healthy area (a-III: mountainous areas in Ibaraki) in Kanto. The leaves were analyzed for apparent cuticular transpiration rates, amounts of epicuticular wax, and contact angles. Sb in aerosols deposited on the leaves was also analyzed. The transpiration rates and the increase in transpiration with leaf aging were higher in a- I than in a-II and a-III. Erosion rates of the wax were higher in a-I and a-II than in a-III. The decrease of contact angles with aging tended to be higher in a-I and a-II than in a-III. Rates of aerosol-Sb deposition on the leaves were in the order a-I ≫ a-II > a-III. The transpiration rates correlated with the values obtained from a linear binomial function that included the amounts of wax and aerosol-Sb as variables (r = 0.855, P < 0.01). In a-l, the large quantity of aerosols on the leaves (and probably gaseous air pollutants) may have increased the transpiration rates by ca. 50% owing to erosion of the wax and stomatal malfunction, placing C. japonica under chronic water stress.

Mineralogy and geochemistry of sediments from Lakes Taupo and Waikaremoana, New Zealand

Abstract Sediments from Lakes Taupo and Waikaremoana, New Zealand, have been analysed to give background concentrations of trace elements in lakes relatively uninfluenced by anthropogenic contributions. Lake Waikaremoana sediments have higher contents of illite, chlorite, smectite, plagioclase, and quartz as well as higher contents of Al, Fe, Na, K, Mg, Ti, P, V, Cr, Co, Ni, Zn, Rb, Sr, Ba, Sc, U, Th, and Rare Earth Elements (REE), than Lake Taupo sediments. Diagenetic enrichment of Mn, Ni, Cu, Zn, P, As, and Fe was observed in surface sediments of certain cores from Lake Taupo where the surface sediment layer was preserved during coring.

Estimation of Mineral Weathering Rates under Field Conditions Based on Base Cation Budget and Strontium Isotope Ratios

Base cation (BC) concentrations of rain, throughfall, percolation from leaf litter, and soil solution were periodically measured in two forests: Kannondai (red pine stand on volcanic soil) and Yasato (deciduous stands on granitic soil). Calculation of a BC budget gave the rate of BC release from soils; the BCs originated from mineral weathering and cation exchange. Weathering rates under field conditions were estimated from the Sr isotope ratios (87Sr/86Sr) of water and soil samples. Isotope ratios decreased in the order rain > throughfall > percolation > soil solution. Clay and silt had extremely high isotope ratios; this suggests that the sandy fraction, whose isotope ratio was smaller than that of the soil solution, was the main contributor to mineral weathering. Estimated BC weathering rates (kmolc-ha-1y-1) were 1.16 for Ca and 0.57 for Mg at Kannondai, and 0.82 for Ca and 0.51 for Mg at Yasato. The unexpected high weathering rate of granitic soil in Yasao was due to the wide coverage of the original parent material by volcanic ash. The contribution of cation exchange derived by subtraction was a little smaller than the weathering rates and was similar to the values estimated from a dynamic model that we developed.

Coniferous coverage as well as catchment steepness influences local stream nitrate concentrations within a nitrogen-saturated forest in central Japan

High concentrations of nitrate have been detected in streams flowing from nitrogen-saturated forests; however, the spatial variations of nitrate leaching within those forests and its causes remain poorly explored. The aim of this study is to evaluate the influences of catchment topography and coniferous coverage on stream nitrate concentrations in a nitrogen-saturated forest. We measured nitrate concentrations in the baseflow of headwater streams at 40 montane forest catchments on Mount Tsukuba in central Japan, at three-month intervals for 1 year, and investigated their relationship with catchment topography and with coniferous coverage. Although stream nitrate concentrations varied from 0.5 to 3.0 mgN L-1, those in 31 catchments consistently exceeded 1 mgN L-1, indicating that this forest had experienced nitrogen saturation. A classification and regression tree analysis with multiple environmental factors showed that the mean slope gradient and coniferous coverage were the best and second best, respectively, at explaining inter-catchment variance of stream nitrate concentrations. This analysis suggested that the catchments with steep topography and high coniferous coverage tend to have high nitrate concentrations. Moreover, in the three-year observation period for five adjacent catchments, the two catchments with relatively higher coniferous coverage consistently had higher stream nitrate concentrations. Thus, the spatial variations in stream nitrate concentrations were primarily regulated by catchment steepness and, to a lesser extent, coniferous coverage in this nitrogen-saturated forest. Our results suggest that a decrease in coniferous coverage could potentially contribute to a reduction in nitrate leaching from this nitrogen-saturated forest, and consequently reduce the risk of nitrogen overload for the downstream ecosystems. This information will allow land managers and researchers to develop improved management plans for this and similar forests in Japan and elsewhere.