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Acid deposition is widespread in Japan, but acidification of stream water is rare in forest ecosystems. Bedrock‐derived cations, including those released into the soil by weathering of bedrock minerals, generally act to neutralize acid deposition and flow out into streams. Volcanic ash, which is widespread in Japan, may also release cations and neutralize acids, but the contribution of volcanic‐ash‐derived cations is currently poorly explored. To assess the importance of volcanic ash as a source of base cations, we examined strontium in two catchments underlain by chert bedrock at Mount Amamaki, Japan. Additionally, we obtained comparative data from two sandstone‐bedrock catchments in the same area. We measured 87Sr/86Sr ratios in samples of stream water, bulk precipitation, riverbed rock, and soil from the catchments. We used the 87Sr/86Sr data to analyze the relative contributions of atmospheric deposition, bedrock, and volcanic ash in soil as sources of Sr in the stream waters. We estimated volcanic ash in soil to contribute between 46% and 78% of stream‐water Sr for one chert‐bedrock catchment, and between 0% and 52% for the other. We conclude that volcanic ash in soil is an important source of Sr in stream water. Thus, volcanic ash can act as a source of base cations and hence contribute to the acid‐neutralizing capacity of soil in forest ecosystems in Japan. [ABSTRACT FROM AUTHOR]

Collection and cooking of wild vegetables have provided seasonal enjoyments for Japanese local people as provisioning and cultural ecosystem services. However, the Fukushima Daiichi Nuclear Power Plant accident in March 2011 caused extensive radiocesium contamination of wild vegetables. Restrictions on commercial shipments of wild vegetables have been in place for the last 10 years. Some species, including buds of Aralia elata, are currently showing radiocesium concentrations both above and below the Japanese reference level for food (100 Bq/kg), implying that there are factors decreasing and increasing the 137Cs concentration. Here, we evaluated easy-to-measure environmental variables (dose rate at the soil surface, organic soil layer thickness, slope steepness, and presence/absence of decontamination practices) and the 137Cs concentrations of 40 A. elata buds at 38 locations in Fukushima Prefecture to provide helpful information on avoiding collecting highly contaminated buds. The 137Cs concentrations in A. elata buds ranged from 1 to 6,280 Bq/kg fresh weight and increased significantly with increases in the dose rate at the soil surface (0.10–6.50 μSv/h). Meanwhile, the 137Cs concentration in A. elata buds were not reduced by decontamination practices. These findings suggest that measuring the latest dose rate at the soil surface at the base of A. elata plants is a helpful way to avoid collecting buds with higher 137Cs concentrations and aid in the management of species in polluted regions. [ABSTRACT FROM AUTHOR]

A two‐stage sampler was designed to investigate the vertical distribution of heavy metals and trace elements that contaminate forest soils through atmospheric deposition. The hand‐corer consisted of two L‐shaped aluminum angles that were driven separately into the soil to reduce friction between the corer wall and the soil. This allowed for soil cores to be collected with less compression than with traditional corers. The corer is easily made, inexpensive, lightweight, and easy to carry. The degree of compression of soil cores collected at a depth of 20 cm from various montane forests in Japan was usually less than 10% (collected core length >18 cm); although, more compression occurred in soil with a higher air content. The degree of compression of soil cores collected from urban forests was lower than that in montane forests. When the two‐stage sampler was compared with a tube‐type sampler in a Japanese cedar (Cryptomeria japonica) forest, the compression degree of a soil core collected with the two‐stage sampler was a quarter that of the tube‐type sampler. The collection of less‐compressed soil cores will allow for reconstruction of a more accurate linear depth distribution of contaminants. To demonstrate this, we investigated the vertical distribution of Pb, Sb, and radioactive 137Cs in soil cores collected from conifer plantations on Mount Tsukuba, Japan, in April 2011. The migration centers of anthropogenic Pb, Sb, and 137Cs were positioned at 7.9, 7.5, and 3.3 cm from the ground surface, respectively. These distances probably reflect differences in the history of atmospheric pollution. [ABSTRACT FROM AUTHOR]

The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil. [ABSTRACT FROM AUTHOR]

A heterogeneous chiral imidazolodinone catalyst was synthesized by immobilization on a sulfated chitin through non‐covalent ionic interactions. The chitin‐based organocatalyst promoted the asymmetric Diels‐Alder reaction with high enantioselectivity under heterogeneous conditions and was successfully reused multiple times without apparent loss of catalytic activity and enantioselectivity. [ABSTRACT FROM AUTHOR]

Abstract This study investigated the transport of 137Cs within a forest ecosystem by examining temporal changes in the inventory and determining the major pathways of transfer following significant atmospheric deposition. A forested area of eastern Japan was monitored for four years immediately after the Fukushima nuclear power plant accident in March 2011 that released a large amount of radionuclides. The long physical half-life of 137Cs means that contamination can persist for decades, so it is vital to understand the mechanisms underlying the 137Cs dynamics in ecosystems. We sampled litterfall, throughfall, and soil, mainly from a cedar stand, over a four-year period, and analyzed the 137Cs concentrations of each sample to determine the transfer rate and total inventory. After validating our methodology through a comparison with results from an earlier study, we determined the temporal changes in the 137Cs distribution and in the major transfer pathway. Results showed that most 137Cs intercepted by canopies was transferred rapidly over the first nine months, and that the major pathway was not litterfall but throughfall. The ecological half-life of the 137Cs stocked in the canopy was calculated for both the early and later stages of contamination. Although the former is consistent with previous results, the latter ecological half-life is somewhat longer, probably because of dependence on the meteorological and tree physiological conditions at the site. This study presents valuable new data on the post-Fukushima 137Cs contamination, enhancing our understanding of the associated dynamics in forest ecosystems. Graphical abstract Unlabelled Image Highlights • The Fukushima accident provided an opportunity to understand the fate of radionuclides • An area in Japan was monitored for 137Cs transfer from canopies to the forest floor • Throughfall transferred much more 137Cs than litterfall, regardless of tree species. • At a cedar stand, most 137Cs was transferred within nine months of the accident. • General trends obtained by comparisons with previous studies are also discussed. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We assessed how warm air temperatures, high solar radiation, and weak wind speeds might induce hypoxia in a shallow lake during a heat wave. We simulated bottom‐water dissolved oxygen concentrations and compared concentrations in 2022 with the average for the previous 30 years. We found that hypoxia was most sensitive to wind speeds. When the wind speed was low, convection was insufficient to prevent hypoxia, but there was no hypoxia if the wind speed equaled the average speed during the previous 30 years. However, if solar radiation and air temperatures equaled the respective averages during the previous 30 years, hypoxia did not occur, even if wind speeds were low. We conclude that the combined effects of weak winds and either high solar radiation or air temperatures induced hypoxia during the heat wave of 2022. Plain Language Summary: The concentration of dissolved oxygen (DO) is one of the most important characteristics of lake ecosystems. However, a mechanistic understanding of the formation of bottom‐water DO in shallow water during heat waves is still limited by the paucity of relevant data. We combined high‐frequency monitoring via a new buoy system and numerical simulation to analyze how meteorological changes during a heat wave affected bottom‐water DO concentration in a shallow lake. We found that slackening of wind speeds and increases of either air temperatures or solar radiation induced bottom‐water hypoxia by constraining convective mixing. Wind speeds during the night were low, and the supply of DO by convective mixing during the night was insufficient to prevent hypoxia. Key Points: Hypoxia was observed in Lake Kasumigaura during a heat wave in 2022We observed higher solar radiation and air temperatures, and weaker winds in 2022 than the average for the previous 30 yearsInsufficient convection led to hypoxia because of the combined effects of weak winds, high solar radiation, and high air temperatures [ABSTRACT FROM AUTHOR]

Abstract: Soil cores and rainwater were sampled under canopies of Cryptomeria japonica in four montane areas along an atmospheric depositional gradient in Kanto, Japan. Soil cores (30cm in depth) were divided into 2-cm or 4-cm segments for analysis. Vertical distributions of elemental enrichment ratios in soils were calculated as follows: (X/Al)i/(X/Al)BG (where the numerator and denominator are concentration ratios of element-X and Al in the i- and bottom segments of soil cores, respectively). The upper 14-cm soil layer showed higher levels of Cu, Zn, As, Sb, and Pb than the lower (14–30cm) soil layer. In the four areas, the average enrichment ratios in the upper 6-cm soil layer were as follows: Pb (4.93)≥Sb (4.06)≥As (3.04)>Zn (1.71)≥Cu (1.56). Exogenous elements (kg/ha) accumulated in the upper 14-cm soil layer were as follows: Zn (26.0)>Pb (12.4)>Cu (4.48)≥As (3.43)≥Sb (0.49). These rank orders were consistent with those of elements in anthropogenic aerosols and polluted (roadside) air, respectively, indicating that air pollutants probably caused enrichment of these elements in the soil surface layer. Approximately half of the total concentrations of As, Sb, and Pb in the upper 14-cm soil layer were derived from exogenous (anthropogenic) sources. Sb showed the highest enrichment factor in anthropogenic aerosols, and shows similar deposition behavior to NO3 −, which is a typical acidic air pollutant. There was a strong correlation between Sb and NO3 − concentrations in rainfall (e.g., in the throughfall under C. japonica: [NO3 −]=21.1 [dissolved Sb], r =0.938, p <0.0001, n =182). Using this correlation, total (cumulative) inputs of NO3 − were estimated from the accumulated amounts of exogenous Sb in soils, i.e., 16.7t/ha at Mt. Kinsyo (most polluted), 8.6t/ha at Mt. Tsukuba (moderately polluted), and 5.8t/ha at the Taga mountain system (least polluted). There are no visible ecological effects of these accumulated elements in the Kanto region at present. However, the concentrations of some elements are within a harmful range, according to the Ecological Soil Screening Levels determined by the U.S. Environmental Protection Agency. [Copyright &y& Elsevier]

Abstract: Surface soil samples, which had no significant As contamination, were examined for As(V) reduction, As(III) oxidation and As mobilization capability. All five soil samples tested exhibited microbial As(V)-reducing activities both in aerobic and anaerobic conditions. Under aerobic conditions when As(V) reduction had almost ceased, oxidation of As(III) to As(V) occurred, whereas only As(V) reduction was observed under anaerobic conditions. In cultures incubated with As(III), As(III) was oxidized by indigenous soil microbes only under aerobic conditions. These results indicate that microbial redox transformations of As are ubiquitous in the natural environment regardless of background As levels. Mobilization through microbially mediated As(V) and Fe(III) reduction occurred both in the presence and absence of oxygen. Significant variation in dissolved As occurred depending on the Fe contents of soils, and re-immobilization of As arose in the presence of oxygen, presumably as a consequence of dissolved As(III) and Fe(II) oxidation. There was no apparent correlation between dissolved Fe(II) and As, suggesting that reductive dissolution of Fe(III) minerals does not necessarily determine the extent of As release from soils. [Copyright &y& Elsevier]

Dry deposition fluxes (F L) of NO3 − and SO4 2− to leaf surfaces were measured for Japanese red pine (Pinus densiflora), Japanese cedar (Cryptomeria japonica), Japanese cypress (Chamaecyparis obtusa), and Japanese white oak (Quercus myrsinaefolia), together with atmospheric concentrations (C L) of NO x (NO+NO2), T-NO3 (gaseous HNO3 +particulate NO3 −) and SO x (gaseous SO2 +particulate SO4 2−) around the leaves in a suburban area of Japan, using a modified leaf-washing technique. F L of NO3 − and SO4 2− decreased as follows: pine>>cedar>cypress≥oak and pine>>cedar>oak≥cypress, respectively. F L of NO3 − for all tree species fluctuated synchronously with C L of T-NO3. F L of SO4 2− fluctuated with C L of SO x , but the dominant pollutant deposited (SO2 or SO4 2−) appeared to differ for different tree species. Dry deposition conductance (K L) of T-NO3 and SO x was derived as an F L/C L ratio. Seasonal variations of K L likely reflect the gas/particle ratios of T-NO3 and SO x , which were affected by meteorological conditions such as temperature. Dry deposition velocities (V d) of T-NO3 and SO x were obtained as the mathematical product of annual mean K L and the total leaf surface areas in the forests. The comparison of V d among tree species indicated that the loads of acidic air pollutants were higher to coniferous forests than broad-leaved forest because of the higher K L and/or larger leaf surface areas. [Copyright &y& Elsevier]

We investigated bioremediation of As-contaminated soils by reductive dissolution of As using a dissimilatory As(V)-reducing bacterium (DARB), Bacillus selenatarsenatis SF-1. We also examined the effect of anthraquinone-2,6-disulfonate (AQDS), an extracellular electron-shuttling quinone, on the As extraction. When B. selenatarsenatis was incubated with As(V)-laden Al precipitates, no acceleration of As dissolution was observed in the presence of AQDS, even though the microbial reduction of AQDS occurred actively. In contrast AQDS addition significantly enhanced the reductive dissolution of As and Fe in analogous experiments with As(V)-laden Fe(III) precipitates, whereas As dissolution did not occur in the absence of the As(V) reducer. These results indicate the dissolution of As was accelerated by indirect reduction of solid-phase Fe(III) following microbial AQDS reduction, although As(V) reduction is vital for As extraction. B. selenatarsenatis was able to extract As from two types of industrially contaminated soils through reduction of solid-phase As(V) and Fe(III). The copresence of AQDS with B. selenatarsenatis improved the removal efficiency of As from the contaminated soils, concomitantly releasing Fe(II), suggesting that simultaneous use of DARB and electron-shuttling compounds can be an effective strategy for remediation of As-contaminated soils. [ABSTRACT FROM AUTHOR]

Japanese cedar (Cryptomeria japonica) is the main timber species in Japan. The prediction of the temporal changes in the 137Cs concentration in the stemwood of Japanese cedar after the Fukushima nuclear accident is essential for optimizing forest management in contaminated areas. However, it is difficult to estimate the respective contributions of root and foliar uptake to 137Cs accumulation in stemwood from simple field measurements, especially in trees that contain the residue of initially-deposited 137Cs. In this study, we devised a method for estimating the rate of 137Cs root uptake into stemwood using the 133Cs content in stemwood and the 137Cs/133Cs ratio in the exchangeable fraction of soil. As a trial, the method was applied to a cedar stand in Fukushima Prefecture, using available monitoring data from prior studies over 5 years from August 2011 to August 2016. The mean annual rate of 137Cs root uptake into stemwood over this period was estimated as 53 ± 20 Bq m−2 yr−1. We note that our method likely provided a maximum estimate, because it is based on the assumptions that 133Cs in wood is exclusively supplied by root uptake, and that Cs isotopes are taken up by roots in the top 5 cm of mineral soil. Moreover, the mean annual increase of the 137Cs inventory in stemwood during the study period was measured as 108 Bq m−2 yr−1, although this value was associated with considerable uncertainty (95% confidence interval from −109 to 324 Bq m−2 yr−1). As a result, the maximum estimated rate of 137Cs root uptake into stemwood accounted for around half of the measured rate of 137Cs accumulation in stemwood. Our results show that the Cs isotopic approach has potential to distinguish the main pathway of stemwood contamination (i.e., root vs. foliar uptake) following radioactive fallout. Unlabelled Image • A method was devised for estimating the rate of 137Cs root uptake into stemwood. • We tested the method at a cedar stand in Fukushima using data from 2011 to 2016. • Maximum estimate accounted for the half of the total 137Cs accumulation in stemwood. • This isotopic approach can contribute to revealing the origin of 137Cs in stemwood. [ABSTRACT FROM AUTHOR]

Changes in 137Cs export over time following clearcutting were investigated in a Japanese forested catchment affected by the Fukushima nuclear accident. A total of 13% of the catchment area was clear-cut 2 years after the accident. Annual suspended solids (SS) export at the catchment outlet increased 1.4 to 2.0 times after clearcutting; however, 137Cs export increased slightly (up to 1.1 times), corresponding to 0.21% to 0.30% of the 137Cs inventory in the catchment. The smaller change in 137Cs export than in SS export was due to a rapid decrease in the activity concentration following clearcutting. This decrease was likely caused by both natural attenuation and SS derived from sources with a low activity concentration in the clear-cut area. Monitoring of the sediment transport from hillslopes in small-scale experimental plots showed that the 137Cs yield in the skid trail was 3.6 to 21 times greater than those in clear-cut and unlogged forest floors. This significant 137Cs transport was due to greater soil erosion (by up to two orders of magnitude) along the skid trail, despite the lower activity concentration than those in the other plots. This indicates that while skid trails were involved in the rapid decrease of the activity concentration of SS, they were a potential source of the increased export of 137Cs and SS. Net 137Cs export increased by clearcutting (the export excluding the decrease accompanied by natural attenuation) was estimated to account for only 0.092% of the inventory in the catchment for 2.5 years. These results imply that the impact of clearcutting on 137Cs export was temporary in this catchment. [ABSTRACT FROM AUTHOR]

Microbially mediated arsenate (As(V)) and Fe(III) reduction play important roles in arsenic (As) cycling in nature. Extracellular electron shuttles can impact microbial Fe(III) reduction, yet little is known about their effects on microbial As mobilization in soils. In this study, microcosm experiments consisting of an As-contaminated soil and microbial communities obtained from several pristine soils were conducted, and the effects of electron shuttles on As mobilization were determined. Anthraquinone-2,6-disulfonate (AQDS) and riboflavin (RF) were chosen as common exogenous and biogenic electron shuttles, respectively, and both compounds significantly enhanced reductive dissolution of As and Fe. Accumulation of Fe(II)-bearing minerals was also observed, which may lead to re-immobilization of As after prolonged incubation. Interestingly, Firmicutes -related bacteria became predominant in all microcosms, but their compositions at the lower taxonomic level were different in each microcosm. Putative respiratory As(V) reductase gene ( arrA ) analysis revealed that bacteria closely related to a Clostridia group, especially those including the genera Desulfitobacterium and Desulfosporosinus , might play significant roles in As mobilization. These results indicate that the natural soil microbial community can use electron shuttles for enhanced mobilization of As; the use of this type of system is potentially advantageous for bioremediation of As-contaminated soils. [ABSTRACT FROM AUTHOR]

Summary: In forest ecosystems, understanding the relationship between the vertical distribution of fine roots and residual soil nitrogen is essential for clarifying the diversity–productivity–water purification relationship.Vertical distributions of fine‐root biomass (FRB) and concentrations of nitrate‐nitrogen (NO3‐N) in soil water were investigated in a conifer plantation with three thinning intensities (Control, Weak and Intensive), in which hardwood abundance and diversity were low, moderate and high, respectively.Intensive thinning led to the lowest NO3‐N concentration in soil water at all depths (0–100 cm) and highest FRB at shallow depths (0–50 cm). The NO3‐N concentration at a given depth was negatively correlated with total FRB from the surface to the depth at which NO3‐N concentration was measured, especially at shallow depths, indicating that more abundant fine roots led to lower levels of downward NO3‐N leaching. FRB contributed positively to nitrogen content of hardwood leaves.These findings demonstrate that a hardwood mixture in conifer plantations resulted in sufficient uptake of NO3‐N from soil by well developed fine‐root systems, and translocation to canopy foliage. This study suggests that productivity and water purification can be achieved through a hardwood mixture in conifer plantations. [ABSTRACT FROM AUTHOR]

The temperature and oxygen environment play important roles in the desorption of 137Cs from freshwater lake sediment to lake water. In this study, 12 quarterly surveys were performed to measure the dissolved 137Cs concentration in surface and bottom lake water, the vertical distribution of water temperature, and the dissolved oxygen (DO) concentration at the upstream, midstream, and downstream sites of the Yokokawa Dam Lake in Fukushima Prefecture, Japan. Higher concentrations of dissolved 137Cs were detected in the bottom water than in the surface water, especially in the summer and midstream lake regions at depths of 8–21 m owing to higher temperatures, which activated the bacterial decomposition of organic matter, and anaerobization, which enhanced the NH 4 + in the pore water and 137Cs desorption from mineral particles. To compare the effects of anaerobization and increasing temperature on 137Cs desorption from sediment particles, intact sediment core samples were collected from the lake midstream and incubated for 1–14 days in a chamber under three controlled temperature and oxygen environment conditions: aerobic +10 °C; anaerobic +10 °C; and anaerobic +20 °C. The vertical distribution of 137Cs in the sediment pore water showed a similar profile as NH 4 + and K+, and both the increased temperature and reduced DO concentration enhanced the 137Cs desorption. A comparison of the standard partial regression coefficients of temperature and DO concentration in the multiple regression equation for the 137Cs concentration in pore water shows that the reduction of DO from saturation to zero at the water–sediment interface accelerated the desorption of 137Cs more strongly than did the temperature rise from 10 to 20 °C. The experimental results show a nearly inverse proportional relationship between NH 4 + and the distribution coefficients of 137Cs after thermodynamic correction, except in the surface layer. These findings indicate that the 137Cs concentration in pore water can be explained by the temperature-dependent chemical distribution between the solid–aqueous phase and its equilibrium with NH 4 +. [Display omitted] • Dissolved 137Cs in the midstream area of bottom lakewater is high in summer. • Reduced dissolved oxygen promotes Cs desorption more than temperature rise. • 137Cs desorption in sediment appears to be determined by NH 4 + dynamics. [ABSTRACT FROM AUTHOR]

Chemical transport models played key roles in understanding the atmospheric behaviors and deposition patterns of radioactive materials emitted from the Fukushima Daiichi nuclear power plant after the nuclear accident that accompanied the great Tohoku earthquake and tsunami on 11 March 2011. However, model results could not be sufficiently evaluated because of limited observational data. We assess the model performance to simulate the deposition patterns of radiocesium (137Cs) by making use of airborne monitoring survey data for the first time. We conducted ten sensitivity simulations to evaluate the atmospheric model uncertainties associated with key model settings including emission data and wet deposition modules. We found that simulation using emissions estimated with a regional-scale (500 km) model better reproduced the observed 137Cs deposition pattern in eastern Japan than simulation using emissions estimated with local-scale (50 km) or global-scale models. In addition, simulation using a process-based wet deposition module reproduced the observations well, whereas simulation using scavenging coefficients showed large uncertainties associated with empirical parameters. The best-available simulation reproduced the observed 137Cs deposition rates in high-deposition areas (=10 kBq m-2) within 1 order of magnitude and showed that deposition of radiocesium over land occurred predominantly during 15-16, 20-23, and 30-31 March 2011. [ABSTRACT FROM AUTHOR]

To investigate differences in culturable freshwater bacterioplankton between summer and winter, we examined specific bacterioplankton in the low temperature surface water of two shallow, hypereutrophic, temperate lakes in Japan over two winters, and compared our results with the previously published data. We used the size-exclusion assay method (SEAM), a cultivation-based approach that simply and effectively isolates typical freshwater bacterioplankton. The specific clusters detected in the winter samples were the Rhodoferax sp. BAL47 cluster (LimA and LimC), a predominant and ubiquitous freshwater lineage, and the LiUU-5-340 cluster. To confirm tolerance to low water temperature of winter-specific groups, we also compared growth rates at 5°C among several pure strains of typical freshwater bacterioplankton clusters belonging to the Rhodoferax sp. BAL47, Polynucleobacter necessarius, GKS98, LiUU-5-340, and IRD18C08 of the class Betaproteobacteria, and the Luna-1 and Luna-2 of the class Actinobacteria. Specific detectability of freshwater bacterioplankton clusters/subclusters by SEAM in the winter sample substantially correlated with the low temperature-specific growth characteristics of each isolate. Response to water temperature is a key control factor in freshwater bacterioplankton assemblage composition. These results provide important insights into the specific response to water temperature of several ubiquitous culturable freshwater bacterioplankton clusters inhabiting a temperate climate zone. [ABSTRACT FROM AUTHOR]

To investigate the nitrification potential of phyllospheric microbes, we incubated throughfall samples collected under the canopies of Japanese cedar ( Cryptomeria japonica) and analyzed the transformation of inorganic nitrogen in the samples. Nitrate concentration increased in the unfiltered throughfall after 4 weeks of incubation, but remained nearly constant in the filtered samples (pore size: 0.2 and 0.4 µm). In the unfiltered samples, δO and δN values of nitrate decreased during incubation. In addition, archaeal ammonia monooxygenase subunit A ( amoA) genes, which participate in the oxidation of ammonia, were found in the throughfall samples, although betaproteobacterial amoA genes were not detected. The amoA genes recovered from the leaf surface of C. japonica were also from archaea. Conversely, nitrate production, decreased isotope ratios of nitrate, and the presence of amoA genes was not observed in rainfall samples collected from an open area. Thus, the microbial nitrification that occurred in the incubated throughfall is likely due to ammonia-oxidizing archaea that were washed off the tree canopy by precipitation. [ABSTRACT FROM AUTHOR]

In the present study, we investigated the effect of antibiotics on microbial arsenate (As(V)) reduction and arsenite (As(III)) oxidation in sediments collected from a small pond and eutrophic lake. The As(V)-reducing activities were less susceptible to chloramphenicol in aerobic conditions than in anaerobic conditions. Aerobic As(V) reduction proceeded in the presence of diverse types of antibiotics, suggesting that As-resistant bacteria are widely antibiotic resistant. In contrast, some antibiotics, e.g., chloramphenicol, strongly inhibited aerobic As(III) oxidation. In addition, bacterial As(III) oxidase genes were scarcely amplified and Proteobacteria-related 16S rRNA genes drastically decreased in chloramphenicol-amended cultures. Erythromycin and lincomycin, which successfully target many Grampositive bacteria, scarcely affected As(III) oxidation, although they decreased the diversity of As(III) oxidase genes. These results indicate that the aerobic As(III) oxidizers in the sediment cultures are mainly composed of Proteobacteria and are more sensitive to certain types of antibiotics than the aerobic As(V) reducers. Our results suggest that antibiotic disturbance of environmental microbial communities may affect the biogeochemical cycle of As. [ABSTRACT FROM AUTHOR]

The free-living, cosmopolitan, freshwater betaproteobacterial bacterioplankton genus Polynucleobacter was detected in different years in 11 lakes of varying types and a river using the size-exclusion assay method (SEAM). Of the 350 strains isolated, 228 (65.1%) were affiliated with the Polynucleobacter subclusters PnecC (30.0%) and PnecD (35.1%). Significant positive correlations between fluorescence in situ hybridization and SEAM data were observed in the relative abundance of PnecC and PnecD bacteria to Polynucleobacter communities (PnecC + PnecD). Isolates were mainly PnecC bacteria in the samples with a high specific UV absorbance at 254 nm (SUVA254), and a low total hydrolysable neutral carbohydrate and amino acid (THneutralCH + THAA) content of the dissolved organic matter (DOM) fraction, which is known to be correlated with a high humic content. In contrast, the PnecD bacteria were abundant in samples with high chlorophyll a and/or THneutralCH + THAA concentrations, indicative of primary productivity. With few exceptions, differences in the relative abundance of PnecC and PnecD in each sample, determined using a high-sensitivity cultivation-based approach, were due to DOM quality. These results suggest that the major DOM component in the field, which is allochthonously or autochthonously derived, is a key factor for ecological niche separation between PnecC and PnecD subclusters. [ABSTRACT FROM AUTHOR]

Abstract: Speciation of Al, including inorganic monomeric Al (Ali, the sum of aquo, hydroxy and inorganically complexed forms), organic monomeric Al (Alo, the organically complexed form), and colloidal mineral Al (Alc, the fine particulate form that passes through a 0.4-μm pore size membrane filter), was investigated in stream waters (pH 6–8) of 4 watersheds in Japan. Total dissolved Al (Alt, the sum of Alc, Ali and Alo) ranged from 0.03 to 3.31μM, and Alc was a minor component (<22% of Alt) in most of the streams. Ali was dominant (71% of Alt) in stream waters with low concentrations of Alt (<0.25μM), while the Alo fraction (37%) was almost as large as the Ali fraction (39%) in the highest class (Alt >1μM). In spite of the variation in the range of reactive Al (Alr, the sum of Ali and Alo) in the 4 watersheds (Miomote, 0.03–3.27μM; Tsukuba, 0.06–0.71μM; Dorokawa, 0.05–0.71μM; Tama, 0.03–0.38μM), the entire data set for Alr could be expressed as a function of the ratio of dissolved organic C (DOC) and Ca: [Al r (μM)]= 0.13 [DOC/Ca (mol/mol)]+0.11 (r =0.86, P <0.001). Alr increased in proportion to the DOC/Ca ratio in Japanese stream waters. Although acidic deposition in Japan has already resulted in elevated concentrations of in stream waters, a high level of Ca (instead of Al) is serving as a major counterion for . However, an additional loading of acidic deposition may result in shortage of Ca and mobilization of Al as a counterion for , and continuous observation of the speciation of Al in Japanese stream waters may reveal future change in the conditions for mobilization of Al from “low Ca and high DOC” to “low Ca and high ”. [Copyright &y& Elsevier]

A novel dissimilatory antimonate [Sb(V)]-reducing bacterium, strain SVR, was isolated from soil of a former antimony (Sb) mine. Strain SVR coupled Sb(V) reduction to acetate oxidation with an apparent reduction rate of 2.4 mM d−1. The reduction of Sb(V) was followed by the precipitation and accumulation of white microcrystals in the liquid medium. The precipitates were initially small and amorphous, but they eventually developed to the crystal phase with a length > 50 µm. Strain SVR removed 96% of dissolved Sb as the precipitates. An X-ray diffraction analysis indicated that the microcrystals were the orthorhombic Sb trioxide (Sb 2 O 3), i.e. , valentinite. Phylogenetic and physiological analyses revealed that strain SVR is a member of the genus Geobacter. The cell suspension of strain SVR incubated with acetate and Sb(V) at pH 7.0 was able to form valentinite. Interestingly, at pH 8.0, the cell suspension formed another crystalline Sb 2 O 3 with a cubic structure, i.e. , senarmontite. Our findings provide direct evidence that Geobacter spp. are involved in Sb(V) reduction in nature. Considering its superior capacity for Sb removal, strain SVR could be used for the recovery of Sb and the individual productions of valentinite and senarmontite from Sb-contaminated wastewater. [Display omitted] • An anaerobic Sb(V)-reducing bacterium, Geobacter sp. SVR, was isolated. • Strain SVR reduced 5 mM Sb(V) completely within 2 d. • Following Sb(V) reduction, Sb was precipitated as Sb 2 O 3 microcrystals. • Orthorhombic or cubic Sb 2 O 3 microcrystals were formed depending on the pH. [ABSTRACT FROM AUTHOR]