Shigeto Kawashima

Carbon monoxide, hydrogen, and methane uptake by soils in a temperate arable field and a forest

CO, H2, and CH4 uptake by the soil of an arable field and a forest soil (360 m apart) was measured by a closed-chamber method in temperate Japan for about 1 year. CO production observed was exponentially dependent on top soil temperature. CO production was greater in the forest soil than in the soil of the arable field at the same soil temperature. (Gross) CO, H2, and CH4 deposition velocities ranged from 0 to 7×10−2, from 0 to 9×10−2, and from 0.05 to 0.1×10−2 cm s−1 in the arable field and from 1.5 to 4.5×10−2, 5 to 8×10−2, and from 0.3 to 0.6×10−2 cm s−1 in the forest, respectively. Variations in the deposition velocities were smaller in the forest than in the arable field and corresponded to variations in soil moisture in the top soil. Seasonal trends caused by the variation in temperature were observed only for CH4 deposition, reflecting the clear dependence on soil temperature. Application of dead plant material to the arable field led to acceleration of CO and H2 deposition onto the soil. The deposition velocities of CO and H2 were positively correlated (n =36, R2* = 0.881, p<0.0001; R2* is the coefficient of determination adjusted by degrees of freedom) in the arable field and (n = 37, R2* = 0.408, p<0.0001) in the forest, suggesting diffusion control on their deposition velocities.

Automated pollen monitoring system using laser optics for observing seasonal changes in the concentration of total airborne pollen

The development of a simple and automatic pollen measurement methodology is required to manage allergic problems caused by airborne pollen. We developed a device and algorithm to automatically monitor airborne pollen by using basic laser optics technology. The device measures the sideward and forward scattering intensities of laser light from each particle. Because this device provides detailed temporal variation in the pollen concentration, the dispersal dynamics of airborne pollen can be effectively analyzed. We compared the pollen counts obtained with the automated method and standard Hirst-type method. Scatter-plot graphs were constructed of the forward and sideward scattering intensities of the observed particles. An extract window methodology was used to estimate the concentrations of the major allergenic pollens. The extract window parameters were obtained for major types of allergenic pollen. The results suggest the possibility of developing a device for monitoring several types of airborne pollen simultaneously. We determined the standard extract window to be used for estimating the concentration of all types of airborne pollen together. A field experiment was performed to evaluate the automated monitoring system with the standard extract window. The estimated temporal variation pattern of the total airborne pollen concentration agreed well with the observed temporal variation pattern for the whole pollen season. The pollen monitor was able to estimate the overall features of seasonal changes in the total airborne pollen concentration.

Effects of different application timings of methane fermentation digested liquid to paddy plots on soil nitrogen and rice yield

Treatment of animal and food wastes using a methane fermentation technique is drawing considerable public attention as a suitable option for the utilization of biomass resources. The application of a fermentation byproduct (methane fermentation digested liquid) as an agricultural fertilizer has been investigated. Determining the appropriate timing required for applying digested liquid on a rice (Oryza sativa L.) paddy plot is important. The concentrations of soil nitrogen (N) components and rice yield should be considered because digested liquid contains both inorganic and organic N. This study compares the N transformation and the rice yield and growth at different application times over a period of 3 y. The effects of the timing of basal application on soil N were different and the timing that maximized the rice yield was different in each year. Days before ponding (DBP) affected soil N before mid-summer drainage, and rice growth rates at the panicle formation stage and the ear emergence stage. The effects of DBP disappeared before harvest. The results indicated that sufficient potentially mineralizable N existed regardless of DBP, and the effect of DBP lessened after the mid-summer drainage, which coincides with the period when N uptake is most active.

Pollen Dispersal and Hybridization Model for Risk Assessment of Genetically Modified Crops

In recent years, an attention to the gene flow problem of dispersal of artificially modified genes to the natural environment by airborne pollen is increasing rapidly. Especially for wind-pollinated crop, there is a possibility that pollen diffuses quite widely depending on meteorological conditions. In order to deal with such problems, it is necessary to develop the model that can estimate the pollen dispersal and the hybridization mating appropriately. In this paper, I present an aerobiological mechanistic model for assessing pollen dispersal and hybridization using hourly data. This model considers hourly change of the meteorological conditions and daily change of biological conditions. And it was constructed for estimating the spatial distribution of hybridization percentage in a recipient field. The effectiveness of the model was certified by the field experiments. The model was constructed in consideration of physical processes and biological processes. The algorithms presented here can be applied to estimate the total pollen deposition and hybridization mating for many kinds of plants.

Three-dimensional prediction of maize pollen dispersal and cross-pollination, and the effects of windbreaks

With the extensive adoption of transgenic crops, an understanding of transgene flow is essential to manage gene flow to non-GM crops. Thus, a flexible and accurate numerical model is required to assess gene flow through pollen dispersal. A three-dimensional atmospheric model combined with a diffusion transport model would be a useful tool for predicting pollen dispersal since it would be flexible enough to incorporate the effects of factors such as the spatial arrangement of crop combinations, land use, topography, windbreaks, and buildings. We applied such a model to field measurements of gene flow between two adjacent maize (Zea mays) cultivars, with suppression effects due to windbreaks, in an experimental cornfield in Japan. This combined model reproduced the measured cross-pollination distribution quite well in the case of maize plots with plant windbreaks slightly taller than the maize and without windbreaks, but the model underestimated the effect of a 6-m-tall windbreak net beyond 25 m from the donor pollen source on cross-pollination. The underestimation was most probably due to the problem of assimilated wind data. The model showed that the 6-m-tall windbreak and the plant wind break suppressed average cross-pollination rate by about 60% and 30%, respectively. Half-tall and coarser mesh windbreak net suppressed cross-pollination rates by 40% by reducing the swirl of donor pollen by reduced wind speed.

Modelling of Pollen Emission Process for Dispersal Simulation of Birch Pollen

The number of patients of pollinosis caused by airborne pollen is increasing rapidly in the world. From a global perspective, pollinosis from birch is a serious problem in Europe, North America, and Northeast Asia. Our aim in this research is to generalize the principle of our pollen emission model developed for cedar. We observed temporal variations in airborne pollen concentrations of birch in Hokkaido, Japan, by using a Hirst-type pollen sampler. Relationship between airborne birch pollen and meteorological conditions during the main dispersal period was analyzed. Our results indicate that airborne pollen concentrations are related to changes in air temperature and solar radiation. The derivative of air temperature is most important and effective factor than the air temperature itself. The air temperature change for shorter time was related to the pollen emission of birch compared with the case of cedar. The amount of birch pollen emitted from the flowering birch forest was formulated using the algorithm summarized from the analysis.

Estimation of the Release Time of Radio-Tellurium During the Fukushima Daiichi Nuclear Power Plant Accident and Its Relationship to Individual Plant Events

Abstract A simulation model was developed to estimate the areal (surface) deposition pattern of 129mTe after the Fukushima Daiichi nuclear power plant (FDNPP) accident. Using this model, the timing and intensity of the 129mTe release were reverse estimated from the environmental monitoring data. Validation using 137Cs data showed that the model simulated atmospheric dispersion and estimated surface deposition with relatively high accuracy. The estimated surface deposition pattern of 129mTe was consistent with the actual measured pattern. The estimated time and activity of 129mTe emissions indicated that 129mTe was predominantly emitted from FDNPP Unit 3.

Enrichment of airborne Japanese cedar ( Cryptomeria japonica ) pollen in mountain ranges when passing through a front accompanying temperate low pressure

Values obtained by the real-time pollen monitors set up at 14 measuring points in the Tohoku region indicate that a large amount of Japanese cedar pollen was dispersed along the western region and northern flank of the Ou Mountain Range when a front accompanying the temperate low pressures passed through the west sea of northern Hokkaido. We are sure that this phenomenon is related to pollen enrichment by mountain ranges. The time at which highest concentrations of pollen grains were observed shifted from the western to the eastern side, in accordance with the path of the front. No pollen was seen after the passage of the cold front.

Impact of Global Warming on the Regional Climate Adjacent to the Great Lake Biwa

We tried to simulate local climatic elements (temperature, wind speed and wind direction) in a lake watershed by using the turbulence closure model. The study site is Lake Biwa watershed, which is the largest lake in Japan and the most important water resource for 12 million people in Kinki region including Osaka and Kyoto Prefectures. The lake watershed is surrounded by mountains and covered mainly by lake, forest, and paddy field. Then, we conducted scenario analysis of global warming by rising the surface temperature of the lake according to IPCC reports and estimated the impact of global warming on the regional climate adjacent to the great Lake Biwa. In addition, we selected some local areas, which are typical land use, in the watershed and conducted sensitivity analysis for global warming in the local areas. The effect of global warming on the lake watershed appears clearer in the daytime, when wind speed in the upper boundary is higher. In this case, the energy from the great lake may be rapidly distributed to the surrounding region.