Takehide Hama

Nitrogen removal properties in a continuous marine anammox bacteria reactor under rapid and extensive salinity changes.

Salinity tolerance is one of the most important factors for the application of bioreactors to high-salinity wastewater. Although marine anammox bacteria (MAB) might be expected to tolerate higher salinities than freshwater anammox bacteria, there is little information on the effects of salinity on MAB activity. This study aimed to reveal the nitrogen removal properties in a continuous MAB reactor under conditions of rapid and extensive salinity changes. The reactor demonstrated stable nitrogen removal performance with a removal efficiency of over 85% under salinity conditions ranging from 0 to 50 g/L NaCl. The reactor performance was also well maintained, even though the salinity was rapidly changed from 30 to 50 g/L and from 30 to 0 g/L. Other evidence suggested that the seawater medium used contained components essential for effective MAB performance. Bacterial community analysis using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) showed that planctomycete UKU-1, the dominant MAB species in the inoculum, was the main contributor to anammox activity under all conditions. The PCR-DGGE using a universal bacterial primer set showed different DNA band patterns between the reactor biomass sample collected under conditions of 75 g/L NaCl and all other conditions (0, 30, 50 and freshwater-medium). All DNA sequences determined were very similar to those of bacterial species from marine environments, anaerobic environments, or wastewater-treatment facilities.

Application of a modified conceptual rainfall–runoff model to simulation of groundwater level in an undefined watershed

Groundwater level simulation models can help ensure the proper management and use of urban and rural water supply. In this paper, we propose a groundwater level tank model (GLTM) based on a conceptual rainfall-runoff model (tank model) to simulate fluctuations in groundwater level. The variables used in the simulations consist of daily rainfall and daily groundwater level, which were recorded between April 2011 and March 2015 at two representative observation wells in Kumamoto City, Japan. We determined the best-fit model parameters by root-mean-square error through use of the Shuffled Complex Evolution-University of Arizona algorithm on a simulated data set. Calibration and validation results were evaluated by their coefficients of determination, Nash-Sutcliffe efficiency coefficients, and root-mean-square error values. The GLTM provided accurate results in both the calibration and validation of fluctuations in groundwater level. The split sample test results indicate a good reliability. These results indicate that this model can provide a simple approach to the accurate simulation of groundwater levels.

Nitrogen and phosphorus effluent loads from a paddy-field district adopting collective crop rotation

Japanese paddy rice systems commonly adopt the rotation of vegetables, wheat and soybeans with paddy rice. Crop rotation may, however, increase the nutrient load in effluent discharged from the district because more fertilizer is applied to the rotation crops than is applied to paddy crops. We investigated a paddy-field district subject to collective crop rotation and quantified the annual nutrient load of effluent from the district in three consecutive years. The total annual exports of nitrogen and phosphorus over the investigation period ranged from 30.3 to 40.6 kg N ha(-1) and 2.62 to 3.13 kg P ha(-1). The results suggest that rotation cropping increases the effluent nutrient load because applied fertilizer is converted to nitrate, and surface runoff is increased due to the absence of shuttering boards at the field outlets.

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.

Simplified Lumped Groundwater Model to Simulate Nitrate Concentration Dynamics

AbstractModeling of the nitrate concentration in groundwater can help ensure proper groundwater management and utilization, especially as a drinking water supply. Here, a groundwater nitrate tank m...

Nitrate contamination of groundwater and identification of its cause in Kumamoto City and neighbouring area in Japan

Kumamoto City that has a population of 0.7 million depends on the only groundwater for the drinking-water demand. Recently, there are growing concerns about a groundwater contamination by nitrate. In this study, we aimed to reveal the situation and cause of nitrate contamination of groundwater in Kumamoto City and its neighbouring area by a combination of water-quality measurement and the analysis of public data. Nitrate concentration in the groundwater varied according to the area-location, however, most groundwater samples showed an increasing trend for the last few decades, and high nitrate concentration (>10 mg-N/L) was detected even in deep-aquifer samples. The results of nitrogen stable isotopic analysis suggested that nitrate contamination was caused by organic nitrogen. At the same time, the analysis based on public statistical data demonstrated that the nitrogen load by waste of domestic animals drastically increased for the last decades. These results strongly suggested that the waste of domestic animals was the most significant cause for the groundwater contamination in the research area.

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.