In order to find practical strategy for controlling eutrophication in Lake Taihu, in this study, water quality and biota were investigated in East Lake Taihu, Meiliang Bay and West Lakeshore. Compared with the lower nutrients concentrations in East Lake Taihu, the values of Chl.a, turbidity, T-N and T-P showed significant fluctuations with eutrophication level in different places of Meiliang Bay and West Lakeshore. There was significant positive correlation among each value of Chl.a, T-N and T-P in Meiliang Bay, which indicated that the occurrence of water bloom was related to the concentration of nutrient. According to the result of identification, there were totally twelve species of aquatic macrophytes in the investigated area, of which two species were found in Meiliang Bay, one species was found in the southwest coastal zone, and twelve species were found in East Lake Taihu including six species as dominant submerged plants. There were ten species of Cyanophyta during the water bloom in East Lake Taihu and Meiliang Bay, of which Microcystis aeruginosa was found with large quantities of biomass as dominant species. Apart from the Cyannophyta, 21 species of diatom and 20 species of Chlorophyta were identified in East Lake Taihu and Meiliang Bay, of which 41 species were spread in East Lake Taihu. The relatively richer macrophytes community and phytoplankton indicated the higher biodiversity conditions in East Lake Taihu.

View full abstract

 Risk assessment of soil contaminated with radionuclides was performed by considering the intake of radionuclides in foods based on measured concentrations. Due to the disaster at the Fukushima nuclear power plant on March 11, 2011, radionuclides were spread out. The radionuclides were found in the food, and the Japanese people are concerned about eating foods from Fukushima and the surrounding area. Radionuclides such as ¹³⁴Cs and ¹³⁷Cs were found on soil, buildings, plants, and so on. The exposure routes were determined to be food intake, ingestion and inhalation of soil particles, and external radiation from the ground. Then, the total doses of all exposure routes for one year were calculated, and the committed effective doses for the lifetime were evaluated. As a result, exposures by ingestion and inhalation of soil particles were negligible, and exposure by food intake and external exposure from the ground were comparatively large. This study shows that the air dose by this disaster should be less than 0.2 μSv/h to control the radiation dose with the consumption of food being less than 1 mSv/y. The risk assessment based on land use can provide information about the priority of countermeasures against the contamination and provides reasonable decontamination methods or risk management strategies.

View full abstract

 The analysis on waste set-out behavior and the unit amount distribution of waste was conducted for municipal combustible waste at one district in Fukuoka city, Japan, both in spring and summer season. As a result, most households decided the capacity of waste bag in advance based on the long time experience. And the seasonal variation on waste set-outs mainly depended on the distribution of the unit amount of waste, which meant that it was possible that some combinations between such distribution of the unit amount of waste and the set up capacities of waste bag would cause the dramatic variation between the different seasons.

View full abstract

 Field investigation in Fukushima showed that mobility of radioactive cesium was low in soil, and wetdry cycle experiment showed that quantity of bioavailable radioactive cesium in soil decreased with time. Convection-dispersion equation and point attenuation kernel integration method are used for modeling the secular change of air dose rate caused by radioactive cesium in soil. Here, two-step variation model of distribution coefficient for radioactive cesium in soil could well explain its distribution profile in depth and change of monitored air dose rate. This model showed that air dose rate at urban flat area in August of 2011 would decrease to less than half in two years and that of 1μSv/h would decrease to 0.19μSv/h before 10 years have passed. It was also showed that weeding didn't have significant effect to air dose rate.

View full abstract

 A bioaccumulation model of persistent organic pollutants (POPs) in bivalves was developed, in which the exposure routes from water and suspended solid are separated, and the growth of bivalves is incorporated. Constants in the model were calculated with results from the indoor exposure experiment with Corbicula japonica. It was suggested that rate constant of POP loss would mainly control the bioaccumulation factor because absorption efficiency of each OCPs from water was almost 1. It was cleared that bioaccumulation factor of chemicals whose logKow is approximately 6 decreased by a digit with the increase of concentrations of suspended solid from 1.20 mgC/L to 8.52 mgC/L. The applicability of the model to the environment was suggested, because the model replicated the change of OCP concentrations in Corbicula in the environment. In addition, the growth of Mytilus galloprovincialis and growth disruptance due to the high and low water temperature in summer and winter were simulated well. By comparing the results from a previous study, the validity of the model was indicated.

View full abstract