Urban areas are undergoing a relative increase in non-point loads from road surfaces and rooftops. Manufacturing activities and motor vehicles produce exhaust gases containing micro-pollutants that are considered to adversely affect human beings and river ecosystems. These toxic substances accumulate on road surfaces on fair days and run off into river systems in the form of roadway drainage on rainy days. In this study, we measured the content of benzo(a)pyrene (B(a)P), which is a carcinogen in road-surface sediments, and experimentally quantified the rate of photolysis of B(a)P , in order to develop a prediction model to estimate B(a)P road-surface sediment and runoff loads. The characteristics (such as pollution load generation, distribution and attenuation) of B(a)P road-surface sediment loads were clarified, and a method was developed to identify parameters for a model to predict these loads. The findings of this study will enable more quantitative predictions to be made concerning B(a)P road-surface sediment and runoff loads, which will help provide greater accuracy when countermeasures and the control of non-point loads will be considered in the future.

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An investigation on the seasonal change and removal of estrogen in a swine wastewater treatment plant was carried out from July 2004 to September 2005. Natural estrogens (estrone, estradiol and estriol) in raw wastewater showed similar seasonal changes and their peak values reached 162, 872, 4,480 ng · l^-1, respectively, whereas equol showed a different trend in which the maximum concentration was markedly high at 43,300 ng · l^-1. The results showed that approximately 93% of the total estrogenicity in raw wastewater was attributed to equol. The sequencing batch reactor (SBR) process of the swine wastewater treatment plant was efficient to remove selected estrogens for quantitative analysis as well as nitrogen and phosphate. Moer than 99% removal efficiencies for all selected estrogens and total estrogenicity were attained by the SBR process. The total estrogenicity that remained after the SBR process was, however, still higher than the predicted noneffective concentration level for fish (PNEC). It was found that a baffle channel located at the final stage of the treatment flow contributed to decreasing the estrogenicity to the PNEC level. Experimental results in the laboratory showed that filamentous algae inhabiting the bottom of the channel were responsible for the estrogenicity decrease observed in the baffle channel.

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To evaluate the transport and accumulation of suspended particles from the rivers in Ariake Bay basin, we simulated the movement of particles discharged from the main rivers and Isahaya Reservoir using a three-dimensional flow model and the Euler-Lagrange method. This model was able to quantitatively estimate the spatio-temporal behavior of particles during the process of accumulation on the sea bottom and the subsequent resuspension in water columns. Hereafter, we will attempt to validate this model with a collection of real data from each of the locations that was simulated, while also estimating the contribution of particles from each source into the bay. Furthermore, this simulation model could be useful for predicting the movement of plankton during red tides, as well as the journey of pelagic bivalve larvae.

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