The amounts of dioxins (PCDD/Fs) and dioxin-like PCBs transported by rivers from various sources to Tokyo Bay were estimated. River water samples were collected at six stations in six different rivers (Edo River, Naka River, Ara River, Sumida River, Tama River and Tsurumi River) from April 2001 to July 2003, and the concentrations of PCDD/Fs and dioxin-like PCBs in these rivers were determined. On the basis of these results, the annual amounts of PCDD/Fs and dioxin-like PCBs transported by each river to Tokyo Bay were estimated. It was estimated that 10 g-TEQ (particulate phase) and 2.3 g-TEQ (dissolved phase) were transported to Tokyo Bay annually in recent years. Also, the contributions of sources of PCDD/Fs and dioxin-like PCBs in these rivers were estimated by a chemical mass balance (CMB) approach. In Tama and Tsurumi Rivers, it was estimated that more than 85% of total TEQ originated from combustion, while the contribution of combustion was less than 60% in the Ara River. Moreover, the amounts of PCDD/Fs and dioxin-like PCBs transported from each source were estimated, assuming that the contributions of sources in a river are constant in recent years. It was estimated that 8.4 g-TEQ, 1.1 g-TEQ, 0.45 g-TEQ, 1.2 g-TEQ originating from combustion, PCP, CNP and commercial PCBs, respectively, were transported to Tokyo Bay annually.
The influence of substrate concentration and pH on hydrogen fermentation of a mixed substrate by a mixed microflora was investigated using a batch experiment. The batch reactor with a working volume of 1.0 liter was operated at 35°C at a constant pH for each experimental run. Dog food was used as the substrate. The seed microflora was a mixed culture having Clostridium pasteurianum and Sporolactobacillus racemicus M116. It was obtained by acclimatizing a thermophiledigested sludge using glucose as the substrate. The experiments were conducted by changing the pH from 4.0 to 7.5 at various substrate concentrations of TS2%, TS5%, and TS10% to evaluate substrate decomposition, gas production and metabolic production under each condition. Hydrogen fermentation was greatly affected by pH at each TS concentration and the optimal pHs for obtaining maximum hydrogen yield were identified to be 4.5-5.5 for TS2%, 5.5 for TS5% and 6.5 for TS10%. The maximum hydrogen productions at TS2%, TS5% and TS10% ranged from 93.9 to 108 ml·g-1 VS, and no significant influence caused by the substrate TS concentration was noted. These results indicate that hydrogen fermentation can be effectively operated under a high-substrate condition as well as at TS10% by maintaining an optimum pH. The H2 yield at the optimal pH was as high as 1.80 mol H2·mol-1 glucose. Lactic acid was the main product at a low pH, while a complex fermentation pattern was obtained at a pH close to 7.0. Both these fermentation patterns resulted in a decrease in H2 production.
The dechlorination reaction of an aqueous solution of trichloroethylene (TCE) with α-Fe·Fe3O4 composite particles which included 500-4500 ppm sulfur was carried out using shaking and stationary methods. As a result, the following reaction mechanism was obtained. cis-1,2-dichloroethylene (DCE) was produced as the intermediate product at the first step of the dechlorination of TCE, and cis-1,2-DCE was converted into four types of sulfonated hydrocarbon through the reaction. Such a substitution of Cl in cis-1,2-DCE to S proceeded catalytically at the surface of magnetite including in composite particles and S atoms only acted as the promoter of dechlorination without the formation of hydrogen sulfide. These sulfonated hydrocarbons converted to seven types of hydrocarbon as the main products by the successive reactions.
The decomposition of humic acid on the Pt/Ti and SnO2/Ti electrodes was investigated by measuring the total organic carbon (TOC) and UV-visible spectrum. The results showed that humic acid could be decomposed electrochemically and the efficiency in the decomposition of humic acid on the SnO2/Ti electrode was higher than that on the Pt/Ti electrode. The effects of different types of supporting electrolyte, their concentrations and the initial concentration of humic acid on the electrochemical decomposition of humic acid were investigated. Na2SO4 was found to be a suitable supporting electrolyte and the decomposition of humic acid was achieved efficiently at low electrolyte concentration.
Agriculture is multifunctional, and the value of each function should be expressed in a form that is easy for anyone to understand. One function, for example, is water purification, and recently much effort has been expended to quantify this function. We proposed a new replacement cost method to perform an economic valuation of the nitrogen (N) removal function of paddy fields and of the N load function of upland fields, as well as economically valuated cultivated lands in Japan. The N removal function was valued at approximately 0.3 JPY·m-2·d-1 when compared with the maintenance and depreciation cost of water quality improvement facilities. Upland fields have a negative economic value of approximately 0.08 JPY·m-2·d-1. However, paddy fields function effectively in N removal only when irrigation water is strongly contaminated with N. Consequently, 90% and more of the area used for paddy fields do not function in N removal. Based on these valuations, cultivated lands including paddy fields and upland fields could be annually valuated at minus 780×109 JPY Japan-wide.