We measured O₂ consumption and CO₂ production by benthic respiration to examine the characteristics of organic matter metabolism in tidal flat sediments (A-C) of three different types in the northern part of Hiroshima Bay.
Benthic respirations were in the range of 0.196-4.07g-O₂·m^-2·d^-1 (0.046-1.98g-C·m^-2·d^-1), 0.620-5.60g-0₂·m^-2·d^-1 (0.247-2.08g-C·m^-2·d^-1), 0.3l9-2.23g-0₂·m^-2·d^-1 (0.105-0.804g-C·m^-2·d^-1) in A, B and C, respectively.
Each tidal flat showed the highest respiration activity at high temperature in summer season, and almost same activity at same temperature in spite of different season, organic matter content and bacterial number in the sediment. From these results, it's considered to be temperature that has a most important effect on the benthic respiration activity in tidal flat. We examined temperature coefficient for the respiration by changing temperature into 5 stages of 5-40°C, and obtained Q₁₀=2.75 and 2.39 in Band C, respectively.
Though the benthic respiration quatient (RQ) showed variations, the values yielded an annual total RQ of 1.04 in these three tidal sediments. We also estimated the ratios of macrobenthos respiration measured directly in the laboratory to total benthic respiration of tidal flats, and got the value of 3.4-100%, 14-65% and 3.7-40% in each tidal flat A, B and C.

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Two phenanthrene degrading bacteria were isolated from soil and identified as Burkholderia sp. strain PHN-5 and N372B. Strain N372B degraded phenanthrene rapidly in mineral salts medium without accumulation of 1-hydroxy-2-naphthoic acid and intermediate products. The phenanthrene degradation pathway by the strain N372B seemed to be in which phenanthrene was first converted to 1-hydroxy-2-naphthoic acid, 2-carboxybenzaldehyde and o-phthalic acid. Strain PHN-5 (did degrade phenanthrene, but with some accumulation of 1-hydroxy-2-naphthoic acid. This strain could not oxidize 1-hydroxy-2-naphthoic acid.
Both of these two Burkholderia strains also degraded a variety of polycyclic aromatic hydrocarbons. Strain PHN-5 had wider specificity than strain N372B. The enzymes which degraded 1-hydroxy-2-naphthoic acid to o-phthalic acid in strain N372B cells required NAD⁺ and Ferrous ion as their cofactors. On the other hand, the corresponding enzymes were not observed in strain PHN-5.

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The production and release of microcystins during the batch culture of Microcystis aeruginosa LERL 031 which was isolated from Korean freshwater were investigated. Total amounts of two major toxins (microcystin-RR and -LR) did not decrease at the death phase of the culture while chlorophyll-a concentration decreased. The ratio of two major intracellular microcystin amounts of the cyanobacteria was changed depending on the growth phase.
The grazing effects on Microcystis biomass and microcystins by micrometazoa and protozoan which were isolated from biofilm oxidation reactor were examined. Among three microanimals Monas guttula was turned out to be the most effective grazer of M. aeruginosa LERL-031. In the condition of coexistence of Aeolosoma hemprichi, Philodina erythrophthalma, Monas guttula in the cyano-bacterial as grazer, chlorophyll-a concentration decreased by 73% of initial concentration after 31 days. In the condition of no addition of microanimals, intracellular microcystins were released to surrounding water during the lysis of cells but not degraded.

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Optimal hydrogen peroxide dose for ozone/hydrogen peroxide (0₃/H₂O₂) process was investigated based on the difference of the reactivity of target compounds (i. e., malonate and oxalate ions) with hydroxyl radical (HO·) and their initial concentration (i. e., 0.05 and 0.50 mM). All experiments were conducted at pH7.5 and ozone dose was 0.021 mM·min^-1. The optimal H₂O₂ doses at which the decomposition ratio of these target compounds becomes maximum with the reaction time of five and ten minutes existed in the range of 0.025-0.14 mM. At five minute reaction time, the optimal H₂O₂ dose for malonate ion, highly reactive compound with HO·, was greater than that for oxalate ion, lowly reactive compound with HO·. On the other hand, the optimal H₂O₂ dose became more dependent on the time-course of H₂O₂ concentration in the process at ten minute reaction time. Especially, in the case of oxalate ion, the optimal H₂O₂ dose greatly increased with the elapse of time. Bicarbonate ion not only prevented the decomposition of target compounds but also enhanced the decrease of H₂O₂ concentration. Also, the optimal H₂O₂ dose increased with the increase of initial bicarbonate ion concentration.

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Soil and ground aquifer contamination caused by aliphatic volatile organochlorine compounds, such as trichloroethylene and tetrachloroethylene etc., has made it necessary to determine soil contents. An application method of supercritical fluid extraction was therefore developed to extract the compounds from contaminated soil matrices.
The method for collecting extracted materials was investigated from the viewpoint of minimizing collection loss. The collection train composed of two impingers that contain n-hexane and 5 % n-decane and cooled by an ice bath with salt was enough to collect the major compounds targeted.
The extractability of target compounds was found to mostly depend on temperatures. The extracted amounts at 150 °C increased with an increase in temperature from 50 °C. On the other hand, pressure and the addition of a modifier did not affect the extractability.

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A technique is considered and tested for quick measurement of DO concentration in a large water body where the concentration varies in time and space: Commercial DO meters for field measurements usually take tens seconds to output a value with enough accuracy at one measurement point because of their tardy response. However, when the response characteristics are expressed by some mathematical equation which relates the inputted (real) signal to the outputted signal, it is possible to deduce a spatial distribution of DO concentration from a continuously outputted signal obtained by moving the meter in a water, and then the time for measurement can be remarkably reduced. In this study, this idea is realized by assuming the characteristic equation as a first order differential equation. Field experiments show that the deduced DO profiles satisfactorily agree with the profiles obtained from the ordinary measurement.

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