A personal computer-based COD model was developed in order to make eutrophication programs effective for Toyano Lagoon which has a short retention time (1.8 days) and is a shallow and eutrophic lake. Toyano Lagoon is mainly used for irrigation water through the pumping stations at the inlet and outlet where connect Kurinoki River and Shinano River, respectively. This means that flow control such as dilution and discharging at pumping stations is feasible as eutrophication control.
First the model was calibrated using observed data in 1988 FY. Then the calibrated model was verified by observed data in 1985 FY (i.e., before eutrophication control measures). The sensitivity analysis for parameters and forcing functions and water pollution analysis were performed using the verified model. It was found in both the calculated values and the observed data that COD concentrations increased steeply in April, July and September when the inflow and outflow decreased. The model calculations showed that the increase of autochthonous COD due to primary production corresponds to the peak of COD concentrations in these months. The production rate of autochthonous COD and the external COD loading rate are 228 t·y^-1 and 1,946 t·y^-1, respectively. The control of inflow and outflow being increased by 150% and kept constant is very effective for prevention of the peak of autochthonous COD, though reduction control of external nutrient load not. The COD concentration in Toyano Lagoon decreases by about 1.5g·m^-3 per 1,000kg·d^-1 reduction of the external COD load.

View full abstract

We constructed a numerical model that simulates a finite system where solute transport and denitrification and isotope fractionation associated with denitrification simultaneously occur. We described the system simply as one dimensional convective-dispersive equation with reaction in finite length, solved the equations numerically by FDM, and examined the effect of dispersion on the change of solute concentration and isotope ratio through the system.
As Peclet number decreases and as the unreacted fraction of nitrate decreases, the relationship between the unreacted fraction and delta-15 value of effluent diverts from the relationship without the effect of solute transport, and the apparent fractionation factor diverts from the true one. The ratio of apparent to true (per mill) enrichment factors decreases as dimensionless reaction rate constant κ_14N increases and Peclet number Pe decreases, not the ratio κ_14N/Pe but both κ_14N and Pe affect the ratio of apparent to true (per mill) enrichment factors, in this point, the apparent fractionation factor calculated by this finite system differs from that calculated from solute and isotope ratio distributions in the semi-infinite system.

View full abstract

Fulvic acid extracted from lake sediments was treated with Amberlite XAD-2 and XAD-8 resins. The metal complexing ability of the fulvic acid was measured at pH 6.0 with a Cu²⁺ titration method, in which free Cu²⁺ was determined with an ion selective electrode. A two binding site model, in which there are two kinds of the molecules having strong and weak complexing ability and they complex with metal ion at the ratio of 1 : 1, was employed for the determination of the stability constant and complexing capacity of the fulvic acid, because the hyperbolic approxmation could apply to the Scatchard plot of the found values.
The stability constants of the fulvic acids having strong complexing ability and weak complexing ability were in the range of 6.33-7.12 and 4.35-4.66, respectively. Both colorless fractions of the fulvic acid which were not adsorbed on XAD-2 and XAD-8 resins had such a high complexing ability as 44 and 32 μmol·g^-1, respectively.
On the other hand, both colored fractions of the fulvic acid which were adsobed on the resins had only little complexing capacity.

View full abstract

Field observations were carried out to clarify the structure of water quality in a reservoir with dicho-thermal stratification. Measurements were made for the vertical profiles of water temperature, dissolved oxygen, electric conductivity, iron and manganese in a reservoir of Shimajigawa-Dam in Yamaguchi Prefecture. In this reservoir, dicho-thermal stratification frequently occurred during the period from April 1987 to March 1990. The maximum thickness of the layer of dicho-thermal stratification reached about 40 m, and the maximum range of the temperature variation in this layer reached about 2 degrees. Thickness of the anoxic layer where the dissolved oxygen was lower than 10% of the saturate value ranged from 20 m to 40 m. When the dicho-thermal stratification occurs, vertical density structure should be estimated by considering the water temperature, salinity and pressure, i.e. depth. Manganese and iron showed high concentration in the layer of dicho-thermal stratification. This feature seems to reflect the biochemical action in this region. Results of water quality analyses imply that the behavior of the water in the dicho-thermal stratification influences the quality of whole water in a reservoir, and that manganese, iron and electric conductivity are useful indices of the behavior of the reservoir with dicho-thermal stratification.

View full abstract

To assess the effects of pesticides sprayed in golf links on growth of algae population in aquatic environment, toxicity of some pesticides was assayed by 72 hours-algal growth inhibition test. A green algae Selenastrum capricornulum was used for the assay, since it is one of typical algal species in the assay. Of twelve chemicals tested, oxine-copper, butamifos and pendimethalin exhibited a pronounced toxic action on the algae, and reduced the growth of the algae at the concentration below 0.1 mg·l^-1. However, with diazinon, trichlorfon, flutoluanil and mecoprop formulation, the concentrations of these chemicals which results in a 50% reduction of growth (EC₅₀) were over 10mg·l^-1. The EC₅₀ values of some herbicides and fungicides were lower than the current effluent guide line values for golf links. It suggests that the guide line value should not appropriate for conservation of aquatic ecosystem. It is noticeable that positive correlation was observed between the values of EC₅₀ and water solubility for the chemicals tested.

View full abstract

A method for predicting the change of COD of lake water in response to the reduction of phosphorus loading was newly developed because the existing methods for the purpose are considered inappropriate for application to unusual type of waters like a very shallow water. The method is based on an analysis of the current state of the phosphorus cycling in the specific lake and a diagrammatic expression of every flux and stock of the organic and the inorganic phosphorus considering the production and decomposition of organic matter and the release and settling of phosphorus in the take. This analysis needs extensive field observation. Once it is established, the change of organic phosphorus concentration in response to the change of total phosphorus loading can be predicted by making a simple and appropriate assumption on the change of the related processes in the cycle. When the change of organic phosphorus concentration is predicted, the change of COD can be predicted by utilizing a statistical relation between the organic phosphorus and the COD of water. The relation was found to be simple and reliable in our case. The new method was applied to Lake Teganuma and the result was compared with the results of existing methods.

View full abstract

Multiplication characteristics of FRNA phage was studied. Using FRNA phage Qβ and Escherichia coli K12 A/λ (F⁺), concentration of host bacteria and FRNA phages in constant temperature incubation was measured after certain time intervals. FRNA phage inoculated in host culture growing exponentially multiplied while inoculated in host culture in steady state phase didn't multiply. Higher yield of FRNA phage was obtained when incubated in higher substrate concentration. Incubation temperature greatly affected FRNA phage multiplication. In 35°C and 30°C condition FRNA phage multiplied. But decrease of the incubation temperature resulted in decrease of FRNA phage production and finally in 25°C condition FRNA phage didn't multiply. On the other hand, multiplication of DNA phage obtained from an urban river on E. coli C plate was not affected by the temperature. Incubation of sewage sample showed the same tendency of multiplication potential that DNA phages were easy to grow but FRNA phages were not. When we consider adopting phage as an indicator for pathogenic virus, E. coli KI2A/λ (F⁺) seems more reasonable as a host strain because it can detect FRNA phage, than E. coli C which detects DNA phage easily multipliable in the environment.

View full abstract

The effect of the diffusive boundary layer on the sediment oxygen demand (SOD) is investigated theoretically. The oxygen consumption in the sediment is modeled to consist of the bacterial and the chemical consunmptions. Each reaction rate is formulated by the Michaelis-Menten and the first-order reaction kinetics of dissolved oxygen concentration, respectively. The effect of flow velocity is expressed in terms of a non-dimensional velocity, U_*. This model suggests that, at very low flow velocity (U_* < 1), the SOD is completely determined by the transport through the diffusive boundary layer and can simply be expressed as functions of the velocity, DO concentration in the bulk water and a friction coefficient. At higher velocity, the transport is so fast that the processes in the sediment become rate limiting. The velocity dependence of SOD through the boundary layer thickness agrees with observations by former researchers. Predicted profiles of DO concentration in the boundary layer and in the sediment reproduce the observed profiles using microelectrodes. The model also includes a dependence between the bulk DO concentration in the water and SOD. Effect of the vertical distribution of reactive organic carbon on the dependence is also discussed.

View full abstract

Biodegradation of tetrachloroethylene (PCE) to trichloroethylene (TCE) and successively to cis-1, 2-dichloroethylene (cis-DCE) under an anaerobic condition could be well approximated by a consecutive first-order reaction model.
PCE → k₁ TCE → k₂ cis-DCE
The theory has a rule that the models with the same ratio of kinetic constants k₂/k₁ show a similar time-concentration profile even if the scales of time-axis are different. This rule enables us to estimate the ratio of kinetic constants in contaminated groundwater from the observed values of the concentrations of the above three compounds. Then we can analyze the present state of the degree of degradation and evaluate the behavior of the three compounds in future.

View full abstract

Enzyme immunoassay was applied to the analysis of pesticide and herbicides as an alternative to the expensive and time-consuming chromatographic techniques. Antibodies against asulam, simazine, and thiram were successfully prepared and submitted to their quantitative determination with conventional ELISA. Results showed good quantitivity of immunoassay and feasibility of applying the method to field monitoring.

View full abstract

In order to clarify the mechanism of water pollution in a river, the River Ohtsu and the River Shinkawa were chosen and the changes of concentrations and components of the dissolved organic substances were investigated.
Water was sampled once a week from June 1984 to August 1987. Each water sample was filtered through a 0.45 μm membrane filter and used for the determination of the concentrations of dissolved organic substances.
The concentration ranges of dissolved TOC in samples collected from the River Ohtsu and the River Shinkawa during the experimental term were 8.6-16.6mg·l^-1 and 5.7-8.3mg·l^-1, respectively. In the summer season, the dissolved TOC in the River Ohtsu was composed of proteins, 14-18% ; carbohydrates, 16-19% ; volatile organic acids, 2-6% ; anion surfactants, 5-9% ; humic acids, 4-6% ; lignin, 2-4% and urea, 1-2%.
The concentration ratios of each component in the samples from the River Ohtsu, which catches the wastewater from its urbanized catchment area, were very similar to those of the municipal wastewater. In case of the River Ohtsu, therefore, the contamination by wastewater from its catchment area is thought to be a major cause of the pollution. On the other hand, as one of the cause of the pollution of the River Shinkawa, the influx of the organic substances from the domestic wastewater may contribute greatly.

View full abstract