The cladoceran Daphniamagna has been used as an aquatic test species in aquatic toxicology. To evaluate the aquatic toxicity of leachate from concrete, the immobilization of D. magna was observed after treatment of various concentrations of leachate specimens. Reliabilities of the culture condition and the experimental protocol for acute toxicity test were successfully achieved from the standard toxicity test. The leachates were prepared from the mixture of Ordinary Portland Cement (OPC) and pozzolanic admixtures, Pulverised fuel ash (PFA), Ground granulated blast furnace slag (GGBS) and GGBS containing loess. Acute toxicity test showed 100% immobilization of D. magna for OPC or PFA. The leachates from OPC or PFA had high pH 10 to 12. However, GGBS and GGBS containing loess showed less toxicity according to the concentrations. Especially, immobilization was not observed at the concentrations below 12.5% of GGBS containing loess. Also the range of pH for these specimens was 8 to 9. This suggested that the use of loess as the admixture in concrete may be useful to reduce eco-toxicity of leachates from concrete. This our study provided the harmfulness of the alkali leaching from concrete in aquatic environment and the usefulness of D. magna to evaluate the toxicity of leachates from concrete.
The detection and presence of toxic materials in environment is one of the most popular interests because of their harmful effects on ecosystem including human. Especially, the presence of toxic materials in aquatic environment is more considerable to evaluate the harmfulness. The evaluation of contamination in aquatic environment has been for a long time performed only by specific chemical analyses, but many experiences and studies have shown the inadequacy of such approach. To complement this chemical analysis, the biological methods using fish or algae have been used to evaluate and monitor the water quality for many years (Sandbacka
The
The concrete is composed of primarily of cement, aggregate, and water and is widely used for making architectural structures, foundations, walls, bridges, dams and etc. Especially, the cement, commonly Portland cement, serves as a solidified and hardened into rock-hard strength through a chemical process. Concern about the environmental impacts of cementbased materials has been grow consistently now (Dell'Orso
The purpose of this study, therefore, was to evaluate the usage of eco-toxicity assays with
[Table 1.] Preparation of synthetic freshwater using reagent grade chemicals
Preparation of synthetic freshwater using reagent grade chemicals
[Table 2.] Culture conditions for D. magna
Culture conditions for D. magna
Corporation (KEC), Korea, and maintained in laboratory by the standard culturing method suggested by KEC (Table 1) (KEC). The synthetic hard water for culture was manufactured as Table 2.
The alkali leaching specimen was prepared from the mixture of Ordinary Portland Cement (OPC) and pozzolanic admixture. The specimens were made with not only cement and water but also the admixture instead of cement. The ratio of cement to water was 10:3, 10:4 and 10:5, respectively. The admixture replacement percentage were followed in the 10:4 ratio of cement to water; 30% Pulverised fuel ash (PFA), 60% Ground granulated blast furnace slag (GGBS) and 60% GGBS containing loess, respectively. Each specimen was treated to the sealed container filled with water for 30 days, and then the leachate was prepared from it.
As a means of controlling the sensitivity of
All experiments were carried out with brood neonates (< 24 hrs old). Twenty
To evaluate the reliability of the experimental protocol for acute toxicity test, the standard toxicity test was carried out using potassium dichromate. As the result, EC50 value was 1.01 mg/L at 24 hrs of exposure (Fig. 1). This value belonged to normal range (0.9~2.1 mg/L)
of standard toxicity test using
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Immobilization of D. magna by alkali leachate from concrete
The effect of alkali leachate from various kind
[Table 3.] Acute toxicity test of alkali leachates using D. magna.
Acute toxicity test of alkali leachates using D. magna.
of concrete to
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Acute toxicity of alkali leachates from concretes
From the preceding results, 24h-EC50 value and TU were calculated (Table 3). We could not determine any value of 24h-EC50 value and TU for the leachates from OPC only or replacement with PFA 30% because of their high toxicity. The replacement with GGBS 60%, on the other hand, showed 17.67 TU and the addition of loess, especially, reduced TU significantly to 2.04.
The amount of leaching from concrete used in this study may be much more than that from natural condition because the less water used to leach from concrete in this study. However, 100% immobilization in all concentrations of OPC or PFA 30% suggested that the effects of leachates from concrete in natural condition may be significant in aquatic environment. The strength of concrete is determined generally by the rate of cement to water. Therefore, the use of higher amount of cement in mixture is the basic essential to satisfy strength of concrete. Acute test showed significantly high toxicity to
In conclusion, this study provided the harmfulness of the alkali leaching from concrete in aquatic environment and the usefulness of