• Journal of Environmental Health Sciences
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• v.35 no.2
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• pp.124-129
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• 2009

The photocatalysis degradation of simazine, s-triazine type herbicide was carried out using circulating photo reactor systems. In order to search for the effective method to mineralize this compound into environmentally compatible products, this study compared the removal efficiencies of simazine by changing various parameters. First, under the photocatalytic condition, simazine was more effectively degraded than by photolysis and $TiO_2$ only condition. With photocatalysis, 5 mg/l simazine was degraded to approximately 90% within 30 min, and completely degraded after 150 min. Ionic byproducts such as ${NO_2}^-$, ${NO_3}^-$, and $Cl^-$ were detected from the photocatalysis of simazine, however, the recoveries were poor, indicating the presence of organic intermediates rather than the mineralization of simazine during photocatalysis. Two bioassays using V. fischeri and D. magna were employed to measure the toxicity reduction in the reaction solutions treated by both photocatalysis and photolysis. Simazine and its photocatalysis treated water did not exert any significant toxicity to V. fischeri, marine bacterium. However, the acute toxicity test using D. magna indicates that initial acute toxicity ($EC_{50}$ = 57.30%) was completely reduced ($EC_{50}$ = 100%) after 150 min under both photocatalysis and photoysis of simazine. This results indicates that photocatalysis and photolysis of simazine reduced the acute toxicity through mineralization.

• Journal of Environmental Health Sciences
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• v.33 no.2 s.95
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• pp.123-131
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• 2007

Many environmental contaminants including several metals, polycyclic aromatic hydrocarbons, and pharmaceuticals, have been identified to be phototoxic in the water environment. Concerns regarding photo-enhancement of toxicity of several environmental contaminants have been increasing because of the increased level of ultraviolet irradiation on the earth surface. However, there exist arguments that there might be certain defense mechanisms taking place in the aquatic ecosystem, which may include behavioral characteristics or genetic acclimation. This study was conducted to understand the potential responses of aquatic receptors to several phototoxic metals in the real environment, where long-term acclimation of such organisms to low dose UV-B may take place. For this purpose, water flea Daphnia magna was acclimated to environmentally relevant dose of UV-B (12 to $18uW/cm^2$) for >11 generations. The differences in developmental and life history characteristics, and toxicity responses were evaluated. Acclimation did not affect the daphnids' growth, longevity, and reproduction characteristics such as time to first brood, and brood size: After 21 d, survival of D. magna was not influenced by UV-B acclimation. When the number of young per female was compared. the daphnids acclimated for 11 generations tend to produce less number of neonates than the un-acclimated individuals but with no statistical significance (p>0.05). Four metals that were reported to be phototoxic elsewhere were employed in this evaluation, that include As, Cd. Cu, and Ni. UV-B level being applied in acclimation did increase the toxicity of Cd and Cu, significantly (p<0.05). However, the toxicities of As and Ni were not affected by irradiation of UV-B. Phototoxic responses were evaluated between the acclimated and the un-acclimated daphnids. For Cu, UV-B acclimation led to reduction of the photo-induced toxicity $(p\approx0.1)$ in daphnids. Non-acclimated Daphnia were affected by 50% at 4.18 ug/l Cu. but UV-B acclimated individuals exhibited $EC_{50}$ of 5.89 ug/l. With Cd, UV-B acclimation appeared to increase phototoxicity (p>0.05). With As and Ni, UV-B acclimation did not influence photo-induced toxicity. This observation may be in part explained by the type of reactive oxygen species that were generated by each metal. Similar to UV-B light, Cu is known to generate superoxide anion by acting as redox cycling toxicant. This is one of the first studies that employed_laboratory based UV-B acclimated test species for photoenhanced toxicity evaluation.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.67-74
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• 2005

Toxicity tests were performed to evaluate the feasibility of application with prediction models to 10 mixture chemicals (chloroneb, butylbenzylphthalate, pendimethaline, di-n-butylphthalate, di-iso-butylphthalate, diazinon, isofenphos, 2-chlorophenol, 2,4,6-trichlorophenol and p-octylphenol) detected in effluents from wastewater treatment plants (WWTPs). Ten chemicals were selected in the basis of their toxicities to Daphnia magna and the concentrations in effluents measured by GC/MS. Three models including concentration addition (CA), independent action (IA) and effect summation (ES) were employed for the comparison of the predicted and the observed mortality of D. magna exposed to 10 mixture chemicals for 48 hours. With a comparative study it was ineffective to predict the mortality through the CA and the ES prediction model, while the IA prediction model showed a high correlation($r^2\;=\;0.85$). Moreover, the ES model over-estimated the toxicity observed by bioassay experiments about five-fold. Consequently, IA model is a reasonable tool to predict the mixture toxicity of the discharging water from WWTPs.

• Journal of Korean Society on Water Environment
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• v.30 no.1
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• pp.80-86
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• 2014

Unlike to natural organic matters (NOMs), effluent organic matters (EfOMs) are not well understood due to their complexity and heterogeneity. In this study, EfOMs from sewage and industrial wastewater treatment effluents and Suwannee River NOM (SRNOM) were isolated into hydrophobic (HPO), transphilic (TPI) and hydrophilic (HPI) fractions. Specific ultraviolet absorbance (SUVA) and fluorescence excitation emission matrix (FEEM) analyses were used to characterize physicochemical properties. In addition, acute toxicity and oxidative stress to Daphnia magna were evaluated to characterize toxicological properties. EfOMs showed similar properties to microbially derived organic matters having low hydrophobicity, which are totally different from SRNOM having high hydrophobicity. Moreover, acute toxicity and antioxidant enzyme activity in D. magna was largely dependent on fraction types of EfOMs. These findings suggest that EfOMs have different physicochemical and toxicological properties compared with those of NOMs, which needs to be further identified with various sources of EfOMs.

• Ecology and Resilient Infrastructure
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• v.2 no.4
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• pp.345-350
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• 2015

The toxicity of red mud (RM) pellets for water purification was evaluated using Pseudokirchneriella subcapitata and Daphnia magna in a lab-scale experiment. According to the algal growth inhibition test, both specific growth rates and relative growth rates of P. subcapitata decreased, and the growth inhibition rates increased ($R^2=0.97$, p<0.001) as the concentration of RM pellets in the aqueous solution increased (>1.6 g/L). Also, based on the acute toxicity evaluation test on D. magna, toxic unit (TU) values ranged between 0.00 and 2.83, and increased with an increase in the concentration of RM pellets in the aqueous solution. A correlation analysis indicated that the pH of RM pellets was statistically correlated with TU values ($R^2=0.77$, p=0.02). The environmental implication from this study is that the concentration of RM pellets in an aqueous solution needs to be lower than 4.4 g/L to keep the maximum permissible TU value less than 1.0.

• The Korean Journal of Pesticide Science
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• v.8 no.2
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• pp.117-128
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• 2004

The influence of different feeding rates of three green algae on growth and reproduction in four Korean cladocera, Daphnia sp., Daphnia obtusa, Moina macrocopa, and Simocephalus vetulus was investigated. The growth and reproduction rates of Daphnia sp. fed Chlorella vulgaris cells were significantly increased than those of daphnid fed Senedesmus subspicatus and Selenastrum carpricornutum. The total offsprings of Daphnia sp. fed $25\times10^4$ and $50\times10^4$ cells Chlorella vulgaris for 21days were $124{\pm}2.8$ and $168{\pm}22.1$, respectively. The Daphnia obtusa fed $25\times10^4$ and $50\times10^4$ cells Selenastrum carpricornutum was shown good reproduction rates, $72.2{\pm}7.9$ and $79.6{\pm}22.9$, respectively. The Moina macrocopa fed $25\times10^4$ and $50\times10^4$ cells Senedesmus subspicatus as well as Simocephalus vetulus and $25\times10^4$ and $50\times10^4$ cells Chlorella vulgaris were shown good reproduction rates. All of algae tested were sufficient as a good diet for Korean Cladocerans in this study. However, the preferred alga was Chlorella vulgaris and the optimal feeding concentrations were $2.5\times10^5\sim5\times10^5$ cells/mL, because the alga was shown most stable and generally high production rates in all cladocerans tested.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.281-289
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• 2021

Commercially used disposable cups undergo fragmentation in the environment and become microplastics (MPs). These MPs can be ingested by aquatic organisms and cause a range of adverse effects. We assessed the acute and chronic toxicity of disposable cup-derived MP fragments in Daphnia magna. MP fragments were identified as a polyethylene terephthalate (PET) fragment with a size of 33.18 ± 7.76 ㎛. The presence of three additives including 1- Propanone. 1-phenyl-3-[2-(phenylmethoxy)phenyl]-, p-Xylene and ethylbenzene was analyzed from MP fragments. The 48 h acute toxicity revealed that 20 % of immobilization and mortality were found at the highest concentration of PET MP (200 mg L^-1). The 21 d chronic toxicity revealed that PET MP fragments significantly (p < 0.05) more reduced survival rate (31 %), total offspring (52 %) in D. magna compared with control group. The developmental abnormality of offspring (3.5%) by PET MP fragments was significantly (p < 0.05) higher than control groups (0.3%). These results are possibly induced by gut blocking by ingestion of MP fragments and their longer retention time. These findings indicate that the fragmentation of disposable cups (PET polymers) into small-sized MP fragments pose a significant ecological risk to aquatic organisms. Further studies are required to elucidate the underlying toxicity mechanisms.

• Journal of Korean Society on Water Environment
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• v.33 no.2
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• pp.181-186
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• 2017

This paper aimed to evaluate the results of alternative acute toxicity test on 83 wastewater samples. Each sample was tested by traditional method (using laboratory cultured D. magna as a test organism) and alternative method (using Toxikit which can be purchased from a specialized company). The relationship between Lab. culture toxicity and Toxkits toxicity indicated good relation ($r^2=0.84$, p<0.01, n = 83). Number of samples which showed a small difference of lower than 0.5 between two test methods were 52 and they account for 63 percent of collected samples. In addition, these 52 samples had a lower average toxicity of TU 0.5 (Lab. culture method) and TU 0.45 (Toxkits method). Whereas samples which indicated big difference of test results between two methods, had a tendency to show higher toxicity. From these results, alternative toxicity test method could be applied to the official test method, if samples would have a lower toxicity less than TU 2. Also, Toxikit standard toxicant test results indicated $EC_{50}$ values between 0.93 and 1.68 mg/L and these results were considered as valid for quality control standard.

• KSBB Journal
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• v.26 no.1
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• pp.7-12
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• 2011

In order to perform an acute toxicity assessment of a new algicide, thiazolidinedione derivative (TD53) with enhanced solubility and lower toxicity to marine ecosystem, representative 3 organisms: plant plankton (Skeletonema costatum), animal plankton (Daphnia magna), fish (Paralichthys olivaceus) related in the food chain of marine ecosystem according to OECD standard methods were employed in the exposure experiment. The exposure assessment showed that $EC_50$ of S. costatum in 96-hour, $EC_50$ of D. magna in 48-hour and $LC_50$ of P. olivaceus in 72-hour for TD53 were $1.53\;{\mu}M$, $0.61\;{\mu}M$ and $2.14\;{\mu}M$ respectively. NOEC (No Observed Effect Concentration) and PNEC (Predicted No Effect Concentration) were calculated to be $0.25\;{\mu}M$ and 6.10 nM, respectively from $EC_50$ of most sensitive strain, D. magna. Comparing with the results of toxicity assessment previously performed by using Ulva pertusa Kjellman accepted as an ISO standard method, the values of PNEC showed 3.7 times lower toxicity in case of this study employing 3 organisms, indicating that if the organisms which are more representative and sensitive in marine ecosystem are further investigated, more accurately and validly predicted toxicity of TD53 could be applied in field.

• Journal of Ecology and Environment
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• v.31 no.2
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• pp.125-129
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• 2008

To predict Daphnia secondary productivity along a trophic gradient indexed as total phosphorus (TP) concentration, we estimated energy transfer efficiencies from food quality for Daphnia such as eicosa-pentaenoic acid (EPA) or docosahexaenoic acid (DHA) content. Eleven flow-through Daphnia magna growth experiments were conducted with seston from 9 lakes, ponds and river waters. Primary productivities were estimated from food supply rates in the flow-through experiments, producing energy transfer efficiencies from seston to D. magna. We found DHA content was the best predictor of energy transfer efficiencies among the essential fatty acids. An asymptotic saturation model explained 79.6% of the variability In energy transfer efficiencies. Based on empirical data in this study and empirical models from literature, we predict that Daphnia productivity would peak in mesotrophic systems by decreasing food quality and Increasing food quantity along trophic gradient.