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Optimization and performance evaluation of the continuous algal toxicity test
(1997-07-01)
Chen, CY
;
Lin, KC
;
環境工程研究所
;
Institute of Environmental Engineering
Responses of Selenastrum capricornutum to cadmium in a chemostat are evaluated under various test conditions defined by the nitrogen to phosphorus ratio, phosphate strength, dilution rate, and ethylenediaminetetraacetic acid content. Based on the test results, these parameters were optimized to achieve superior test sensitivity. This continuous system was also modified to allow testing on a weekly basis. The performance of the modified testing technique was evaluated, employing six different metal toxicants. Compared with batch test results reported by other researchers and our own experiment, the continuous test achieved superior sensitivities and reproducibility. The test method presented in this study is believed to be an ideal technique both for research and regulatory purposes.
Effects of inoculum's mean cell volume on algal toxicity tests
(2000)
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
The aim of the present study is to compare the effects of the mean cell volume (MCV) of algal inoculum to the sensitivity and reproducibility of the toxicity test. Two sets of experiments were conducted using inoculums with the MCV equal to 60 mum(3)/cell and 40 mum(3)/cell, respectively. The initial cell densities, however, were kept the same at 10,000 cells/ml. The results show that larger MCV of the inoculum results in greater EC50 values. Similar observations and conclusions were obtained from comparisons based on NOEC values. Thus, MCV of the inoculum significantly influences the observed toxic response in terms of EC50 and NOEC values. It is also evident that, there is a significant increase in the test variability if the MCV is not controlled properly. This study reports that standardizing the initial mean cell volume of algal culture can improve inter-laboratory and intra-laboratory precision. Furthermore, replacing the EC50 values by the calculated exposure values (EE50) can reduce the variability in data due to differences in the MCV of the inoculum.
Statistical comparisons of the no-observed-effect concentration and the effective concentration at 10% inhibition (EC10) in algal toxicity tests
(2001)
Shieh, JN
;
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
Batch-type algal toxicity tests were conducted to evaluate the low toxic effects of metal toxicants. Both the no-observed-effect concentration (NOEC) and the effective concentration at 10% inhibition (EC10) were calculated and compared. The results of this study indicate that, for algal toxicity tests, NOEC. offers better protection to the test organisms than EC10. In addition, the consistency of NOEC is found to depend on the response endpoints measured. A cut-off-value approach is proposed to determine whether NOEC or EC10 should be chosen for estimating low toxic effects. For a specific toxicity test, the average cut-off value directly indicates the magnitude of the square root of the within-group-variance. A precise test associated with small within-group-variances also produces relatively small average cut-off value (say, less than 10% of the growth reduction). This average value provides useful information on the minimum protection that can be offered by the NOEC.
Discrepancies between different response parameters in batch and continuous algal toxicity tests
(2001-03-30)
Chao, MR
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
The test sensitivities and reproducibilities based on different response endpoints (cell density and total cell volume) were compared using both bath and continuous algal toxicity tests. Parameters related to algal cell density are found to be more sensitive and reproducible than total cell volume which bears a direct correlation to algal biomass or dry weight. The magnitude of differences in the median effective concentration values could be upto six folds. The main cause for the above discrepancies is because the cell density and total cell volume are two response endpoints reflecting the degree of inhibition on the binary fission mechanism and overall photosynthesis, respectively. At low toxicant concentrations, the inhibitory effect is primarily on the cell division rather than on the cellular photosynthesis. Thus, more severe toxic effects are expected to be observed based on the cell density than the total cell volume. The results of this study clearly demonstrate that sensitivity and reproducibility can be significantly improved if response parameters are calculated based on the cell density. Traditionally, cell density data are often converted into biomass before assessing the effects of toxicants. This procedure may not be necessary and may reduce the test sensitivity. (C) 2001 Elsevier Science B.V. All rights reserved.
A novel algal toxicity testing technique for assessing the toxicity of both metallic and organic toxicants
(2005-05-01)
Lin, JH
;
Kao, WC
;
Tsai, KP
;
Chen, CY
;
環境工程研究所
This study presents a closed-system algal toxicity test technique that is capable of detecting the effects of both organic and metallic toxicants. Toxicity testing was conducted by transferring adequate amounts of algal suspension, dilution water (with culture growth medium), and toxicants into 300-mL BOD bottles. The BOD bottles were completely filled up with no head-space left. The initial cell density and the exposure time were 15,000 cells/mL and 48 h, respectively. The performance of the above test method was evaluated using three heavy metals and six organic toxicants based on three different test endpoints, i.e., dissolved oxygen production, algal growth rate, and cell density. The proposed test revealed excellent test sensitivity and reproducibility. Currently, none of the existing algal toxicity test protocols is adequate for assessing the toxicity of organic chemicals. The closed-system algal toxicity tests developed by previous researchers also may not be ideal because the enlarged headspace and/or enriched bicarbonate buffer may result in either underestimations of the exposure concentrations or insensitive responses to both heavy metals and organic toxicants. Compared to the aforementioned algal toxicity test methods, the proposed technique in the present study has a more general applicability under conditions such as effluent samples containing both metals and organic toxicants or samples with unknown compositions. (c) 2005 Elsevier Ltd. All rights reserved.
Individual and combined toxicity of nitriles and aldehydes to Raphidocelis subcapitata
(2005-05-01)
Chen, CY
;
Chen, SL
;
Christensen, ER
;
環境工程研究所
;
Institute of Environmental Engineering
A closed- system algal toxicity test with no headspace was applied to evaluate the toxicity of I I aldehydes and two nitrites to Raphidocelis subcapitata. Algal growth rate and dissolved oxygen (DO) production were used as the test endpoints. Compared to literature data, our test results based on the endpoint of DO production is 2.5 to 257 times more sensitive than the conventional algal batch tests. In addition, our analyses show that different relative toxicity relationships may be observed when different test methods or different endpoints are applied. The test alga was found to be quite sensitive to aldehydes, and a quantitative structure- activity relationship (QSAR) relationship was established based on the n-octanol/water partition coefficient (log K,,.). This study also evaluated the combined effects of aldehydes and nitriles. Four synergistic joint actions related to majononitrile were identified. On the other hand, most of the combined effects between aldehydes and acetonitrile were antagonistic. In general, we find that greater-than-additive effects mainly are associated with toxicants displaying flat dose-response curves, and less-than-additive effects may be related to certain steep-slope chemicals. Model analyses show that the above mixture toxicity behavior may be due to response addition or response multiplication joint action modes.
Toxicity of chlorophenols to Pseudokirchneriella subcapitata under air-tight test environment
(2006-01-01)
Chen, CY
;
Lin, JH
;
環境工程研究所
;
Institute of Environmental Engineering
A closed-system algal toxicity test with no headspace was applied to evaluate the toxicity of chlorophenols to Pseudo-kirchneriella subcapitala. The dissolved oxygen production and the growth rate based on cell density were the response endpoints. Phenol and seven chlorophenols were tested using the above test technique. Median effective concentrations (EC50) range from 0.004 to 25.93 mg/l (based on DO production) and 0.0134 to 20.90 mg/l (based oil growth rate). No-observed-effect concentration (NOEC) is within the range of 0.001-8.19 mg/l. In general, growth rate is a more sensitive response endpoint than the oxygen production, except for the case of pentachlorophenol. However, the differences in sensitivity between the two parameters were marginal. Furthermore, quantitative structure-activity relationships (QSAR's) based on the n-octanol/water partition coefficient (log P) and the acid dissociation constant (pK(a)) values were established with R-2 ranged from 0.90 to 0.96. From literature data also based on P. subcapitata, the new test method is 1.65-108 times more sensitive than the conventional algal batch tests. A completely different relative-sensitivity relationship among various aquatic organisms was thus observed. The results of this study indicate that the toxicity data of volatile organic chemicals derived by conventional algal toxicity tests may severely underestimate the impact of these toxicants. Our results show that alga is very sensitive to chlorophenols compared to other aquatic organisms Such as the luminescent bacteria (the Microtox test), Daphnia magna, and rainbow trout. (c) 2005 Elsevier Ltd. All rights reserved.
Toxicity assessment of pesticides to Pseudokirchneriella subcapitata under air-tight test environment
(2006-04-17)
Yeh, HJ
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
This paper presents the toxicity data of seven pesticides including atrazine, parathion, dichlorvos, malathion, fenthion, 2-methyl-4-chiorophenoxyacetic acid, and pentachlorophenol on Pseudokirchneriella subcapitata based on a new algal toxicity testing technique conducted under air-tight environment. The dissolved oxygen production and the cell density were adopted as the response endpoints. Median effective concentrations (EC50) range from 0.0035 to 3.40 mg/L (DO production) and from 0.0067 to 3.12 mg/L (cell density). No-observed-effect concentration (NOEC) was determined using the Dunnett's test. NOEC values are with in the range of 0.001-1.20 mg/L. In general, the two test endpoints revealed similar sensitivities. From comparisons of literature data also based on Pseudokirchneriella subcapitata, it is clear that conventional batch tests tend to underestimate the toxicity of pesticides due to their open test environment. Closed-system tests, i.e., microplate test, respirometer test, and our BOD-bottle test, generally provide better assessment to the effects of pesticides. Data based on our test method reveals much higher toxicity (3-100 times) than that from the conventional batch tests. Furthermore, for organophosphorus insecticides, results from the present study show that Pseudokirchneriella subcapitata is less sensitive than Daphnia magna and rainbow trout, but is more susceptible than fathead minnow. The closed-system test applied in this study provides more adequate assessment for the toxicity of pesticides than the conventional batch tests. (c) 2005 Elsevier B.V. All rights reserved.
The combined toxic effects of nonpolar narcotic chemicals to Pseudokirchneriella subcapitata
(2006-06-01)
Hsieh, SH
;
Tsai, KP
;
Chen, CY
;
環境工程研究所
;
Institute of Environmental Engineering
This paper presents the toxicity data of 10 nonpolar narcotic chemicals on Pseudokirchneriella subcapitata (green algae) assessed by a new algal toxicity testing technique conducted under air-tight environment. Based on DO production, median effective concentration (EC50) varies from 1.73mg/L (1-octanol) to8040 mg/L (2-propanol). The endpoint of algal growth rate reveals similar sensitivity as that from DO production. Compared to literature data, Pseudokirchneriella subcapitata and Nitrosomonas are apparently more sensitive to nonpolar narcotics than other organisms such as minnow, daphnia, and Tetrahymena pyriformis. Furthermore, good correlations between toxic effects observed from Pseudokirchneriella subcapitata and other aquatic organisms were found. Hence, algal toxicity test can be considered as a surrogate test for estimating the toxicity of nonpolar chemicals to fathead minnow, Microtox, activated sludge, Daphina magna, and Tetrohymena pyriformis. The combined effects of 13 binary mixtures of nonpolar chemicals were investigated using both additive-index method and isobologram analysis. overall speaking, the joint actions between these chemicals are strictly additive. Model analyses indicate that these compounds act on identical reaction sites or receptors, which verify that these chemicals are of the same toxicity mechanism (narcosis). (c) 2006 Elsevier Ltd. All rights reserved.
Optimization and performance evaluation of the continuous algal toxicity test
(1997-07-01)
Chen, CY
;
Lin, KC
;
交大名義發表
;
環境工程研究所
;
National Chiao Tung University
Responses of Selenastrum capricornutum to cadmium in a chemostat are evaluated under various test conditions defined by the nitrogen to phosphorus ratio, phosphate strength, dilution rate, and ethylenediaminetetraacetic acid content. Based on the test results, these parameters were optimized to achieve superior test sensitivity. This continuous system was also modified to allow testing on a weekly basis. The performance of the modified testing technique was evaluated, employing six different metal toxicants. Compared with batch test results reported by other researchers and our own experiment, the continuous test achieved superior sensitivities and reproducibility. The test method presented in this study is believed to be an ideal technique both for research and regulatory purposes.

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