Concentrations Of Test Chemicals Research Articles

Treating Soil Solution Samplers To Prevent Microbial Removal of Analytes

Soil microorganisms colonizing soil water sampling devices (lysimeters) reduced concentrations of biodegradable organic chemicals, including 2,4-dichlorophenoxyacetic acid methyl ester, alachlor, methyl m-chlorobenzoate, and metolachlor as water entered through porous ceramic cups. In some cases, losses exceeded 99%. Additions of either a biocide (sodium hypochlorite) or a bacteriostat (copper salt) prevented microbial activity so that concentrations of test chemicals inside lysimeters equaled those outside. Field studies further indicated that treating lysimeters with a copper salt effectively prevented microbial activity. Thus, chemically treating soil water samplers could improve the accuracy of soil water data for a wide variety of analytes, including environmentally important organics, such as pesticides and industrial wastes, and inorganics, such as ammonia and nitrate.

The european system of standardized legal tests for assessing the biodegradability of chemicals

A brief overview is given of the approach to biodegradation testing adopted by the European Economic Community (EEC) as part of the legislation on new chemicals. The tiered system of screening and simulation tests is outlined and the various tests are discussed briefly. It is concluded that the test strategy is logical and cost-effective, but that ongoing work to further harmonize and revise screening tests for ready biodegradability must be completed before these tests perform satisfactorily. The principles governing simulation tests should be further developed, and, in particular, the importance of the applied concentration of test chemical should be addressed.

Method for Estimating the Toxicity of Chemicals to Activated Sludge. II. A Rapid Determination and Application of Oxygen Uptake Rate by Using Oxygen Electrode.

This paper deals with the investigation of simple and rapid method to determine the toxicity value (IC50) of chemicals to activated sludge by using oxygen electrode. In this method, activated sludge was added to various concentrations of test chemicals and 50% inhibition of the oxygen uptake rate (OUR) was measured within 10 min. The IC50 values calculated to be 1.5 mg/l, 1.5 mg/l, 4.0 mg/1, 7.2 mg/l, 14 mg/1, 14mg/l, 20 mg/l, 75 mg/l, 108 mg/l and 2500 mg/l for mercury (II) chloride, copper (II) chloride, mercury (II) acetate, copper (II) acetate, 2, 3, 5-trichlorophenol, pentachlorophenol, p-nitrophenol, 3, 4-dimethylphenol, cyclohexylamine and aniline, respectively, agreed almost well with those reported in the literatures. In addition, the OUR of activated sludge inhibited specifically by mercury (II) chloride was easily recovered by the addition of thiol compounds such as 2-mercaptoethanol, thiosulfate and reductive glutathione, respectively. Reactivation by thiol compounds suggested that mercury (II) form reversible mercaptides with sulfhydryl groups of enzymes concerned in OUR. From these results, the OUR method would be applicable to a rapid determination for biochemical field or biodegradation test in the Law Concerning the Examination and Regulation of Manufacture, etc. Chemical Substances.

A method for measuring the biodegradation of organic chemicals

AbstractAn automated gas‐chromatographic measurement of carbon dioxide is described and its application to a biodegradation screening test procedure is demonstrated. The biodegradation test system consists of 20‐ml glass vials containing aqueous solutions of a test chemical and an acclimated microbial inoculum. The vials and their contents are sealed with rubber septa. At specified time intervals, the contents of selected vials are acidified. Subsequent automated headspace determination of carbon dioxide provides a measure of cumulative biological degradation. To demonstrate the validity of the overall test procedure, the biodegradabilities of eight organic compounds were measured: aniline, benzaldehyde, ethylenediaminetetraacetic acid, ethylene glycol, linear alkylbenzene sulfonate, nitrilotriacetic acid, p‐nitrophenol and N‐methylaniline. Biological degradation was also monitored by measuring residual test chemical concentrations. There was excellent internal consistency of results by comparison of carbon dioxide evolution values with specific chemical analyses. Both the results of carbon dioxide measurements and specific chemical analyses are discussed in relation to literature values derived from similar screening test procedures. It is concluded from this study that automated headspace determination of carbon dioxide has several advantages over existing test methods. It is further concluded that application of this headspace procedure in the screening test described provides an accurate, albeit conservative, estimate of biodegradability, with positive results indicating a low potential for environmental persistence.

A METHOD FOR MEASURING THE BIODEGRADATION OF ORGANIC CHEMICALS

An automated gas-chromatographic measurement of carbon dioxide is described and its application to a biodegradation screening test procedure is demonstrated. The biodegradation test system consists of 20-ml glass vials containing aqueous solutions of a test chemical and an acclimated microbial inoculum. The vials and their contents are sealed with rubber septa. At specified time intervals, the contents of selected vials are acidified. Subsequent automated headspace determination of carbon dioxide provides a measure of cumulative biological degradation. To demonstrate the validity of the overall test procedure, the biodegradabilities of eight organic compounds were measured: aniline, benzaldehyde, ethylenediaminetetraacetic acid, ethylene glycol, linear alkylbenzene sulfonate, nitrilotriacetic acid, p-nitrophenol and N-methylaniline. Biological degradation was also monitored by measuring residual test chemical concentrations. There was excellent internal consistency of results by comparison of carbon dioxide evolution values with specific chemical analyses. Both the results of carbon dioxide measurements and specific chemical analyses are discussed in relation to literature values derived from similar screening test procedures. It is concluded from this study that automated headspace determination of carbon dioxide has several advantages over existing test methods. It is further concluded that application of this headspace procedure in the screening test described provides an accurate, albeit conservative, estimate of biodegradability, with positive results indicating a low potential for environmental persistence.

A comparison of microbial bioassays for the detection of aquatic toxicants

The toxicity of 35 test chemicals was analyzed using two microbial bioassay systems. The commercially available Microtox Toxicity Analyzer System™ and the two-organism procedure of Tchan were used to determine the concentration of test chemicals resulting in a 50% reduction in response (EC 50). Both of the tests employed a luminescent bacterium while the procedure of Tchan also utilized an alga. Results from the two microbial tests were compared with available data obtained with fish toxicity bioassays and with each other. The Microtox™ procedure was somewhat more sensitive than the Tchan bioassay in detecting most of the test chemicals and fish bioassays were generally more sensitive than either of the microbial tests. As a notable exception, photosynthesis-inhibiting herbicides were detected at remarkably lower concentrations with the procedure of Tchan than any of the other bioassays. Potential applications for these tests are discussed.

A rapid method for determining the toxicity of chemicals to activated sludge

This paper reports the development of a method to determine the toxicity of chemicals to activated sludge. In the method, activated sludge was exposed to various concentrations of test chemicals and the inhibition of [ 14C]glucose uptake was measured after 15 min. Data for the decrease in glucose uptake as a function of the log of the test chemical concentration was analyzed by a nonlinear regression model to determine the concentration of chemical inhibiting uptake by 50% (IC 50 value). In control experiments, glucose uptake in the absence of test chemicals was rapid, specific and totally dependent on the presence of metabolically-active activated sludge. However, uptake in the presence of inorganic and organic test chemicals showed significant, dose-dependent decreases as the concentration of test material increased. Inhibition of uptake was accurately described by the nonlinear regression model, and calculated IC 50 values for two chemicals, mercuric chloride and 3,5-dichlorophenol, agreed well with values reported in the literature to adversely affect wastewater treatment plant operation. Based on the results of our studies, inhibition of glucose uptake proved to be a rapid, accurate and reproducible method of determining the toxicity of chemicals to activated sludge.

The E. coli pol A 1− assay A quantitative procedure for diffusible and non-diffusible chemicals

A procedure is described for determining the preferential killing of DNA repair-deficient E. coli. Dilute suspensions of DNA repair-proficient and -deficient bacteria are exposed to a graded series of test chemical concentrations. Survivors are determined by enumeration on agar plates. An expression used to express preferential killing (or lack thereof) is shown to be dose-dependent and potentially useful for determining genotoxic potencies.