摘要:

AbstractEarly life stages of smallmouth bass (Micropterus dolomieuiLacepede) were exposed to ammonia concentrations at four different pH values (from 6.5 to 8.7). Acute lethal tests were conducted with juveniles, and partial chronic tests were initiated at the late embryo stage and extended through 32 d of exposure.The 96‐h LC50 ammonia concentrations at pH 6.53, 7.16, 7.74 and 8.71 were 371, 117, 39.5 and 7.43 mg/L total ammonia‐N (NH3‐N) and 0.694, 1.00, 1.20 and 1.78 mg/L un‐ionized NH3, respectively. The acute toxicity of ammonia in terms of NH3‐N was directly related to test pH, and in terms of NH3was inversely related to pH.Embryo through preswim‐up larvae were the most resistant early life stages studied during chronic exposures. Survival of embryos to larvae 7 d post hatch was unaffected by ammonia concentrations ranging from 0.236 to 0.865 mg/L NH3at pH values of 6.60 to 8.68. Adverse effects on early developmental stages demonstrated that survival to 14 d and growth to 32 d were among the most sensitive indicators of ammonia toxicity. The estimated 32‐d no‐observed‐effect concentrations, defined as the geometric means of the maximum no‐effect and minimum effect concentrations determined from statistically significant decreases in growth (wet weight), were calculated to be 17.4, 14.4, 14.6 and 2.40 mg/L total NH3‐N and 0.0437, 0.148, 0.599 and 0.612 mg/L un‐ionized NH3at pH values of 6.60, 7.25, 7.83 and 8.68, respectively. The acute to chronic ratios, as calculated from NH3concentrations and acute results adjusted to the above pH values for chronic tests, were 16.7, 7.03, 2.07

ISSN:0730-7268    

DOI:10.1002/etc.5620040111

出版商:Wiley Periodicals, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractData are presented that discourage the use of total residual chlorine (TRC) and free residual chlorine (FRC) levels in setting water quality criteria for chlorine and chlorinated carrier molecules. Repetitive static acute toxicity tests for aging solutions of chlorinated complexes withDaphnia magnapermit generation of biological half‐lives for direct comparison with analytically derived concentrations of TRC and FRC. The results indicate a strong similarity in the decline of toxic effects onD. magnaand TRC for an aging solution of 1,3‐dichloro‐5,5‐dimethylhydantoin (DCDMH), although no such similarity exists between these two measures for aging solutions of chlorine and trichloro‐S‐triazinetrione (TCTT). Repetitive toxicity tests with aging DCDMH generated toxic decay curves with coefficients of determination (r2) exceeding 73% while exhibiting a minimum decay rate of ‐0.10. TRC data for DCDMH exhibited anr2of 93% and a decay rate of ‐0.07. Ther2values for the chlorine series ranged from 15 to 60% for the toxic effects decay curve, as compared with 76% for analytically derived data. The TCTTr2values for these same parameters were 23 to 64 and 84%, respectively. Both chlorine and TCTT presented definable, consistent decreases in TRC levels over the course of the studies, while the observed biological effects oscillated widely from test to test within a series. These results demonstrate that the standard reported parameters of TRC and FRC are inadequate for setting effluent limitations on chlorinated discharges because they are inconsistent in measuring the toxic constituents of

ISSN:0730-7268    

DOI:10.1002/etc.5620040112

出版商:Wiley Periodicals, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe Toxic Substances Control Act (TSCA) has focused governmental attention on the process of assessing the hazards from commercial chemicals. Environmental behavior and impact must be projected before the chemical is released. This requires a knowledge of the environment, relevancy of laboratory data, extent of necessary data and interpretation of those data for future impacts. The responsibility for the data rests with the manufacturer. The key criterion involves a determination of “unreasonable risk.” Six axiomatic principles of risk assessment are identified. This involves an interactive and interdisciplinary thought process that is both iterative and staged. A generalized procedure for exposure assessment has been developed. An initial risk assessment comparing projected environmental concentrations with probable effect levels determines the type and quantity of laboratory test data needed. As examples, three new and three existing chemicals with widely differing properties and uses have been evaluated for their potential environmental impa

ISSN:0730-7268    

DOI:10.1002/etc.5620040113

出版商:Wiley Periodicals, Inc.    

年代:1985

数据来源: WILEY