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491.
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Field and microcosm observations of methanogenic phenolic compound degradation indicate that Monod kinetics governs the substrate disappearance but overestimates the observed biomass. In this paper we present modeling results from an ongoing multidisciplinary study of methanogenic biodegradation of phenolic compounds in a sand and gravel aquifer contaminated by chemicals and wastes used in wood treatment. Field disappearance rates of four phenols match those determined in batch microcosm studies previously performed by E.M. Godsy and coworkers. The degradation process appears to be at steady-state because even after a sustained influx over several decades, the contaminants still are disappearing in transport downgradient. The existence of a steady-state degradation profile of each substrate together with a low biomass density in the aquifer indicate that the bacteria population is exhibiting no net growth. This may be due to the oligotrophic nature of the biomass population in which utilization and growth are approximately independent of concentration for most of the concentration range. Thus a constant growth rate should exist over much of the contaminated area which may in turn be balanced by an unusually high decay or maintenance rate due to hostile conditions or predation. 相似文献
493.
Michael Gochfeld Iris Udasin Elissa Favata Gail Buckler Carol Natarelli Joanna Burger 《Environmental monitoring and assessment》1993,25(2):99-107
The blood lead levels of 568 New Jersey hazardous waste workers were determined at least once in the period 1984–1987. Workers almost always wore protective clothing in the field, which should have prevented exposure to lead. Therefore, despite their occupation, these workers are probably representative of the New Jersey suburban population in the mid-1980s. Blood lead levels ranged from 2.0–20.7 µg/dL, with an arithmetic mean value of 5.8 µg/dL, representing a decline from levels measured a decade earlier, but there was no clear change over the four years of the study. Blood lead levels increased with age of the worker up to age 60. Women showed lower levels than men in every age group. 相似文献
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Michael Sivak 《Journal of Safety Research》1996,27(4):225-231
This article provides a public-health perspective on the motor-vehicle safety situation in Europe and in the United States. It will be argued that a prerequisite for such a perspective is the use of fatality rate per capita, instead of the usually employed rate per distance traveled. To illustrate the public-health perspective, two sets of analyses were performed. The first set of analyses compared motor-vehicle fatality rates to fatality rates from other causes of death. The second set contrasted the motor-vehicle fatality rates per population in different countries, providing information about traffic safety relative to other countries. 相似文献
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Among employees of comparable organizations in the United States and New Zealand, role stressors (ambiguity and conflict), along with effort-to-performance uncertainty, performance-to-outcome uncertainty and doubt about acceptance by one's supervisor, generally predicted job satisfaction, psychological strain and turnover intentions. Path analyses of three alternative theoretical models highlighted the importance of job satisfaction as a mediator of the effects of role stressors and uncertainty on strain and turnover intentions. Role stressors contributed separately and via uncertainty to all three outcome measures, but subordinate perceptions of supervisor behaviors added little independent predictive power, once the role stressors and uncertainty were accounted for. These findings support the hypothesis that supervisors can influence the degree of role stress and uncertainty which their subordinates experience, which in turn may affect levels of satisfaction, strain and turnover intentions. 相似文献
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Michael J. Szarek Iris R. Bell Gary E. Schwartz 《Journal of environmental psychology》1997,17(4):345-351
The development and validation of a brief self-report screening measure of environmental chemical sensitivity, the Chemical Odor Intolerance Index (CII), is described. Subjects included 1734 college students, 192 older adults, and 38 chemically intolerant and multiple chemical sensitivity (MCS) patients. The results of the studies demonstrate that the CII has strong internal stability (Cronbach's alpha ranging from 0.80 to 0.92 across samples), and evidence of factorial, group, convergent, and discriminant validity is reported across diverse samples. In future research, the CII will permit the quantification of self-reported illness from low levels of environmental chemicals as a continuous rather than dichotomous variable. Consequently, the CII will facilitate the ability to compare and standardize subject selection criteria in both preclinical and clinical (i.e. MCS) populations. 相似文献