53 research outputs found
Kinetics of toluene degradation by toluene-oxidizing bacteria as a function of oxygen concentration, and the effect of nitrate
The kinetics of toluene degradation as a function of oxygen concentration were compared for six strains of toluene-oxidizing bacteria using initial rate assays. The effect of nitrate was also examined. Rates of degradation and the relative effect of oxygen on the degradation rate were correlated with the pathway for toluene oxidation. Strains which synthesize toluene dioxygenases, Pseudomonas putida F1, P. fluorescens CFS215, and Pseudomonas sp. strain W31, degraded toluene at significantly higher rates (151â166 nmol/mg per min) than strains synthesizing toluene monooxygenases, Burkholderia cepacia G4 (23 nmol/mg per min) and B. pickettii PKO1 (14 nmol/mg per min), or a methylmonooxygenase, P. putida PaW1 (12 nmol/mg per min). Rates declined 30â48% for the dioxygenase strains and 25% for PaW1 as the oxygen concentration was decreased from 240 to 50 ÎM, but declined less than 10% for G4 and PKO1. Nitrate enhanced toluene degradation by the denitrifying strains PKO1 and W31 at oxygen concentrations below 30 ÎM, but had no significant effect on any of the other strains. Biphasic kinetics were observed for all of the strains, with double-reciprocal plots of the data exhibiting an inflection point at a âcritical oxygen concentrationâ between 20 and 30 ÎM. Below this concentration, the rate of toluene degradation was inhibited to a greater extent than predicted by the kinetic data for higher oxygen concentrations. For the denitrifying strains PKO1 and W31, however, monophasic kinetics were observed when nitrate was provided as an alternative electron acceptor. These observations suggest that biphasic kinetics result when rates of toluene degradation are limited by the availability of electron acceptor at the critical oxygen concentration, and that this limitation is overcome by denitrifying strains able to respire nitrate. Taken together, our findings suggest that the synthesis of monooxygenases and the ability to denitrify represent independent adaptations for toluene utilization in low oxygen environments. Moreover, these data support the use of nitrate in mixed electron acceptor strategies for the bioremediation of contaminated aquifers, as well as the targeted use of monooxygenase and dioxygenase strains in settings in which their physiological traits can be best exploited.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74870/1/j.1574-6941.1997.tb00387.x.pd
Inadequate Monitoring and Inappropriate Project Goals: A Case Study on the Determination of Success for the Forester Creek Improvement Project
Decentralized water management: rainwater harvesting and greywater reuse in an urban area of Beijing, China
Salt Marsh Reduces Fecal Indicator Bacteria Input to Coastal Waters in Southern California
Design and Construction of Wetlands for Aqueous Transfers and Transformations of Selected Metals
Intercomparison and validation of computer codes for thermalhydraulic safety analysis of heavy water reactors
Activities within the frame of the IAEAâs Technical Working Group on Advanced
Technologies for HWRs (TWG-HWR) are conducted in a project within the IAEAâs
subprogramme on nuclear power reactor technology development. The objective of the
activities on HWRs is to foster, within the frame of the TWG-HWR, information exchange
and co-operative research on technology development for current and future HWRs, with an
emphasis on safety, economics and fuel resource sustainability.
One of the activities recommended by the TWG-HWR was an international standard problem
exercise entitled: âIntercomparison and validation of computer codes for thermalhydraulics
safety analysesâ. Intercomparison and validation of computer codes used in different
countries for thermalhydraulics safety analyses will enhance the confidence in the predictions
made by these codes. However, the intercomparison and validation exercise needs a set of
reliable experimental data. The RD-14M Large-Loss Of Coolant Accident (LOCA) test
B9401 simulating HWR LOCA behaviour that was conducted by Atomic Energy of Canada
Ltd (AECL) was selected for this validation project. This report provides a comparison of the
results obtained from six participating countries, utilizing four different computer codes.
General conclusions are reached and recommendations made.
The IAEA expresses its appreciation to the CANDU Owners Group (COG) for releasing the
experimental data to the international community, and to D. Richards of AECL, Canada for
leading the activity. The IAEA officer responsible for this publication was R. Lyon of the
Division of Nuclear Power
Leached Compounds from Smoked Cigarettes and Their Potential for Bioaccumulation in Rainbow Trout (Oncorhynchus mykiss)
Cigarette butts are one of the most prevalent forms of
litter worldwide
and may leach toxic compounds when deposited in aquatic environments.
Previous studies demonstrated that smoked cigarette leachate is toxic
toward aquatic organisms. However, the specific bioavailable chemicals
from the leachate and the potential for human and wildlife exposure
through the food chain were unknown. Using a nontargeted analytical
approach based on GCĂGC/TOF-MS, 43 compounds were confirmed to
leach from smoked cigarettes when exposed to a water source. Additionally,
the bioaccumulation potential of organic contaminants in an edible
fish, rainbow trout (Oncorhynchus mykiss), was assessed through direct exposure to the leachate of smoked
cigarettes at 0.5 CB/L for 28 days. There was a significant reduction
in fish mass among the exposed rainbow trout vs the control group
(Ï2 (1) = 5.3, p = 0.021). Both
nontargeted and targeted chemical analysis of representative fish
tissue identified four tobacco alkaloids, nicotine, nicotyrine, myosmine,
and 2,2âČ-bipyridine. Their average tissue concentrations were
466, 55.4, 94.1, and 70.8 ng/g, respectively. This study identifies
leached compounds from smoked cigarettes and demonstrates the uptake
of specific chemicals in rainbow trout, thus suggesting a potential
for accumulation in food webs, resulting in human and wildlife exposure
Verification of enhanced phosphate removal capability in pure cultures ofAcinetobacter calcoaceticus under anaerobic/aerobic conditions in an SBR
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