Distribution and transformation of elemental mercury in the St. Lawrence River and Lake Ontario

2000 ◽  
Vol 57 (S1) ◽  
pp. 155-163 ◽  
Author(s):  
Marc Amyot ◽  
David RS Lean ◽  
Laurier Poissant ◽  
Marie-Renée Doyon
Keyword(s):  
Water Column ◽  
Laboratory Experiments ◽  
Lake Ontario ◽  
Elemental Mercury ◽  
Volatile Species ◽  
Spatial And Temporal Patterns ◽  
First Order ◽  
Inland Lakes ◽  
First Order Kinetics ◽  
St Lawrence River

Elemental Hg (Hg0) is a volatile species that is responsible for water-to-air transfer of Hg in Lake Ontario and the St. Lawrence River. We conducted two cruises in 1998 to identify spatial and temporal patterns in Hg0 levels in these systems and performed field and laboratory experiments on redox transformations of Hg. Elemental Hg concentrations were higher in Lake Ontario than in the St. Lawrence River. At stations in Lake Ontario, Hg0 levels were higher at the bottom of the water column than at the surface, whereas they were homogeneous throughout the water column of the river. Elemental Hg concentrations were generally higher in July than in September and, in contrast with experiments on inland lakes, were relatively constant during the day except for a narrow peak at sunrise. Field and laboratory experiments showed that photoreduction of Hg(II) in St. Lawrence River water was substrate limited and was influenced by visible and ultraviolet radiation. Pseudo first-order kinetics best described photoreduction, with k values between 1 and 2·h-1.

Oxidation of the mercurous ion by peroxidase

1986 ◽  
Vol 64 (5) ◽  
pp. 969-972 ◽  
Author(s):  
Donald C. Wigfield ◽  
Season Tse
Keyword(s):  
Elemental Mercury ◽  
Order Rate Constant ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Order Rate ◽  
First Order Kinetics ◽  
Cold Vapour ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Mercurous Ion

The kinetics of oxidation of the mercurous ion by peroxidase have been measured by following the disappearance of mercurous ion using cold-vapour atomic absorption spectroscopy. Pseudo-first-order kinetics are observed with respect to mercurous ion, and the pseudo-first-order rate constants are linearly related to peroxidase concentration, showing first-order dependence on peroxidase. This behaviour is identical to oxidation of elemental mercury, and the second-order rate constant, 1.44 × 104 M−1 s−1 at 23 °C, is also, within experimental error, the same as that for elemental mercury oxidation. The data are interpreted in terms of peroxidase-induced disproportionation of the mercurous dimer, followed by two-electron oxidation of zero-valent mercury.

F-Specific RNA Bacteriophages as Model Viruses in UV Disinfection of Wastewater

1991 ◽  
Vol 24 (2) ◽  
pp. 347-352 ◽  
Author(s):  
A. H. Havelaar ◽  
Th J. Nieuwstad ◽  
C. C. E. Meulemans ◽  
M. van Olphen
Keyword(s):  
Laboratory Experiments ◽  
Uv Disinfection ◽  
Somatic Coliphages ◽  
Process Indicator ◽  
Practical Applications ◽  
First Order ◽  
Inactivation Rate Constant ◽  
First Order Kinetics ◽  
Naturally Occurring ◽  
High Concentrations

F-specific RNA (FRNA) bacteriophages can be assayed in wastewater by simple and rapid methods. Their inactivation by UV radiation follows first-order kinetics and relatively simple formulas can describe the effect of UV absorbance by wastewater and the wavelength-dependent killing efficiency of polychromatic lamps. Because the organisms can be grown in high concentrations, biological calibration of full-scale reactors requires only relatively small volumes of phage culture. Naturally occurring FRNA-phages were more resistant to UV than somatic coliphages, Escherichiacoli and faecal streptococci. The inactivation rate constant was almost equal to that of reoviruses, which underlines the suitability of FRNA-phages as a process indicator for UV inactivation of viruses. A pure culture of MS2 was inactivated at a rate which was almost twice that of naturally occurring FRNA-phages, indicating the necessity of designing reactors for practical applications on field-data rather than laboratory experiments.

Spatial and Temporal Patterns of Hydrogen Peroxide in Lake Waters

1989 ◽  
Vol 46 (7) ◽  
pp. 1227-1231 ◽  
Author(s):  
W. J. Cooper ◽  
D. R. S. Lean ◽  
J. H. Carey
Keyword(s):  
Metal Speciation ◽  
Spatial And Temporal Patterns ◽  
Short Term ◽  
Mixing Processes ◽  
Depth Profiles ◽  
First Order ◽  
First Order Kinetics ◽  
Dark Decay ◽  
And Behavior ◽  
Lake Waters

Depth profiles of H2O2 concentration were measured at three stations in Lake Erie, one in Lake Ontario and in Jacks Lake. Epilimnetic concentrations followed changes in solar radiation suggesting that the formation resulted from photochemical or perhaps photoautotrophic processes. Mid-day H2O2 concentrations of 100–200 nM were observed at all locations. Dark decay of H2O2, determined at several depths at two locations, followed apparent first order kinetics with half lives from 10–22 h. H2O2 may be useful as a tracer for short term mixing processes and as a powerful oxidizing agent can influence metal speciation, degradation of some organic pollutants, as well as the survival and behavior of organisms.

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 167-178 ◽  
Author(s):  
Xin Tong ◽  
Jiao Li ◽  
Jun Ma ◽  
Xiaoquan Chen ◽  
Wenhao Shen
Keyword(s):  
Degradation Rate ◽  
Southern China ◽  
Catalytic Degradation ◽  
Pulp And Paper ◽  
Gaseous Pollutants ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH < 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

Loadings of Selected Chemicals into the St. Lawrence River System from Lake Ontario, 1986/87

1989 ◽  
Vol 24 (4) ◽  
pp. 589-608 ◽  
Author(s):  
I.K. Tsanis ◽  
J. Biberhofer ◽  
C.R. Murthy ◽  
A. Sylvestre
Keyword(s):  
Mass Balance ◽  
Lake Ontario ◽  
River System ◽  
Vertical Gradient ◽  
The South ◽  
Measured Concentration ◽  
Chemical Monitoring ◽  
The North ◽  
Loading Estimates ◽  
St Lawrence River

Abstract Determination of the mass output through the St. Lawrence River outflow system is an important component in computing mass balance of chemical loadings to Lake Ontario. The total flow rate in the St. Lawrence River System at the Wolfe Island area was calculated from detailed time series current meter measurements from a network of current meters and Lagrangian drifter experiments. This flow is roughly distributed in the ratio of 55% to 45% in the South and North channel, respectively. Loading estimates of selected chemicals have been made by combining the above transport calculations with the ongoing chemical monitoring data at the St. Lawrence outflow. A vertical gradient in the concentration of some organic and inorganic chemicals was observed. The measured concentration for some of the chemicals was higher during the summer months and also is higher in the South Channel than in the North Channel of the St. Lawrence River. These loading estimates are useful not only for modelling the mass balance of chemicals in Lake Ontario but also for serving as input loadings to the St. Lawrence River system from Lake Ontario.

Zebra Mussels as Biomonitors for Organic Contaminants in the Lower Great Lakes

1996 ◽  
Vol 31 (2) ◽  
pp. 411-432 ◽  
Author(s):  
Michael E. Comba ◽  
Janice L. Metcalfe-Smith ◽  
Klaus L.E. Kaiser
Keyword(s):  
Great Lakes ◽  
Organic Contaminants ◽  
Lake Erie ◽  
Soft Tissues ◽  
Lake Ontario ◽  
Dry Weight ◽  
Zebra Mussels ◽  
Organic Contamination ◽  
Contamination Levels ◽  
St Lawrence River

Abstract Zebra mussels were collected from 24 sites in Lake Erie, Lake Ontario and the St. Lawrence River between 1990 and 1992. Composite samples of whole mussels (15 sites) or soft tissues (9 sites) were analyzed for residues of organochlo-rine pesticides and PCBs to evaluate zebra mussels as biomonitors for organic contaminants. Mussels from most sites contained measurable quantities of most of the analytes. Mean concentrations were (in ng/g, whole mussel dry weight basis) 154 ΣPCB, 8.4 ΣDDT, 3.5 Σchlordane, 3.4 Σaldrin, 1.4 ΣBHC, 1.0 Σendosulfan, 0.80 mirex and 0.40 Σchlorobenzene. Concentrations varied greatly between sites, i.e., from 22 to 497 ng/g for ΣPCB and from 0.08 to 11.6 ng/g for ΣBHC, an indication that mussels are sensitive to different levels of contamination. Levels of ΣPCB and Σendosulfan were highest in mussels from the St. Lawrence River, whereas mirex was highest in those from Lake Ontario. Overall, mussels from Lake Erie were the least contaminated. These observations agree well with the spatial contaminant trends shown by other biomoni-toring programs. PCB congener class profiles in zebra mussels are also typical for nearby industrial sources, e.g., mussels below an aluminum casting plant contained 55% di-, tri- and tetrachlorobiphenyls versus 31% in those upstream. We propose the use of zebra mussels as biomonitors of organic contamination in the Great Lakes.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

Decomposition of 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenezenesulfonic Acid) in Solutions ofFD&C Red No. 40

1984 ◽  
Vol 67 (4) ◽  
pp. 844-845
Author(s):  
Naomi Richfield-Fratz
Keyword(s):  
Liquid Chromatography ◽  
Aqueous Solutions ◽  
Borate Buffer ◽  
Sodium Borate ◽  
First Order ◽  
First Order Kinetics ◽  
Color Additive ◽  
Sodium Borate Buffer

Abstract 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenzenesuIfonic acid), when present as a reaction by-product in FD&C Red No. 40, is shown to decompose rapidly in aqueous solutions of the color additive. The decomposition is halted by the addition of sodium borate buffer. Quantitationly liquid chromatography shows that decomposition is nonlinear with time and follows approximate first order kinetics.

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