scholarly journals Rate constants of dichloride radical anion reactions with molecules of environmental interest in aqueous solution: a review

2021 ◽  
Author(s):  
László Wojnárovits ◽  
Erzsébet Takács
Keyword(s):  
Rate Constants ◽  
Radical Anion ◽  
Natural Waters ◽  
Organic Molecules ◽  
Chloride Ions ◽  
Electron Systems ◽  
Electron Transfer Mechanism ◽  
High Concentrations ◽  
The One ◽  
Lower Oxidation

AbstractNatural waters, water droplets in the air at coastal regions and wastewaters usually contain chloride ions (Cl-) in relatively high concentrations in the milimolar range. In the reactions of highly oxidizing radicals (e.g., •OH, •NO3, or SO4•-) in the nature or during wastewater treatment in advanced oxidation processes the chloride ions easily transform to chlorine containing radicals, such as Cl•, Cl2•-, and ClO•. This transformation basically affects the degradation of organic molecules. In this review about 400 rate constants of the dichloride radical anion (Cl2•-) with about 300 organic molecules is discussed together with the reaction mechanisms. The reactions with phenols, anilines, sulfur compounds (with sulfur atom in lower oxidation state), and molecules with conjugated electron systems are suggested to take place with electron transfer mechanism. The rate constant is high (107–109 M-1 s-1) when the reduction potential the one-electron oxidized species/molecule couple is well below that of the Cl2•-/2Cl- couple.

scholarly journals Oxidation of hypotaurine and cysteine sulphinic acid by peroxynitrite

2005 ◽  
Vol 389 (1) ◽  
pp. 233-240 ◽  
Author(s):  
Mario FONTANA ◽  
Donatella AMENDOLA ◽  
Emanuela ORSINI ◽  
Alberto BOFFI ◽  
Laura PECCI
Keyword(s):  
Oxygen Uptake ◽  
Rate Constants ◽  
Ph Value ◽  
Second Order ◽  
Cysteic Acid ◽  
Direct Reaction ◽  
Radical Chain ◽  
Electron Transfer Mechanism ◽  
Order Rate ◽  
The One

Peroxynitrite mediates the oxidation of the sulphinic group of both HTAU (hypotaurine) and CSA (cysteine sulphinic acid), producing the respective sulphonates, TAU (taurine) and CA (cysteic acid). The reaction is associated with extensive oxygen uptake, suggesting that HTAU and CSA are oxidized by the one-electron transfer mechanism to sulphonyl radicals, which may initiate an oxygen-dependent radical chain reaction with the sulphonates as final products. Besides the one-electron mechanism, HTAU and CSA can be oxidized by the two-electron pathway, leading directly to sulphonate formation without oxygen consumption. The apparent second-order rate constants for the direct reaction of peroxynitrite with HTAU and CSA at pH 7.4 and 25 °C are 77.4±5 and 76.4±9 M−1·s−1 respectively. For both sulphinates, the apparent second-order rate constants increase sharply with decrease in pH, and the sigmoidal curves obtained are consistent with peroxynitrous acid as the species responsible for sulphinate oxidation. The kinetic data, together with changes in oxygen uptake, sulphinate depletion, sulphonate production, and product distribution of nitrite and nitrate, suggest that oxidation of sulphinates by peroxynitrite may take place by the two reaction pathways whose relative importance depends on reagent concentrations and pH value. In the presence of bicarbonate, the direct reaction of sulphinates with peroxynitrite is inhibited and the oxidative reaction probably involves only the radicals •NO2 and CO3•−, generated by decomposition of the peroxynitrite-CO2 adduct.

The one- and two-electron reduction of 2-thioriboflavin by radical anions of CO2 and dithiothreitol

1986 ◽  
Vol 64 (1) ◽  
pp. 67-70 ◽  
Author(s):  
Parminder S. Surdhar ◽  
David A. Armstrong ◽  
Vincent Massey
Keyword(s):  
Steady State ◽  
Rate Constants ◽  
Radical Anion ◽  
Pulse Radiolysis ◽  
Continuous Production ◽  
Radical Anions ◽  
Reduction Step ◽  
Equivalence Point ◽  
Electron Reduction ◽  
The One

The one- and two-electron reductions of 2-thioriboflavin with[Formula: see text] and cyclic disulphide anion of dithiothreitol [Formula: see text] have been studied by the steady state γ and pulse radiolysis techniques. The [Formula: see text] radical reacted with 2-thioriboflavin to give the neutral semiquinone (•FlH) and the radical anion (•Fl−) at pH 5 and 10 respectively. The pK of the •FlH radical was determined to be 7.4. In the case of the anion, the 2-thioriboflavin spectrum is similar in shape to that of FAD radical anion, but red shifted by 40–50 nm. Red shifts are also seen in the neutral •FlH form for the 370-nm peak and 580-nm shoulder. However, in addition, there is strong enhancement of the absorbance at 500 nm. The spectrum of 2-thioriboflavin semiquinone produced in the presence of 2–5 mM dithiothreitol was perturbed, as was observed previously for unsubstituted flavin semiquinones in the presence of sulphydryls. The rate constants for the initial one-electron reduction step viz: [Formula: see text] were 4.0 ± 0.5 × 109 M−1 s−1 and 1.3 ± 0.2 × 109 M−1 s−1 at pH 7 and 10 respectively. The corresponding rate for the reaction of [Formula: see text] with 2-thioriboflavin at pH 7 was determined to be 2.4 ± 0.2 × 109 M−1 s−l. The continuous production of [Formula: see text] radicals by γ radiolysis reduced 2-thioriboflavin to the dihydro form, and the flavin was regenerated on the addition of air. The[Formula: see text] radical also effected a two-electron reduction. However, in this case, if the process was taken beyond the equivalence point, the dihydroflavin spectrum was bleached and the oxidized flavin could not be recovered.

scholarly journals Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet

2021 ◽  
Author(s):  
Jon R. Hawkings ◽  
Benjamin S. Linhoff ◽  
Jemma L. Wadham ◽  
Marek Stibal ◽  
Carl H. Lamborg ◽  
...  
Keyword(s):  
Natural Waters ◽  
Inorganic Mercury ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Annual Runoff ◽  
Arctic Ecosystems ◽  
High Mercury ◽  
Southwestern Margin ◽  
High Concentrations ◽  
Dissolved Mercury

AbstractThe Greenland Ice Sheet is currently not accounted for in Arctic mercury budgets, despite large and increasing annual runoff to the ocean and the socio-economic concerns of high mercury levels in Arctic organisms. Here we present concentrations of mercury in meltwaters from three glacial catchments on the southwestern margin of the Greenland Ice Sheet and evaluate the export of mercury to downstream fjords based on samples collected during summer ablation seasons. We show that concentrations of dissolved mercury are among the highest recorded in natural waters and mercury yields from these glacial catchments (521–3,300 mmol km−2 year−1) are two orders of magnitude higher than from Arctic rivers (4–20 mmol km−2 year−1). Fluxes of dissolved mercury from the southwestern region of Greenland are estimated to be globally significant (15.4–212 kmol year−1), accounting for about 10% of the estimated global riverine flux, and include export of bioaccumulating methylmercury (0.31–1.97 kmol year−1). High dissolved mercury concentrations (~20 pM inorganic mercury and ~2 pM methylmercury) were found to persist across salinity gradients of fjords. Mean particulate mercury concentrations were among the highest recorded in the literature (~51,000 pM), and dissolved mercury concentrations in runoff exceed reported surface snow and ice values. These results suggest a geological source of mercury at the ice sheet bed. The high concentrations of mercury and its large export to the downstream fjords have important implications for Arctic ecosystems, highlighting an urgent need to better understand mercury dynamics in ice sheet runoff under global warming.

scholarly journals Rate and Product Studies with 1-Adamantyl Chlorothioformate under Solvolytic Conditions

2021 ◽  
Vol 22 (14) ◽  
pp. 7394
Author(s):  
Kyoung Ho Park ◽  
Mi Hye Seong ◽  
Jin Burm Kyong ◽  
Dennis N. Kevill
Keyword(s):  
Rate Constants ◽  
Isotope Effects ◽  
Ion Pairs ◽  
Carbonyl Sulfide ◽  
Activation Parameters ◽  
Chloride Ions ◽  
Reaction Channels ◽  
Decomposition Pathway ◽  
Solvent Isotope ◽  
Solvent Isotope Effects

A study was carried out on the solvolysis of 1-adamantyl chlorothioformate (1-AdSCOCl, 1) in hydroxylic solvents. The rate constants of the solvolysis of 1 were well correlated using the Grunwald–Winstein equation in all of the 20 solvents (R = 0.985). The solvolyses of 1 were analyzed as the following two competing reactions: the solvolysis ionization pathway through the intermediate (1-AdSCO)+ (carboxylium ion) stabilized by the loss of chloride ions due to nucleophilic solvation and the solvolysis–decomposition pathway through the intermediate 1-Ad+Cl− ion pairs (carbocation) with the loss of carbonyl sulfide. In addition, the rate constants (kexp) for the solvolysis of 1 were separated into k1-Ad+Cl− and k1-AdSCO+Cl− through a product study and applied to the Grunwald–Winstein equation to obtain the sensitivity (m-value) to change in solvent ionizing power. For binary hydroxylic solvents, the selectivities (S) for the formation of solvolysis products were very similar to those of the 1-adamantyl derivatives discussed previously. The kinetic solvent isotope effects (KSIEs), salt effects and activation parameters for the solvolyses of 1 were also determined. These observations are compared with those previously reported for the solvolyses of 1-adamantyl chloroformate (1-AdOCOCl, 2). The reasons for change in reaction channels are discussed in terms of the gas-phase stabilities of acylium ions calculated using Gaussian 03.

scholarly journals CHEMICAL AND BIOLOGICAL INDICATORS FOR EVALUATION OF ARCTIC SOIL DEGRADATION AND ITS POTENTIAL TO REMEDIATION

2021 ◽  
Vol 29 (1) ◽  
pp. 33-39
Author(s):  
Tatiana S. Smirnova ◽  
Elena A. Mazlova ◽  
Olga A. Kulikova ◽  
Ilya M. Ostrovkin ◽  
Adam M. Gonopolsky ◽  
...  
Keyword(s):  
Biological Indicators ◽  
Climatic Conditions ◽  
Chloride Ions ◽  
The Arctic ◽  
Environmental Damage ◽  
Arctic Zone ◽  
Arctic Soils ◽  
Arctic Soil ◽  
Restoration Ability ◽  
High Concentrations

In recent years, significant efforts have been made to accelerate the economic development of the Arctic zone, leading to intense environmental pollution of this region, accompanied by the significant impact of accumulated environmental damage in the region. The solution to these problems is difficult due to the remoteness of these areas and severe climatic conditions. Therefore, it is important to evaluate the potential for restoration of arctic soils. For this purpose, various indicators are used, including biological ones. In the analyzed arctic soil samples, high concentrations of petroleum hydrocarbons (up to 47,000 mg/kg) and chloride-ions (0.10–0.14 wt %) were established. Microbioassay demonstrated a presence of hydrocarbon-oxidizing microorganisms: Penicillium, Azotobacter chroococcum, Bacillus subtilis, Pseudomonas oleovorans. A low enzymatic activity and specific Arctic climate point out a low self-restoration ability of the soil, demonstrated the need for its remediation. The microbioassay with microbial strains identification and soil remediation methods suitable for the Arctic zone were recommended.

A Micropuncture Study of Kidney Function in the River Lamprey Lampetra Fluviatilis Adapted to Sea Water

1980 ◽  
Vol 88 (1) ◽  
pp. 239-248
Author(s):  
A. G. LOGAN ◽  
R. MORRIS ◽  
J. C. RANKIN
Keyword(s):  
Fresh Water ◽  
Kidney Function ◽  
Sea Water ◽  
Chloride Ions ◽  
Water Reabsorption ◽  
Plasma Electrolyte ◽  
River Lamprey ◽  
Micropuncture Study ◽  
Urine Composition ◽  
High Concentrations

Micropuncture techniques have been used to investigate kidney function in lampreys adapted to hyperosmotic media. Plasma electrolyte concentrations were maintained well below corresponding concentrations in the external environment. Urine composition was variable, but generally showed high concentrations of magnesium, sulphate and chloride ions. Lampreys in 50% sea water produced urine which was hypo or iso-osmotic to plasma, whereas those in 100% sea water produced hyperosmotic urine. Urine flow rate in 50% sea water was one tenth of that in fresh water, due to a reduction in filtration rate and an increase in water reabsorption by the kidney. As in fresh water, little if any filtered water was reabsorbed by the proximal segment. Almost 90% of filtered water was reabsorbed by the kidney of 100% sea water lampreys and most of this must have occurred in the distal and collecting segments.

Histamine-induced modulation of olfactory receptor neurones in two species of lobster, Panulirus argus and Homarus americanus

1989 ◽  
Vol 145 (1) ◽  
pp. 133-146 ◽  
Author(s):  
T. A. Bayer ◽  
T. S. McClintock ◽  
U. Grunert ◽  
B. W. Ache
Keyword(s):  
Receptor Antagonist ◽  
Olfactory Receptor ◽  
Single Cells ◽  
Homarus Americanus ◽  
Chloride Ions ◽  
Electrophysiological Recording ◽  
Stimulus Response ◽  
Olfactory Receptor Cells ◽  
Receptor Cells ◽  
The One

In two species of lobster, application of the biogenic amine, histamine (HA), to the soma of olfactory receptor cells suppressed both spontaneous and odour-evoked activity, as shown by electrophysiological recording from single cells. The action of HA was graded, reversible, specific to HA, and had a threshold between 0.1 and 1 mumol l-1. HA increased the conductance of the membrane, primarily to chloride ions. The vertebrate HA receptor antagonist, cimetidine, and the nicotinic receptor antagonist, d-tubocurarine, but not other known vertebrate HA receptor antagonists, reversibly blocked the action of HA. These results suggest that a histaminergic mechanism modulates stimulus-response coupling in lobster olfactory receptor cells and potentially implicate a novel HA receptor, pharmacologically similar to the one recently described in the visual system of flies.

Specific Action of Chloride Ions at High Concentrations on Thermoluminescence of Chloroplasts

1998 ◽  
pp. 1223-1225
Author(s):  
M. K. Solntsev ◽  
V. Tashish ◽  
V. A. Karavaev ◽  
A. M. Kuznetsov
Keyword(s):  
Chloride Ions ◽  
High Concentrations
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