Werner R. Haag

Rate constants for direct reactions of ozone with several drinking water contaminants

Abstract Rate constants for the direct reactions of ozone with 45 potential organic drinking water contaminants, including solvents, haloalkanes, esters, aromatics and pesticides (such as alachlor, aldicarb, atrazine, carbofuran, 2,4-dichlorophenoxyacetic acid, endrin, glyphosate, etc.), have been measured in water in the presence of hydroxyl radical scavengers to minimize interfering radical chain reactions. The data demonstrate, again, the electrophilic nature of the ozonation reaction. In addition, for complex molecules, steric factors are important in limiting reactivity. The zwitterionic compound glyphosate exhibits a complex pH dependence that is explained by the inductive effect of side-chain protonation on the basicity of the amine reaction center. Rate constants for ozone consumption differ from those for compound consumption by an amount presumably equal to the reaction stoichiometry.

RATE CONSTANTS FOR INTERACTION OF 1O21Δg) WITH AZIDE ION IN WATER

Abstract— The rate constant for quenching of 1O2 by azide ion in water was determined to be (5.0 ± 0.4) × 108M−1 s−1 using a variety of sensitizers (including humic acids) and 1O2 acceptors. The apparent second‐order rate constant decreases with pH below pH 5.5 in accordance with the protonation of azide ion to form hydrazoic acid (pKa= 4.6). Quenching by hydrazoic acid is at least 2 orders of magnitude slower than by azide ion. Greater than 99% of all interactions between 1O2 and azide ion involve physical quenching rather than chemical reaction. Humic acid triplets are not significantly quenched by azide ion at concentrations less than 2 mM, allowing azide ion quenching to be used as a diagnostic test for the intermediacy of 1O2 in photosensitized oxidations in natural surface waters.

Fate of diethylene glycol dinitrate in surface waters

Abstract The environmental fate of diethylene glycol dinitrate (DEGDN) in surface waters is dominated by photolysis with surface half-lives ranging from 15 days in summer to 59 days in winter at 40°N. The environmental quantum yield is 0.18. Photolysis of DEGDN initially forms nitrate ion and 2-hydroxyethyl nitratoacetate; the latter photolyzes further to 1- and 2-carbon acids and additional nitrate. DEGDN biotransforms with a second-order rate constant of 3.9 × 10−11 mL cell−1 h−1, corresponding to a half-life of about 2 years in a typical surface water. Intermediate biotransformation products were observed but were further transformed and did not accumulate. DEGDN is expected to move readily through soils because it had low soil sorption coefficients Kp of 2 and 0.8 g mL−1 on EPA-5 and EPA-18 sediments, respectively. Abiotic reduction occurred rapidly in lake and river sediments but the importance of this process for overall fate is difficult to quantitate. Other fate parameters measured at 25°C were a water solubility of 3900 mg L−1, octanol/water partition coefficient of 9.6 (dimensionless), Henrys constant of