E. W. B. De Leer

Findings supporting the natural formation of trichloroacetic acid in soil

Abstract The concentrations of trichloroacetic acid (TCAA) in soil and of chlorinated solvents in soil air from simultaneously taken samples from four sites are presented. The data show that there is a significant positive correlation between the concentrations of TCAA and chloroform - but not between TCAA and other chlorinated solvents — in soil. The calculated half-life of TCAA shows that the contribution of decarboxylation to the chloroform concentration in soil is negligible. Since TCAA and chloroform were found to be formed from humic acids in the chloroperoxidase (CPO)-mediated reaction and CPO activity has been detected in soil, the observed correlation between the concentrations of TCAA and chloroform provides novel support for the hypothesis that TCAA is formed naturally in soil.

Mass balance of trichloroacetic acid in the soil top layer.

Since the ban on the use of trichloroacetic acid (TCAA) as a herbicide in several countries, TCAA is still found ubiquitously in the environment. The presence of TCAA nowadays is suggested to originate mainly from the atmospheric degradation of tetrachloroethene. Our mass balance calculations indicate that this may be true for the presence of TCAA in the atmosphere. However, our mass balance calculations also provide tentative evidence for the formation of TCAA in soil. If our calculated production fluxes are realistic estimates, a very large source of TCAA in soil has been identified.

“De novo”-synthesis of chlorinated biphenyls, dibenzofurans and dibenzo-p-dioxins in the fly ash catalyzed reaction of toluene with hydrochloric acid

Toluene is converted into benzaldehyde and halogenated aromatic oxidation products in an air atmosphere at 425 °C with fly ash from a municipal waste incineration plant as the catalyst. Several halogenated products such as chlorinated and brominated benzenes, biphenyls and traces of PCDDs/PCDFs could be detected under these conditions, resulting from the reaction of metal chlorides and hromides present on the surface of the fly ash. The addition of a “chlorine” source to the reaction gases in the form of trichloroethylene or hydrogen chloride dramatically increased the production of PCBs, PCDDs/PCDF5 and other chlorinated aromaticcompounds, giving evidence for a “de novo” synthesis of PCBs and PCDDs/PCDFs. A reaction pathway, based on the initial oxidation of toluene to benzaldehyde as the key intennediate, followed by chlorination and condensation reactions is proposed.

Origin of system peaks in single-column ion chromatography of inorganic anions using high pH borate—gluconate buffers and conductivity detection

Abstract Single-column ion chromatography of inorganic anions with borate—gluconate buffers and conductivity detection produces system peaks as the result of complexation of polyvalent cations such as calcium. The complexes show retention due to ion-exchange and/or reversed-phase mechanisms. The system peaks can be avoided by treating the sample with a cation exchanger which replaces the polyvalent cations with sodium ions.

Thermal Methods Developed in the Netherlands for the Cleaning of Contaminated Soil

Four different processes for the thermal decontamination of soil have been developed in The Netherlands. Three processes make use of rotary tube furnaces with different combinations of direct and indirect heating, followed by an incineration of the volatilized products. In the direct heating processes the flames are in direct contact with the contaminated soil, while in the indirect heating process the soil is in contact with the heated wall of the furnace only. The indirect heating process uses an inert gas atmosphere. The fourth process uses a fluidized bed furnace with a temperature of 800–900 C and a freeboard for the incineration of the residual volatilized products.

Rearrangements and hydrogen—deuterium exchange in ferrocenylcarbenium ions

Abstract The rearrangement of the t-butyl group in t-butylferrocenyl carbenium ions (VI) and the hydrogen—deuterium exchange in the methyl group of methylferrocenyl carbenium ions (XVI) has been studied. The reaction rates depend on the size of the substituents at the carbenium ion center, an increase in the size of the substituents causing an increase in the rate. This effect is attributed, on the basis of the Gleiter and Cais models of ferrocenyl substituted carbenium ions, to increased steric hindrance between the substituents and the unsubstituted cyclopentadienyl ring.

Progress in the Treatment of Soils Contaminated with Organochlorine Compounds. A Comparison between the Netherlands and the USA

The principle of thermal soil decontamination is simple. A contaminated soil is heated to temperatures of 400-700 °C, which is sufficient to evaporate or to pyrolyse the organic contaminants. The gaseous products are removed by convection and the residual soil is ready for reuse after cooling and moistening.

Rapid Screening of Pollutants in Soil by Curiepoint Pyrolysis/Evaporation Gas Chromatography-Mass Spectrometry

The qualitative and quantitative analysis of pollutants in soil and sediments is an expensive and time consuming task since each group of anthropogenic compounds requires an other analytical approach. Therefore some sort of rapid screening of the soil or sediment sample as such for polluting components is very desirable.