Mark D. Engelmann

The complete dechlorination of DDT by magnesium/palladium bimetallic particles.

The complete dechlorination of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT) by a magnesium/palladium bimetallic system has been accomplished. The reaction takes place under ambient temperature and pressure and mild reaction conditions requiring only 0.25 g of magnesium and 0.3% palladium (wt/wt) to drive the dechlorination of 100 microg DDT (50 ppm in 2 ml). The process is both rapid and complete requiring less than 10 min to attain total dechlorination within the detection limit (approximately 10 pg for DDT) of electron capture detection gas chromatography (GC-ECD). The major product formed, as deduced from mass spectrometry (GC-MS) is the hydrocarbon skeleton, 1,1-diphenylethane. This technology may allow for the development of an economic and environmentally benign method of DDT remediation.

Simultaneous determination of total polychlorinated biphenyl and dichlorodiphenyltrichloroethane (DDT) by dechlorination with Fe/Pd and Mg/Pd bimetallic particles and flame ionization detection gas chromatography

Abstract Simultaneous measurement of total dichlorodiphenyltrichloroethane (DDT, technical mixture) and polychlorinated biphenyl (PCB-Aroclors 1248 and 1260) is facilitated by quantitative dechlorination to diphenylethane and biphenyl. The two-stage dechlorination reaction utilizes a palladium catalyst deposited onto iron and magnesium particles. The treatment has the advantage of converting the complex chromatographic pattern that arises from the multiple congeners and degradation products of PCB and DDT into peaks corresponding to their representative hydrocarbon skeletons. The limit for quantitative measurement (LOQ) using this treatment and GC-FID analysis is 40 parts-per-billion (ppb, μg/l) for Aroclor 1260 and 100 ppb for DDT with a linear response extending to 100 times the LOQ. The calibration was successfully tested with triplicate water samples fortified at 15 (DDT) and 10 (Aroclor 1260) times the LOQ. Accuracy (mean percent) and precision (percent relative standard deviation) were 92% and 6.2% for DDT and 96% and 5.2% for Aroclor 1260. Accuracy and RSD for 35 ppm triplicate spiked soil samples were 76% and 18% for Aroclor 1260 and 68% and 26% for DDT. These results are comparable to the published single laboratory results for EPA method 8082 ‘Polychlorinated Biphenyls by Gas Chromatography’. However, the single laboratory results for EPA method 8081A ‘Organohalide Pesticides by Gas Chromatography,’ failed to resolve DDT and therefore could not be compared with this method.

Measurement of Fukushima aerosol debris in Sequim and Richland, WA and Ketchikan, AK

Aerosol collections were initiated at several locations by Pacific Northwest National Laboratory (PNNL) shortly after the Great East Japan earthquake of May 2011. Aerosol samples were transferred to laboratory high-resolution gamma spectrometers for analysis. Similar to treaty monitoring stations operating across the Northern hemisphere, iodine and other isotopes which could be volatilized at high temperature were detected. Though these locations are not far apart, they have significant variations with respect to water, mountain-range placement, and local topography. Variation in computed source terms will be shown to bound the variability of this approach to source estimation.

Optimizing Separation of Iodine from Halogen Interferences in Preparation for TIMS Analysis

Low-level analysis of radioiodine performed by TIMS requires an initial chemical separation from interfering higher electron-affinity halogens. Experiments using 125I and 36Cl tracers have shown that iodide can be selectively oxidized and purged from solution while the chloride remains in the solution. A systematic investigation of the experimental factors that affect the oxidation and transfer of iodine along with the separation of iodide from chloride has been completed. Experimental design was used to determine the optimum experimental conditions by obtaining a better understanding of factor affects and interactions. Factors such as gas purge rate, experiment run time, and oxidant concentration were simultaneously studied in a central composite design of experiments and response surfaces were generated from results. Optimizing experimental factors resulted in improved iodide oxidation and transfer efficiencies, halogen separation, and shorter analysis times.