George R. Helz

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Molybdenum is a nutrient important for a variety of biological functions, most notably nitrogen fixation. Molybdenum availability is limited through sorption reactions, particularly in environments rich in sulfide minerals. This study examines the sorption of two major molybdenum species, molybdate (MoO4(2-)) and tetrathiomolybdate (MoS4(2-)), on synthetic(More)
1978,32, 316-319. Dressen, D. R.; Gladney, E. S.; Owens, J. W.; Perkins, B. L.; Wienke, C. L.; Wanger, L. E. Environ. Sci. Technol. 1977,11, 1017-1019. Dudas, M. J. Environ. Sci. Technol. 1981, 15, 840-843. Shannon, D. G.; Fine, L. 0. Environ. Sci. Technol. 1974, 8, 1026-1028. Kanapilly, G. M. Health Phys. 1977, 32, 89-100. Kanapilly, G. M.; Raabe, 0. G.;(More)
Anthropogenic influences on trace element profiles in dated sediments from estuaries have been often documented, with the vast majority of studies focusing on a short list of high-abundance trace elements. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) provides a new approach that minimizes sample preparation and contamination while(More)
In aquatic ecosystems, availabilities of Fe, Mo and Cu potentially limit rates of critical biological processes, including nitrogen fixation, nitrate assimilation and N2O decomposition. During long periods in Earth's history when large parts of the ocean were sulfidic, what prevented these elements' quantitative loss from marine habitats as insoluble(More)
Dechlorination by sulfur dioxide or other S(IV) compounds is employed to protect aquatic wildlife from toxic residual chlorine in wastewatertreatment plant effluents. Tests a t two wastewater treatment plants show that dechlorination removes 87-98% of residual chlorine but that a remainder, which exceeds regulatory limits, is very slowly reduced. Judging(More)
High concentrations of H2O2 are being tested for in situ oxidation and remediation of buried organic contaminants in soils and groundwater. Peroxide is being considered as a direct chemical oxidant in Fenton-type reactions or as a source of oxidizing equivalents in bioremediation schemes. How H2O2 affects the oxidation state and solubility of Cr(III) and(More)
Two years ago this journal published an article entitled "The Chlorination Question," which reviewed a conference at which the latest research had been presented on topics such as ecosystem damage from discharges of chlorinated sewage and power plant cooling water ( / ) . A growing movement is now under way in the U.S. to install dechlorination facilities,(More)
Received for review February 1,1982. Accepted August 2,1982. This work was supported by subcontract T-64167197-030 from Battelle Columbus Laboratories and EPA Contract 68-01 -6325. Although the research described in this article has been funded wholly or in part by the US. Environmental Protection Agency through Contract 68-01-6325 to SRI International, it(More)
Inorganic and organic chloramines pose a threat to aquatic ecosystems that are exposed to discharges of treated and disinfected wastewater. Conventionally practiced dechlorination with sulfite reduces the most refractory organic chloramines too slowly to produce wastewater effluents that meet current ecosystem protection criteria in the United States (i.e.(More)
Liquid chromatographic (LC) measurement of individual N-chloramines, which are key byproducts of wastewater and drinking water chlorination, could lead to more effective control of water disinfection. Such measurements are challenging because of analyte instability. A detector selective for N-chloramines is constructed based on postcolumn derivatization(More)