Isotope Applications in Environmental Investigations

Table of Contents . Chapter I Introduction -This introductory chapter provides definitions, nomenclature, analytical techniques, and standard equations for stable and radioisotopes. Introduction Stable isotopes Definitions Nomenclature Analytical techniques Abundances Table of abundances for commonly used elements Fractionation Rayleigh model Mixing equations Conservative tracers Concentration-dependent mixing Radioisotopes Definitions Nomenclature Analytical techniques Half-life Table of half-lives of commonly utilized isotopes Age dating . . Chapter II Hydrology - This chapter presents basic isotope techniques applied in hydrology studies including oxygen and hydrogen isotopic composition of precipitation, surface water hydrology including two- and three-component hydrograph separation, and groundwater hydrology including recharge processes, age dating, and estimating flow paths and flow rates. Isotope techniques presented will be relevant to typical investigative practices for environmental investigations. Precipitation Oceanic evaporation Altitude and latitude effect d18O and dD meteoric water line Evaporation deviation from meteoric water line Surface water Hydrograph separation One tracer - two sources Two tracers - three sources Groundwater Recharge Age dating Tritium and tritium-helium T-3He Sulfur - 35S Carbon - 14C Chlorine - 36Cl Other tracers Si, Ar, and Kr Sulfur hexafluoride CFCs Flow paths and flow rates Introduced tracers Noble gases Sulfur hexafluoride Inorganic salts Groundwater - Surface water interactions 222Rn and radium Sediment Age Dating 210Pb 137Cs . . Chapter III Geochemistry - This chapter presents typical isotope techniques that can be used for evaluating geochemical processes in surface water and groundwater. Isotopes can provide valuable information regarding oxidation and reduction processes. In turn, these important geochemical processes can dramatically affect the fate and transport of contaminants in the environment. A solid understanding of site geochemistry is important for designing appropriate remedial approaches. In addition, when present at sufficiently high concentrations, typical geochemical indicator parameters, such as nitrate, sulfate, and methane can be considered contaminants in and of themselves. Therefore, this chapter will also present isotope methods for discriminating sources of nitrate, sulfate, and methane in surface water and groundwater. General geochemistry (short intro - contaminant degradation perspective) Oxidation-reduction processes ORP Nitrate reduction d15N and d18O for evaluating nitrate reduction and sources of nitrate Sulfate reduction d34S and d18O for evaluating sulfate reduction and sources of sulfate Methanogenesis dD and d13C for evaluating methanogenesis and sources of methane . . Chapter IV Petroleum Hydrocarbons - This chapter presents typical isotope applications for identifying sources of petroleum hydrocarbons in the environment and for demonstrating degradation and discriminating degradation pathways. This chapter will also provide a brief introduction of other standard petroleum hydrocarbon fingerprinting techniques. Petroleum hydrocarbon fingerprinting techniques Chromatograms for identifying fuel types PAH fingerprinting Isotope fingerprints using dD and d13C Bulk Compound-specific isotope analysis Typical ranges of dD and d13C values Source discrimination Demonstrating degradation Aerobic and anaerobic degradation of petroleum hydrocarbons Typical isotopic shifts during contaminant degradation processes Petroleum hydrocarbons Select additives including MtBE, TBA, and 1,2-dichloroethane Identifying degradation pathways Methane and other light hydrocarbons MtBE Incorporating isotope monitoring for evaluating efficacy of active remediation Incorporating isotope monitoring in Monitored Natural Attenuation remedies Importance of including assessment of potential sources as well as potential degradation when using isotopes for either source discrimination or demonstrating degradation, i.e., processes are coupled isotopically. . . Chapter V Chlorinated Solvents and Other Organic Constituents - This chapter presents typical isotope applications for identifying sources of chlorinated solvents in the environment and for demonstrating degradation of chlorinated solvents. This chapter will also provide a brief introduction of other standard chlorinated solvent fingerprinting techniques. Chlorinated solvent fingerprinting techniques Ratio analyses Other techniques Isotopic analyses Bulk isotope analyses - d37Cl Compound-specific isotope analyses - dD and d13C (progress of d37Cl?) Typical isotopic composition of parent (manufactured) compounds Demonstrating degradation Aerobic and anaerobic degradation of chlorinated solvents Degradation reaction pathways Chlorinated ethenes: PCE à TCE à DCE à VC Chlorinated ethanes: PCA à TCA à DCA à CA and TCA à DCE à VC Typical isotopic shifts during contaminant degradation processes Incorporating isotope monitoring for evaluating efficacy of active remediation Incorporating isotope monitoring in Monitored Natural Attenuation remedies Other organic constituents 1,4-dioxane PCBs Importance of including assessment of potential sources as well as potential degradation when using isotopes for either source discrimination or demonstrating degradation, i.e., processes are coupled isotopically. . . Chapter VI Inorganic Constituents - This chapter presents typical isotope applications for identifying sources and transformations of environmentally-relevant inorganic constituents in the environment. A short description of the relevance of each of the elements and compounds to environmental investigations will be provided. Metals Boron Discriminate sources of boron Chromium Discriminate sources of chromium Demonstrate reduction of chromate Copper Discriminate sources of copper Zinc Discriminate sources of zinc Mercury Discriminate sources of mercury Evaluate microbial cycling Lead Discriminate sources of lead Uranium Discriminate sources of uranium Demonstrate microbial reduction of oxidized uranium species Other inorganic constituents Perchlorate Discriminate sources of perchlorate d17O, d18O, and d37Cl Distinguish between natural and anthropogenic perchlorate Demonstrate degradation . Chapter VII Methods for Field Sampling - This chapter presents techniques for sample collection and preservation including mass and/or volume of sample required, container types, preservation and shipping requirements, and practical hold times for analysis as well typical laboratory turn-around times for data reporting. Oftentimes, samples for isotope analyses can be collected during routine environmental investigations, then held for analysis pending results from more standard laboratory analysis techniques.. . References. Index