References

Doyle, M. Stroud, and D. Wakelin. 2001. Methods for the stable isotopic analysis of chlorine in chlorate and perchlorate compounds. Analytical Chemistry 73 4946-50. Albarede, F., and B. Beard. 2004. Analytical methods for non-traditional isotopes. In Geochemistry of non-traditional stable isotopes, eds. C. M. Johnson, B. L. Beard, and F. Albarede, 113-52. Washington DC The Mineralogical Society of America. Algeo, T. J., and T. W. Lyons. 2006. Mo-total organic...

Isotopic analysis of biomarkers

Biomarkers are compounds specific to a particular organism or group of organisms that can be isolated and measured to allow the study of both microbial processes specific to that organism or group of organisms and the study of larger scales of population and community changes. The microbial formation of biological components from parent carbon can be assessed under aerobic conditions using isotopic fractionation. Bacteria synthesize proteins from amino acids and carbohydrates and lipids that...

Selenium

Selenium has six stable isotopes 74Se (0.889 ), 76Se (9.366 ), 77Se (7.635 ), 78Se (23.772 ), 80Se (49.607 ) and 82Se (8.731 ). While Se is an essential element for all living things, it can also be toxic to organisms (Cooper and Glover 1974 Ganther 1974 Lemly 1998 Skorupa 1998). Selenium is a constituent of most shales Figure 12.4a) and the soils that form from them, and it is concentrated in evaporative waters so it is a common contaminant of surface and groundwaters in arid environments....

Biodegradation And Bioremediation

Biodegradation is perhaps the most important process on earth. Without biodegradation, the organic matter synthesized by plants and other lithotrophic organisms would accumulate and the carbon dioxide in the atmosphere would not be regenerated. Biodegradation and biotransformation include the cycling of important elements, including carbon and nitrogen that are both essential molecular building blocks and components of contaminants. Without biodegradation, nutrients fixed in organic matter...

Index

Abbotsford-Sumas regional sand and gravel aquifer, BMPs in, 222 Abiogenic systems, 169 Abiotic and biotic processes, distinguish between, 18 Accelerator mass spectrometry (AMS), 358 Acetate fermentation and CH4 production, 171-172 by Methanosaeta thermophila, 172 Aceticlastic methanogenesis, 170 Acetylene block method, 334 Acinetobacter sp., benzene degraded by, 149 Advection-dispersion theory, 50 Advective transport of water and NAPL, 297 Aerobic benzene biodegradation, 149 Aerobic...

Mass Fractionation Processes

Stable isotopes are fractionated in nature during physicochemical and biological reactions by mass-dependent and mass-independent processes. Mass-dependent isotope fractionation occurs because of small changes in the bond energies of molecules that contain isotopes of an element of differing mass. Vibrational frequencies for molecules containing the isotope of greater mass are relatively low and this makes them slightly more stable. The effect of mass-dependent fractionation can be readily...

Modeled example scenarios

In this section the model will be applied in five scenarios that were selected and ordered with increasing complexity. The first scenario (9.5.1) is describing transient diffusion of CO2 in a column filled with dry sand, devoid of biological reactions and kinetic isotope fractionation, and thus, only diffusion leads to fractionation of CO2. Subsequently, steady-state scenarios including kinetic isotope fractionation in 1D (9.5.2 and 9.5.3) and 2D (9.5.4) are discussed, and in the end, a...

Type of information obtained by isotopes

The variations in the abundance of stable isotopes in natural compounds or anthropogenic pollutants can be used in different ways for assessing different types of information. These types can be grouped into at least seven classes. The first possibility is to identify sources of compounds by direct analysis of the compound in a given environment and compare the isotopic abundance to a number of potential sources that have distinct but constant isotope abundances. A prerequisite for this...

Fe Isotope Composition of Iron Oxides and Fluids

Recent research regarding the isotopic composition of iron oxides highlights that iron oxides tend to have low 56Fe 54Fe ratios (Emmanuel et al. 2005 Teutsch et al. 2005 Severmann et al. 2006 Staubwasser, von Blanckenburg, and Schoenberg 2006). Because iron oxides have high 56Fe 54Fe ratios relative to aqueous Fe(II), iron oxides with low S56Fe values must form from fluids that experience complete oxidation or those with unusually low S56Fe values. Based on partial leaching studies of semiarid...

Sulfur isotope fundamentals

Sulfate is a major constituent of many surface waters and groundwaters. Identifying potential sources and the biogeochemical history of dissolved sulfate is often of significant interest for water resource managers, since sulfate may cause acidification (Reuss and Johnson 1986), contributes to the hardness of water, and is an important terminal electron acceptor in reductive processes (Appelo and Postma 2005). For the delineation of various sources of sulfate in the hydrosphere, the application...

Introduction

This chapter discusses how isotope data can be used to demonstrate, and in some cases, quantify the extent of contaminant transformation at the field scale in the context of natural attenuation or engineered remediation. Furthermore, it discusses how isotope data can help to differentiate between different sources of the same contaminant. When implementing natural attenuation or engineered remediation to remediate contaminated aquifers, there is usually a need to demonstrate occurrence of...

Principles Of Isotope Analysis

Elemental Analyzer Setup

The isotope ratios of light elements are most commonly measured with gas-source magnetic sector mass spectrometers often denoted as isotope ratio mass-spectrometers (IRMS). Their measurement principle is different from that of mass-spectrometers commonly used for identification of organic compounds. The first type of these instruments was developed in 1947 by Alfred Nier. With these instruments, the molecules of interest are introduced in gaseous form into the ion source, are ionized, and...

Incorporation of isotope fractionation into reactive transport models

All calculation procedures introduced so far are based on the Rayleigh equation. While these calculations can be carried out rapidly and provide insight in the magnitude of contaminant degradation, they have their limitations. They only apply to one step degradation processes. Furthermore, degradation has to be the only fractioning process, which is usually the case in groundwater but not in the unsaturated zone where diffusion can fractionate isotopes as well (Bouchard et al. 2008). Finally,...

Case studies

The above described principles of isotope distribution in the sulfur cycle have been utilized in numerous case studies throughout the last five decades to determine sources and the biogeochemical history of sulfur compounds in terrestrial and aquatic ecosystems (e.g., Krouse and Grinenko 1991). The following sections discuss selected examples with specific relevance to microbial conversions in the hydrosphere. 7.10.1 Tracing Sulfate During Recharge Atmospheric deposition contains sulfate...

Compoundspecific isotope analysis CsiA

2.4.1 Coupling with Gas Chromatography (GC) The coupling of gas chromatographs with an IRMS makes it possible to analyze isotope ratios of individual compounds in complex mixtures (Matthews and Hayes 1978 Meier-Augenstein 1999). Such methods are usually referred to as compound-specific isotope analysis (CSIA). The instrument is frequently denoted as isotoperatio-monitoring gas chromatography-mass spectrometry (IRM-GCMS) or more commonly gas chromatography isotope-ratio mass spectrometry...

Ramon Aravena

University of Waterloo, Ontario, Canada Taylor & Francis Group, an informa business Taylor & Francis Group, an informa business 6000 Broken Sound Parkway NW, Suite 300 2010 by Taylor and Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number 978-1-56670-661-2 (Hardback) This book contains...

Source fingerprinting

In industrialized and urbanized area, there are often several sources of the same contaminant. For example, there may be multiple spills of chlorinated solvents such as PCE or several gas stations potentially with spills containing MTBE. Due to the complexity of transport processes in the subsurface, it can be difficult to attribute downgradient contamination to a specific source. Industrial solvents from different manufacturers or petroleum hydrocarbons of different origin have frequently...

Isotopic composition of organic compounds and other carbon pools

In order to assess the impact of aerobic degradation on isotopic signatures, the background signature of the atmosphere and other carbon sources, such as natural OM and environmental contaminants, must be known. Figure 5.1 illustrates the variation in carbon isotopic signatures expressed in 8 notation in units of per mil ( e) relative to the Vienna Pee Dee Belemnite (VPDB) standard (see Chapter 1) of some natural carbon substances in the environment. CO2 resides in and exchanges between large...

Radiocarbon And Methane Ch4

An important constraint in tracing sources of carbon in biogenic and fossil CH4 accumulations has been the use of radiocarbon (expressed in percent Modern Carbon pMC ). Best estimates suggest that between 15 and 21 of global CH4 emissions are derived from radiocarbon dead sources, such as fossil fuels, organic matter that is > 40 kyr old, and abiogenic (geological) CH4 (Stevens 1988 Wahlen 1994). Measurement of 14CH4 in local environments also provides useful information about carbon sources...

Natural Abundance Of Stable Isotopes

The original isotopic compositions of solar systems are a result of nuclear processes in stars and planets. Isotopic compositions in terrestrial environments change gradually by the processes of radioactive decay, cosmic ray interactions, mass-dependent fractionations that accompany inorganic and biological reactions, and anthropogenic activities such as the processing of nuclear fuels, reactor accidents, and the testing of nuclear weapons. Stable isotopes are nuclides that do not appear to...

Discovery Of Isotopes

Until the late nineteenth century, chemists were convinced that each chemical element has a distinct and integer molar mass. The elements were ordered in the periodic table of elements according to their molar masses, and minor deviations from integer molar masses were thought to be caused by analytical errors. Only after the discovery of radioactivity by Henry Becquerel and Marie and Pierre Curie at the end of the nineteenth century (Nobel Prize in physics in 1903), the ideas about the nature...

Nitrogen Cycle

The isotope composition of the main nitrogen pools involved in nitrogen cycling in groundwater (soil organic nitrogen, ammonium, and nitrate) is imprinted by the isotope composition of the sources (internal and external) and processes that affect these pools in the unsaturated and saturated zones. The external sources are fertilizers and nitrogen derived from animal and domestic waste. In some specific areas of the world, soil nitrogen (internal source) has been shown to be an important source...

Aerobic biodegradation of chlorinated hydrocarbons

As was observed for toluene degradation, degradation pathways and initial enzymatic reactions are also important considerations for CSIA fractionation studies of chlorinated contaminants. Chlorinated organic contaminants can be degraded cometabolically to carbon dioxide by methane oxidizing bacteria. These bacteria are present in many different aerobic soil and sediment environments (Hanson and Hanson 1996 Brungard et al 2003). Methanotrophs are gram-negative bacteria that are classified based...

Radiocarbon notation

The term radioactivity was coined by Marie Sklodowska Curie based on her research with radium. The Curie (1 Ci 3.7 x 1010 disintegrations per second) was initially used as the unit of radioactivity and later replaced by the SI unit Becquerel (1 Bq one disintegration per second). Both units of radioactivity are based on disintegrations per time during radioactive decay. Because radiocarbon has been used in many fields to examine ancient and modern carbon, a standardization of the nomenclature...

International standards

The measurement of absolute isotope ratios or abundances is not easily done and requires very sophisticated mass spectrometric equipment (see Chapter 2). However, for most studies, the monitoring of relative variations in stable isotope concentrations rather than absolute abundances provides the necessary information about the processes. By measuring a known reference material under the same conditions as our sample, we can then express isotopic concentrations as the difference between sample...

Calculation of isotope ratios

The IRMS system provides information about ratios of isotopologues (identical molecules with a different isotopic composition) relative to the reference gas from which the isotope ratio of elements in the molecules are calculated. The calculation procedure is discussed in detail for CO2, probably the most commonly measured molecule. The basic information obtained from the IRMS are electrical signals proportional to the amount of ions with specific masses (44, 45 and 46 in case of CO2) reaching...

Methane in Landfills

Landfilling is the main method for solid waste disposal in North America. Environmental hazards associated with landfills include CH4 and contaminated liquid production (i.e., leachate) both of which could migrate from the landfill into surrounding environments (Farquhar 1988 Abaci, Edwards, and Whitaker 1993 Robertson, Murphy, and Cherry 1995). Although modern landfills are typically designed with a low permeability liner and leachate collection and gas extraction systems, some degree of...

Expressing And Quantifying Isotope Fractionation

The abundance of different isotopes in a system are usually reported as isotope ratio R or more commonly in the delta notation relative to the isotope ratio of reference material (see Chapter 2) where HA is the amount of heavy isotope in the system, LA the amount of the light isotopes, and Rstd the isotope ratio of the reference material. Since variations of isotope ratios are often small, the 5-values are usually expressed on a per mill scale by multiplication with 1000. For example a value of...

Isotope fractionation during transformation processes

For reactive processes, the rate constant or equilibrium constant frequently depends on which isotope is present at the reactive position, which is denoted as an isotope effect. As a result of this isotope effect, isotopes become unevenly distributed among reactant and products. In other words, isotope fractionation occurs. This section discusses the origin of isotope effects during transformation processes and illustrates in semiquantitative terms the factors that control the magnitude of...

Isotope fractionation during transport processes

Under saturated conditions, transport of dissolved compounds occurs by advection and dispersion e.g., Freeze and Cherry 1979 . Advection corresponds to the displacement of molecules with the movement of the water. In the classical advection-dispersion theory, it is usually assumed that the advective displacement of molecules takes place with the average groundwater flow velocity within some representative aquifer volume. However, not all molecules cover the same distance in a given amount of...

Isotope fractionation during transformation of petroleum hydrocarbons

Similar to chlorinated solvents, petroleum hydrocarbons are of environmental concern. Petroleum hydrocarbons may enter the environment via accidental fuel spills or at industrial sites. Among them, the monoaromatic hydrocarbons benzene, toluene, ethylbenzene, and xylene isomers BTEX belong to the list of priority pollutants of the U.S. Environmental Protection Agency US-EPA 1999 . These putatively mutagenic and carcinogenic substances make up the bulk gt 50 wt of the water-soluble fraction of...