Stable Hydrogen Isotope Ratios Research Articles

A 10-yr record of stable isotope ratios of hydrogen and oxygen in precipitation at Calgary, Alberta, Canada

Short-term (0.5–3 d) precipitation samples were collected from January 1992 to December 2001 in Calgary, Alberta, Canada, and the stable isotope ratios of hydrogen (2H/1H) and oxygen (18O/16O) for these samples were determined. The 10-yr amount-weighted average δ2H and δ18O values of precipitation were −136.1° and −17.9°, respectively. Consistent with International Atomic Energy Agency (IAEA) established practice, the following local meteoric water line (LMWL) for Calgary was derived using amount-weighted monthly average δ2H and δ18O values: δ2H = 7.68 δ18O −0.21 (r2= 0.96, n= 104). The correlation equation between δ2H and δ18O values from individual samples was found to be δ2H = 7.10 δ18O −13.64 (r2= 0.95, n= 839), which is different from the LMWL, exhibiting lower slope and intercept values. A comparison of δ2H and δ18O correlation equations with temperature during precipitation events showed a trend of decreasing slopes and intercepts with increasing temperature. Our data suggest that this is caused by incorporation of moisture derived from evaporation from water bodies and soils along the storm paths and by secondary evaporation between the cloud base and the ground during precipitation events. These processes compromise the usefulness of d-excess values as an indicator for the meteorological conditions in the maritime source regions. The δ18O temperature dependence at Calgary was found to be ⊼ 0.44°¼C−1. The study shows that short-term sampling of individual precipitation events yields valuable information, which is not obtainable by the widely used monthly collection programs.

田面水の水素・酸素安定同位体比とそれに及ぼす蒸発の影響

田面水の水素・酸素安定同位体比とそれに及ぼす蒸発の影響

MIGRATORY MOVEMENTS OF SHARP-SHINNED HAWKS (ACCIPITER STRIATUS) CAPTURED IN NEW MEXICO IN RELATION TO PREVALENCE, INTENSITY, AND BIOGEOGRAPHY OF AVIAN HEMATOZOA

Abstract Previous interspecific studies have shown that migratory birds have a higher prevalence of blood parasites than nonmigratory birds. It is thought that birds that move greater distances are exposed to a larger parasite fauna, because of uneven distribution of vectors that carry such parasites. Current hypotheses also suggest that the stress of migration may allow parasites to persist, by weakening the immune system and allowing latent infections to recur. We captured migrating hatching-year Sharp-shinned Hawks (Accipiter striatus) in New Mexico and estimated natal latitudes of each individual by analyzing stable-hydrogen isotope ratios of feathers. That enabled us to estimate distances traveled up to point of capture. We also collected blood to quantify hematozoan infection prevalence and intensity. We related distance traveled to prevalence and intensity of hematozoan infections. Contrary to previous hypotheses, our results show no relationship between distance traveled by migrants and prevalence...

Comparative equilibration and online technique for determination of non-exchangeable hydrogen of keratins for use in animal migration studies

Stable hydrogen-isotope ratios (δD) of keratin provide a novel means for tracking geographical movements of birds and other species. Here we describe a rapid, low cost, analytical approach to facilitate online continuous-flow isotope-ratio mass spectrometry (CF-IRMS) δD analyses of keratins (120-160 samples per day) through the use of calibrated keratin working standards and "comparative equilibration" to correct for the effects of moisture on exchangeable hydrogen. It is anticipated that this analytical approach and CF-IRMS will greatly aid in providing cost effective and directly comparable δD results on keratins and feathers among various laboratories and researchers involved in animal migration studies.

Chemical and isotopic properties of kukersites from Iowa and Estonia

Kukersite samples from Estonia and Iowa were analyzed for elemental composition, functional group distribution, and carbon and hydrogen stable isotope ratios. The elemental and hydrogen isotope values, together with other analytical data, suggest a higher thermal maturity for the Iowa kukersite. The wide carbon isotopic range of 9.3‰ among kukersites, with unusually negative δ13C values reaching −33.2‰, indicates isotopically variable carbon sources for production of biomass, and thus major paleoceanographic differences between the environments supporting biosynthesis.

Variation in Hydrogen Stable-Isotope Ratios Between Adult and Nestling Cooper's Hawks

AbstractHydrogen stable-isotope analysis of feathers is an increasingly popular method for estimating the origins of migrating and wintering birds. Use of this method requires that investigators know which feathers are grown on breeding grounds and how the hydrogen stable-isotope ratios of feathers (δDf) relate to those of local precipitation (δDp). In this study, we measured δDf of adult (primaries 1, 3, and 10) and nestling Cooper's Hawks (Accipiter cooperii) in Wisconsin, North Dakota, and British Columbia, Canada. As previously shown, δDf of nestling feathers were related to δDp. In contrast, the δDf of adult feathers grown on the breeding grounds were substantially greater than those of their nestlings, and varied significantly across primary feathers and study areas. Our findings suggest that it is not possible to use hydrogen stable-isotope analysis of feathers to learn the origins of migrating adult Cooper's Hawks (or possibly adults of other large-bodied species with extended molting periods) until more is learned about the physiological or ecological mechanisms underlying these isotopic discrepancies.Variación en las Proporciones de Isótopos Estables de Hidrógeno entre Adultos y Polluelos de Accipiter cooperiiResumen. El análisis de isótopos estables de hidrógeno en las plumas es un método cada vez más popular para determinar el origen de aves migratorias e invernantes. El uso de esta técnica requiere que el investigador conozca qué plumas crecen en los lugares de nidificación y cómo las proporciones de isótopos estables de hidrógeno de las plumas (δDf) se relacionan con aquellas de la precipitación local (δDp). En este estudio, medimos las δDf en adultos (primarias 1, 3 y 10) y en polluelos de Accipiter cooperii en Wisconsin, North Dakota y British Columbia, Canadá. Como se ha mostrado previamente, las δDf de plumas de polluelos se encontraban relacionadas con las δDp. Por el contrario, las δDf de plumas de adultos que crecieron en los lugares de nidificación fueron substancialmente mayores que aquellas de sus polluelos, y variaron significativamente entre plumas primarias y áreas de estudio. Nuestros resultados sugieren que no es posible utilizar el análisis de isótopos estables de hidrógeno de plumas para determinar el origen de adultos migratorios de A. cooperii (o de adultos de otras especies de aves con tamaños corporales grandes y con períodos de muda extendidos) hasta que los mecanismos ecológicos y fisiológicos que subyacen a estas discrepancias isotópicas sean mejor entendidos.

Microbe forensics: oxygen and hydrogen stable isotope ratios in Bacillus subtilis cells and spores.

Bacillus subtilis, a Gram-positive, endospore-forming soil bacterium, was grown in media made with water of varying oxygen (delta(18)O) and hydrogen (deltaD) stable isotope ratios. Logarithmically growing cells and spores were each harvested from the cultures and their delta(18)O and deltaD values determined. Oxygen and hydrogen stable isotope ratios of organic matter were linearly related with those of the media water. We used the relationships determined in these experiments to calculate the effective whole-cell fractionation factors between water and organic matter for B. subtilis. We then predicted the delta(18)O and deltaD values of spores produced in nutritionally identical media and local water sources for five different locations around the United States. Each of the measured delta(18)O and deltaD values of the spores matched the predicted values within a 95% confidence interval, indicating that stable isotope ratio analyses may be a powerful tool for tracing the geographic point-of-origin for microbial products.

酸素および水素の安定同位体比と水質から見た長野県松本盆地中・南部地域の広域地下水流動系

山岳部に囲まれた標高550mから750mの高地にある松本盆地は,家庭用水や農業,工業,都市用水を地下水にかなりの部分依存している.そこで,地下水の酒養域や流動経路を理解することが,水資源管理や汚染の防止に重要である.松本盆地の酒養域や流動経路を同定するために地下水の水素および酸素の安定同位体比と水質を調べた.全ての安定同位体比は天水線に沿った広範囲にプロットされた.水素および酸素の安定同位体比と水質の空間分布および酸素の安定同位体の高度効果は,浅層と深層の流動系と5つの酒養域,7つの流動経路が本研究領域で識別可能であることを示している.浅層と深層の帯水層を通る4つの流動経路は河川の流れに沿っている.薄い沖積層で覆われた各々2つの推定断層を経由する流動経路が低い水素および酸素の安定同位体比から推定される.推定断層を経由して深層の帯水層へ移動する1つの流動経路が深層の水質と安定同位体比と浅層のそれらを比較することによって推定される.

Estimating the latitudinal origins of migratory birds using hydrogen and sulfur stable isotopes in feathers: influence of marine prey base

Hydrogen stable isotope analysis of feathers is an important tool for estimating the natal or breeding latitudes of nearctic-neotropical migratory birds. This method is based on the latitudinal variation of hydrogen stable isotope ratios in precipitation in North America (deltaD(p)) and the inheritance of this variation in newly formed feathers (deltaD(f)). We hypothesized that the typically strong relationship between deltaD(p) and deltaD(f) would be decoupled in birds that forage in marine food webs because marine waters have relatively high deltaD values compared to deltaD values for local precipitation. Birds that forage on marine prey bases should also have feathers with high delta(34)S values, since delta(34)S values for marine sulfate are generally higher than delta(34)S values in terrestrial systems. To examine this potential marine effect on feather stable isotope ratios, we measured deltaD and delta(34)S in the feathers of nine different species of raptors from both inland and coastal locations across North America. Feathers from coastal bird-eating raptors had consistently higher deltaD and delta(34)S values than feathers from inland birds. Birds that had high delta(34)S values also deviated strongly from the typical relationship between deltaD(p) and deltaD(f). We recommend measuring both sulfur and hydrogen stable isotope ratios in feathers when some members of a migrant population could potentially forage in marine habitats. We suggest using a practical cutoff of delta(34)S >10 per thousand to remove marine-foraging birds from a migrant sample when using stable isotopes of hydrogen to estimate the latitudinal origins of migrants because high deltaD(f) values for marine-foraging birds could potentially distort estimates of origins.

Seasonal variations in stable carbon and hydrogen isotope ratios in methane from rice fields

During two successive growing seasons, methane emissions from rice fields in Italy were measured. High‐precision measurements of the methane 13C/12C and D/H ratios were carried out by mass spectrometry and tunable diode laser absorption spectrometry. Significant seasonal variations were found for both δ13C and δD. The results confirm earlier observations by Bergamaschi [1997] in finding a seasonal cycle with isotopically depleted methane in the main growing season and higher values at the beginning and the end of the season during drainage of the field. The measured δ13C diurnal cycles showed a strong correlation with the methane emission rate. The isotopic composition of methane, which depended on the season, can be explained by variations of the different pathways for methane production, oxidation, and release into the atmosphere. A model based on these parameters was able to reproduce the field measurements and indicate the principal causes of observed fluctuations in the isotopic methane composition.

Using Hydrogen Isotope Geochemistry to Estimate the Natal Latitudes of Immature Cooper's Hawks Migrating Through the Florida Keys

AbstractWe constructed a regression model for the relationship between stable-hydrogen isotope ratios in immature Cooper's Hawk (Accipiter cooperii) feathers (δDf) and precipitation in areas where feathers were grown (δDp) across much of the latitudinal and longitudinal extent of the species' breeding range. We used our model to estimate δDp values from δDf values of immature Cooper's Hawks captured during migration in the Florida Keys. We compared these estimated δDp values to a published map of δDp values of North American precipitation to learn the latitudinal origins of migrants. We reviewed previous migration banding studies to estimate the longitudinal range of migrants. Our analysis suggested that most of the immature Cooper's Hawks migrating through the Keys originated in natal areas in the Mid-Atlantic and Southeast regions of the continent. We found no difference in the passage date of northern and southern birds or in the latitudinal origins of males and females. This new information will aid in the interpretation of population trends generated from the ongoing migration count in the Keys.

USING HYDROGEN ISOTOPE GEOCHEMISTRY TO ESTIMATE THE NATAL LATITUDES OF IMMATURE COOPER'S HAWKS MIGRATING THROUGH THE FLORIDA KEYS1

We constructed a regression model for the relationship between stable-hydrogen isotope ratios in immature Cooper's Hawk (Accipiter cooperii) feathers (δDf) and precipitation in areas where feathers were grown (δDp) across much of the latitudinal and longitudinal extent of the species' breeding range. We used our model to estimate δDp values from δDf values of immature Cooper's Hawks captured during migration in the Florida Keys. We compared these estimated δDp values to a published map of δDp values of North American precipitation to learn the latitudinal origins of migrants. We reviewed previous migration banding studies to estimate the longitudinal range of migrants. Our analysis suggested that most of the immature Cooper's Hawks migrating through the Keys originated in natal areas in the Mid-Atlantic and Southeast regions of the continent. We found no difference in the passage date of northern and southern birds or in the latitudinal origins of males and females. This new information will aid in the interpretation of population trends generated from the ongoing migration count in the Keys.

Isotopic characteristics of typhonic rainwater: typhoons no. 13 (1993) and no. 6 (1996)

The stable isotope ratios of hydrogen and oxygen were measured for rainwater samples from Typhoon No. 13, which struck Japan on September 1993, and Typhoon No. 6, which passed in July 1996. Rainwater was collected every hour over 2- to 3-day periods at Beppu, Japan (33°16′N, 131°29′E), which lies on or close to the typhoon routes. The deuterium excess parameters (δD – 8 ·δ18O) of the rainwaters vary over wide ranges from 19.22 to 1.52 for Typhoon No. 13, 1993, and from 6.02 to −8.10 for Typhoon No. 6, 1996, respectively. Rainwaters with higher d-values precipitated in the forward parts of the typhoons. This is ascribed to the possibility that the water vapors supplied by the bottom air currents from the front (rear) of the typhoons may be originally formed by rapid (gentle) evaporation of seawater. Symmetrical patterns of spatial δD and δ18O distributions within the typhoon precipitations, as estimated from the variations in the isotope ratios of the typhoon rainwaters, should appear from a continuous isotopic fractionation of water vapors with the bottom air currents converging toward the typhoon center. The weighted means of δD and δ18O of the typhoon precipitations are more negative than those of ordinary rainfall, suggesting that an isotopic influence of typhoon precipitation on surface waters, e.g., river, stream, lake, and spring waters, may be important.

Temporal and spatial partitioning of water resources among eight woody species in a Hawaiian dry forest.

Lowland dry forests are unique in Hawaii for their high diversity of tree species compared with wet forests. We characterized spatial and temporal partitioning of soil water resources among seven indigenous and one invasive dry forest species to determine whether the degree of partitioning was consistent with the relatively high species richness in these forests. Patterns of water utilization were inferred from stable hydrogen isotope ratios (δD) of soil and xylem water, zones of soil water depletion, plant water status, leaf phenology, and spatial patterns of species distribution. Soil water δD values ranged from -20‰ near the surface to -48‰ at 130 cm depth. Metrosideros polymorpha, an evergreen species, and Reynoldsia sandwicensis, a drought-deciduous species, had xylem sap δD values of about -52‰, and appeared to obtain their water largely from deeper soil layers. The remaining six species had xylem δD values ranging from -33 to -42‰, and apparently obtained water from shallower soil layers. Xylem water δD values were negatively correlated with minimum annual leaf water potential and positively correlated with leaf solute content, an integrated measure of leaf water deficit. Seasonal patterns of leaf production ranged from dry season deciduous at one extreme to evergreen with near constant leaf expansion rates at the other. Species tapping water more actively from deeper soil layers tended to exhibit larger seasonality of leaf production than species relying on shallower soil water sources. Individuals of Myoporum sandwicense were more spatially isolated than would be expected by chance. Even though this species apparently extracted water primarily from shallow soil layers, as indicated by its xylem δD values, its nearly constant growth rates across all seasons may have been the result of a larger volume of soil water available per individual. The two dominant species, Diospyros sandwicensis and Nestegis sandwicensis, exhibited low leaf water potentials during the dry season and apparently drew water mostly from the upper portion of the soil profile, which may have allowed them to exploit light precipitation events more effectively than the more deeply rooted species. Character displacement in spatial and temporal patterns of soil water uptake was consistent with the relatively high diversity of woody species in Hawaiian dry forests.

Deuterium and oxygen‐18 isotope composition of precipitation and atmospheric moisture

The stable isotopes of oxygen and hydrogen incorporated in the water molecule (18O and 2H) have become an important tool not only in Isotope Hydrology, routinely applied to study the origin and dynamics of surface and groundwaters, but also in studies related to atmospheric circulation and palaeoclimatic investigations. A proper understanding of the behaviour of these tracers in the water cycle is required for a meaningful use of these tools in any of these disciplines. Our knowledge of the vertical distribution and the factors controlling the stable isotope ratios of oxygen and hydrogen in atmospheric moisture derives from a limited number of observations and vertical profiles in the atmosphere. An international programme jointly operated by the International Atomic Energy Agency (IAEA) and the World Meteorological Organization (WMO), and operational since 1961, has resulted in the development of a dedicated database to monitor isotope ratios in precipitation in more than 500 meteorological stations world-wide. The main features of the spatial and temporal variations of stable isotope ratios of oxygen and hydrogen in precipitation and atmospheric moisture at the global scale are presented based on the analysis of limited data on water vapour, data obtained by the Global Network for Isotopes in Precipitation (GNIP) and the few observations at high latitudes. Copyright © 2000 John Wiley & Sons, Ltd.

Stable isotope systematics of surface water bodies in the Himalayan and Trans-Himalayan (Kashmir) region

Stable hydrogen (δD) and oxygen (δ18O) isotope ratios of the headwaters of the Indus and its tributaries, surface ice in glaciers, saline and fresh water lakes and thermal springs in the Himalayan and Trans-Himalayan (Kashmir) region are reported. The δ5D-δ18 relationship for the river samples shows a slope of 9.12 +-0.29 which agrees well with the estimate of 8.99 ±0.33 based on a simple Rayleigh fractionation model. The unique signature of a higher deuterium excess (d) of the ‘Western Disturbance’ is preserved in these samples. An altitude effect of -0.9 per mil/km is observed in the δ18O of Indus waters. At a lower altitude (Beas) the altitude effect is almost double, indicating that the altitude effect decreases with elevation in this region.

Is there a stable isotope evidence for the CO2 fertilization effect?

It has been suggested that part of the so-called “missing sink” of carbon dioxide introduced into the atmosphere by anthropogenic activities, that is the imbalance between estimated anthropogenic carbon dioxide emissions and oceanic uptake, may be stored in the vegetation in midlatitudes. Precise mechanisms of abstraction of additional carbon dioxide by vegetation, also known as the “fertilization effect”, are poorly understood. Stable carbon and hydrogen isotope ratios of cellulose extracted from annual growth rings (covering the time period 1980–1993) in an oak tree from Kalamazoo, SW Michigan provide a basis to investigate at a physiological level how the fertilization effect may operate. The carbon isotope ratios show that the intercellular concentration of carbon dioxide increased due to an increase in stomatal opening. Although increased intercellular concentration of carbon dioxide translated to increased Water Use Efficiency and assimilation rates, it also resulted in increased transpiration rate as shown by higher D/H of the fixed carbon. The two-fold significance of the isotope data are: first, they provide the first field evidence based on isotope studies for excess CO2 induced biomass production and second, they suggest that this mechanism is likely to operate only in limited environments. Vegetation in regions where moisture availability is not restricted so that there can be a gain in water use efficiency despite increased leaf evaporation are best suited to sequester excess carbon from the atmosphere.

Oxygen and hydrogen isotope study of high-pressure metagabbros and metabasalts (Cyclades, Greece): implications for the subduction of oceanic crust

Oxygen and hydrogen stable isotope ratios of eclogite-facies metagabbros and metabasalts from the Cycladic archipelago (Greece) document the scale and timing of fluid–rock interaction in subducted oceanic crust. Close similarities are found between the isotopic compositions of the high-pressure rocks and their ocean-floor equivalents. High-pressure minerals in metagabbros have low δ18O values: garnet 2.6 to 5.9‰, glaucophane 4.3 to 7.1‰; omphacite 3.5 to 6.2‰. Precursor actinolite that was formed during the hydrothermal alteration of the oceanic crust by seawater analyses at 3.7 to 6.3‰. These compositions are in the range of the δ18O values of unaltered igneous oceanic crust and high-temperature hydrothermally altered oceanic crust. In contrast, high-pressure metabasalts are characterised by 18O-enriched isotopic compositions (garnet 9.2 to 11.5‰, glaucophane 10.6 to 12.5‰, omphacite 10.2 to 12.8‰), which are consistent with the precursor basalts having undergone low-temperature alteration by seawater. D/H ratios of glaucophane and actinolite are also consistent with alteration by seawater. Remarkably constant oxygen isotope fractionations, compatible with isotopic equilibrium, are observed among high-pressure minerals, with Δglaucophane−garnet = 1.37 ± 0.24‰ and Δomphacite−garnet = 0.72 ± 0.24‰. For the estimated metamorphic temperature of 500 °C, these fractionations yield coefficients in the equation Δ = A * 106/T2 (in Kelvin) of Aglaucophane−garnet = 0.87 ± 0.15 and Aomphacite−garnet = 0.72 ± 0.24. A fractionation of Δglaucophane–actinolite = 0.94 ± 0.21‰ is measured in metagabbros, and indicates that isotopic equilibrium was established during the metamorphic reaction in which glaucophane formed at the expense of actinolite. The preservation of the isotopic compositions of gabbroic and basaltic oceanic crust and the equilibrium fractionations among minerals shows that high-pressure metamorphism occurred at low water/rock ratios. The isotopic equilibrium is only observed at hand-specimen scale, at an outcrop scale isotopic compositional differences occur among adjacent rocks. This heterogeneity reflects metre-scale compositional variations that developed during hydrothermal alteration by seawater and were subsequently inherited by the high-pressure metamorphic rocks.

Deuterium and oxygen-18 isotope composition of precipitation and atmospheric moisture

The stable isotopes of oxygen and hydrogen incorporated in the water molecule (18O and 2H) have become an important tool not only in Isotope Hydrology, routinely applied to study the origin and dynamics of surface and groundwaters, but also in studies related to atmospheric circulation and palaeoclimatic investigations. A proper understanding of the behaviour of these tracers in the water cycle is required for a meaningful use of these tools in any of these disciplines. Our knowledge of the vertical distribution and the factors controlling the stable isotope ratios of oxygen and hydrogen in atmospheric moisture derives from a limited number of observations and vertical profiles in the atmosphere. An international programme jointly operated by the International Atomic Energy Agency (IAEA) and the World Meteorological Organization (WMO), and operational since 1961, has resulted in the development of a dedicated database to monitor isotope ratios in precipitation in more than 500 meteorological stations world-wide. The main features of the spatial and temporal variations of stable isotope ratios of oxygen and hydrogen in precipitation and atmospheric moisture at the global scale are presented based on the analysis of limited data on water vapour, data obtained by the Global Network for Isotopes in Precipitation (GNIP) and the few observations at high latitudes. Copyright © 2000 John Wiley & Sons, Ltd.

Dynamics of landfill gas migration in unconsolidated sands

A gas plume from the Foxhall landfill in Suffolk, UK contains elevated concentrations of methane and carbon dioxide in unsaturated unconsolidated sands which comprise Pleistocene “Red Crag” deposits. The plume emanates from a relatively restricted zone along one side of the landfill, but extends over 100 m from the site boundary. The reduction in the methane to carbon dioxide ratio with distance and the systematic changes in their carbon and hydrogen stable isotope ratios are evidence of microbially mediated methane oxidation. A one-dimensional advection–diffusion model was used to describe the combined concentration of methane and carbon dioxide in the plume. Diffusion alone underestimated the concentration profile, but a good fit to the data was achieved with an advective flux of 4.5 m yr–1, indicating that advection due to a pressure gradient from the landfill as well as diffusion should be considered in gas migration modelling. The kinetics of methane oxidation was studied by parameter-fitting a reaction rate into the advection–diffusion equation with first-order decay. A decay constant of –0.063 yr–1 (half-life 11 yr) produced a poor fit to the methane profile, suggesting that oxidation may not be constant throughout the plume. However, the stable isotope data allowed two rates of oxidation to be inferred. A slow rate of oxidation with a half-life of the order of 4.3 to 7.6 yr was inferred in the centre of the plume where oxygen was absent. A much faster rate with a half-life no longer than 0.76 to 1.21 yr occurred beyond 60 m of the landfill and around the top fringe of the plume where oxygen was present. These rates are considered to reflect the difference between aerobic and anaerobic oxidation, the latter utilizing iron(III) in the sediment as an electron acceptor. The shape of the plume is asymmetrical, indicating a geological control on gas migration. In a two-dimensional model a poor fit to the observed data was obtained when the sand was assumed to be homogeneous and where the gas entered from a restricted part of the landfill boundary. However, a better model was produced by varying the diffusion coefficient in the sands over the range 5 × 10–7 to 2 × 10–6 m2 s–1 without the need to restrict the zone of gas release along the landfill boundary. Such a range in transport properties could be accounted for by normal variability in the porosity, tortuosity and water content of the sand. The long-term dissipation of the plume assuming only diffusion was predicted to take up to 30 yr for the gas concentration to reduce to 10% of its initial value. However, the plume disappeared within a year after pumping from gas wells in the landfill, indicating that advection under an imposed pressure gradient was a major control on remediation. This study shows that models can be used to explain landfill gas migration and to infer oxidation rates which can be used to predict gas migration at other sites. However, the need to obtain field data on gas permeabilities and diffusivities will always be a major limitation in predicting gas migration in permeable formations.