Mass Balance Techniques Research Articles

Effect of solid characteristics on hydrodynamic and mass transfer in a fixed bed reactor operating in co-current gas–liquid up flow

In order to understand better which parameters control the mass transfer efficiencies in biofilters, hydrodynamic and mass transfer parameters have been investigated for seven different packings in a three phase fixed bed reactor operating in co-current gas–liquid up flow. For this purpose, the packing characteristics (bed porosity, particle size and particle shape) and hydrodynamics parameters have been determined. Thus, the pressure drops, global gas hold-up, static gas fraction, slip velocities and bubble size have been investigated. For each type of solid, volumetric oxygen mass transfer coefficients have been measured under different operating conditions of gas (air) and liquid (tap water). The experiments were performed in a cylindrical PVC column with co-current up-flow of gas and liquid at laboratory temperature and atmospheric pressure. Air was injected at the bottom of the column using a porous disc diffuser. The superficial gas velocity ranged from 2.3E−3 m/s to 2.5E−2 m/s, the superficial liquid velocity varied from 1.2E−3 m/s to 3.3E−3 m/s. The column of 0.15 m in diameter and 4 m height was filled with packing. The following values were determined: • Pressure drop through the bed height was measured using differential manometers. • The average values of the global gas hold-up and static gas fraction were determined in the experimental set up by a new technique which is based on a monitoring of liquid flow. • The bubble sizes and slip velocities were determined by image acquisition and data treatment systems on a particular glass cell. • The volumetric oxygen mass transfer coefficient was determined by gas and liquid mass balance techniques. These different techniques applied on the fixed bed bubble column enabled for each type of solid a complete characterisation of hydrodynamic and mass transfer to be described. These experimental tools were used to compare and evaluate the influence of solid characteristics on the reactor performances and to initiate a mass transfer model.

Differentiating Pedogenesis from Diagenesis in Early Terrestrial Paleoweathering Surfaces Formed on Granitic Composition Parent Materials

Unconformable surfaces separating Precambrian crystalline basement and overlying Proterozoic to Cambrian sedimentary rocks provide an exceptional opportunity to examine the role of primitive soil ecosystems in weathering and resultant formation of saprolite (weathered rock retaining rock structure) and regolith (weathered rock without rock structure), but many appear to have been affected by burial diagenesis and hydrothermal fluid flow, leading some researchers to discount their suitability for such studies. We examine one modern weathering profile (Cecil series), four Cambrian paleoweathering profiles from the North American craton (Squaw Creek, Franklin Mountains, Core SQ‐8, and Core 4), one Neoproterozoic profile (Sheigra), and one late Paleoproterozoic profile (Baraboo), to test the hypothesis that these paleoweathering profiles do provide evidence of primitive terrestrial weathering despite their diagenetic and hydrothermal overprinting, especially additions of potassium. We employ an integrated approach using (1) detailed thin‐section investigations to identify characteristic pedogenic features associated with saprolitization and formation of well‐drained regoliths, (2) electron microprobe analysis to identify specific weathered and new mineral phases, and (3) geochemical mass balance techniques to characterize volume changes during weathering and elemental gains and losses of major and minor elements relative to the inferred parent materials. There is strong pedogenic evidence of paleoweathering, such as clay illuviation, sepic‐plasmic fabrics, redoximorphic features, and dissolution and alteration of feldspars and mafic minerals to kaolinite, gibbsite, and Fe oxides, as well as geochemical evidence, such as whole‐rock losses of Na, Ca, Mg, Si, Sr, Fe, and Mn greater than in modern profiles. Evidence of diagenesis includes net additions of K, Ba, and Rb determined through geochemical mass balance, K‐feldspar overgrowths in overlying sandstone sections, and K‐feldspars with reaction rims in weathered basement. The sub‐Cambrian paleoweathering profiles formed on granite are remarkably similar to modern weathering profiles formed on granite, in spite of overprinting by potassium diagenesis.

Kidney and splanchnic handling of Interleukin-6 in humans

Chronic elevation of circulating Interleukin-6 (IL-6) is observed in elderly individuals as well as in several illnesses, including chronic kidney diseases. A number of cells and tissues possess the ability to metabolize significant amounts of IL-6 in vitro. However, information on signals and mechanisms by which IL-6 is removed from blood in humans is still incomplete. To assess the individual role of splanchnic organs and kidney on IL-6 inter-organ exchange we used the IL-6 mass-balance technique across the hepato-splanchnic bed and kidney in six subjects with normal renal and liver function undergoing diagnostic venous catheterizations. Both in the hepatic and renal veins IL-6 levels were significantly lower ( p = 0.041 and 0.038, respectively), than in the artery. The fractional extraction of IL-6, i.e., the percentage of arterial IL-6 extracted after a single pass, was greater across the splanchnic organs (18%) than across the kidney (8%). Accordingly, IL-6 plasma clearance across splanchnic organs was greater than across the kidney and the sum of kidney and splanchnic removal accounted for as much as 63% of the estimated adipocyte IL-6 release. Our data demonstrate that, although the individual contribution to removal is different, both splanchnic organs and kidneys affect in a significant way the disposal of IL-6 in humans. According, both liver and kidney dysfunction could affect the handling of this proinflammatory cytokine and favour a chronic inflammatory response.

Recharge to groundwater in the Turi Basin, northern Chile: An evaluation based on tritium and chloride mass balance techniques

Summary The Turi Basin contains an unconfined phreatic aquifer within the Toconce Formation volcano-sedimentary sequence that passes eastwards under the Quaternary volcanic chain and outcrops in the Altiplano. The phreatic aquifer is floored by impermeable welded Miocene ignimbrites. Precipitation captured by the volcanic edifices infiltrates through high permeability soils to recharge the phreatic aquifer. The hydrochemistry of the groundwater in the phreatic aquifer shows little evidence of mixing with geothermal water and therefore approximates to a closed system. Tritium values demonstrate that recharge is occurring under current climatic conditions and takes around 40 years to pass 10+ km from recharge areas on the slopes of the volcanoes and the Altiplano to the center of the basin. The chloride mass balance technique has been used to quantify precipitation recharge at 15,500 m3 d−1. This is significantly less than the flow through the phreatic aquifer (58,000–86,000 m3 d−1) calculated from its physical properties and the difference is interpreted to be due to subsurface inflow through the Toconce Formation from the Altiplano. The results of this study have wider application throughout the Andean hydrological environment of northern Chile.

How effective are broad-scale nutrient mass balances for determining the sustainability of lot-feed manure application?

Nutrient mass balances have been used to assess a variety of land resource scenarios, at various scales. They are widely used as a simple basis for policy, planning, and regulatory decisions but it is not clear how accurately they reflect reality. This study provides a critique of broad-scale nutrient mass balances, with particular application to the fertiliser use of beef lot-feeding manure in Queensland. Mass balances completed at the district and farm scale were found to misrepresent actual manure management behaviour and potentially the risk of nutrient contamination of water resources. The difficulties of handling stockpile manure and concerns about soil compaction mean that manure is spread thickly over a few paddocks at a time and not evenly across a whole farm. Consequently, higher nutrient loads were applied to a single paddock less frequently than annually. This resulted in years with excess nitrogen, phosphorus, and potassium remaining in the soil profile. This conclusion was supported by evidence of significant nutrient movement in several of the soil profiles studied. Spreading manure is profitable, but maximum returns can be associated with increased risk of nutrient leaching relative to conventional inorganic fertiliser practices. Bio-economic simulations found this increased risk where manure was applied to supply crop nitrogen requirements (the practice of the case study farms, 200–5000 head lot-feeders). Thus, the use of broad-scale mass balances can be misleading because paddock management is spatially heterogeneous and this leads to increased local potential for nutrient loss. In response to the effect of spatial heterogeneity policy makers who intend to use mass balance techniques to estimate potential for nutrient contamination should apply these techniques conservatively.

Global synthesis of groundwater recharge in semiarid and arid regions

AbstractGlobal synthesis of the findings from ∼140 recharge study areas in semiarid and arid regions provides important information on recharge rates, controls, and processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), and radioactive waste disposal (US) are among the primary goals of many of these recharge studies. The chloride mass balance (CMB) technique is widely used to estimate recharge. Average recharge rates estimated over large areas (40–374 000 km2) range from 0·2 to 35 mm year−1, representing 0·1–5% of long‐term average annual precipitation. Extreme local variability in recharge, with rates up to ∼720 m year−1, results from focussed recharge beneath ephemeral streams and lakes and preferential flow mostly in fractured systems. System response to climate variability and land use/land cover (LU/LC) changes is archived in unsaturated zone tracer profiles and in groundwater level fluctuations. Inter‐annual climate variability related to El Niño Southern Oscillation (ENSO) results in up to three times higher recharge in regions within the SW US during periods of frequent El Niños (1977–1998) relative to periods dominated by La Niñas (1941–1957). Enhanced recharge related to ENSO is also documented in Argentina. Climate variability at decadal to century scales recorded in chloride profiles in Africa results in recharge rates of 30 mm year−1 during the Sahel drought (1970–1986) to 150 mm year−1 during non‐drought periods. Variations in climate at millennial scales in the SW US changed systems from recharge during the Pleistocene glacial period (≥10 000 years ago) to discharge during the Holocene semiarid period. LU/LC changes such as deforestation in Australia increased recharge up to about 2 orders of magnitude. Changes from natural grassland and shrublands to dryland (rain‐fed) agriculture altered systems from discharge (evapotranspiration, ET) to recharge in the SW US. The impact of LU change was much greater than climate variability in Niger (Africa), where replacement of savanna by crops increased recharge by about an order of magnitude even during severe droughts. Sensitivity of recharge to LU/LC changes suggests that recharge may be controlled through management of LU. In irrigated areas, recharge varies from 10 to 485 mm year−1, representing 1–25% of irrigation plus precipitation. However, irrigation pumpage in groundwater‐fed irrigated areas greatly exceeds recharge rates, resulting in groundwater mining. Increased recharge related to cultivation has mobilized salts that accumulated in the unsaturated zone over millennia, resulting in widespread groundwater and surface water contamination, particularly in Australia. The synthesis of recharge rates provided in this study contains valuable information for developing sustainable groundwater resource programmes within the context of climate variability and LU/LC change. Copyright © 2006 John Wiley & Sons, Ltd.

Groundwater and lake evolution in the Badain Jaran Desert ecosystem, Inner Mongolia

The amount and timing of aquifer recharge and the evolution of lakes and groundwater in the south-eastern Badain Jaran desert of Inner Mongolia, with high megadunes, has been investigated using stable isotopes and hydrochemistry. Unsaturated zone moisture profiles down to 22 m have recorded recharge over 1185 years. Small but finite amounts of recharge are recorded with mean recharge rates of 0.95-1.33 mm year−1, determined using a chloride mass balance technique. The unsaturated profile also acts as a unique archive of hydrological and climate change. Before 1300, it was relatively dry but distinct wet periods may be recognised during 1340-1450, 1500-1610 and 1710-1820. Since the mid 1800s, the climate shows a trend towards greater aridity. The interdune lakes are generally fresh but locally, hypersaline lakes are found in juxtaposition. This implies that in general, the lakes have low residence times and flow back into the dune system, but sedimentary obstruction locally prevents outflow and extreme evaporation occurs. The stable isotope records show that the lakes are fed by palaeowaters which on the basis of other proxy data must predate the Last Glacial Maximum. Their recharge source is problematic but most likely this derives from a diminishing water table extending some 30 m south to the Yabulai Mountains.

A review of the oxygen isotope composition of lacustrine diatom silica for palaeoclimate reconstruction

Diatom silica (frustules) are a form of biogenic opal and contain oxygen isotopes that are being increasingly used in palaeoclimate studies. Frustules are comprised of an inner tetrahedrally bonded silica skeleton (Si–O–Si) with an outer, hydrous layer. The hydrous layer is freely exchangeable and must be removed prior to oxygen isotope measurement using oxidising reagents and/or high temperatures. Analysis of the oxygen isotope composition of diatom silica requires samples that are almost pure diatomite since extraction techniques will liberate oxygen from all the components in the sediment. There is a generally acceptable protocol involving chemistry, sieving and settling techniques and more recently laminar flow separation. Recent studies of lacustrine diatoms have shown that even a small proportion of contaminant can have a significant influence on the oxygen isotope value. All lake sediments require their own specific procedure and every sample must be scrutinised by microscopy to check for the level of contamination prior to analysis. Where sediment cannot be purified sufficiently, a semi-quantitative assessment of the diatom content can facilitate mass balance techniques. When robust preparation methods are used, diatom silica offers an important palaeoclimate proxy, providing an additional complementary, rather than an alternative, host of oxygen isotopes in carbonates. In lacustrine isotope studies it is often assumed, but rarely proven, that diatom silica form in isotope equilibrium and hence empirically derived palaeotemperature equations, usually made in vitro, can be used. Most studies lack the detailed investigation of contemporaneous materials from natural waters of the region under study to test these equations. Further investigations need to be conducted in order to understand the systematic relationship between temperature, water isotope composition and diatom isotope composition to enable quantitative interpretation of the sediment record. Experiments to test for vital effects and inter-specific differences have so far revealed little variation. It is useful to know when and where the diatom silica is formed in the modern environment, so details of diatom ecology are important in the interpretation of isotope data. Here we show that valuable palaeoclimate data can be gained from the oxygen isotope composition of diatom silica (δ 18O diatom), especially since diatoms are abundant in many lakes sensitive to climate variation where other hosts (e.g., carbonates) are absent. To date the most successful studies have been conducted in areas where the δ 18O diatom registers changes in the oxygen isotope composition of the lake water (rather than temperature) which is then related to other aspects of climate. In these studies, the range of values obtained is often greater than the error introduced by contaminating materials.

Measuring ammonia emissions from land applied manure: an intercomparison of commonly used samplers and techniques

A number of techniques have been developed to quantify ammonia (NH 3) emissions following land application of manure or fertiliser. In this study, coefficients of variation were determined for three commonly used field techniques (mass balance integrated horizontal flux, wind tunnels and the equilibrium concentration technique) for measuring emissions from a range of manure types. Coefficients of variation (CV) for absorption flasks, passive flux samplers and passive diffusion samplers were 21, 10 and 14%, respectively. In comparative measurements, concentrations measured using passive flux samplers and absorption flasks did not differ significantly, but those measured using passive diffusion samplers were on average 1.8 times greater. The mass balance technique and wind tunnels gave broadly similar results in two out of four field tests. Overexposure of passive diffusion samplers for some sampling periods meant that estimation of cumulative NH 3 emission using the equilibrium concentration technique in the field tests could not be made. For cumulative NH 3 emissions, CVs were in the range of 23–52, 46–74 and 21–39% for the mass balance, wind tunnel and equilibrium concentration techniques, respectively. Lower CVs were associated with measurements following slurry compared with solid manure applications. Our conclusions from this study are that for the measurement of absolute emissions the mass balance technique is to be preferred, and for small-plot comparative measurements the wind tunnel system is preferred to the equilibrium concentration technique.

Examining strategies to improve the carbon balance of corn/soybean agriculture using eddy covariance and mass balance techniques

There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO 2 concentrations. A number of management methods that might increase soil C levels have been suggested, but there are scant available data to properly support recommendations or policy changes. We have used eddy covariance measurements of net ecosystem exchange (NEE) in contrasting management systems to discern the impact of two specific practices, reduced tillage and a spring cover crop in the soybean year, on the biennial C balance of a corn/soybean rotation, the dominant cropping system in much of the midwestern United States. Measurements commenced in fall 2001, immediately following corn harvest and tillage, and continued through a year of soybean and a year of corn. One of the two fields was farmed conventionally (CONV), with fall chisel/disk tillage after each harvest, soybean planting in late May (2002), and corn planting in early May (2003). In the alternative field (ALT), we used reduced tillage (strip till) each fall following harvest, and a spring oats cover crop in the soybean year (2002) that was planted in early April, then killed with a herbicide shortly after soybean planting. Both fields have the same soil type, and were similarly instrumented, with a sonic anemometer and open-path infrared gas analyzer. Reduced tillage resulted in somewhat lower soil respiration rates in both autumns in ALT, relative to CONV. Also, the spring oats cover crop prior to soybean did fix additional C, but it was rapidly respired after the oats were killed, and the surface crop residue slowed the initial development of the subsequent soybean crop. Soybean yields for the two fields were similar, but slightly higher for CONV, a pattern that was more pronounced with corn the following year. Overall, cumulative NEE was larger (more C fixed) in the conventional field, but C removed in yield in the conventional field was larger too, so that the apparent change in soil organic carbon (ΔSOC), estimated as NEE – harvested C, in the two fields was nearly identical. In both treatments the apparent ΔSOC was negative (approximately 90 g C m −2 SOC lost over the biennium, or about 20% of cumulative NEE) but this may be at least partially due to systematic underestimation by eddy covariance rather than an actual loss of SOC. We conclude that neither of these management practices (reduced tillage, spring cover crop) resulted in any C sequestration within the first two years of implementation that is resolvable with current measurement methods.

Analysis and applications of measurements of source dominated hydrocarbon concentrations from the PUMA campaigns in June/July 1999 and January/February 2000 at an urban background site in Birmingham, UK

Approximately, hourly C 2 –C 7 hydrocarbon concentrations from gas chromatographic measurements are reported for an urban background site in Birmingham, UK, from summer 1999 and winter 1999–2000. Comparison with another measurement site suggests that the observed behaviour is typical of the urban background in the whole conurbation. The lack of any correlation between seasonal variation and OH rate coefficient shows that hydrocarbon concentrations are dominated by local sources. Chemical mass balance techniques have been applied and indicate the main sources are vehicle emissions (exhaust and fugitive) and natural gas leakage. Winter concentrations of isoprene correlate well with butadiene concentrations suggesting an automotive related source. This correlation disappears during the summer when isoprene displays a high correlation with radiation. During a period of the summer campaign ethane and propane concentrations displayed a regular diurnal behaviour, which has been utilized to estimate the ratios of the day/night boundary layer height and natural gas emission rates for the West Midlands conurbation.

Comparison of methods for the determination of KLaO2 for respirometric measurements

The mass transfer coefficient for oxygen in water (KLaO2) is an important parameter for respirometric studies. But determination of KLaO2 in process conditions is not straightforward. In this paper, two distinct procedures for determining KLaO2 in process conditions are outlined and tested. The off-gas method relies on a gas mass balance over a bioreactor while the non-steady state methods rely on analysing DO recovery after perturbation. Various means for inducing perturbation are tested and compared. KLaO2 values for a bioreactor are determined by the listed methods. It was found that the off-gas method resulted in the highest KLaO2 for the given reactor, while the non-steady state method, whereby perturbation is caused by exogenous activity on acetate, resulted in the lowest KLaO2. It is shown that the gas mass balancing technique is robust to unexpected exogenous activity (caused by for example, the oxidation of storage polymers formed or nitrite accumulated), while the non-steady state methods that involve inducing perturbations by exogenous activity appear susceptible to such continued exogenous activity in the DO recovery period.

Kinetic isotopic fractionation during carbonate dissolution in laboratory experiments: Implications for detection of microbial CO 2 signatures using δ 13C-DIC

Laboratory experiments on reagent-grade calcium carbonate and carbonate rich glacial sediments demonstrate previously unreported kinetic fractionation of carbon isotopes during the initial hydrolysis and early stages of carbonate dissolution driven by atmospheric CO 2. There is preferential dissolution of Ca 12CO 3 during hydrolysis, resulting in δ 13C-DIC values that are significantly lighter isotopically than the bulk carbonate. The fractionation factor for this kinetic isotopic effect is defined as ε carb. ε carb is greater on average for glacial sediments (−17.4‰) than for calcium carbonate (−7.8‰) for the < 63 μm size fraction, a sediment concentration of 5 g L −1 and closed system conditions at 5°C. This difference is most likely due to the preferential dissolution of highly reactive ultra-fine particles with damaged surfaces that are common in subglacial sediments. The kinetic isotopic fractionation has a greater impact on δ 13C-DIC at higher CaCO 3:water ratios and is significant during at least the first 6 h of carbonate dissolution driven by atmospheric CO 2 at sediment concentrations of 5 g L −1. Atmospheric CO 2 dissolving into solution following carbonate hydrolysis does not exhibit any significant equilibrium isotopic fractionation for at least ∼ 6 h after the start of the experiment at 5°C. This is considerably longer than previously reported in the literature. Thus, kinetic fractionation processes will likely dominate the δ 13C-DIC signal in natural environments where rock:water contact times are short <6–24 h (e.g., glacial systems, headwaters in fluvial catchments) and there is an excess of carbonate in the sediments. It will be difficult apply conventional isotope mass balance techniques in these types of environment to identify microbial CO 2 signatures in DIC from δ 13C-DIC data.

Kidney Protein Dynamics and Ammoniagenesis in Humans with Chronic Metabolic Acidosis

To evaluate the effects of chronic metabolic acidosis on protein dynamics and amino acid oxidation in the human kidney, a combination of organ isotopic ((14)C-leucine) and mass-balance techniques in 11 subjects with normal renal function undergoing venous catheterizations was used. Five of 11 studies were performed in the presence of metabolic acidosis. In subjects with normal acid-base balance, kidney protein degradation was 35% to 130% higher than protein synthesis, so net protein leucine balance was markedly negative. In acidemic subjects, kidney protein degradation was no different from protein synthesis and was significantly lower (P < 0.05) than in controls. Kidney leucine oxidation was similar in both groups. Urinary ammonia excretion and total ammonia production were 186% and 110% higher, respectively, and more of the ammonia that was produced was shifted into urine (82% versus 65% in acidemic subjects versus controls). In all studies, protein degradation and net protein balance across the kidney were inversely related to urinary ammonia excretion and to the partition of ammonia into urine, but not to total ammonia production, arterial pH, [HCO(-)(3)], urinary flow, the uptake of glutamine by the kidney, or the ammonia released into the renal veins. The data show that response of the human kidney to metabolic acidosis includes both changes in amino acid uptake and suppression of protein degradation. The latter effect, which is likely induced by the increase in ammonia excretion and partition into the urine, is potentially responsible for kidney hypertrophy.

Polar organic compounds measured in fine particulate matter during TexAQS 2000

Fine particle samples were collected at three sites in the Houston area during TexAQS 2000. Polar organic species including levoglucosan, n -alkanoic acids, n -alkenoic acids and dicarboxylic acids were quantified to characterize the composition of local ambient organic aerosols. Levoglucosan, a tracer for biomass burning, was measured as a dominant compound, followed by n -alkanoic acids. The compound distribution of higher molecular weight n -alkanoic acids (⩾C 22 ) was consistent with biogenic emission sources. n -Alkenoic acids exhibit variable concentrations during sampling period with high ratios of octadecanoic to octadecenoic acid. The concentrations of dicarboxylic acids are compared with unapportioned organic carbon calculated by the chemical mass balancing technique. This correlation supports the conclusion that diacids are generated by photochemical reactions and contribute to the unapportioned organic mass. Data collected during a regional wood smoke episode are used to examine the influence of wood combustion to ambient particulate matter concentrations.

Polar organic compounds measured in fine particulate matter during TexAQS 2000

Abstract Fine particle samples were collected at three sites in the Houston area during TexAQS 2000. Polar organic species including levoglucosan, n-alkanoic acids, n-alkenoic acids and dicarboxylic acids were quantified to characterize the composition of local ambient organic aerosols. Levoglucosan, a tracer for biomass burning, was measured as a dominant compound, followed by n-alkanoic acids. The compound distribution of higher molecular weight n-alkanoic acids (⩾C22) was consistent with biogenic emission sources. n-Alkenoic acids exhibit variable concentrations during sampling period with high ratios of octadecanoic to octadecenoic acid. The concentrations of dicarboxylic acids are compared with unapportioned organic carbon calculated by the chemical mass balancing technique. This correlation supports the conclusion that diacids are generated by photochemical reactions and contribute to the unapportioned organic mass. Data collected during a regional wood smoke episode are used to examine the influence of wood combustion to ambient particulate matter concentrations.

Atmospheric Dispersion of Gases and Odours from Animal Production Systems

Animal production systems are major agricultural sources of the greenhouse gases, methane and nitrous oxide, of pollutants such as ammonia and hydrogen sulfide, and of odours. Verifying inventory estimates of their production, and monitoring, regulating and reducing their emission all require the ability to make precise, non-obtrusive measurements of their fluxes, and in the case of odours, an ability to predict concentrations close to the source. However, these requirements present special problems. The source areas are often small or irregularly shaped, the sources may be distributed heterogeneously, and emissions may be transient. Odours present an additional problem in that it is difficult to quantify their intensity since they are usually due to a mixture of more than 100 volatile organic compounds. The use of tracer gases to follow odour dispersion is discussed, but quantifying odour intensity is a pressing problem. The paper considers measurement techniques appropriate for sources of different shapes and sizes. Most attention is given to small and irregularly shaped sources for which conventional, large-area micrometeorological approaches are inapplicable: line-sources, strips, small plots, and waste storage areas such as ponds and manure piles. Mass balance techniques appear to be particularly useful for these purposes. Various applications of the methodology are considered in some detail. The advent of open-path gas lasers that can measure concentrations rapidly and over distances of hundreds of meters is seen as a significant development. Finally, the paper considers the use of a Lagrangian dispersion model that allows emissions from sources of any geometry to be linked to concentrations at any location downwind. In forward mode, it can predict downwind concentrations for given source scenarios, while in backward mode, it can infer fluxes from measurements of concentration and wind speed at just one height downwind. It is a very attractive tool for use in many dispersion problems relevant to the theme of the paper.

A mass balance approach for assessing basin-centred gas prospects: integrating reservoir engineering, geochemistry and petrophysics

Abstract This paper presents a mass balance technique for evaluating the resource-in-place potential of basin-centred gas exploration prospects. As the name implies, the methodology is derived from the conservation of mass principle. Unlike conventional reservoir engineering techniques, the mass balance approach directly integrates dynamic elements of the total petroleum system with all static reservoir engineering, geological and petrophysical data to estimate the resource-in-place. This prospect evaluation technique not only provides an independent estimate of hydrocarbon resource-in-place for comparison with that computed from the conventional reservoir engineering approach, but also gives estimates of hydrocarbons lost from the petroleum system. Accordingly, this technique reduces the inherent uncertainty associated with conventional methods and provides more realistic estimates of resource-in-place.

Hydrogeochemical modeling of the shallow groundwater in the northern Jordan Valley

The reasons for the rapid degradation and salination of the shallow aquifer in the northern Jordan Valley were investigated. Shallow groundwater, surface water and thermal water were sampled from the study area for this purpose. The geochemical mass-balance technique was used to quantify the contribution of different sources, geochemical processes and rock types to the final water composition, applying the NETPATH software package. The isotopic compositions of the water were also investigated. The results suggest three potential recharge sources: the Yarmouk River, the Jordan River, and the Mukheibah thermal water. Evaporation significantly contributes to the current chemistry of the shallow water, as is indicated by the geochemical models and the isotopic results. Tritium analyses indicate that the water is clearly new (less than 50 years). The relatively high values of nitrate in some wells may be of anthropogenic origin.

INCORPORATION OF CHLORIDE MASS BALANCE TO IMPROVE ESTIMATES OF EVAPOTRANSPIRATION, RECHARGE, AND RUNOFF

A method is presented whereby measured soil water chloride concentrations and longterm precipitation and airtemperature profiles are interpreted to provide temporal estimates of evapotranspiration, recharge, and runoff. Applying thechloride mass balance technique to soil water chloride profiles improves the boundary conditions associated with thelongterm mean recharge rate. Temporal estimates of evapotranspiration and runoff are calculated from precipitation andair temperature data. Next, these estimates and measured precipitation are used as inputs in an unsaturated groundwatermodel to estimate temporal recharge, which is subsequently compared to the longterm mean recharge rate calculated fromthe chloride profiles. Finally, the evapotranspiration and runoff components of the model are scaled such that the modeledrecharge rate is similar to the longterm mean recharge rate.<br><br>This method improves the chloride mass balance method, which up to now only provides longterm mean recharge.Additionally, the method allows initial estimates of evapotranspiration and runoff to be scaled such that the resultingestimates of evapotranspiration and runoff are consistent with both chloride mass balance and water mass balance. Althoughdirect methods to measure evapotranspiration, recharge, and runoff are attractive, they are not always reasonable due to theexpense of collecting data over long time periods. In contrast, this method obtains its required input from basic meteorologicaldata and soil cores collected at a single point in time.