bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil salinization at a side-hill seep and closed basin in southern Alberta
Authors: Miller J. J. , Beke G. J. , Pawluk S.
Published: April 2011

One saline soil in a side-hill seep and another in a closed basin in southern Alberta were investigated using hydrological, chemical and mineralogical techniques to compare the nature of soil salinization. The morphology of the saline Gleyed Regosolic soil in the seep indicated strong upward movement of water and soluble salts. This was evident from the presence of mottles in the soil solum, a shallow water table (≤ 2.69 m), and high EC (2.8–32.5 dS m−1) and SARt (4.8–55.5) values in the shallow groundwater and soil. High soluble Mg/Ca ratios (2.1) in the soil extract of the Ccasa3 horizon and the presence of Mg-calcites (4–5 mol %) indicated restricted leaching at this site. The morphology of the saline Orthic Dark Brown Chernozemic soil in the closed basin reflected slight upward movement of water and soluble salts. This morphology was consistent with a deeper water table (≥ 2.62 m), and lower EC (2.2–10.0 dS m−1) and SARt (2.9–11.3) values in the shallow groundwater and soil. High Mg/Ca ratios (4.8–7.0) in soil extracts of the C horizons, but no Mg-calcites, indicated greater leaching at this site. We estimated that it would take about 77 yr to salinize the soil at the seep via upward groundwater movement, and 6500 yr to salinize the soil at the closed basin. The high tritium content of the shallow groundwater at both sites suggested that downward (closed basin) and lateral (seep) movement of water to the water table was an important factor contributing to shallow water tables and soil salinization. Key words: Salinization, hydrology, chemistry, mineralogy, side-hill seep, closed basin
Evaporite mineralogy and trace-element content of salt-affected soils in Alberta
Authors: Kohut Connie K. , Dudas M. J.
Published: April 2011

A survey of efflorescent crusts and associated surface soils in central and southern Alberta was conducted to determine evaporite mineralogy and elemental composition. X-ray powder diffraction indicates that efflorescence mineralogies are dominated by sodium sulfate minerals, such as thenardite and mirabilite. Sodium magnesium sulfate minerals such as konyaite and bloedite are also frequently present, with eugsterite, halite and thermonatrite among other evaporites identified. The content of selected elements in the salt crusts and surface soils was determined using instrumental neutron activation analysis. Trace-element concentrations from site to site were extremely variable. However, comparisons with elemental abundances previously reported for till and soils indicate that there is generally no mean accumulation of trace elements in salt-affected soils. Exceptions are Br and Cl, which show enrichment in soils infused with soluble salts. Key words: Salinity, trace elements, evaporites, mineralogy
Effect of timing of application on the recovery of fertilizer N applied to irrigated soft white wheat
Authors: Carefoot J. M. , Conner R. L. , Bole J. B.
Published: April 2011

The effect of timing of application on the recovery of fertilizer N applied to irrigated soft white wheat (Triticum aestivum L.) was investigated in a 3-yr field study and a 1-yr lysimeter study using 15N-labelled urea and ammonium nitrate. Fertilizer N treatments consisted of a check and 90 kg ha−1 applied as preplant N, postplant N or combinations. Under a controlled watering regime in the lysimeter experiment, timing of N application had no effect on plant growth parameters. In the field studies, although grain yield was not affected by N timing, grain N concentration increased from 17.9 to 19.6 g kg−1 as the proportion of postplant N was increased from 0 to 100%. Plant N uptake was greater when all of the N was applied postplant than preplant (means = 124.5 and 114.2 kg ha−1, respectively) in the field studies. Plant recovery of fertilizer N (FNR) by the difference method was greater when all of the fertilizer N was applied postplant (43.7%) man preplant (28.6%) in the field experiments. With a negative apparent added N interaction (ANI), the FNR was less by the difference method than by the 15N method. However, with a positive ANI, FNR was less by the 15N method than by the difference method. There was a greater difference between methods as the proportion of N applied as postplant N increased. Key words: Fertilizer N timing, irrigation, soft white wheat, nitrogation, fertilizer N recovery
Acidic leaching of a Podzol Bf horizon from the Precambrian Shield, Ontario, Canada
Authors: LaZerte Bruce , Findeis Joe
Published: April 2011

Illuviated mineral horizons (Bf) from a Podzol on the Precambrian Shield, Ontario, Canada were collected, placed in columns and treated with distilled water, cation amended water, acidified water or cation and acid amended water over a 4-mo period. While the cation treatment had little effect relative to the control, the acid treatment removed large quantities of Al, Si and base cations. The source of the leached Al was primarily (~ 70%) dithionite–citrate–bicarbonate (DCB) extractable Al, apparently some form of amorphous gibbsite. Organic Al (pyrophosphate extractable) contributed only about 20%. However, even more pronounced was a major within-column migration of oxalate extractable Al–Si, perhaps allophane or imogolite, which was leached from the top of the acidified columns and precipitated below. The weathering of primary minerals and possibly interlayer Al in vermiculite contributed little to the leaching of Al from the acidified columns. Key words: Acid, weathering, Podzol, aluminum, silica
Carry-over of granular and emulsifiable concentrate formulations of trifluralin in Saskatchewan
Authors: Smith Allan E. , Aubin Andrew J.
Published: April 2011

The field persistence of trifluralin from fall treatments of both emulsifiable concentrate (EC) and granular formulations was investigated at two sites in Saskatchewan over a 2-yr period. At both locations, there were no significant differences (P = 0.05) in trifluralin persistence from fall applications of either formulation. In addition, the carryover of trifluralin residues in farmers’ fields following fall and spring applications of EC and granular formulations was monitored at several Saskatchewan locations to determine their persistence under typical farming practices. Trifluralin residue data indicated that following fall applications, the percent carry-over to the first spring was 83 ± 21(15 fields sampled) and 37 ± 15 (28 fields sampled) to the second spring; and that following spring applications, the percent carry-over to the next spring was 33 ± 12 (14 fields sampled). Key words: Field studies, persistence, formulations, trifluralin, herbicide
Management systems for conservation fallow on the southern Canadian prairies
Authors: Blackshaw R. E. , Lindwall C. W.
Published: April 2011

Fallow continues to be a common agronomic practice on the southern Canadian prairies, but it has been associated with increased soil erosion and salinity and declining soil fertility. Field experiments were conducted at Lethbridge, Alberta, from 1987 to 1992 to determine the effects of various fallow treatments on weed control, conservation of surface crop residues, accumulation of soil water, and succeeding spring and winter wheat yields. Conventional cultivation during the fallow year with 168-cm sweeps controlled most spring-germinating weeds but did not adequately control overwintered flix-weed or downy brome. Repeated applications of glyphosate and 2,4-D effectively controlled most weeds. Paraquat did not control wild buckwheat or dandelion. Glyphosate alone often did not control wild buckwheat or Russian thistle. Treatments involving a combination of herbicides and tillage gave the best control of all weed species. Although not as effective in conserving surface crop residues as sole use of herbicides, many of the combined herbicide-tillage treatments maintained sufficient crop residue to keep the risk of soil erosion low. Soil water accumulation and succeeding wheat yields with the combined herbicide-tillage treatments were similar to, or greater than, those attained with repeated herbicides or repeated tillage. Management systems combining herbicides and tillage for fallow weed control may reduce costs and prevent or retard the development of herbicide resistance. Key words: Water conservation, herbicides, reduced tillage, soil erosion, stubble retention, weed control, wheat yield, no-till
Efficacy of inorganic fertilizers in restoring wheat yields on artificially eroded soils
Authors: Larney Francis J. , Janzen H. Henry , Olson Barry M.
Published: April 2011

Chemical fertilizers are often used to amend eroded agricultural land. However, the relationships between level of erosion, nitrogen (N) rate and phosphorus (P) rate in restoring soil productivity are unclear. In 1990, experiments were initiated to examine the effect of three levels of erosion (0, 10 and 20 cm of topsoil removal to simulate non-eroded, moderately eroded and severely eroded soils), four rates of N and three rates of P on the performance of spring wheat (Triticum aestivum L.) for four southern Alberta soils. Residual erosion and fertilizer effects were assessed in a second cropped year. Erosion significantly decreased grain and straw yield at all four sites in the initial year. Removing 10 and 20 cm of topsoil reduced non-fertilized production by 43–66% and 60–85%, respectively, as compared with the undisturbed non-fertilized plots. Except for one site in the initial year, additions of N and P only partly remedied these losses. Responses to N and P were highest at moderate levels of erosion at three sites. There was a greater yield overlap between moderately and severely eroded treatments than between non-eroded and moderately eroded treatments, implying that the restoration of productivity is more difficult once the shallowest layer of topsoil has been removed. Key words: Simulated erosion, wheat, inorganic fertilizer, soil restoration
Carbon dioxide balance of a crop-fallow rotation in western Canada
Authors: McGinn S M , Akinremi O O
Published: April 2011

The use of micrometeorological and chamber techniques is a unique means to investigate the seasonal CO2 cycle in agriculture. Two growing seasons are reported in this study, one being a wet year (207 mm 1994) and the other a dry year (86 mm 1996). A Bowen ratio tower and automated soil chambers were set up in a barley and fallow field to simultaneously monitor energy and carbon dioxide fluxes. These fluxes were integrated over the measurement period to arrive at a seasonal carbon balance of each surface. Our results show that barley removed CO2 from the atmosphere, amounting to −9.5 and −8.5 Mg CO2 ha-1 in 1994 and 1996, respectively. A portion of the atmospheric CO2 was retained by the soil (6.6 and 3.7 Mg CO2 ha-1 in 1994 and 1996, respectively). The soil in fallow emitted −11.1 and −6.7 Mg CO2 ha-1 in 1994 and 1996, respectively. Above a crop-fallow area, the atmosphere gained CO2 from the surface in 1994 (0.8 Mg CO2 ha-1) but was a source of CO2 in 1996 (losing −1 Mg CO2 ha-1 to the surface). The soil under a crop-fallow area lost CO2 in both years (−2.2 and −1.5 Mg CO2 ha-1 in 1994 and 1996, respectively). Key words: Carbon dioxide, fluxes, barley, fallow, respiration, photosynthesis
Magnetic susceptibility of a saprolite and a soil profile developed on pyroxenite at Mont-Saint-Bruno, Quebec, Canada
Authors: De Kimpe C R , Dejou J. , Chevalier Y.
Published: April 2011

Magnetic susceptibility (χ) measurements were performed with a recording magnetic susceptivimeter on a pyroxenite and its alteration products, i.e., a saprolite and the horizons of a soil profile. Pyroxenite contains a relatively high percentage of opaque minerals that, under alteration, transformed partly into Fe oxides with a high magnetic susceptibility. In the saprolite and the soil, χ values varied according to depth in the profile, particle size, mineralogical and chemical composition. Significant correlations between χ values and Fe and Ti oxides indicated the importance of opaque minerals, magnetite, maghemite and ilmenite to the magnetic susceptibility of the alteration products of the pyroxenite. This method provided additional information on the intensity of the alteration of the rock, especially on the formation of secondary Fe oxides at the expense of the ferromagnesian minerals. Key words: Magnetic susceptibility, pyroxenite, saprolite, maghetite, maghemite, opaque minerals
Evaluation of the potassium supplying power of Abitibi-Temiscaming soils by electro-ultrafiltration and chemical methods
Authors: Ziadi N. , Simard R R , Tran T S , Allard G.
Published: April 2011

Soil K supplies were studied in the Abitibi-Temiscaming region of Canada to determine the K buffering capacity of heavy clay soils. Forages did not respond for 3 yr to K fertiliser on these soils. In addition, Mehlich-3 K did not change in the unfertilised control soil after six forage cuts taken over 3 yr. The origin of the plant-available K has thus to be identified to refine fertiliser K recommendations. Four soils with or without K addition (0 and 166 kg K ha–1 yr–1) were characterised. On average, increasingly higher soil K were extracted by Electro-ultrafiltration (EUF) at 50 V and 20°C (21 mg kg–1), EUF at 200 V and 20°C (59 mg kg–1), EUF at 400 V and 80°C (68 mg kg–1), Mehlich 3 (202 mg kg–1), 1 M NH4OAc (214 mg kg−1) and 1 M HNO3 (1808 mg kg–1). Highly significant relationships (0.97 < R2 < 0.99) between K desorbed at 200 V and 20°C and time were obtained. The large amounts of K desorbed by EUF at 80°C and 400 V and a KQ ratio larger than 0.6 indicate a high capacity of rapidly and slowly exchangeable K sources to buffer soil solution K. The EUF technique showed that the lack of forage response to K fertiliser was related to large soil K reserves and their capacity to replenish soil solution K. Key words: HNO3-K, Mehlich 3-K, NH4OAc-K, EUF
An innovative approach for visualization of subsurface soil properties
Authors: Hu Z. , Bass B. , Chan C. W. , Huang G. H.
Published: April 2011

Subsurface characterization is an important requirement in the decision-making process of selecting a remediation technique for petroleum-contaminated sites. The soil type distribution is one of the most important site characteristics, because it affects selection of the site remediation technique. The visualization of soil type distribution and also the contaminant concentration distribution in the subsurface can help the decision-maker understand the site and select the proper remediation technique. In this paper, we describe the software Soil-Visual (1.0, 1.1), which is used for visualizing the soil sampling data, the soil type distribution, and contaminant concentration distribution of a contaminated site. This software has two functions: (1) to determine the soil particle size distribution and contaminant concentration distribution of the entire site from limited soil sampling data; and (2) to visualize the multi-dimensional soil type distribution and contaminant concentration distribution data of each soil layer on a two-dimensional map. The red-green-blue (RGB) color illustration method has been used in this software to convert the multi-dimensional soil sampling data into a bitmap. Key words: RGB bitmap, soil classification, visualization
Atmosphere composition and N2O emissions in soils of contrasting textures fertilized with anhydrous ammonia
Authors: Régis R. Simard Philippe Rochette, , Michel C. Nolin Noura Ziadi, , Cambouris Athyna N.
Published: April 2011

Nitrous oxide production and emission in agricultural soils are often influenced by soil physical properties and mineral N content. An experiment was initiated on a commercial farm located in the St. Lawrence Lowlands to measure the effects of recommended (150 kg N ha-1) and excessive (250 kg N ha-1) rates of anhydrous ammonia on atmospheric composition (O2, CO2, CH4 and N2O) and N2O emissions in soils of contrasting textures (sandy loam, clay loam and clay) cropped to corn. N2O emissions and soil temperature, water content and atmospheric composition were measured from post-harvest tillage to the first snowfall during the first year (2000), and from spring thaw to mid-July during the following 2 yr. Episodes of high N2O concentrations and surface emissions coincided with periods of high soil water content shortly following rainfall events when soil O2 concentrations were lowest. The convergence of indicators of restricted soil aeration at the time of highest N2O production suggested that denitrification was a major contributor to N2O emissions even in soils receiving an NH4-based fertilizer. Soil texture had a significant influence on soil N2O concentration and emission rates on several sampling dates. However, the effect was relatively small and it was not consistent, likely because of complex interactions between soil physical properties and N2O production, consumption and diffusion processes. Nitrous oxide emissions during the study were not limited by soil N availability as indicated by similar fluxes at recommended and excessive rates of anhydrous ammonia. Finally, greater N2O emissions in 2001 than in 2002 stress the importance of multiyear studies to evaluate the effect of annual weather conditions on soil N2O dynamics. Key words: Greenhouse gasses, denitrification
Growing media, greenhouse tomato yield and Pythium root rot
Authors: Jean Caron Viviane Juneau, , Valérie Gravel Carole Martinez, , Allaire Suzanne
Published: April 2011

Increased environmental pressure is forcing the horticultural industry to look for new growing media in replacement of rockwool and high-quality peat substrates. The objectives of this study were to determine: (1) the effect of different substrates on greenhouse tomato (Lycopersicon esculentum Mill.) yield and root rot caused by Pythium, and (2) thethreshold values of some substrate physico-chemical properties for tomato yield and Pythium root rot. Two experiments (fall, spring) were conducted using five substrates. In the fall experiment, yield was related to water availability, as long as aeration was sufficient. In the spring experiment, yield depended on air storage and gas concentrations (O2, CO2) in the substrate because of their low aeration levels. The effect of substrate types and their physico-chemical properties on Pythium root rot varied according to the cultural conditions. Under fall cropping conditions, substrates showing wet and anaerobic conditions favoured Pythium root rot. In these experiments, adequate aeration properties for tomato plant productivity were obtained with a maximum of 30% low-quality peat added to a mixture of sawdust and compost. Key words: Growing media, irrigation strategies, physico-chemical properties, Pythium root rot, Lycopersicum esculentum
Comparison of soil test phosphorus methods in neutral to calcareous Manitoba soils
Authors: Ige D V , Akinremi O O , Flaten D. , Kashem M A
Published: April 2011

Increasing concern for the amount of P entering lakes in Manitoba may lead to regulation of P concentration in agricultural soils. A possible means for this regulation is the use of soil test P. This may require a means of comparing soil test P analyses as various laboratories in Manitoba employ different methods of soil test P determination. Thus, the objectives of this study were to (i) compare the methods of P determination in Manitoba soils, and (ii) develop equations for converting different soil test P methods from one to another. One hundred and fifteen archived surface soil samples representing major soils of Manitoba were used for the study. Soil test P was determined in these soils using the original Kelowna (K1) method and the two modified Kelowna methods (K2 and K3). Mehlich-3, Olsen- and water extractable-P were also determined for all soils. The results were analyzed statistically and were related using a simple regression analysis model. The amount of P extracted by the different extracting agents varied widely. Mehlich-3 extracted the largest amount of P (a range of 5.4–200 mg kg-1) while water extracted the smallest amount (a range of 0.2–70 mg kg-1). The P extracted by the Olsen and the three Kelowna methods were intermediate between Mehlich-3 and water-P. Our results also showed that the three Kelowna methods were not significantly different from one another. The Olsen method compared well with those of the modified Kelowna methods, but extracted less P than the original Kelowna and Mehlich-3 methods. Overall, the different agronomic soil test P methods were well correlated to each other with correlation coefficients (r) ranging between 0.95 and 0.98. However, the correlations between these soil test methods and water extractable P was not as high. Water extractable P and the agronomic soil test P methods were better related by a non-linear relationship than by a linear relationship. The coefficient of determination (R2) for all the regression equations relating the different agronomic soil test P methods ranged from 0.91 to 0.97. As such, the equations generated in this study can be used to convert the result from one soil test P method to another. Key words: Kelowna extractable phosphorus, Mehlich-3 extractable phosphorus, Olsen extractable phosphorus, water extractable phosphorus
Water-filled microbially habitable pores: Relation to denitrification
Authors: Novosad N. , Kay B. D.
Published: April 2011

The onset of a decline in net N mineralization, primarily due to denitrification, has been related to water contents, θW, or water-filled porosities, fW, but values of these characteristics vary among soils thus limiting their use as diagnostic criteria. An implicit assumption in the use of these characteristics is that water-filled pores of all sizes are habitable by microorganisms participating in denitrification. However, microorganisms are excluded from small pores, and the volume fraction of these pores varies with soil structure. The objective of this study was to determine if variation in the volume fraction of water-filled microbially habitable pores, θMHP, contributes to the variation in denitrification in soils of different structure. Data were used from studies with and without growing maize (Zea maize L.) plants. Variation in soil structure was achieved by using soils of different texture and organic carbon contents that were packed to two different levels of relative compaction. At the onset of a decrease in net N mineralization, values of θMHP exhibited less variability among soils than either θW or fW. The θMHP will be of greatest value as a diagnostic criterion for the decline in net N mineralization in soils exhibiting variation in the volume fraction of pores ≤ 4 µm diameter. Key words: Denitrification, habitable pore space, soil structure
Effects of erosion control practices on runoff, soil loss, and yield of strawberries in the Lower Fraser Valley
Authors: Vliet L. J. P. van , Hall J. W. , Fast D.
Published: April 2011

Erosion control practices were evaluated for their ability to reduce soil loss and runoff and for their effects on strawberry (Fragaria × ananassa Duch.) yield on a silt loam soil in the uplands area of the Lower Fraser Valley. Three treatments (underdrainage, winter cover cropping of barley [Hordeum vulgare L.] and cross slope planting) were compared to a control. Soil and runoff losses from natural rainfall were measured on replicated experimental plots (0.01375 ha) from 1991 to 1994. Soil and runoff losses were significantly lower with the winter cover crop and cross-slope planting treatments than the control. Results for the underdrainage treatment were not significantly different from the control and non-representative of proper underdrainage due to too deep an installation under wet conditions. Soil protection by the barley cover crop reduced mean annual soil loss and runoff by 78 and 43%, respectively. Cross slope planting reduced soil and runoff losses by 97 and 84%, respectively, compared with the control. Annual runoff coefficients of up to 21% were observed for the control, while coefficients of 40% were not uncommon for single storm events. Except for the cross slope treatment, strawberry yields were not compromised by the erosion control practices. Winter cover cropping is the preferred erosion control practice for strawberries grown on upland soils, since cross slope planting may cause depressed yields from root rot disease resulting from stagnant water between the rows.

Key words: Soil loss, runoff, runoff coefficient, cover crop, across slope, erosion control
Soil phosphorus saturation degree: Review of some indices and their suitability for P management in Québec, Canada
Authors: Beauchemin Suzanne , Simard R. R.
Published: April 2011

Many agricultural fields contain excessive labile soil P in regard to crop needs. Its environmental fate must be assessed. The concept of P saturation degree is meaningful as it describes the portion of the soil binding sites already covered with P, and indicates the potential desorbability of soil P. The first objective of this study was to review different indices that have been proposed to estimate the degree of soil P saturation and the relationships between soil P saturation degree and P solubility. The second objective is to discuss their suitability as environmental indicators for P management in the province of Québec, Canada. In the Netherlands, the P saturation index is defined as the ratio of P to Al + Fe contents extracted by ammonium oxalate [Pox/( Alox + Feox ) or ( Pox/0.5( Alox + Feox )]. This approach has been mainly used with non-calcareous soils. In Québec, the ratio of Mehlich-III extractable P to Al (M3P/AlM3) is proposed as an alternative, which relies on routine laboratory test. However, the suitability of the M3P/AlM3 ratio has yet to be determined for some specific soil groups (e.g. gleyed soils, soils with Alox content >6 g kg−1) and for subsoil horizons. Regardless of the chosen index, it is suggested that the best way to manage the risk of water contamination by P in Québec (namely, defining critical levels of soil P saturation) may be to form homogeneous soil groups to account for their distinctive behaviour and characteristics. Key words: Phosphorus, saturation, management
INSSECT—an instrumented platform for investigating floc properties close to the seabed
Authors: Mikkelsen Ole A. , Milligan Timothy G. , Hill Paul S. , Moffatt Dan
Published: April 2011

A new type of tripod, INSSECT (IN situ Size and SEttling Column Tripod), designed for floc measurements in the shallow parts of the continental shelf, is described. INSSECT orientates itself into the current so that instrumentation on it faces upstream, thereby minimizing flow disturbance. The instrumentation includes a digital floc camera, a video settling column, a unique sediment trap designed for capturing flocs intact, a laser sizer, an optical backscatterance sensor, a compass and tilt meter, and a current meter. It is designed for relatively short deployments of up to 2 weeks and can be recovered, turned around, and redeployed rapidly. It was designed for use in semi‐synoptic surveys of the spatial variation in floc properties such as size and settling velocity and the factors that influence them. The paper describes the various components of the INSSECT and presents selected results from the first deployments, demonstrating its ability to turn in the current and capture single flocs intact. Contrary to recent findings on the influence on settling columns on floc size, intercomparison between the video settling column and the digital floc camera reveals that the sizes are similar.
Composition of estuarine bacterial communities assessed by denaturing gradient gel electrophoresis and fluorescence in situ hybridization
Authors: Castle Dawn , Kirchman David L.
Published: April 2011

We compared the results from two culture‐independent techniques commonly used to investigate microbial community composition in aquatic ecosystems: fluorescence in situ hybridization (FISH) with oligonucleotide probes and denaturing gradient gel electrophoresis (DGGE). These two techniques were used with samples from the Delaware Estuary and from experiments in the estuary and Chesapeake Bay. Most of the ribotypes identified by DGGE were members of the phylogenetic groups identified by FISH (alpha, β, and γ proteobacteria and the Cytophaga‐like bacteria). DGGE and FISH usually (64% of all comparisons) identified the same phylogenetic group as being dominant, and both methods revealed systematic changes in bacterial community structure along the estuarine gradient. Cytophaga‐like bacteria appeared to be sampled adequately by DGGE, even though bacteria from this cluster are often underrepresented in clone libraries of 16S rRNA genes. However, there were notable instances when DGGE and FISH failed to identify the same phylogenetic group as being most abundant. In several cases, the dominant group was β‐proteobacteria according to FISH but these bacteria were absent in DGGE gels.
Preparation of natural methane samples for stable isotope and radiocarbon analysis
Authors: Kessler John D. , Reeburgh William S.
Published: April 2011

We describe procedures for preparing methane samples from natural waters or sediments for radiocarbon (14C‐CH4) analysis. These procedures also allow the determination of 2H/1H and 13C/12C ratios of this methane. Methane is extracted from natural samples in the field using Lamont radon stripping boards (Mathieu et al. 1988) and trapped using liquid nitrogen‐cooled U‐traps filled with HiSiv 3000. The field procedures eliminate the need to return large samples to the laboratory. The U‐traps are returned to the laboratory where a new twostage purification‐oxidation vacuum line is used to extract, purify, and oxidize the methane. The methane oxidation products (carbon dioxide and water) are analyzed for the natural content of 14C, 2H, and 13C with standard procedures. These procedures were evaluated under the conditions that methane was extracted from between 19 to 114 L water or 0.07 to 0.35 L sediment. No isotope fractionation was observed and the blanks are small (0.528 ± 0.39 µmol methane with radiocarbon content 14C/C = 96.1 ± 0.3 pMC [percent Modern Carbon] [Stuiver and Polach 1977]). Using 14C‐accelerator mass spectrometry (AMS), these procedures can produce a successful radiocarbon measurement when at least 1.81 µmol methane are collected. Thus, 14C‐CH4 measurements can be made when the dissolved methane concentration is between saturation (mM) and 15.9 nM for the water column or 5.2 µM for the sediment.
As limitações dos sistemas de metas
Authors: Reis Neto Mário Teixeira , Couto João Henrique Soares do , Gonçalves Carlos Alberto
Published: April 2011

Neste ambiente de grandes incertezas em que as organizações estão inseridas, a correta utilização de um sistema de medição pode significar vantagem competitiva e desempenho. Este ensaio procura esclarecer os limites dos sistemas de medição, verificando se a utilização de metas de resultado é suficiente para que uma empresa tenha um desempenho superior. O objetivo é analisar a teoria das metas sob um olhar crítico, observando os limites da utilização de diversos tipos de metas, até mesmo no serviço público. Buscou-se fazer uma análise das pesquisas dos autores que defendem a utilização de metas para se ter desempenho e, a partir das suas premissas, analisar os estudos dos autores que as criticam, mostrando que elas podem causar, dependendo da situação, sérios danos financeiros e à imagem da organização. Após essa análise, verificou-se que as metas possuem um importante papel no aumento do desempenho da organização, todavia, deve-se ter certo cuidado na sua utilização, pois elas podem levar as pessoas a comportamentos não éticos, à inibição da cooperação e do aprendizado organizacional, entre outros.
Capacitação gerencial nas incubadoras de base tecnológica: proposição de um modelo matricial de avaliação
Authors: Xavier Wescley Silva , Martins Guilherme Silveira , De Carvalho Lima Afonso Augusto Teixeira de Freitas
Published: April 2011

Este trabalho tem como objetivo a proposição de uma ferramenta de avaliação de programas de capacitação gerencial de Incubadoras de Empresas. Tal ferramenta foi desenvolvida a partir de um estudo em 14 Incubadoras e 115 empreendimentos nascentes de base tecnológica. A avaliação é realizada nas tradicionais áreas funcionais da Administração (i.e. Marketing, Recursos Humanos, Finanças e Operações) em duas dimensões: (a) uma compara o domínio que o empresário julga possuir dos fundamentos de cada disciplina da Administração e a importância que esses fundamentos têm para o seu negócio; (b) a outra dimensão compara essa importância atribuída pelo empresário com o quanto o fundamento foi contemplado no programa de capacitação gerencial oferecido pela incubadora. Com isso, é possível avaliar, respectivamente, as lacunas de conhecimento que os empresários julgam possuir e quais pontos podem ser mais bem explorados pela incubadora nos treinamentos gerenciais. O estudo de campo revelou que os fundamentos de Marketing e Finanças são vistoscomo mais importantes pelos empresários e mais contemplados nos programas de capacitação. Ademais, verificou-se a existência de lacunas entre importância atribuída pelos empresários e a efetividade da incubadora em alguns elementos, o que sugere a necessidade de reavaliar os programas de capacitação gerencial.
Airborne observation of aerosol optical depth during ARCTAS: vertical profiles, inter-comparison and fine-mode fraction
Authors: Shinozuka Y. , Redemann J. , Livingston J. M. , Russell P. B. , Clarke A. D. , Howell S. G. , Freitag S. , O'Neill N. T. , Reid E. A. , Johnson R. , Ramachandran S. , McNaughton C. S. , Kapustin V. N. , Brekhovskikh V. , Holben B. N. , McArthur L. J. B.
Published: April 2011

Abstract. We describe aerosol optical depth (AOD) measured during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment, focusing on vertical profiles, inter-comparison with correlative observations and fine-mode fraction. Arctic haze observed in <2 km and 2–4 km over Alaska in April 2008 originated mainly from anthropogenic emission and biomass burning, respectively, according to aerosol mass spectrometry and black carbon incandescence measurements. The Ångström exponent for these air masses is 1.4 ± 0.3 and 1.7 ± 0.1, respectively, when derived at 499 nm from a second-order polynomial fit to the AOD spectra measured with the 14-channel Ames Airborne Tracking Sunphotometer (AATS-14) over 354–2139 nm. We examine 55 vertical profiles selected from all phases of the experiment. For two thirds of them, the AOD spectra are within 3% + 0.02 of the vertical integral of local visible-light scattering and absorption. The horizontal structure of smoke plumes from local biomass burning observed in central Canada in June and July 2008 explains most outliers. The differences in mid-visible Ångström exponent are <0.10 for 63% of the profiles with 499-nm AOD > 0.1. The retrieved fine-mode fraction of AOD is mostly between 0.7 and 1.0, and its root mean square difference (in both directions) from column-integral submicron fraction (measured with nephelometers, absorption photometers and an impactor) is 0.12. These AOD measurements from the NASA P-3 aircraft, after compensation for below-aircraft light attenuation by vertical extrapolation, mostly fall within ±0.02 of AERONET ground-based measurements between 340–1640 nm for five overpass events.
Source attribution of the changes in atmospheric methane for 2006–2008
Authors: Bousquet P. , Ringeval B. , Pison I. , Dlugokencky E. J. , Brunke E.-G. , Carouge C. , Chevallier F. , Fortems-Cheiney A. , Frankenberg C. , Hauglustaine D. A. , Krummel P. B. , Langenfelds R. L. , Ramonet M. , Schmidt M. , Steele L. P. , Szopa S. , Yver C. , Viovy N. , Ciais P.
Published: April 2011

Abstract. The recent increase of atmospheric methane is investigated by using two atmospheric inversions to quantify the distribution of sources and sinks for the 2006–2008 period, and a process-based model of methane emissions by natural wetland ecosystems. Methane emissions derived from the two inversions are consistent at a global scale: emissions are decreased in 2006 (−7 Tg) and increased in 2007 (+21 Tg) and 2008 (+18 Tg), as compared to the 1999–2006 period. The agreement on the latitudinal partition of the flux anomalies for the two inversions is fair in 2006, good in 2007, and not good in 2008. In 2007, a positive anomaly of tropical emissions is found to be the main contributor to the global emission anomalies (~60–80%) for both inversions, with a dominant share attributed to natural wetlands (~2/3), and a significant contribution from high latitudes (~25%). The wetland ecosystem model produces smaller and more balanced positive emission anomalies between the tropics and the high latitudes for 2006, 2007 and 2008, mainly due to precipitation changes during these years. At a global scale, the agreement between the ecosystem model and the inversions is good in 2008 but not satisfying in 2006 and 2007. Tropical South America and Boreal Eurasia appear to be major contributors to variations in methane emissions consistently in the inversions and the ecosystem model. Finally, changes in OH radicals during 2006–2008 are found to be less than 1% in inversions, with only a small impact on the inferred methane emissions.
The Eyjafjöll explosive volcanic eruption from a microwave weather radar perspective
Authors: Marzano F. S. , Lamantea M. , Montopoli M. , Di Fabio S. , Picciotti E.
Published: April 2011

Abstract. The sub-glacial Eyjafjöll explosive volcanic eruptions of April and May 2010 are analyzed and quantitatively interpreted by using ground-based weather radar data and volcanic ash radar retrieval (VARR) technique. The Eyjafjöll eruptions have been continuously monitored by the Keflavík C-band weather radar, located at a distance of about 155 km from the volcano vent. Considering that the Eyjafjöll volcano is approximately 20 km far from the Atlantic Ocean and that the northerly winds stretched the plume toward the mainland Europe, weather radars are the only means to provide an estimate of the total ejected tephra. The VARR methodology is summarized and applied to available radar time series to estimate the plume maximum height, ash particle category, ash volume, ash fallout and ash concentration every 5 min near the vent. Estimates of the discharge rate of eruption, based on the retrieved ash plume top height, are provided together with an evaluation of the total erupted mass and volume. Deposited ash at ground is also retrieved from radar data by empirically reconstructing the vertical profile of radar reflectivity and estimating the near-surface ash fallout. Radar-based retrieval results cannot be compared with ground measurements, due to the lack of the latter, but further demonstrate the unique contribution of these remote sensing products to the understating and modelling of explosive volcanic ash eruptions.
Microphysical simulations of new particle formation in the upper troposphere and lower stratosphere
Authors: English J. M. , Toon O. B. , Mills M. J. , Yu F.
Published: April 2011

Abstract. Using a three-dimensional general circulation model with sulfur chemistry and sectional aerosol microphysics (WACCM/CARMA), we studied aerosol formation and microphysics in the tropical upper troposphere and lower stratosphere (UTLS) based on three nucleation schemes (two binary homogeneous schemes and an ion-mediated scheme). Simulations suggest that ion-mediated nucleation rates in the UTLS are 25% higher than binary rates, but that the rates predicted by the two binary schemes vary by two orders of magnitude. However, it is found that coagulation, not nucleation, controls number concentration at sizes greater than approximately 10 nm. Therefore, based on this study, atmospherically relevant processes in the UTLS are not sensitive to the choice of nucleation schemes. The dominance of coagulation over other microphysical processes is consistent with other recent work using microphysical models. Simulations using all three nucleation schemes compare reasonably well to observations of size distributions, number concentration across latitude, and vertical profiles of particle mixing ratio in the UTLS. Interestingly, we find we need to include Van der Waals forces in our coagulation scheme to match the UTLS aerosol concentrations. We conclude that this model can accurately represent sulfate microphysical processes in the UTLS, and that the properties of particles at atmospherically relevant sizes are not sensitive to the details of the nucleation scheme. We also suggest that micrometeorites, which are not included in this model, dominate the aerosol properties in the upper stratosphere above about 30 km.
A multi-angle aerosol optical depth retrieval algorithm for geostationary satellite data over the United States
Authors: Zhang H. , Lyapustin A. , Wang Y. , Kondragunta S. , Laszlo I. , Ciren P. , Hoff R. M.
Published: April 2011

Abstract. Aerosol optical depth (AOD) retrieval from geostationary satellites has high temporal resolution compared to the polar orbiting satellites and thus enables us to monitor aerosol motion. However, current Geostationary Operational Environmental Satellites (GOES) have only one visible channel for retrieving aerosol and hence the retrieval accuracy is lower than those from the multichannel polar-orbiting satellite instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS). The operational GOES AOD retrieval algorithm (GOES Aerosol/Smoke Product, GASP) uses 28-day composite images from the visible channel to derive surface reflectance, which can produce large uncertainties. In this work, we develop a new AOD retrieval algorithm for the GOES imager by applying a modified multi-angle Implementation of Atmospheric Correction (MAIAC) algorithm. The algorithm assumes the surface Bidirectional Reflectance Distribution Function (BRDF) at channel 1 of GOES is proportional to seasonal average BRDF in the 2.1 μm channel from MODIS. The ratios between them are derived through time series analysis of the GOES visible channel images. The results of the AOD and surface reflectance retrievals are evaluated through comparison against those from Aerosol Robotic Network (AERONET), GASP, and MODIS. The AOD retrievals from the new algorithm demonstrate good agreement with AERONET retrievals at several sites across the US. They are comparable to the GASP retrievals in the eastern-central sites and are more accurate than GASP retrievals in the western sites. In the western US where surface reflectance is high, the new algorithm also produces larger AOD retrieval coverage than both GASP and MODIS.
Recovery of GPP monthly pattern in a eucalypt site in Portugal after felling
Authors: Rodrigues A. , Pita G.
Published: April 2011

Abstract. The main objective of this work was to report the recovery of seasonal pattern of GPP obtained by eddy covariance measurements in a eucalypt (Eucalyptus globulus Labill.) site in Pegões (Southern Portugal) after a felling processed in October and November of 2006. This was made in a wider context of a general description of the evolution of carbon sequestration at several timescales in the period 2002–2010. In Portugal eucalypt stands aimed mainly for pulp production occupies an area of about 739 515 ha, (National Forest Inv 2005–2006) corresponding to about 23% of total forest area. The site is part of a 300 ha eucalypt stand, located in Herdade da Espirra, intensively managed as coppice under a twelve year productive cycle with a density of about 1100 trees/ha and characterized by a 12-month growing period. A prolonged drought in 2004 and 2005 and a felling in October–November 2006, followed by the start of a new production cycle, changed the carbon sink ability of eucalypt stand. In the two drought years, rainfall was reduced to values of 50%, relatively to long-term 709 mm average of. In the period prior to cutting NEE of 8.7 g cm−2 was maximum in 2002 decreasing to a minimum of 3.6 tons/ha in 2005 at the peak of the effect of drought. After the felling the eucalypt stand recovered its carbon sink capacity in June 2007 with an annual GPP of 1621.6 g cm−2 in 2010. Seasonal patterns of GPP in 2007, 2008 and 2009 were almost opposite to that of the period before the felling, with a tendency to recover to the situation prior the felling in 2010.
Consistent calculation of aquatic gross production from oxygen triple isotope measurements
Authors: Kaiser J.
Published: April 2011

Abstract. Oxygen triple isotope measurements can be used to calculate aquatic gross oxygen production rates. Past studies have emphasised the appropriate definition of the 17O excess and often used an approximation to derive production rates from the 17O excess. Here, I show that the calculation can be phrased more consistently and without any approximations using the relative 17O/16O and 18O/16O isotope ratio differences directly. The 17O excess is merely a mathematical construct and the derived production rate is independent of its definition, provided all calculations are performed with a consistent definition. I focus on the mixed layer, but also show how time series of triple oxygen measurements below the mixed layer can be used to derive gross production. In the calculation of mixed layer productivity, I explicitly include isotopic fractionation during gas invasion and evasion, which requires the oxygen supersaturation s to be measured as well. I also suggest how bubble injection could be considered in the same mathematical framework. I distinguish between concentration steady state and isotopic steady state and show that only the latter needs to be assumed in the calculation. It is even possible to derive an estimate of the net production rate in the mixed layer that is independent of the assumption of concentration steady state. I review measurements of the parameters required for the calculation of gross production rates and show how their systematic uncertainties as well as the use of different published calculation methods can cause large variations in the production rates for the same underlying isotope ratios. In particular, the 17O excess of dissolved O2 in equilibrium with atmospheric O2 and the 17O excess of photosynthetic O2 need to be re-measured. Because of these uncertainties, all calculation parameters should always be fully documented and the measured isotope ratio differences as well as the oxygen supersaturation should be permanently archived, so that improved measurements of the calculation parameters can be used to retrospectively improve production rates.
Raising the Dead without a Red Sea-Dead Sea project? Hydro-economics and governance
Authors: Rosenberg D. E.
Published: April 2011

Abstract. Seven decades of extractions have dramatically reduced Jordan River flows, lowered the Dead Sea level, opened sink holes, and caused other environmental problems. The fix Jordan, Israel, and the Palestinians propose would build an expensive multipurpose conveyance project from the Red Sea to the Dead Sea that would also generate hydropower and desalinate water. This paper compares the Red-Dead project to alternatives that may also raise the Dead Sea level. Hydro-economic model results for the Jordan-Israel-Palestinian inter-tied water systems show two restoration alternatives are more economically viable than the proposed Red-Dead project. Many decentralized new supply, wastewater reuse, conveyance, conservation, and leak reduction projects and programs in each country can together increase economic benefits and reliably deliver up to 900 MCM yr−1 to the Dead Sea. Similarly, a smaller Red-Dead project that only generates hydropower can deliver large flows to the Dead Sea when the sale price of generated electricity is sufficiently high. However, for all restoration options, net benefits fall and water scarcity rises as flows to the Dead Sea increase. This finding suggests (i) each country has no individual incentive to return water to the Dead Sea, and (ii) outside institutions that seek to raise the Dead must also offer countries direct incentives to deliver water to the Sea besides building the countries new infrastructure.