Impacts of cover crops and crop residues on phosphorus losses in cold climates: a review

Non-Peer ReviewedThe use of plants in riparian buffers or cover crops is widely proposed as a strategy to mitigate sediment and nutrient losses from land to water. In cold climates, concerns may arise with regard to potentially elevated phosphorus (P) losses associated with freeze-thaw of plant materials. Here, we review the impacts of cover crops and crop residues on P loss in cold climates, and explore linkages between water extractable P in the plant materials and P loss in surface runoff and subsurface drainage from cropped soils. Water extractable P in plants is greatly affected by crop species and hardiness, as well as freezing regimes including both freezing temperature and the number of freeze-thaw cycles. Although controls on water extractable P in plant tissues and residues are relatively well understood, impacts on P runoff and leaching are inconsistent across studies due to the influences of soil, climate, and management factors. This review sheds light on improving winter crop cover management to minimize P losses from land to water in cold climates and points to future research needs. Specifically, more research is needed to understand interactions between soil, plant, hydrology, and management in influencing P loss, and to improve the assessment of crop contributions to P loss in field settings of cold climates. Further, the trade-offs between the concern over P and the control of sediment loss and nitrogen leaching should be acknowledged, as should the uncertainties of freezing and crop adaptability under future climate regimes

Untersuchungen von Beugesehnennähten mittels Bildsequenzanalyse im Experiment

Im Rahmen dieser Arbeit werden die Ergebnisse aus Zugversuchen an Schweinesehnen, die mit verschiedenen Nahtmaterialien und den gängigen Nahttechniken für Beugesehnen der Hand genäht wurden, vorgestellt. Schwerpunkt der Untersuchungen ist die Ermittlung und Dokumentation der Reißfestigkeit der Naht und die Spaltbildung an der Kontaktstelle der genähten Sehnenstümpfe mittels biomechanischer Versuche. Das Eintreten der Spaltbildung und des Nahtrisses wird durch videotechnische Aufzeichnungen, die den eigentlichen Messvorgang an der Universalprüfmaschine begleiten, exakt dokumentiert (Bildsequenzanalyse). Die Bildsequenzanalyse stellt gegenüber den in der Literatur dokumentierten Methoden eine wesentliche Fort- bzw. Neuentwicklung zur Ermittlung der Spaltstabilität und der Reißfestigkeit von genähten Sehnen dar. Die Auswertung der Versuche mittels Bildsequenzanalyse wurde für 12 verschiedene Nahttechnik/Nahtmaterial-Kombinationen durchgeführt. Nach Entwicklung und Anfertigung einer neuen Einspannvorrichtung für die Sehnen, die eine optimale Festhaltung der Sehnenstümpfe gewährleistete, erfolgte die systematische Durchführung von Bildsequenzanalysen für gängige Sehnennaht-Techniken mit verschiedenen Fäden. Auf Grundlage der biomechanischen Versuche und der Weiterentwicklung bisheriger Kenntnisse zur Beugesehnennaht konnte im Rahmen dieser Arbeit eine optimierte bzw. eine neue Nahttechnik entwickelt werden (Marburger Sehnennaht I und II), die eine frühe postoperative Mobilisierung durch entsprechende Nahtfestigkeiten ermöglicht, eine gute Gleitfunktion aufweist sowie durch Erhaltung der Gefäßversorgung der Sehne einen sicheren Heilungsprozess gewährleistet. Die Ergebnisse der biomechanischen Versuche mit der Marburger Sehnennaht I und II sind in dieser Arbeit detailliert dokumentiert. Der Vergleich mit den gängigen Sehnennaht-Techniken zeigt, dass die Marburger Sehnennaht eine hohe Reißfestigkeit und die beste Spaltstabilität besitzt

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II ? gas phase reactions of organic species

International audienceThis article, the second in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Organic species, which were last published in 1999, and were updated on the IUPAC website in late 2002, and subsequently during the preparation of this article. The article consists of a summary table of the recommended rate coefficients, containing the recommended kinetic parameters for the evaluated reactions, and eight appendices containing the data sheets, which provide information upon which the recommendations are made

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume III ? gas phase reactions of inorganic halogens

International audienceThis article, the third in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of inorganic halogen species, which were last published in J. Phys. Chem. Ref. Data, in 2000 (Atkinson et al., 2000), were updated on the IUPAC website in 2003 and are updated again in the present evaluation. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and five appendices containing the data sheets, which provide information upon which the recommendations were made

Glycolaldehyde formation via the dimerization of the formyl radical

Glycolaldehyde, the simplest monosaccharide sugar, has recently been detected in low- and high-mass star-forming cores. Following our previous investigation into glycolaldehyde formation, we now consider a further mechanism for the formation of glycolaldehyde that involves the dimerization of the formyl radical, HCO. Quantum mechanical investigation of the HCO dimerization process upon an ice surface is predicted to be barrierless and therefore fast. In an astrophysical context, we show that this mechanism can be very efficient in star-forming cores. It is limited by the availability of the formyl radical, but models suggest that only very small amounts of CO are required to be converted to HCO to meet the observational constraints

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume IV – gas phase reactions of organic halogen species

This article, the fourth in the series, presents kinetic and photochemical data sheets evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of organic halogen species, which were last published in 1997, and were updated on the IUPAC website in 2006/07. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and four appendices containing the data sheets, which provide information upon which the recommendations are made

Who smells? Forecasting taste and odor in a drinking water reservoir

Taste and odor problems can impede public trust in drinking water and impose major costs on water utilities. The ability to forecast taste and odor events in source waters, in advance, is shown for the first time in this paper. This could allow water utilities to adapt treatment, and where effective treatment is not available, consumers could be warned. A unique 24-year time series, from an important drinking water reservoir in Saskatchewan, Canada, is used to develop forecasting models of odor using chlorophyll a, turbidity, total phosphorus, temperature, and the following odor producing algae taxa: Anabaena spp., Aphanizemenon spp., Oscillatoria spp., Chlorophyta, Cyclotella spp., and Asterionella spp. We demonstrate, using linear regression and random forest models, that odor events can be forecast at 0-26 week time lags, and that the models are able to capture a significant increase in threshold odor number in the mid-1990s. Models with a fortnight time-lag show a high predictive capacity (R2 = 0.71 for random forest; 0.52 for linear regression). Predictive skill declines for time lags from 0 to 15 weeks, then increases again, to R2 values of 0.61 (random forest) and 0.48 (linear regression) at a 26-week lag. The random forest model is also able to provide accurate forecasting of TON levels requiring treatment 12 weeks in advance-93% true positive rate with a 0% false positive rate. Results of the random forest model demonstrate that phytoplankton taxonomic data outperform chlorophyll a in terms of predictive importance

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species

This article, the second in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Organic species, which were last published in 1999, and were updated on the IUPAC website in late 2002, and subsequently during the preparation of this article. The article consists of a summary table of the recommended rate coefficients, containing the recommended kinetic parameters for the evaluated reactions, and eight appendices containing the data sheets, which provide information upon which the recommendations are made

Differences in atmospheric phosphorus deposition amongst rural and urban land use locations in Missouri

Atmospheric phosphorus (AP) produced by both anthropogenic and natural processes influences phytoplankton productivity and alters carbon processing in water bodies, resulting in potential impairment and toxic phytoplankton blooms. The production of AP, which is oftentimes transported vast distances by wind dispersal in the form of enriched mineral dust, can be re-deposited by wet (precipitation based) or dry (continual) deposition. Both rural and urban locations in Missouri experience varying anthropogenic activities; therefore, distinguishing between varying land use locations at these sites provides insight as to why AP may differ. The objective of this study is to determine if AP deposition differs among rural and urban land use locations in Missouri. When soil has been recently agitated and readily exposed, we hypothesize this additional P in the atmosphere will result in higher bulk deposition flux totals (BD) in rural locations. AP was collected from three rural locations and three urban locations, using a standard sized utility bucket, altered to reduce debris. After each two-week sampling period, a total sample water volume for each site is collected, total P is analyzed (TP), which determines the BD flux of each site by factoring the time it took to collect each sample (4 samples over approximately 70 days). Rural locations had the highest BD. Rural locations were not significantly different than urban locations (F5,18 = 1.667, p = 0.194). Further analysis of AP and the implication on water bodies is needed, as AP analysis is exceedingly rare. A multitude of differing land use practices results in variables that contribute significantly to the production of AP.Crystal Rein, Sarahi Viscarra Arellano, Karl Friesen-Hughes, Ashley King, Alexia Marten, Corey Sanderson, Jason J Venkiteswaran, Helen Baulch, Nora Jessie Casson, Colin J Whitfield, and Rebecca North (University of Missouri, University of Saskatchewan, Wilfrid Laurier University, University of Winnipeg

Carbon monoxide in the solar atmosphere I. Numerical method and two-dimensional models

The radiation hydrodynamic code CO5BOLD has been supplemented with the time-dependent treatment of chemical reaction networks. Advection of particle densities due to the hydrodynamic flow field is also included. The radiative transfer is treated frequency-independently, i.e. grey, so far. The upgraded code has been applied to two-dimensional simulations of carbon monoxide (CO) in the non-magnetic solar photosphere and low chromosphere. For this purpose a reaction network has been constructed, taking into account the reactions which are most important for the formation and dissociation of CO under the physical conditions of the solar atmosphere. The network has been strongly reduced to 27 reactions, involving the chemical species H, H2, C, O, CO, CH, OH, and a representative metal. The resulting CO number density is highest in the cool regions of the reversed granulation pattern at mid-photospheric heights and decreases strongly above. There, the CO abundance stays close to a value of 8.3 on the usual logarithmic abundance scale with [H]=12 but is reduced in hot shock waves which are a ubiquitous phenomenon of the model atmosphere. For comparison, the corresponding equilibrium densities have been calculated, based on the reaction network but also under assumption of instantaneous chemical equilibrium by applying the Rybicki & Hummer (RH) code by Uitenbroek (2001). Owing to the short chemical timescales, the assumption holds for a large fraction of the atmosphere, in particular the photosphere. In contrast, the CO number density deviates strongly from the corresponding equilibrium value in the vicinity of chromospheric shock waves. Simulations with altered reaction network clearly show that the formation channel via hydroxide (OH) is the most important one under the conditions of the solar atmosphere.Comment: 15 pages, 6 figures, final version will contain online materia