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Understanding isoprene photooxidation using observations and modeling over a subtropical forest in the southeastern US
Su, Luping ; Patton, Edward G. ; Vilà-guerau De Arellano, Jordi ; Guenther, Alex B. ; Kaser, Lisa ; Yuan, Bin ; Xiong, Fulizi ; Shepson, Paul B. ; Zhang, Li ; Miller, David O. ; Brune, William H. ; Baumann, Karsten ; Edgerton, Eric ; Weinheimer, Andrew ; Misztal, Pawel K. ; Park, Jeong-Hoo ; Goldstein, Allen H. ; Skog, Kate M. ; Keutsch, Frank N. ; Mak, John E. - \ 2016
Atmospheric Chemistry and Physics 16 (2016)12. - ISSN 1680-7316 - p. 7725 - 7741.
The emission, dispersion, and photochemistry of isoprene (C5H8) and related chemical species in the convective boundary layer (CBL) during sunlit daytime were studied over a mixed forest in the southeastern United States by combining ground-based and aircraft observations. Fluxes of isoprene and monoterpenes were quantified at the top of the forest canopy using a high-resolution proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS). Snapshot (∼ 2 min sampling duration) vertical profiles of isoprene, methyl vinyl ketone (MVK) + methacrolein (MACR), and monoterpenes were collected from aircraft every hour in the CBL (100–1000 m). Both ground-based and airborne collected volatile organic compound (VOC) data are used to constrain the initial conditions of a mixed-layer chemistry model (MXLCH), which is applied to examine the chemical evolution of the O3–NOx–HOx–VOC system and how it is affected by boundary layer dynamics in the CBL. The chemical loss rate of isoprene (∼ 1 h) is similar to the turbulent mixing timescale (0.1–0.5 h), which indicates that isoprene concentrations are equally dependent on both photooxidation and boundary layer dynamics. Analysis of a model-derived concentration budget suggests that diurnal evolution of isoprene inside the CBL is mainly controlled by surface emissions and chemical loss; the diurnal evolution of O3 is dominated by entrainment. The NO to HO2 ratio (NO : HO2) is used as an indicator of anthropogenic impact on the CBL chemical composition and spans a wide range (1–163). The fate of hydroxyl-substituted isoprene peroxyl radical (HOC5H8OO·; ISOPOO) is strongly affected by NO : HO2, shifting from NO-dominant to NO–HO2-balanced conditions from early morning to noontime. This chemical regime change is reflected in the diurnal evolution of isoprene hydroxynitrates (ISOPN) and isoprene hydroxy hydroperoxides (ISOPOOH).
Methods for landscape monitoring compared
Dirkx, G.H.P. - \ 2010
In: Mapping and Monitoring of Nordic Vegetation and Landscapes. Conference proceedings, Hveragerði, Iceland, 16 18 September, 2009. - Noorwegen : Viten fra Skog og Landskap - p. 29 - 32.
There is currently no landscape monitoring programme being carried out in the Netherlands, which hampers attempts to describe trends in the Dutch landscape and to assess the effectiveness of landscape policy. Several landscape monitoring methods have been explored in the past few years. In view of the lack of field data, much effort has been invested to explore opportunities for landscape monitoring using already available data. One of the sources is the GIS version of the topographical map of the Netherlands. In addition, methods for gathering information from digital aerial photographs have been explored, using manual methods as well as computerised remote sensing techniques. Finally, also field work methods have been explored, ranging from a detailed approach - in which detailed data on all landscape elements in a region are collected - to smart sampling methods enabling reliable assessments of landscape changes using a minimum of samples. An assessment of the various methods shows that a mix of methods is the most effective approach. Whereas reliable data on new buildings, as well as data on infrastructure and land use, can be gathered from existing topographical data, such topographical databases do not allow data on landscape elements like wooded banks and hedgerows to be gathered. The best source of information for this kind of data was found to be aerial photographs. Manual analysis of aerial photographs, as well as the use of computerised remote sensing techniques, turns out to be costly. Field work, which is very expensive, is only necessary to check the information gained from aerial photographs.
Kinetic modelling: A tool to predict the formation of acrylamide in potato crisps
Knol, J.J. ; Viklund, G.Å.I. ; Linssen, J.P.H. ; Sjöholm, I.M. ; Skog, K.I. ; Boekel, M.A.J.S. van - \ 2009
Food Chemistry 113 (2009)1. - ISSN 0308-8146 - p. 103 - 109.
dietary acrylamide - maillard reaction - breast-cancer - fried potato - asparagine - risk - products - exposure - systems - bladder
Three empirical models were used to fit the formation of acrylamide in crisps of three different cold-sweetened potato genotypes, fried under the same experimental conditions. Statistical methods were used to compare the performance of the models, with the 'Logistic-Exponential' model performing the best. The obtained model parameters for the formation of acrylamide showed improvement in precision compared to an earlier study, the precision of the parameter estimates for the degradation of acrylamide was still problematic. Nevertheless, the predictive capacity of the 'Logistic-Exponential' model was tested, as this model showed a strong correlation between parameter a and the reducing sugar content of the raw potato. The predictions from this model for the formation of acrylamide in potato crisps were close to earlier reported experimental values. Therefore, the use of the 'Logistic-Exponential' model as a tool to predict acrylamide in potato crisps seems promising and should be developed further.
A study on the use of empirical models to predict the formation of acrylamide in potato crisps
Knol, J.J. ; Viklund, G.Å.I. ; Linssen, J.P.H. ; Sjöholm, I.M. ; Skog, K.I. ; Boekel, M.A.J.S. van - \ 2008
Molecular Nutrition & Food Research 52 (2008)3. - ISSN 1613-4125 - p. 313 - 321.
maillard reaction - fried potato - asparagine - systems - foods - temperature - variety - color - wheat - chips
The formation of acrylamide in potato crisps was fitted by empirical mathematical models. Potato slices were fried under the same experimental conditions for different times. Besides the content of precursors in the raw potato slices, acrylamide and water content in the potato crisps were quantified after predetermined times (2-6 min). The temperature developments in the surrounding oil and outer cell layer of the potato slices were monitored, giving more insight in the frying process and making future comparisons between studies possible. The pattern found for the formation of acrylamide, which was similar to earlier studies, was fitted to three empirical models. Statistical methods were used to compare the performance of the models, with the Logistic-Exponential and Empirical model performing equally well. The obtained model parameters were in the range of earlier reported studies, although this comparison is not unequivocal as the experimental conditions differed between studies. The precision of parameter estimates was problematic; this should be improved by better experimental design. Nevertheless, the approach of this study will make it possible to truly compare acrylamide formation patterns and model parameters in the future, with the ability to develop a tool to predict acrylamide formation in potato crisps.
Heat-Generated Food Toxicants; Identification, Characterisation and Risk Minimisation
Skog, K.I. ; Murkovic, M. ; Mottram, D. ; Boekel, T. van; Zondervan, C. ; Klaveren, J.D. van - \ 2007
National Veterinary Institute, Norway
voedselveiligheid - risicovermindering - eten koken - warmtebehandeling - food safety - risk reduction - cooking - heat treatment
Main results of the HEATOX Project. The main objectives were to: estimate health risks that may be associated with hazardous compounds in heat-treated food and: find cooking/processing methods which minimise the amounts of these compounds, thereby providing safe, nutritious and high-quality food-stuffs
Modelling of dietary exposure to acrylamide
Klaveren, J.D. van; Boon, P.E. ; Mul, A. de - \ 2006
In: Acrylamide and other hazardous compounds in heat-treated foods / Skog, K., Alexander, J., Cambridge, England : Woodhead Publishing Limited - ISBN 9781845690113 - p. 195 - 213.
Formation of Heterocyclic Amines in a Meat Juice Model System
Arvidsson, P. ; Boekel, M.A.J.S. van; Skog, K. ; Solyakov, A. ; Jägerstad, M. - \ 1999
Journal of Food Science 64 (1999). - ISSN 0022-1147 - p. 216 - 221.
|Formation of mutagenic Maillard Reaction products.
Arvidsson, P. ; Boekel, M.A.J.S. van; Skog, K. ; Jagerstad, M. - \ 1998
In: The Maillard Reaction in Foods and Medicine / O'Brien, J., Nursten, H.E., Crabbe, J., Ames, J.F., - p. 219 - 224.
Kinetics of formation of polar heterocyclic amines in a meat model system.
Arvidsson, P. ; Boekel, M.A.J.S. van; Skog, K. ; Jägerstad, M. - \ 1997
Journal of Food Science 62 (1997). - ISSN 0022-1147 - p. 911 - 916.