TEMPORAL VARIABILITY OF N2O FLUXES FROM A FERTILIZED GRASSLAND: PRELIMINARY RESULTS FROM DYNAMIC CLOSED CHAMBERS

Poster (2013, April 09)

This work presents preliminary results of nitrous oxide (N2O) fluxes measured by dynamic closed chambers from a fertilized grassland grazed by the Belgian Blue breed of cattle. It is part of a project ... [more ▼]

This work presents preliminary results of nitrous oxide (N2O) fluxes measured by dynamic closed chambers from a fertilized grassland grazed by the Belgian Blue breed of cattle. It is part of a project funded by the public service of Wallonia (SPW-DGARNE), whose objectives are to make a carbon/CO2 balance of the grassland (Jérôme et al., 2013) and to quantify CH4 (Dumortier et al., 2013) and N2O fluxes. The site is located in Dorinne (Dorinne Terrestrial Observatory), Belgium (50° 18’ 44” N; 4° 58’ 07” E; 248 m al.). It is a permanent grassland of ca. 4.2 ha with a moderate slope of 1 to 2 %. Mineral fertilisation took place in March and May 2012. Two cylindrical chambers of 19,2 cm diameter and 11,5 cm height were placed inside a protected area around a micrometeorological station. An infrared gas analyser (Thermofischer 46i) was used in order to measure the N2O concentrations inside of the chambers, closed by automatically controlled lids and ventilated by a constant air flow of 1liter/min. These devices were completed by adjacent soil humidity and temperature sensors. The first measurement campaign took place during June and July 2012. The chambers were installed in the field and N2O fluxes were followed without manipulation. N2O fluxes were characterised by a background emission (between 2 and 10 ngN.m2s􀀀1) on which intense but time limited peaks (between 50 and 300 ngN.m2s􀀀1) superimposed. Peaks were found to be mainly linked to fertilisation and driven by precipitation. Background fluxes were found to correlate positively with soil temperature. Secondly, a manipulation experiment took place in November 2012: two different fertilizer treatments were applied to the chambers. Doses of respectively 100 and 200 kg N/ha of ammonium nitrate were sprayed in the chambers (equivalent to a 8mmprecipitation). N2O fluxes peaked shortly after fertiliser application (respectively 300 and 550 ngN.m2s􀀀1), as well as after a posterior rain event (respectively 800 and 1500 ngN.m2s􀀀1). The peak dynamics suggests a complex interaction between soil humidity and nitrogen availability, which is under study. Dumortier et al., Geophysical Research Abstracts, Vol. 15, EGU2013-2083-1, 2013 Jérôme et al., Geophysical Research Abstracts Vol. 15, EGU2013-6989, 2013 [less ▲]

Relationships between soil properties and contents in trace elements in a landscape impacted by atmospheric fallouts in Belgium

Conference (2013, April 08)

Alimentation azotée des animaux de rente

Learning material (2013)

Amphiphilic structure-surface property relationships of monosaccharide-based surfactants

Poster (2013, April 08)

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar ... [more ▼]

A set of monosaccharide-based renewable surfactants has been prepared, structurally checked, and systematically screened for different activities and functionalities. These compounds vary in the polar head group, linker, and hydrophobic tail. Beyond the goal to find out the most potential valuable surfactants for each measurement, relationships between chemical structure, basic properties, and functionalities have been examined by comparing compounds differing in a single structural variable. In this paper, we show and explain the impact of the anomeric alpha or bêta, neutral or acid sugar derivatives, equatorial or axial position of hydroxyl group, alkyl chain substitute attachment position, number, and length on surface properties of sugar-based surfactants. [less ▲]

Modélisation du transfert radiatif en forêts feuillues ardennaises : adaptation de la librairie Samsaralight

Conference (2013, April 08)

The influence of biogeochemical processes on the pH dynamics in the seasonally hypoxic saline Lake Grevelingen

Poster (2013, April 07)

Carbon cycling in the epilimnion of Lake Kivu (East Africa): surface net autotrophy and emission of CO2 to the atmosphere sustained by geogenic inputs

Poster (2013, April 07)

Two year study of CO2, CH4 and N2O dynamics and fluxes in four rivers in Belgium (Meuse, Ourthe, Geer and Blanc Gravier)

Poster (2013, April 07)

Denitrification, anammox and fixed nitrogen removal in the water column of a tropical great lake

Conference (2013, April 07)

Branch-and-price: principles and its application to a 2-period vehicle routing problem

Scientific conference (2013, April 05)

We review branch-and-price as an efficient algorithm to solve integer programming problems with huge number of variables. In particular, we discuss column generation algorithm as the main engine in branch ... [more ▼]

We review branch-and-price as an efficient algorithm to solve integer programming problems with huge number of variables. In particular, we discuss column generation algorithm as the main engine in branch-and-price. Implementation of branch-and-price to solve the most basic version of the well-known vehicle routing problem (VRP) is investigated, and some common tricks are introduced. Then, a new extension of VRP is introduced and exploitation of branch-and-price to solve it is discussed. We consider a 2-period vehicle routing problem where each vertex of the network has a positive demand for period 1, 2, or both. Each demand on period 1 can be postponed to period 2 in order to decrease sum of the routing costs on two periods, but it is penalized in the objective function. Similarly, each demand on period 2 can be advanced to period 1, and yet penalized, with the hope of reducing routing costs. We have used many of the classic tricks to implement branch-and-price for solving our 2-period VRP. We have also used new tricks to (1) possibly improve the upper bound during the course of column generation in each node and (2) decrease the computations time to solve pricing problem in column generation. [less ▲]