Lucas Garcia PhD thesis defense (INRA Grignon)

I am pleased
to invite you to my PhD thesis defense, which will take place on the 27th
of May 2010, at the Pierre et Marie Curie
university in Paris (France),
and to the subsequent drink.

I will
present the results of my PhD work, entitled “Ammonia and pesticides
volatilization from agricultural fields. Analysis and modeling of the influence
of the surface physical properties and conditions with the Volt'Air model”, for
which you should find the abstract below.

The defense
will take place on Thursday, May 27th 2010 at 2 p.m. (14h)

at the Université Pierre et Marie Curie campus

4 place Jussieu

75005 Paris, France

At the
Herpin amphitheater, Esclangon building.

Before the
following jury:

Mr. CHANZY
André, Senior scientist, INRA Avignon, France - Reviewer

Mr.
ROCHETTE Philippe, Senior scientist, AAC, Canada - Reviewer

Mr. CABANE
Michel, Professor of the UPMC, LATMOS, France - Examiner

Mr. FERRARI
Federico, Scientist, Inst. Of Agr. and Env. Chemistry, Italy - Examiner

Mr. WEILL
Alain, Senior scientist, LATMOS, France -
Examiner

Mr. CELLIER
Pierre, Senior scientist, INRA Grignon,
France - PhD Director

Ms. BEDOS
Carole, Scientist, INRA Grignon,
France - PhD Supervisor

Ms.
GENERMONT Sophie, Scientist, INRA Grignon,
France - PhD Supervisor

 Lucas Garcia

Abstract

Ammonia and
pesticides emissions to the atmosphere mainly originate from agricultural
activities. Such compounds released in the air imply a number of health risks
to human populations, either from intense but short exposition or low
concentrations on a longer period. Likewise, deposition on non-target ecosystem
can intensely disturb the environment (eutrophication, acidification…) and its
inhabiting species (destruction or weakening of the biotope food chain).

Volatilization
of ammonia and pesticides occurs right at the moment of the input on the farmed
surface and lasts from a few days to a few weeks, depending on the properties
of the considered compound and the pedoclimatic conditions. An important
component of the establishment of the volatilization flux is the availability
of the compound in gaseous form at the soil surface, at the interface with the
atmosphere. This availability is governed by the compound transfers from and to
this surface and its physic-chemical equilibriums, which themselves depend on
the soil surface temperature and humidity conditions and the water transfers.

We used and
improved the ammonia and pesticides volatilization model Volt'Air in order to refine
the representation of the surface and its influence, both from its nature and its
physical conditions,  on the processes
defining volatilization. After assessing the ability of Volt'Air to describe
the physical conditions of a bare soil at adequate space and time scales, we
implemented the modeling concept of a layer of manure at the surface,
integrating a specific description of the water, heat and compound transfers,
along with the definition of the layer hydraulic properties. Moreover, modeling
of the input heterogeneity proves the ability of Volt'Air to adequately
reproduce and assess some of the currently used emissions reduction techniques.
Finally, accounting for the surface physical conditions allowed for developing
a new equilibrium formalism, with the integration of the adsorption of
pesticides in gaseous form on mineral matrixes depending on the temperature and
humidity of the soil, inspired by the latest studies on organic compound
adsorption.. Comparison with experimental measurements showed that each of
these implementations notably improved the estimation of the volatilization
fluxes relatively to the previous version of Volt'Air, either when comparing to
a cattle slurry application for the manure layer implementation, or a
trifluralin application on a bare soil for the gaseous adsorption
implementation.

Key Words : volatilization, ammonia, pesticides, surface
conditions, manure, adsorption