Environmental Engineering Reference
In-Depth Information
4.7 An Application of Lagrangian Particle Model
with Chemical Reactions to Power Plant Pollution
Dispersion in Complex
Stefano Alessandrini
1
and Enrico Ferrero
2
1
ERSE (Enea Ricerca Settore Elettrico), via Rubattino 54, Milano
2
Università del Piemonte Orientale, via Teresa Michel, 11, Alessandria, Italy
1. Introduction
A modeling system based on the regional atmospheric model RAMS (Pielke et al.,
1992) and the Lagrangian particle model SPRAY (Tinarelli et al., 2000) is adopted
to forecast the concentration of pollutants around the CERCS power plant, situated
in a complex terrain area of Spain. To calculate also the NO
2
concentration, we
introduced in the Lagrangian dispersion model an hybrid Lagrangian-Eulerian
scheme for chemical reactions between nitrogen oxides an ozone including the
NO
2
photolysis. This new model was tested in controlled conditions in a previous
work (Alessandrini and Ferrero, 2009). It is worth noticing that the small distance
of the air quality stations from the power plant stacks gives the possibility to study
also the cases where the plume has not still reached the photochemical equilibrium
condition. In these situations the photochemical algorithm used shows considerably
important advantages compared to more simple approaches generally adopted.
The results of the simulations carried out using the modeling system are presented
analyzing some particularly interesting episodes. The comparison between the
predicted and measured concentrations of all the emitted substances shows the
ability of the chemical scheme to account for the short term turbulent dispersion.
2. The Chemical Model
Following Chock and Winkler (1994a, b) chemistry and dispersion are treated
separately and sequentially, each particle (n) released by the source may bring
mass of different substances. At each time step the particle position X
(n)
(t) is
updated using the stochastic model equation, then the concentrations of each
substance is calculated in a fixed Eulerian grid and the chemistry is updated.
Formation of NO
2
occurs when NO is emitted in an atmosphere containing O
3
.
During the daytime, photo-dissociation of NO
2
by absorption of ultra-violet
