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Numerical modelling. Determination of the origin of episodes

The knowledge of the origin of odorous episodes in multiple-source areas is a key factor to take into account to enhance air quality. In this line, LCMA has developed several methodologies focused in solving the absence of these data. Two main methodologies are applied depending on the control situation:


a) Analysis of the episode register historical data

b) Analysis of current episode register data together with chemical control (activation of the samplers by the affected people)


As has been said before, a first approach of episodes origin determination can be achieved through episode roses, trajectory intersection, etc. However, LCMA has developed a second level of confirmation of the results through the calculation of back-trajectories and the simultaneous chemical control during the sampling duration.


The determination of the origin of an odorous episode based on back-trajectory calculation from different simultaneous detection points is shown in figure 13.


The discernment of the origin of an odour episode in an area with several potential emission sources is shown in figure 14.


The evolution in time of the odour intensity of an episode is shown in figure 15. Odour intensity decreases as the back-trajectory of the air mass increases its distance from the emitter activity.


Figure 13. Back-trajectories from different detection points of the same odour


Figure 14. Back-trajectory of an odorous episode in an area with multiple emission


Figure 15. Evolution of the origin of an odorous episode at different odour intensities
(Odour scale: No odour (1)-Maximum odour intensity (5))