Measurement and Modeling of Local Circulation Patterns and Pollutant Dispersion from a Waste Incinerator in the Basin of Bolzano in the Italian Alps.

Air quality scenarios can play a key role in supporting policies for monitoring pollutant dispersion and reducing health risks. However, the numerical modeling of pollutant dispersion is still a challenging task, especially in mountainous complex terrain. In fact, besides of the inherent difficulties in accurately reproducing both the atmospheric and the dispersion processes, the lack of experimental datasets of ground concentrations makes difficult the models calibration and validation.

In this contribution, results from the Bolzano Tracer Experiment (B-TEX), which was performed on 14 February 2017 near the city of Bolzano in the Eastern Italian Alps, are presented. The city lies in a basin, surrounded by high alpine crests, where four tributary valleys join. The experiment was part of a project aiming at the optimal design of a permanent air-quality-station network for monitoring long-term effect of pollutants emitted by the incinerator, as well as to outline possible scenarios of pollutant dispersion under accidental release. The experiment included two 1-h-long releases of a passive tracer from the stack of an incinerator plant located south to the city: one during the early morning, under stable meteorological conditions and weak Northerly winds, and the second in the early afternoon, under weak convection and a light Southerly wind. Also a very peculiar feature of the area was detected by wind profilers, i.e. a low-level valley-exit jet entering the basin through one of the tributary valleys outlet. Tracer concentrations were then measured at selected points in the surroundings. Before and during the releases a modelling chain was run coupling the Weather Research and Forecasting (WRF) model with two different dispersion models: the CALPUFF semi-lagrangian gaussian puff model and the SPRAYWEB particle lagrangian model. After the experiment a verification of the modeling chain was performed, including a sensitivity analysis to initial/boundary conditions as well as to parameterizations of boundary-layer and turbulent dispersion processes and model setup.

Results from the field campaigns, as well as from simulations performed under different model-chain design and setup, are presented and discussed.