The paper describes the dataset of concentrations and related meteorological measurements collected during the field campaign of the Bolzano Tracer Experiment (BTEX).
The experiment was performed to characterize the dispersion of pollutants emitted from a waste incinerator in the basin of the city of Bolzano, in the Italian Alps.
As part of the experiment, two controlled releases of a passive gas tracer (sulfur hexafluoride,
The dataset represents one of the few examples available in the literature concerning dispersion processes in a typical mountain valley environment, and it provides a useful benchmark for testing atmospheric dispersion models in complex terrain.
The dataset described in this paper is available at
Pollutant transport modeling is an essential tool for our understanding of factors controlling air quality and consequently affecting the environment and human health.
Nowadays, increasing computational capabilities allow us to simulate with unprecedented detail many atmospheric processes even at local scale.
However, models still need careful calibration and validation against field observations, especially over complex mountainous terrain, where the interaction between local atmospheric processes and the orography
Several research projects focusing on air pollution transport processes at different scales have performed experiments including controlled releases of tracers, both at ground level
The main purpose of the above experiments is to provide a reliable reference benchmark under controlled conditions for comparison with dispersion model outputs.
However, only a few projects have been conducted over complex mountainous terrain
The present paper describes a dataset of tracer concentrations, and related meteorological measurements, collected to evaluate the pollutant dispersion from a waste incinerator close to Bolzano, a midsized city in the Italian Alps.
Indeed, concerns about the environmental impacts of this plant stimulated the organization of a comprehensive project to assess the fate of the pollutants released and their ground deposition in the surrounding area
The paper is organized as follows: Sect.
Overview of the study area. The map shows the orographic complexity of the region and the positions of the city of Bolzano (BZ), the incinerator (1) and the meteorological monitoring network used during BTEX, namely 1 sodar (2), 1 microwave temperature profiler (MTP; 3), 1 Doppler wind lidar (4) and 15 surface weather stations (WS).
The city of Bolzano (
The waste incinerator is
A passive tracer for monitoring the dispersion processes in the atmosphere needs to be (i) colorless and odorless, (ii) nontoxic to human health and the environment, (iii) chemically inert and stable at the temperature of the released smoke, (iv) absent in the ambient air (i.e., detectable only in trace concentration) and (v) easily measurable in the laboratory once environmental samples have been collected.
As none of the substances normally released in the atmosphere by the plant fulfill the above requirements, sulfur hexafluoride (
Nowadays,
Pollutant emissions from a plant into the atmosphere are strongly controlled by the operational working of the plant.
The emissions from the incinerator of Bolzano, under usual operating conditions, are ejected at a constant flow rate under steady conditions.
Therefore, the deposition areas of the pollutants and their ground concentrations mostly depend on local atmospheric processes, e.g., wind regime and stability.
Accordingly, in order to obtain realistic deposition patterns of the tracer, an important requirement was to perform a steady release of
Two releases of
Vacuum-filled glass bottle
During each release of
The meteorological field inside the Bolzano basin was simulated by means of the Weather Research and Forecasting (WRF) model
The modeling chain was used
48 h before the experiment to pinpoint a first-guess distribution of the samplers on the basis of the predicted meteorological conditions and fallout areas and right before each release, in nowcasting mode, to adjust (if needed) the distribution of the samplers with the updated model output (driven by the most recent assimilated meteorological measurements) and to define the starting time and duration of each sampling.
The resolution adopted for the numerical weather prediction simulations (i.e., 500 m) can fall, in principle, into the so-called gray zone or terra incognita, i.e., those scales where turbulence is neither subgrid nor fully resolved but rather is partially resolved. However, this rather high resolution was necessary to adequately capture the spatial variability of meteorological fields in the Bolzano basin. The CALMET model was used as a physically based interpolator to further increase the horizontal resolution from 500 to 200 m.
During BTEX, the meteorological field within the study area was monitored by means of 15 surface weather stations (WS in Fig.
Surface weather stations (WSs) adopted to monitor the meteorological field during BTEX along with their position (V: valley floor station; S: valley sidewall station), coordinates, altitude and available measurements: air temperature (
The 15 surface weather stations are part of the network operated by the Weather Service of the Autonomous Province of Bolzano and are partly located on the valley floors and partly on the sidewalls.
These stations, listed in Table
Technical characteristics of the microwave temperature profiler (MTP-5HE) installed at the airfield of Bolzano.
The atmospheric thermal structure inside the basin is constantly monitored by means of an MTP-5HE passive microwave radiometer (manufactured by ATTEX, Russia).
The instrument determines the vertical temperature profile at 11 elevation angles (from 0 to 90
The MTP-5HE used during BTEX (technical specifications in Table
A view of the roof of the incinerator of Bolzano during the experimental campaign with the MFAS mini-sodar
Wind intensity and direction at the outlet of a stack represent a fundamental input to properly model the fate of pollutants.
Accordingly, the wind field at the chimney of the incinerator was monitored by means of an MFAS mini-sodar (manufactured by Scintec, Germany), installed on the roof of the plant at
Sodar measurements played a key role in the BTEX project.
Indeed, during preliminary analyses preceding the experiment, these measurements allowed us to capture an intense nocturnal wind (wind intensity greater than
The interaction between the valley exit jet of the Isarco Valley and the smoke of the incinerator can strongly affect the pollutant dispersion scenarios within the Bolzano basin.
Therefore, a dedicated measurement campaign was performed to monitor this flow, and a Doppler wind lidar (label 4 in Fig.
The WINDCUBE 100S Doppler wind lidar from Leosphere (France) installed on a roof at
The Doppler wind lidar was a WINDCUBE 100S manufactured by Leosphere (France).
This device probes the atmosphere with coherent beams of pulsed, eye-safe electromagnetic waves in the near-infrared domain (wavelength
After each release, samples of ambient air were collected by means of two different technologies: vacuum-filled glass bottles and polyvinyl fluoride bags (hereafter PVF bags).
Bottles with a capacity of
Different from the online monitoring of
The dataset presented in this paper consists of
79 samples of time series of meteorological quantities collected by the monitoring network described in Sect. temperature profiles measured by means of the microwave temperature profiler (MTP-5HE) every sodar measurements, i.e., vertical profiles of mean wind quantities, standard deviations and backscatter, provided every Doppler wind lidar vertical profiles of the wind speed components and of the carrier-to-noise ratio, provided every information and working conditions of the incinerator observed during the day of the release, i.e., coordinates and height of the stack and discharge and temperature of the smoke every
CFS reanalyses of geopotential height at
Time evolution of the wind intensity
Time–height distribution of the thermal field
Releases of
During the night of 13 and 14 February, the moist air produced low-level clouds that covered the sky above the study area and inhibited the radiative cooling of the ground.
Indeed, as confirmed by the microwave temperature profiler (Fig.
The two releases of SF
Summary of the two releases performed during BTEX (VB: vacuum-filled glass bottles; TB: PVF bags).
Geographical coordinates of the sampling points (SP) along with number of samples of ambient air collected during the first release of BTEX (VB: vacuum-filled glass bottle; TB: PVF bags). The numbers after VB and TB indicate the duration in minutes of the sampling.
Geographical coordinates of the sampling points (SP) along with number of samples of ambient air collected during the second release of BTEX (VB: vacuum-filled glass bottle; TB: PVF bags). The numbers after VB and TB indicate the duration in minutes of the sampling.
Figure 8 provides a graphical overview of the dataset, by representing the time evolution of the concentrations measured by the sampling teams during each release (gray areas).
In particular, in view of describing the spatial patterns of the tracer along the axis of the Adige Valley, i.e., in agreement with the observed wind regime, the sampling points are ordered according to their latitude, i.e., from south (below) to north (above), while the horizontal black line marks the latitude of the incinerator.
Each box corresponds to one sample: the length of the box fits the timing and the duration of the sampling, whereas the color corresponds to the measured concentration.
Specifically, blue boxes correspond to samples in which the tracer concentration was lower than the detectability limit of the laboratory analyses, i.e.,
The first release of BTEX was carried out in the early morning, in order to evaluate the dispersion of pollutants in a stable nocturnal atmosphere with a light down-valley wind (i.e., blowing from north to south; see for example the weather station at Bronzolo (WS4) in Fig.
The second release started at 12:45 LST and ended at 14:15 LST, in order to investigate the dispersion processes under a weakly unstable atmosphere and an up-valley wind rising in the Adige Valley (see WS3, WS4, WS8 and WS11 in Fig.
At the end of this second release a total of 51 samples were collected by means of both vacuum-filled glass bottles and PVF bags.
Tracer concentrations measured on 14 February 2017 after each release.
Air samples were collected by means of vacuum-filled glass bottles (large rectangles) and PVF bags (small rectangles).
In addition, instantaneous samples of air (circles) were analyzed.
The sampling points are listed from north to south, while the two horizontal black lines indicate the latitude of the incinerator.
The arrows at the top and bottom of the graph indicate reference time stamps (LST) for Figs.
Spatial distribution of the tracer concentrations measured during the release performed in the morning of 14 February 2017. The position of the city of Bolzano is indicated on the map with the label BZ.
All data presented in this paper are publicly available at World Data Center PANGAEA
The Bolzano Tracer EXperiment (BTEX) represents one of the few experiments available in the literature performed over complex mountainous terrain to evaluate dispersion processes by means of controlled tracer releases and under well-documented meteorological conditions.
The obtained dataset presented in this paper is the result of a 3-year project during which a great effort was made to properly design, organize and manage all the activities connected to the measurement campaigns.
Indeed, preliminary investigations and also ad hoc measurement campaigns were performed to identify the most suitable monitoring network (Sect.
Spatial distribution of the tracer concentrations measured during the release performed in the afternoon of 14 February 2017. The position of the city of Bolzano is indicated in the map with the label BZ.
On 14 February 2017 two tracer releases were performed.
The collected dataset contains 79 samples of tracer ground concentrations, collected during each release in 14 different locations of the study area and at different times.
The complex orography of the study area and its related heterogeneous meteorological fields did not allow for a regular distribution of the sampling points around the incinerator, e.g., in concentric circles.
Therefore, seven sampling points were located in the main residential areas neighboring the incinerator, while the other seven sampling points were placed in agreement with the fallout areas of the tracer, as predicted by a modeling chain specifically set up for the purposes of the study and composed of both meteorological and dispersion models.
In particular, for a proper interpretation of the output of the modeling chain, a key role was played by the expertise gained by the modeling team on the typical meteorological processes characterizing the study area.
The adopted strategy allowed us to capture the space–time variability of the tracer at ground level.
More details on the numerical experiments carried out to simulate the tracer dispersion can be found in
The dataset is completed with a detailed description of the meteorological field, provided by 15 surface weather stations, 1 microwave temperature profiler, 1 sodar and 1 Doppler wind lidar. Specifically, the meteorological data cover a period of 48 h starting from 13 February 2017 00:00 LST in order to provide a more complete description of the meteorological processes within the study area.
The uniqueness of BTEX makes the collected dataset a useful benchmark for testing dispersion models in complex terrain.
MF led the writing of the paper and prepared all figures and tables. WT wrote the section on chemical measurements. DZ revised preliminary versions of the manuscript. All authors contributed to suggesting ideas and reviewing the paper. All authors contributed to the design and planning of the experiment and participated in the field campaigns. WT provided the required tools for air samples collection, instructed the team of observers and performed all the laboratory analyses. MF, LG, ET and GA managed the sodar and the Doppler wind lidar operations. GA, ET and LG contributed to the setup of the modeling chain and operated it during the field campaigns. MF collected all the data, both from the field experiment and from permanent observational facilities in the target area and surroundings; organized the dataset; and created its publication on World Data Center PANGAEA. DZ, as principal investigator, managed the overall execution of the project, including partners' involvement and commitment, from the initial concept to the conclusion, and suggested the preparation of the present paper.
The authors declare that they have no conflict of interest.
The authors acknowledge Marco Palmitano (eco center S.p.A) and Bruno Eisenstecken (eco center S.p.A), who encouraged and strongly supported this study, also by renting the Doppler wind lidar. The authors are also grateful to all the personnel of eco center S.p.A., Eco-Research s.r.l., the Environmental Agency of the Autonomous Province of Bolzano and the Mario Negri Institute for Pharmacological Research for participating in the measurement activities during the releases. The Weather Service of the Autonomous Province of Bolzano is acknowledged for kindly providing data from its weather stations. The Environmental Agency of the Autonomous Province of Bolzano, Massimo Guariento and Luca Verdi are kindly acknowledged for data from the microwave temperature profiler.
This paper was edited by Scott Stevens and reviewed by two anonymous referees.