Since the mid-90s, the European Community has
adopted increasingly stringent air quality standards.
Consequently, air quality has generally improved across
Europe. However, current EU standards are still breached
in some European hotspots.
The Veneto region (NE Italy) lies in the eastern
part of the Po Valley, a major European hotspot for air
pollution, where EU standards for particulate matter,
nitrogen oxides and ozone are still breached at some
sites.
This study aims to analyse the PM10-bound
arsenic, cadmium, nickel, and lead concentrations over a
10 years-long period (2010-2020) in the Veneto Region
by using data collected by the local environmental
protection agency (ARPAV) in 20 sampling stations
mostly distributed across the plain areas of the region
and categorized as rural (RUR), urban (URB), and
suburban (SUB) background, industrial (IND) and traffic
(TRA) hotspots (Figure 1). The comprehensive dataset
discussed in this study was statistically investigated to
detect the seasonal trends, their relationship with other
air pollutants and meteorological parameters and their
spatial variations at a regional scale. This study
completes previous air quality studies over the Veneto
region for gaseous pollutants and bulk PM10 (Masiol et al.
2017).
Samplings were carried out according to CEN EN
12341:1998 standard on quartz fibre filters and were
continuous for 24 h, starting at midnight. The gravimetric
determination of PM10 mass was measured following
the CEN EN 12341:2014 standard. The elemental analysis
was performed using an ICP-MS (Agilent 7700) after acid
digestion (EN 14902:2005).
The trends were analysed using different
approaches on the monthly-averaged data. The shape of
trends and their seasonal variations were assessed
through the seasonal-trend decomposition time series
procedure based on “Loess” (STL). The linear trends were
computed by the Mann-Kendall trend test (p < 0.05) and
the Theil-Sen nonparametric estimator of slope (MK-TS).
Since this latter analysis assumes monotonic linear
trends and does not consider the shape of trends, the
presence of possible breakpoints was investigated using
the piecewise regression.
Generally, monthly patterns of all analysed
elements show higher concentrations during winter,
following PM10 concentrations. Some exceptions were
detected and discussed. Results of trend analysis indicate
statistically significant negative (decreasing) or null linear
trends in almost all stations. A few positive (increasing)
but not statistically significant trends were also detected.
Some sites showed rapid decreases occurred in
short periods and linked to peculiar events or local
causes. Among others, several sites across the Venice
area showed significant drops of arsenic concentrations
after the REACH (Registration Evaluation Authorisation
of Chemicals) implementation (Formenton et al., 2021).
Data used in this study are provided by ARPAV (Agenzia
Regionale per la Prevenzione e Protezione Ambientale
del Veneto, https://www.arpa.veneto.it/)