Spatial and temporal air quality analysis of the Maltese Islands, in relation to the COVID-19 partial lockdown

Abstract

The influence of the COVID-19 pandemic has been widespread across various sectors of society, including the environment. Due to the recency of the outbreak, scientific literature concerning air quality in Malta is still scarce. This study looks towards the influence of the pandemic and the imposed partial lockdown on nitrogen dioxide (NO2) and benzene concentrations across Malta and Gozo. To observe and better understand these changes, NO2 and benzene concentrations taken from 2014 till 2020, measured by the passive diffusion tube network in Malta and Gozo, was utilised in this study. This data was analysed on both a spatial and temporal level. To conduct the spatial analysis, 28 different choropleth maps were produced, 14 maps displaying NO2 concentrations and the 14 other maps representing benzene concentrations. For the temporal analysis, box plots were produced for each year from 2014 till 2019. In total, 12 different plots were produced using the values recorded during the 13 exposure periods in each year. Similarly, box plots were produced for the ten traffic sites that recorded the highest concentrations of NO2 and benzene respectively. The analysis highlighted the reductions in pollutant concentrations experienced during the partial lockdown. Traffic sites at St. Geroge’s Road (STJ 1) and Corradino Road (PLA 8) measured a 75% decrease in NO2 concentrations when compared to the same period in 2019. Benzene reductions were less drastic. However, certain sites still experienced reductions of up to 50% to the same period in 2019. Results from the Mann-Whitney U statistical test further emphasised the role of the partial lockdown on the reduced concentrations. It was determined that there was no significant difference between the median recordings of the concentration averages computed before and after the March-June period and concentration averages measured during the March-June period.