Spatio-temporal analysis of air pollution data in Malta

Abstract

Air pollution measurements display patterns over space and time allowing for spatio-temporal modelling, through which pollution concentrations and trends can be analysed. In Malta, the MEPA (Malta Environment and Planning Authority) collects monthly averaged data for various pollutants from a network of 123 diffusion tubes located around the Islands (Figure 1). This preliminary study uses data associated with traffic, that is nitrogen dioxide (NO2) and benzene, collected monthly between the period 2004 and 2010 with the objectives to i) develop a computationally efficient method that best describes the data; ii) determine the level of dependency of each site on neighbouring ones and iii) identify any factors that affect the behaviour and patterns of pollution. Results will show that generally there is a low spatial dependency between close sites, thus implying that local sources, rather than diffusion, have a predominant effect on the measurements. This analysis will prove valuable in MEPA’s redistribution exercise of the diffusion tube network to determine which sites are necessary to retain and which sites can be removed without significantly affecting the information gathered.