Long-term trends and source apportionment of fine particulate matter (PM2.5) and gaseous pollutants in Auckland, New Zealand

Abstract

Airborne particles and pollutant gases are of increasing concern due to their adverse health effects, necessitating a thorough understanding of their composition, sources, spatial and temporal trends for effective air quality management. This study is part of a source apportionment study in Auckland, a dynamic urban environment with complex air quality challenges in an isolated Southern Ocean setting. Over the 2006–2016 period, concentrations of PM2.5, CO, NO2, and SO2 consistently decreased at all 4 monitoring sites indicating the impacts of control measures. The sources impacting the four sites were identified using the positive matrix factorisation (PMF) receptor model. Common sources affecting these sites included motor vehicles (both petrol and diesel), biomass burning, sea salt, sulphate/marine diesel, and soil/road dust. While motor vehicle emissions and biomass burning emerged as the primary contributors to PM2.5, BC, NO2, CO, and SO2, motor vehicle contributions declined due to advancements in fuel formulation and engine technology despite increased vehicle numbers. Biomass burning contributed substantially to winter PM2.5 concentrations driven by domestic heating practices. However, the introduction of alternative heating technologies mitigated the upward trends in biomass burning emissions despite an increasing residential population. Soil/road dust contributions varied by site, influenced by meteorological conditions and local activities, with implications for site-specific air quality management. Sulphate/marine diesel concentrations exhibited seasonal variability, reflecting the impact of both shipping emissions and natural sources. Urban sulphate concentrations decreased due to regulations requiring the introduction of low-sulphur automotive gasoline and diesel fuels. Sea salt, a naturally occurring source, posed challenges for management efforts with concentrations trending downwards over time, possibly linked to climate patterns. This study's source apportionment analysis provides critical insights into Auckland's air quality. The findings inform policy development, air quality management, and health impact assessments, benefiting both the Auckland region and New Zealand as a whole. Ongoing monitoring and emissions reduction strategies, particularly targeting motor vehicles and biomass burning, are pivotal for enhancing air quality and public health in the region.