Executive summary

Airborne particulate matter (PM) and gaseous pollutants pose significant health risks and comprehensive studies on their composition, sources, and trends are needed for effective air quality management. This study investigates the source apportionment of coarse particulate matter (PM₁₀) and its long-term trends in Auckland. Over the 2006-2022 study period, consistent decreases in PM₁₀ concentrations were recorded across the monitored sites, attributed primarily to reductions in motor vehicle emissions facilitated by advancements in fuel formulation and emission control technology. 

Five common sources affecting the three PM₁₀ monitoring sites were resolved using positive matrix factorisation (PMF) receptor modelling. These sources were identified as marine aerosol, motor vehicles, biomass burning, sulphate (primary and secondary), and soil. Marine aerosol contributes substantially to Auckland’s PM₁₀ levels, accounting for over 44 per cent of the mass concentration on average. However, being a natural source, marine aerosol is part of the ‘natural’ background of Auckland and therefore, a challenge to manage. Marine aerosol contributions showed downward trends over the study period, possibly influenced by changing climate patterns.

Motor vehicles and biomass burning remain the primary anthropogenic sources of PM₁₀ in Auckland. Biomass burning, particularly during winter months, was a significant contributor to PM₁₀ concentrations although the use of alternative heating technologies helped stabilise concentrations at two of the three monitored sites. Shipping emissions were identified as having a direct impact on urban air quality with regulations mandating low-sulphur fuels contributing to decreased sulphate source contributions to PM₁₀. 

This study underscores the importance of ongoing monitoring and emissions reduction strategies, particularly targeting motor vehicles and biomass burning, for enhancing air quality and public health. This research contributes to a broader understanding of PM dynamics in Auckland, informing policy development and air quality management strategies.

Auckland Council technical report, TR2025/2

February 2025