Source and meteorological influences on air quality (CO, CH4 & CO2) at a Southern Hemisphere urban site

Abstract Wollongong, Australia is an urban site at the intersection of anthropogenic, biomass burning, biogenic and marine sources of atmospheric trace gases. The location offers a valuable opportunity to study drivers of atmospheric composition in the Southern Hemisphere. Here, a record of surface carbon monoxide (CO), methane (CH 4 ) and carbon dioxide (CO 2 ) was measured with an in situ Fourier transform infrared trace gasanalyser between April 2011 and August 2014. Clean air was found to arrive at Wollongong in approximately 10% of air masses. Biomass burning influence was evident in the average annual cycleof clean air CO during austral spring. A significant negative short-term trend was found in clean air CO (−1.5 nmol mol −1 a −1 ), driven by a reduction in northern Australian biomass burning. Significant short-term positive trends in clean air CH 4 (5.4 nmol mol −1 a −1 ) and CO 2 (1.9 μmol mol −1 a −1 ) were consistent with the long-term global average trends. Polluted Wollongong air was investigated using wind-direction/wind-speed clustering, which revealed major influence from local urban and industrial sources from the south. High values of CH 4 , with anthropogenic ΔCH 4 /ΔCO 2 enhancement ratio signatures, originated from the northwest, in the direction of local coal mining. A pollution climatology was developed for the region using back trajectory analysis and ΔO 3 /ΔCO enhancement ratios. Ozone production environments in austral spring and summer were associated with anticyclonicmeteorology on the east coast of Australia, while ozone depletionenvironments in autumn and winter were associated with continental transport, or fast moving trajectories from southern latitudes. This implies the need to consider meteorological conditions when developing policies for controlling air quality.