Decreasing Trend in Formaldehyde Detected From 20‐Year Record at Wollongong, Southeast Australia

Abstract

The response of atmospheric composition to ongoing environmental change remains poorly constrained across much of the Southern Hemisphere. We use a 20‐year record of ground‐based total column measurements from Wollongong, southeast Australia to identify a statistically significant decreasing trend in formaldehyde of −1.9 [−2.2, −1.7]%/year. The trend is consistently negative across all months except November. Satellite data indicate that the trend at Wollongong is distinctly local and is superimposed on a regional‐scale increase likely driven by changes in methane. In austral summer, coincident changes in hydrogen cyanide suggest that decreases in local biomass burning can only partly explain the observed trend. In the absence of other explanations, we infer that the observed formaldehyde trend is likely driven by decreasing industrial emissions. In November, an observed increasing temperature trend is consistent with an earlier onset of biogenic emissions in the region, driving increased biogenic formaldehyde that counteracts the overall decrease.

Spatio-temporal distribution and source partitioning of formaldehyde over Ethiopia and Kenya

“…Methane (CH 4 ) has been shown to affect HCHO on both global and local scales via oxidation by OH (Pfister et al, 2008;Lieschke et al, 2019). In this study, CH Vegetation is another important local HCHO source, which emits BVOCs and affect HCHO indirectly.…”

“…Formaldehyde (HCHO) is a high-yield product of volatile organic compounds (VOCs), including biogenic and anthropogenic VOCs. According to model estimates, approximately 30% of the global HCHO burden comes from isoprene (Stavrakou et al, 2009), one of the most abundant reactive compounds of biogenic volatile organic compounds (BVOCs) emitted from different ecosystems (Guenther et al, 2006;Lieschke et al, 2019). As both isoprene and HCHO have very short atmospheric lifetime, normally few hours, HCHO is widely used to estimate the concentration of isoprene, particularly for regions that have few observations from field measurements (Marais et al, 2012;Zhu et al, 2017).…”

“…HCHO is elevated mainly by methane (CH 4 ) oxidation; BVOC degradation, biomass burning; and anthropogenic sources (Luecken et al, 2012). Methane oxidation by hydroxyl radical (OH) is the main source of global HCHO background value and variation (De Smedt et al, 2015;Franco et al, 2016), which contributes from 45% to 60% of the global total atmospheric HCHO (Lieschke et al, 2019). Equations 1-a to c show a simple example of HCHO formation from methane.…”

Australian Fire Emissions of Carbon Monoxide Estimated by Global Biomass Burning Inventories: Variability and Observational Constraints

“…Meanwhile, Wollongong is a semi-urban site located on the east coast of New South Wales roughly 100 km south of Sydney. The site does occasionally sample smoke from local fires (e.g., Rea et al, 2016) but is also sensitive to anthropogenic, biogenic, and long-range transported biomass burning sources (Buchholz et al, 2016;Fisher et al, 2017;Lieschke et al, 2019). The mean biases of each simulation relative to the Cape Grim and Wollongong measurements and the MOPITT satellite data (averaged over southern Australia) are shown in Table 5.…”

“…Meanwhile, Wollongong is a semi‐urban site located on the east coast of New South Wales roughly 100 km south of Sydney. The site does occasionally sample smoke from local fires (e.g., Rea et al., 2016) but is also sensitive to anthropogenic, biogenic, and long‐range transported biomass burning sources (Buchholz et al., 2016; Fisher et al., 2017; Lieschke et al., 2019).…”