High Hydroquinone Emissions from Burning Manzanita

California wildfires are becoming larger and more frequent because of climate change and historical fire suppression. The 2017 fire season was record-breaking in terms of monetary damage, area burned, and human casualties. In addition, roughly 20 million people were exposed to dense wildfire smoke for days. Understanding the health impacts of wildfire smoke requires detailed chemical speciation of smoke produced from different fuels. This study demonstrates the unique chemical fingerprint observed in smoke from burning manzanita, a common chaparral and forest understory shrub found in several ecosystems of California. Burning manzanita during the FIREX Fire Laboratory experiments emitted hydroquinone (1,4-dihydroxybenzene with an emission factor of 0.4 g/kg) and two sterol/triterpenoid tracer compounds at levels up to 100 times higher than those of the other common wildland fuels in California such as pine trees, other shrubs, grasses, and duff. Additionally, these compounds were detected in Berkeley, CA, from smoke produced during the October 2017 wildfires in northern California, a region where manzanita grows. In contrast, the identified fingerprint for manzanita burning emissions was not observed during prescribed fires of a mixed conifer forest in California's Sierra Nevada, indicating negligible amounts of manzanita were burned. As confirmed by shrub inventory data collected prior to the burns, small amounts of manzanita remain after prescribed burning, a low-severity forest management technique, but larger amounts can occur after recovery from high-severity events like wildfires. Results from this study show that chemical signatures in smoke can be traced back to specific fuels like manzanita and that forest management techniques can be used to limit certain types of wildfire emissions.