We carried out ambient sampling of particulate matter influenced by domestic biomass burning (BB) in urban settings (Athens and Patras, Greece; e.g.
https://twitter.com/pyrotrach/status/1260532378503692288(opens in new window)) the remote site of Finokalia and Heraklion, Crete (e.g.
https://twitter.com/LAPI_epfl/status/1278377339936702464(opens in new window)) and Mt.Helmos in the Peloponnese, to capture wildfire plumes from a range of distances and degree of chemical processing.
We systematically carryied out laboratory experiments, where smoke is generated from a variety of facilities and combustion conditions (wood stove, fireplace, pellet stove) and introduced into the FORTH environmental chamber facility (e.g.
https://twitter.com/LAPI_epfl/status/1252800291424088064(opens in new window)) that replicates the conditions found in the atmosphere. In this facility, the smoke samples are “aged” in the chamber, as they would in the atmosphere under specific “regimes”– the main ones being nighttime vs. daytime conditions and humid vs. dry). Over time during these aging experiments, we follow how the chemistry and properties of the smoke particles change.
We also carried out campaign intensives (e.g.
https://twitter.com/LAPI_epfl/status/1156596691941941254(opens in new window) https://twitter.com/pyrotrach/status/1271231836656668672 ) where airmasses influenced by BB smoke are characterized and further aged – under controlled conditions – with portable environmental chambers deployed in the field - to follow the properties of BB smoke when it is further aged, and thus provides breakthrough understanding of the most aged particles from BB.
All BB samples were analyzed for the chemical markers and characteristics related to their ability to absorb light (“brown carbon”) as well as their ability to generate radicals in-vivo (“oxidative potential”) and provide other sources of toxicity (polyaromatic hydrocarbons and their oxidized counterparts) that are associated with adverse health impacts upon inhalation. We show that BB is highly toxic, associated with high levels of oxidative potential and carcinogen content. The ability to cause oxidative stress in people increases as smoke ages in the atmosphere. However, the timing of emissions and subsequent oxidation (e.g. nighttime vs. daytime) give much different transient levels of OP, meaning that health impacts of smoke depends strongly on when it is emittied and how it is subsequently aged before it is inhaled by people. Its transient toxicity can vary significantly, with oxidized smoke being generally more toxic than the original emissions. This means that even if it is highly diluted - can still cause adverse impacts to populations when breathing it over time. Domestic BB is a major contributor to the total oxidative potential of aerosol in wintertime and while wildfire smoke in the summertime.
BB is a very significant source of carcinogens (polyaromatic hydrocarbons; PAHs) which can persist if the relative humidity conditions are such (low humidity). In urban environments such as Athens, Greece, a significant fraction of the annual exposure of the population is related to wintertive haze episodes rich in BB smoke, the effects on heal of which is further exacerbated by the high levels of particulate matter and its strong contribution to oxidative potential and stress. We find that BB in general induces strong impacts adverse on health through multiple pathways.
Through modeling, we show that BB emits considerable amounts of Brown Carbon, a climate warmer, which mostly decays ("photobleaches") a few hours after emission. A fraction however, composed of very large molecules emitted directly from biomass burning, is quite resilient to oxidation and remains brown after a few days of aging. This resilient brown carbon is uniquely related to BB, causes persistent climate warming and can be used as a marker for aged BB.
BB is is an important modulator of atmospheric acidity, and we have developed a unique framework for understanding how acidity and liquid water content levels can impact the sensitivivty of particulate matter levels to precursor compounds and also the speed which aerosol deposits on the ground, thus unraveling when particulate matter tends to accumulate in the boundary layer, and the characteristic regimes of nutrient deposition velocity and its impacts on ecosystem productivity.
Biomass burning and its estimated impacts on health can change (compared to other aerosol types) if one switches from a mass-based link to health to one based on OP. This was particularly evident during a study in Athens, and the relative toxicity of aerosol from BB vs. Saharan dust.
