Biomass Fires Research Articles

Ambient biomass smoke and cardio-respiratory hospital admissions in Darwin, Australia.

BackgroundIncreasing severe vegetation fires worldwide has been attributed to both global environmental change and land management practices. However there is little evidence concerning the population health effects of outdoor air pollution derived from biomass fires. Frequent seasonal bushfires near Darwin, Australia provide an opportunity to examine this issue. We examined the relationship between atmospheric particle loadings <10 microns in diameter (PM10), and emergency hospital admissions for cardio-respiratory conditions over the three fire seasons of 2000, 2004 and 2005. In addition we examined the differential impacts on Indigenous Australians, a high risk population subgroup.MethodsWe conducted a case-crossover analysis of emergency hospital admissions with principal ICD10 diagnosis codes J00–J99 and I00–I99. Conditional logistic regression models were used to calculate odds ratios for admission with 10 μg/m3 rises in PM10. These were adjusted for weekly influenza rates, same day mean temperature and humidity, the mean temperature and humidity of the previous three days, days with rainfall > 5 mm, public holidays and holiday periods.ResultsPM10 ranged from 6.4 – 70.0 μg/m3 (mean 19.1). 2466 admissions were examined of which 23% were for Indigenous people. There was a positive relationship between PM10 and admissions for all respiratory conditions (OR 1.08 95%CI 0.98–1.18) with a larger magnitude in the Indigenous subpopulation (OR1.17 95% CI 0.98–1.40). While there was no relationship between PM10 and cardiovascular admissions overall, there was a positive association with ischaemic heart disease in Indigenous people, greatest at a lag of 3 days (OR 1.71 95%CI 1.14–2.55).ConclusionPM10 derived from vegetation fires was predominantly associated with respiratory rather than cardiovascular admissions. This outcome is consistent with the few available studies of ambient biomass smoke pollution. Indigenous people appear to be at higher risk of cardio-respiratory hospital admissions associated with exposure to PM10.

Satellite boreal measurements over Alaska and Canada during June–July 2004: Simultaneous measurements of upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, OCS, and SF6 mixing ratios

Simultaneous ACE (Atmospheric Chemistry Experiment) upper tropospheric CO, C2H6, HCN, CH3Cl, CH4, C2H2, CH3OH, HCOOH, and OCS measurements show plumes up to 185 ppbv (10−9 per unit volume) for CO, 1.36 ppbv for C2H6, 755 pptv (10−12 per unit volume) for HCN, 1.12 ppbv for CH3Cl, 1.82 ppmv (10−6 per unit volume) for CH4, 0.178 ppbv for C2H2, 3.89 ppbv for CH3OH, 0.843 ppbv for HCOOH, and 0.48 ppbv for OCS in western Canada and Alaska at 50°N–68°N latitude between 29 June and 23 July 2004. Enhancement ratios and emission factors for HCOOH, CH3OH, HCN, C2H6, and OCS relative to CO at 250–350 hPa are inferred from measurements of young plumes compared with lower mixing ratios assumed to represent background conditions based on a CO emission factor derived from boreal measurements. Results are generally consistent with the limited data reported for various vegetative types and emission phases measured in extratropical forests including boreal forests. The low correlation between fire product emission mixing ratios and the SF6 mixing ratio is consistent with no significant SF6 emissions from the biomass fires.

Horse grazing in firebreaks sown with Trifolium brachycalycinum (Katznl. &amp; Morley) and Cynodon dactylon (L.) Pers

Firebreaks are useful to reduce the extent of forest fires, however, when they are cleared down the slope, soil erosion is increased and the native tall sward in summer can increase fire risk. The sown mixture Trifolium brachycalycinum (Katznl. & Morley) and Cynodon dactylon L. Pers. has already proved to be useful for both fire prevention (the short sward remains green in summer, creating easy access) and biomass production (clover can give high yields with high palatability and protein levels). This pasture needs to be grazed to be kept short and reduce fuel biomass in summer. Unfortunately, there is not much livestock reared in Central Italy and animals are normally fed indoors. In this article, a trial in a coastal farm of Central Italy is reported to investigate the efficiency of horses in maintaining the sown species botanical composition, soil cover, sward height, biomass (before and after grazing) and fuel biomass in summer in a firebreak over 4 years. The mixture was intensively grazed over short periods during spring and summer. Animals grazed both the sown species and native plants, they trampled on the remaining herbage, breaking the stems, and leaving short and compact dry mulch. Very little combustible vegetation was left in the hot season and horse grazing is recommended for farms that have firebreaks.

Hygroscopic behavior of aerosol particles from biomass fires using environmental transmission electron microscopy

We used both a conventional transmission electron microscope and an environ- mental transmission electron microscope (ETEM) to determine morphology, composition, and water uptake of 80 individual aerosol particles collected from the young smoke of flaming and smoldering fires during SAFARI-2000, a comprehensive air quality campaign in southern Africa. Six representative carbonaceous particle types are described, including soot, tar balls, and heterogeneously internally mixed particles containing C with S-, K-, Mg- or Na- rich inorganic phases. The hygroscopic behavior of these particles over the range 0-100% relative humidity (RH) was studied in detail. Soot and tar balls did not take up water, whereas the mixed organic-inorganic particles took up water between 55 and 100% RH, the exact value depending on the composition of their water-soluble phases. The inorganic phase appeared to determine the hygroscopic properties of all mixed organic-inorganic particles. Thus, incorporation of inorganic plant material or reactions with inorganic atmospheric components can dramatically alter the hygroscopic properties of carbonaceous particles in smoke plumes. The fraction of these mixed organic-inorganic particles plausibly increases with time, which will modulate the effects of smoke on radiative budgets.

Estimates of global biomass burning emissions for reactive greenhouse gases (CO, NMHCs, and NOx) and CO2

Open fire biomass burning and domestic biofuel burning (e.g., cooking, heating, and charcoal making) algorithms have been incorporated into a terrestrial ecosystem model to estimate CO2and key reactive GHGs (CO, NOx, and NMHCs) emissions for the year 2000. The emissions are calculated over the globe at a 0.5° × 0.5° spatial resolution using tree density imagery, and two separate sets of data each for global area burned and land clearing for croplands, along with biofuel consumption rate data. The estimated global and annual total dry matter (DM) burned due to open fire biomass burning ranges between 5221 and 7346 Tg DM/yr, whereas the resultant emissions ranges are 6564–9093 Tg CO2/yr, 438–568 Tg CO/yr, 11–16 Tg NOx/yr (as NO), and 29–40 Tg NMHCs/yr. The results indicate that land use changes for cropland is one of the major sources of biomass burning, which amounts to 25–27% (CO2), 25 –28% (CO), 20–23% (NO), and 28–30% (NMHCs) of the total open fire biomass burning emissions of these gases. Estimated DM burned associated with domestic biofuel burning is 3,114 Tg DM/yr, and resultant emissions are 4825 Tg CO2/yr, 243 Tg CO/yr, 3 Tg NOx/yr, and 23 Tg NMHCs/yr. Total emissions from biomass burning are highest in tropical regions (Asia, America, and Africa), where we identify important contributions from primary forest cutting for croplands and domestic biofuel burning.

THE EFFECTIVENESS OF A BEHAVIOURAL INTERVENTION TO REDUCE CHILD EXPOSURE TO INDOOR AIR POLLUTION: PRELIMINARY RESULTS

ISEE-164 Introduction: Indoor air pollution has been causally linked to Acute Lower Respiratory Infections in children younger than five years old and accounts for a significant proportion of death and illness in developing countries. At the level of prevention, behaviour change has been identified as a possible intervention strategy to reduce the impact of indoor air pollution on child respiratory health. Nevertheless, published studies have yet to systematically evaluate the effectiveness of behaviour change strategies in reducing child exposure to indoor air pollution. Aim: The aim of this study was to evaluate the effectiveness of a behavioural intervention designed to reduce child exposure to indoor air pollution. Methods: Using a before-after (with comparison group) study design, the project evaluated the effectiveness of the intervention in a rural, village in the North West province of South Africa. Results were compared to a similar community that did not receive the intervention. All households that had a child younger than four years old were recruited into the study. Overall, 324 households (175 in the intervention and 149 in the comparison group) including 502 children (244 in the intervention and 258 in the comparison group) participated in the study. The study focused on socio-demographic information, indoor air quality concentrations (respirable particulates and carbon monoxide), child exposure to indoor air pollution, health literacy related to indoor air pollution, and child respiratory health. Baseline data were captured during early winter 2003 (before the intervention) and follow-up data 12 months later, during winter 2004. Results: In terms of health literacy, preliminary results showed no significant impacts on caregivers’ knowledge of indoor air pollution. However, significant improvements were found in caregivers’ perceptions of their children’s susceptibility to indoor air pollution. In terms of indoor air quality, results showed no significant impacts on overall kitchen concentrations of respirable particulates and carbon monoxide. However, child exposure to carbon monoxide was significantly reduced in the intervention community compared to the comparison community. Reductions in child exposure may be related to a significant decrease in the amounts of time that children in the intervention group spent in the vicinity of indoor biomass fires compared to the comparison group. Multivariate analyses are currently underway to determine the interactions of these factors on respiratory health. Conclusion: Preliminary results suggest that behavioural interventions may be more effective in certain domains than others. Even though the intervention (alone) did not affect ambient levels of indoor air quality, it is positive to note reductions in child exposure to indoor air pollution (possibly through reductions in the amounts of time that children spent close to fires). These and other findings will be discussed in relation to other intervention approaches and evaluation methodologies.

Long‐range transport of Siberian biomass burning emissions and impact on surface ozone in western North America

During the summer of 2003, biomass fires burned a large area of Siberia, the largest in at least 10 years. We used the NRL Aerosol Analysis and Prediction System (NAAPS) model to forecast the transport of the smoke from these fires. Transport of these airmasses to North America was confirmed by aircraft and surface observations. The fires resulted in enhancements in summer background CO and O3of 23–37 and 5–9 ppbv, respectively, at 10 sites in Alaska, Canada and the Pacific Northwest. From the area burned, we estimate that the Siberian fires generated 68 Tg of CO and 0.82 Tg of NOx(as N). In addition, we show that the background O3enhancement contributed to an exceedance of the ozone air quality standard in the Pacific Northwest. These results show that regional air quality and health are linked to global processes, including climate, forest fires and long‐range transport of pollutants.

Super‐large raindrops

Raindrops similar or greater in size to the largest ever observed, with maximum dimensions of at least 8.8 mm and possibly 1 cm, have been measured in rainshafts beneath cumulus congestus clouds spawned by a biomass fire in Brazil and in very clean conditions in the Marshall Islands. It is proposed that the super‐large raindrops were produced by the rapid growth of drops colliding with each other within narrow regions of cloud where liquid water contents were unusually high. In Brazil, the initial growth of super‐large raindrops might have been initiated by condensation onto giant smoke particles.

Linking horizontal and vertical transports of biomass fire emissionsto the tropical Atlantic ozone paradox during the Northern Hemisphere winter season: climatology

Abstract. During the Northern hemisphere winter season, biomass burning is widespread in West Africa, yet the total tropospheric column ozone values (&lt;30DU) over much of the Tropical Atlantic Ocean (15°N-5°S) are relatively low. At the same time, the tropospheric column ozone values in the Southern Tropical Atlantic are higher than those in the Northern Hemisphere (ozone paradox). We examine the causes for low tropospheric column ozone values by considering the horizontal and vertical transport of biomass fire emissions in West Africa during November through March, using observed data which characterizes fires, aerosols, horizontal winds, precipitation, lightning and outgoing longwave radiation. We have found that easterly winds prevail in the lower troposphere but transition to westerly winds at pressure levels lower than 500hPa. A persistent anticyclone over West Africa at 700hPa is responsible for strong easterly winds, which causes a net outflow of ozone/ozone precursors from biomass burning in West Africa across the Atlantic Ocean towards South America. The lowest outgoing longwave radiation (OLR) and highest precipitation rates are generally found over the central Atlantic, some distance downstream of fires in West Africa making the vertical transport of ozone and ozone precursors less likely and ozone destruction more likely. However, lightning over land areas in Central Africa and South America can lead to enhanced ozone levels in the upper troposphere especially over the Southern tropical Atlantic during the Northern Hemisphere winter season.

Development of Brachystegia-Julbernardia woodland after clear-felling in central Zambia: Evidence for high resilience

Abstract Question: Does the development of Brachystegia-Julbernardia (miombo) woodland after felling, and under a variable fire regime, occur via a seral stage of fire-tolerant species? Location: Four sites in central Zambia, Africa. Methods: Trees in replicate plots were clear-cut and stumps and resprouts enumerated. Species recruited into the tree layer (> 2.0 m tall) were monitored for 11 years (1991 – 2001) and fire occurrence and herbaceous biomass assessed annually to determine fuel loads. Results: Fire frequency was variable at the study sites and fuel loads were generally too low to suppress woodland regeneration after felling. However, at one site a change from low to high fire frequency arrested woodland development and triggered a regression towards a ‘fire-trap’ vegetation type in which a few fire-tolerant species survived. There was no evidence to support the hypothesis that miombo woodland regeneration is facilitated by a sere of fire-tolerant species. All regrowth after felling was from res...

Linking horizontal and vertical transports of biomass fire emissions to the Tropical Atlantic Ozone Paradox during the Northern Hemisphere winter season: 1999

The horizontal and vertical transport of biomass fire emissions in West Africa for January 1999, are examined using all available data including wind, fire, aerosol, precipitation, lightning and outgoing longwave radiation. Ozonesonde data from the Aerosols99 Trans‐Atlantic cruise are also included with rain and wind analyses. The results here support earlier studies that ozone and ozone precursors associated with biomass burning are confined to the lower troposphere primarily due to the lack of deep convection over land areas. Ozone and its precursors are horizontally transported equatorward or toward the west by winds in the 1000–700 hPa layers. However, rising adiabatic motions associated with the diurnal evolution of the West African planetary boundary layer can transport ozone and its precursors vertically into the free troposphere above the marine boundary layer. Moreover, lightning from South America, Central Africa and mesoscale convective systems in the Gulf of Guinea can lead to elevated ozone mixing ratios in the middle and upper troposphere of the tropical south Atlantic. The results presented here shed light of the proposed ozone paradox during Northern Hemisphere winter.

Vertical distribution of nighttime smoke following a wildland biomass fire in boreal Alaska

A comprehensive evaluation of the vertical structure of a smoldering smoke plume was afforded by a unique combination of tethersonde measurements (from ground level to about 400 m above ground level (AGL) or 274–674 m above sea level (ASL)), lidar sounding (from about 1.5 to 5 km ASL), and a video recording during the FROSTFIRE experimental burn in July 1999. Tethersonde and lidar measurements were made at local midnight. The video camera operated continuously for 1 week. Estimates of mass concentration were derived from the light‐scattering measurements. Every night, upper level smoke concentrations were estimated to be about 1000 times lower than near‐surface concentrations. The tethersonde instrument indicated maximum mass concentrations on the night following the most active burning (10–11 July), with the smoke trapped below an inversion at 115 m AGL. The lidar measurements indicated that maximum mass concentrations aloft (∼2000 m AGL) occurred on the next night (11–12 July), when the inversion was weaker, and estimated mass concentrations in the first few hundred meters ASL were smaller. The opportunistic combination of instruments offers the first available quantitative information on vertical plume structure in smoldering biomass smoke and holds promise for more a rigorous understanding of smoldering smoke as it significantly impacts visibility and human health.

Fungal spores are transported long distances in smoke from biomass fires

Abstract Viable fungal spores are present in smoke from distant biomass fires. This finding has potentially important implications for prescribed burning, agricultural management and public health. While attempting to find fungal spores in dust blown from China to Texas, one of us (S.A.M.) discovered that smoke from Yucatan contains viable bacteria and fungal spores, including the genera Alternaria, Cladosporium, Fusariella and Curvularia. There was a high correlation (r2=0.78) of spores and coarse carbon particles collected on microscope slides during 13 days of the 2002 smoke season. To eliminate possible contamination by local spores, an air sampler was flown from a kite at a Texas Gulf Coast beach during and after the 2003 smoke season on days when the NOAA back trajectory showed air arriving from Yucatan. Fifty-two spores and 19 coarse black carbon particles (>2.5 μm) were collected during a 30-min kite flight on the smoke day and 12 spores and four carbons on the day without smoke. We have found spores in smoke from an Arizona forest fire and in Asian smoke at Mauna Loa Observatory, Hawaii. We have tested these findings by burning dried grass, leaves, twigs and flood detritus. The smoke from all test fires contained many spores.

Reduction of false alarm rate in automatic forest fire infrared surveillance systems

One of the main problems related to infrared remote sensing of forest fires by automatic systems concerns the rejection of false alarms. The study of the infrared spectral radiance emitted by a biomass fire has been used to define spectral algorithms that permit to separate fires from other sources considered as false alarms. The different behaviour of the medium (3–5 μm) and thermal (8–12 μm) infrared spectral regions has been the basis for the definition of a new “figure” of merit, the so-called Fire Index (FI). An experimental burn has been used to test the ability of FI to identify clearly fires. A second algorithm based on an intraband analysis, the Mid-IR Fire Index (MFI), has been proposed to give complementary information to FI. Evolution of FI and MFI values with distance for different IR sources has been calculated. Finally, an experimental validation of both algorithms has been performed by using two infrared cameras working in the medium and thermal infrared spectral windows.

Effects of humidity on aerosols in southern Africa during the biomass burning season

Measurements of the aerosol total light scattering coefficient, σsp, and the aerosol hemispheric backscatter ratio, β(1), as functions of relative humidity (RH in %) (so‐called humidographs) at three wavelengths (450, 550, and 700 nm) were obtained in the dry season in southern Africa (1) in ambient air in South Africa, Botswana, Mozambique and Zambia, (2) at various distances downwind in identifiable smoke plumes from biomass fires, and (3) along the southwest coast of Africa. The ratio of σsp at an RH of 80% to that at 30% provides a measure of the effects of RH on σsp, and similarly for β(1). For the three broad sampling categories given above, and at a wavelength of 550 nm, these ratios varied from 1.42 ± 0.05 to 2.07 ± 0.03 for σsp, and from 0.69 ± 0.05 to 0.99 ± 0.14 for β(1). In general, humidographs for the ambient air samples showed a greater dependence on RH than those for smoke from identifiable biomass fires. During a period when dense, aged smoke was transported to the region from the north, the humidographs for σsp for ambient air samples were similar to those for identifiable smoke plume samples just ∼10‐ to 50‐min old. This suggests that as far as the effects of RH on σsp are concerned the effects of aging of smoke and its mixing with ambient air are realized within less than about an hour.

Individual aerosol particles from biomass burning in southern Africa: 1. Compositions and size distributions of carbonaceous particles

Individual aerosol particles in smoke plumes from biomass fires and in regional hazes in southern Africa were studied using analytical transmission electron microscopy (TEM), which allowed detailed characterization of carbonaceous particle types in smoke and determination of changes in particle properties and concentrations during smoke aging. Based on composition, morphology, and microstructure, three distinct types of carbonaceous particles were present in the smoke: organic particles with inorganic (K‐salt) inclusions, “tar ball” particles, and soot. The relative number concentrations of organic particles were largest in young smoke, whereas tar balls were dominant in a slightly aged (∼1 hour) smoke from a smoldering fire. Flaming fires emitted relatively more soot particles than smoldering fires, but soot was a minor constituent of all studied plumes. Further aging caused the accumulation of sulfate on organic and soot particles, as indicated by the large number of internally mixed organic/sulfate and soot/sulfate particles in the regional haze. Externally mixed ammonium sulfate particles dominated in the boundary layer hazes, whereas organic/sulfate particles were the most abundant type in the upper hazes. Apparently, elevated haze layers were more strongly affected by biomass smoke than those within the boundary layer. Based on size distributions and the observed patterns of internal mixing, we hypothesize that organic and soot particles are the cloud‐nucleating constituents of biomass smoke aerosols. Sea‐salt particles dominated in the samples taken in stratus clouds over the Atlantic Ocean, off the coast of Namibia, whereas a distinct haze layer above the clouds consisted of aged biomass smoke particles.

Trace gas chemistry in a young biomass burning plume over Namibia: Observations and model simulations

We investigated trace gas emissions from a biomass fire near Otavi, northern Namibia, on 13 September 2000 as part of the Southern African Regional Science Initiative 2000 (SAFARI 2000). Observations included fast measurements of carbon monoxide (CO), ozone (O3), acetone (propanone, CH3COCH3), and acetonitrile (ethanenitrile or methyl cyanide, CH3CN). Additionally, flask samples were taken and analyzed for nonmethane hydrocarbons (NMHCs). Measurements close to the fire were used to quantify the emissions of the different compounds. Several transects were flown through the plume downwind to study the chemical changes in the plume during the first 2 hours after the emission. Fast production of O3 was observed, with the O3/CO molar enhancement ratio ER(O3/CO) reaching ∼0.10 in the plume after 2 hours. Acetone molar enhancement ratios (ER(acetone/CO) were ∼5 × 10−3 in the very young plume but ∼9 × 10−3 after 1–2 hours of aging, pointing to a substantial fast secondary acetone formation. To understand the chemical processes occurring in the plume, we simulated the plume chemistry with a dilution box model. The fast O3 production is well reproduced, whereas acetone mixing ratios in the aging plume are underestimated by the model. This points to additional yet unidentified acetone precursors. The model suggests an overall molar enhancement ratio of these compounds with respect to CO of 7.5 × 10−3 and a reaction rate coefficient of 6 × 10−11 cm3 s−1 for the reaction with HO radicals. The secondary acetone production may cause the net acetone source from biomass burning to be underestimated when only data from observations immediately near the fires are considered. The atmospheric implications of these findings are discussed.

Trace gas and particle emissions from fires in large diameter and belowground biomass fuels

We adopt a working definition of residual smoldering combustion (RSC) as biomass combustion that produces emissions that are not lofted by strong fire‐induced convection. RSC emissions can be produced for up to several weeks after the passage of a flame front and they are mostly unaffected by flames. Fuels prone to RSC include downed logs, duff, and organic soils. Limited observations in the tropics and the boreal forest suggest that RSC is a globally significant source of emissions to the troposphere. This source was previously uncharacterized. We measured the first emission factors (EF) for RSC in a series of laboratory fires and in a wooded savanna in Zambia, Africa. We report EFRSC for both particles with diameter &lt;2.5 μm (PM2.5) and the major trace gases as measured by open‐path Fourier transform infrared (OP‐FTIR) spectroscopy. The major trace gases include carbon dioxide, carbon monoxide, methane, ethane, ethene, acetylene, propene, formaldehyde, methanol, acetic acid, formic acid, glycolaldehyde, phenol, furan, ammonia, and hydrogen cyanide. We show that a model used to predict trace gas EF for fires in a wide variety of aboveground fine fuels fails to predict EF for RSC. For many compounds, our EF for RSC‐prone fuels from the boreal forest and wooded savanna are very different from the EF for the same compounds measured in fire convection columns above these ecosystems. We couple our newly measured EFRSC with estimates of fuel consumption by RSC to refine emission estimates for fires in the boreal forest and wooded savanna. We find some large changes in estimates of biomass fire emissions with the inclusion of RSC. For instance, the wooded savanna methane EF increases by a factor of 2.5 even when RSC accounts for only 10% of fuel consumption. This shows that many more measurements of fuel consumption and EF for RSC are needed to improve estimates of biomass burning emissions.

Fine particulate matter source attribution for Southeast Texas using 14C/13C ratios

Radiocarbon analyses of fine particulate matter samples collected during the summer of 2000 in southeast Texas indicate that a substantial fraction of the aerosol carbon at an urban/suburban site (27–73%) and at a rural, forested site (44–77%) was modern carbon. Data from emission inventories and additional ambient measurements indicate that the most likely sources of this modern carbon are biomass burning fires and biogenic secondary organic aerosol.

Simulation of a biomass‐burning plume: Comparison of model results with observations

We have simulated the dynamical evolution of the plume from a prescribed biomass fire, using the active tracer high‐resolution atmospheric model (ATHAM). Initialization parameters were set to reflect the conditions during the fire. The model results are compared with airborne remote‐sensing and in situ measurements of the plume. ATHAM reproduces the injection height (250–600 m) and the horizontal extent of the plume (∼4 km) with good accuracy. The aerosol mass concentrations are underestimated but still in the range of the observations. Remaining differences between the model results and the measurements are attributed to limited meteorological and fire emission information. Additionally, radiative transfer simulations using in situ measurements of the aerosol properties are performed. A comparison of the measured and simulated reflected solar flux shows an underestimation by the model over the ocean surface, which is most likely due to an underestimation of the aerosol optical depth in the model. The instantaneous radiative forcing was calculated to −36 W m−2over land and −58 W m−2over the ocean for a solar zenith angle of 47° and an optical depth of unity, consistent with previous studies. Overall, it appears that ATHAM is a valuable tool for the examination of transport processes within biomass‐burning plumes and, together with a chemical and microphysical module, is suitable for studies of the interaction between transport, chemistry, and microphysics within such plumes.