Key drivers of pyrogenic carbon redistribution during a simulated rainfall event

Abstract. Pyrogenic carbon (PyC) is produced by the incomplete combustion of vegetation during wildfires and is a major and persistent pool of the global carbon (C) cycle. However, its redistribution in the landscape after fires remains largely unknown. Therefore, we conducted rainfall simulation experiments on 0.25 m2 plots with two distinct Swiss forest soils (Cambisol (clay loam) and Luvisol (sandy silt)). We applied PyC produced from wood (Picea abies) labeled under FACE conditions and C4 grass (Miscanthus sinensis) to the soil surface to study PyC redistribution by runoff and splash and the vertical mobility of PyC in a 10 cm unsaturated soil column based on the differences in δ13C of soils and PyC. We assessed the effect of soil texture, slope angle and PyC characteristics (feedstock and particle size) on the mobility of PyC during 30 min of intense rainfall (102 mm h−1). Our results highlight that PyC is highly mobile. Surface runoff transported between 0.2 % and 36.0 % of the total added PyC. Erosion by splash further redistributed 10.3 % to 25.3 % of the added PyC. Soil type had a substantial impact on the redistribution of PyC by both runoff and splash: on average, we recovered 10.5 % of the added PyC in runoff and splashed material for the clay-rich Cambisol and 61.3 % of the added PyC for the sandy silt Luvisol combined. PyC feedstock had a clear but contrasting effect on PyC redistribution: relocation in the runoff and splashed material was greater for wood PyC (43.4 % of total added PyC) than grass PyC (28.4 %). However, more wood PyC (11.5 %; fraction of organic C derived from the PyC) remained where it was initially applied compared to grass PyC (7.4 %). The results further suggest that the effect of PyC characteristics on its mobility can be highly variable and depend not only on the material from which it was derived, but also on other factors (e.g., particle size, porosity, density). In particular, the mobility of PyC was almost twice as large for fine-grained PyC (< 63 µm) than for coarse PyC (63 µm–2 mm). Vertical mobility of PyC up to 10 cm depth was greater in the clay-rich, well-aggregated Cambisol but limited in the physically instable Luvisol, likely due to quick aggregate breakdown and surface sealing. The addition of PyC to the surface of the studied soils further induced changes in the export of native soil organic carbon (nSOC) after the 30 min rainfall event. Our study shows that large quantities of PyC can be redistributed by water erosion over short timescales and that the mobility of PyC depends to a great extent on the response of soils to rainfall. Moreover, the addition and redistribution of PyC affects the export of nSOC and thus the C budget of fire-affected soils and catchments.

Download Full-text

Key drivers of pyrogenic carbon redistribution during a simulated rainfall event

10.5194/bg-2020-361 ◽

2020 ◽

Author(s):

Severin-Luca Bellè ◽

Asmeret Asefaw Berhe ◽

Frank Hagedorn ◽

Cristina Santin ◽

Marcus Schiedung ◽

...

Keyword(s):

Particle Size ◽

Soil Column ◽

Slope Angle ◽

Rainfall Simulation ◽

Miscanthus Sinensis ◽

Substantial Impact ◽

Organic C ◽

Pyrogenic Carbon ◽

Sandy Silt ◽

C Cycle

Abstract. Pyrogenic carbon (PyC) is produced by the incomplete combustion of vegetation during wildfires and is a major and persistent pool of the global carbon (C) cycle. However, its redistribution in the landscape after fires remains largely unknown. Therefore, we conducted rainfall simulation experiments on 0.25-m2 plots with two distinct Swiss forest soils (Cambisol (clay loam) and Luvisol (sandy silt)). We applied PyC produced from wood (Picea abies) labelled under FACE conditions and C4-grass (Miscanthus sinensis) to the soil surface to study PyC redistribution by runoff and splash, and the vertical mobility of PyC in a 10 cm unsaturated soil column based on the differences in δ13C of soils and PyC. We assessed the effect of soil texture, slope angle and PyC characteristics (feedstock and particle size) on the mobility of PyC during 30 minutes of intense rainfall (102 mm h−1). Our results highlight that PyC is highly mobile. Surface runoff transported between 0.2 to 36.0 % of the total added PyC. Erosion by splash further redistributed 10.3 to 25.3 % of the added PyC. Soil type had a substantial impact on the redistribution of PyC by both runoff and splash: on average, we recovered 10.5 % of the added PyC in runoff and splashed material for the clay-rich Cambisol and 61.3 % of the added PyC for the sandy silt Luvisol combined. PyC feedstock had a clear, but contrasting effect on PyC redistribution: relocation in the runoff and splashed material was greater for wood-PyC (43.4 % of total added PyC) than grass-PyC (28.4 %). However, more wood-PyC (11.5 %; fraction of organic C derived from the PyC) remained where it was initially applied compared to grass-PyC (7.4 %). The results further suggest that the effect of PyC characteristics on its mobility can be highly variable and depend not only on the material from which it was derived, but also on other factors (e.g. particle size, porosity, density). In particular, the mobility of PyC was almost twice as large for fine-grained PyC (

Download Full-text

Lateral redistribution of fire-derived carbon: A rainfall simulation experiment

10.5194/egusphere-egu2020-5765 ◽

2020 ◽

Author(s):

Severin-Luca Bellè ◽

Asmeret Asefaw Berhe ◽

Frank Hagedorn ◽

Marcus Schiedung ◽

Samuel Abiven

Keyword(s):

Soil Surface ◽

Water Erosion ◽

Rainfall Simulation ◽

Clay Loam ◽

Clay Loam Soil ◽

Organic C ◽

Sandy Silt ◽

C Cycle ◽

Loam Soil ◽

Runoff Sediment

Wildfires are a key component in the global carbon (C) cycle, releasing significant amount of CO2 to the atmosphere, but also producing one of the most persistent terrestrial organic C forms by the incomplete combustion of natural vegetation, namely fire-derived or pyrogenic carbon (PyC). Post-fire, PyC is deposited on the soil surface, but can then be laterally redistributed by wind or water erosion. Due to the lack of vegetation cover after a fire, primary factors that govern rate of PyC distribution post-fire will be changes in soil surface properties and physical characteristics of PyC. However, the drivers and quantities of transported PyC (and non-fire derived organic matter) by water erosion from its site of production remain largely unknown, which limits our understanding of PyC movement in the landscape.In this study, we tracked PyC erosion (and movement in soil) in a controlled experiment using a gravity-type rainfall simulator (at an intensity of 50mmh-1). We studied the quantity of PyC eroded from the soil surface (runoff and splash sediment) as well as its vertical movement within the soil (soil cores) for two Swiss temperate forest soils (initial soil moisture of 12-16%). We calculated the distribution of PyC using the isotopic 13C signature differences of grass-PyC (Miscanthus grass), wood-PyC (spruce wood grown under FACE conditions) and natural forest soil C in soil flume of 0.25m2. We studied the combination of the following factors: soil texture (sandy silt and clay loam), slope (10&#176; and 25&#176;), PyC particle size (63&#181;m and 63&#181;m-2mm) and PyC feedstock (grass and wood) to identify the major drivers of PyC redistribution.We hypothesize that: i) higher quantities of PyC can be found in the sediment of the sandy silt soil, with higher slopes and with bigger PyC particles, ii) higher quantities of PyC move vertically in the clay loam soil and with smaller PyC particles and iii) PyC is preferentially eroded compared to bulk SOC.Results suggest that we find 100 times more runoff sediment on sandy silt soil compared to clay loam soil, and two times more runoff sediment on 25&#176; slope compared to 10&#176;. We also find 1.5 times more splash erosion on sandy silt soil than on the clay loam soil. Regarding PyC erosion, observations suggest that > 50% of initial PyC is eroded on the sandy silt soil, whereas a majority of the PyC particles moves vertically through the soil for the clay loam.

Download Full-text

How much fire-derived carbon is transported vertically through the soil and what controls its mobility?

10.5194/egusphere-egu2020-6600 ◽

2020 ◽

Author(s):

Marcus Schiedung ◽

Severin-Luca Bellè ◽

Alysha Coppola ◽

Samuel Abiven

Keyword(s):

Experimental Approach ◽

Sandy Loam ◽

Soil Column ◽

Experimental Period ◽

Soil Mineral ◽

Mineral Phase ◽

Organic C ◽

Pyrogenic Carbon ◽

Vertical Mobility

Wildfires produce a fire-derived carbon (C) residue known as pyrogenic carbon (PyC). This residue is one of the largest and most persistent terrestrial organic C pools with residence times over 1000 years. Large quantities of PyC can remain on the site where the fire occurs or can be transferred along the landscape and eventually enter the soil where it represents a major component of the total soil organic carbon (SOC). The drivers explaining the vertical PyC mobility in soils and the quantities it represents remain largely unknown, which limits our understanding of the fate of PyC in the terrestrial systems. Here, we used a manipulative soil column experimental approach in order to study the proportion of transportable PyC and its interaction with the soil mineral phase and non-fire-derived SOC during its vertical transport. To do this, we applied highly 13C-labelled ryegrass biochar (as a PyC proxy) on the upper layer of small soil columns (7 cm length, 2.5 cm diameter), and traced the fire-derived C in the soil and in the soluble fractions sequentially extracted during a percolation of 600 pore volumes under saturated conditions (equivalent to 18 years continues rainfall). We studied a combination of ranging soil texture (sandy loam and sand), SOC content (0.3-3.0%) and weathering state (age) of the ryegrass biochar (artificial oxidation with H2O2) to identify drivers controlling the vertical mobility of fire-derived C. We hypothesized that: i) Significant proportions of fire-derived C are transported through the soil column over the whole experimental period but decrease with time, ii) fire-derived C can be retained and stabilized within the soil column and influence the mobility of non-fire-derived SOC and iii) weathered fire-derived C is more mobile than fresh fire-derived C which may control its long-term fate in soils.

Download Full-text

Reference carbon cycle dataset for typical Chinese forests via colocated observations and data assimilation

Scientific Data ◽

10.1038/s41597-021-00826-w ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Honglin He ◽

Rong Ge ◽

Xiaoli Ren ◽

Li Zhang ◽

Qingqing Chang ◽

...

Keyword(s):

Northern Hemisphere ◽

Global Climate ◽

Meteorological Data ◽

C Sequestration ◽

Research Network ◽

Soil Biology ◽

Area Index ◽

Ecosystem Research ◽

Organic C ◽

C Cycle

AbstractChinese forests cover most of the representative forest types in the Northern Hemisphere and function as a large carbon (C) sink in the global C cycle. The availability of long-term C dynamics observations is key to evaluating and understanding C sequestration of these forests. The Chinese Ecosystem Research Network has conducted normalized and systematic monitoring of the soil-biology-atmosphere-water cycle in Chinese forests since 2000. For the first time, a reference dataset of the decadal C cycle dynamics was produced for 10 typical Chinese forests after strict quality control, including biomass, leaf area index, litterfall, soil organic C, and the corresponding meteorological data. Based on these basic but time-discrete C-cycle elements, an assimilated dataset of key C cycle parameters and time-continuous C sequestration functions was generated via model-data fusion, including C allocation, turnover, and soil, vegetation, and ecosystem C storage. These reference data could be used as a benchmark for model development, evaluation and C cycle research under global climate change for typical forests in the Northern Hemisphere.

Download Full-text

Long term trends in fertility of soils under continuous cultivation and cereal cropping in southern Queensland. III. Distribution and kinetics of soil organic carbon in particle size fractions

Soil Research ◽

10.1071/sr9860293 ◽

1986 ◽

Vol 24 (2) ◽

pp. 293 ◽

Cited By ~ 67

Author(s):

RC Dalal ◽

RJ Mayer

Keyword(s):

Particle Size ◽

Organic Matter ◽

Organic Carbon ◽

Soil Organic Carbon ◽

Size Fraction ◽

Organic C ◽

Size Fractions ◽

Particle Size Fractions ◽

Clay Size Fraction ◽

Sand Size

Distribution of soil organic carbon in sand-, silt- and clay-size fractions during cultivation for periods ranging from 20 to 70 years was studied in six major soils used for cereal cropping in southern Queensland. Particle-size fractions were obtained by dispersion in water using cation exchange resin, sieving and sedimentation. In the soils' virgin state no single particle-size fraction was found to be consistently enriched as compared to the whole soil in organic C in all six soils, although the largest proportion (48%) of organic C was in the clay-size fraction; silt and sand-size fractions contained remaining organic C in equal amounts. Upon cultivation, the amounts of organic C declined from all particle-size fractions in most soils, although the loss rates differed considerably among different fractions and from the whole soil. The proportion of the sand-size fraction declined rapidly (from 26% to 12% overall), whereas that of the clay-size fraction increased from 48% to 61% overall. The proportion of silt-size organic C was least affected by cultivation in most soils. It was inferred, therefore, that the sand-size organic matter is rapidly lost from soil, through mineralization as well as disintegration into silt-size and clay-size fractions, and that the clay fraction provides protection for the soil organic matter against microbial and enzymic degradation.

Download Full-text

Soil organic carbon stabilization mechanisms and temperature sensitivity in old terraced soils

Biogeosciences ◽

10.5194/bg-18-6301-2021 ◽

2021 ◽

Vol 18 (23) ◽

pp. 6301-6312

Author(s):

Pengzhi Zhao ◽

Daniel Joseph Fallu ◽

Sara Cucchiaro ◽

Paolo Tarolli ◽

Clive Waddington ◽

...

Keyword(s):

Organic Carbon ◽

Soil Organic Carbon ◽

Temperature Sensitivity ◽

Land Surface ◽

C:N Ratio ◽

Temperature Sensitive ◽

Organic C ◽

Fraction Composition ◽

Soil Burial ◽

C Cycle

Abstract. Being the most common human-created landforms, terrace construction has resulted in an extensive perturbation of the land surface. However, our mechanistic understanding of soil organic carbon (SOC) (de-)stabilization mechanisms and the persistence of SOC stored in terraced soils is far from complete. Here we explored the factors controlling SOC stability and the temperature sensitivity (Q10) of abandoned prehistoric agricultural terrace soils in NE England using soil fractionation and temperature-sensitive incubation combined with terrace soil burial-age measurements. Results showed that although buried terrace soils contained 1.7 times more unprotected SOC (i.e., coarse particulate organic carbon) than non-terraced soils at comparable soil depths, a significantly lower potential soil respiration was observed relative to a control (non-terraced) profile. This suggests that the burial of former topsoil due to terracing provided a mechanism for stabilizing SOC. Furthermore, we observed a shift in SOC fraction composition from particulate organic C towards mineral-protected C with increasing burial age. This clear shift to more processed recalcitrant SOC with soil burial age also contributes to SOC stability in terraced soils. Temperature sensitivity incubations revealed that the dominant controls on Q10 depend on the terrace soil burial age. At relatively younger ages of soil burial, the reduction in substrate availability due to SOC mineral protection with aging attenuates the intrinsic Q10 of SOC decomposition. However, as terrace soil becomes older, SOC stocks in deep buried horizons are characterized by a higher temperature sensitivity, potentially resulting from the poor SOC quality (i.e., soil C:N ratio). In conclusion, terracing in our study site has stabilized SOC as a result of soil burial during terrace construction. The depth–age patterns of Q10 and SOC fraction composition of terraced soils observed in our study site differ from those seen in non-terraced soils, and this has implications when assessing the effects of climate warming and terrace abandonment on the terrestrial C cycle.

Download Full-text

Evaluation of terrestrial pan-Arctic carbon cycling using a data-assimilation system

Earth System Dynamics ◽

10.5194/esd-10-233-2019 ◽

2019 ◽

Vol 10 (2) ◽

pp. 233-255 ◽

Cited By ~ 4

Author(s):

Efrén López-Blanco ◽

Jean-François Exbrayat ◽

Magnus Lund ◽

Torben R. Christensen ◽

Mikkel P. Tamstorf ◽

...

Keyword(s):

The Arctic ◽

Soil Organic C ◽

Area Index ◽

Organic C ◽

Soil C ◽

Transit Times ◽

C Cycle ◽

C Stocks ◽

Data Assimilation System ◽

Assimilation System

Abstract. There is a significant knowledge gap in the current state of the terrestrial carbon (C) budget. Recent studies have highlighted a poor understanding particularly of C pool transit times and of whether productivity or biomass dominate these biases. The Arctic, accounting for approximately 50 % of the global soil organic C stocks, has an important role in the global C cycle. Here, we use the CARbon DAta MOdel (CARDAMOM) data-assimilation system to produce pan-Arctic terrestrial C cycle analyses for 2000–2015. This approach avoids using traditional plant functional type or steady-state assumptions. We integrate a range of data (soil organic C, leaf area index, biomass, and climate) to determine the most likely state of the high-latitude C cycle at a 1∘ × 1∘ resolution and also to provide general guidance about the controlling biases in transit times. On average, CARDAMOM estimates regional mean rates of photosynthesis of 565 g C m−2 yr−1 (90 % confidence interval between the 5th and 95th percentiles: 428, 741), autotrophic respiration of 270 g C m−2 yr−1 (182, 397) and heterotrophic respiration of 219 g C m−2 yr−1 (31, 1458), suggesting a pan-Arctic sink of −67 (−287, 1160) g Cm−2 yr−1, weaker in tundra and stronger in taiga. However, our confidence intervals remain large (and so the region could be a source of C), reflecting uncertainty assigned to the regional data products. We show a clear spatial and temporal agreement between CARDAMOM analyses and different sources of assimilated and independent data at both pan-Arctic and local scales but also identify consistent biases between CARDAMOM and validation data. The assimilation process requires clearer error quantification for leaf area index (LAI) and biomass products to resolve these biases. Mapping of vegetation C stocks and change over time and soil C ages linked to soil C stocks is required for better analytical constraint. Comparing CARDAMOM analyses to global vegetation models (GVMs) for the same period, we conclude that transit times of vegetation C are inconsistently simulated in GVMs due to a combination of uncertainties from productivity and biomass calculations. Our findings highlight that GVMs need to focus on constraining both current vegetation C stocks and net primary production to improve a process-based understanding of C cycle dynamics in the Arctic.

Download Full-text

Representation of dissolved organic carbon in the JULES land surface model (vn4.4_JULES-DOCM)

Geoscientific Model Development ◽

10.5194/gmd-11-593-2018 ◽

2018 ◽

Vol 11 (2) ◽

pp. 593-609 ◽

Cited By ~ 7

Author(s):

Mahdi Nakhavali ◽

Pierre Friedlingstein ◽

Ronny Lauerwald ◽

Jing Tang ◽

Sarah Chadburn ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Land Surface ◽

Soil Column ◽

River System ◽

Terrestrial Ecosystems ◽

Surface Model ◽

Organic C ◽

C Cycle ◽

Doc Concentration

Abstract. Current global models of the carbon (C) cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, thus not considering the lateral transport of carbon from the continents to the oceans. Therefore, those models implicitly consider all of the C which is not respired to the atmosphere to be stored on land and hence overestimate the land C sink capability. A model that represents the whole continuum from atmosphere to land and into the ocean would provide a better understanding of the Earth's C cycle and hence more reliable historical or future projections. A first and critical step in that direction is to include processes representing the production and export of dissolved organic carbon in soils. Here we present an original representation of dissolved organic C (DOC) processes in the Joint UK Land Environment Simulator (JULES-DOCM) that integrates a representation of DOC production in terrestrial ecosystems based on the incomplete decomposition of organic matter, DOC decomposition within the soil column, and DOC export to the river network via leaching. The model performance is evaluated in five specific sites for which observations of soil DOC concentration are available. Results show that the model is able to reproduce the DOC concentration and controlling processes, including leaching to the riverine system, which is fundamental for integrating terrestrial and aquatic ecosystems. Future work should include the fate of exported DOC in the river system as well as DIC and POC export from soil.

Download Full-text

Fe(II)-catalyzed transformation of Fe (hydr)oxides in particle-size soil organic matter fractions from amended agricultural soils

10.5194/egusphere-egu2020-14873 ◽

2020 ◽

Author(s):

Beatrice Giannetta ◽

Ramona Balint ◽

Daniel Said-Pullicino ◽

César Plaza ◽

Maria Martin ◽

...

Keyword(s):

Particle Size ◽

Organic Matter ◽

Soil Organic Matter ◽

Agricultural Soils ◽

Solid Phase ◽

Organic Amendments ◽

Fine Sand ◽

Organic C ◽

Amended Soils ◽

Mineral Transformations

Redox-driven changes in Fe crystallinity and speciation may affect soil organic matter (SOM) stabilization and carbon (C) turnover, with consequent influence on global terrestrial soil organic carbon (SOC) cycling.&#160;Under reducing conditions, increasing concentrations of Fe(II) released in solution from the reductive dissolution of Fe (hydr)oxides may accelerate ferrihydrite transformation, although our understanding of the influence of SOM on these transformations is still lacking.&#160;Here, we evaluated abiotic Fe(II)-catalyzed mineralogical changes in Fe (hydr)oxides in bulk soils and size-fractionated SOM pools (for comparison, fine silt plus clay, FSi+Cl, and fine sand, FSa) of an agricultural soil, unamended or amended with biochar, municipal solid waste compost, and a combination of both.&#160;FSa fractions showed the most significant Fe(II)-catalyzed ferrihydrite transformations with the consequent production of well-ordered Fe oxides irrespective of soil amendment, with the only exception being the compost-amended soils. In contrast, poorly crystalline ferrihydrite still constituted ca. 45% of the FSi+Cl fractions of amended soils, confirming the that the higher SOM content in this fraction inhibits atom exchange between aqueous Fe(II) and the solid phase. Building on our knowledge of Fe(II)-catalyzed mineralogical changes in simple systems, our results evidenced that the mechanisms of abiotic Fe mineral transformations in bulk soils depend on Fe mineralogy, organic C content and quality, and organo-mineral associations that exist across particle-size SOM pools. Our results underline that in the fine fractions the increase in SOM due to organic amendments can contribute to limiting abiotic Fe(II)-catalyzed ferrihydrite transformation, while coarser particle-size fractions represent an understudied pool of SOM subjected to Fe mineral transformations.&#160;

Download Full-text

Biomass burning emissions of trace gases and particles in marine air at Cape Grim, Tasmania

Atmospheric Chemistry and Physics ◽

10.5194/acp-15-13393-2015 ◽

2015 ◽

Vol 15 (23) ◽

pp. 13393-13411 ◽

Cited By ~ 15

Author(s):

S. J. Lawson ◽

M. D. Keywood ◽

I. E. Galbally ◽

J. L. Gras ◽

J. M. Cainey ◽

...

Keyword(s):

Particle Size ◽

Biomass Burning ◽

Cloud Condensation Nuclei ◽

Trace Gases ◽

Particle Growth ◽

Dominant Mode ◽

Condensation Nuclei ◽

Substantial Impact ◽

Marine Air ◽

Cape Grim

Abstract. Biomass burning (BB) plumes were measured at the Cape Grim Baseline Air Pollution Station during the 2006 Precursors to Particles campaign, when emissions from a fire on nearby Robbins Island impacted the station. Measurements made included non-methane organic compounds (NMOCs) (PTR-MS), particle number size distribution, condensation nuclei (CN) > 3 nm, black carbon (BC) concentration, cloud condensation nuclei (CCN) number, ozone (O3), methane (CH4), carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), nitrous oxide (N2O), halocarbons and meteorology. During the first plume strike event (BB1), a 4 h enhancement of CO (max ~ 2100 ppb), BC (~ 1400 ng m-3) and particles > 3 nm (~ 13 000 cm-3) with dominant particle mode of 120 nm were observed overnight. A wind direction change lead to a dramatic reduction in BB tracers and a drop in the dominant particle mode to 50 nm. The dominant mode increased in size to 80 nm over 5 h in calm sunny conditions, accompanied by an increase in ozone. Due to an enhancement in BC but not CO during particle growth, the presence of BB emissions during this period could not be confirmed. The ability of particles > 80 nm (CN80) to act as CCN at 0.5 % supersaturation was investigated. The ΔCCN / ΔCN80 ratio was lowest during the fresh BB plume (56 ± 8 %), higher during the particle growth period (77 ± 4 %) and higher still (104 ± 3 %) in background marine air. Particle size distributions indicate that changes to particle chemical composition, rather than particle size, are driving these changes. Hourly average CCN during both BB events were between 2000 and 5000 CCN cm-3, which were enhanced above typical background levels by a factor of 6–34, highlighting the dramatic impact BB plumes can have on CCN number in clean marine regions. During the 29 h of the second plume strike event (BB2) CO, BC and a range of NMOCs including acetonitrile and hydrogen cyanide (HCN) were clearly enhanced and some enhancements in O3 were observed (ΔO3 / ΔCO 0.001–0.074). A short-lived increase in NMOCs by a factor of 10 corresponded with a large CO enhancement, an increase of the NMOC / CO emission ratio (ER) by a factor of 2–4 and a halving of the BC / CO ratio. Rainfall on Robbins Island was observed by radar during this period which likely resulted in a lower fire combustion efficiency, and higher emission of compounds associated with smouldering. This highlights the importance of relatively minor meteorological events on BB emission ratios. Emission factors (EFs) were derived for a range of trace gases, some never before reported for Australian fires, (including hydrogen, phenol and toluene) using the carbon mass balance method. This provides a unique set of EFs for Australian coastal heathland fires. Methyl halide EFs were higher than EFs reported from other studies in Australia and the Northern Hemisphere which is likely due to high halogen content in vegetation on Robbins Island. This work demonstrates the substantial impact that BB plumes can have on the composition of marine air, and the significant changes that can occur as the plume interacts with terrestrial, aged urban and marine emission sources.

Download Full-text