Contribution of fungi to primary biogenic aerosols in the atmosphere: wet and dry discharged spores, carbohydrates, and inorganic ions

[摘要] Biogenic aerosols play important roles in atmospheric chemistry physics,the biosphere, climate, and public health. Here, we show that fungi whichactively discharge their spores with liquids into the air, in particularactively wet spore discharging Ascomycota (AAM) and actively wet sporedischarging Basidiomycota (ABM), are a major source of primary biogenicaerosol particles and components. We present the first estimates for theglobal average emission rates of fungal spores.

Measurement results and budget calculations based on investigations inAmazonia (Balbina, Brazil, July 2001) indicate that the spores of AAM andABM may account for a large proportion of coarse particulate matter intropical rainforest regions during the wet season (0.7–2.3 μg m⁻³). For the particle diameter range of 1–10 μm, the estimatedproportions are ~25% during day-time, ~45% at night, and~35% on average. For the sugar alcohol mannitol, the budgetcalculations indicate that it is suitable for use as a molecular tracer foractively wet discharged basidiospores (ABS). ABM emissions seem to accountfor most of the atmospheric abundance of mannitol (10–68 ng m⁻³), andcan explain the observed diurnal cycle (higher abundance at night). ABMemissions of hexose carbohydrates might also account for a significantproportion of glucose and fructose in air particulate matter (7–49 ng m⁻³), but the literature-derived ratios are not consistent with theobserved diurnal cycle (lower abundance at night). AAM emissions appear toaccount for a large proportion of potassium in air particulate matter overtropical rainforest regions during the wet season (17–43 ng m⁻³), andthey can also explain the observed diurnal cycle (higher abundance atnight). The results of our investigations and budget calculations fortropical rainforest aerosols are consistent with measurements performed atother locations.

Based on the average abundance of mannitol reported for extratropicalcontinental boundary layer air (~25 ng m⁻³), we have alsocalculated a value of ~17 Tg yr⁻¹ as a first estimate for theglobal average emission rate of ABS over land surfaces, which is consistentwith the typically observed concentrations of ABS (~10³–10⁴ m⁻³; ~0.1–1 μg m⁻³).The global average atmosphericabundance and emission rate of total fungal spores, including wet and drydischarged species, are estimated to be higher by a factor of about three,i.e. 1 μg m⁻³ and ~50 Tg yr⁻¹. Comparisons withestimated rates of emission and formation of other major types of organicaerosol (~47 Tg yr⁻¹ of anthropogenic primary organic aerosol;12–70 Tg yr⁻¹ of secondary organic aerosol) indicate that emissionsfrom fungi should be taken into account as a significant global source oforganic aerosol. The effects of fungal spores and related chemicalcomponents might be particularly important in tropical regions, where bothphysicochemical processes in the atmosphere and biological activity at theEarth's surface are particularly intense, and where the abundance of fungalspores and related chemical compounds are typically higher than inextratropical regions.

[学科分类] 大气科学