10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

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Ice Nuclei Activity of Fungal Spores Collected in the Metropolitan Area of São Paulo, Brazil

ANA PAULA MENDES EMYGDIO, Dulcilena de Matos Castro Silva, Ricardo Matheus Pires, Fabio Luiz Teixeira Goncalves, Maria de Fatima Andrade, University of Sao Paulo

Abstract Number: 1325
Working Group: Bioaerosols

Abstract
Bioaerosols are related to respiratory diseases and also have an impact on several atmospheric processes, such as scattering and absorption of radiation and they can influence on cloud formation being cloud condensation nuclei (CCN) and ice nuclei (IN). Several studies have been performed to determinate the capability of the bioaerosol to be ice nuclei, specially bacteria and fungal spores. The aim of this work was to evaluate the ice nuclei activity (INA+) of several fungal spores present in the atmosphere of Sao Paulo. To achieve these objectives, fungal spores were collected in the metropolitan area of São Paulo with two methodologies: using the impactador "AR MAS 100-ECO" (Merck, FR) (250 liters) with modified DRBCm Dichloran Rose-Bengal culture media and extract with ethanol solution; and for the Basidiomycota group, fruiting bodies were collected in the forest fragment (Parque Estadual das Fontes do Ipiranga) and the spores were extracted using the spore print methodology. After the collection, freezing tests were performed using a thermostatic bath with ethanol and water, the amount of spore in each solution was determinate with a Neubauer chamber. A total of 32 drops with 10µl from each of the 13 fungal types were tested considering three different dilutions including: Henningsia brasiliensis (Hb), Macrolepiota sp. (M), Ganoderma australe (Gs), Dichomitus setulosus (Ds), Flaviporus liebmanii (Fl), Pycnoporus sanguineus (Ps), Fusarium sp. (F), Trichoderma sp. (T), Aspergillus sp. (A), Aspergillus niger (An), Antrodiella liebmannii (Al), Ceriporia xylostromatoides (Cx), Arbortiporus fractipes (Af). Ultrapure Milli-Q water was also tested for comparison. In all tests the ultrapure Milli-Q water starts to freeze below -20ºC. The total volume of spores suspended for the three dilutions was (i) 10⁺⁶/10⁺⁷ spores/mL, (ii) 10⁺⁵/10⁺⁶ spores/mL, (iii) 10⁺⁵/10⁺⁴ spores/mL. Only the Gs had a dilution factor of (i) 10⁺⁴ spores/mL, (ii) 10⁺³ spores/mL and (iii) 10⁺² spores/mL. The higher initial freezing temperature for all spore tested was -9ºC for M and Af and the lower initial freezing temperature was -22ºC for T considering the most concentrated solution (i -10⁺⁷ spores/mL). The initial freezing temperature increased as more concentrated the solution. The initial and final temperature of freezing and the first and last cumulative ice nucleation activity per spore according to the calculation of Vali (1971) for the (i) dilution were: Hb (-14ºC/-25ºC; 1.9x10^-05; 1.1x10^-03), M (-9ºC/-25ºC; 1.6x10^-6), Gs (-11ºC/-25ºC; 1.3x10^-4), Ds (-14ºC/-25ºC; 3.3x10^-7; 8.5x10^-6), Fl (-11ºC/-25ºC; 2.9x10^-6), Ps (-14ºC/-25ºC; 3.3x10^-8), F (-16ºC/-23ºC; 6.7x10^-7; 2.4x10^-5), T (-22ºC/-23ºC; 1.8x10^-7; 3.6x10^-7), A (-13ºC/-23ºC; 9.6x10^-7; 4.2x10^-5), An (-19ºC/-23ºC; 2.4x10^-7; 8.0x10^-6), Al (-15ºC/-21ºC; 3.4x10^-7; 3.7x10^-5), Cx (-14ºC/-21ºC; 1.4x10^-6), Af (-9ºC; 4.9x10^-6; 5.3x10^-4). The freezing temperature of all spores tested indicates that they could contributed to a heterogeneous ice cloud formation, since all spores freeze in a temperature warmer than -19ºC (except for the T) and the ultrapure Milli-Q water freeze in temperature colder than -20ºC. However, only the Macrolepiota sp. and the Arbortiporus fractipescan presented significant ice nuclei activity with this experimental design. It should be considered that factors other than temperature should be accounted for the heterogeneous ice cloud formation, such as the size of the spore and the height needed to reach the temperature required for freezing.