Intact spores and submicrometer size fragments are released from moldy building materials during growth and sporulation. It is unclear whether all fragments originate from fungal growth or if small pieces of building materials are also aerosolized as a result of microbial decomposition. In addition, particles may be formed through nucleation from secondary metabolites of fungi, such as microbial volatile organic compounds (MVOCs). In this study, we used the elemental composition of particles to characterize the origin of submicrometer fragments released from materials contaminated by fungi.Particles from three fungal species (Aspergillus versicolor, Cladosporium cladosporioides and Penicillium brevicompactum), grown on agar, wood and gypsum board were aerosolized using the Fungal Spore Source Strength Tester (FSSST) at three air velocities (5, 16 and 27 m/s). Released spores (optical size, dp ≥ 0.8 micrometers) and fragments (dp ≤ 0.8 micrometers) were counted using direct-reading optical aerosol instruments. Particles were also collected on filters, and their morphology and elemental composition analyzed using scanning electron microscopes (SEM) coupled with an Energy-Dispersive X-ray spectroscopy (EDX).Among the studied factors, air velocity resulted in the most consistent trends in the release of fungal particles. Total concentrations of both fragments and spores increased with an increase in air velocity for all species whereas fragment-spore (F/S) ratios decreased. EDX analysis showed common elements, such as C, O, Mg and Ca, for blank material samples and fungal growth. However, N and P were exclusive to the fungal growth, and therefore were used to differentiate biological fragments from non-biological ones. Our results indicated that majority of fragments contained N and P.Because we observed increased release of fragments with increased air velocities, nucleation of MVOCs was likely not a relevant process in the formation of fungal fragments. Based on elemental composition, most fragments originated from fungi, but also fragments from growth material were detected.
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机译：完整的孢子和亚微米大小的碎片会在生长和发芽过程中从发霉的建筑材料中释放出来。尚不清楚所有碎片是否都来自真菌的生长，或者是否由于微生物的分解而使小的建筑材料也被雾化。另外，可以通过成核由真菌的次级代谢产物（例如微生物挥发性有机化合物（MVOC））形成颗粒。在这项研究中，我们使用颗粒的元素组成来表征被真菌污染的材料释放出的亚微米碎片的起源。分别在琼脂，木材和石膏板上生长的三种真菌物种（杂色曲霉，Cladosporium cladosporioides和短青霉）的颗粒被鉴定出来。使用真菌孢子源强度测试仪（FSSST）在三个风速（5、16和27 m / s）进行雾化。使用直读光学气溶胶仪对释放的孢子（光学尺寸，dp≥0.8微米）和碎片（dp≤0.8微米）进行计数。还在过滤器上收集颗粒，并使用扫描电子显微镜（SEM）结合能量色散X射线光谱仪（EDX）分析了它们的形态和元素组成。在研究的因素中，空气速度导致了空气中最一致的趋势。释放真菌颗粒。对于所有物种，碎片和孢子的总浓度均随风速的增加而增加，而碎片孢子（F / S）的比率则降低。 EDX分析显示空白物质样品和真菌生长中常见的元素，例如C，O，Mg和Ca。但是，N和P是真菌生长所独有的，因此可用于区分生物片段和非生物片段。我们的结果表明，大多数片段含有N和P.由于我们观察到片段的释放随空气速度的增加而增加，因此MVOC的成核可能与真菌片段的形成无关。基于元素组成，大多数片段都来自真菌，但也检测到了来自生长材料的片段。
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