Brochosomes produced by leafhoppers-a widely unknown, yet highly abundant species of bioaerosols in ambient air

Brochosomes are excitingly shaped hollow spherical particles produced by leafhoppers (Cicadelliae), presumably to serve as a very efficient water-repellent protective surface coating. The spheroids have a diameter between 250 and 600 nm and are made of a network of protein–lipid rods, arranged in the form of hexagons and pentagons. Brochosomes in the atmosphere have been described only a few times and the reported concentrations were usually small. The cause of the apparently rare occurrence of these particles in ambient air is shown to be twofold. First, most of the brochosomes are airborne not as individual species, but in the form of rather large clusters containing up to 100,000 particles. Second, for high-efficiency collection of particles with aerodynamically complex morphology such as brochosomes (or agglomerates of carbon nanoparticles), size selective sampling with impactors turned out to be more efficient the higher the nozzle velocity. In a series of sampling campaigns brochosomes were found to be the most abundant bioaerosol particles in a semi-urban atmosphere during the warm season. Occasionally, brochosomes tended to react with other nanoparticle matter. As a result, the presumably freshly produced brochosomes became strongly distorted, rearranging in a variety of exotic forms, including perfect or distorted domes or even a spider web.