Fine dust collection capacity of a moss greening system for the building envelope: An experimental approach

Air pollution is one of the most impactful environmental issues worldwide in terms of mortality. Numerous studies have assessed the benefits of vertical greening systems within urban areas for mitigating air pollution, but their widespread adoption is limited by high costs and maintenance requirements. The current study assesses the air pollution mitigation capacity within urban areas of three moss species: Barbula unguiculata, Grimmia pulvinata and Homalothecium sericeum, used in the moss envelope system called MosSkin. Following a three-months exposure of the three moss species samples in a highly trafficked area, phyllids were analysed with Field Emission Scan Electron microscopy to quantify number, dimension, and nature of particle deposition on leaves on their different portions (base, centre, apex). The moss species chosen collected up to 45,580 particles per mm² with the trend H. sericeum ≥ G. pulvinata > B. unguiculata, showing a similar tendency in terms of classes and order of magnitudes. However, specific higher affinities for PM fractions 2–7.5 μm were shown by G. pulvinata. The PMx collection can be related to species-specific shape of leaves within stems, and it depends on the leaf portions (highest capture in apex), 45–55 % consisting of PM_0.5 μm, indicating a significant collecting capacity of such fractions.