Fig. 14
From: Ejection of marine microplastics by raindrops: a computational and experimental study
(a) Airborne time of spray droplets without updraft is in the order of half a second. No droplets are picked up by the atmosphere. (b) With \(1 \frac {\mathrm {m}}{\mathrm {s}}\) vertical updraft velocity, all droplets smaller than 0.26mm diameter have diverging airborne time (capped at finite values so that the data points are visible in the diagram). The black curve represents the lifetime (time until full evaporation, Eq. (11)) of droplets depending on diameter. If the airborne time is larger than the lifetime, the droplets are considered picked up by the atmosphere. (c) The number of picked up microplastic particles per raindrop impact increases with vertical updraft velocity. Numbers are given for an initial concentration of 5000 microplastic particles per cm3 in the sea water as used in our simulations. Additional figures and data in Figure S24 and Table S3