Surface water formation on the natural surface under supersaturation: from local water balance to air pollutant deposition

AbstractHeterogeneous nucleation and subsequent growth of surface water occur on hydrophobic natural substrates under supersaturation; however, this basic physical relationship has been explained only empirically as yet. In order to derive a new method to determine supersaturation at the canopy –air interface, we considered the parameters that contribute to surface water formation (SWF) and examined their importance by field observations at an urban site in the period 2015–2017. We found that both the interfacial and vertical temperature differences ranged 1–3 K and that they were n ecessary but not sufficient for supersaturated condensation on natural surfaces. Excess supply of moisture must exist and continuously contribute to the growth of the condensed water nuclei, which may originate from external sources such as atmospheric advection. Under the additional moisture supply , SWF appeared not only on the ground soil but also on the vegetation canopy at heights of 1–2 m. We also found that the SWF plays a role in the removal of ground-level air pollutants. The removal efficiency for [SO42 − + NO3−] of the deposition flux was estimated as ~  0.3 mmol (per [Ca2+] meq)/m2(per leaf area) during SWF.
Source: Air Quality, Atmosphere and Health - Category: Environmental Health Source Type: research