Spatial distribution and concentrations of salt fogs in a coastal urban environment: A case study in Zhuhai city

Coastal buildings are threatened by corrosive damage secondary to salt fogs. However, the unclearly salt-fog concentrations and their spatial distribution pattern, particularly in an urban environment, severely hinder targeted salt-fog-resistant designs for coastal buildings. Against this background, this study adopted the salt-fog sampling device and the spectrophotometric method to undertake simultaneous, multi-site field investigations on salt-fog concentrations in a coastal urban area in Zhuhai city in China, and then analyzed factors affecting such concentrations: meteorological conditions, offshore distances, and building barriers. Our results demonstrated that salt-fog concentrations in coastal urban spaces have similarities and differences with previous empirical studies in the marine environment. Firstly, salt-fog concentrations were directly affected by sea winds and tides, especially the wind direction, which is not present in the empirical studies in the marine environment. Then, it decreased monotonically with offshore distances in open coastal spaces. Furthermore, the spatial distribution of salt fog in the built environment depended critically on the degree to which the building was shielded from sea winds. Specifically, the single-building barrier was found to moderately reduce salt-fog concentrations on its leeward side (by up to 121.49 mu g/m3), while the enclosed-building barriers could block the intrusion of sea winds into the enclosed area, promoting consistently low concentrations (below 36.79 mu g/m3) there. Finally, adaptable salt-fog-resistant measures are recommended based on the spatial distribution investigation of salt-fog concen-trations in the built environment.