Atmospheric chemistry of hydrogen fluoride

• Published in: Journal of atmospheric chemistry 2018-03, Vol.75 (1), p.1-16
• Main Author: Cheng, Meng-Dawn
• Format: Article
• Language: English
• Subjects: Acidity; Air pollution; Atmosphere; Atmospheric chemistry; Atmospheric models; Atmospheric ozone; Atmospheric particulate matter; Atmospheric particulates; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Atmospheric turbulence; Boundary layer parameters; Boundary layers; Chemical reactions; Chemistry; Computer applications; Computer simulation; Depolymerization; Deposition; Dispersion; Dry deposition; Earth and Environmental Science; Earth Sciences; Emissions; Fluorides; Hydrogen; Hydrogen fluoride; Low level; Modelling; Nitrogen oxides; Oligomers; Oxides; Ozone; Parameterization; Particulate emissions; Particulate matter; Photochemicals; Polymerization; Rain; Raindrop velocity; Removal; Residence time; Residential density; Risk assessment; Species; Sulfur; Sulfur dioxide; Surface boundary layer; Suspended particulate matter; Thermal properties; Thermodynamic properties; Transport; Troposphere; Velocity; Wet deposition
• ISSN: 0167-7764; 1573-0662
• DOI: 10.1007/s10874-017-9359-7

Although a large volume of monitoring and computer simulation data exist for global coverage of HF, study of HF in the troposphere is still limited to industry whose primary interest is the safety and risk assessment of HF release because it is a toxic gas. There is very limited information on atmospheric chemistry, emission sources, and the behavior of HF in the environment. We provide a comprehensive review on the atmospheric chemistry of HF, modeling the reactions and transport of HF in the atmosphere, the removal processes in the vertical layer immediately adjacent to the surface (up to approximately 500 m) and recommend research needed to improve our understanding of atmospheric chemistry of HF in the troposphere. The atmospheric chemistry, emissions, and surface boundary layer transport of hydrogen fluoride (HF) are summarized. Although HF is known to be chemically reactive and highly soluble, both factors affect transport and removal in the atmosphere, the chemistry can be ignored when the HF concentration is at a sufficiently low level (e.g., 10 ppmv). At a low concentration, the capability for HF to react in the atmosphere is diminished and therefore the species can be mathematically treated as inert during the transport. At a sufficiently high concentration of HF (e.g., kg/s release rate and thousands of ppm), however, HF can go through a series of rigorous chemical reactions including polymerization, depolymerization, and reaction with water to form molecular complex. As such, the HF species cannot be considered as inert because the reactions could intimately influence the plume’s thermodynamic properties affecting the changes in plume temperature and density. The atmospheric residence time of HF was found to be less than four (4) days, and deposition (i.e., atmosphere to surface transport) is the dominant mechanism that controls the removal of HF and its oligomers from the atmosphere. The literature data on HF dry deposition velocity was relatively high compared to many commonly found atmospheric species such as ozone, sulfur dioxide, nitrogen oxides, etc. The global average of wet deposition velocity of HF was found to be zero based on one literature source. Uptake of HF by rain drops is limited by the acidity of the rain drops, and atmospheric particulate matter contributes negligibly to HF uptake. Finally, given that the reactivity of HF at a high release rate and elevated mole concentration cannot be ignored, it is important to incorporate