Haldust

Haldust is a term used in environmental science and atmospheric research to describe aerosol particles that are enriched in halogen elements (fluorine, chlorine, bromine, iodine) or halogenated compounds. Because there is no universally defined standard, the term is used in different ways to denote either halogen-containing mineral dust or organic/inorganic particles with elevated halogen content.

Composition and forms: Haldust particles can be mineral-rich, containing silicates or carbonates with substituted halogen atoms, or organic-rich, containing halogenated organics adsorbed onto particle surfaces. Particle sizes typically span submicrometer to a few micrometers.

Formation and sources: In urban and industrial settings, haldust can originate from combustion of halogenated fuels and waste, industrial coatings or processes that emit halogenated compounds, and natural sources such as volcanic plumes where halogens are released and condense onto existing dust. Aging aerosols can accumulate halogens through reactions with atmospheric halogen reservoirs.

Physical and chemical properties: Halogen content influences volatility, hygroscopicity, and optical properties. Haldust may absorb or scatter light and participate in heterogeneous chemistry, including release of halogen radicals under sunlight, affecting local ozone chemistry.

Occurrence and measurement: Haldust has been reported in air quality studies near industrial zones, marine-influenced environments, and in volcanic regions. Sampling uses standard particulate matter collectors; analysis employs electron microscopy, X-ray spectroscopy, infrared and mass spectrometry to quantify halogen content and composition.

Impact and relevance: Because halogens influence atmospheric chemistry and can pose health or environmental risks, haldust is of interest for air quality monitoring and climate studies. See also: halogen aerosols, atmospheric chemistry, particulate matter.