Modelling indoor radical chemistry during the HOMEChem campaign

Area of Science:

• Indoor air chemistry
• Atmospheric chemistry
• Environmental science

Background:

• Indoor environments expose occupants to air pollutants from indoor sources and outdoor air exchange.
• Peak pollutant concentrations are often driven by indoor activities such as cooking and cleaning.
• Understanding indoor air chemistry is crucial for assessing occupant health and environmental impact.

Purpose of the Study:

• To investigate the impact of household cleaning and cooking on indoor air chemistry using a chemical model.
• To quantify the concentrations of key reactive species, including hydroxyl (OH) radicals, hydroperoxyl radicals, and nitrous acid (HONO).
• To assess the reactivity of chlorine (Cl) atoms and OH radicals during and after these activities.

Main Methods:

• Utilized the INdoor CHEMical model in Python (INCHEM-Py), constrained by data from the HOMEChem campaign.
• Input data included concentrations of organic and inorganic compounds, and measured photolysis rates.
• Modelled concentrations of OH, hydroperoxyl radicals, and HONO were compared against measured values.

Main Results:

• Modelled peak concentrations of OH, hydroperoxyl radicals, and HONO were 30%, 10%, and 30% higher than observations, respectively.
• Determined rates for HONO formation during cooking and its subsequent loss and release from wet surfaces during cleaning.
• Predicted peak Cl atom concentrations of (0.75-2.3) × 10^5 atoms/cm^3 during cleaning, with high daily Cl atom reactivity (5000-9000 s^-1).
• OH reactivity increased significantly post-activity, reaching up to 160 s^-1, exceeding levels in polluted outdoor areas.

Conclusions:

• Household activities like cooking and cleaning substantially enhance the indoor atmosphere's oxidation capacity.
• The study quantifies the significant role of these activities in generating reactive species and increasing overall air reactivity.
• Findings underscore the importance of understanding indoor air chemistry for public health and environmental assessments.