Surface Emissions Modulate Indoor SVOC Concentrations through Volatility-Dependent Partitioning

Abstract

Measurements by semivolatile thermal desorption aerosol gas chromatography (SV-TAG) were used to investigate how semivolatile organic compounds (SVOCs) partition among indoor reservoirs in (1) a manufactured test house under controlled conditions (HOMEChem campaign) and (2) a single-family residence when vacant (H2 campaign). Data for phthalate diesters and siloxanes suggest that volatility-dependent partitioning processes modulate airborne SVOC concentrations through interactions with surface-laden condensed-phase reservoirs. Airborne concentrations of SVOCs with vapor pressures in the range of C13 to C23 alkanes correlated with indoor air temperature. Observed temperature dependencies were quantitatively similar to theoretical predictions that assumed a surface-air boundary layer with equilibrium partitioning maintained at the air-surface interface. Airborne concentrations of SVOCs with vapor pressures corresponding to C25 to C31 alkanes correlated with airborne particle mass concentration. For SVOCs with higher vapor pressures, which are expected to be predominantly gaseous, correlations with particle mass concentration were weak or nonexistent. During primary particle emission events, enhanced gas-phase emissions from condensed-phase reservoirs partition to airborne particles, contributing substantially to organic particulate matter. An emission event related to oven-usage was inferred to deposit siloxanes in condensed-phase reservoirs throughout the house, leading to the possibility of reemission during subsequent periods with high particle loading.

Fates and spatial variations of accumulation mode particles in a multi-zone indoor environment during the HOMEChem campaign

“…Particle concentration and composition both inuence gas-phase uptake onto particles. 55,56 Observed gradients indicate that this concentration-dependent partitioning process will occur differently throughout the house during cooking periods. For example, the uptake coefficient of dinitrogen pentoxide (N 2 O 5 )which has been detected in indoor environments during cooking 57 is inversely proportional to the available particle surface area.…”

How Do Indoor Environments Affect Air Pollution Exposure?

“…11,12 Another chemical transformation that occurs with outdoor-to-indoor transport is the shift in the abundance and composition of semivolatile organic compounds (SVOCs) sorbed to airborne particles. [13][14][15][16][17][18] Certain SVOCs that are prominent in outdoor air, such as polycyclic aromatic hydrocarbons (PAHs), can desorb from outdoor particles transported indoors. 19 Other SVOCs, which are prominent indoors, can sorb to particles that are transported into buildings.…”

“…20 Under conditions with minimal indoor particle emissions, particles of outdoor origin have been shown to quickly sorb indoor SVOCs, 16 resulting in larger mass fractions of particulate SVOCs indoors than outdoors. 17 In summary, several features of indoor environments result in physical and chemical transformations such that indoor particles of outdoor origin differ meaningfully in size distribution and chemical composition from their outdoor precursors. Such changes might well influence the health consequences associated with inhaling them.…”

“…Phthalates are a prime example. 17 Human exposures to semivolatile organic compounds are dominated by indoor environments both through inhalation and dermal uptake. 84,85 Diseases believed to be influenced by environmental exposures to endocrine disrupting chemicals have increased over time, including asthma, allergy, Alzheimer's disease, psychogenic processes, eating disorders, chronic obesity, and possibly autism.…”

Frequency of use of household products containing VOCs and indoor atmospheric concentrations in homes

“…Heterogeneous surface chemistry is an emerging topic in indoor chemistry and is covered in the recent literature. [43][44][45] SOA production is driven predominantly by the oxidants OH and O 3 . 46 Though indoor data on these species were not collected in this study, it is likely that species with a short indoor residence time will be affected by different oxidant concentrations between seasons.…”