Gas/Solid Partitioning of Semivolatile Organic Compounds to Model Atmospheric Solid Surfaces as a Function of Relative Humidity. 1. Clean Quartz

摘要

Evaluating the relative importance of adsorption to particle surfaces vs adsorption into organic material in particles for gas/particle partitioning in the atmosphere requires a comparison of relevant gas/solid partitioning constants with field-determined values. Gas/ quartz partitioning constants K_p (m~3/μg) were measured at 20℃ for clean quartz as a function of relative humidity (RH) for 11 semivolatile polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. Increasing RH from ～30 to ～70% caused the K_p values to decrease by a factor of 10. With adsorption to the quartz surface as the only possible sorption mechanism, surface-area-normalized partition constants (K_(p,s), m~3/m~2) were calculated. For quartz, correlations of log K_(p,s) with the log of the vapor pressure were found to lie significantly below the corresponding lines for urban paniculate matter. We conclude that adsorption to mineral/oxide surfaces like clean quartz is not important in determining K_p values in urban air; such sorption may be important in rural/remote environments.