Volatilization from water estimation described

The recommended error estimation methods for high volatility compounds from the reference are reviewed in this section of the report after describing the test protocol procedures. A Monte Carlo simulation of experimental results was then performed followed by statistical analyses to determine the distribution and amount of error associated with estimation of volatilization from water for a high volatility compound. 

It has been argued that the Kqa values can be used as a unifying property for describing volatilization of POPs from soils and sorption to aerosols. The limited experimentally obtained values typically are supplemented by estimates from octanol-water and air-water partition coefficients. The value of condensation temperature lies in its ability to estimate sorption of atmospheric contaminants to aerosols (Bidleman, 1988). At Tc, the chemical is equally partitioned between the gas phase and aerosols. Since POPs exist in the atmosphere both as gases (vapor phase), and in condensed form adsorbed to aerosol particles, the characteristic temperature of... 

Based on information from these sources, scientists estimate that the nucleus of a comet consists of about 42 percent volatile compounds (about 80 percent of which is water) and 58 percent solid particles, generally described as "dust." About 45 percent of this nuclear dust is similar in chemical composition to the carbonaceous chondrites found in meteorites that is, they are primarily silicate in composition. (Carbonaceous chondrites are discussed at greater length in the next section.) Another 40 percent of the nuclear dust is organic in nature, that is, composed of carbon compounds of varying degrees of complexity. The final 15 percent of nuclear dust is composed of very small particles with masses of only a few atto-grams (10 l8g). 

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