Fate of spilled xylene as influenced by soil moisture content

Abstract

Barrel size undisturbed monoliths of Weswood silt loam soil (Fluventic Ustochrept) were collected, instrumented, equilibrated at desired moisture contents, and treated with xylene by spilling it on the soil surface. Volatilization of xylene was measured using a chamber equipped with a granular activated carbon (GAC) vapor trap. Leachate was collected daily under − 33 kPa tension with a GAC vapor trap between each collection bottle and the vacuum source. Residual xylene was determined by collecting soil samples at the end of the leaching period and analyzing them for xylene. Degradation was estimated as the xylene applied less the sum of the xylene which remained, leached, and volatilized. Most of the observed volatilization occurred immediately after application and was greatest from the driest soil. An application rate of 7.2 × 10−2 m depth of xylene at the intermediate moisture content resulted in four times more volatilization than occurred from the 3.6 × 10−2 m application. Xylene appeared in the leachate collected at a depth of 0.78 m from all treatments within 12 hr after the xylene was applied. Initial soil moisture content greatly influenced the amount which passed through the soil. An average of 34% and less than 0.5% of the applied xylene moved through the wettest and driest soils, respectively. Doubling the xylene application depth resulted in a 10 to 17-fold increase in the amount of xylene in the leachate. Vapor traps in line with soil pore liquid samplers were essential, since for some treatments, an average of 95.1% of the xylene collected in the leachate was recovered from the vapor trap. The xylene which remained in the soil after 67 days ranged from 6.7 to 12.8%. Estimated degradation rates ranged from 45.7 to 137.8 g day−1 with the greatest degradation occurring in the soil with the highest application rate and the least degradation in the wettest soil with the lowest application rate.