| Popis: |
Concentrations of four halogenated hydrocarbons, used commercially as solvents, were measured throughout the air over the Los Angeles Basin during three days in the Fall of 1972. Average concentrations were found to be 1.25 ppb for tetrachloroethylene, 0.65 ppb for trichloro-fluoromethane, 0.37 ppb for 1,1,1-trichloroethane and 0.22 ppb for carbon tetrachloride. Carbon tetrachloride showed the least variation in concentration throughout the entire basin with more than 86 per cent of all measurements falling within the range 0.1–0.3 ppb. Generally, there was a progressive decrease in the concentrations of all four compounds on moving from the in-land valleys to the coast. Diurnal studies at ground level locations and vertical profile measurements indicate that the adventitious labeling of the Los Angeles air mass with 1,1,1-trichloroethane, (C 2 H 3 Cl 3 ) and tetrachloroethylene (C 2 C1 4 ) may allow these compounds to trace the movement of air within and away from the Los Angeles Basin. |
