Response of vegetation to volatile pollutants: a delivery system for controlled, quantifiable chronic exposure of foliage

Little is known about air-to-foliage transfer of volatile (organic pollutants: sink strength of leaves and toxicity to the plant via this route have not been widely documented). An exposure system that is capable of repeatedly delivering a range of concentrations of volatilized organic pollutant to foliage under optimal growth and activity conditions is needed. Using naphthalene (a polycyclic aromatic hydrocarbon) as a model contaminant, a steady-state exposure system was developed in which a continuous stream of naphthalene vapor was generated from a chilled permeation tube. This stream was proportionately released into tour separate clean airstreams to deliver four discrete concentrations of naphthalene vapor to large cuvettes in which potted plants were sealed. Each cuvette received a total flow rate of 5 L/min. Naphthalene concentration exiting the permeation tube was calculated twofold: using ideal gas laws and from the daily mass loss of the permeation tube. Daily mass loss from the permeation tube and indirect indication of naphthalene concentration by UV light attenuation indicated that the exposure system was capable of maintaining a logarithmic range of naphthalene vapor concentrations over 4 d. Deviation from predicted concentrations was associated with high moisture content of the air supply line used to vent the permeation tube