Peter M. Jeffers

Green plants: A terrestrial sink for atmospheric CH3Br

Methyl bromide is reactively removed from air by the foliage of all 9 herbaceous, 18 deciduous, and 12 coniferous plants we have tested, in a process that appears enzymatic. Excised plant leaves yielded removal rates directly proportional to leaf surface area and first-order in CH3Br concentration from 10 ppmv to 500 pptv, the current limit of our experimental technique. Observed rate constants for different plants vary within a factor of about 100 with a lower value of 1×10−3 hr−1cm−2 in systems where the rate is not diffusion limited. This sink for atmospheric CH3Br could be significant in calculations of the global methyl bromide budget.

Sterilization of Plants for Phytoremediation Studies by Bleach Treatment

ABSTRACT Bleach treatment of plants was studied as a simple alternative to axenic tissue cultures for demonstrating phytodegradation of aqueous and gas-phase environmental contaminants. Parrotfeather (Myriophyllum aquaticum), spinach (Spinacia oleracea), and wheat (Triticum aestivum) were exposed to 0.525% NaC10 solutions for 15 s, then rinsed in deionized water. Plate counts indicated that 97 to 100% of viable bacteria were removed from parrotfeather and spinach. Transformation rates for 2,4,6-trinitrotoluene (TNT) by bleached and untreated parrotfeather were virtually identical. Similarly, treated and untreated spinach, wheat heads, and wheat leaves removed methyl bromide (MeBr) from air at the same rates. However, wheat root with attendant adhering soil was rendered inactive by bleach treatment. Parrotfeather roots examined by dissecting microscope and by electron microscope showed no significant damage caused by bleach treatment.

vv pumping in H2: estimate of induced dissociation at 300°K

By means of the stimulated Raman effect one may produce in H2, D2, and in several other gases, a substantial population in the ν = 1 state. Subsequent to the pulse excitation vv energy transfers rapidly generate a vibrational distribution which is approximately equivalent to (3–4) × 103°K. Then, in H2 + D2 mixtures metathetic reactions occur. Here we report on a computer simulation of an experiment described elsewhere, designed to estimate whether a measurable fraction of the hydrogen molecules reach the upper vibrational level and dissociate. Solutions of the coupled differential equations show that the anticipated hydrogen atom concentrations are too low by a factor of 107-108 to account for the observed H/D exchanges. These calculations also show that the conventional phenomenological rate equation for dissociation does not apply to this highly non-thermal distribution.