problem was especially prominent in citrus seed beds, where plants appeared chlorotic and

stunted (Tucker and Anderson, 1972). Another reason for unfavorable growth response in some

plants to methyl bromide fumigation is the accumulation of bromide ions in soil (Gentle et al.,

1989). Accumulation of these ions can often be corrected by leaching via irrigation.


Methyl Bromide as a Potential Contributor to Ozone Depletion

 The ozone is a layer of atmosphere located approximately 9-21 miles from the surface

of the earth. This layer is important in reflecting ultraviolet rays and reducing the loss of heat

from the earth (Villee et al., 1989). There are several chemicals that have been implicated in

the possible destruction of ozone, one of which is methyl bromide.

 There is considerable uncertainty and controversy associated with the identification of

 sources of atmospheric bromine compounds. There are several reasons for uncertainty

 associated with estimates derived from the calculations of atmospheric bromine compounds,

 including the calibration of measurements, identification of sources and sinks, and the inter-

 relationship between removal of atmospheric methyl bromide and contributions from known and

 unknown sources (Watson and Albritton, 1991a).

 Both natural and anthropogenic sources have been implicated as significant contributors

 of methyl bromide in the atmosphere. The contributions of various sources of methyl bromide

 to total atmospheric concentrations have not been clearly characterized, however, anthropogenic

 sources have been implicated (Watson and Albritton, 1991a). Based on recent estimates,

 approximately half of the total methyl bromide used for soil fumigation is thought to find its way

 into the upper atmosphere. This equates to an estimated 30,000 metric tons per year

 (Chemically Speaking, 1992b). Methyl bromide is also produced by natural means, and there