Pesticides are lost from soils in 

 five ways. One loss is due to volatili- 

 zation in areas of the coastal zone 

 where the surfaces are hot. The beach 

 or the black surface of the marsh is an 

 example of areas where volatilization is 

 a potentially significant loss. Chemical 

 decomposition is a second way of losing 

 pesticide. There are difficulties pre- 

 dicting these losses because we do not 

 know what happens to most types of pes- 

 ticides under the anaerobic conditions 

 of marshes. The bulk of the research 

 has been about agricultural soils where 

 the balance of water and oxygen favor 

 oxidation, not the reverse as in 

 marshes. Photodecomposition is a third 

 loss factor of significance. Photodecom- 

 position is significant in the case of 

 toxaphene. Durant and Reimold (1972) 

 postulated that ultraviolet light was 

 responsible for the degradation of tox- 

 aphene-contaminated dredge material 

 placed in a marsh. A fourth factor in- 

 fluencing loss of pesticides in soils is 

 microbial metabolism, and it, too, is 

 not well understood in many of the 

 coastal soils and ecosystems. Research 

 has usually been concerned about biolog- 

 ical metabolism in agricultural ecosys- 

 tems. Removal of pesticides by plants 

 is another form of loss which has not 

 been widely studied. We do not know 

 that Spartina will pick up toxaphene and 

 translocate it (Gallagher et al. 1979). 

 The residence time of these chemicals in 

 soil varies greatly and is influenced by 

 many factors. DDT has a half life be- 

 tween 3 and 30 yr, chlorodane about 

 8 yr, and heptachlor 2 to 4 yr. Toxa- 

 phene has been measured to have an 11-yr 

 half life in some agricultural soils. 

 Gallagher and Wolf (in press) used up- 

 take by Spartina as an indicator of the 

 presence of toxaphene in the soil and 

 found tissue levels to be near zero 

 after only 7 mo without additions. 

 We collected soil samples from 

 Terry Creek area where we know that they 

 had been exposed to toxaphene for many 

 years. We sectioned the samples and 

 measured the toxaphene levels in the 

 mud. After separating the mud from the 

 macro-organic material (that not passing 

 a 1-mm sieve), we measured the toxaphene 

 in fractions. We found approximately 

 400 rng/mMn the macro-organic matter in 

 the creekbank soils and 150 mg/m2 in the 



mud. In the high marsh far away from the 

 creek, there was very little toxaphene 

 (less than 20 mg/m2)in either the macro- 

 organic matter or mud (Gallagher et al. 

 1979). 



Organisms do not spend their lives 

 in the whole organic or mud zone; they 

 are often localized in specific areas. 

 To evaluate specific micro-habitats, we 

 collected cores of the marsh and dis- 

 sected them. The shoots were cut and we 

 separated the live roots and rhizomes 

 from the bulk of the mud. All the soil 

 that stuck to the live roots we called 

 rhizosphere soil. The soil that stuck 

 to the roots was influenced by the 

 roots, as were the microbes present in 

 that soil. The dead roots had the high- 

 est toxaphene levels, the dead material 

 next, and the live materials were much 

 lower. All material associated with 

 organic matter had higher concentrations 

 than the mud (Gallagher et al. 1979). 

 The dead roots probably had more toxa- 

 phene in them for one of two reasons: 

 1) either they had a lot of cracks in 

 the surface and the material is absorbed 

 or adsorbed, or 2) the organic material 

 in the roots is more easily degraded by 

 microbes than the toxaphene; therefore, 

 it becomes enriched as the vegetation 

 rots away. 



The examination of a few actual 

 cases of pesticide-marsh flora interac- 

 tions and several hypothetical cases has 

 pointed out the complexities of the 

 problem of pesticides in the wetlands. 

 Basic knowledge of wetland processes 

 will aid in theorizing the fate and 

 trophic transfer in the various food 

 chain modules. Once these are identi- 

 fied, they must be tested with various 

 pesticides. If it is determined that 

 potentially serious problems exist in 

 situations where wetlands are the target 

 ecosystems, they can be avoided by 

 changing the management practice. The 

 uncontrolled situation is that where the 

 wetland is a nontarget ecosystem. Meth- 

 ods of ameliorating such interaction 

 should receive research priority. 



Literature Cited 



Durant, C. J. and R. J. Reimold. 1972. 

 Effects of estuarine dredging of 

 toxaphene-contaminated sediments in 



138 



