# Phtyoremediation and Bioremediation of Pesticide-Contaminated Soil
## 7 Remediation of Pesticides
### In Situ Bioremediation and Phtoremediation  
There has been significant progress in developing in situ bioremediation for pesticides [25; 86; 87; 88; 89; 92; 111; 112; 134; 151; 154; 159; 162; 180; 181; 182; 185; 188; 202; 204; 206; 244; 277; 283; 284; 286].  
These methods fall into three general categories; phytoremediation, bioremediation by indigenous organisms and bioaugmentation. Vegetation has been beneficial in the bioremediation of pesticides in many locations for many different pesticides [1; 22; 26; 38; 44; 45; 50; 54; 79; 81; 83; 85; 111; 122; 147; 148; 152; 171; 175; 176; 180; 221; 244; 253; 283; 284; 254; 255; 283; 285; 13; 286; 256; 257; 283; 287; 288; 171; 175; 176; 180; 221; 244; 253; 283; 284]. With vegetation present in the contaminated soil, degradation of the pesticide near the roots is supported by substrates coming from the roots that enhance microbial growth and the magnitude of the active microbial population [22; 187; 207]. Bacteria and fungi in the root zone provide beneficial genes and play important roles in the biodegradation of pesticides [206; 218]. Some pesticides are taken up into the plant and transformed by plant enzymes. The octanol/water partition coefficient of the pesticide is important in phytoremediation because it affects the solubility of the pesticide in water, the uptake into plants, and the distribution of the pesticide in the soil and in the plant [13; 124; 180; 193; 256]; see [PERSON] et al. for values of the octanol/water partition coefficient for pesticides [291]. Biodegradation of pesticides by endophytic bacteria associated with plants is important in many biodegradation processes. Listings of plants that take up pesticides and the pesticides that have been reported to be transformed by plant enzymes are available [111; 152; 283]. The process of establishing vegetation and nurturing growth is inexpensive compared to many of the other remediation processes. It can be applied at field scale [88; 113; 160; 164; 165; 184; 210]. The vegetation reduces wind-blown dust and the movement of the pesticides from the site [156]. [PERSON] et al. [169; 173; 174] have provided a list of 17 pesticide-tolerant plants that grew in soils where high pesticide concentrations were present. The growth of plants in contaminated field soil often improves soil quality by increasing microbial populations and organism diversity, and by adding organic matter to the soil [10; 26; 53; 189; 190]. The common results after phytoremediation of contaminated soil are that pesticide concentrations in soil are reduced and pesticide concentrations in roots are less than the concentrations in the soil, but larger than the concentrations in the stems and leaves of the plants [4; 156].  
There have been several efforts to develop transgenic plants for phytoremediation of pesticide-contaminated soils [284]. The process that plants use may involve 1) addition of a reactive group such as OH to the pesticide, 2) conjugation of another compound to the pesticide through reaction with the reactive group, and 3) integration of the conjugated pesticide into cell-wall components or another part of the plant where the new substance is less toxic [236; 283; 284]. Atrazine degradation with transgenic plants has been reviewed by [PERSON] et al. [284].  
Endophytes with biodegradation ability can be added to the site to assist the plant with phytoremediation [284; 288]. Genetic modification of endophytic bacteria is one pathway to develop the successful pesticide degradation by a plant, aided by bacteria associated with the plant. Endophytic bacteria may survive better than soil bacteria in field applications [283; 288]. In phytoremediation, biodegradation in the rhizosphere and the plant are both important.