HYCREST CRESTED WHEATGRASS ACCELERATES THE DEGRADATION OF PENTACHLOROPHENOL IN SOIL

We investigated the effects of vegetation on the fate of pentachloroph enol (PCP) in soil using a novel high-how sealed test system. Pentachl orophenol has been widely used as a wood preservative, and this highly toxic biocide contaminates soil and ground water at many sites. Altho ugh plants are known to accelerate the rates of degradation of certain soil contaminants, this approach has not been thoroughly investigated for PCP. The fate of [C-14]PCP, added to soil at a concentration of 1 00 mg/kg, was compared in three unplanted and three planted systems. T he plant used was Hycrest, a perennial, drought-tolerant cultivar of c rested wheatgrass [Agropyron desertorum (Fischer ex Link) Schultes]. T he flow-through test system allowed us to maintain a budget for C-14-l abel as well as monitor mineralization (breakdown to (CO2)-C-14) and v olatilization of the test compound in a 155-d trial. In the unplanted systems, an average of 88% of the total radiolabel remained in the soi l and leachate and only 6% was mineralized. In the planted systems, 33 % of the radiolabel remained in the soil plus leachate, 22% was minera lized, and 36% was associated with plant tissue (21% with the root fra ction and 15% with shoots). Mineralization rates were 23.1 mg PCP mine ralized kg(-1) soil in 20 wk in the planted system, and for the unplan ted system 6.6 mg PCP kg(-1) soil for the same time period. Similar am ounts of volatile organic material were generated in the two systems ( 1.5%). Results indicated that establishing crested wheatgrass on PCP-c ontaminated surface soils may accelerate the removal of the contaminan t.