Environmental fate of phenanthrene in lysimeter planted with wheat and rice in rotation

An outdoor lysimeter experiment was conducted to investigate the fate of 14C-labeled phenanthrene in the soil planted with wheat and rice in rotation. Results showed that applied 14C-activity in the soil decreased mainly through gaseous losses; 67.5% of it evaporated as 14CO2. After the rice harvest, the surface soil retained 21.7% of applied 14C-activity, of which 92.4% remained in nonextractable soil residues. The 14C-activities found in deeper layers of the soil column indicated vertical migration of phenanthrene or metabolites. Furthermore, the 14C-activities detected in five organs of mature wheat or rice decreased in the order: roots > leaves > shells > stems > grains. The vertical migration and its accumulation by grains suggest that PAHs in field have adverse effects on the security of groundwater and food.