Effects of exposure time and co-existing organic compounds on uptake of atrazine from nutrient solution by rice seedlings (Oryza sativa L.)

Root uptake of atrazine (ATR) by rice seedlings (Oryza sativa L.) from nutrient solution was investigated with exposure periods of 48, 96, and 240 h. A similar ATR uptake was carried out with two co-existing organic compounds (o-chlorophenol (CP) and 2,4-dichlorophenol (DCP)) with 48 h exposure. In contact with the seedlings, the ATR level in nutrient solution decreased sharply during the early exposure and then reached relatively steady levels after 48 h. It was observed that the ATR levels within whole seedlings approached the estimated equilibrium partition limits in about 48 h, according to the partition-limited model utilizing the measured plant water and organic matter contents and the ATR partition coefficients with whole seedlings. However, when roots and shoots were consisted separately, the detected ATR levels in roots were lower than estimated equilibrium limit while the levels in shoots exceeded the equilibrium limit. The data with roots suggested the occurrence of rapid ATR degradation in roots. The results with shoots are intrinsically consistent with the suggested complex formation of ATR with free metal ions in shoots. The ATR levels in roots and shoots varied to a moderate extent when the seedlings were exposed to different levels of ATR-CP-DCP mixtures. The variation results presumably from the interference of coexisting CP and DCP and the phytotoxicity of the mixed chemicals.