A simulated experiment of repacked soil columns in flooding field condition was conducted to study dynamic leaching characteristics of nitrogen(N) and phosphorus(P) from paddy soil through irrigation with contaminated river water.The results showed that the N losses by leaching of different N forms had higher values in early flooding stage(usually in about seven days after flooding)

then decreasing.That indicated that the N in leachate might not come from irrigating river water but mostly from the paddy soil.In late flooding stage

the few leaching of NO-3-N and NH 4-N were observed except for dissolvable organic N (DON) that indicated DON might be main form of N leaching from paddy soil under contaminated irrigation.In addition

there were different results of the P leaching loss compared with N loss that few losses were observed in long period of time after flooding but a few found in late flooding stage

as the phenomena indicated the P absorbed by soil might have been up to saturation after a long-term flooding treatment with phosphorous sewage irrigation and soil could not hold in surplus P from outside input.