Laboratory experiments of phosphorus loss with surface runoff during simulated rainfall

Surface runoff accounts for much of the phos- phorus (P) input to and accelerated eutrophication of the fresh waters. The environmental fate of P receives increasing attention but the key mechanisms of P transport with surface runoff remain unclear. Through artificial rainfall experiments, characteristics of P loss with surface runoff during simulated rainfall are investigated under the conditions of various slope gradient and rainfall intensity and the factors of influencing are also discussed. Results show that the amount of runoff and sediment increased rapidly in a shorter time after runoff producing, then gradually turned to be stable. It shows significant correla- tion between the runoff volume and sediment. The amount of runoff and sediment increased with the increasing of slope gradient and rainfall intensity. P content in the runoff was higher in the early stage after runoff producing, and then stabilized gradually. Most of the P transformed through the sediment loss.