土壤优先水流及溶质优先迁移的研究

通过土壤原状土柱和填充土柱实验，研究了土壤优先水流的特征和非吸附性离子Br^-和NO3^-在土壤中的优先迁移。结果表明，土壤优先水流存在优先穿透、穿透曲线不对称性、偶向入渗和拖尾等特征，原状土柱中Br^-标记的优先水流在实验开始后24h出现穿透，穿透时的孔隙体积仅0.04，在原状土柱中以Br^-标记的土壤优先水流占土壤出流总量的26％，所引起的Br^-累积淋出量占总淋出量的86.7％，说明土壤优先水流虽只占出流总量较小的比例,却可造成较大比例的溶质迁移，优先水流可使NO3^－快速向下迁移，在仅1倍孔隙体积时，其出流中可收获投加量的11％，优先水流可使Br^-和NO3^-向土壤较深层次迁移的同时，发生径向扩散。

Preferential flow and its effect on solute migration in soil

The characteristics of soil preferential flow and the preferential migrate in soil for non absorptive bromide and nitrate ions were studied.With undisturbed and packed soil columns,the results showed that soil preferential flow was characterized with preferential breakthrough,non symmetric breakthrough curve,lateral infiltration,tailing and so on.The preferential breakthrough for Br - was 24 hours after it was applied,and the leachate volume was only 0.04 times asmuch as the pore volumes.The preferential flow for Br - accounted for 26% of total flux in the undisturbed soil columns.But the accumulative leachate mass for Br - resulted from the preferential flow were 86.7% of total accumulative leachate mass,showing that the soil preferential flow accounted for relative small ratio of the flux,but caused re lative much more solute transference.NO - 3 was moved down rapidly by preferential flow at only one time as large as pore volumes,and got 11% of the applied amount,respectively.As a result of the preferential flow,the lateral infiltration flow enabled Br - and NO - 3 rapidly distribute and diffuse into the deeper soil.