Rule of the Nitrate Transport in Main Soils in Fengqu Region

Groundwater pollution by nitrate-N is one of the most significantenvironmental problems in the agricultural fields. Intensification of the agricultural practices and excessive use of nitrogen fertilizers are the main reasonsfor nitrate contamination of the groundwater. Nitrate concentration levels in the groundwater usually reach or exceed the water quality criteria (10 mg·L-1). In this paper, through using the simulating soil column indoor, the nitrate vertical transport rules in farmland soils in Fengqu region were studied. The results showed that under saturated condition, there were spatial differences in the form of the breakthrough curves (BTCs) of nitrate vertical transport in yellowfluvo-aquic and aeolian sandy soils. The effluent times of nitrate in aeoliansandy soil and topsoil layer in yellow fluvo-aquic soil were early, and the times that input nitrate all leached out of the soil column were short, and the peak values of BTCs were high, but the changes of BTCs of 30～60 cm soil layer in yellow fluvo-aquic soil were adverse: the IMG SRC=IMAGE/03230103.JPG HEIGHT=11 WIDTH=19longer effluent times of nitrate removing out of soil column were, the more plain and the lower peak values of the BTCs were. Accompanying ion had no obvious effect on BTCs in aeolian sandy soil and topsoil layer in yellow fluvo-aquic soil, but maybe made effluent times of nitrate ahead. Under unsaturated condition, the peak values of the BTCs of nitrate transport in aeolian sandy and yellow fluvo-aquic soils were much lower. The duration of the transport was affected greatly by the flutes of nitrate. The asymmetry distribution and tailing phenomenon of BTCs were more distinct under the lower rates of nitrate input. The contents of nitrate in studied soils showed regular changes with the seasons, higher in winter and spring than in summer and autumn.