为了研究地表水与地下水不同补给关系下硝酸盐氮在傍河农田的迁移规律,选取大沽河河床沙样作为沙槽试验介质,设计地表水与地下水相互补给装置,模拟无补给、地表水补给地下水和地下水补给地表水3种方式下硝酸盐氮在土壤中的迁移,通过测定各取样点硝酸盐氮含量和到达时间,分析了其迁移规律。结果 表明:纯淋洗实验中,淋洗强度与沙样颗粒越小,硝酸盐氮在表层沙中的累积越明显,硝酸盐氮的迁移也越慢。地表水与地下水相互补给试验中,补给水位上升,硝酸盐氮的积累量增加、迁移到饱水带的时间缩短; 补给水力坡度为0.5时,硝酸盐氮在细沙饱水带中迁移速度约为5.3 cm/min; 水力坡度变为0.7时,迁移速度约为9.4 cm/min; 补给水力坡度为0.5时,硝酸盐氮在中沙饱水带的迁移速度约为12.3 cm/min。硝酸盐氮在包气带中的积累量随着沙层深度的增加而减少; 淋洗强度、水力坡度及沙样颗粒越大,硝酸盐氮在包气带和饱水带中的迁移速度越快; 补给水位越高,硝酸盐氮迁移至饱水带的时间越短。
This research aimed to study the migration pattern of nitrate nitrogen in farmland next to rivers under different recharge relations between surface water and groundwater. Sand samples from riverbeds at different locations on the Dagu River were used as sand tank experimental media. Surface water and groundwater complementary feeding devices were designed to simulate leaching of nitrate nitrogen in the soil in three ways: no recharge, surface water recharge, and groundwater recharge, migration of nitrate nitrogen was determined by measuring the nitrate nitrogen content and the arrival time at each sampling point. The results show that: in the pure leaching experiment, the smaller the leaching intensity and sand-like particles, the more obvious the accumulation of nitrate nitrogen in the surface sand, and the slower the migration of nitrate nitrogen; in the experiment of supplementary surface water and groundwater, the supply water level increased, the accumulation of nitrate nitrogen increased, and the time of nitrate migration to the saturated zone was shortened; when the supply hydraulic gradient is 0.5, the speed of nitrate nitrogen migrates in the fine sand saturated zone is about 5.3 cm/min; when the hydraulic gradient becomes 0.7, the speed of nitrate migration is about 9.4 cm/min; when the recharge hydraulic gradient is 0.5, the nitrate nitrogen migration speed is about 12.3 cm/min. The accumulation of nitrate nitrogen in the unsaturated zone decreases with the increase of the sand depth. The greater the leaching intensity, hydraulic slope and sand-like particles, the faster the migration speed of nitrate nitrogen in the unsaturated zone and saturated zone; the higher the recharge water level, the shorter the time for nitrate nitrogen to migrate to the saturated zone.
