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地形和植被会改变水分在土壤中的运移,进而影响土壤中硝态氮(NO_3~--N)的分布,并可能导致对水体污染的差异.在黄土高塬沟壑区黑河流域选取3个样点,采集刺槐林和草地在不同坡位(上、中和下坡位)的6 m深土样,分析了坡位和植被对NO_3~--N迁移的影响,并初步评估了其对地表水及地下水污染的潜在风险.不同坡位及植被条件下,土壤中硝态氮均没有出现累积,在表层土壤达到最大值后逐渐减小.2种植被下NO_3~--N达到稳定时的深度约为200 cm,稳定浓度均为下坡位>上坡位>中坡位,但在同一坡位的稳定浓度均有草地高于刺槐林的特点,说明坡位及植被覆盖类型均会影响NO_3~--N在土壤中的分布.整个流域地表水NO-3含量枯水期及汛期分别为(6.90±2.10)mg·L~(-1)和(5.84±2.86)mg·L~(-1),而坡地表层土壤(0~20 cm)中可移动态NO_3~-为(29.55±6.59)mg·L~(-1),明显大于地表水中的浓度,很有可能随径流流失造成地表水氮素污染.地下水枯水期和汛期的NO_3~-含量分别为(24.61±23.72)mg·L~(-1)和(15.70±10.78)mg·L~(-1),而坡地深层土壤(>200 cm)中NO-3为(0.78±0.16)mg·L~(-1),由于浓度较低,对地下水造成污染的可能性较小.
Topography and vegetation will change the migration of water in the soil, and then affect the distribution of nitrate nitrogen (NO_3 ~ - N) in the soil, and may lead to the difference of water pollution.Selecting three in the Heihe River Basin in the gully region of the Loess Plateau Samples were collected from 6 m deep soil samples of Robinia pseudoacacia forest and grassland at different slope positions (upper, middle and downhill), and the effects of slope position and vegetation on the migration of NO 3 - -N were analyzed. Surface water and groundwater pollution.Under different slope positions and vegetation conditions, nitrate nitrogen did not accumulate in the soil, but decreased gradually when the surface soil reached the maximum value.When the NO_3 ~ - N under the two kinds of vegetation reached a steady state The depth was about 200 cm, and the stable concentrations were in the downhill> uphill> mid-slope. However, the stable concentrations in the same slope were higher in the grassland than in the Robinia pseudoacacia forest, indicating that both the slope position and the vegetation cover type would The content of NO_3 ~ -N in the soil was affected by (6.90 ± 2.10) mg · L ~ (-1) and (5.84 ± 2.86) mg · L ~ (- (29.55 ± 6.59) mg · L -1, which is obviously higher than that in surface water, and is likely to change with runoff The soil NO3 (superscript +) pollution of surface water was lost, the NO3 - content of groundwater in dry season and flood season were (24.61 ± 23.72) mg · L -1 and (15.70 ± 10.78) mg · L -1, respectively, NO-3 in the soil (> 200 cm) was (0.78 ± 0.16) mg · L -1, which was less likely to pollute the groundwater due to its lower concentration.