摘要
三峡库区消落带坡地的自发农用较为常见,消落带的这种利用方式可能加剧养分流失并对库区水环境造成影响。通过对库区2011~2013年3个落干期消落带农用坡地的地表径流、壤中流中氮素形态与浓度进行定位监测,研究消落带农用坡地氮素流失特征及其环境效应。结果表明:常规施肥下,消落带农用坡地侵蚀模数为1 443 kg/(hm^2·a),落干期内坡地平均径流量为230 mm,径流系数为0.58,其中壤中流流量占总径流量的77%。历次降雨产流事件中常规施肥处理时,地表径流、壤中流中TN平均浓度分别是4.85±0.85、20.73±2.05 mg/L,落干期地表径流(泥沙)和壤中流的TN流失量分别为6.63±1.19、35.22±3.38 kg/hm^2,分别占当季施肥量的2.2%、11.7%。可见,随壤中流流失是三峡库区消落带农用坡地氮素流失的主要途径。与常规施肥处理相比,减量施肥处理使地表径流(泥沙)、壤中流TN流失通量分别显著降低了25%、48%,表明减少氮肥用量可以显著降低消落带农用带来的环境风险,建议消落带农用地氮肥进行减量施肥,使其既不影响作物产量,也显著降低氮流失。
The mechanisms of nitrogen（N） losses through runoff （both overland flow and interflow） represent a significant portion of the N biogeoehemical cycle have been well documented for purple soil in the Sichuan Basin. It is unclear, however, how nitrogenloss takes place in agricultural slop land in the zone of fluctuating water level in the Three Gorges reservoir region. Nutrient loss may be increased and bring a great impact on the water environment of the Three Gorges Reservoir area while slope lands in the water level fluetuation zone used by local farmers spontaneously. Nitrogenloss through runoff in hill slope cropland in the water level fluctuation zone is unclear without any in sitn monitoring. In this paper, we presented an in situ monitoring study of nitrogen losing forms, contents and fluxes via different pathways from slope land used for farming in the in the water level fluctuation zone during drawdown period through 2011 to 2013. The results showed that soil erosion modulus of slope land used for farming would be 1 443 kg· hm-2 · a-1, while average annual runoff is 229.7 mm with interflow accounting for 77% of the total runoff discharge. The average total nitrogen in water of overland flow and interflow was 4.85±0.85 mg · L-1, 20.73±2. 05 mg· L-1 , respectively. The annual total nitrogen loss via overland flow and interflow was 6.63±1. 19 and 35.22±3.38 kg · hm-2, respectively, accounting for 2.2% and 11.7% of applied N fertilizer. Nitrate loss via interflow is the dominant route of nitrogen loss from the slope cropland. Compared with conventional fertilization rate, the loadings of total nitrogen were significantly reduced by 25% and 48%, respectively, in the overland flow and interflow under N-reduction fertilization. This indicates that reducing nitrogen application rate may decrease significantly the environmental risk of N loss from the slope land used for farming in the water level fluctuation zone. The intensity of nitrogen loss on slope land cannot be neglected while the slope land for farming of water level fluctuating zone, which may have potential risk of water pollution in the reservoir area. Therefore, restoration the ecological barrier function of water level fluctuating zone plays an important role in protecting the water environment of the Three Gorges reservoir area, suggesting the measures of reducing nitrogen application rate.
出处
《长江流域资源与环境》
CAS
CSSCI
CSCD
北大核心
2017年第8期1159-1168,共10页
Resources and Environment in the Yangtze Basin
基金
国家自然科学基金重大项目(41430750)"三峡库区支流消落带土-水界面磷素流失过程与通量"
中国科学院STS项目(KFJ-SW-STS-175-02)"三峡库区生态清洁小流域建设技术体系试验示范"~~
关键词
三峡水库
消落带
地表径流
壤中流
氮负荷
减量施肥
Three Gorges Reservoir
water level fluctuation zone
overland flow
interflow
nitrogen loading
reducing fertilizer application
