摘要
滨河湿地作为连接河流水体和陆地的一个功能过渡界面区,是河流生态系统与陆地生态系统进行物质、能量、信息交换的一个重要过渡带,也是保护河流水体的最后一道屏障,对水质净化和农业非点源污染控制起着非常重要的作用。以黄河湿地国家自然保护区孟津扣马段为研究对象,采取野外定位观测试验和稳定同位素示踪(人工富集15N源的同位素稀释法)相结合的方法,研究了滨河湿地土壤对农业非点源氮的持留作用、渗漏到地下水中的农业非点源氮和湿地不同植被对滞留在土壤中的农业非点源氮的吸收作用。结果显示:通过地表径流进入滨河湿地的农业非点源氮在3个实验样方的垂向和侧向都发生了渗漏。滨河湿地土壤对农业非点源氮的滞留作用主要发生在0—10cm,相当于一个过滤器的功能。3种受试植被土壤表层的滞留量为芦苇(0.045mg/g)>藨草(0.036mg/g)>水烛(0.032mg/g),分别占到土壤滞留氮的59.2%、56.3%和56.1%。滞留在土壤中的农业非点源氮污染存在一个相对较长的效应。滨河湿地特殊的氧化还原条件导致强烈的土壤微生物反硝化作用以及滨河湿地植被对氮素的吸收作用,使得0-10cm土层土壤外源氮变化速度最快,1个月后,滞留芦苇、水烛、藨草样方中15N下降了77.8%、68.8%和8.3%;3个月后,芦苇、藨草、水烛样方中的15N下降了93.3%、72.2%和37.5%。滨河湿地复杂的水文过程,使得滞留在土壤表层的农业非点源氮迁移转化更为复杂多变。监测数据显示,在实验设计的浓度和强度范围内农业非点源氮没有对地下水造成影响。不同植被和同一植物的不同生长时期对滞留在土壤中氮的吸收能力差别较大,吸收量依次为芦苇嫩芽(9.731mg/g)>老芦苇(4.939mg/g)>藨草(0.620mg/g)>水烛(0.186mg/g)。通过对生物量计算得出滨河湿地芦苇、水烛和藨草对农业非点源氮的吸收能力分别为氮吸收量96.11、3.76、0.32kg/hm2。可见,滨河湿地作为连接河流与陆地的缓冲带,通过截留、过滤、植物吸收等过程能有效的削减农业非点源氮对临近地表水体污染,对农业非点源氮污染控制起着非常重要的作用。合理的滨河湿地保护与利用模式对河流水环境保护具有重要的意义。
As a functional transition interface connecting rivers and lands,riparian wetlands are one of the major transition zones for matter,energy,and information transfer between aquatic and terrestrial ecosystems. It is also the last barrier to protect the water quality in rivers,and play an important role in water purification and non-point pollution control. With the combination of field experiments and isotope trace technique （ the 15N-enriched method） in Kouma section of the Yellow River,retention of agricultural non-point nitrogen pollution by the soil in riparian wetland,the proportion of agricultural non-point nitrogen which leaks into the groundwater,and the absorption of agricultural non-point sources nitrogen pollution by different vegetation types in riparian wetlands were investigated. The results showed that the agricultural non-point sources nitrogen flowing into riparian wetlands through surface runoff infiltrated into the subsurface and dispersed both vertically and horizontally in three experiment plots. Retention of agricultural non-point nitrogen pollution by the soil in riparian wetlands mainly occurred in the soil layer at top 0 -10 cm,and the amount of nitrogen retained by surface soil associated with three types of vegetation were 0. 045 mg/g for Phragmites communis Trin plots,0. 036 mg/g for Scirpus triqueter plots,and 0. 032mg/g for Typha angustifolia plots,which accounted for 59. 2% ,56. 3% ,and 56. 1% of the total nitrogen interception,respectively. The top soil layer （ 0 -10 cm） of riparian wetland acts as a filter. A long period pollution effect exists in agricultural non-point nitrogen that remained in the soil. Strong denitrification function of soil microorganisms in the extraordinary oxidation-reduction condition of riparian wetland and uptake by plant in riparian wetland make agricultural non-point nitrogen in the 0 -10 cm soil layer change more quickly than those in other layers. After K15 NO3 was added to the surface soil,nitrogen content decreased by 77. 8% for Phragmites communis Trin plots,68. 8% for Typa angustifolia plots,and 8. 3% for Scirpus triqueter plots within one month,respectively. Three months later,the nitrogen content decreased by 93. 3% for Phragmites communis Trin plots,72. 2% for Scirpus triqueter plots,and 37. 5% for Typa angustifolia plots,respectively. Due to complex hydrological processes in riparian wetlands,it is more complicated for agricultural non-point sources nitrogen remaining in the surface soil to transfer and transform. Monitoring data indicated that groundwater was not affected by agricultural non-point pollution at this experimental concentration through detention by the soil in riparian wetland. But one month later,15N atom percentage showed significant difference comparing with other time,and it is probably because of frequent exchange between groundwater and river water in the study area. Effects of agricultural non-point nitrogen pollution were significantly different among different vegetation communities. Effects of agricultural non-point nitrogen pollution were also significantly different among different growth stages of the same plant. The nitrogen uptake amount changed as follows：young shoots of Phragmites communis Trin plots （ 9. 731 mg/g） old Phragmites communis Trin plots （ 4. 939 mg/g） Scirpus triqueter plots （ 0. 620 mg/g） Typa angustifolia plots （ 0. 186 mg/g）. Harvesting of Phragmites communis Trin vegetation at midseason can promote its absorption for agricultural non-point nitrogen pollution. The nitrogen uptake amount of Phragmites communis Trin plots,Typa angustifolia plots,Scirpus triqueter plots were 96. 11kg/hm2,3. 76 kg/hm2,and 0. 32 kg/hm2,respectively. This study suggests that riparian wetlands play a key role for the control of agricultural non-point pollution. As the buffer connection between rivers and lands,the riparian wetland can effectively reduce the agricultural non-point nitrogen pollution through interception,filtration,plant uptake and other processes. The scientific protection and utilization of riparian wetland will be helpful to protect water environment in rivers.
出处
《生态学报》
CAS
CSCD
北大核心
2010年第21期5759-5768,共10页
Acta Ecologica Sinica
基金
教育部新世纪优秀人才支持计划项目(NCET-09-0120)
中国科学院城市与区域生态国家重点实验室开放基金(SKLURE2010-2-4)
国家自然科学基金项目(30570276)
河南省教育厅自然科学研究计划项目资助(2010B610006)
关键词
滨河湿地
植被样方
农业
非点源污染
氮污染
riparian wetland
vegetation plot
agriculture
non-point source
nitrogen
