柴河流域不同景观类型径流氮磷含量及其计量比变化特征

Variation of Concentrations and Stoichiometric Proportions of Nitrogen and Phosphorus in Runoff With Land Use in Chaihe Catchment

流域内不同景观类型控制着径流养分输移程度及其计量比,进而影响流域内不同生态系统的服务功能,因此养分含量及其生态化学计量成为评价流域生态过程及水体营养状态的重要手段。为了解滇池流域内柴河子流域不同景观类型径流氮磷含量及其计量比变化特征,在时空尺度上针对流域主要景观类型进行野外水质监测,结果显示:(1)该区域径流水体氮磷超标较为严重,溶解态氮与颗粒态磷是氮磷的主要存在形态,氮磷污染指标基本符合面源污染特征;(2)坝平地径流氮含量及磷矿区径流磷含量时间变异程度较高;整个流域内雨季初期径流氮含量空间变异较强,雨季中期磷空间变异较大;(3)根据径流水体营养物限制划分标准,坝平地与台地的径流整体处于磷限制状态,磷矿区及富磷区林地径流处于氮限制状态,而大棚区及柴河下游水体不受营养盐的限制。因此,柴河水体排入滇池后容易增加滇池富营养化的风险。

As land use is an important factor controlling outputs and stoichiometric proportions of soil nutrients in runoff from a catchment and hence affecting service functions of the various ecosystems within the catchment, determination of nutrient contents and their bio?stoichiometric proportions in runoff have become an important tool for evaluating ecological processes and waterbody nutrient status of the catchment. In order to follow variations of nitrogen and phosphorus concen?trations and their stoichiometric proportions in runoffs with type of landscape in the Chaihe Catchment of the Dianchi Lake, water qualities were monitored spatio?temporally in the landscapes dominant of the catchment. Results show that ( 1) the surface runoff waters in the catchment were all far beyond the criteria of the national standard for water environment quality in China in N and P concentrations, and the pollutants existed mainly in the form of dissolved nitrogen and particulate phosphate;( 2) nitrogen content in runoff in flatlands and phosphate content in runoff in the phosphorus mining areas var?ied quite sharply temporally, while nitrogen content in runoff did spatially in the early period of the wet season and phos?phorus content did in the mid?wet season;and ( 3) according to previous studies, in which N ∶ P < 7 and > 30 were set for grading of waterbodies in quality for limiting nutrients in runoff, the surface runoffs from flatlands and tablelands as a whole, were under the condition of phosphorus limitation and the surface runoff from the phosphate mining areas and forest?lands in phosphorus?rich areas were under the condition of nitrogen limitation, while the runoffs in the greenhouse regions and the lower reaches of the Chaihe River was under the condition of none?limitation. It is, therefore, concluded that the effluent of the Chaihe River flowing into the Dianchi Lake tends to intensify the eutrophication risk of the Dianchi Lake.