环境检测与评价；技术开发及推广服务；大气污染治理；固体废物污染治理；城市生活污水治理；水污染治理；生态修复工程；社会经济咨询；环境技术咨询；会务服务；汽车租赁。
Reeds widely grow in the arid and semi-arid regions in northwest China， can remove nitrogen and phosphorus in water bodies. In the recent years， it has not been well understood how dual fluctuations of salinity and water level in the arid and semi-arid regions affect removal of nitrogen and phosphorus by reeds， thus the best control measures for removal of nitrogen and phosphorus by reeds are different to set up under dual fluctuations of salinity and water level. Three different gradients of both salinity and water level fluctuations were set up， the effect of dual fluctuations of water and salinity on removal of nitrogen and phosphorus by reeds were analyzed by experiment. The results showed that: （1） Increase of salinity with low frequency was beneficial to removal of total nitrogen， total phosphorus and ammonia nitrogen， while increase of salinity with high frequency was unfavorable to them. The decline of water level was conducive to removal of ammonia nitrogen， the rise of water level with low frequency is conducive to removal of total nitrogen， while the rise of water level with high frequency inhibited removal of ammonia nitrogen and total nitrogen， mainly because it reduced dissolved oxygen of water. （2） The fluctuations of water level and salinity in Shahu Lake both led to increase of reed root lengths， indicating that the actual water recharge processes did not affect the survival of reed. （3） Although increase of water level with high frequency and decline of salinity promote uptake of nitrogen and phosphorus by reeds， however， they were not the best conditions for nitrogen and phosphorus removal in water bodies， because the direct uptake by reeds is not the dominant process of nitrogen and phosphorus removal. The regulation of water level and salinity should give priority to the appropriate conditions for microbial growth in order to ensure good water quality. （4） The results of AMOS structural equation modeling and two factor analysis of variance showed that dual fluctuations of water level and salinity directly affected the reed biomass， indirectly affected the concentrations of nitrogen and phosphorus in water bodies.
