Effectiveness of emergent and submergent aquatic plants in mitigating a nitrogen–permethrin mixture

Hydraulically connected wetland microcosms (～50?L) in series were used to test the effectiveness of varying combinations of two common aquatic vascular plants, parrot feather (Myriophyllum aquaticum) and cattail (Typha latifolia), for mitigating contamination from a mixture of nitrogen (ammonium nitrate) and permethrin. The upstream series included Myriophyllum only (M) and Typha only (T) while the combination upstream effluent into downstream series included Myriophyllum into Myriophyllum (M?+?M) and Typha into Myriophyllum (T?+?M). During flow, M into M?+?M more efficiently mitigated nitrogen than T into T?+?M. Post-flow, nitrogen removal efficiency was greater for T versus M and M?+?M versus T?+?M. Mean aqueous dissipation half-lives (t_1/2) of NH₄-N and NO₃-N were more rapid in T than M treatments. Ammonium and nitrate t_1/2 was highly correlated with aquatic plant above-ground shoot biomass. Permethrin mitigation efficiencies and t_1/2 were not significantly affected by plant species either singly or in combination. Trans-permethrin t_1/2 was moderately correlated with plant biomass, but not cis-permethrin t_1/2. Results of this study indicate differences in aquatic plant species and flow path influence nitrogen removal but not permethrin. However, plant species appears less important than overall plant biomass in ascertaining aquatic plant effectiveness in mitigating a nitrogen–permethrin mixture.     

上海地区霾时气溶胶类型垂直分布的季节变化

采用上海地区2007年1月~2010年11月CALIPSO星载激光雷达Level 2反演资料,对清洁海洋型、沙尘型、大陆污染型、大陆清洁型、污染沙尘型和烟尘型等类型气溶胶垂直分布进行了分析,研究了其季节变化规律.结果表明:霾发生时0~2km高度烟尘型气溶胶出现频率明显高于非霾时,而在2~8km高度,沙尘型、污染沙尘型与大陆污染型明显高于非霾时.0~2km高度春季霾大陆污染型气溶胶出现频率高于其他季节;0~2km夏季污染沙尘型气溶胶与海洋型气溶胶出现频率均高于其他季节,特别是污染沙尘型;秋季霾期间,0~2km高度范围内烟尘型出现频率明显高于2~6km高度;冬季污染沙尘型、烟尘、大陆污染型气溶胶出现频率高于其他季节.