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排序方式: 共有489条查询结果,搜索用时 31 毫秒
481.
Sisi Li Liang Zhang Yun Du Hongbin Liu Yanhua Zhuang Shuzhi Liu 《Environmental Modeling and Assessment》2016,21(5):657-668
The identification of critical source areas (CSAs) and critical source periods (CSPs) are essential prerequisites for cost-effective practices of non-point source (NPS) pollution control. A simple empirical tool combining Export Coefficient Model (ECM) and a Geographic Information Systems (GIS)-based weighting scheme of watershed heterogeneity was proposed to estimate annual and monthly phosphorus loss, to identify critical source areas and periods, and to assess pollution control practices. The GIS-based weighting scheme was developed to represent the transport potential of runoff to move phosphorus from the land surfaces to waters, as a supplement to the source-based ECM. The empirical tool was applied to the Dianchi Lake watershed of China. The results showed that the total phosphorus loss from NPS in 2008 was 352.3 tons. The agricultural land was recognized as the largest and the most spatially various source type. The lakeside plain and the terraces of the watershed were identified as CSAs, which generated more than 90 % of non-point phosphorus. The early part of wet season (from May to August) was the CSPs, when about 70 % of non-point phosphorus was lost. The reduction of phosphorus fertilizers and the vegetated buffer strips (VBS) were effective in controlling phosphorus loss from NPS in the watershed. A reduction of 20 % in phosphorus fertilizer application combined with the set-up of VBS in both riparian area of the main watercourses and the lakeside areas would decrease 25 % of phosphorus loss. 相似文献
482.
太湖缓坡丘陵地区雨强对农业非点源污染物随地表径流迁移的影响 总被引:6,自引:5,他引:6
以流域尺度为研究单元,流量、水质同步监测分析了雨强对太湖缓坡丘陵地区农田土壤养分随地表径流迁移的影响.10场降雨试验结果显示,雨强对农田氮、磷径流迁移有巨大影响.总磷、磷酸盐及氨氮EMC值随雨强的增强而增大;小降雨强度条件下,总氮、硝氮EMC值随雨强的增强而增大,强降雨条件下,其EMC值与雨强呈负相关.小雨、中雨、大雨及暴雨条件下,总氮及总磷的SMA值依次为1.91、311.83、127.65、731.69g/hm2及0.04、7.77、2.99、32.02g/hm2,与雨强表现出正相关.硝氮及氨氮是氮素迁移的主要类型,且主要是溶解态迁移.磷酸盐是磷迁移的主要形态.小降雨强度下,磷以溶解态迁移为主,随着雨强的增强,颗粒态磷迁移量逐渐增加,当雨强达到暴雨时,磷主要是颗粒态迁移.次降雨量、小时最大雨强、平均雨强及降雨历时影响因素中,氮、磷迁移量与小时最大雨强及次降雨量显著相关(p0.01),均表现为正相关. 相似文献
483.
活性污泥吸附废水中的铍 总被引:3,自引:0,他引:3
探讨了活性污泥吸附处理含铍废水的吸附动力学特性及吸附模型,研究了吸附后铍在活性污泥上的存在形态。实验结果表明,铍离子在活性污泥上的吸附行为遵循二级动力学规律,活性污泥在溶液中的分散性非常好,污泥微孔内扩散效应不是吸附过程的主要控制步骤,扩散速率主要由液相向固相的传质速率所控制,铍在污泥上的吸附主要为快速的表面吸附。铍在活性污泥上的吸附数据既可用Freundlich方程描述,也符合Langmuir吸附规律,Langmuir曲线的相关性还较Freundlich曲线高,吸附过程受温度影响不大,通过对处理后污泥的连续提取实验研究可知,处理后的活性污泥中铍的主要存在形态为有机结合态、残渣态和交换态。 相似文献
484.
485.
486.
膨胀石墨除油机理及影响因素研究 总被引:2,自引:0,他引:2
针对水面浮油的去除问题,通过对新型吸附材料-膨胀石墨的扫描电镜观察,从其结构特征的角度揭示了膨胀石墨的吸油机理,首次系统地研究了温度、时间、pH等操作条件对吸附油性能的影响。扫描电镜的结果显示膨胀石墨的鳞片厚度都在100 nm以上,而且以大孔、超大孔为主,这种结构赋予了膨胀石墨独特的吸附特性。操作条件对膨胀石墨的吸附性能有重要的影响,在本实验条件下即在酸(中)性条件下,吸附时间1 min-2 min左右,转速为660 r/min膨胀石墨可达到饱和吸附量。 相似文献
487.
488.
Zhuang Minghao Caro Dario Qin Wei Wang Chun Yang Xiaolin Liu Rui Zhang Lin 《Environmental Chemistry Letters》2022,20(6):3371-3376
Environmental Chemistry Letters - China is a major producer of wheat, maize and rice, which generates massive greenhouse gas emissions due to the consumption of elevated amounts of energy, land,... 相似文献
489.
Criegee intermediates (CIs), also known as carbonyl oxide, are reactive intermediates that play an important role in the atmospheric chemistry. Investigation on the structures and reactivity of CIs is of fundamental importance in understanding the underlying mechanism of their atmospheric reactions. In sharp contrast to the intensively studied parent molecule (CH2OO) and the alkyl-substituted derivatives, the knowledge about the fluorinated analogue CF3C(H)OO is scarce. By carefully heating the triplet carbene CF3CH in an O2-doped Ar-matrix to 35 K, the elusive carbonyl oxide CF3C(H)OO in syn- and anti-conformations has been generated and characterized with infrared (IR) and ultraviolet-visible (UV-vis) spectroscopy. The spectroscopic identification is supported by 18O-labeling experiments and quantum chemical calculations at the B3LYP/6-311++G(3df,3pd) and MP2/6-311++G(2d,2p) levels. Upon the long-wavelength irradiation (λ > 680 nm), both conformers of CF3C(H)OO decompose to give trifluoroacetaldehyde CF3C(H)O and simultaneously rearrange to the isomeric dioxirane, cyclic-CF3CH(OO), which undergoes isomerization to the lowest-energy carboxylic acid CF3C(O)OH upon UV-light excitation at 365 nm. The O2-oxidation of CF3CH via the intermediacy of CF3C(H)OO and cyclic-CF3CH(OO) might provide new insight into the mechanism for the degradation of hydro-chlorofluorocarbon CF3CHCl2 (HCFC-123) in the atmosphere. 相似文献