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541.
Photochemistry of a major commercial polybrominated diphenyl ether flame retardant congener: 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE153) 总被引:3,自引:0,他引:3
The photochemistry of a major commercial polybrominated diphenyl ether (PBDE) flame retardant congener, 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE153), was investigated in acetonitrile, distilled water, and seawater. After a short irradiation period in acetonitrile at 302 nm, the major photoproducts of BDE153 included 2,2',4,4',5-(BDE99), 2,2',4,5,5'-(BDE101), and 2,4,4',5,5'-(BDE118) substituted penta-BDEs as primary photohydrodebromination products, 2,2',4,4'-(BDE47), 3,3',4,4'-(BDE77), 2,3',4,4'-(BDE66), and 2,2',4,5'-(BDE49) substituted tetra-BDEs as secondary photohydrodebromination products, a suite of non-2,3,7,8-substituted mono- through penta-brominated dibenzofurans, and three tetrabrominated 2-hydroxybiphenyl congeners. By comparison, irradiation in distilled water and seawater gave increased relative photohydrodebromination contributions and no evidence for the formation of brominated dibenzofurans or 2-hydroxybiphenyls. In all solvent systems, subsequent degradation of primary and secondary photoproducts under continuing irradiation led to a steadily decreasing reaction mass balance. The results suggest a short photochemical half-life for BDE153 in aquatic systems, with rapid photohydrodebromination to some of the most prevalent penta- and tetra-brominated diphenyl ether congeners typically observed in environmental matrices. 相似文献
542.
目的 研究模拟海洋大气环境对舱外设备箱体腐蚀行为的影响,为快速评价舱外设备箱体原材料、原结构、原表面技术状态改进优劣提供技术和方法支撑。方法 根据XX舱外设备箱体实际服役环境剖面、腐蚀损伤状况,制定含海水模拟、湿热、维护保养及检查阶段等3个模块的实验室模拟海洋大气环境加速谱,运用外观、扫描电镜(SEM)、金相显微镜、X射线能谱(EDS)等表征技术,研究设备箱体在12个循环周期的宏微观形貌和腐蚀产物元素含量分布,并对标准金属铝和钢的同步实验室试验与XX近海户外自然环境下的腐蚀效应进行对比。结果 12个循环周期结束后,底座铝合金严重腐蚀,呈现明显的晶间腐蚀,并产生大量腐蚀产物,腐蚀产物主要含有O、Na、Al、Si、Cl、Ca、Mn、Fe等元素,其腐蚀形貌及程度与实际服役5 a的底座一致。标准金属铝和钢加速试验120 d的腐蚀效应分别等效XX近海大气试验4.65 a和10.57 a。结论 海水模拟、湿热、维护保养及检查阶段等3个模块的实验室模拟循环试验能较好地模拟XX舱外设备箱体经历的环境,其腐蚀与实际服役环境下的腐蚀程度相近,实现了基于短期内完成3~5 a的海洋运行验证。 相似文献
543.
544.
Dynamics of dissolved organic carbon in the mires in the Sanjiang Plain,
Northeast China 总被引:1,自引:0,他引:1
Mires in boreal area had proved to be an important dissolved organic carbon (DOC) reserve for the sensitivity to climate change
and human interfering. The study was focused on the temporal and spatial dynamics and controlling factors of DOC in a seasonallywaterlogged
mire (SLM) and perennially-waterlogged mire (PLM) in the Sanjiang Plain, Northest China. In the two mires, DOC
concentrations in both surface water and upper soil strata experienced pronounced seasonal variation. DOC concentrations in the
surface waters were the greatest and averagely was 47.82 in SLM and 34.84 mg/L and PLM, whereas that in soil water at 0.3-m depth
had little di erence (20.25 mg/L in SLM and 26.51 mg/L in PLM). Results revealed that DOC concentrations declined 5–8 times
vertically from the surface down to groundwater. DOC in the groundwater only was in a very small part with the average concentration
of 5.18 mg/L. In relation to the surface water, DOC concentrations varied positively with temperature just before 8 August, and only
in early spring and later autumn DOC concentrations exhibited identifiable spatial trends along with standing water depths in PLM. It
was supposed that the influences from standing water depth took e ect only in conditions of low temperature, and temperature should
be the most powerful factor controlling DOC dynamics in the mires. Redox potential (Red) showed negative relationship with DOC
values while total nitrogen (TN) and the majority of free ions in the soil solution exhibited no relationship. High soil TOC/TN ratio and
low redox potentials also led to DOC accumulation in the mires in the Sanjiang Plain. 相似文献
545.
感潮河段水环境容量总量控制方案的研究 总被引:1,自引:0,他引:1
以西江干流南海段为例,建立了考虑横向扩散的二维非恒定对流扩散水质模型。根据感潮河流水环境容量的特点,确定求解容量的因素。在此基础上,用线性规划法来求解研究河段水环境容量,并提出了相应的水环境规划方案。结果表明,该河段还有大量的COD容量剩余,可根据产业结构及工业布局调整的需要,在保证区域内总量控制目标实现的前提下,在西江沿岸适当配置一些有废水排放的建设项目。 相似文献
546.
547.
Feipeng Wang Dongbin Wei Miao Chen Shuang Peng Qiaorong Guo Xinyi Zhang Jun Liu Yuguo Du 《环境科学学报(英文版)》2022,34(2):106-114
Wastewater reclamation and reuse is an increasing global project, while the reclamation treatment on wastewater does not completely remove all pollutants in water. The residual pollutants in reclaimed water would cause potential risk on human health and ecosystem safety during the long-term use. It is impossible to analyze and control all pollutants one by one in practice, therefore, identification and control of priority pollutants will be efficient strategy to ensure the safe use of reclaimed ... 相似文献
548.
549.
550.
泸沽湖沉积物-水界面扩散作用对上覆水体基本化学组成的影响 总被引:4,自引:0,他引:4
通过云南泸沽湖──半封闭深水湖泊湖水和沉积物孔隙水中Ca2+、K+、Na+、HCO等基本组分及pH等剖面分布的研究,结果表明,这些基本组分可以自底部沉积物向上覆水体扩散迁移。定量地估算了扩散通量及其对上覆水体的影响程度,说明湖泊沉积物-水界面作用在控制整个水体水化学基本组成中起着重要的作用。 相似文献