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271.
广州秋季不同功能区大气颗粒物中PAHs粒径分布 总被引:5,自引:8,他引:5
利用MOUDITM级联分段式采样器采集了秋季广州市区(荔湾采样点和五山采样点)及郊区(新垦采样点)3个采样点的气溶胶样品并使用GC-MS分析了样品中13种多环芳烃的含量.发现3~4环的多环芳烃呈双峰分布,5~7环的多环芳烃呈单峰分布.广州市区和郊区的多环芳烃具有不同粒径分布模式;相对于城区,郊区的多环芳烃存在于更大的颗粒物中,这可能是气溶胶的陈化过程不同导致的.城区的多环芳烃可能主要受吸附作用控制,而郊区的多环芳烃则可能受多种机制控制,如吸附作用、吸收作用和多层吸附.诊断参数值在粒径1~2.5μm和0.1~0.56μm存在较大差异;从浓度上看新垦13种多环芳烃的总浓度为39ng/m3,五山为71~94ng/m3,荔湾为32~154 ng/m3;从组成上看广州市大气颗粒物种多环芳烃以5~7环为主. 相似文献
272.
水电站运行影响河流的栖息地环境,进而影响底栖动物群落结构,从而对河流生态健康造成影响.基于牡丹江镜泊湖电站至石岩电站江段的底栖动物采样数据,分析该江段的底栖动物沿程变化规律以及梯级水电站群对水生态环境的影响.结果表明,梯级电站的运行对研究江段的多种生境因子造成了影响,改变了江段内底栖动物的群落结构.在电站的上游和下游,底栖动物群落结构差别明显,其中,电站下游环境敏感种的数量多于上游.相比坝式水电站,引水式水电站对底栖动物的影响较小.空间上来看,电站运行影响沿程逐渐减弱,底栖动物的密度和丰度呈现沿程增加的趋势. 相似文献
273.
Seasonal variations of soil bacterial communities in Suaeda wetland of Shuangtaizi River estuary, Northeast China 总被引:1,自引:0,他引:1
Xuwang Zhang Zhe Ji Yating Shao Chaochen Guo Hao Zhou Lifen Liu Yuanyuan Qu 《环境科学学报(英文版)》2020,32(11):45-53
Estuarine wetland is the transitional interface linking terrestrial with marine ecosystems, and wetland microbes are crucial to the biogeochemical cycles of nutrients. The soil samples were collected in four seasons (spring, S1; summer, S2; autumn, S3; and winter, S4) from Suaeda wetland of Shuangtaizi River estuary, Northeast China, and the variations of bacterial community were evaluated by high-throughput sequencing. Soil properties presented a significant seasonal change, including pH, carbon (C) and total nitrogen (TN), and the microbial diversity, richness and structure also differed with seasons. Canonical correspondence analysis (CCA) and Mantel tests implied that soil pH, C and TN were the key factors structuring the microbial community. Gillisia (belonging to Bacteroidetes) and Woeseia (affiliating with Gammaproteobacteria) were the two primary components in the rhizosphere soils, displaying opposite variations with seasons. Based on PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States) prediction, the xenobiotics biodegradation related genes exhibited a seasonal decline, while the majority of biomarker genes involved in nitrogen cycle showed an ascending trend. These findings could advance the understanding of rhizosphere microbiota of Suaeda in estuarine wetland. 相似文献
274.
上海河流氮负荷的年际变化及其水体富营养化的原因探讨 总被引:2,自引:1,他引:2
利用1990-2002年水质监测数据,分析了上海河流水体中氮负荷(总氮和氨氮)的年际变化特征:从整体上来看,上海河流水体氮负荷较大,氮污染严重:苏州河、黄浦江下游河段氮负荷明显高于上游河段,市区河流氮负荷明显高于郊区河流;从年际变化上看,苏州河、黄浦江、市区河流(除龙华港)水体历年氮含量有降低趋势,郊区河流水体历年氮含量有增长趋势。在此基础上,从六个方面讨论了造成上海河流水体富营养化的原因,以期为上海市河流综合整治的规划决策提供重要的科学依据。 相似文献
275.
276.
Anammox enrichment from different conventional sludges 总被引:23,自引:0,他引:23
Three sets of sequencing batch reactor (SBR) were used for Anammox enrichment from conventional sludges including upflow anaerobic sludge blanket, activated sludge, and anaerobic digestion sludge. After four months of operation, the Anammox activity occurred in all reactors allowing continuous removal of ammonium and nitrite. The morphology of the cultivated Anammox sludge was observed using scanning electron microscope. The photographs showed that the obtained culture was mostly spherical in shape, presumably Anammox culture. There were also filamentous-like bacteria co-existing in the system. Fluorescence in situ hybridization (FISH) analysis using 16S rRNA targeting oligonucleotide probes PLA46 and Amx820 showed that the dominant population developed in all SBRs was hybridized with both PLA46 and Amx820 gene probes. It means that the cultivated biomass in all SBRs was classified in the group of Planctomycetales bacteria with respect to the anaerobic ammonium-oxidizing bacteria, Candidatus Brocadia anammoxidans and Candidatus Kuenenia stuttgartiensis. Numerous time sequences were tested in this experiment. The shortest workable reaction time was found in the range from 5 to 7 h. Good quiescence of sludge was obtained at 30 min of settle period followed by a discharge period of 15 min. A long-term performance showed a near perfect removal of nitrite based on the influent NO2(-)-N concentration of 50-70 mg l(-1). The maximum ammonia removal efficiency was 80% with the influent NH4(+)-N concentration of 40-60 mg l(-1). It is, therefore, concluded that Anammox cultivation from conventional sludges was highly possible under control environment within four months. 相似文献
277.
278.
J. A. Laws B. F. Pain S. C. Jarvis D. Scholefield 《Agriculture, ecosystems & environment》2000,80(3):1032
Past research on nitrogen (N) inputs, losses and surpluses focused on separate components of grassland management, i.e., grazed or cut swards and the impact of fertiliser or slurry applications. In practice, however, grassland is both grazed and cut for conservation, and N fertiliser is supplied from both organic and inorganic sources. A whole systems approach was used to evaluate the effects of combinations of management strategies designed to reduce N losses on N budgets, and herbage and animal production in South West England. Three systems with contrasting N inputs were compared: CN, conventional mineral N application and broadcast slurry; TN, tactical mineral N application with slurry injection and the early housing of cattle; GC, a mixed grass/white clover sward with no mineral N addition and slurry injection. Comparisons were made on two contrasting soil types: a freely-draining sandy loam (Gleysol, Site 1), and a poorly drained clay (Luvisol, Site 2). 1 ha farmlets were grazed to a target sward height by beef cattle for a 5-year (Site 1) or a 4-year (Site 2) period. Herbage surplus to grazing requirements was cut for silage. On average, 185 kg N ha−1 was applied annually to treatment TN compared with 280 kg N ha−1 for CN. An additional 76, 102 and 67 kg N ha−1 was applied in slurry to treatments CN, TN and GC, respectively. Substantial reductions in N surpluses were achieved for both treatments TN and GC compared with treatment CN (N surpluses ha−1: 254, 168 and 119 kg at Site 1, and 247 kg, 190 and 73 kg at Site 2, for CN, TN and GC, respectively). The highest N input for treatment CN was associated with the greatest animal and herbage production. More land was required for grazing on treatment GC and less herbage was cut for silage so that self-sufficiency was not attained for winter fodder on this treatment. The early removal of cattle on treatment TN did not result in a significant increase in the amount of herbage cut for silage. It was concluded that the combinations of mitigation options used were successful in reducing N surpluses compared with the conventional N management system, but animal and herbage production was reduced. 相似文献
279.
从平流层和对流层的大气化学过程入手,分析了研究各个反应所采用的测量手段;从当前大气化学的发展要求提出了理论研究和模式建立中对仪器测量手段的要求。并且从测量坪台这一角度分析了目前在大气化学领域使用的主要测量仪器和手段。 相似文献
280.
城镇生活污水、含氮的工业废水和农田氮肥是水环境的主要氮污染源。影响水环境中氮污染的主要因素是含氨污水的排放性状、纳志水体的环境容量以及人为与自然条件下氮素的物理、化学的转化作用。 相似文献