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排序方式: 共有1249条查询结果,搜索用时 950 毫秒
961.
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964.
针对我国长江典型江段丰、平、枯不同时期的地表水,采用了固相萃取—气相色谱质谱联用(GC-MS)的分析技术,调查了16种优先控制多环芳烃(PAHs)的污染状况.研究了长江干流PAHs的污染水平和分布特征,并在定量分析的基础上评估了长江干流PAHs的来源和生态风险.结果显示,Σ16PAHs浓度范围为2.22~1450.91ng/L,均值为107.04ng/L,其中,平水期武汉江段Σ16PAHs浓度最高,均值为1050.64ng/L,长江干流PAHs污染状况与近5a国内其他水体相比处于中等偏低水平.空间分布上长江典型江段地表水中Σ16PAHs从上游攀枝花江段到下游南京江段呈现出先上升后下降的趋势;时间分布上Σ16PAHs的变化趋势为平水期(187.78ng/L)>丰水期(73.30ng/L)>枯水期(38.02ng/L).由同分异构比值法分析表明:在枯水期和平水期中,煤炭、生物质燃烧和石油源是长江干流PAHs的主要来源,而丰水期PAHs主要源于煤炭、生物质燃烧,其中南京江段PAHs的来源较为复... 相似文献
965.
Hongyi Ao Chenxi Wu Xiong Xiong Liandong Jing Xiaolong Huang Kai Zhang Jiantong Liu 《Environmental monitoring and assessment》2014,186(4):2121-2133
Qinghai Lake, situated on the Qinghai–Tibet plateau, is the largest lake in China. In this study, the water and sediment quality were investigated in Qinghai Lake, three sublakes, and five major tributaries. Both Na+ and Cl? were found to be the major ions present in Qinghai Lake and the three sublakes, while Ca2+ and HCO3? dominated the tributaries. Compared with historical data from the 1960s, the concentrations of NH4 +, NO3 ?, and soluble reactive silica have increased considerably, likely caused by increased human activities in the area. Compared to the historical data, chemical oxygen demand has increased and lake water transparency has decreased, likely related to an increase in nutrient levels. Relatively high concentrations of total nitrogen (TN) and total phosphorus (TP) were observed in Qinghai Lake sediments, although P fraction types and low water concentrations of these two indicate low possibility of transfer into the water column. The ratios of C/N suggest that the organic matter in the sediments are primarily from autochthonous sources. TN and total organic carbon in the sediment cores increased slowly up the core while TP and total inorganic carbon have been fairly constant. 相似文献
966.
967.
Meng Si Boxiong Shen George Adwek Lifu Xiong Lijun Liu Peng Yuan Hongpei Gao Cai Liang Qihai Guo 《环境科学学报(英文版)》2021,33(3):49-71
Due to the increasingly strict emission standards of NOx on various industries, many traditional flue gas treatment methods have been gradually improved. Except for selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) methods to remove NOx from flue gas, theoxidation method is paying more attention to NOx removal now because of the potential to simultaneously remove multiple pollutants from flue gas. This paper summarizes the efficiency, reaction conditions, effect factors, and reaction mechanism of NO oxidation from the aspects of liquid-phase oxidation, gas-phase oxidation, plasma technology, and catalytic oxidation. The effects of free radicals and active components of catalysts on NO oxidation and the combination of various oxidation methods are discussed in detail. The advantages and disadvantages of different oxidation methods are summarized, and the suggestions for future research on NO oxidation are put forward at the end. The review on the NO removal by oxidation methods can provide new ideas for future studies on the NO removal from flue gas. 相似文献
968.
969.
通过监测邢台市2017年11月15日—2018年3月15日采暖期间大气PM_(2.5)中水溶性离子,得到水溶性离子的污染特征,并结合主成分分析方法讨论不同离子的来源。结果表明,邢台市PM_(2.5)中水溶性离子主要由NO~-_3、SO_4~(2-)、NH~+_4组成,分别占总水溶性离子质量浓度的35.2%、25.7%、20.4%;SNA三元相图表明,NH~+_4、SO_4~(2-)、NO~-_3在PM_(2.5)中占比分别为10.6%~40.2%、20.5%~67.1%、26.4%~56.2%;主成分分析结果表明,PM_(2.5)中水溶性离子的主要来源有二次气溶胶、燃煤、交通源、生物质燃烧和土壤尘。 相似文献
970.
Lifang Wang Fengchang Wu Yongqiang Xiong Jidun Fang 《Environmental science and pollution research international》2013,20(4):2390-2397
Based on the molecular distribution of bound fatty acid (BFA) compound classes in core sediments of Lake Dianchi combined with the compound-specific δ13C values of the straight-chain BFAs, origin and vertical changes of organic matters in the sediments were investigated. The results indicated a significant change of BFA sources over the past 700 years. Contrast to the low concentrations of the terrestrial BFAs, the abundance of BFAs derived from the plankton/bacteria in the top sections (1944–recent) was more than 80 %. The increasing proportions of the branched and unsaturated BFAs in total fatty acids were closely correlated with the heavy eutrophication and the frequent algal blooms in the decades. Furthermore, the positive shift of δ 13C of C16 and C18 (~2?‰) in the upper section might be an indicator of the excess phytoplankton productivity. However, it was found that the plankton/bacteria-derived BFAs were more easily degraded during the early diagenetic process. The special compound carbon isotopic compositions of the long straight-chain BFAs (C24 and C26) in the sediments showed a depletion of heavier δ 13C values (ca. ?30?‰) in the midsections (1559–1787), reflecting a relatively growing contribution of C3 plants to C4 plants or that C4 plant growth was inhibited in cold and arid climates during the period. 相似文献