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941.
942.
汉江上游郧县段全新世特大洪水事件光释光测年研究 总被引:1,自引:0,他引:1
通过对汉江上游的野外考察,在湖北郧县段河谷发现了含有典型的古洪水滞流沉积物的全新世风成黄土土壤剖面。对该剖面采集样品,进行了沉积学分析,并且应用光释光技术中的单片再生剂量法(SAR)测定获得其OSL年龄,结合地层对比和文化层考古学断代,确定由古洪水滞流沉积层记录的特大洪水事件发生在距今1 800~1 700 a之间,对应于我国历史上的东汉至魏晋时期(A.D. 200~300)。通过与汉江上游地区、国内和世界各地的多种指标气候变化记录的对比分析,揭示出特大洪水事件发生在东汉至南北朝时期的气候恶化期。由于气候状态不稳定,降水变率大,致使严重地干旱和特大洪水皆有发生。该成果对我们深刻理解区域水文系统对于全球变化的响应规律具有重要意义 相似文献
943.
Alam Md. Asraful Wan Chun Tran Dang Thuan Mofijur M. Ahmed Shams Forruque Mehmood Muhammad Aamer Shaik Feroz Vo Dai-Viet N. Xu Jingliang 《Environmental Chemistry Letters》2022,20(2):1153-1168
Environmental Chemistry Letters - Microalgae are photosynthetic cell factories of global interest for fuels, food, feed, bioproducts, carbon sequestration, waste mitigation, and environmental... 相似文献
944.
于2018—2021年对南京市及国考断面七桥瓮进行水质调查,分析其溶解氧变化特征,采用水质水量联合评价及皮尔逊相关分析法,并结合水文气象等相关信息,对南京市地表水溶解氧分布特征及国考七桥瓮断面低氧成因进行研究分析。结果表明,南京市地表水溶解氧浓度夏季最低,中心主城区及附近区域溶解氧浓度均相对较低。七桥瓮断面溶解氧浓度在2.25~11.07 mg/L,其中5—9月溶解氧易出现超标波动。溶解氧浓度昼间高于夜间,与pH值呈正相关关系,与水温、高锰酸盐指数、氨氮、总磷均呈负相关关系。水温和上游来水带入的耗氧污染物是七桥瓮断面溶解氧偏低的主要成因,其中,溶解氧浓度与水温相关性最为显著。研究结论可为七桥瓮断面稳定达标提供基础支撑,为秦淮河流域精准治污提供技术依据,为南京市水环境多源同治提供治理思路。 相似文献
945.
946.
利用多组分新型高效材料与普通硅酸盐水泥制得复配材料,开展箱涵清淤重金属(Cd、Cr、Cu、Ni、Pb和Zn)污染底泥钝化试验及工程应用研究,采用无侧限抗压强度和毒性浸出浓度评价钝化效果,进一步分析重金属赋存形态变化探讨钝化机制.结果表明,底泥:复配材料:黄沙质量配比为5:4:1时,钝化效果最佳.实际工程应用中,H型和O型固化砖抗压强度分别达10.82和10.11MPa,毒性浸出浓度远低于鉴别标准值(GB5085.3-2007),满足资源化应用要求.重金属浸出浓度与离子交换态和有机结合态占比呈正相关,有机结合态和铁锰氧化态分别为底泥和固化砖中重金属的主要赋存形态,二者占比在固化前后呈现完全相反的变化趋势,该变化对固化稳定化重金属起重要作用.除H型Cr外,其他固化砖中重金属残渣态占比均有所增加.该复配材料基于多组分物质间相互协同作用实现重金属钝化具有实际应用前景. 相似文献
947.
Zhijie Li Lu Lei Yanpei Li Chun Chen Qingqing Wang Wei Zhou Jiaxing Sun Conghui Xie Yele Sun 《环境科学学报(英文版)》2021,33(6):242-252
Extensive studies on aerosol chemistry have been carried out in megacities in China, however, aerosol characterization in Central China Plain (CCP) is limited. Here we conducted real-time measurements of fine particle composition with a time-of-flight aerosol chemical speciation monitor in Kaifeng, Henan province in October 2019. Our results showed that nitrate and organics constituted the major fraction of non-refractory PM2.5 for the entire study, on average accounting for 34% and 33%, respectively. However, aerosol composition was substantially different among four periods due to different meteorological conditions and chemical processing. For instance, nitrate presented the lowest contribution during the first period due to evaporative loss associated with high temperature (T), and then rapidly increased during polluted periods as a function of relative humidity (RH). Positive matrix factorization analysis showed the dominance of secondary organic aerosol (SOA) in OA, and also the changes in OA composition under different T and RH levels. In addition, this study is unique with two periods of local emission controls. Back trajectory and coefficient of divergence analysis showed that air pollution in CCP was overall homogeneously distributed. As a result, the effectiveness of local emission controls in this region was strongly affected by meteorological conditions and regional transport. We found that one of the periods with emission control even showed the highest concentrations for the entire study. Our results point towards the limited effect of local emission controls in mitigating air pollution in CCP, and highlight the importance of joint emission controls under unfavorable meteorological conditions. 相似文献
948.
Many problems in drinking water distribution systems (DWDSs) are caused by microbe, such as biofilm formation, biocorrosion and opportunistic pathogens growth. More iron release from corrosion scales may induce red water. Biofilm played great roles on the corrosion. The iron-oxidizing bacteria (IOB) promoted corrosion. However, when iron-reducing bacteria (IRB) and nitrate-reducing bacteria (NRB) became the main bacteria in biofilm, they could induce iron redox cycling in corrosion process. This process enhanced the precipitation of iron oxides and formation of more Fe3O4 in corrosion scales, which inhibited corrosion effectively. Therefore, the IRB and NRB in the biofilm can reduce iron release and red water occurrence. Moreover, there are many opportunistic pathogens in biofilm of DWDSs. The opportunistic pathogens growth in DWDSs related to the bacterial community changes due to the effects of micropollutants. Micropollutants increased the number of bacteria with antibiotic resistance genes (ARGs). Furthermore, extracellular polymeric substances (EPS) production was increased by the antibiotic resistant bacteria, leading to greater bacterial aggregation and adsorption, increasing the chlorine-resistance capability, which was responsible for the enhancement of the particle-associated opportunistic pathogens in DWDSs. Moreover, O3-biological activated carbon filtration-UV-Cl2 treatment could be used to control the iron release, red water occurrence and opportunistic pathogens growth in DWDSs. 相似文献
949.
为进一步提高活性焦脱硫脱硝性能,提出臭氧(O3)预氧化协同喷氨(NH3)的工艺优化思路.通过在固定床上开展相关均相反应实验,研究外部引入的O3、NH3对NOx、SO2的反应特性.结果表明,O3对NO的氧化反应为逐级过程,随着O3/NO物质的量比增大,O3将NO依次氧化为NO2和N2O5.O3对SO2的均相氧化作用十分有限,O3/SO2=1时SO2氧化率低于5.0%.在O3预氧化条件下喷入NH3后,O3/NH3=1时约有6.7%的O3消耗量;当O3/NO=1时,预氧化产物NO2含量显著下降,同时NO排放浓度小幅上升;当O3/NO=1.5时,NOx排放水平与未喷入NH3条件时相当.在O3和NH3协同作用下,SO2的氧化率显著提高,推测此时脱硫反应产物为更加稳定的NH4HSO4或(NH4)2SO4.O3-NH3协同脱硫脱硝反应中,O3/NO不超过1时,NH3-NO2和NH3-SO2反应同时发生,提高NH3引入量能够同时提高脱硫率和脱硝率.O3/NO > 1时,NH3-N2O5反应优先级最高,N2O5对NH3的消耗抑制了NH3-SO2脱硫反应发生.仅运用O3预氧化和NH3协同作用方式的脱硫脱硝效率较为有限,但对烧结烟气中氮、硫污染物的形态的改变产生重要影响. 相似文献
950.
Lee CW Srivastava RK Ghorishi SB Karwowski J Hastings TW Hirschi JC 《Journal of the Air & Waste Management Association (1995)》2006,56(5):643-649
A study was conducted to investigate the effect of selective catalytic reduction (SCR) catalyst on mercury (Hg) speciation in bituminous and subbituminous coal combustion flue gases. Three different Illinois Basin bituminous coals (from high to low sulfur [S] and chlorine [Cl]) and one Powder River Basin (PRB) subbituminous coal with very low S and very low Cl were tested in a pilot-scale combustor equipped with an SCR reactor for controlling nitrogen oxides (NOx) emissions. The SCR catalyst induced high oxidation of elemental Hg (Hg0), decreasing the percentage of Hg0 at the outlet of the SCR to values <12% for the three Illinois coal tests. The PRB coal test indicated a low oxidation of Hg0 by the SCR catalyst, with the percentage of Hg0 decreasing from approximately 96% at the inlet of the reactor to approximately 80% at the outlet. The low Cl content of the PRB coal and corresponding low level of available flue gas Cl species were believed to be responsible for low SCR Hg oxidation for this coal type. The test results indicated a strong effect of coal type on the extent of Hg oxidation. 相似文献