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331.
332.
为了揭示不同污泥龄活性污泥的絮凝特性及作用机制,采用序批式反应器,考察污泥龄(solid retention time,SRT)对絮体EPS(extra-micro colony polymeric substances,EMPS)和菌胶团EPS(extra-cellular polymeric substances,ECPS)2种EPS组分的影响,通过扩展的DLVO理论和EPS组分解析不同污泥龄的絮凝性能。研究结果表明,随着SRT的增大,活性污泥的相互作用能曲线存在明显的势垒和势垒值逐渐减少,EMPS和ECPS含量逐渐减少,且相对于ECPS的变化,EMPS含量随泥龄的变化更加明显,其中蛋白质与腐殖质含量逐渐降低,污泥絮凝性能变好。这表明,较高的污泥相互作用能势垒和EMPS组分含量是污泥絮凝性能低的内在机制,且EMPS中蛋白质和腐殖质含量的变化是不同污泥龄污泥絮凝性能差异的主要原因。 相似文献
333.
为系统研究选择性催化还原(SCR)反应器入口参数与反应温度对脱硝性能的交互作用,基于E-R机理,通过建立SCR脱硝反应一维模型,结合燃煤电厂调峰实际运行数据设定入口参数界限,利用MATLAB数值仿真,分别对反应温度同氨氮摩尔比(NSR)、入口NO质量浓度和入口速度对脱硝效率及氨逃逸率的耦合效应进行了重点分析。结果表明:入口参数对最佳反应温度影响较大;偏离最佳反应温度越多,NSR对氨逃逸率影响程度越低,NSR>1时,脱硝性能对NSR敏感性降低;增大入口NO质量浓度可改善整体脱硝性能,当入口质量NO浓度为1 050 mg·Nm−3时 ,脱硝效率可达82.42%,氨逃逸率低至0.33%;入口速度与反应温度的交互作用最大,降低入口速度可拓宽催化剂高活性温度窗口,显著提升脱硝性能,将入口速度由7 m·s−1降至1 m·s−1,最佳脱硝效率由69.32%升至89.17%,最低氨逃逸率由8.11%趋近于0;燃煤电厂调峰运行负荷上升会导致脱硝效率下降和氨逃逸加剧。该研究结果可为燃煤电厂SCR脱硝性能的整体优化提供参考。 相似文献
334.
Food web research provides essential insights into ecosystem functioning, but practical applications in ecosystem-based management are hampered by a current lack of knowledge synthesis. To address this gap, we provide the first systematic review of ecological studies applying stable isotope analysis, a pivotal method in food web research, in the heavily anthropogenically impacted Baltic Sea macro-region. We identified a thriving research field, with 164 publications advancing a broad range of fundamental and applied research topics, but also found structural shortcomings limiting ecosystem-level understanding. We argue that enhanced collaboration and integration, including the systematic submission of Baltic Sea primary datasets to stable isotope databases, would help to overcome many of the current shortcomings, unify the scattered knowledge base, and promote future food web research and science-based resource management. The effort undertaken here demonstrates the value of macro-regional synthesis, in enhancing access to existing data and supporting strategic planning of research agendas.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-022-01785-1. 相似文献
335.
有机氮(ON)在雨水径流氮素污染中起关键作用,但多数研究只关注可生物降解有机氮的生物转化去除,忽略了占比较高的难生物降解有机氮.以生物炭作为吸附剂,探究其对雨水径流典型难生物降解有机氮(吲哚)的吸附效能及机制.结果表明,原始生物炭对吲哚有较高的单位吸附量(45 mg·g-1),生物炭投加浓度为0.4 g·L-1时其表面平均吸附位点利用度最高.H2O2和NaOH改性生物炭对吲哚的吸附量是原始生物炭的1.3倍和1.6倍,吸附机制包括疏水相互作用、氢键和π-π电子供体-受体(π-π EDA)作用,以疏水相互作用为主,其中H2O2改性通过增加生物炭表面含氧官能团来加强氢键和π-π EDA作用,而NaOH改性生物炭通过大幅提高生物炭比表面积来加强疏水相互作用,故NaOH改性吸附效果更优.综上,生物炭对难生物降解有机氮具有较强去除作用,通过NaOH改性还能大幅提高效率,故在雨水径流氮素污染较高的地区把NaOH改性生物炭作为生物滞留池中的填料有着极大的应用潜力. 相似文献
336.
Hypotheses relating the behavior of voles to their population cycles often assume that the rate of social interaction increases
with population density. To test this assumption, we examined the frequency of social interactions in a population of prairie
voles (Microtus ochrogaster) over a 7-year period. In addition, we characterized space use by resident animals, patterns of visitation by nonresidents
to nests, and participants in social interactions. Social groups within the population typically displayed little overlap
in their use of space, even at high population densities. Nevertheless, nonresidents, particularly wandering males, were captured
as visitors at nests. The number of visits per social group did not increase in a simple linear manner with population density
and was particularly variable when there were fewer than 100 animals/ha. At such times, more single females and fewer pairs
received visits from males than expected based on the frequency of occurrence of these groups in the population; a similar
pattern was noted during periods of high population density (≥100 animals/ha) but the comparisons failed to reach statistical
significance. Furthermore, at high population density, more communal groups received visits from females than expected. Patterns
of visitation to communal groups were influenced by the number of adult male residents (winter only), but not by the number
of adult female residents or presence of philopatric female offspring. These data indicate that the frequency of social contact
in prairie voles does not increase linearly with population density and is influenced by the spacing and possible mate-guarding
behavior of resident animals.
Received: 7 January 1998 / Accepted after revision: 16 May 1998 相似文献
337.
338.
目的获得航炮发射时炮舱结构的动响应。方法依据火炮发射原理,使用化学爆炸模拟炮口冲击波,建立航炮发射时炮口冲击载荷的表达模型。利用ALE方法处理高压流动空气与炮舱表面的流固耦合问题,通过数值计算获得发射气流冲击载荷作用下炮舱结构的表面压力分布与动响应。利用试验结果,修正载荷与炮舱模型的有关参数。结果计算得到的炮舱动响应与试验结果相比较,误差在可接受范围内。结论建立了一种使用化爆模拟冲击波进行航炮炮舱结构炮振响应仿真计算的技术方法,初步确定了结构危险部位,为后续炮舱结构减振设计创造了条件。 相似文献
339.
针对天津机场区域考虑航班运行影响,应用广义加性模型(Generalized Additive Model,GAM)建立污染物浓度预测模型,对因子间的共线性问题和交互作用进行改进,得到最优的NOx浓度预测模型.选取天津机场区域2019年11月—2020年3月环境、气象及航班数据,建立改进的GAM.结果显示:(1)改进的GAM预测效果优,可以更加准确地预测浓度峰值及变化趋势;(2)样本量会影响模型选择的因子数量及模型性能;(3)改进模型adj-R2为0.940,实测和预测NOx浓度的相关系数为0.975,预测效果好;(4)航班活动对机场区域污染物浓度影响较大.改进的GAM考虑污染物浓度与影响因子之间的复杂非线性关系及影响因子之间交互作用对污染物浓度变化的影响,使模型精度进一步提升. GAM对污染物浓度的准确预测可为机场区域污染防治提供依据. 相似文献
340.
Feihu Yao Hailong Liu Guangquan Wang Liming Du Xiaofen Yin Yunlong Fu 《环境科学学报(英文版)》2013,25(6):1245-1251
Paraquat (PQ), a nonselective herbicide, is non-fluorescent in aqueous solutions. Thus, its determination through direct fluorescent methods is not feasible. The supramolecular inclusion interaction of PQ with cucurbit[7]uril was studied by a fluorescent probe titration method. Significant quenching of the fluorescence intensity of the cucurbit[7]uril-coptisine fluorescent probe was observed with the addition of PQ. A new fluorescent probe titration method with high selectivity and sensitivity at the ng/mL level was developed to determine PQ in aqueous solutions with good precision and accuracy based on the significant quenching of the supramolecular complex fluorescence intensity. The proposed method was successfully used in the determination of PQ in lake water, tap water, well water, and ditch water in an agricultural area, with recoveries of 96.73% to 105.77%. The fluorescence quenching values (ΔF) showed a good linear relationship with PQ concentrations from 1.0×10-8 to 1.2× 10-5 mol/L with a detection limit of 3.35×10-9 mol/L. In addition, the interaction models of the supramolecular complexes formed between the host and the guest were established using theoretical calculations. The interaction mechanism between the cucurbit[7]uril and PQ was confirmed by 1H NMR spectroscopy. 相似文献