粉喷桩体的力学性质试验研究

粉喷桩是处理软弱地基的一种重要方法.通过水泥土的室内配合比试验,研究了粉喷桩体的抗拉、抗压和抗剪强度性质及其影响因素,可为粉喷桩施工和设计提供理论指导.图1,表3,参5.     

Monoterpene emissions and carbonyl compound air concentrations during the blooming period of rape (Brassica napus)

An increasing percentage of agricultural land in Germany is used for oil seed plants. Hence, rape has become an important agricultural plant (in Saxony 1998: 12% of the farmland) in the recent years. During flowering of rape along with intensive radiation and high temperatures, a higher production and emission of biogenic VOC was observed. The emissions of terpenes were determined and more importantly, high concentrations of organic carbonyl compounds were observed during this field experiment. All measurements of interest have been carried out during two selected days with optimal weather conditions. It is found that the origin or the mechanism of formation of different group of compounds had strong influence on the day to day variation of their concentrations. The emission flux of terpenes from flowering rape plants was determined to be 16–32 μg h⁻¹ m⁻² (30–60 ng h⁻¹ per g dry plant––540–1080 ng h⁻¹ per plant), in total. Limonene, -thujene and sabinene were the most important compounds (about 60% of total terpenes). For limonene and sabinene reference emission rates (M_S) and temperature coefficients were determined: β_limonene=0.108 K⁻¹ and M_S=14.57 μg h⁻¹ m⁻²; β_sabinene=0.095 K⁻¹ and M_S=5.39 μg h⁻¹ m⁻².

The detected carbonyl compound concentrations were unexpectedly high (maximum formaldehyde concentration was 18.1 ppbv and 3.4 ppbv for butyraldehyde) for an open field. Possible reasons for these concentrations are the combination of primary emission from the plants induced by high temperature and high ozone stress, the secondary formation from biogenically and advected anthropogenically emitted VOC at high radiation intensities and furthered by the low wind speeds at this time.     

一体化间歇曝气完全混合活性污泥法

一体化间歇曝气完全混合活性污泥法处理装置采取特殊的沉淀区构造,改变了活性污泥的循环流动方式,通过间歇曝气,反应区交替处于好氧/缺氧状态,达到了有机物高效去除、高效硝化反硝化及控制污泥膨胀的效果.该方法具有出水水质好、运行稳定、能耗低、流程简洁和操作管理方便的特点,是一种很有发展潜力的一体化中小型生活污水、城市污水处理系统.     

一体化间歇曝气完全混合活性污泥法

一体化间歇曝气完全混合活性污泥法处理装置采取特殊的沉淀区构造,改变了活性污泥的循环流动方式,通过间歇曝气,反应区交替处于好氧/缺氧状态,达到了有机物高效去除、高效硝化反硝化及控制污泥膨胀的效果.该方法具有出水水质好、运行稳定、能耗低、流程简洁和操作管理方便的特点,是一种很有发展潜力的一体化中小型生活污水、城市污水处理系统.     

Monoterpene emissions and carbonyl compound air concentrations during the blooming period of rape (Brassica napus)

An increasing percentage of agricultural land in Germany is used for oil seed plants. Hence, rape has become an important agricultural plant (in Saxony 1998: 12% of the farmland) in the recent years. During flowering of rape along with intensive radiation and high temperatures, a higher production and emission of biogenic VOC was observed. The emissions of terpenes were determined and more importantly, high concentrations of organic carbonyl compounds were observed during this field experiment. All measurements of interest have been carried out during two selected days with optimal weather conditions. It is found that the origin or the mechanism of formation of different group of compounds had strong influence on the day to day variation of their concentrations. The emission flux of terpenes from flowering rape plants was determined to be 16–32 μg h⁻¹ m⁻² (30–60 ng h⁻¹ per g dry plant––540–1080 ng h⁻¹ per plant), in total. Limonene, α-thujene and sabinene were the most important compounds (about 60% of total terpenes). For limonene and sabinene reference emission rates (M_S) and temperature coefficients were determined: β_limonene=0.108 K⁻¹ and M_S=14.57 μg h⁻¹ m⁻²; β_sabinene=0.095 K⁻¹ and M_S=5.39 μg h⁻¹ m⁻².The detected carbonyl compound concentrations were unexpectedly high (maximum formaldehyde concentration was 18.1 ppbv and 3.4 ppbv for butyraldehyde) for an open field. Possible reasons for these concentrations are the combination of primary emission from the plants induced by high temperature and high ozone stress, the secondary formation from biogenically and advected anthropogenically emitted VOC at high radiation intensities and furthered by the low wind speeds at this time.     

制备方法对铁钛复合氧化物磷吸附性能的影响:共沉淀法与机械物理混合法

为了研究制备方法对金属复合氧化物表面性质与吸附性能的影响,本文分别采用共沉淀法与机械物理混合法制备了铁钛复合氧化物CFe-Ti与MFe-Ti.采用SEM、BET、XRD与FTIR等表征技术,研究了两种铁钛复合氧化物CFe-Ti与MFe-Ti的形貌结构、比表面积、表面羟基浓度等表面特性;通过批式吸附实验,考察了其磷吸附性能.结果表明,与纯的氧化物Fe OOH及TiO_2相比,共沉淀法制备的CFe-Ti纳米颗粒更疏松,孔结构更发达,表面羟基浓度更高,CFe-Ti的最大磷吸附容量达40.6mg·g~(-1),高于纯Fe OOH(27.2 mg·g~(-1))与TiO_2(16.7 mg·g~(-1)),分别为其1.5倍和2.4倍,展示了显著的协同效应.而MFe-Ti的形貌结构和表面性质与Fe OOH及TiO_2相比变化不大,其磷最大吸附容量为22.7 mg·g~(-1),不仅明显低于CFe-Ti,且低于纯Fe OOH,表明未产生协同效应.研究也表明,磷在CFe-Ti与MFe-Ti表面的吸附性质未发生变化,均通过形成内层表面络合物而发生了化学吸附.因此,金属复合氧化物的表面性质和吸附性能与其制备方法密切相关,与机械物理混合法相比,共沉淀法是一种更为简单经济制备高效能铁钛复合氧化物磷吸附剂的方法.     

人工强制混合充氧及诱导自然混合对水源水库水质改善效果分析

为探究人工强制混合充氧与诱导持续混合对水质改善的影响及人工强制混合与自然混合的衔接条件,以李家河水库为例,于2017年6月至2019年4月开展水质及水文气象指标监测,分析自然过程及人工诱导混合过程各时期水温、溶解氧及水质变化特征.结果表明:①自然过程分层期持续时间长,混合期仅为2.5个月,人工诱导混合过程通过扬水曝气系统的运行, 9月底水体达到完全混合且进入降温期,诱导自然混合条件具备,表层水温、平均气温分别为20.17℃和16.5℃,此时系统关闭后水体持续自然混合,混合周期延长至5.5个月;②自然过程污染物浓度较高,混合期表层污染物浓度呈现先增加后降低的趋势,氧跃层伴随热分层出现,底部厌氧周期达6个月;③相较于自然过程,人工诱导混合过程水体等温层厌氧消除且污染物控制效果良好, 10月至翌年3月同期底层NH~+_4-N、 TP、 Fe和Mn浓度的削减率为76.2%、 75.5%、 82.2%和82.1%,均达到地表水环境质量标准,人工诱导混合过程有利于水质改善及混合作用时效的延长.     

厌氧时间对间歇进水-间歇曝气的好氧颗粒污泥系统影响

为启动生活污水AGS工艺,实验以间歇进水-间歇曝气方式运行,降低硝氮浓度,减轻对PAO的抑制,利用除磷中产生的磷酸盐沉淀和正电微粒促进颗粒化实现.接种污水厂污泥于SBR反应器R1、R2、R3和R4中,在总厌氧时间为30、60、90和120 min时,研究厌氧时间对生活污水AGS系统的影响.实验表明,R1、R2、R3和R4历时56、48、39和35 d启动成功;运行105 d,平均粒径达750、764、791和650μm.运行期间,R1和R2在43 d和47 d除磷恶化,延长厌氧时间至90 min后恢复;R3处理效果良好; R4在63～77 d颗粒解体,处理效果下降,DPAO富集程度降低.运行后期,R1、R2、R3和R4出水水质均满足《城镇污水处理厂污染物排放标准》一级A标准.结果表明,长厌氧时间运行能实现快速颗粒化,但长期运行时颗粒易解体.较长的厌氧时间能减轻硝氮对PAO释磷的抑制,有助于富集DPAO,能获得良好的脱氮除磷效果.     

太湖地区农田NO排放不连续测量最佳时间

以我国南方太湖地区稻麦轮作生态系统的旱地阶段为例,在通过自动连续测量揭示ＮＯ排放的时间变异规律性基础上,讨论了ＮＯ排放不连续测量结果矫正及最佳观测时间选择．根据自动连续测量结果,ＮＯ排放表现出日间极大值型和夜间极大值型２种规律性日变化形式．前者发生在温度比较适宜,但植物生长较弱的情况下,此日变化形式直接与温度有关;后者发生在植物旺盛生长的情况下,且主要取决于植物对铵态氮的吸收,而与温度没有直接关系．在植物生长强弱变换的过渡期,日变化的规律性不明显．不连续测量结果的矫正因子也因植物生长状况而异．当观测时间选择不当,又不进行任何矫正处理时,根据不连续测量结果估计的ＮＯ排放可能偏高１２％ ～４７％ 或偏低１８％ ～６８％ ．无论哪种植物生长情形,１５ｖ００～１６ｖ００都是ＮＯ排放不连续测量的最佳观测时间．这时的观测结果不需要日变化矫正,能直接用来代表日平均排放量.     

Comparing the Extent and Permanence of Headwater Streams From Two Field Surveys to Values From Hydrographic Databases and Maps

Supreme Court cases have questioned if jurisdiction under the Clean Water Act extends to water bodies such as streams without year‐round flow. Headwater streams are central to this issue because many periodically dry, and because little is known about their influence on navigable waters. An accurate account of the extent and flow permanence of headwater streams is critical to estimating downstream contributions. We compared the extent and permanence of headwater streams from two field surveys with values from databases and maps. The first used data from 29 headwater streams in nine U.S. forests, whereas the second had data from 178 headwater streams in Oregon. Synthetic networks developed from the nine‐forest survey indicated that 33 to 93% of the channel lacked year‐round flow. Seven of the nine forests were predicted to have >200% more channel length than portrayed in the high‐resolution National Hydrography Dataset (NHD). The NHD and topographic map classifications of permanence agreed with ~50% of the field determinations across ~300 headwater sites. Classification agreement with the field determinations generally increased with increasing resolution. However, the flow classification on soil maps only agreed with ~30% of the field determination despite depicting greater channel extent than other maps. Maps that include streams regardless of permanence and size will aid regulatory decisions and are fundamental to improving water quality monitoring and models.