内陆丘陵河谷地区小风条件下的大气扩散模拟研究

针对湖南中部丘陵河谷地区的气象特点,开展了小风条件下大气扩散的数值模拟研究,并与示踪实验结果进行比较.模拟采用美国EPA推荐的非稳态拉格朗日高斯烟团模式CALPUFF,以加密的地面气象观测资料、边界层垂直廓线观测资料和铁塔多层湍流观测资料作为模拟气象场的输入.中等风速和小风条件下的模拟结果表明:模式对地表类型及资料的分...     

Optimization of process parameters using response surface methodology for bioconversion of activated sludge by Penicillium corylophilum

The optimization of process parameters for the bioconversion of activated sludge by Penicillium corylophilum was investigated using response surface methodology （RSM）. The three parameters namely temperature of 33℃, agitation of 150 r/min, and pH of 5 were chosen as center point from the previous study of fungal treatment. The experimental data on chemical oxygen demand （COD） removal （%） were fitted into a quadratic polynomial model using multiple regression analysis. The optimum process conditions were determined by analyzing response surface three-dimensional surface plot and contour plot and by solving the regression model equation with Design Expert software. Box-Behnken design technique under RSM was used to optimize their interactions, which showed that an incubation temperature of 32.5℃, agitation of 105 r/min, and pH of 5.5 were the best conditions. Under these conditions, the maximum predicted yield of COD removal was 98.43%. These optimum conditions were used to evaluate the trail experiment, and the maximum yield of COD removal was recorded as 98.5%.     

四氯化碳在包气带的迁移机理及动态降解

生物降解方法是处理有机物污染的土壤和地下水的主要途径。试验以污染场地土壤为样本,分析土样的有机碳含量、容重、密度、孔隙比、饱和含水率等基本物理特性,并制作成试验土柱,模拟研究四氯化碳在包气带土壤中垂直迁移规律,动态分析影响生物降解的主要因素。结果表明,四氯化碳随淋溶作用向深层迁移,并在包气带底部积聚;温度是影响生物降解的重要因素,当温度为18℃时,稳定降解率最大为48.2μg/L;该菌株最适宜降解的四氯化碳淋溶强度为42.3μg/L,此时菌株能正常地进行生物代谢;25 g/L的葡萄糖对微生物降解有促进作用,稳定降解率达44.3%。     

济宁市生活垃圾渗滤液的电化学氧化法处理技术探析

目前,生活垃圾污染已经日趋严重,而生活垃圾渗滤液对环境造成的危害更是不容忽视,它影响地表景观,污染地下水,因此,对生活垃圾渗滤液的处理显得尤为重要.本文采用电化学氧化法研究生活垃圾渗滤液中CODcr和NH3-N去除率的影响因素,通过正交实验法得出:当电流密度为7.5 A/dm2、NaCl投加量为2g、pH为4时,经过2h的电解,二者的去除率均很高,因此,这种电化学氧化法对生活垃圾渗滤液处理具有较好的效果.     

太湖湖心区的痕量金属历史沉积过程研究

以太湖湖心区的沉积物为研究对象,解析了湖心区痕量金属的沉积通量年变化,探明了湖心区痕量金属的历史沉积情况.结果表明:湖心区各样点沉积物的沉积速率从1950年以前的(0.032±0.023)g·cm-2·a-1缓慢递增到1980前后的(0.076±0.030)g·cm-2·a-1,1980年后突增明显,在2000年后达到(0.185±0.132)g·cm-2·a-1.湖心区沉积物中8种痕量金属(钒、铬、镍、铜、锌、砷、镉和铅)的含量年变化没有明显递增趋势,在20世纪80年代(对应沉积柱4~9 cm深度处)前后相差不大(变幅小于20%).但8种金属元素的沉积通量随时间推进而递增,与1980年前相比,金属沉积通量在1980年后突增倍数达到11倍以上.金属沉积通量与沉积物的沉积速率显著正相关,并与20世纪20年代以来太湖流域社会经济发展形势相一致.1980年后8种痕量金属沉积总量在湖心区西部最大,而沉积物沉积速率对湖心区南部的痕量金属沉积总量贡献最大.通过金属沉积通量可以更全面地研究太湖重金属的历史沉积过程和人为活动的干扰效应.     

Investigation on removal of p-nitrophenol using a hybridized photo-thermal activated persulfate process: Central composite design modeling

The aim of this work is the study of p-nitrophenol (PNP) removal, as a nitroaromatic compound, using a hybridized photo-thermally activated potassium persulfate (KPS) in a fully recycled batch reactor. Response surface method was used for modeling the process. Reaction temperature, KPS initial dosage and initial pH of the solution were selected as variables, besides PNP degradation efficiency was selected as the response. ANOVA analysis reveals that a second order polynomial model with F-value of 41.7, p-value of 0.0001 and regression coefficient of 0.95 is able to predict the response. Based on the model, the process optimum conditions were introduced as initial pH of 4.5, [KPS]₀ = 1452 mg/L and T = 66 °C. Also experiments showed that using thermolysis and photolysis of the persulfate simultaneously, the role of thermolysis is not considerable. A pseudo first order kinetic model was established to describe the degradation reaction. Operational cost, as a vital industrial criterion, was estimated so that the condition of initial pH of 4.5, [KPS]₀ = 1452 mg/L and T = 25 °C showed the highest cost effective case. Under the preferred mild condition, the process will reach to 84% and 89% of degradation and mineralization efficiencies, after 60 and 120 min, respectively.     

屋顶绿化二氧化碳减排效益的研究

屋顶绿化不仅能够美化城市环境,而且对城市二氧化碳减排具有一定作用。文章利用自行设计的熏气装置对几种常见屋顶绿化植物进行CO2熏气实验,测定其对CO2的吸收速率和影响因素;实验结果表明,红叶石楠、红继木和石榴等绿化植物对CO2具有显著的吸收能力,其中红叶石楠的吸收速率最高,达7.058 L/(m.2d),绿化植物对CO2的吸收速率受屋面温度影响较大,温度超过34℃时吸收速率快速减小;在实验观测基础上,结合武汉城市区域气候特征、建筑物荷载能力、屋顶绿化可用面积等信息,分析得到武汉市进行规模化屋顶绿化之后,每年可吸收转化CO21.696×106t,相当于一个194 MW火力发电厂一年的CO2排放量,屋顶绿化的发展前景较可观。     

乙酰磺胺酸钾废水的预处理工艺优化研究

在确定微电解、Fenton氧化、混凝沉淀各自最佳反应条件的基础上,进一步研究了单独混凝、H2O2强化微电解工艺对废水的处理效果。试验结果表明,单独混凝工艺在最佳条件下COD、NH3-N、TP的平均去除率分别为16.9%、20.1%、59.4%;强化微电解工艺在最佳反应条件下,COD、NH3-N、TP去除率分别为32%、-4.5%、69%。通过对比试验发现,微电解/Fenton氧化/混凝沉淀联合工艺效果最好,COD平均去除率能达到55%。对该化工厂的废水预处理工艺提出改造方案,初步预算了工程改造投资及药剂费用。     

Reaction mechanism and process safety assessment of acid-catalyzed synthesis of tert-butyl peracetate

Esterification during the synthesis of tert-butyl peracetate (TBPA) is highly exothermic. Since peroxides (tert-butyl hydroperoxide TBHP and TBPA) are intrinsically thermosensitive, this synthesis process is potentially dangerous. In this work, the exothermic process and mechanism of TBPA synthesis using acetic anhydride (Ac₂O) and TBHP under the catalysis of sulphuric acid (H₂SO₄) were clarified by calorimetry, infrared spectroscopy, and high-performance liquid chromatography. To substantially alleviate the thermal risk of the reaction, and to feasibly select appropriate synthesis conditions for ensuring the process safety of the synthesized products, several sets of isothermal and isoperibol experiments were performed using calorimetry. The intermediates formed and concentration changes during the reaction were monitored using in-situ Fourier-transform infrared spectroscopy. Differential scanning calorimetry and adiabatic calorimetry were used to assess the thermal hazard of the materials during the synthesis process. The reaction mechanism was verified using density functional theory calculations. The results revealed that a controlled increase in exothermicity could be achieved by adding aqueous TBHP to Ac₂O in semi-batch experiments in isothermal mode, and accordingly, the highest yield was 95.71%. Experiments combined with theoretical calculations revealed that the primary exothermic event was the TBPA formation reaction, and the removal of a large amount of water from TBHP prior to this is favourable for the reaction. The criticality classes of this reaction were of Grade 2.