Wall losses of oxygenated volatile organic compounds from oxidation of toluene: Effects of chamber volume and relative humidity

Vapor wall losses can affect the yields of secondary organic aerosol. The effects of surface-to-volume (S/V) ratio and relative humidity (RH) on the vapor-wall interactions were investigated in this study. The oxygenated volatile organic compounds (OVOCs) were generated from toluene-H₂O₂ irradiations. The average gas to wall loss rate constant (k_gw) of OVOCs in a 400 L reactor (S/V = 7.5 m⁻¹) is 2.47 (2.41 under humid conditions) times higher than that in a 5000 L reactor (S/V = 3.6 m⁻¹) under dry conditions. In contrast, the average desorption rate constant (k_wg) of OVOCs in 400 L reactor is only 1.37 (1.20 under humid conditions) times higher than that in 5000 L reactor under dry conditions. It shows that increasing the S/V ratio can promote the wall losses of OVOCs. By contrast, the RH effect on k_gw is not prominent. The average k_gw value under humid conditions is almost the same as under dry conditions in the 400 L (5000 L) reactor. However, increasing RH can decrease the desorption rates. The average k_wg value under dry conditions is 1.45 (1.27) times higher than that under humid conditions in the 400 L (5000 L) reactor. The high RH can increase the partitioning equilibrium timescales and enhance the wall losses of OVOCs.     

Prenatal diagnosis of omphalocele and gastroschisis by ultrasonography

As the use of ultrasonography has become a routine procedure in the care of pregnant women, fetal congenital malformations have been frequently diagnosed prenatally. During a 4-year period abdominal wall defects (AWD) were diagnosed in 14 cases, five were gastroschises and nine were omphaloceles, seven females and seven males. Concomitant malformations were present in one case of gastroschisis and in five cases of omphalocele. Eleven AWD's were diagnosed in the second trimester and six pregnancies were interrupted. Eight children with AWD were born; two boys with omphalocele and one girl and one boy with gastroschisis are still alive. Alpha-fetoprotein was determined in amniotic fluid in 11 cases and also in maternal serum prior to the amniocentesis in eight cases. Chromosomal investigations were performed in 13 cases, 11 on amniotic fluid cells and two on lymphocytes from a blood sample made postnatally. Two abnormal karyotypes, 47,XX + 18 were found.     

影响街区峡谷浓度扩散的因素

对街区峡谷内污染扩散规律的研究是城市空气质量预测的主要内容之一。应用现代流体力学数值模拟方法进行大量算例的计算和分析,研究了城市街区峡谷污染物二维扩散的规律。在分析二维街区峡谷内浓度扩散的规律时,发现对街区峡谷浓度扩散的两个影响因素,其中定量分析了湍流脉动对浓度扩散的影响,与层流时得到的浓度扩散进行了通量积分的比较;此外,定性分析了不同类型的街区峡谷对扩散的影响。     

初论环境信息污染及预防

从SARS所引发的社会现象分析,首次从环境角度对信息污染进行探讨,提出了环境信息污染的含义及特征。并针对环境信息污染的潜在危害性,论述治理环境信息污染应以预防为主。建议政府和个人逐步通过建立“信息墙”,使信息更加有序、有条理,以此来预防和减少环境信息污染。     

基于热湿交换理论的巷道风流温、湿度影响因素研究

为了研究巷道风流参数的影响因素、预测风流温湿度的变化规律,结合热湿交换理论,建立了风流与围岩壁面之间热湿交换的数学模型,以及贴体坐标系下围岩内部温度场的导热微分方程;利用数值方法,将围岩内部的导热问题与影响风流参数变化的热湿交换问题耦合起来,并以大柳塔煤矿52505综采工作面为例进行计算,得到了与实测参数较为一致的模拟结果,验证了该数值方法的有效性。研究结果表明:风流温度受原始岩温、入风流温度、局部热源强度等因素的影响,风流相对湿度与入风流温、湿度以及井下湿源的数量和强度有关;巷道壁温作为将围岩温度场与风流参数之间关联起来的主要因素,对模拟结果影响较大,其数值取决于壁面与风流之间热湿交换以及围岩原始岩温。     

Flow Dynamics in Eccentrically Rotating Flasks Used for Dispersant Effectiveness Testing

The evaluation of dispersant effectiveness used for oil spills is commonly done using tests conducted in laboratory flasks. We used a Hot Wire Anemometer (HWA) to characterize mixing dynamics in the Swirling Flask (SF) and the Baffled Flask (BF), the latter is being considered by the EPA to replace the prior to test dispersant effectiveness in the laboratory. Five rotation speeds of the orbital shaker carrying the flasks were considered, Ω = 50, 100, 150, 175 and 200 rpm. The radial and azimuthal water speeds were measured for each Ω. It was found that the flow in the SF is, in general, two-dimensional changing from horizontal at low Ω to axi-symmetric at high Ω. The flow in the BF appeared to be three-dimensional at all rotation speeds. This indicates that the BF is more suitable for representing the (inherently) 3-D flow at sea. In the SF, the speeds and energy dissipation rates ɛ increased gradually as the rotation speed increased. Those in the BF increased sharply at rotation speeds greater than 150 rpm. At 200 rpm, the Kolmogorov scale (i.e., size of smallest eddies) was about 250 and 50 μm in the SF and BF, respectively. Noting that the observed droplet sizes of dispersed oils range from 50 to 400 μm (hence most of it is less than 250 μm), one concludes that the mixing in the SF (even at 200 rpm) is not representative of the vigorous mixing occurring at sea.     

吸附铅、镉固定化细菌胞壁多糖小球包埋条件的优化选择

细菌已广泛应用于重金属废水的处理,多糖则是细胞壁的主要成分,并通过螯合作用吸附重金属,而固定化技术具有处理效率高,生产成本低等优势。采用正交实验法,以聚乙烯醇和海藻酸钠为包埋剂,同时添加活性炭,硅藻土等对细菌胞壁多糖进行固定化,并以吸附铅、镉能力为主要考察指标,同时从机械强度、传质性、耐酸性等方面综合考虑,选择最优化的固定化小球最佳配方。结果表明,在聚乙烯醇、海藻酸钠、活性炭、硅藻土、多糖、二氧化硅和饱和硼酸中氯化钙的质量分数分别为10%、0.2%、1.5%、1.5%、0.8%、4%、3%,胶联时间为16h,己二胺浓度为0.06mol?L-1的条件下制得的固定化小球对铅、镉吸附的能力较强,并按照最佳配方进行了验证实验,对铅的吸附量达到4.4575μmol?g-1,对镉的吸附量达到4.1708μmol?g-1,机械强度、传质性和耐酸性都较好。     

大豆根系分泌物和根细胞壁对难溶性磷的活化

探讨了不同磷效率大豆品种根系细胞壁和根分泌物对难溶性铝磷的活化与吸收能力。结果表明，砂培条件下，磷高效品种(巴西10号)对难溶性铝磷的吸收显著高于磷低效品种(本地2号)。铝磷处理条件下，根系总表面积巴西10号是本地2号的131％，而钾磷处理二者没有明显差异。根系细胞壁对铝磷的活化表明，大豆苗期根系细胞壁对铝磷的活化量显著高于成熟期。苗期、成熟期巴西10号对铝磷的活化量为本地2号的119％、176％。不同栽培方式根系细胞壁对铝磷的活化量表现为水培大于砂培，水培条件下两个大豆基因型对铝磷的活化量没有差异。不同生育时期、栽培方式根分泌物对铝磷的活化量表现为，成熟期大于苗期，砂培大于水培。巴西10号根分泌物对铝磷的活化量比本地2号分别高出69．3％(成熟期)和40．1％(砂培)。上述研究结果表明，大豆根分泌物和根细胞壁对难溶性铝磷的溶解具有促进作用，有利于大豆对铝磷的吸收。     

The influence of high initial concentration aqueous-phase TCE on the performance of iron wall systems

Flow-through column tests were conducted to investigate the performance of iron wall remediation systems for the degradation of aqueous-phase trichloroethylene (TCE). Concentration profiles under steady-state transport conditions were generated by measuring TCE concentrations at sample ports located at various locations along the length of the column. The results indicated that a pseudo-first-order model is adequate at describing degradation kinetics for low initial TCE concentrations, but not for higher initial concentrations. The deviation from pseudo-first-order kinetics can be explained by interspecies competition for reactive sites between TCE and a dominant reaction product. A modification of the pseudo-first-order model that accounts for product interference predicts laboratory data for high initial concentration profiles, but deviates slightly as initial concentrations approach the solubility of TCE. The data clearly demonstrate the importance of accurately describing reaction kinetics for the purpose of designing iron wall treatment systems.     

采用大涡PIV研究Taylor-Couette流及其对混凝过程的影响

采用大涡PIV方法对Taylor-Couette流场的湍动能及湍动能耗散率进行了估算,并利用数值模拟对其进行验证,结合絮凝实验,综合对比速度矢量、湍动能分布、湍动能耗散率分布及对应流场中混凝过程的絮体图像,探究了湍动能与湍动能耗散率对絮凝效能的影响.结果表明,大涡PIV法与数值模拟在雷诺数较高的情况下有较好的一致性,且雷诺数越大一致性越好.在Taylor-Couette涡流场中,随着雷诺数的增大,湍动能与湍动能耗散率数值不断增大,且在流场中的分布由规律有序到紊乱最终趋于各向均匀一致.而混凝过程中湍动能与湍动能耗散率的数值大小及其在流场中的空间分布情况,均对产生絮体的大小和浊度去除率有较大影响.