Investor demand and spot commodity prices: Reply

In a recent article (Tilton et al., 2011), we argue that even when investor stocks are declining an increase in investor demand can cause a commodity's price to rise, a conclusion that is both contrary to conventional wisdom and counter-intuitive. In his comment on our article, Olle Östensson (2011) challenges this finding. After assessing his concerns in this reply, we maintain that our original finding is valid: investor demand can be driving commodity prices higher even when investor stocks are falling.     

载铁活化天然沸石处理高氟地下水

采用氯化铁改性天然沸石进行地下水除氟效果的研究,考察了地下水中4种阴离子Cl-、HCO3-、SO24-和PO34-对该改性沸石除氟效果的影响,并分析了其除氟机理和表面成分。研究结果表明,对于初始氟浓度不同的水样,随着阴离子浓度的增加,吸附剂对氟的去除率逐渐下降。Cl-对吸附剂除氟效果影响较小,氟去除率降低较慢;随着HCO3-浓度的增大(由100 mg/L到1 000 mg/L),水样pH由8.42缓慢升高到9.52,而氟去除率则由70.36%缓慢下降到56.73%(2mg/L);SO24-及PO34-对改性沸石除氟效果影响较大,氟去除率降低较快,且PO34-的影响大于SO24-。可以得到载铁活化天然沸石对4种阴离子的吸附顺序为:PO34->SO24->HCO3->Cl-。     

滤筒除尘器脉冲清灰动态分析

对常用规格φ325 mm×660 mm滤筒采用普通喷吹孔和诱导喷嘴进行脉冲清灰实验研究,测试滤筒侧壁压力峰值和压力上升速度,并使用高速动态分析仪拍摄清灰时粉尘从滤筒壁面脱落的动态过程。实验证明了滤筒脉冲清灰时,粉尘的脱落是从滤筒上部到下部依次进行,滤筒侧壁第一个压力峰值、最大压力峰值和压力上升速度对清灰效果均有影响,且脉冲气流形成的第一个侧壁压力峰值对滤筒的第一次冲击对清灰来说起着决定性的作用,回流气流形成的侧壁压力峰值作用较弱。而压力上升速度不能完全作为评价清灰效果好坏的指标。实验证明,采用诱导喷嘴可以改善滤筒内部流场,提高清灰效率。     

110离子交换树脂担载催化剂净化低浓度PH3

以110丙烯酸系阳离子交换树脂作为载体,Pd(Ⅱ)-Cu(Ⅱ)为主催化剂,制成担载型过渡金属催化剂。以N₂为载气,对反应温度、氧含量、催化剂用量3个因素进行催化氧化净化低浓度PH₃研究。实验结果表明,在氧含量为3.7%,温度为72℃时,催化剂的催化活性较高;PH₃净化效率随催化剂用量增大而提高。在优化后的实验条件下,考察催化剂以CO为载气时催化剂对PH₃的净化效率,虽然净化效果比以N₂为载气时差,但反应较稳定,持续时间较长,有较好的抗杂毒性,且催化剂具有再生性能。     

Dynamics of mercury fluxes and their controlling factors in large Hg-polluted floodplain areas

Environmental pollution by mercury (Hg) is a considerable environmental problem world-wide. Due to the occurrence of Hg volatilization from their soils, floodplains can function as an important source of volatile Hg. Soil temperature and soil water content related to flood dynamics are considered as important factors affecting seasonal dynamics of total gaseous mercury (TGM) fluxes. We quantified seasonal variations of TGM fluxes and conducted a laboratory microcosm experiment to assess the effect of temperature and moisture on TGM fluxes in heavily polluted floodplain soils. Observed TGM emissions ranged from 10 to 850 ng m⁻² h⁻¹ and extremely exceeded the emissions of non-polluted sites. TGM emissions increased exponentially with raised air and soil temperatures in both field (R²: 0.49-0.70) and laboratory (R²: 0.99) experiments. Wet soil material showed higher TGM fluxes, whereas the role of soil water content was affected by sampling time during the microcosm experiments.     

Environmental fate of Ra in cation-exchange regeneration brine waste disposed to septic tanks, New Jersey Coastal Plain, USA: migration to the water table

Fate of radium (Ra) in liquid regeneration brine wastes from water softeners disposed to septic tanks in the New Jersey Coastal Plain was studied. Before treatment, combined Ra (²²⁶Ra plus ²²⁸Ra) concentrations (maximum, 1.54 Bq L⁻¹) exceeded the 0.185 Bq L⁻¹ Maximum Contaminant Level in 4 of 10 studied domestic-well waters (median pH, 4.90). At the water table downgradient from leachfields, combined Ra concentrations were low (commonly ≤0.019 Bq L⁻¹) when pH was >5.3, indicating sequestration; when pH was ≤5.3 (acidic), concentrations were elevated (maximum, 0.985 Bq L⁻¹ - greater than concentrations in corresponding discharged septic-tank effluents (maximum, 0.243 Bq L⁻¹)), indicating Ra mobilization from leachfield sediments. Confidence in quantification of Ra mass balance was reduced by study design limitations, including synoptic sampling of effluents and ground waters, and large uncertainties associated with analytical methods. The trend of Ra mobilization in acidic environments does match observations from regional water-quality assessments.     

中国城市土地市场有效性的实证研究

将有效市场假说应用于我国城市土地市场中,利用全国土地交易价格指数,采用序列相关检验、游程检验和方差比检验3种方法分别对我国城市土地市场的弱式有效性进行了实证检验,一致得出我国城市土地市场尚未达到弱式有效的结论.提出了对策建议:①营造公平、公开、公正的土地市场环境,发挥市场在配置土地资源方面的基础性作用.②打破对一级土地市场的垄断,构建城乡一体化的土地市场.③构建完善的土地市场指数系统,强化信息基础平台建设.     

Wild fire impact on copper, zinc, lead and cadmium distribution in soil and relation with abundance in selected plants of Lamiaceae family from Vidlic Mountain (Serbia)

Fire has been considered as an improving factor in soil quality, but only if it is controlled. Severe wild fire occurred in the summer 2007 on the Vidlic Mountain (Serbia) overspreading a huge area of meadows and forests.Main soil characteristics and content of heavy metals (Cu, Pb, Cd, Zn) in different fractions obtained after sequential extraction of soil from post-fire areas and from fire non disturbed areas were studied. In four plant species of Lamiaceae family (Ajuga genevensis L., Lamium galeobdolon (L.) L., Teucrium chamaedrys L., Acinos alpinus (L.) Moench.), that grow in typical habitats of the mountain, distribution of heavy metals in aerial parts and roots was investigated too.For all samples from post-fire area cation exchange capacity and soil organic matter content are increased while rH is decreased. Fire caused slightly increased bioavailability of the observed metals but more significant rise happened in metal amounts bound to oxides and organics. The plants showed variable behavior. T. chamaedrys collected on the post-fire area contained elevated concentrations of all analyzed metals. A. alpinus showed higher phytoaccumulation for Zn and Cd, while the other two plant species for Pb and Cd in the post-fire areas.     

强碱性阴离子交换树脂对苦味酸的吸附与解吸性能

研究了强碱性阴离子交换树脂(简称树脂)对苦味酸的吸附与解吸性能,探讨了吸附的热力学和动力学特性以及吸附机理.实验结果表明:树脂对苦味酸的吸附量随吸附温度升高而增大;溶液pH为2.7 ～12.0时树脂的苦味酸吸附量最大,稳定在120 mg/g以上;树脂对苦味酸的等温吸附规律符合Freundlich模型,相关系数大于0.9...     

吡虫啉光降解产物中阴离子的毛细管电泳分析

本文建立了吡虫啉光降解产物中无机阴离子的毛细管电泳分析方法,背景电解质采用铬酸钠和十四烷基三甲基溴化铵,２５４ｎｍ紫外间接检测,在选定条件下,光降解产物中各种阴离子在３ｍｉｎ内达到完全分离;