Catalytic dechlorination of chlorophenols in water by palladium/iron

Three isomer chlorophenols, o-, m-, p-chlorophenol, were dechlorinated by palladium/iron powder in water through catalytic reduction. The dechlorinated reaction is believed to take place on the surface site of the catalyst in a pseudo-first-order reaction. The reduction product for all the three isomers is phenol. The dechlorination rate increases with increase of bulk loading of palladium due to the increase of both the surface loading of palladium and the total surface area. The molecular structure also has an effect on the dechlorination rate. For conditions with 0.048% Pd/Fe, the rate constants are 0.0215, 0.0155 and 0.0112 min-1 for o-, m-, p-chlorophenol, respectively. Almost complete dechlorination is achieved within 5 h.     

Sequential analysis of hair mercury levels in relation to fish diet of an Amazonian population, Brazil

Several studies in the Amazonian Basin have shown that riverine populations are exposed to methylmercury through fish consumption. It has been suggested that seasonal variations in hair mercury observed through sequential analyses may be related to the changes in fish species ingested by the local communities. The aim of the present study was to investigate the relationship between fish-eating practices and seasonal variation in mercury exposure. A group of 36 women from a village located on the banks of the Tapajós River, a major tributary of the Amazon, comprised the present study population. An interview-administered questionnaire was used to gather information on socio-demographic characteristics, fish-eating practices and other relevant information. The women also provided hair samples of at least 24 cm in length for mercury analysis. Hair total and inorganic mercury concentration was measured using a cold vapor atomic absorption analytical method. Trigonometric regression analysis was done to assess the seasonal variation of total mercury levels. Variations in inorganic mercury were examined by repeated measures analysis of variance, and analysis of contrast variable with a polynomial transformation. The results showed that hair mercury levels varied with the season. Higher levels were observed in months corresponding to the dry season, with lower levels in the rainy season. Herbivorous fish predominated the diet for 47.2% of the women during the dry season, but this rose to 72.2% during the rainy season. Those who reported eating fish daily had higher mercury levels in hair compared to those who only ate fish a few times per week. Retrospective mercury analyses, evaluated by the quantity of mercury present in each centimeter of hair, indicate that mean mercury level of the population decreased over the 2 years prior to the study. The percentage of inorganic mercury over the total mercury in hair increased towards the extremities of the hair strand. Higher percentages of inorganic mercury were found for the group who ate more fish (on a daily consumption basis). These results support the assumption that there are seasonal variations in methylmercury exposure and also a relationship between type of fish species consumed and the resulting hair mercury levels.     

The ecology of "fecal indicator" bacteria commonly found in pulp and paper mill water systems

Coliform bacteria have long been used to indicate fecal contamination of water and thus a health hazard. In this study, the in-mill water and external effluent treatment systems of seven typical Canadian pulp and paper mills were all shown to support the growth of numerous coliforms, especially Klebsiella Spp., Escherichia coli. Enterobacter spp., and Citrobacter spp. In all mills and most sampled locations, klebsiellas were the predominant coliforms. Although all but one of the mills had no sewage input and most disinfected their feed (input) water, all contained the most typical fecal indicator bacterium, E. coli. Many of the mill coliforms were classified as fecal coliforms by standard "MPN" and metabolic tests, but this was shown to be due to their thermotolerance, not their origin. Mill coliforms were shown not to be just simple transients from feedwater or furnish (wood), but to be continuously growing, especially in some of the primary clarifiers. Isolated mill coliforms grew very well on a sterilized raw combined mill effluent. The fecal streptococci (enterococci), alternative indicators of fecal health hazards, were common in all mills in the absence of sewage. Ten strains of E. coli isolated from four mills were all shown to be non-toxigenic strains of harmless serotypes. No salmonellas were found. Therefore, the use of total coliform, fecal coliform, enterococci, or E. coli counts as indicators of fecal contamination, and thus of health hazard in pulp and paper mill effluents or biosolids (sludges) known to be free of fecal input is invalid.     

A simple system to rapidly monitor activated sludge health and performance

A set of four assays designed to rapidly measure the health and biodegradative performance of pulp and paper mill activated sludges was developed. Three of the assays are specific oxygen uptake rates (SOURs) that measure the normal "working" aeration tank BOD (biochemical oxygen demand) removal rate (SOURAT), a near-maximum BOD removal rate (SOURNMAX), and a rate (SOURTOX) used in combination with the SOURNMAX to indicate the presence of toxic or inhibitory substances. The fourth assay is the specific adenosine triphosphate (SATP) content of the sludge, used as a measure of its viable cell content. Fresh biomass (sludge) samples from one laboratory reactor and four mill biotreatment systems were fed raw mill effluents and used to evaluate the four-assay set. The SOURAT values of all systems were 10-40% of their SOURNMAX values: thus the SOURAT:SOURNMAX ratios indicate that each system's free biodegradative capacity was far greater than its operating rate. It was demonstrated using phenol that the SOURNMAX:SOURTOX ratio can indicate the presence of substances toxic or inhibitory to the biomass. The results also indicated that the SOURNMAX is a much better indicator of improving or worsening sludge performance and capacity than the SOURAT. SATP was shown to be a useful monitor of the proportion of viable cells in an activated sludge and a toxicity indicator complementary to the SOURNMAX:SOURTOX ratio and similar in principle to the commercial Microtox toxicity test. This four-assay set was also applied to three practical situations: (a) at-mill monitoring of a biotreatment system; (b) effects of cold storage on biomass; and (c) effects of decreased BOD loading on biomass.     

Distribution of radiocaesium in an Austrian forest stand

Within an Austrian spruce stand, vertical distribution of radiocaesium in soil as well as 137Cs concentration in different forest ecosystem compartments including spruce and surface water were investigated 10 years after the Chernobyl accident. The total 137Cs inventory in the forest was estimated to be 46 kBq m-2 (ref. date: 86-05-01). From the collected data annual input rates via litterfall of 0.48% per year and output rates through waterflows of only 0.02% per year were derived. The results identify the high importance of forest soils as a sink for radiocaesium. The estimated ecological residence half-times turned out to be highest in the organic soil horizons (1-3 years per cm), whereas in mineral horizons the values decrease significantly. As a consequence, soil inventory represents more than 95% of the total, whereas only approximately 3.3% of the 137Cs inventory is stored in the living biomass of spruce trees and a further 0.5% in the phytomass of understorey vegetation.     

Accumulation of heavy metals and As in wetland birds in the area around Doñana National Park affected by the Aznalcollar toxic spill

The impact of the spill from the mine in Aznalcollar (Seville, Spain) on waterfowl in the Do?ana National Park is assessed. The concentrations of Cu, Pb, Cd, Zn nd As in the liver and eggs of 16 species of waterfowl found dead in the Park between April and November 1998 were determined. The highest levels were found for Zn, followed by Cu, Pb, Cd and As. The main parameters related to the accumulation of these elements in the waterfowl studied were species and trophic level. The other variables studied--distance from the spill, days of exposure, sex, size, and age--are important, although this depends on the element studied. Zn and Cu from the spill have entered the food chain of the aquatic birds studied, but Cd, Pb and As have not. There is currently no evidence to suggest that the trace element concentrations measured have reached toxic levels.     

黑龙江省电信运营企业精心为“两会”提供优质服务

2013年1月25-26日,黑龙江省人大第十二届一次会议和省政协第十一届一次会议相继在哈尔滨召开。黑龙江省电信运营企业精心做好通信保障工作并为"两会"提供优质服务。黑龙江联通充分发挥服务与业务优势,积极做好现场服务工作,在人大代表驻地设置了"联通业务展区",选派业务精、服务优的工作人员,为"两会"代表提供行业应用、iPhone5等多款终端业务演示、缴费售卡、免费无线上网等通     

浅论三螺杆泵的主、从螺杆的几何形状的数学表达与三维建模

简单阐明了螺杆泵设计中所遇到的密封问题,以及在PRO／E的状态下,建立螺杆横截面的齿形曲线,建立扫描的空间螺旋线,通过可变截面扫描建立三螺杆泵的螺杆三维模型。     

钍矿及其利用

钍矿床已为许多国家所了解,它赋存于各种地质环境中。本文作者试图在不考虑钍矿经济意义的前提下对其进行分类。赋存于火成岩、变质岩和沉积岩中的钍矿则根据其地质背景和主岩类型进一步细分。人们发现,重要的钍资源多与碳酸岩伴生(总探明资源的40％),并主要赋存在富含铌和稀土元素的岩石中。第二种重要类型是脉状矿床(占探明资源的31％)。钍既赋存于独立钍矿物中,也赋存于稀土矿物中。其次是砂矿,占探明资源的19％(未固结的海滩砂矿和固结的古砂矿)。在此类型中,含钍矿物(主要是独居石)可作为重矿物产品(锡石、钛铁矿等)的副产品进行回收。另一些矿床,如伟晶岩或碱性侵入岩钍矿,则不太重要。按照其经济重要性推测的顺序,钍矿床可分类如下:(1)未固结砂矿;(2)固结的古砂矿;(3)脉状;(4)碳酸岩。钍的世界年产总量估计为400t ThO_2,但目前仅利用了一小部分。如果应用更广泛(如以钍为燃料的核电站)而需求增加的话,则通过提取作为开采重矿物的副产品回收的独居石精矿能获得每年约2000tThO_2。     

金矿石、冰铜、焙烧产物及金矿物的~(197)Au穆斯堡尔谱的研究

引言金矿石通常含有金属金,金的含量从几个(10~(-6))到几十个(10~(-6))。提炼金的标准方法是用氰化物溶液萃取粉碎的矿石。氰化物与金属金发生反应生成Au(CN)_2~-,随后Au(CN)_2~-被吸附在木炭上。金极少以独立的金矿物形式产出,这类独立的金矿物多数是碲化物。然而在某些情况下,金存在于诸如毒砂或黄铁矿一