An improved activated carbon method to quantify dichlorodiphenyltrichloroethane (DDT) in surface water

Currently, South Africa is designing a strategy for surface water protection involving organic contaminants such as dichlorodiphenyltrichloroethane (DDT), which is currently used for malaria control in mosquito-infested areas. Here, we demonstrate the successful use of an improved activated carbon technique using dichloromethane instead of chloroform, and slower leaching rate of 15 mL/min to quantify DDT and its metabolites in surface water. The recovery tests for 2,4′DDT, 2,4′DDD, 2,4′DDE, and 4,4′DDT, 4,4′DDD, 4,4′DDE ranged from 75 to 84% and 87 to 96%, respectively (DDE: dichlorodiphenyldichloroethylene, DDD: dichlorodiphenyldichloroethane). The main advantages of this technique over conventional liquid–liquid extractions are reduced amount of organic solvent, little sample preparation, and larger sample throughput. Because activated charcoal is fairly cheap, the technique can be routinely used to quantify and monitor DDT and its metabolites in surface water samples.     

Spatio-temporal Analysis of Acute Admissions for Ischemic Heart Disease in NSW,Australia

The recently funded Spatial Environmental Epidemiology in New South Wales (SEE NSW) project aims to use routinely collected data in NSW Australia to investigate risk factors for various chronic diseases. In this paper, we present a case study focused on the relationship between social disadvantage and ischemic heart disease to highlight some of the methodological challenges that are likely to arise.     

GC/MS分析20种纺织品和消费品中禁止使用的胺类致癌物和印染处理废水的环境监测中出现的胺类致癌物

一些偶氮染料用于纺织品和其它材料会产生胺类致癌物,这类物质从两个途径危害健康:一是消费者直接接触产品,二是印染厂产生的废水及污泥对环境水的污染.德国已经禁止某些含有这种超过规定浓度限量的胺类染料货物进口,使用质谱(MS)方法分析测定其含量.在德国规定用6890气相色谱仪/5973质谱检测器检测有关纺织品和其它消费品中有害物质的浓度限量,这一规定很适宜而且优于其它方法,例如,使用脉冲不分流进样和质谱的SIM模式检测方法,其检测限(LOD)是5ng·ml-1(ppb),这样低的检测限为分析人员提供了很大的方便:可以检测出浓度样品的低限,或者不要使用繁琐的样品处理方法,可以节约劳力从而增加分析样品的数量,而且,可以达到低的LOD并改善了数据处理的能力,适合环境样品的分析,用以检测印染厂废水中的污染物.利用能力卓越的MSD Productivity ChemStation,可以打印出符合用户需要的分析报告.     

The investment climate for gold mining

This analysis compares the gold mining industry investment climate in the USA to the investment climate in Australia. These two major gold producing nation's industries share many similarities; in both the USA and Australia, there is evidence of a maturing gold mining industry. Each country has experienced a dramatic increase in gold production and, more recently, greater mining of refractory ore and development of more underground operations. In the 1980s both nations experienced a pronounced rationalization trend that consolidated some gold producing operations and eliminated others. Each country commands a disproportionately large share of exploration expenditures. Land access, a major concern in the USA, has also become a critical issue in Australia as well. For all their similarities, however, the two countries have differences that are significant enough to influence mining company investment decisions. This paper explores those differences and how they may affect the future course of these nations' gold mining industries. Both effective government policy making and corporate strategic planning will occupy a major role in the future course of the two nations' gold mining industries .     

Pulling up roots in the 1990s: Who's willing to relocate?

The purpose of this study was to develop a profile of employees in Fortune 500 companies who are willing to relocate. The profile was developed on a demographically diverse random sample of 827 employees from 20 Fortune 500 corporations, all of whom had moved at least once for their current employer. Employees who were most willing to relocate were younger, their incomes were lower, their career ambitions higher, and their spouses more willing than those who were less willing to relocate. These employees could be found in sales/marketing and production functions. Their attitudes toward moving were also favorable. The single most important predictor of willingness to relocate was spouse willingness to relocate. This result suggests strongly that in the 1990s, corporations are going to have to address the concerns of spouses, if married employees are going to remain mobile. The study also cautions corporations about the shortsightedness of thinking of spouse and dual career issues as ’women's issues‘ and assuming that females and minorities are unwilling to relocate.     

POLICY IMPACTS ON AGRICULTURAL IRRIGATION ELECTRICITY DEMAND IN THE COLUMBIA BASIN1

ABSTRACT: Accurately estimating the price elasticity of demand for irrigation electricity is important to major electricity suppliers such as the Bonneville Power Administration (BPA) of the Pacific Northwest. The BPA has a revenue maximization objective, and the elasticity of demand is central to its rate setting process. Several studies have attempted to estimate demand for irrigation electricity, but none has explicitly included federal agricultural policy and program variables. Tins paper discusses how agricultural programs may influence farmers irrigation decisions and thus their demand for irrigation electricity. It suggests that existing programs serve to make farmers more responsive to electricity rate increases than would otherwise be the case. Thus, studies that fail to include them may underestimate the responsiveness of farmers to electricity rate increases.     

Effects of ethanol addition on micellar solubilization and plume migration during surfactant enhanced recovery of tetrachloroethene

Alcohol addition has been suggested for use in combination with surfactant flushing to enhance solubilization kinetics and permit density control of dense non-aqueous phase liquid (DNAPL)-laden surfactant plumes. This study examined the effects of adding ethanol (EtOH) to a 4% Tween 80 (polyoxyethylene (20) sorbitan monooleate) solution used to flush tetrachloroethene (PCE)-contaminated porous media. The influence of EtOH concentration, subsurface layering and scale on flushing solution delivery and PCE recovery was investigated through a combination of experimental and mathematical modeling studies. Results of batch experiments demonstrated that the addition of 2.5%, 5% and 10% (wt.) EtOH incrementally increased the PCE solubilization capacity and viscosity of the surfactant solution, while reducing solution density from 1.002 to 0.986 g/cm3. Effluent concentration data obtained from one-dimensional (1-D) column experiments were used to characterize rate-limited micellar solubilization of residual PCE, which was strongly dependent upon flow velocity and weakly dependent upon EtOH concentration. Two-dimensional (2-D) box studies illustrated that minor differences (0.008 g/cm3) between flushing and resident solution density can strongly influence surfactant front propagation. A two-dimensional multiphase simulator, MISER, was used to model the influence of EtOH composition on the aqueous flow field and PCE mass recovery. The ability of the numerical simulator to predict effluent concentrations and front propagation was demonstrated for both 1-D columns and 2-D boxes flushed with EtOH-amended Tween 80 solutions. Results of this study quantify the potential influence of alcohol addition on surfactant solution properties and solubilization capacity, and demonstrate the importance of considering small density variations in remedial design.     

An evaluation of electrode insertion techniques for measurement of redox potential in estuarine sediments

E(h) measurements by electrodes are commonly used to characterize redox status of sediments in freshwater, marine and estuarine studies, due to the relative ease and rapidity of data collection. In our studies of fine-grained estuarine seabeds, we observed that E(h) values measured in intact sediment cores were influenced by different electrode insertion techniques. Sediment E(h) measurements generated via lateral insertion of platinum electrodes through silicone-filled ports in acrylic cores were systematically more positive (on the order of 10-100 mV) than profiles generated via vertical insertion of platinum electrodes downward through the sediment-water interface of the same cores. A review of the literature indicated that while researchers routinely use both insertion techniques to measure E(h), no discrepancy in output has previously been reported. We discuss the results of three experiments conducted to determine if the discrepancy in output was caused by electrode poisoning by sulfides during the stepwise vertical insertion technique, or was caused by contact of the electrode with the silicone plug during the lateral insertion technique. We conclude that contact between the platinum surface of the electrode and the silicone plug biases the E(h) measurements, resulting in erroneously positive E(h) values. Insertion of electrodes into sediment through silicone plugs produced E(h) values that were an average of 105.6 mV (+/-10.4 SE) more positive than values generated upon electrode insertion directly into sediment. Thus, we recommend against using an insertion technique where the platinum electrode remains in contact with the silicone plug, as this method results in misclassification of sediment redox state and estimated depth of the redoxcline.     

Entrapment and dissolution of DNAPLs in heterogeneous porous media

Two-dimensional multiphase flow and transport simulators were refined and used to numerically investigate the entrapment and dissolution behavior of tetrachloroethylene (PCE) in heterogeneous porous media containing spatial variations in wettability. Measured hydraulic properties, residual saturations, and dissolution parameters were employed in these simulations. Entrapment was quantified using experimentally verified hydraulic property and residual saturation models that account for hysteresis and wettability variations. The nonequilibrium dissolution of PCE was modeled using independent estimates of the film mass transfer coefficient and interfacial area for entrapped and continuous (PCE pools or films) saturations. Flow simulations demonstrate that the spatial distribution of PCE is highly dependent on subsurface wettability characteristics that create differences in PCE retention mechanisms and the presence of subsurface capillary barriers. For a given soil texture, the maximum and minimum PCE infiltration depth was obtained when the sand had intermediate (an organic-wet mass fraction of 25%) and strong (water- or organic-wet) wettability conditions, respectively. In heterogeneous systems, subsurface wettability variations were also found to enhance or diminish the performance of soil texture-induced capillary barriers. The dissolution behavior of PCE was found to depend on the soil wettability and the spatial PCE distribution. Shorter dissolution times tended to occur when PCE was distributed over large regions due to an increased access of flowing water to the PCE. In heterogeneous systems, capillary barriers that produced high PCE saturations tended to exhibit longer dissolution times.     

Photochemically induced formation of the "Al13" tridecameric polycation in the presence of Fe(III) and organic acids

We found that light-induced Fe(III) reduction associated with the oxidation of a simple hydroxy-carboxylic acid (lactate) caused the formation of the AlO4Al12(OH)24(H2O)12 polycation ("Al13"). Initial conditions were a lactate:Al:Fe ratio of 1:0.76:0.11 in a partially neutralized solution. Base was added rapidly and no Al13 was detected in samples kept in the dark. With exposure to light, Fe(III) reduction was rapid and Fe(II) reached a maximum within 1 day. After the maximum, steady-state Fe(II) declined from 54% to 43% over eight days. During this same time period, the lactate concentration fell to 2% of the original, pH rose from 4.05 to 4.46, and the Al13 detectable by 27Al NMR increased to 2.3 mmol l(-1) (51% of the total solution Al). The formation of Al13 is attributed to the pH rise resulting from the removal of the organic acid buffer. Similar photo-induced chemical changes occur in natural waters and may promote the formation of Al13, conditions permitting.