A comparison of the carbon balances of a natural lake (L. Orträsket) and a hydroelectric reservoir (L. Skinnmuddselet) in northern Sweden

Carbon balances were calculated for the summer stratification period of 2001 for the hydroelectric reservoir L. Skinnmuddselet (created in 1989) and the natural L. Ortr?sket, and estimated on annual basis for both lakes. The reservoir and the lake have similar chemical characteristics and are located in adjacent catchments in the northern part of Sweden. Our main hypothesis was that the CO(2) production and emissions from the reservoir, L. Skinnmuddselet, would be greater than in the natural L. Ortr?sket, due to the decomposition of flooded vegetation and peat. The carbon balances showed that the total production of CO(2) per unit lake surface area during the summer was very similar in the natural lake and the reservoir (31.3 g Cm(-2) in L. Ortr?sket and 25.3 g Cm(-2) in L. Skinnmuddselet). The sediments were the major CO(2) source in the reservoir, while most of the mineralization in the natural lake occurred in the water column. On annual basis the natural L. Ortr?sket produced and emitted more CO(2) per unit of lake surface area than the reservoir L. Skinnmuddselet since mineralization proceeded during winter when L. Skinnmuddselet was emptied for electricity production. Therefore, the potential for CO(2) emission was not greater in the reservoir than in the natural lake.     

Chlorination of model drinking water biofilm: implications for growth and organic carbon removal

The influence of chlorine on biofilm in low organic carbon environments typical of drinking water or industrial process water was examined by comparing biomass and kinetic parameters for biofilm growth in a chlorinated reactor to those in a non-chlorinated control. Mixed-population heterotrophic biofilms were developed in rotating annular reactors under low concentration, carbon-limited conditions (< 2 mg/L as carbon) using three substrate groups (amino acids, carbohydrates and humic substances). Reactors were operated in parallel under identical conditions with the exception that chlorine was added to one reactor at a dose sufficient to maintain a free chlorine residual of 0.09-0.15 mg/L in the effluent. The presence of free chlorine resulted in development of less biofilm biomass compared to the control for all substrates investigated. However, specific growth and organic carbon removal rates were on the average five times greater for chlorinated biofilm compared to the control. Observed yield values were less for chlorinated biofilm. Although chlorinated biofilm's specific organic carbon removal rate was high, the low observed yield indicated organic carbon was being utilized for purposes other than creating new cell biomass. The impacts of free chlorine on mixed-population biofilms in low-nutrient environments were different depending upon the available substrate. Biofilms grown using amino acids exhibited the least difference between control and chlorinated kinetic parameters; biofilm grown using carbohydrates had the greatest differences. These findings are particularly relevant to the fundamental kinetic parameters used in models of biofilm growth in piping systems that distribute chlorinated, low-carbon-concentration water.     

受控力机器人磨削过程中工件的烧伤和表面光洁度

本文研究了受控力条件下机器人砂轮磨削过程中工件的烧伤情况和表面光洁度。工件烧伤是由实际参与切削过程的磨粒的锋利程度逐渐降低而引起的。磨粒锋利程度的变化可以用平均摩擦系数和平均切削深度的变化进行间接监测。随着砂轮的磨损,这两个参数将逐渐减小。本文推导出的解析式可以用来预测受控力磨削过程中发生的烧伤情况。在上述条件下,使用经过仔细调节的PID控制器所得出的实验结果与预测结果十分吻合。实验结果还表明在连续磨削时表面光洁度将得到逐步改善。因此,我们试图根据砂轮切削效率的逐渐下降来解释和预测表面光洁度的变化的特点。这些关系可以用于实际优化机器人控制磨削过程。     

Continuous water treatment by adsorption and electrochemical regeneration

This study describes a process for water treatment by continuous adsorption and electrochemical regeneration using an air-lift reactor. The process is based on the adsorption of dissolved organic pollutants onto an adsorbent material (a graphite intercalation compound, Nyex^®1000) and subsequent electrochemical regeneration of the adsorbent leading to oxidation of the adsorbed pollutant. Batch experiments were carried out to determine the adsorption kinetics and equilibrium isotherm for adsorption of a sample contaminant, the organic dye Acid Violet 17. The adsorbent circulation rate, the residence time distribution (RTD) of the reactor, and treatment by continuous adsorption and electrochemical regeneration were studied to investigate the process performance. The RTD behaviour could be approximated as a continuously stirred tank. It was found that greater than 98% removal could be achieved for continuous treatment by adsorption and electrochemical regeneration for feed concentrations of up to 300 mg L⁻¹. A steady state model has been developed for the process performance, assuming full regeneration of the adsorbent in the electrochemical cell. Experimental data and modelled predictions (using parameters for the adsorbent circulation rate, adsorption kinetics and isotherm obtained experimentally) of the dye removal achieved were found to be in good agreement.     

Hybrid anion exchanger for trace phosphate removal from water and wastewater

Throughout recent decades, the wastewater treatment industry has identified the discharge of nutrients, including phosphates and nitrates, into waterways as a risk to natural environments due to the serious effects of eutrophication. For this reason, new tertiary treatment processes have abounded; these processes generally utilize physico-chemical and biological methods to remove nutrients from secondary wastewaters. The disadvantages of such methods involve larger reactor volumes, operating costs, and waste sludge production; furthermore, complete nutrient removal is unattainable due to thermodynamic and kinetic limitations. The subject study presents the development and performance of a new phosphate-selective sorbent, referred to as hybrid anion exchanger or HAIX. HAIX combines durability and mechanical strength of polymeric anion exchange resins with high sorption affinity of hydrated ferric oxide (HFO) toward phosphate. HAIX is essentially a polymeric anion exchanger within which HFO nanoparticles have been dispersed irreversibly. Laboratory studies show that HAIX selectively removes phosphate from the background of much higher concentrations of competing sulfate, chloride and bicarbonate anions due to the combined presence of Coulombic and Lewis acid-base interactions. Experimental results demonstrate that HAIX's phosphate-sulfate separation factor is over two orders of magnitude greater than that of currently available commercial ion exchange resins. Additionally, optimal HAIX performance occurs at typical secondary wastewater pH conditions i.e., around 7.5. HAIX is amenable to efficient regeneration and reuse with no noticeable loss in capacity.     

Comparative study of the temporal evolution of atmospheric lead deposition in Scotland and eastern Canada using blanket peat bogs

The temporal evolution of atmospheric lead deposition and its possible sources were assessed in eastern Canada and in western Scotland, using blanket peat bogs as geochemical archives. Short cores were taken from two remote sites located close to the sea. Significant lead enrichments in the upper layers at both sites reflect the increasing emission of lead into the atmosphere due to anthropogenic activities during the last century. At the Scottish site, a region under aeolian influence from Europe, anthropogenic derived lead could be recognized by the distinctive unradiogenic composition (206Pb/207Pb ratios down to approximately 1.115), being clearly different from the pre-industrial values (206Pb/207Pb approximately 1.166). In contrast, the lead pollution in eastern Canada (influenced by North American sources) is identified by a more radiogenic lead isotope composition (206Pb/207Pb ratios up to approximately 1.199) compared to preindustrial values (206Pb/207Pb approximately 1.161). Emission inventories and isotope characteristics suggest that industrial (coal burning, mining) and traffic (leaded gasoline) outputs are the most likely sources during the first and the second half of the 20th century, respectively, in both, western Scotland and eastern Canada alike. The Scottish record is in line with previous studies of past atmospheric lead deposition. However, the Canadian deposit suggests that the wind derived, pre-industrial lead, is less radiogenic as previously implied using sediment archives. These results are thus the first to report pre-industrial lead isotope ratios and concentrations of atmospheric derived aerosols in North America.     

Lead decline in the Indian environment resulting from the petrol-lead phase-out programme

Recently, the lead content of various environmental components has decreased in response to replacement of leaded petrol by unleaded petrol. In India, 15 research studies are here assessed with respect to lead concentrations in various environmental components during the leaded petrol phase (before 1996), the transitional phase (1996-2000) and the unleaded petrol phase (2000 onwards). The Ganga River Water exhibited a decrease in lead concentration from 18.0 microg/l in 1988 to 3.1 microg/l in 2001. In Lucknow urban centre, mean lead concentrations in the urban air decreased from 1.6 microg/m(3) in 1994 to 0.2 microg/m(3) in 2002. Lead concentrations in Dalbergia sissoo tree leaves also decreased from 18.7 microg/g dry wt. in 1994 to 8.3 microg/g dry wt. in 2004. Mean blood-lead levels of children from Mumbai, Chennai, Bangalore, Amritsar and Lucknow urban centres have fallen from 18.1 microg/dl in the leaded petrol phase to 12.1 microg/dl in the unleaded petrol phase. The petrol-lead phase-out effort in India has reduced lead concentrations in the various environmental components after 2000. It will help to reduce the exposure of millions of people to environmental lead.     

铬铁矿床地下开采的方向

顿河铬铁矿床,矿石储量巨大,品位高;但矿山地质条件复杂。因此,需要采用综合的方法选择和论证这种矿床的开采技术方案。目前,公司正在向地下开采过渡。“青年”矿井使用分段崩落法开采了第一批试验矿块。结果说明,由于矿体和围岩不够稳固,极不宜使用这种采矿法,需要迅速寻求有效的地下采矿法。哈萨克共和国科学院矿业研究所     

露天地下联合开采时露天开采的安全措施

克里沃罗格矿区中央采选公司开采铁石英岩的主要生产单位是1号和2号露天矿。在1号露天矿东部边坡,以地下法开采一组互相平行的矿体,矿体埋藏深度由几十米至1000米,厚度在80米以下,倾角50～70°(图1)。在2号露天矿范围内,在北部边坡不长的一段也进行地下开采。     

房柱法开采时回采巷道内的定向

房柱法开采时回采巷道中作业安全和地面的完整性,在很大程度上决定于房间矿柱形成的质量。经验表明,房间矿柱形成的质量既决定于矿山地质条件和生产技术因素,又决定于作业控制方法。房间矿柱形成的质量,由矿山测量队测定其在采矿巷道中相对固定的方向或根据某些测点测定其方向予以控制。矿山技术监督员给矿山测量员规定方向,用于标定工作面的中线,据以按凿岩爆破说明书布置炮孔和有效地控制回采矿房和矿柱的实际位置。开采厚度不大(在3～4m 以内)的矿体时,回采巷道中的方向用铅锤标定,而测点固定在巷道顶板上。回采矿房高度大于4～5m 时,测点的固定和铅锤的悬挂都很困难,因为完成这些作业需要使用专门的自行设备,因此只能用