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881.
882.
PCDDs/DF and Co-PCB (dioxin) formations were studied with ash from a newly developed gasification and melting process for
municipal solid waste. Ash samples were heated in a laboratory-scale fixed-bed reactor. Emphasis was placed on the effects
of the type and composition of ash, temperatures, gas residence time, and gaseous organic precursors. Investigations using
macroscopic and homologue distribution analyses led to the following conclusion. The ash from the gasification–melting process
had the ability to generate dioxins in flue gas. A possible carbon source is unburned carbon in the ash samples, although
this was very low (less than 0.01%). An experimental result that the level of dioxins generated from preheated fly ash obtained
from a conventional incinerator was much lower than that from nonheated fly ash supported this conclusion. Dioxin concentrations
obviously showed temperature dependence and peaked at 350°C. Dioxins formed in a gasification–melting process ash were readily
desorbed from the surface, probably because of the low carbon content of the ash. There was no experimental evidence that
gaseous organic precursors fed to the reactor generated dioxins. Therefore, an organic precursor was not essential for the
formation of dioxins. A good linear relationship obtained between PCDDs/DFs and gas residence time also supported the assumption.
Received: February 14, 2000 / Accepted: June 30, 2000 相似文献
883.
The ratio between (Ca +K +Mg) and Al in nutrientsolution has been suggested as a predictive tool forestimating tree growth disturbance. However, the ratiois unspecific in the sense that it is based on severalelements which are all essential for plant growth;each of these may be growth-limiting. Furthermore,aluminium retards growth at higher concentrations. Itis therefore difficult to give causal and objectivebiological explanations for possible growthdisturbances. The importance of the proportion ofbase-cations to N, at a fixed base-cation/Al ratio, isevaluated with regard to growth of Picea abies.The uptake of elements was found to be selective;nutrients were taken up while most Al remained insolution. Biomass partitioning to the roots increasedafter aluminium addition with low proportions of basecations to nitrogen. We conclude that the low growthrates depend on nutrient limitation in thesetreatments. Low growth rates in the high proportionexperiments may be explained by high internal Alconcentrations. The results strongly suggest thatgrowth rate is not correlated with the ratio in therooting medium and question the validity of usingratios as predictive tools for estimating forestdamage. We suggest that growth limitation of Picea abies in the field may depend on lowproportions of base cations to nitrate. It istherefore important to know the nutritional status ofthe plant material in relation to the growth potentialand environmental limitation to be able to predict andestimate forest damage. 相似文献
884.
Yukio Noma Sayuri Yamane Akiko Kida 《Journal of Material Cycles and Waste Management》2001,3(2):126-134
Adsorbable organic halides (AOX) and AOX formation potential (AOXFP) were investigated in 46 landfill lea-chates as potentially
toxic parameters. AOX in landfill leachate was within the range <10–2200 μg Cl/l, and AOXFP was within 51–15 000 μg Cl/l.
AOX and AOXFP correlated with chemical oxygen demand (COD). AOX discharge from closed landfills was generally lower than that
from operating landfills. The molar ratio of AOXFP/total organic carbon (TOC) suggested that organic compounds in a leachate
have a double bond every 15–190 carbons under the supposition that one chlorine would add to one double bond. The five landfills
discharging high-level AOXFP (>4000 μg Cl/l) were all landfills where sludge had been dumped. The removal efficiencies of
three parameters through leachate treatment processes were as follows: polychlorinated dibenzo-dioxins/dibenzo-furans (PCDDs/DFs)
> TOC > AOX. PCDDs/DFs were substantially removed at p.p.t. levels, while AOX was hardly removed at relatively low levels.
Received: February 14, 2000 / Accepted: January 9, 2001 相似文献
885.
G. Grabow D. C. Yoder C. R. Mote 《Journal of the American Water Resources Association》2000,36(3):549-566
ABSTRACT: A procedure using a simple, empirically‐based model that makes efficient use of available information has been developed for designing a ground water monitoring well network. A moving plume is described by siting wells in a sequential manner, relying upon two‐dimensional concentration data obtained from previously installed wells to determine the locations of future wells. Data sets from two well known, densely monitored natural gradient tracer studies were used to test the procedure. Plumes defined by all information in the original networks were compared to those defined by reduced networks designed by the new procedure. The new procedure tracked the plumes using only a portion of that information. The new procedure could have reduced the number of wells in the original tests by about 50 percent without appreciable loss of plume information as measured by plume location and extent and by tracer mass. 相似文献
886.
Mohamed Lahlou Dale Colyer 《Journal of the American Water Resources Association》2000,36(5):1003-1012
ABSTRACT: This study examines water consumption characteristics in Casablanca and analyzes approaches for sustainable water demand management. Research procedures involve the development and estimation of water demand models for the residential/commercial, industrial, and institutional sectors; forecasts of water demand to 2010; and simulation of the effects of a complex of water conservation methods on the forecasted demands. The results indicate that residential/commercial water demand is weakly responsive to price changes (elasticity =?0.448) while institutional water demand is slightly more responsive (elasticity =?0.648). The conservation approaches used in the simulations included public education, plumbing code revisions to require use of water conservation devices, leak detection and repair, pricing policy, metering, and pressure reduction. The results indicate that considerable saving in water use can be attained through a comprehensive water demand management program. 相似文献
887.
Joseph S. Stibrich Thomas J. Charles 《Journal of the American Water Resources Association》2000,36(6):1263-1269
ABSTRACT: This paper describes how a hydrologic model proved to be a valuable tool to help interested parties understand impacts to four threatened and endangered fish species in the Upper Colorado River. In 1994, the Ute Water Conservancy District initiated permitting and design of the Plateau Creek pipeline replacement. The project was considered a major Federal action and therefore subject to the National Environmental Policy Act. Under Section 7 of the Endangered Species Act, the U.S. Fish and Wildlife Service (USFWS) entered the process to develop a Biological Opinion (BO) and determined that the project could potentially impact the endangered fish in the 15‐mile reach of the Colorado River. The Section 7 consultation was directed by a Core Committee comprised of stakeholders in the Upper Colorado River watershed. Hydrologic modeling became the evaluation tool for comparing flow reductions to USFWS target recovery flows and defining make‐up flow requirements to meet those targets. The Colorado River Recovery Implementation Program was designated to provide the make‐up flows. The USFWS released a final BO in December 1997, approving diversions through 2015. An Environmental Impact Statement for the project was completed and the Record of Decision was issued by the Bureau of Land Management in early 1998. 相似文献
888.
889.
和田河年径流变化规律研究 总被引:15,自引:1,他引:14
根据和田河实测年径流资料,应用小波分析、R/S分析等多种方法,探讨了在气候变化和人类活动影响下,和田河年径流变化规律及其成因。结果表明,和田河年径流存在减少趋势,且具有一定的持续性。通过径流变化的影响因素分析表明,上游出山口处两支流的径流变化主要受气温升高的影响,下游入塔里木河处除受降水减少的影响外,主要是由于人类对水土资源开发进程的加快,人类活动是其径流变化的主要原因。 相似文献
890.
树舌灵芝多糖对肝纤维化大鼠的肝功能的影响 总被引:2,自引:0,他引:2
观察树舌灵芝多糖对肝纤维化大鼠的肝功能的影响.采用经典的四氯化碳肝纤维化模型,造模同时给予树舌灵芝多糖干预,4周后采血测血清AST、ALB、A/G、HDL,实验中观察大鼠的一般状况.树舌灵芝多糖能显著降低四氯化碳肝纤维化大鼠血清ALIT、Mb、A/G水平.在肝纤维化的病理进程中,采取树舌灵芝多糖进行干预,可改善大鼠肝功能.表3,参5. 相似文献