Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri-Columbia, USA; Williamson et al., Chemosphere (This issue--PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment. 相似文献
Use of biodiesel in diesel engine helps to reduce HC, CO, and smoke emissions due to their enormous oxygen content, whereas NOx emissions formed by Zeldovich mechanism shoot up. Implementation of Bharat Stage (BS) VI by April 2020 in India has created extreme pressure on automobile manufacturers to include after treatment technology in their systems. Selective catalytic reduction (SCR), a NOx control technology, is operated using aqueous urea solution as the reductant. There are several parameters that need to be monitored to enhance the NOx conversion efficiency of SCR retrofit. The uniformity index of ammonia, which determines the conversion efficiency, is greatly influenced by parameters like exhaust gas temperature, injection angle, injector position, mass flow rate, and SCR geometry. This paper considers two types of SCR design, namely SCR with and without mixer design and their impact on NOx reduction. The effect of mass flow rate on urea conversion in SCR design without mixer is 27%, but the impact is reduced greatly in SCR design with mixer with less than 2% variation. The UI resulting from different cases ranges from 0.59 to 0.83. Using Taguchi technique and CFD tool, the impact of parameters on both the SCR designs has been investigated and the optimum SCR design is reported.
Environmental Science and Pollution Research - This study aims to enhance the turbulence of direct injection (DI) diesel engine by modifying the inlet manifold design with an inclined nozzle-like... 相似文献
While reservoirs are constructed to regulate stream flows for several beneficial purposes including flood control, water supply, hydroelectric power, irrigation and low flow augmentation and to enhance water based recreation, they create problems of water quality that offer a new dimension to the task of efficient operation. Among other potential deleterious effects, thermal stratification in reservoirs inhibits mixing and causes a deterioration of dissolved oxygen levels in lower layers. Several investigators have examined the thermal properties of reservoirs and resultant effects upon dissolved oxygen and have suggested alternative schemes for alleviating detrimental effects (1,2,3,4,5). The objective of this paper is to outline a methodology for evaluating some of these alternatives in a river-reservoir system where downstream water quality control is one of several purposes to be served by the reservoir. 相似文献
ABSTRACT: Hierarchical diversity analysis of data on fish and aquatic insects showed that the component of diversity contributed by the species level was generally very small compared with the component at the generic level or with the total diversity. Very high rank correlations between generic diversity, in which genera were discriminated but not identified, and species diversity suggested that the purposes of environmental monitoring might best be served by working at the generic level rather than the species level. This is particularly true when an index of diversity is to be used as the major comparative and communicative tool. The savings of time and money could be appreciable. 相似文献
The complexity of fluvial systems necessitates interdisciplinary research in fluvial geomorphology and aquatic ecology to
develop a fundamental understanding of interconnections among biotic and abiotic aspects of these systems. Integrated knowledge
of this type is vital for environmental management of streams in human-dominated environments. A conceptual framework is presented
for integrating geomorphological and ecological research on streams in East Central Illinois, USA, a glaciated low-relief
agricultural landscape. The framework embodies a multiscale perspective in which a geomorphological conception of the fluvial
system is used to define a hierarchy of characteristic spatial scales for exploring important linkages between stream geomorphology
and aquatic ecology. The focus ecologically is on fish, because a rich body of historical information exists on fisheries
in East Central Illinois and because past work has suggested that availability of physical habitat is a major factor influencing
the community characteristics of fish in this human-altered environment. The hierarchy embodied in the framework includes
the network, link, planform, bar unit, bar element, and bedform/grain scales. Background knowledge from past research is drawn
upon to identify potential linkages between geomorphological and ecological conditions at each of these scales.
The conceptual framework is useful for guiding integrated ecogeomorphological research at specific scales and across different
scales. It also is helpful for illustrating how widespread human modification of streams has catastrophically altered the
scalar structure of fluvial systems in East Central Illinois. Knowledge emerging from the integrated research provides a basis
for environmental-management schemes directed toward stream naturalization. 相似文献