The influence of ambient water quality on the settlement of barnacles and the green alga Enteromorpha spp. to an artificial substratum in the estuaries of Sydney, Australia, was investigated to test the efficacy of both groups of organisms as indicators of changes in water quality due to urban stormwater runoff and/or sewage overflows. Wooden settlement panels were immersed for 4 months on 17 occasions between 1996 and 2005 at 11 locations known to vary in water-quality parameters (conductivity, total uncombined ammonia, oxidised nitrogen, total nitrogen, filterable phosphorus, total phosphorus, faecal coliforms and chlorophyll-a) and ambient meteorological conditions (total rainfall, maximum rainfall). Water-quality data were collected during the time that the settlement panels were deployed. Cover of barnacles was highly variable among locations (range 1.2?C55.2%). Hierarchical partitioning found that chlorophyll-a, total phosphorus and total nitrogen had significant independent positive effects on barnacle cover. Together, these variables explained 26% of the variation in barnacle cover. Mean cover of Enteromorpha spp., however, did not vary significantly among locations suggesting that other potentially more important factors are influencing its settlement and growth. The results of this study suggest that barnacle cover is likely to be a useful indicator of some components of water quality. 相似文献
137Cs was dispersed globally by cold war activities and, more recently, by the Chernobyl accident. Engineered extraction of 137Cs from soils and groundwaters is exceedingly difficult. Because the half-life of 137Cs is only 30.2 years, remediation might be more effective (and less costly) if 137Cs bioavailability could be demonstrably limited for even a few decades by use of a reactive barrier. Essentially permanent isolation must be demonstrated in those few settings where high nuclear level wastes contaminated the environment with 135Cs (half-life 2.3 x 10(6) years) in addition to 137Cs. Clays are potentially a low-cost barrier to Cs movement, though their long-term effectiveness remains untested. To identify optimal clays for Cs retention, Cs desorption was measured for five common clays: Wyoming Montmorillonite (SWy-1), Georgia Kaolinites (KGa-1 and KGa-2), Fithian Illite (F-Ill), and K-Metabentonite (K-Mbt). Exchange sites were pre-saturated with 0.16 M CsCl for 14 days and readily exchangeable Cs was removed by a series of LiNO3 and LiCl washes. Washed clays were then placed into dialysis bags and the Cs release to the deionized water outside the bags measured. Release rates from 75 to 139 days for SWy-1, K-Mbt and F-Ill were similar; 0.017% to 0.021% sorbed Cs released per day. Both kaolinites released Cs more rapidly (0.12% to 0.05% of the sorbed Cs per day). In a second set of experiments, clays were Cs-doped for 110 days and subjected to an extreme and prolonged rinsing process. All the clays exhibited some capacity for irreversible Cs uptake. However, the residual loading was greatest on K-Mbt (approximately 0.33 wt.% Cs). Thus, this clay would be the optimal material for constructing artifical reactive barriers. 相似文献
This article describes how Boeing'S program to conduct environmental assessments has developed since its inception five years ago, and has contributed to the company'S overall Quality Improvement process. 相似文献
ABSTRACT: An extensive group of datasets was analyzed to examine factors affecting widths of streams and rivers. Results indicate that vegetative controls on channel size are scale dependent. In channels with watersheds greater than 10 to 100 km2, widths are narrower in channels with thick woody bank vegetation than in grass lined or nonforested banks. The converse is true in smaller streams apparently due to interactions between woody debris, shading, understory vegetation, rooting characteristics, and channel size. A tree based statistical method (regression tree) is introduced and tested as a tool for identifying thresholds of response and interpreting interactions between variables. The implications of scale dependent controls on channel width are discussed in the context of stable channel design methods and development of regional hydraulic geometry curves. 相似文献
Objectives: The aim of this study was to estimate the potential effectiveness of an in-vehicle automatic collision notification (ACN) system in reducing all road crash fatalities in South Australia (SA).
Methods: For the years 2008 to 2009, traffic accident reporting system (TARS) data, emergency medical services (EMS) road crash dispatch data, and coroner's reports were matched and examined. This was done to initially determine the extent to which there were differences between the reported time of a fatal road crash in the mass crash data and the time EMS were notified and dispatched. In the subset of fatal crashes where there was a delay, injuries detailed by a forensic pathologist in individual coroner's reports were examined to determine the likelihood of survival had there not been a delay in emergency medical assistance.
Results: In 25% (N = 53) of fatalities in SA in the period 2008 to 2009, there was a delay in the notification of the crash event, and hence dispatch of EMS, that exceeded 10 min. In the 2-year crash period, 5 people were likely to have survived through more prompt crash notification enabling quicker emergency medical assistance. Additionally, 3 people potentially would have survived if surgical intervention (or emergency medical assistance to sustain life until surgery) occurred more promptly.
Conclusions: The minimum effectiveness rate of an ACN system in SA with full deployment is likely to be in the range of 2.4 to 3.8% of all road crash fatalities involving all vehicle types and all vulnerable road users (pedestrians, cyclists, and motorcyclists) from 2008 to 2009. Considering only passenger vehicle occupants, the benefit is likely to be 2.6 to 4.6%. These fatality reductions could only have been achieved through earlier notification of each crash and their location to enable a quicker medical response. This might be achievable through a fully deployed in-vehicle ACN system. 相似文献
The present experimental work investigates the use of ethyne gas in biodiesel-fueled diesel engine at different flow rate of 1, 2, and 3 L/min and is compared with diesel operation. This work is aimed to examine the outcome of ethyne gas by dual-fuel operation on emission characteristics of neat biodiesel-fueled stationary diesel engine. The oil derived from mustard seeds are employed as a source for biodiesel. The work was carried out at 2100 rpm (speed) and at an optimal compression ratio of 17. Based on the outcome of this investigation, the maximum reduction in hydrocarbon (25.1%), carbon monoxide (17.24%), and smoke emission (24.8%) was observed for biodiesel–ethyne at 3 L/min than the neat biodiesel. However, NOx emissions were found to be 15.8% higher for ethyne–biodiesel fueling at 3 L/min owing to increase in combustion gas temperature than neat biodiesel. 相似文献
ABSTRACT Emissions of carbon monoxide (CO) from motor vehicles cause several hundred accidental fatal poisonings annually in the United States. The circumstances that could lead to fatal poisonings in residential settings with motor vehicles as the source of CO were explored. The risk of death in a garage (volume = 90 m3) and a single-family dwelling (400 m3) was evaluated using a Monte Carlo simulation with varying CO emission rates and ventilation rates. Information on emission rates was obtained from a survey of motor vehicle exhaust gas composition under warm idle conditions in California, and information on ventilation rates was obtained from a summary of published measurements in the U.S. housing stock. The risk of death ranged from 16 to 21% for a 3-hr exposure in a garage to 0% for a 1-hr exposure in a house. Older vehicles were associated with a disproportionately high risk of death. Removing all pre-1975 vehicles from the fleet would reduce the risk of death by one-fourth to two-thirds, depending on the exposure scenario. Significant efforts have been made to control CO emissions from motor vehicles with the goal of reducing CO concentrations in outdoor air. Substantial public health benefit could also be obtained if vehicle control measures were designed to take account of acute CO poisonings explicitly. 相似文献