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261.
Abdul G.?LiewEmail author Azni?Idris Abdul A.?Samad Calvin H.K.?Wong Mohd S.?Jaafar Aminuddin M.?Baki 《Journal of Material Cycles and Waste Management》2004,6(1):41-47
Bricks produced from sewage sludge in different compositions were investigated. Results of the tests indicated that the sludge proportion is a key factor in determining the brick quality. Increasing the sludge content results in a decrease in brick shrinkage, bulk density, and compressive strength. Brick weight loss on ignition was mainly due to the contribution of the contained organic matter from the sludge being burnt off during the firing process, as well as inorganic substances found in both clay and sludge. The physical, mechanical, and chemical properties of the bricks that were supplemented with various proportions of dried sludge from 10 to 40wt% and generally complied with the General Specification for Brick as per the Malaysian Standard MS 7.6:1972, which dictates the requirements for clay bricks used in walling in general. A standard leaching test method also showed that the leaching of metals from the bricks is very low. 相似文献
262.
Hesseln H Loomis JB González-Cabán A Alexander S 《Journal of environmental management》2003,69(4):359-368
We use a travel cost model to test the effects of wild and prescribed fire on visitation by hikers and mountain bikers in New Mexico. Our results indicate that net benefits for mountain bikers is $150 per trip and that they take an average of 6.2 trips per year. Hikers take 2.8 trips per year with individual net benefits per trip of $130. Both hikers' and mountain bikers' demand functions react adversely to prescribed burning. Net benefits for both groups fall as areas recover from prescribed burns. Because both visitation and annual recreation benefits decrease to these two types of visitors, this gives rise to multiple use costs associated with prescribed burning. With respect to wildfire, hikers and mountain bikers both exhibit decreased visitation as areas recover from wildfires, however, only hikers indicate an increase in per trip net benefits. Bikers' demand effectively drops to zero. These results differ from previous findings in the literature and have implications for efficient implementation of the National Fire Plan and whether prescribed burning is a cost effective tool for multiple use management of National Forests. Specifically, that fire and recreation managers cannot expect recreation users to react similarly to fire across recreation activities, or different geographic regions. What is cost effective in one region may not be so in another. 相似文献
263.
Vellidis G Smith MC Leibowitz SG Ainslie WB Pruitt BA 《Environmental management》2003,31(2):0301-0312
In a climate of limited resources, it is often necessary to prioritize restoration efforts geographically. The synoptic approach
is an ecologically based tool for geographic prioritization of wetland protection and restoration efforts. The approach was
specifically designed to incorporate best professional judgment in cases where information and resources are otherwise limited.
Synoptic assessments calculate indices for functional criteria in subunits (watersheds, counties, etc.) of a region and then
rank the subunits. Ranks can be visualized in region-scale maps which enable managers to identify areas where efforts optimize
functional performance on a regional scale. In this paper, we develop a conceptual model for prioritizing watersheds whose
wetlands can be restored to reduce total sediment yield at the watershed outlet. The conceptual model is designed to rank
watersheds but not individual wetlands within a watershed. The synoptic approach is valid for applying the sediment yield
reduction model because there is high demand for prioritizing disturbed wetlands for restoration, but there is limited, quantitative,
accurate information available with which to make decisions. Furthermore, the cost of creating a comprehensive database is
prohibitively high. Finally, because the model will be used for planning purposes, and, specifically, for prioritizing based
on multiple decisions rather than optimizing a single decision, the consequence of prioritization errors is low. Model results
cannot be treated as scientific findings. The conclusions of an assessment are based on judgement, but this judgement is guided
by scientific principles and a general understanding of relevant ecological processes. The conceptual model was developed
as the first step towards prioritizing of wetland restoration for sediment yield reduction in US EPA Region 4. 相似文献
264.
Various approaches have been used to classify large geographical areas into smaller regions of similar water quality or extrapolate
water-quality data from a few streams to other unmonitored streams. A combination of some of the strengths of existing techniques
is used to develop a new approach for these purposes. In this new approach, referred to here as SPARTA (SPAtial Regression-Tree
Analysis), environmental characteristics for each monitored stream are first quantified using a Geographic Information System
(GIS) and then regression-tree analysis is used to determine which characteristics are most statistically important in describing
the distribution of a specific water-quality constituent. GIS coverages of only the most statistically significant environmental
characteristics are then used to subdivide the area of interest into relatively homogeneous environmental water-quality zones.
Results from the regression-tree analysis not only define the most important environmental characteristics, but also describe
how to subdivide the coverage of the specific characteristic (for example, areas with <26% or ≥26% soil clay content). The
resulting regionalization scheme is customized for each water-quality constituent based on the environmental characteristics
most statistically related to that constituent. SPARTA was used to delineate areas of similar phosphorus, nitrogen, and sediment
concentrations (by including land-use characteristics) and areas of similar potential water quality (by excluding land-use
characteristics). The SPARTA approach reduced the variability in water-quality concentrations (phosphorus, total nitrogen,
Kjeldahl nitrogen, and suspended sediment) within similarly classified zones from that obtained using the US Environmental
Protection Agency's nutrient ecoregions. 相似文献
265.
EMMC process for combined removal of organics, nitrogen and an odor producing substance 总被引:2,自引:0,他引:2
In order to improve the process performance regarding the removal of organics, nitrogen, and an odor-causing compound (sulfide) contained in domestic wastewater, an entrapped-mixed-microbial cell (EMMC) with and without humic substances for both fixed and moving carrier reactors and conventional suspended growth culture (i.e. conventional activated sludge process) were investigated simultaneously. Both synthetic (simulated to the organics concentration of general domestic sewage) and actual domestic wastewater were investigated under operational conditions of 12 h of hydraulic retention time (HRT) with 1 h of aeration and 1 h of non-aeration, and 6 h of HRT with continuous aeration, at a room temperature of 25 +/- 2 degrees C. It was found that entrapping humic substances in the EMMC carriers had no impact on the removal of organics, nitrogen, and the odor-producing compound. Additionally, the performance of the EMMC moving carrier system for the removal of these pollutants is similar to that of the EMMC fixed carrier system. In general, the EMMC associated systems which provide high solids retention time achieve a better removal of chemical oxygen demand (COD), nitrogen, and the odor-producing substance than the suspended growth system for both HRTs of 6 h (continuous aeration) and 12 h (1 h of aeration and 1 h of non-aeration). Both the fixed and moving carrier EMMC processes, therefore, have the potential for improvement or replacement of the existing conventional activated sludge process with regard to improving the effluent qualities (such as COD, nitrogen and odor-producing compound) for reuse/disposal. 相似文献
266.
Fuzzy cognitive mapping was used to develop a participatory ecosystem management plan for Uluabat Lake, Turkey. Interviews
were conducted with stakeholders belonging to six different groups. Lake pollution was the most central and most mentioned
variable for stakeholders. Stakeholder groups agree that lake pollution is negatively affecting ecosystem health and thereby
local economies. Thus, reducing lake pollution was chosen as the overall goal for the management plan. Possible ways to reduce
lake pollution and increase ecosystem health were seen differently by the different groups. Hunters, factory managers, NGO
personnel, and local people thought industry was the main cause of lake pollution, while officials from the government and
local municipalities thought roads and urban development contributed the most to lake pollution. Generally the stakeholder
groups did not perceive their own actions as affecting the lake as strongly as other groups thought. For example, factory
managers viewed factory pollution as negatively affecting the lake but less strongly than the other groups did. According
to policy option simulations, reducing lake pollution had positive effects on all variables, especially fish, birds, animal
husbandry, irrigation, agriculture, and the ecological balance of the lake. Results of this analysis were used to facilitate
meetings among stakeholder groups and to develop a participatory ecosystem management plan. The analysis was useful for pointing
out the similarities as well as the differences among the groups. It also helped the facilitators understand the focus of
each stakeholder group and enabled them to suggest activities in which each group would want to participate. 相似文献
267.
A GIS Model of Subsurface Water Potential for Aquatic Resource Inventory,Assessment, and Environmental Management 总被引:4,自引:0,他引:4
Biological, chemical, and physical attributes of aquatic ecosystems are often strongly influenced by groundwater sources. Nonetheless, widespread access to predictions of subsurface contributions to rivers, lakes, and wetlands at a scale useful to environmental managers is generally lacking. In this paper, we describe a neighborhood analysis approach for estimating topographic constraints on spatial patterns of recharge and discharge and discuss how this index has proven useful in research, management, and conservation contexts. The Michigan Rivers Inventory subsurface flux model (MRI-DARCY) used digital elevation and hydraulic conductivity inferred from mapped surficial geology to estimate spatial patterns of hydraulic potential. Model predictions were calculated in units of specific discharge (meters per day) for a 30-m2-cell raster map and interpreted as an index of potential subsurface water flux (shallow groundwater and event through-flow). The model was evaluated by comparison with measurements of groundwater-related attributes at watershed, stream segment, and local spatial scales throughout Lower Michigan (USA). Map-based predictions using MRI-DARCY accounted for 85% of the observed variation in base flow from 128 USGS gauges, 69% of the observed variation in discharge accrual from 48 river segments, and 29% of the residual variation in local groundwater flux from 33 locations as measured by hyporheic temperature profiles after factoring out the effects of climate. Although it does not incorporate any information about the actual water table surface, by quantifying spatial variation of key constraints on groundwater-related attributes, the model provides strata for more intensive study, as well as a useful spatial tool for regional and local conservation planning, fisheries management, wetland characterization, and stream assessment. 相似文献
268.
A relative significance factor (f
i
) of an impact category is the external weight of the impact category. The objective of this study is to propose a systematic
and easy-to-use method for the determination of f
i
. Multiattribute decision-making (MADM) methods including the analytical hierarchy process (AHP), the rank-order centroid
method, and the fuzzy method were evaluated for this purpose. The results and practical aspects of using the three methods
are compared. Each method shows the same trend, with minor differences in the value of f
i
. Thus, all three methods can be applied to the determination of f
i
. The rank order centroid method reduces the number of pairwise comparisons by placing the alternatives in order, although
it has inherent weakness over the fuzzy method in expressing the degree of vagueness associated with assigning weights to
criteria and alternatives. The rank order centroid method is considered a practical method for the determination of f
i
because it is easier and simpler to use compared to the AHP and the fuzzy method. 相似文献
269.
270.
The hydrogeomorphic (HGM) approach to wetland classification and functional assessment is becoming more widespread in the
United States but its use has been limited by the length of time needed to develop appropriate data sets and functional assessment
models. One particularly difficult aspect is the transferability among geographic regions of specific models used to assess
wetland function. Sharing of models could considerably shorten development and implementation of HGM throughout the United
States and elsewhere. As hydrology is the driving force behind wetland functions, we assessed the comparability of hydrologic
characteristics of three HGM subclasses (slope, headwater floodplain, mainstem floodplain) using comparable long-term hydrologic
data sets from different regions of the United States (Ridge and Valley Province in Pennsylvania and the Willamette Valley
in Oregon). If hydrology by HGM subclass were similar between different geographic regions, it might be possible to more readily
transfer extant models between those regions. We found that slope wetlands (typically groundwater-driven) had similar hydrologic
characteristics, even though absolute details (such as depth of water) differed. We did not find the floodplain subclasses
to be comparable, likely due to effects of urbanization in Oregon, regional differences in soils and, perhaps, climate. Slight
differences in hydrology can shift wetland functions from those mediated by aerobic processes to those dominated by anaerobic
processes. Functions such as nutrient cycling can be noticeably altered as a result. Our data suggest considerable caution
in the application of models outside of the region for which they were developed. 相似文献