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991.
Sanphoti N Towprayoon S Chaiprasert P Nopharatana A 《Journal of environmental management》2006,81(1):27-35
In order to increase methane production efficiency, leachate recirculation is applied in landfills to increase moisture content and circulate organic matter back into the landfill cell. In the case of tropical landfills, where high temperature and evaporation occurs, leachate recirculation may not be enough to maintain the moisture content, therefore supplemental water addition into the cell is an option that could help stabilize moisture levels as well as stimulate biological activity. The objectives of this study were to determine the effects of leachate recirculation and supplemental water addition on municipal solid waste decomposition and methane production in three anaerobic digestion reactors. Anaerobic digestion with leachate recirculation and supplemental water addition showed the highest performance in terms of cumulative methane production and the stabilization period time required. It produced an accumulated methane production of 54.87 l/kg dry weight of MSW at an average rate of 0.58 l/kg dry weight/d and reached the stabilization phase on day 180. The leachate recirculation reactor provided 17.04 l/kg dry weight at a rate of 0.14l/kg dry weight/d and reached the stabilization phase on day 290. The control reactor provided 9.02 l/kg dry weight at a rate of 0.10 l/kg dry weight/d, and reached the stabilization phase on day 270. Increasing the organic loading rate (OLR) after the waste had reached the stabilization phase made it possible to increase the methane content of the gas, the methane production rate, and the COD removal. Comparison of the reactors' efficiencies at maximum OLR (5 kgCOD/m(3)/d) in terms of the methane production rate showed that the reactor using leachate recirculation with supplemental water addition still gave the highest performance (1.56 l/kg dry weight/d), whereas the leachate recirculation reactor and the control reactor provided 0.69 l/kg dry weight/d and 0.43 l/kg dry weight/d, respectively. However, when considering methane composition (average 63.09%) and COD removal (average 90.60%), slight differences were found among these three reactors. 相似文献
992.
Geographical areas constitute the basic implementation locus for integrated coastal zone management strategies and activities.
Because the definition of territorial planning objectives may be affected by socioeconomic and environmental characteristics,
one of the main steps in the process involves dividing the coast into homogeneous environmental management units (HEMUs).
This article presents a general and simple method for regionalizing the landside of a coastal zone into HEMUs and illustrates
it through application to the Catalan coast. Socioeconomic and natural (biophysical) subsystems were selected as the most
appropriate dimensions of the regionalization process. Dimensions were described using 11 spatial themes, which were managed
in a geographic information system environment that proved to be an adequate tool for the purpose. A final coastal zone map
of four classes of HEMUs connected to local administrative units was obtained, and because it reflects the current natural
and socioeconomic dynamics, it can be considered as an initial step in the planning process for the Catalan coast. Although
the proposed method was developed based on the characteristics of the Catalan coast, it is general enough to be adapted and
applied to most developed or developing coastal areas. 相似文献
993.
Bryan BA 《Environmental management》2006,37(1):126-140
The desire to capture natural regions in the landscape has been a goal of geographic and environmental classification and ecological land classification (ELC)
for decades. Since the increased adoption of data-centric, multivariate, computational methods, the search for natural regions
has become the search for the best classification that optimally trades off classification complexity for class homogeneity.
In this study, three techniques are investigated for their ability to find the best classification of the physical environments
of the Mt. Lofty Ranges in South Australia: AutoClass-C (a Bayesian classifier), a Kohonen Self-Organising Map neural network,
and a k-means classifier with homogeneity analysis. AutoClass-C is specifically designed to find the classification that optimally
trades off classification complexity for class homogeneity. However, AutoClass analysis was not found to be assumption-free
because it was very sensitive to the user-specified level of relative error of input data. The AutoClass results suggest that
there may be no way of finding the best classification without making critical assumptions as to the level of class heterogeneity
acceptable in the classification when using continuous environmental data. Therefore, rather than relying on adjusting abstract
parameters to arrive at a classification of suitable complexity, it is better to quantify and visualize the data structure
and the relationship between classification complexity and class homogeneity. Individually and when integrated, the Self-Organizing
Map and k-means classification with homogeneity analysis techniques also used in this study facilitate this and provide information
upon which the decision of the scale of classification can be made. It is argued that instead of searching for the elusive
classification of natural regions in the landscape, it is much better to understand and visualize the environmental structure
of the landscape and to use this knowledge to select the best ELC at the required scale of analysis. 相似文献
994.
Great Basin Land Management Planning Using Ecological Modeling 总被引:1,自引:1,他引:0
This report describes a land management modeling effort that analyzed potential impacts of proposed actions under an updated
Bureau of Land Management Resource Management Plan that will guide management for 20 years on 4.6 million hectares in the
Great Basin ecoregion of the United States. State-and-transition models that included vegetation data, fire histories, and
many parameters (i.e., rates of succession, fire return intervals, outcomes of management actions, and invasion rates of native
and nonnative invasive species) were developed through workshops with scientific experts and range management specialists.
Alternative restoration scenarios included continuation of current management, full fire suppression, wildfire use in designated fire use zones, wildfire use in resilient vegetation types only, restoration with a tenfold budget increase, no restoration treatments, and no livestock grazing. Under all the scenarios, cover of vegetation states with native perennial understory declined and was replaced by tree-invaded
and weed-dominated states. The greatest differences among alternative management scenarios resulted from the use of fire as
a tool to maintain native understory. Among restoration scenarios, only the scenario assuming a tenfold budget increase had
a more desirable outcome than the current management scenario. Removal of livestock alone had little effect on vegetation
resilience. Rather, active restoration was required. The predictive power of the model was limited by current understanding
of Great Basin vegetation dynamics and data needs including statistically valid monitoring of restoration treatments, invasiveness
and invasibility, and fire histories. The authors suggest that such computer models can be useful tools for systematic analysis
of potential impacts in land use planning. However, for a modeling effort to be productive, the management situation must
be conducive to open communication among land management agencies and partner entities, including nonprofit organizations. 相似文献
995.
996.
A Regional Classification Scheme for Estimating Reference Water Quality in Streams Using Land-Use-Adjusted Spatial Regression-Tree Analysis 总被引:1,自引:0,他引:1
Various approaches are used to subdivide large areas into regions containing streams that have similar reference or background
water quality and that respond similarly to different factors. For many applications, such as establishing reference conditions,
it is preferable to use physical characteristics that are not affected by human activities to delineate these regions. However,
most approaches, such as ecoregion classifications, rely on land use to delineate regions or have difficulties compensating
for the effects of land use. Land use not only directly affects water quality, but it is often correlated with the factors
used to define the regions. In this article, we describe modifications to SPARTA (spatial regression-tree analysis), a relatively
new approach applied to water-quality and environmental characteristic data to delineate zones with similar factors affecting
water quality. In this modified approach, land-use-adjusted (residualized) water quality and environmental characteristics
are computed for each site. Regression-tree analysis is applied to the residualized data to determine the most statistically
important environmental characteristics describing the distribution of a specific water-quality constituent. Geographic information
for small basins throughout the study area is then used to subdivide the area into relatively homogeneous environmental water-quality
zones. For each zone, commonly used approaches are subsequently used to define its reference water quality and how its water
quality responds to changes in land use. SPARTA is used to delineate zones of similar reference concentrations of total phosphorus
and suspended sediment throughout the upper Midwestern part of the United States. 相似文献
997.
Long-term water quality records for assessing natural variability, impact of management, and that guide regulatory processes to safeguard water resources are rare for California oak woodland rangelands. This study presents a 20-yr record (1981-2000) of nitrate-nitrogen (NO(3)-N) and suspended sediment export from a typical, grazed oak woodland watershed (103 ha) in the northern Sierra Nevada foothills of California. Mean annual precipitation over the 20-yr period was 734 mm yr(-1) (range 366-1205 mm yr(-1)). Mean annual stream flow was 353 mm y(-1) (range 87-848 mm yr(-1)). Average annual stream flow was 48.1 +/- 16% of precipitation. Mean annual NO(3)-N export was 1.6 kg ha(-1) yr(-1) (range 0.18-3.6 kg ha(-1) yr(-1)). Annual NO(3)-N export significantly (P < 0.05) increased with increasing annual stream flow and precipitation. Mean daily NO(3)-N export was 0.004 kg ha(-1) d(-1) (range 10(-5) to 0.55 kg ha(-1) d(-1)). Mean annual suspended sediment export was 198 kg ha(-1) yr(-1) (range 23-479 kg ha(-1) yr(-1)). There was a positive relationship (P < 0.05) between annual suspended sediment export, annual stream flow and precipitation. Mean daily suspended sediment export was 0.54 kg ha(-1) d(-1) (range 10(-4) to 155 kg ha(-1) d(-1)). Virtually no sediment was exported during the dry season. The large variation in daily and annual fluxes highlights the necessity of using long-term records to establish quantitative water quality targets for rangelands and demonstrates the difficulty of designing a water quality monitoring program for these ecosystems. 相似文献
998.
It is common practice to repeatedly apply dairy manure to the same fields. To accurately assess the total plant availability of manure nutrients, it is necessary to account for the nutrients remaining in soil from previous manure applications. A field experiment studying manure nitrogen (N) uptake by corn (Zea mays L.) was conducted from 1998 to 2003 on a Plano silt loam (fine-silty, mixed, mesic, Typic Argiudolls). Plots received two rates of semisolid manure either every year, every 2 yr, or every 3 yr to estimate first-, second-, and third-year dairy manure N residuals. Residual manure N availability was estimated from single and multiple manure applications using (i) the fertilizer N equivalence method, (ii) the apparent recovery (difference) method, (iii) relative effectiveness method, and (iv) recovery of (15)N-labeled manure. Second-year availabilities after a single manure application using the fertilizer equivalence, difference, and relative effectiveness methods were estimated to be 12, 8, and 4% of total manure N applications, respectively. Estimates of third-year availability by these methods were 3, 1, and 5%, respectively. Measurement of (15)N recovered from labeled manure was 6 and 2% in the second and third year, respectively. Fertilizer equivalence, difference, and relative effectiveness methods showed great year to year variability, reducing the confidence in the residual manure N availability estimates by these methods, but using (15)N-labeled manures reduced variability substantially. Based on this and other studies, we suggest that second- and third-year residual N availability from a single application of semisolid dairy manure would be 9 to 12%, and 3 to 5% of the original manure N application, respectively. 相似文献
999.
Wu Y Lerner DN Banwart SA Thornton SF Pickup RW 《Journal of environmental quality》2006,35(6):2021-2025
The fermentation process is an important component in the biodegradation of organic compounds in natural and contaminated systems. Comparing with terminal electron-accepting processes (TEAPs), however, research on fermentation processes has to some extent been ignored in the past decades, particularly on the persistence of fermentation process in the presence of toxic organic pollutants. Both field and laboratory studies, presented here, showed that microbial processes in a groundwater-based system exhibited a differential inhibitory response to toxicity of phenolic compounds from coal tar distillation, thus resulting in the accumulation of volatile fatty acids (VFAs) and hydrogen. This indicated that fermentation processes could be more resistant to phenol toxicity than the subsequent TEAPs such as methanogenesis and sulfate reduction, thus providing us with more options for enhancing bioremediation processes. 相似文献
1000.
Estimating plant-available nitrogen release from manures, composts, and specialty products 总被引:1,自引:0,他引:1
Gale ES Sullivan DM Cogger CG Bary AI Hemphill DD Myhre EA 《Journal of environmental quality》2006,35(6):2321-2332
Recent adoption of national rules for organic crop production have stimulated greater interest in meeting crop N needs using manures, composts, and other organic materials. This study was designed to provide data to support Extension recommendations for organic amendments. Specifically, our objectives were to (i) measure decomposition and N released from fresh and composted amendments and (ii) evaluate the performance of the model DECOMPOSITION, a relatively simple N mineralization/immobilization model, as a predictor of N availability. Amendment samples were aerobically incubated in moist soil in the laboratory at 22 degrees C for 70 d to determine decomposition and plant-available nitrogen (PAN) (n = 44), and they were applied preplant to a sweet corn crop to determine PAN via fertilizer N equivalency (n = 37). Well-composted materials (n = 14) had a single decomposition rate, averaging 0.003 d(-1). For uncomposted materials, decomposition was rapid (>0.01 d(-1)) for the first 10 to 30 d. The laboratory incubation and the full-season PAN determination in the field gave similar estimates of PAN across amendments. The linear regression equation for lab PAN vs. field PAN had a slope not different from one and a y-intercept not different than zero. Much of the PAN released from amendments was recovered in the first 30 d. Field and laboratory measurements of PAN were strongly related to PAN estimated by DECOMPOSITION (r(2) > 0.7). Modeled PAN values were typically higher than observed PAN, particularly for amendments exhibiting high initial NH(4)-N concentrations or rapid decomposition. Based on our findings, we recommend that guidance publications for manure and compost utilization include short-term (28-d) decomposition and PAN estimates that can be useful to both modelers and growers. 相似文献