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481.
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483.
Effects of aeration method and aeration rate on greenhouse gas emissions during composting of pig feces in pilot scale 总被引:8,自引:0,他引:8
The aim of this study was to uncover ways to mitigate greenhouse gas(GHG) emissions and reduce energy consumption during the composting process. We assessed the effects of different aeration rates(0, 0.18, 0.36, and 0.54 L/(kg dry matter(dm)·min)) and methods(continuous and intermittent) on GHG emissions. Pig feces and corn stalks were mixed at a ratio of 7:1. The composting process lasted for 10 weeks, and the compost was turned approximately every 2 weeks. Results showed that both aeration rate and method significantly affected GHG emissions. Higher aeration rates increased NH3 and N2O losses,but reduced CH4 emissions. The exception is that the CH4 emission of the passive aeration treatment was lower than that of the low aeration rate treatment. Without forced aeration,the CH4 diffusion rates in the center of the piles were very low and part of the CH4 was oxidized in the surface layer. Intermittent aeration reduced NH3 and CH4 losses, but significantly increased N2 O production during the maturing periods. Intermittent aeration increased the nitrification/denitrification alternation and thus enhanced the N2 O production. Forced aeration treatments had higher GHG emission rates than the passive aeration treatment. Forced aeration accelerated the maturing process, but could not improve the quality of the end product. Compared with continuous aeration, intermittent aeration could increase the O2 supply efficiency and reduced the total GHG emission by 17.8%, and this reduction increased to 47.4% when composting was ended after 36 days. 相似文献
484.
485.
Targeting Ecosystem Features for Conservation: Standing Crops in the Florida Everglades 总被引:10,自引:0,他引:10
Andrew M. Turner Joel C. Trexler § C. Frank Jordan † Sarah J. Slack ¶ Pamela Geddes John H. Chick William F. Loftus‡ 《Conservation biology》1999,13(4):898-911
Abstract: The Everglades in southern Florida, U.S.A., is a major focus of conservation activities. The freshwater wetlands of the Everglades do not have high species richness, and no species of threatened aquatic animals or plants live there. We have, however, identified a distinctive ecological feature of the Everglades that is threatened by canal construction, draining, and nutrient enrichment from agricultural runoff. Compared to values reported from other freshwater systems, standing stocks of periphyton in relatively undisturbed areas of the Everglades were unusually high, and standing stocks of invertebrates and fish were unusually low. Averaging data gathered from nine sites and five sampling periods spanning 1 year, we found that periphyton standing crop was 88.2 g/m2 (ash-free dry mass), invertebrate standing stock was 0.64 g/m2 (dry mass), and fish standing stock was 1.2 g/m2 (dry mass of large and small species combined). We found that fish standing stocks were much higher in phosphorus-enriched sites than in nearby reference sites but that invertebrate standing stocks were similar in enriched and reference sites. Our results support the notion that oligotrophy is at least partially responsible for the low standing stocks of fish, but they also suggest that species interactions and a paucity of deep-water refugia are important. Anthropogenic eutrophication in Everglades marshes will lead to the loss of distinctive ecosystem features. A focus on species richness and "hot spots" of threatened species provides no basis for conservation of ecosystems like the Everglades. If oligotrophic ecosystems often have low species richness, they will be underrepresented in preservation networks based on some common criteria for establishing conservation priorities. 相似文献
486.
Deborah A. Hutchinson Alan H. Savitzky Akira Mori Jerrold Meinwald Frank C. Schroeder 《Chemoecology》2008,18(3):181-190
Summary.
Rhabdophis tigrinus obtains defensive steroids (bufadienolides) from its diet and sequesters those compounds in specialized structures on its
neck known as nuchal glands. Hatchling snakes lacking these steroids must acquire them from toads consumed as prey. Here we
show that females provision bufadienolides to their offspring in amounts correlated to the quantity in their own nuchal glands;
thus, chemically protected mothers produce defended offspring. Bufadienolides can be provisioned to embryos via deposition
in yolk and by transfer across the egg membranes within the oviducts. Maternally provisioned bufadienolides persist in the
nuchal glands of juvenile snakes from the time of hatching in late summer until the following spring, when toads of ingestible
size become abundant. Therefore, maternal provisioning may provide chemical protection from predators for young R. tigrinus in the absence of dietary sources of bufadienolides. 相似文献
487.
Eisner T Schroeder FC Snyder N Grant JB Aneshansley DJ Utterback D Meinwald J Eisner M 《Chemoecology》2008,18(2):109-119
Summary. Beetles of the family Lycidae have long been known to be chemically protected. We present evidence that North American species
of the lycid genera Calopteron and Lycus are rejected by thrushes, wolf spiders, and orb-weaving spiders, and that they contain a systemic compound that could account,
at least in part, for this unacceptability. This compound, a novel acetylenic acid that we named lycidic acid, proved actively
deterrent in feeding tests with wolf spiders and coccinellid beetles. Species of Lycuscommonly figure as models of mimetic associations. Among their mimics are species of the cerambycid beetle genus Elytroleptus, remarkable because they prey upon the model lycids. We postulated that by doing so Elytroleptus might incorporate the lycidic acid from their prey for their own defense. However, judging from analytical data, the beetles
practice no such sequestration, explaining why they remain relatively palatable (in tests with wolf spiders) even after having
fed on lycids. Chemical analyses also showed the lycids to contain pyrazines, such as were already known from other Lycidae,
potent odorants that could serve in an aposematic capacity to forestall predatory attacks.
David Utterback: Deceased 相似文献
488.
Jensen Frank Nielsen Rasmus Meilby Henrik 《Environmental Economics and Policy Studies》2023,25(2):161-204
Environmental Economics and Policy Studies - In this paper, we investigate the economically optimal regulation of aquaculture production. The time between releasing and harvesting fish (rotation... 相似文献
489.
Frank M. Hauser Tim Metzner Thorsten Rößler Michael Pütz Steffen Krause 《Environmental Forensics》2019,20(1):13-25
The entry of illegally discharged waste into the sewage system can cause serious damage to sewage pipes and harm the public domain. Besides industrial and communal sources, discharges from clandestine laboratories are of special forensic interest. Aim of this study is to investigate the possibility to detect clandestine discharges of possibly hazardous waste directly at the point of discharge. Tests were performed at a facility where real wastewater was pumped in a controlled way through an open sewage pipe above ground. Chloride, ammonia, pH and conductivity electrodes were investigated for their ability to detect discharges of different types of waste. Waste samples were diluted up to 50 times in a static wastewater environment and pH, conductivity and chloride electrodes were able to distinguish all waste dilutions from blank wastewater. These three electrodes were then used for dynamic tests by placing them inside flowing sewage water and discharging different types of liquid waste ten meters upstream of them. Parameters of the waste discharges like volume, time interval and speed of discharge were varied and the responses of the electrodes were collected. The dynamic tests showed that these three electrodes were able to pick up different waste discharges in a real wastewater environment. It was found that a high sampling rate of the sensors would be required to connect a certain discharge to a specific household connection. These findings highlight the possibility to locate illegal discharges, coming from a variety of sources, using the waste discharge itself. 相似文献
490.
This study seeks to advance our understanding of the leadership consequences that may ensue when supervisors and their teams have similar versus differing orientations toward the past. Integrating a leader–team fit perspective with functional leadership theory, we cast incongruence between supervisor and team past temporal focus as a key antecedent of supervisors' active (i.e., task-oriented and relationship-oriented) and passive (i.e., laissez-faire) leadership behaviors toward the team. We tested our hypotheses in a team-level study that included a field sample of 84 supervisors and their teams using polynomial regression and response surface analyses. Results illustrated that supervisors demonstrated more task-oriented and relationship-oriented leadership when supervisors' and their team's past temporal focus were incongruent rather than aligned. Furthermore, in situations of supervisor–team congruence, supervisors engaged in less task-oriented and relationship-oriented leadership and more laissez-faire leadership with higher (rather than lower) levels of supervisor and team past temporal focus. In sum, these findings support a complex (mis)fit model such that supervisors' attention to the past may hinder their productive leadership behaviors in some team contexts but not in others. Hence, this research advances a novel, multiple-stakeholder perspective on the role of both supervisors' and their team's past temporal focus for important leadership behaviors. 相似文献