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71.
Sharma R Ryan K Hao X Larney FJ McAllister TA Topp E 《Journal of environmental quality》2011,40(1):199-205
Composting is the controlled biological decomposition of organic matter by microorganisms during predominantly aerobic conditions. It is being increasingly adopted due to its benefits in nutrient recycling, soil reclamation, and urban land use. However, it poses an environmental concern related to its contribution to greenhouse gas production. During composting, activities of methanogenic and methanotrophic communities influence the net methane (CH4) release into the atmosphere. Using quantitative polymerase chain reaction (qPCR), this study was aimed at assessing the changes in the methyl-coenzyme M reductase (mcrA) and particulate methane monooxygenase (pmoA) copy numbers for estimation of methanogenic and methanotrophic communities, respectively. Open-windrow composting of beef cattle (Bos Taurus L.) manure with temperatures reaching > 55 degrees C was effective indegrading commensal Escherichia coli within the first week. Quantification of community DNA revealed significant differences in mcrA and pmoA copy numbers between top and middle sections. Consistent mcrA copy numbers (7.07 to 8.69 log copy number g(-1)) were detected throughout the 15-wk composting period. However, pmoA copy number varied significantly over time, with higher values during Week 0 and 1 (6.31 and 5.41 log copy number g(-1), respectively) and the lowest at Week 11 (1.6 log copy number g(-1)). Net surface CH4 emissions over the 15-wk period were correlated with higher mcrA copy number. Higher net ratio of mrA: pmoA copy numbers was observed when surface CH4 flux was high. Our results indicate that mcrA and pmoA copy numbers vary during composting and that methanogen and methanotroph populations need to be examined in conjunction with net CH4 emissions from open-windrow composting of cattle feedlot manure. 相似文献
72.
Assessing Cd,Pb, Zn human bioaccessibility in smelter-contaminated agricultural topsoils (northern France) 总被引:5,自引:0,他引:5
Pelfrêne A Waterlot C Mazzuca M Nisse C Bidar G Douay F 《Environmental geochemistry and health》2011,33(5):477-493
The extractability of Cd, Pb, and Zn was investigated in contaminated agricultural topsoils located in an area highly affected
by the past atmospheric emissions of two smelters in northern France in order to assess their mobility and human bioaccessibility.
The determination of Cd, Pb, and Zn bioaccessibility (Unified Barge Method, in vitro test) was made to evaluate the absolute
trace element (TE) bioavailability. The results highlighted differences in bioaccessibility between Cd, Pb, and Zn (Cd > Pb > Zn).
The mean values of the bioaccessible fractions of Cd, Pb, and Zn during the gastric phase were 82, 55, and 33%, respectively,
of the pseudototal concentrations, whereas during the gastrointestinal phase, the bioaccessible fractions of metals decreased
to 45, 20, and 10%, respectively. Stepwise multiple regression analysis showed that human bioaccessibility was affected by
various physicochemical parameters (i.e., sand, carbonates, organic matter, assimilated P, free Al oxides, and pseudototal
Fe contents). Sequential extractions were performed as an indication of the TE availability in these soils. Cadmium occurred
in the more available fractions, Pb was mostly present as bound by oxides, and a significant contribution to the pseudototal
Zn concentration was defined as the unavailable residual form related to the crystalline structures of minerals. The concepts
of bioavailability and bioaccessibility are important for quantifying the risks associated with exposure to environmental
pollutants and providing more realistic information for human health. 相似文献
73.
Jelle S. van Zweden Christoph Grüter Sam M. Jones Francis L.W. Ratnieks 《Behavioral ecology and sociobiology》2011,65(6):1277-1282
Social insects need to defend their nest against robbery, parasitism and predation. The stingless bee Tetragonisca angustula is unique in that it has guards that hover near the nest entrance in addition to guards that stand at the entrance. We tested
both the general hypothesis that hovering guards increase the effectiveness with which flying intruders are detected and the
specific hypothesis that hovering guards improve the detection of workers of the obligate robber bee, Lestrimellita limao. In an intraspecific study comparing colonies, we found a strong positive relationship between the number of hovering guards
and the distance at which a dummy robber bee or L. limao worker, experimentally moved towards the nest entrance, was detected. These results were mirrored in an interspecific study
showing that four species of stingless bees with similar population colonies but which lacked hovering guards, detected L. limao only at the nest entrance, in contrast to T. angustula. In addition, we found that a greater number of attacks by guards occurred when dummies were impregnated with citral, a major
component of L. limao mandibular gland odour. Our results support the hypothesis that T. angustula hovering guards increase the detection perimeter for flying intruders, especially L. limao. 相似文献
74.
Francis J. Magilligan Keith H. Nislow 《Journal of the American Water Resources Association》2001,37(6):1551-1569
ABSTRACT: We analyzed the type of hydrologic adjustments resulting from flow regulation across a range of dam types, distributed throughout the Connecticut River watershed, using two approaches: (1) the Index of Hydrologic Alteration (IHA) and (2) log‐Pearson Type III flood frequency analysis. We applied these analyses to seven rivers that have extensive pre‐and post‐disturbance flow records and to six rivers that have only long post‐regulation flow records. Lastly, we analyzed six unregulated streams to establish the regional natural flow regime and to test whether it has changed significantly over time in the context of an increase in forest cover from less than 20 percent historically to greater than 80 percent at present. We found significant hydrologic adjustments associated with both impoundments and land use change. On average, maximum peak flows decrease by 32 percent in impounded rivers, but the effect decreases with increasing flow duration. One‐day minimum low flows increase following regulation, except for the hydro‐electric facility on the mainstem. Hydrograph reversals occur more commonly now on the mainstem, but the tributary flood control structures experience diminished reversals. Major shifts in flood frequency occur with the largest effect occurring downstream of tributary flood control impoundments and less so downstream of the mainstem's hydroelectric facility. These overall results indicate that the hydrologic impacts of dams in humid environments can be as significant as those for large, multiple‐purpose reservoirs in more arid environments. 相似文献
75.
Margaret J. Couvillon Francis L.W. Ratnieks 《Behavioral ecology and sociobiology》2008,62(7):1099-1105
In group-level recognition, discriminators use sensory information to distinguish group members and non-members. For example,
entrance guards in eusocial insect colonies discriminate nestmates from intruders by comparing their odour with a template
of the colony odour. Despite being a species-rich group of eusocial bees closely related to the honey bees, stingless bee
nestmate recognition is a relatively little-studied area. We studied Frieseomelitta varia, a common Brazilian species of stingless bee known as marmelada. By measuring the rejection rates of nestmate and non-nestmate
worker bees by guards, we were able to show that guards became significantly less accepting (from 91 to 46%) of nestmates
that had acquired odour cues from non-nestmate workers; however, guards did not become significantly more accepting (from
31 to 42%) of non-nestmates that had acquired equivalent amounts of odour cues from the guard’s nestmates. These data strongly
suggest that guards use an “undesirable–absent” system in recognition, whereby incoming conspecific workers are only accepted
if undesirable cues are absent, despite the presence of desirable cues. We suggest that an undesirable–absent system is adaptive
because robbing by conspecifics may be an important selective factor in F. varia, which would lead to selection for a non-permissive acceptance strategy by guards. 相似文献
76.
ADELEKE Olukunle Francis ZHOU Rui-min Zu Jian-hu Ekoko Bakambo Gracien 《环境科学学报(英文版)》2005,17(2):301-304
Electron beam was successfully used for the degradation of 2-chlorophenol (2-CP) and 4-chlorophenol (4-CP) in aqueous solutions in this research. The effect of radiation dose on substrate degradation and dechlorination of solutions with concentration of 50mg/L was investigated. The effect of initial concentration, pH and presence of oxygen was also investigated. The concentration of 2-CP and 4-CP remaining in solution after irradiation were measured by HPLC. The results showed that increased radiation dose led to increased degradation of the chlorophenols and increased CI^- yield. Deaeration was also found to significantly increase the rate of degradation of chlorphenols in water while degradation and dechlodnation under alkaline condition was lower than at low to neutral pH. 相似文献
77.
Larney FJ Olson AF Miller JJ DeMaere PR Zvomuya F McAllister TA 《Journal of environmental quality》2008,37(2):725-735
In the 1990s, restrictions on incineration encouraged the forest industry in western Canada to develop new uses for their wood residuals by product. One such use was as a replacement for cereal straw bedding in southern Alberta's beef cattle (Bos taurus) feedlot industry. However, use of carbon (C)-rich bedding, such as wood chips, had implications for subsequent composting of the feedlot manure, a practice that was being increasingly adopted. In a 3-yr study, we compared composting of wood chip-bedded manure (WBM) and barley (Hordeum vulgare L.) straw-bedded manure (SBM). There were no significant differences in temperature regimes of SBM and WBM, indicating similar rates of successful composting. Of 17 physical and chemical parameters, five showed significant (P < 0.10) differences due to bedding at the outset of composting (Day 0), and 11 showed significant differences at final sampling (Day 124). During composting (10 sampling times), seven parameters showed significant bedding effects, 16 showed significant time effects, and four showed a Bedding x Time interaction. Significantly lower (P < 0.10) losses of nitrogen (N) occurred with WBM (19%) compared with SBM (34%), which has positive implications for air quality and use as a soil amendment. Other advantages of WBM compost included significantly higher total C (333 vs. 210 kg Mg(-1) for SBM) and inorganic N (1.3 vs. 1.0 kg Mg(-1) for SBM) and significantly lower total phosphorus (4.5 vs. 5.3 kg Mg(-1) for SBM). Our results showed that wood chip bedding should not be a problem for subsequent composting of the manure after pen cleaning. In combination with other benefits, our findings should encourage the adoption of wood chips over straw as a bedding choice for southern Alberta feedlots. 相似文献
78.
79.
Judith Bell Jørgen Hilden Francis Bowling John Pearn Arthur Brownlea Nicole Martina 《黑龙江环境通报》1986,6(1):1-11
From the public health point of view, several formal attempts have been made to measure the impact of prenatal diagnosis (PND) on the incidence of Down's Syndrome (DS), but the results have varied widely. The impact of PND (reduction in the birth rate of chromosomally abnormal neonates) is related to utilization rates but quantitative estimates of this have not been established. In a three-year (1981–1983) total population study from Queensland, Australia, we present results to measure the impact of a voluntary PND programme on the birth incidence of DS, and also other chromosomally abnormal births. Utilization rates for the PND service were 15·5 per cent in that population of mothers 35 years and over. Numbers and rates of all cases of chromosomal abnormalities are presented, subclassified by type of diagnosis–-either by PND or by clinical diagnosis after birth. For the total population, 7·3 per cent of cases of DS were detected prenatally, and 15·4 per cent of all chromosome abnormalities. (A method for measuring the impact of PND is described.) Using this in conjunction with our demographic data, we estimate that with a 15 per cent utilization rate of PND by older mothers, 14 per cent of DS births can be prevented in this age group, or a 5 per cent overall reduction can be achieved if mothers of all ages are considered. One index–-the ratio of the percentage of DS births which are preventable compared with the population utilization rates of PND–-has potential for widespread use. Queensland data for this ratio is 0·34, a figure consistent with that from other studies. Thus a 3·5 per cent drop in the overall DS birth rate may be expected for each 10 per cent increase in the utilization rates of PND for mothers of 35 years and over. A diagram is presented which may serve as a model for improved data collection and better impact estimates in the future. 相似文献
80.
Egg-laying,egg-removal,and ovary development by workers in queenright honey bee colonies 总被引:13,自引:0,他引:13
Francis L.W. Ratnieks 《Behavioral ecology and sociobiology》1993,32(3):191-198
Summary The study investigates whether worker policing via the selective removal of worker-laid male eggs occurs in normal honey bee colonies with a queen. Queenright honey bee colonies were set up with the queen below a queen excluder. Frames of worker brood and drone comb were placed above the queen excluder. Daily inspections of the drone frames revealed the presence of a few eggs, presumably laid by workers, at a rate of 1 egg per 16000 drone cells. 85% of these eggs were removed within 1 day and only 2% hatched. Dissections of workers revealed that about 1 worker in 10000 had a fully developed egg in her body. These data show that worker egg-laying and worker policing are both normal, though rare, in queenright honey bee colonies, and provide further confirmation of the worker policing hypothesis. 相似文献