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141.
Variations of metal distribution in sewage sludge composting 总被引:4,自引:0,他引:4
In the study, the variations of heavy metal distributions (of Cu, Mn, Pb, and Zn) during the sewage sludge composting process were investigated by sequential extraction procedures. The total content of Cu and Zn in the composted mixture increased after the composting process. Mn and Zn were mainly found in mobile fractions (exchangeable fraction (F1), carbonate fraction (F2), and Fe/Mn oxide fraction (F3)). Cu and Pb were strongly associated with the stable fractions (organic matter/sulfides fraction (F4) and residual fraction (F5)). These five metal fractions were used to calculate the metal mobility (bioavailability) in the sewage sludge and composted mixture. The mobility (bioavailability) of Mn, Pb, and Zn (but not Cu) increased during the composting process. The metal mobility in the composted mixture ranked in the following order: Mn>Zn>Pb>Cu. 相似文献
142.
Solid waste management (SWM) is a multidimensional challenge faced by urban authorities, especially in developing countries like Bangladesh. We investigated per capita waste generation by residents, its composition, and the households' attitudes towards waste management at Rahman Nagar Residential Area, Chittagong, Bangladesh. The study involved a structured questionnaire and encompassed 75 households from five different socioeconomic groups (SEGs): low (LSEG), lower middle (LMSEG), middle (MSEG), upper middle (UMSEG) and high (HSEG). Wastes, collected from all of the groups of households, were segregated and weighed. Waste generation was 1.3kg/household/day and 0.25kg/person/day. Household solid waste (HSW) was comprised of nine categories of wastes with vegetable/food waste being the largest component (62%). Vegetable/food waste generation increased from the HSEG (47%) to the LSEG (88%). By weight, 66% of the waste was compostable in nature. The generation of HSW was positively correlated with family size (r(xy)=0.236, p<0.05), education level (r(xy)=0.244, p<0.05) and monthly income (r(xy)=0.671, p<0.01) of the households. Municipal authorities are usually the responsible agencies for solid waste collection and disposal, but the magnitude of the problem is well beyond the ability of any municipal government to tackle. Hence dwellers were found to take the service from the local waste management initiative. Of the respondents, an impressive 44% were willing to pay US$0.3 to US$0.4 per month to waste collectors and it is recommended that service charge be based on the volume of waste generated by households. Almost a quarter (22.7%) of the respondents preferred 12-1pm as the time period for their waste to be collected. This study adequately shows that household solid waste can be converted from burden to resource through segregation at the source, since people are aware of their role in this direction provided a mechanism to assist them in this pursuit exists and the burden is distributed according to the amount of waste generated. 相似文献
143.
144.
The influence of clay minerals on the reduction of Cr6+ by citric acid was investigated at pH values 4.0, 4.5 and 5.0 at 25 degrees C. The results indicate that montmorillonite and illite greatly accelerate the reduction reactions at pH 4.0 and 4.5, but their effects are dramatically reduced at pH 5.0. The role of clay minerals in accelerating the reactions is in the order: illite>montmorillonite>kaolinite, which has a positive correlation with the amount of Mn2+ adsorbed on the surfaces of these minerals. With light, Fe(3+) also significantly increases reaction rates. Ethylenediaminetetraacetic acid (EDTA) greatly suppresses the acceleration of the reduction reactions by these minerals, indicating that EDTA competes with citric acid for Mn2+. Thus, the formation of complexes between Mn(2+) and citric acid could be a prerequisite for the acceleration of the reductions of Cr6+ by clay minerals. In addition, there is no relationship between the specific surface area of clay minerals and the reduction rate of Cr6+ by citric acid. 相似文献
145.
Characterizing effects of uncertainties in MSW composting process through a coupled fuzzy vertex and factorial-analysis approach 总被引:1,自引:0,他引:1
A coupled fuzzy vertex and factorial-analysis approach was developed in this study for systematically characterizing effects of uncertainties in a municipal solid waste composting process. A comprehensive composting process model was also embedded into the system framework and used to address substrate decomposition and biomass growth, as well as the interactions between moisture contents, temperatures, and oxygen concentrations. The applicability of the proposed method was verified through a custom-made pilot-scale composting system. Results from fuzzy simulation indicated that the fuzzy vertex method could effectively communicate implicit knowledge into dynamic simulations and thus provide valuable information for enhancing composting process control under uncertainty. The factorial analysis was effective in quantifying the proportion to which the uncertainty of each single or interactive effect of model parameters contributes to the overall uncertainty of the system outcomes. Thus, sensitive parameters that may lead to errors or unreasonable predictions can be determined. The proposed study system could not only be used in characterizing combined effects of uncertainties for composting processes, but was also applicable to many other environmental modelling systems. 相似文献
146.
Information on food waste disposal and on recycling methods and recycled amounts is reported. Data were obtained from a mail and phone survey of all licensed food establishments in Hawaii conducted in 2004 and 2005. Of 8253 licensed food establishments, 5033 completed surveys. It was found that relationships exist between food establishment size (measured by the number of meals served per day or the number of employees) and the amount of food an establishment recycled; establishment type and recycling behavior; and establishment type and amount recycled. The amount of food waste recycled in the state of Hawaii was estimated to be 264,000 L/day and annual food waste generation was estimated to be 336,000 tonnes. 相似文献
147.
Some concepts of sustainability applied to soils are given in relation to the Organisation for Economic Co-operation and Development (OECD) Co-operative Research Programme 'Biological Resource Management for Sustainable Agricultural Systems'. The application of these concepts to climate change will be discussed in relation to seven high-profile papers published over the past 12 months. It is argued that multi-disciplinary (including social science) approaches are needed to address the issues. There is also a brief discussion on biomass energy in terms of soil sustainability and climate change. 相似文献
148.
Houghton DC 《Environmental monitoring and assessment》2007,135(1-3):253-264
Over 300,000 caddisfly specimens representing 249 species were collected from nearly 250 sites throughout Minnesota during
2000 and 2001 to determine the effects of human disturbance on the composition of caddisfly trophic functional groups at the
landscape level. Canonical correspondence analysis determined that stream width was the most important variable influencing
functional group composition in regions of the state with relatively low disturbance, and that differences in the caddisfly
fauna between sizes of streams generally followed trends predicted by the river continuum concept. In regions of the state
with moderate disturbance, both stream width and the percentage of disturbed habitat upstream of a site were important variables
influencing functional group composition. In highly disturbed regions, no variables corresponded to changes in the composition
of caddisfly functional groups. Instead, ecosystems were homogeneous: fine-particle filtering collectors dominated in all
sizes of streams. The observed aquatic ecosystem homogenization is attributed mostly to input of fine-particle organic and
inorganic sediment from extensive agriculture. 相似文献
149.
Weather-mediated natural selection on arrival time in cliff swallows (Petrochelidon pyrrhonota) 总被引:2,自引:0,他引:2
An unusually long period of cold weather in May 1996 caused extensive mortality among insectivorous cliff swallows (Petrochelidon pyrrhonota) in the northern and central Great Plains. We analyzed how viability selection affected spring arrival time in a migratory
Nebraska population by comparing capture histories of survivors with those of birds known to have died and by documenting
how arrival time changed in the year following the selection event. Surviving birds had significantly later first-capture
dates (an index of arrival time) in the years prior to selection than those that died; a significant selection differential
suggested directional selection for birds that arrived later. Colony sites were occupied significantly later following the
selection event, and the distribution of first-capture dates in the season after selection was significantly shifted toward
later arrivals. Offspring of the survivors tended to arrive later than birds of the same age prior to the selection event.
While major weather-caused mortality events of this magnitude are rare in the study area, spells of cold weather severe enough
to cause limited mortality are frequent in April and early May. At least 25 probable mortality events of varying severity
were identified in the last 50 years based on climatological data. Periodic weather-mediated selection against early arrival
constrains the cliff swallow’s breeding season and may partly prevent directional selection for earlier nesting.
Received: 19 October 1999 / Received in revised form: 15 January 2000 / Accepted: 24 January 2000 相似文献
150.
Social and mating system of cooperatively breeding laughing kookaburras (Dacelo novaeguineae) 总被引:4,自引:0,他引:4
DNA fingerprinting was combined with field observations over four breeding seasons to investigate the social structure and
mating system of the laughing kookaburra (Dacelo novaeguineae). Groups comprised a socially dominant pair and up to six helpers of either sex. Helpers were always recruited from young
hatched in the group. Territorial inheritance, which is a feature of other cooperative breeders and an oft-cited benefit of
philopatry, did not occur. Helpers only attained dominant status in an established group by dispersing into a vacant dominant
position in that group. However, helpers could also form new groups by excising a new territory, often through a ”budding”
process. The mating system was overwhelmingly monogamous. There were no cases of extra-group parentage in a sample of 140
nestlings; within groups of three or more birds, dominance predicted parentage almost perfectly (99.2% of 129 nestlings),
irrespective of whether helpers in the group were related to one or both dominant birds. This is contrary to predictions from
models of reproductive skew, possibly because they currently fail to incorporate the willingness of females to share reproduction
among males.
Received: 15 May 1999 / Received in revised form: 2 November 1999 / Accepted: 6 November 1999 相似文献