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711.
Laursen K White TJ Cresswell DJ Wainwright PJ Barton JR 《Journal of environmental management》2006,80(3):208-213
The geographical limitations of Singapore, its restricted natural resources and voluminous municipal and industrial waste streams, make environmental management a major challenge for the island state. In an attempt to find ways to reduce importation of raw materials and the waste sent to landfill, light weight aggregates were produced from marine clay and a CaF(2)-rich semiconductor industry sludge. Aggregates were produced in a bench-scale rotary kiln with three clay/sludge loadings (90/10, 70/30 and 50/50%). All three mixtures showed good bloating behavior during firing and the ceramic pellets (1-1.5cm diameter) had densities well below that required for light-weight aggregates. In the initial tests, the pore sizes of the aggregates were in general too large resulting in high water absorption. Comparisons between the composition of the two waste products and the aggregates showed a significant loss of fluorine (40-60%) during processing; a problem which may require flue gas treatment. Leach testing showed that the formed aggregates would not pose a human or environmental hazard in terms of fluorine mobilization. 相似文献
712.
García-Nieto PJ 《Journal of environmental management》2006,79(4):372-382
This paper studies the scavenging efficiencies of aerosol emissions from coal-fired power plants under different removal mechanisms (coagulation, heterogeneous nucleation and gravitational settling) as a function of time. It also analyses the ‘health impact’ of the aerosol before and after the above dynamic mechanisms by comparing the respirable dust fractions. The well-known equations of evolution are applied to an average PSD that represents the exhaust particulate emissions from coal-fired power plants (i.e. Aboño power plant in Asturias that belongs to Hidrocantábrico Group, S.A.). From this study it is inferred that respirable dust is scavenged with the greatest difficulty and when compared with the initial volume of respirable dust, roughly 20% remains after 18 h of gravitational settling. Therefore, gravitational settling is the main removal mechanism of respirable dust compared to condensation and coagulation. 相似文献
713.
BR-319: Brazil’s Manaus-Porto Velho Highway and the Potential Impact of Linking the Arc of Deforestation to Central Amazonia 总被引:3,自引:0,他引:3
Brazil’s BR-319 Highway linked Manaus, in the state of Amazonas, to Porto Velho, Rondônia, until it became impassable in 1988. Now it is proposed for reconstruction and paving, which would facilitate migration from the “Arc of Deforestation” in the southern part of the Amazon region to new frontiers farther north. The purpose of the highway, which is to facilitate transport to São Paulo of products from factories in the Manaus Free Trade Zone, would be better served by sending the containers by ship to the port of Santos. The lack of a land connection to Manaus currently represents a significant barrier to migration to central and northern Amazonia. Discourse regarding the highway systematically overestimates the highway’s benefits and underestimates its impacts. A variety of changes would be needed prior to paving the highway if these potential impacts are to be attenuated. These include zoning, reserve creation, and increased governance in various forms, including deforestation licensing and control programs. More fundamental changes are also needed, especially the abandonment of the long-standing tradition in Brazil of granting squatters’ rights to those who invade public land. Organizing Amazonian occupation in such a way that road construction and improvement cease to lead to explosive and uncontrolled deforestation should be a prerequisite for approval of the BR-319 and other road projects for which major impacts are expected. These projects could provide the impetus that is needed to achieve the transition away from appropriation of public land by both small squatters and by grileiros (large-scale illegal claimants). A delay in reconstructing the highway is advisable until appropriate changes can be effected. 相似文献
714.
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
715.
Soil pollution with Cd is an environmental problem common in the world, and it is necessary to establish what Cd concentrations
in soil could be dangerous to its fertility from toxicity effects and the risk of transference of this element to plants and
other organisms of the food chain. In this study, we assessed Cd toxicity on soil microorganisms and plants in two semiarid
soils (uncultivated and cultivated). Soil ATP content, dehydrogenase activity, and plant growth were measured in the two soils
spiked with concentrations ranging from 3 to 8000 mg Cd/kg soil and incubated for 3 h, 20 days, and 60 days. The Cd concentrations
that produced 5%; 10%;, and 50%; inhibition of each of the two soil microbiological parameter studied (ecological dose, ED,
values) were calculated using two different mathematical models. Also, the effect of Cd concentration on plant growth of ryegrass
(Lolium perenne, L.) was studied in the two soils. The Cd ED values calculated for soil dehydrogenase activity and ATP content were higher
in the agricultural soils than in the bare soil. For ATP inhibition, higher ED values were calculated than for dehydrogenase
activity inhibition. The average yields of ryegrass were reduced from 5.03 to 3.56 g in abandoned soil and from 4.21 to 1.15
g in agricultural soil with increasing concentrations of Cd in the soil. Plant growth was totally inhibited in abandoned and
agricultural soils at Cd concentrations above 2000 and 5000 mg/kg soil, respectively. There was a positive correlation between
the concentration of Cd in the plants and the total or DTPA-extractable concentrations of Cd in the soil. 相似文献
716.
Employing in-depth, elite interviews, this empirical research contributes to understanding the dynamics among policy windows,
policy change, and organizational learning. First, although much of the research on agenda setting—how issues attract enough
attention that action is taken to address them—has been conducted at the national scale, this work explores the subnational,
regional scale. With decentralization, regional-scale environmental decision-making has become increasingly important. Second,
this research highlights the role of policy windows and instances of related organizational learning identified by natural
resources managers. Having practitioners identify focusing events contrasts with the more typical approach of the researcher
identifying a particular focusing event or events to investigate. A focusing event is a sudden, exceptional experience that,
because of how it leads to harm or exposes the prospect for great devastation, is perceived as the impetus for policy change. 相似文献
717.
The extensive literature on environmental justice has, by now, well defined the essential ingredients of cumulative risk,
namely, incompatible land uses and vulnerability. Most problematic is the case when risk is produced by a large aggregation
of small sources of air toxics. In this article, we test these notions in an area of Southern California, Southeast Los Angeles
(SELA), which has come to be known as Asthmatown. Developing a rapid risk mapping protocol, we scan the neighborhood for small
potential sources of air toxics and find, literally, hundreds of small point sources within a 2-mile radius, interspersed
with residences. We also map the estimated cancer risks and noncancer hazard indices across the landscape. We find that, indeed,
such large aggregations of even small, nondominant sources of air toxics can produce markedly elevated levels of risk. In
this study, the risk profiles show additional cancer risks of up to 800 in a million and noncancer hazard indices of up to
200 in SELA due to the agglomeration of small point sources. This is significant (for example, estimates of the average regional
point-source-related cancer risk range from 125 to 200 in a million). Most importantly, if we were to talk about the risk
contour as if they were geological structures, we would observe not only a handful of distinct peaks, but a general “mountain
range” running all throughout the study area, which underscores the ubiquity of risk in SELA. Just as cumulative risk has
deeply embedded itself into the fabric of the place, so, too, must intervention seek to embed strategies into the institutions
and practices of SELA. This has implications for advocacy, as seen in a recently initiated participatory action research project
aimed at building health research capacities into the community in keeping with an ethic of care. 相似文献
718.
Romário J. da Silv Lizeth Carolina Mojica-Sánchez Filipe D.S. Gorz Graciela C. Pedro Bruna G. Maciel Gabriela P. Ratkovski Hérica D. da Roch Kamila T.O. do Nascimento Juan C. Medina-Llamas Alicia E. Chávez-Guajardo José J. Alcaraz-Espinoz Celso P. de Melo 《环境科学学报(英文版)》2021,33(2):62-73
We report the preparation of poly(3,4-ethylene dioxythiophene) (PEDOT)-modified polyvinylidene fluoride electrospun fibers and their use as a novel adsorbent material for the removal of the anionic dye Methyl Orange (MO) from aqueous media. This novel adsorbent material can be used to selectively remove MO on a wide pH range (3.0–10.0), with a maximum capacity of 143.8 mg/g at pH 3.0. When used in a recirculating filtration system, the maximum absorption capacity was reached in a shorter time (20 min) than that observed for batch mode experiments (360 min). Based on the analyses of the kinetics and adsorption isotherm data, one can conclude that the predominant mechanism of interaction between the membrane and the dissolved dye molecules is electrostatic. Besides, considering the estimated values for the Gibbs energy, and entropy and enthalpy changes, it was established that the adsorption process is spontaneous and occurs in an endothermic manner. The good mechanical and environmental stability of these membranes allowed their use in at least 20 consecutive adsorption/desorption cycles, without significant loss of their characteristics. We suggest that the physical-chemical characteristics of PEDOT make these hybrid mats a promising adsorbent material for use in water remediation protocols and effluent treatment systems. 相似文献
719.
Russian Journal of Ecology - A study of the anthropogenic impacts on the on-shore aggregation of true seals was carried out at a haul-out located at the mouth of Piltun Bay (the northeastern part... 相似文献
720.
Zadubrovskiy P. A. Vasina A. V. Novikova E. V. Kondratyuk E. Yu. Matskalo L. L. Novikov E. A. 《Russian Journal of Ecology》2021,52(4):283-289
Russian Journal of Ecology - To test the hypothesis that animals from habitats exposed to high anthropogenic pressure are more successful in adapting to captivity, immature narrow-skulled voles... 相似文献