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891.
Towns concentrate around 50% of world-wide population and the trend is oriented to underscore an urban profile of population. In addition, towns have become important for their economic contribution to the Gross Internal Product. The negative side of towns is the environmental and social impacts as a result of productive and domestic activities, besides the lack of available data. In order to overcome these shortcomings, the United Nations has established a project of urban monitoring throughout the Global Network of Urban Observatories; Mexico joined the project in 2005. The Local Urban Observatory of Mexicali has the task to produce information about cities that is useful to design public policies. Some of this information deals with a set of environmental indicators in the United Nations Habitat Agenda, which includes solid wastes. Therefore, this paper deals with two main topics; firstly, from the Habitat Agenda, a comparative urban analysis of waste production and coverage of domestic waste collection services; secondly, from the Local Agenda, the identification and ranking of environmental problems according to public perception coming from people involved in the municipal planning and decision making process. Results will be used to develop local indicators and public environmental policies. 相似文献
892.
Aishah S. A. K. Sharifah Hanafiah Zainal Abidin Mohamad R. Sulaiman Kheng H. Khoo Hairi Ali 《Journal of Material Cycles and Waste Management》2008,10(2):116-123
Malaysia is in dire need of alternatives to landfilling for solid waste management. Recently, landfills have faced the problems
of overfilling, overflowing of leachates leading to pollution of water resources, and uncontrolled dust emissions adversely
affecting the local environment. With the rising cost of urbanization coupled with the high rate of waste generation, one
possible method of waste treatment that is receiving particular attention by the government is incineration. Incineration
of solid waste is rather new in Malaysia, with limited usage in handling small sources of waste generation such as the municipal
solid waste (MSW) of resort islands; however, its potential in ameliorating the problems associated with solid waste treatment
may make it an attractive alternative to landfill. This article presents the results of test runs conducted to investigate
the performance of a locally designed and manufactured rotary kiln incinerator (RKI). The test runs were conducted using MSW
collected from the Shah Alam municipality. The combustion efficiency was analyzed by looking at the temperature profiles and
chemical species concentrations. To complement the combustion characteristics measurements, predictions of the air flow in
the incinerator during the process were also investigated. The overall performance of the RKI suggests that it is suitable
for treating MSW. 相似文献
893.
D. S. Rosa C. G. F. Guedes C. M. Oliveira M. I. Felisberti 《Journal of Polymers and the Environment》2008,16(4):230-240
Mixtures of poly-β-(hydroxybutyrate-co-valerate) PHB-V with virgin and post-consumer low density polyethylene (LDPE) were
prepared by melt mixing in proportions of 100/0, 90/10, 80/20, 70/30 and 0/100 (wt/wt%). The mixtures were analysed by infrared
spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), melting flow index (MFI),
tensile tests, scanning electron microscopy (SEM) and biodegradation in simulated soil. The DMTA and DSC curves of post-consumer
LDPE suggested that this polymer was a mixture of LDPE and linear low density polyethylene (LLDPE). Virgin and post-consumer
LDPE had lower MFI than PHB-V, but the blends showed higher index as the content of LDPE increased. The addition of LDPE reduced
the tensile strength and Young’s modulus of the mixtures compared with PHB-V. SEM indicated poor interfacial adhesion between
PHB-V and LDPE. PHB-V degraded slow and gradually, while both LDPE showed virtually no degradation under the conditions studied.
The biodegradability of the blends depended on their composition and of the type of LDPE. LDPE improved the biodegradability
of the mixtures. 相似文献
894.
Jörg Luster Manoj Menon Sandra Hermle Rainer Schulin Madeleine S. Günthardt-Goerg Bernd Nowack 《Water, Air, & Soil Pollution: Focus》2008,8(2):163-176
Soil translocation for recultivation of soil removed from construction sites and for the preparation of refilled lysimeters
inevitably involves disturbance of soil structure, and, if intermediate storage is included, also drying and rewetting of
the soil. We report on an experiment with model forest ecosystems, where uncontaminated forest subsoils were covered with
non-contaminated or freshly heavy metal (mainly Zn and Cu) contaminated topsoil in large lysimeters. Monitoring of the chemical
composition of the drainage water revealed two distinct soil conditioning phases. During an initial phase of about a year
strongly elevated nitrate and sulfate concentrations occurred that were attributed to a mineralisation flush caused by the
increased accessability of mineralisable nitrogen and sulfur in destroyed aggregates. These effects were significantly larger
in lysimeters with calcareous subsoil than in those with acidic subsoil. The second phase was characterised by a gradual decrease
in dissolved organic carbon and sulfate concentrations, in particular in the acidic subsoil. This decrease may be attributed
to the depletion of pools made accessible during aggregate destruction or the formation of new aggregates. These chemical
changes had only little effects on the concentrations of copper and zinc in the drainage water. Based on our results, it can
be concluded that large refilled lysimeters can be used for many purposes without risk of compromised results, if a conditioning
phase of about 1 year with sufficiently moist soil conditions is respected. Nevertheless, gradual changes in soil chemical
characteristics still occur after this initial phase. Implications for the recultivation of sites using relocated soils are
discussed. 相似文献
895.
896.
H. S. Lin H. D. Scott K. F. Steele H. I. Inyang 《Environmental monitoring and assessment》1999,58(2):151-172
Statistical methods and a Geographic Information System (GIS) were used to investigate potential indicators of ground water vulnerability to agricultural chemical contamination in a representative area of the Mississippi River alluvial aquifer. A total of 47 wells were sampled for analysis of nitrate, phosphorus, potassium, and 13 pesticides commonly-used in the area. Ten soil and hydrogeologic variables and five ground water vulnerability indices were examined to explain the variations of chemical concentrations. The results showed that no individual soil or hydrogeologic variables or their linear combinations could explain more than 25% of the variation of the chemical concentrations. A quadratic response surface model with the values of confining unit thickness, slope, soil permeability, depth to ground water, and recharge rate accounted for 62% of the variation of nitrate, 43% of P, and 83% of K, suggesting that the interactions among soil and hydrogeologic variables were significant. Observed trends of decreasing nitrate and P concentrations with increasing well depth and/or depth to ground water seemed to correlate with carbonate equilibrium in the aquifer and more reduced environment with depth. In view of uncertainties involved, it was recognized that the limitations associated with input data resolution used in GIS and the formulation of leaching indices limited their use for predicting ground water vulnerability. Misuse of pesticides could be another factor that would complicate the relationships between pesticide concentrations and the vulnerability indices. 相似文献
897.
M. Böhm U. Hentschel A. Friedrich L. Fieseler R. Steffen V. Gamulin I. Müller W. Müller 《Marine Biology》2001,139(6):1037-1045
The aim of this study was the documentation of the molecular immune response of Suberites domuncula upon bacterial infection. Additionally, the bacteria that are naturally present in the sponge after prolonged aquarium maintenance were characterized. After 6 months of maintenance of S. domuncula in seawater aquaria, only one bacterial 16S rDNA sequence could be recovered, which belongs to the genus Pseudomonas. Concomitantly, morphologically uniform bacteria were found encapsulated in bacteriocytes. These findings indicate that certain bacteria, possibly of the genus Pseudomonas, are able to persist for long periods in host bacteriocytes. Subsequent to performing a previously established infection assay with S. domuncula, a potentially pathogenic Vibrio sp. was isolated from the tissues. Furthermore, the host tissue disintegrated and asexual propagation bodies (gemmules) were formed. In order to gain insights into the molecular events occurring after bacterial infection, the stress-response kinases, p38 protein kinase and JNK protein kinase, were analyzed. It is demonstrated that these two kinases are activated (phosphorylated) upon incubation of the tissue with the bacterial endotoxin lipopolysaccharide (LPS). Moreover, LPS strongly inhibits protein synthesis. It is concluded that there are many functionally different interactions between S. domuncula and bacteria and that the animal possesses mechanisms to differentiate between bacteria and to respond accordingly. 相似文献
898.
Uptake of Chromium by Trees: Prospects for Phytoremediation 总被引:3,自引:0,他引:3
899.
A stow net (90 m2 opening) was used, at regular intervals between July 1989 and June 1993, to collect fish over ca. 4 h on both the flood and
ebb tides at five sites distributed at regularly spaced distances throughout the Elbe Estuary. Overall, 53.4% of the species
were marine, and some of these were abundant, e.g.Clupea harengus, Pleuronectes flesus, Pomatoschistus minutus, Merlangius merlangus and Sprattus sprattus. However, in terms of number of individuals, such species contributed only 9.1%, compared with 90.0% by anadromous species,
which was predominantly due to exceptionally high catches of Osmerus eperlanus. The ichthyofaunal compositions on the flood and ebb tides were similar, even downstream where salinities change markedly
during each tidal cycle. Although this is probably due in part to groups of fish being swept first upstream on the flood tide
and then back downstream on the ebb tide, several species clearly tended to occupy particular regions of the estuary. Each
year the species composition changed sequentially from the most downstream site (max. salinity=ca. 31.4‰) to the most upstream
site (max. salinity=ca. 1.5‰), mainly as a result of a sequential decline in the number and abundance of marine species and
a progressive increase in the contributions of both anadromous and freshwater species. However, the marine species diagnostic
of differences in the compositions among regions varied between years. Thus, for example, the diagnostic species for the downstream
sites were C. harengus and M. merlangus in 1990/1991 and S. sprattus in 1992/1993, reflecting differences in the recruitment strengths of these marine species in the two years. The ichthyofaunal
composition exhibited pronounced annual cyclical changes in each region and thus occurred irrespective of whether or not the
salinity in a region underwent pronounced changes during the year. This cyclicity was attributable to intra-annual variations
in the times of recruitment of certain marine species, particularly in the downstream region, and to seasonal migrations of
diadromous species into each region, as well as to the movements of freshwater species into the upstream region in winter
and early spring.
Received: 18 November 1999 / Accepted: 25 October 2000 相似文献
900.
Home range, activity and distribution patterns of a temperate rocky-reef fish, Cheilodactylus fuscus
Red morwong (Cheilodactylus fuscus; Cheilodactylidae: Perciformes), are large temperate rocky reef fish that are patchily distributed in local aggregations
of 3 to >100 fish. The home ranges and aggregating behaviour of red morwong were investigated using external tags (n = 114, over 35 mo) and ultrasonic transmitters (n = 9 over 20 d) at coastal and estuarine sites in south-east Australia. Adult red morwong had a mean home range during the
day of 1865 m2 (SE = 268). Night movement, determined by ultrasonic telemetry, indicated a significantly greater mean home range of 3639 m2 (SE = 416). Home range did not differ significantly with size or sex. Fish movements were greatest and aggregation sizes
varied most during the non-reproductive mid-summer period. Tagged fish (N = 20) displaced 200 to 900 m returned in 1 to 3 d to the point of capture, often traversing open sand habitat and other aggregations.
During the day, fish were commonly found on bouldered habitat. During the night, these site-specific aggregations fragmented
as fish dispersed over a variety of substrata, with crepuscular peaks in activity. Therefore, estimates of habitat-specificity
and feeding patterns collected only by day may give misleading results.
Received: 28 June 1996 / Accepted: 8 July 1998 相似文献