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41.
Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscatus var. radula of Iko River were conducted between 2003 and 2004. The impact of anthropogenic activities especially industrial effluent,
petroleum related wastes, gas flare and episodic oil spills on the ecosystem are remarkable. Trace metals analyzed included
cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), vanadium (V) and zinc (Zn). Sediment
particle size analysis revealed that they were characteristically psammitic and were predominantly of medium to fine grained
sand (>73%), less of silt (<15%) and clay (<10%). These results correlated with low levels of trace elements such as Pb (0.03 ± 0.02 mg kg−1), Cr (0.22 ± 0.12 mg kg−1), Cd (0.05 ± 0.03 mg kg−1), Cu (0.04 ± 0.02 mg kg−1) and Mn (0.23 ± 0.22 mg kg−1) in the sediment samples. This observation is consistent with the scarcity of clayey materials known to be good scavengers
for metallic and organic contaminants. Sediments indicated enhanced concentration of Fe, Ni and V, while other metal levels
were relatively low. The concentrations of all the metals except Pb in surface water were within the permissible levels, suggesting
that the petroleum contaminants had minimal effect on the state of pollution by trace metals in Iko River. Notably, the pollutant
concentrations in the sediments were markedly higher than the corresponding concentrations in surface water and T. fuscatus tissues, and decreased with distance from point sources of pollution. 相似文献
42.
Wastewater management in small and medium-sized enterprises representing the chemical and food industries was investigated.
The results showed that wastewater discharged from an ink-production factory was highly contaminated with organic pollutants.
Anaerobic biological treatment followed by chemical coagulation using ferric chloride aided with lime proved to be very effective
and produced an effluent that complied with national regulatory standard for wastewater discharge into public sewage network.
Also, management of wastewater from a confectionery factory representing the food sector was carried out. Aerobic biological
treatment using plastic-packed trickling filter proved to be an effective treatment method. However, application of in-plant
control measures alleviated the requirement for the construction of a wastewater treatment plant. The applied pollution prevention
and cleaner production measures involved good housekeeping, recovery of spent chocolate, modification of floor cleaning and
installation of suction devices for the removal of sugar and starch powders. All improvement measures were documented by cost/benefit
analysis. 相似文献
43.
Recycling and conservation efforts for water are the need of the day because of the lack of new water sources and the ever-increasing
demand for drinking water. Seedlings of Acacia nilotica L. were irrigated with: canal water (T1, control); municipal effluent (T2); textile effluent (T3); steel effluent (T4); textile + municipal effluent in 1:1 ratio (T5); steel + municipal effluent in 1:2 ratio (T6); steel + textile in 1:2 ratio (T8) and steel + municipal + textile in 1:2:2 ratio (T7) with views to observe effluents effect on the seedlings and its adaptability and to recommend safe disposal of these effluents.
Seedlings in T6, T7 and T8 showed 50% lesser height and collar diameter than those in control. Seedlings in T2 attained greatest height, collar diameter, numbers of branches and produced 140 g dry biomass seedling−1. Highest concentration of manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn) and lowest concentration of nitrogen (N),
phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) in the seedlings of T4, T6, T7 and T8 resulted in nutritional imbalance, mineral toxicity and reduction in photosynthetic (Pn) and transpiration (E) rates and caused seedling mortality. Seedlings of T3 had highest sodium concentration and low concentration of Ca, Mg and micronutrients resulting in nutritional imbalance, augmented
chlorosis and reduced gas exchange and biomass by half as compared to control. Increased growth, Pn and E and biomass in seedlings of T5 over T3 and survival period in T6, T7 and T8 seedlings suggested a beneficial effect of effluents mixing. Unscientific disposal should be avoided and toxic concentration
of metal ions␣may be reduced for long-term application and harmless disposal of effluents in afforestation and urban development. 相似文献
44.
Henrietta Nittby Bengt Widegren Morten Krogh Gustav Grafström Henrik Berlin Gustav Rehn Jacob L. Eberhardt Lars Malmgren Bertil R. R. Persson Leif G. Salford 《The Environmentalist》2008,28(4):458-465
We have earlier shown that radio frequency electromagnetic fields can cause significant leakage of albumin through the blood–brain
barrier of exposed rats as compared to non-exposed rats, and also significant neuronal damage in rat brains several weeks
after a 2 h exposure to a mobile phone, at 915 MHz with a global system for mobile communications (GSM) frequency modulation,
at whole-body specific absorption rate values (SAR) of 200, 20, 2, and 0.2 mW/kg. We have now studied whether 6 h of exposure
to the radiation from a GSM mobile test phone at 1,800 MHz (at a whole-body SAR-value of 13 mW/kg, corresponding to a brain
SAR-value of 30 mW/kg) has an effect upon the gene expression pattern in rat brain cortex and hippocampus—areas where we have
observed albumin leakage from capillaries into neurons and neuronal damage. Microarray analysis of 31,099 rat genes, including
splicing variants, was performed in cortex and hippocampus of 8 Fischer 344 rats, 4 animals exposed to global system for mobile
communications electromagnetic fields for 6 h in an anechoic chamber, one rat at a time, and 4 controls kept as long in the
same anechoic chamber without exposure, also in this case one rat at a time. Gene ontology analysis (using the gene ontology
categories biological processes, molecular functions, and cell components) of the differentially expressed genes of the exposed
animals versus the control group revealed the following highly significant altered gene categories in both cortex and hippocampus:
extracellular region, signal transducer activity, intrinsic to membrane, and integral to membrane. The fact that most of these
categories are connected with membrane functions may have a relation to our earlier observation of albumin transport through
brain capillaries. 相似文献
45.
Olanike O. Aladenola Ayodele E. Ajayi Ayorinde A. Olufayo Babatunde Ajayi 《The Environmentalist》2008,28(2):123-127
The performance of a mixture of a forest bye product and cement for the production of storage structure for harvested rainwater
was assessed. Three mix ratios of Cement: Gmelina arborea sawdust 3.0:1.0 (specimen A), 2.5:1.0 (specimen B) and 2.0:1.0 (specimen C) were considered. Engineering properties and dimensional
stability of the different mix-ratios were monitored from prototypes cylindrical pots and test billet specimens. Possible
change in quality of stored rainwater, with time was monitored in all the three cases. Water quality parameters monitored
include pH, hardness, total suspended solids, alkalinity, acidity and total dissolved CO2. The tensile stress obtained were 110, 104, and 95 N/mm2, while the compressive strength were 5,000, 3,000, and 2,000 kN for specimens A, B and C respectively. Accelerated aging
test showed that sample A were more resistant to deformation, while specimen C were more susceptible to change in structure
over time. Similarly, the values of tensile and compressive strength after accelerated aging test increased in the order of
specimen A > B > C. Except in specimen C where significant differences in alkalinity and acidity were observed, there were
no significant differences in quality of the water stored in the pots after 2 months of storage. The results indicate the
suitability of the Gmelina arborea waste as an alternative in constructing water storage structures in rural communities. 相似文献
46.
47.
Crowding and Experience-Use History: A Study of the Moderating Effect of Place Attachment Among Water-Based Recreationists 总被引:1,自引:1,他引:0
Effective recreation resource management relies on understanding visitor perceptions and behaviors. Given current and increasing
pressures on water resources, understanding crowding evaluations seems important. Beyond crowding, however, variables that
possibly relate to or influence crowding are of interest and in particular, place attachment and experience-use history (EUH).
As EUH is related to place attachment and likely affects crowding, this study explored the moderating effect of place attachment
dimensions on the relationships between EUH and visitor crowding evaluations. Water based recreationists at a U.S. Army Corps
of Engineers site were contacted onsite and asked questions related to experience-use history, crowding evaluations, place
attachment, and activity participation. Anglers and campers at the site identified similar crowding perceptions and place
attachments. Only one of eight models tested revealed a moderating effect. Specifically, place identity moderated the relationship
between the total times visited in the past twelve months and expected crowding among anglers. As such, the quest continues
to understand the relationship among these important variables. 相似文献
48.
This article describes the history of the Coachella Valley Multiple Species Habitat Conservation Plan (CVMSHCP), in the Riverside
County region of Southern California. When this collaborative biodiversity conservation planning process began, in 1994, local
participants and supporters had numerous factors working in their favor. Yet, as of April 2007, nearly 13 years had passed
without an approved plan. This is a common problem. Many multiple species habitat conservation plans now take more than a
decade to complete, and the long duration of these processes often results in negative consequences. The CVMSHCP process became
bogged down—despite strong scientific input and many political advantages—due to problematic relationships between the Plan’s
local supporters, its municipal signatory parties, and officials from the state and federal wildlife agencies, particularly
the regional office of the US Fish and Wildlife Service. This case study demonstrates the crucial importance of institutional
structures and relationships, process management, and timeliness in habitat conservation planning. We conclude by offering
several related recommendations for future HCP processes. 相似文献
49.
We compared measures of ecosystem state across six adjacent land-tenure groups in the intact tropical savanna landscapes of
northern Australia. Tenure groups include two managed by Aboriginal owners, two national parks, a cluster of pastoral leases,
and a military training area. This information is of relevance to the debate about the role of indigenous lands in the Australian
conservation estate. The timing and frequency of fire was determined by satellite imagery; the biomass and composition of
the herb-layer and the abundance of large feral herbivores by field surveys; and weediness by analysis of a Herbarium database.
European tenures varied greatly in fire frequencies but were consistently burnt earlier in the dry season than the two Aboriginal
tenures, the latter having intermediate fire frequencies. Weeds were more frequent in the European tenures, whilst feral animals
were most abundant in the Aboriginal tenures. This variation strongly implies a signature of current management and/or recent
environmental history. We identify indices suitable for monitoring of management outcomes in an extensive and sparsely populated
landscape. Aboriginal land offers a unique opportunity for the conservation of biodiversity through the maintenance of traditional
fire regimes. However, without financial support, traditional practices may prove unsustainable both economically and because
exotic weeds and feral animals will alter fire regimes. An additional return on investment in Aboriginal land management is
likely to be improved livelihoods and health outcomes for these disadvantaged communities. 相似文献
50.
During the past decades, the traditional state monopoly in urban water management has been debated heavily, resulting in different
forms and degrees of private sector involvement across the globe. Since the 1990s, China has also started experiments with
new modes of urban water service management and governance in which the private sector is involved. It is premature to conclude
whether the various forms of private sector involvement will successfully overcome the major problems (capital shortage, inefficient
operation, and service quality) in China’s water sector. But at the same time, private sector involvement in water provisioning
and waste water treatments seems to have become mainstream in transitional China. 相似文献