Genetic variation among age-classes of the mangrove Avicennia marina in clean and contaminated sediments     

Melville F  Burchett M  Pulkownik A 《Marine pollution bulletin》2004,49(9-10):695-703

An examination was made of the genetic variation with age in mangrove populations in two estuaries in south-east Australia, one contaminated, the other uncontaminated. Sediment nutrient and metal levels, and isozyme/allozyme complements were measured in three age-classes in four stands in each estuary, to identify site and intergenerational genetic composition, and influences of sediment contamination. Within each river, there were greater genetic distances among the age-classes than among sampling sites. A downstream gradient of genetic distance was found in the uncontaminated river, but not the contaminated one, where genetic distances seemed to reflect site-specific factors, though apparently not the present sediment metal or nutrient levels. It appears that genetic distances in the polluted river may reflect past fluctuations in pollution pressures. In both rivers, genetic distances indicate that the mangroves within one estuary form one population, with 'neighbourhood' differentiation.  相似文献   

Whole-bird models for the magnetic cleansing of oiled feathers     

Orbell JD  Ngeh LN  Bigger SW  Zabinskas M  Zheng M  Healy M  Jessop R  Dann P 《Marine pollution bulletin》2004,48(3-4):336-340

Iron powder, a promising dry-cleansing agent for oiled feathers where both the contaminant and the cleansing agent may be harvested magnetically, has been tested on the plumage of whole-bird models. The breast and back plumage of Mallard Duck (Anas platyrhynchos) and Little Penguin (Eudyptula minor) carcasses were patch-contaminated with commercial-grade engine oil, three different crude oils, and an oil/seawater emulsion. The plumage was then subjected to a magnetic cleansing protocol. The contaminant removal was assessed gravimetrically and was found to reflect the outcomes for a previously reported in vitro study using feather clusters. Between 92-98% of the contaminants, and effectively all of the cleansing agent, were removed from the feathers.  相似文献   

Assessment of the impact of industrial effluents on water quality of receiving rivers in urban areas of Malawi   总被引：2，自引：0，他引：2  

O. Phiri  P. Mumba  B. H. Z. Moyo  W. Kadewa 《International Journal of Environmental Science and Technology》2005,2(3):237-244

A study was carried out in Malawi to assess the extent of chemical pollution in a receiving river as affected by industrial effluents. Both the effluents and the water at selected points in the river were analysed for pH, dissolved oxygen, biochemical oxygen demand, electrical conductivity, suspended solids, nitrate, alkalinity, hardness, chloride and phosphate in the dry and rainy seasons. The results showed that the effluents were acidic in both the dry season (range: 4.2 ± 0.02–6.5 ± 0.02) and in the rainy season (range: 4.2 ± 0.05–5.6 ± 0.01). While the levels of dissolved oxygen, biological oxygen demand, electrical conductivity, suspended solids, alkalinity and chloride were relatively high in the dry and rainy seasons, the concentration of phosphate and nitrate were low in both seasons. The water upstream was neutral (average pH, 7.40 ± 0.04) with high dissolved oxygen but low in the levels of the other parameters in both seasons. The water after the effluent receiving points was acidic and the levels of the other parameters were high, especially downstream. The results suggested that the water in the river was polluted and not good for human consumption. It is therefore recommended that the careless disposal of the wastes should be discouraged and although the values in some cases were lower than the allowable limits, the continued discharge of the effluents in the river may result in severe accumulation of the contaminants and, unless the authorities implement the laws governing the disposal of wastes, this may affect the lives of the people.  相似文献   

Methodological challenges posed in studying an elite in the field     

Margaret Desmond 《Area》2004,36(3):262-269

This paper engages with recent debates in geography and associated disciplines that are concerned with the wider analytic issues to be confronted in researching an elite. Drawing on a case study of the construction of a policy position on GMOs and the Environment in Ireland, the methodological challenges encountered researching up the hybrid elite central to this development are interrogated. In particular, emphasis is placed on the politics of time, which becomes central when a new sector is emerging, and meanings and definitions are being constructed.  相似文献   

Evidence of Strain Partitioning Between the Sierra Madre Fault and the Los Angeles Basin, Southern California from Numerical Models     

Margaret T. Glasscoe  Andrea Donnellan  Louise H. Kellogg  Gregory A. Lyzenga 《Pure and Applied Geophysics》2004,161(11-12):2343-2357

— Geodetic data indicate that the northern Metropolitan Los Angeles region is shortening at a rate of 4.5–6.0 mm/yr between downtown Los Angeles and the San Gabriel Mountains. If we assume that all of the uplift of the San Gabriel Mountains is due to the major frontal fault system (the Sierra Madre fault) and use reported values for bedrock uplift, slip per event and recurrence intervals to determine the slip rate on the Sierra Madre fault, we obtain slip rates between 0.6–1.27 mm/yr. Using these slip rates, the horizontal shortening attributable to the Sierra Madre fault accounts for only ~33% of the observed shortening across the basin, leaving ~67% of the shortening to be accounted for elsewhere. Herein we present a suite of models that test possible shortening mechanisms to account for this strain deficit. The models incorporate a range of fault geometries and have a layered structure with variable vertical and horizontal rheologies. The models demonstrate how lower-crust rheology and the presence of a low rigidity, anelastically deforming sedimentary basin affects the dissipation of stress imposed on the viscous layers by elastic failure of the faults. We found that viscoelastic models with a single fault, vertically strong crust and a compliant sedimentary basin yield a horizontal velocity profile that best matches the geodetically observed velocity profile across the Los Angeles Basin. Our models also indicate that we are still not accounting for all of the observed deformation. Therefore, more complex models that include both laterally varying rheologies and frictional properties on faults must be considered.  相似文献   

Neogastroplites meets Metengonoceras: morphological response of an endemic hoplitid ammonite to a new invader in the mid-Cretaceous Mowry Sea of North America     

Margaret M. Yacobucci 《Cretaceous Research》2004,25(6):122

High levels of morphological variability have been attributed to various ecological and developmental mechanisms, including selection for ecological generalists in an unstable environment, inherent developmental plasticity, and the absence of competitors in an empty ecosystem. The late Albian–early Cenomanian hoplitid ammonite Neogastroplites of the Mowry Sea of North America, notorious for its extreme levels of intraspecific variability, is used as a test case of the idea that a lack of competitors promotes variability. The group responded to the invasion of a second ammonite, the engonoceratid Metengonoceras, into the Mowry Sea by spreading into a previously unoccupied region of morphospace, suggesting possible ecological character displacement and a release from constructional constraints. However, morphological variability did not decrease, as would be predicted by the competition model. The variability of Neogastroplites might instead result from environmental instability or developmental flexibility.  相似文献   

Lags in vegetation response to greenhouse warming   总被引：12，自引：0，他引：12  

Margaret B. Davis 《Climatic change》1989,15(1-2):75-82

Fossil pollen in sediments documents vegetation responses to climatic changes in the past. Beech (Fagus grandifolia), with animal-dispersed seeds, moved across Lake Michigan or around its southern margin, becoming established in Wisconsin about 1000 years after populations were established in Michigan. Hemlock (Tsuga canadensis), with wind-dispersed seeds, colonized a 50,000 km² area in northern Michigan between 6000 and 5000 years ago. These tree species extended ranges northward at average rates of 20–25 km per century. To track climatic changes in the future, caused by the greenhouse effect, however, their range limit would need to move northward 100 km per °C warming, or about 300 km per century, an order of magnitude faster than range extension in the past. Yet range extension in the future would be less efficient than in the past, because advance disjunct colonies have been extirpated by human disturbance, and because the seed source is reduced due to reductions in tree populations following logging. Many species of trees may not be able to disperse rapidly enough to track climate, and woodland herbs, which have less efficient seed dispersal mechanisms, may be in danger of extinction.  相似文献   

“The Deterministic Side of Geostatistics” by A. G. Journel     

Margaret Armstrong 《Mathematical Geosciences》1985,17(8):855-859

  相似文献   

Gases and trace elements in soils at the North Silver Bell deposit, Pima County, Arizona     

Margaret E. Hinkle  Clifford A. Dilbert 《Journal of Geochemical Exploration》1984,20(3):323-336

Soil samples were collected over the North Silver Bell porphyry copper deposit near Tucson, Arizona. Volatile elements and compounds in gases derived from the soils and metallic elements in the soils were analyzed in order: (1) to see which volatile constituents of the soils might be indicative of the ore body or the alteration zones; and (2) to distinguish the ore and alteration zones by comparison of trace elements in the soil.Plots of analytical data on trace elements in soils indicated a typical distribution pattern for metals around a porphyry copper deposit, with copper, molybdenum, and arsenic concentrations higher over the ore body, and zinc, lead, and silver concentrations higher over the alteration zones.Higher than average concentrations of helium, carbon disulfide, and sulfur dioxide adsorbed on soils were found over the ore body, whereas higher concentrations of carbon dioxide and carbonyl sulfide were found over the alteration zones.  相似文献   

Internal and external validation of vulnerability indices: a case study of the Multivariate Nursing Home Vulnerability Index     

Wilson  Matthew  Lane  Sandi  Mohan  Raghuveer  Sugg  Margaret 《Natural Hazards》2020,100(3):1013-1036

Natural Hazards - As the frequency of natural disasters increases, there has been an emphasis on vulnerability index creation studies. In this study, we test the validity of vulnerability indices...  相似文献