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931.
A comparison of metals in sediments and water in the River Nahr-Ibrahim,Lebanon: 1996 and 1999 总被引:1,自引:0,他引:1
Rivers whose basins are underlain by carbonate rocks exhibit high pH, lower desorption of metals and possess high buffering capacity against acidic inputs to the river. The catchment of River Nahr-Ibrahim, Lebanon, is largely underlain by limestone. Compared to neighbouring countries, Lebanon is relatively fortunate since precipitation is high. However, recently a warming in temperature and a drop in precipitation has occurred, thus causing low water levels in rivers. The objective of this study is to investigate the variation of the total metal content (Fe, Mn, Zn, Cu, Pb and Cd) in bed sediments and water of River Nahr-Ibrahim between 1996 and 1999 (two years); and relate these variations to the effect of changes in human activities and/or due to the variations of precipitation rate, temperature and pH of water. Bed load sediments and stream water were collected simultaneously from five sampling sites. Water pH and temperature were determined in situ. Sediment samples were dried at room temperature and sieved; the sediment size <75 m size was retained. Water was analysed for major constituents and trace metals. Metals were extracted from sediments with aqua regia. Metal concentration in water and sediments were determined using ICP-MS technique. Data revealed a drop in metal concentrations (Zn, Cu, Pb, Cd) in sediments at quarry site after its closure. The decrease in precipitation rate, lowering the level of water and the dilution of industrial discharges and decrease in water pH led most probably to the desorption of metals from sediments into the water. 相似文献
932.
A Transdisciplinary Approach to Conservation Land Acquisition 总被引:2,自引:0,他引:2
Brian Czech 《Conservation biology》2002,16(6):1488-1497
933.
934.
Brian A. Davies 《Environmental geochemistry and health》2001,23(1):79-84
Instructions for Authors
Environmental Geochemistry and Health 相似文献935.
Conserving Biological Diversity through Ecosystem Resilience 总被引:40,自引:0,他引:40
Brian Walker 《Conservation biology》1995,9(4):747-752
Confusion over the term ecological redundancy (Walker 1992) requires that the concept be clarified in order to advance the developing theory that maintaining ecosystem function conserves biological diversity. The species approach to conserving biological diversity assumes that the species in trouble are already identified. The ecosystem approach attempts to deal with the problem of conserving all the species in an ecosystem, including those not yet known. This is best achieved by ensuring that the ecosystem continues to function approximately as it has by maintaining its essential structure. Ecosystem stability (the probability of all species persisting) is enhanced if each important functional group of organisms (important for maintaining function and structure) comprises several ecologically equivalent species, each with different responses to environmental factors. In this sense ecological redundancy is good because it enhances ecosystem resilience, but functionally important groups (guilds, functional types) that have only one or very few species deserve priority conservation attention because their functions could be quickly lost with species extinctions. 相似文献
936.
Symmetric fights as a measure of escalation potential in a symbiotic,territorial snapping shrimp 总被引:1,自引:0,他引:1
Summary The shrimp Alpheus armatus territorially defends the sea anemone it occupies, using as a weapon its large, specially modified snapping claw. This behavior was studied in experimental contests which were symmetric (matched individuals) with respect to sex, size, and residency. Characteristics of these contests were compared for two size-classes of male and female shrimp.There were no significant differences between these groups of shrimp in the number of bouts required to establish dominance or in the number of snaps exchanged. Large females had shorter contests than either small or large males, and losers of contests between large females were injured more frequently and more severely.This distinctiveness of large female contests could be interpreted as evidence that (i) controlling anemones is more important for large females, (ii) injuries are less important for large females, or (iii) large females lose the ability to assess one another because their contests are less frequent.If injuries are an accurate measure of the most important costs associated with fighting, then these results indicate that short contests are not necessarily the least costly, and that females can be more aggressive than males, as measured by escalation potential, in sexually selected species. 相似文献
937.
938.
Catherine E. deRivera Natasha Gray Hitchcock Sarah J. Teck Brian P. Steves Anson H. Hines Gregory M. Ruiz 《Marine Biology》2007,150(6):1275-1288
Introduced populations can cause ecological and economic damage and are difficult to eradicate once they have established.
It is therefore important to be able to predict both where species may become established and their capacity to spread within
recipient regions. Here, we use a new method to assess potential for intraregional spread of a marine crab introduced to North
America, Carcinus maenas. We determined survivorship and development rates throughout a range of temperatures in the laboratory for C. maenas larvae from non-native populations on the Atlantic and Pacific coasts of North America. The larvae exhibited narrower physiological
tolerances than adults, and no lab-cultured larvae completed larval development below 10.0°C or above 22.5°C. Survivorship
peaked at intermediate water temperatures of 12.5–20.0°C, and development time decreased with increasing temperatures within
this range. Based upon these laboratory development rates, we used nearshore sea-surface temperature data from both coasts
of North America to predict development times required for larvae at different months and sites. Taken together, survivorship
and development data indicate that C. maenas has the capacity to continue its northward spread and establish populations at numerous additional sites in North America.
Moreover, decadal temperature data at two Alaskan sites predicted little variability in development duration across years,
suggesting that development duration predictions are robust to interannual water temperature differences. 相似文献
939.
Source of lead in humans from Broken Hill mining community 总被引:3,自引:0,他引:3
Brian L. Gulson Donald Howarthl Karen J. Mizon Alistair J. Law Michael J. Korsch Jeffrey J. Davis 《Environmental geochemistry and health》1994,16(1):19-25
This paper documents the first precise lead isotope measurements for men, women and children from the same family in an attempt to determine the source of lead in their blood. The subjects reside in one of the world's largest lead mining cities, Broken Hill, NSW, Australia. Biological and environmental samples have been compared using isotopic compositions and lead contents. Adult males have isotopic profiles (or compositions) which appear to be related to their occupations. Adult females have low blood leads (<10 g dL–1) and their main source of lead is not from the mine dumps around which the city is built but probably from a mixture of petrol, food and perhaps water. The blood lead contents in children from 1 to 14 years old vary and are partly dependent on age. There is a moderate correlation of blood lead and isotopic compositions (r = 0.73) indicating that a significant component of blood lead derives from the mine dumps in children with elevated blood leads. Some children with blood leads <20 g dL–1, however, also have a dominant component of mine lead in their blood 相似文献
940.
Brian Miller Christen Wemmer Dean Biggins Richard Reading 《Environmental management》1990,14(6):763-769
Prairie dogs (Cynomys spp.) have been poisoned throughout this century because of grazing competition with livestock. Recent evidence showed these
early claims were exaggerated, but animal control was already entrenched in government policy. As a result, ongoing government
subsidized poisoning has reduced prairie dogs to about 2% of their former distribution. The reduction of prairie dogs diminished
species diversity in the arid grasslands of North America, including the potential extinction of the black-footed ferret (Mustela nigripes). Cost-benefit analysis revealed that poisoning costs more than any grazing benefits accrued. This analysis did not consider
the long-term costs of reversing ecosystem degradation, the intangible value of biological diversity as a public benefit,
or the depletion of biotic resources as a loss of actual or potential wealth. The government presently finances the poisoning
policy and the preservation of endangered species like the black-footed ferret, two apparently conflicting programs. We, therefore,
propose an integrated management plan that considers both interests. We propose that federal monies allocated to the poisoning
program be converted into a rebate for ranchers who manage livestock while preserving the prairie dog community. This would
redirect funds and personnel already allocated to prairie dog eradication to an incentive for ranchers who manage for livestock
and wildlife. Livestock interests and grassland biotic diversity would both benefit. 相似文献