Based on the available toxicity data and the concentrations of DDTs and HCHs in surface water from the upper reaches of the Huaihe River, overlapping areas of probability density and margin of safety (MOS10) were used to estimate the risk levels of DDTs and HCHs to aquatic organisms. The overlapping areas of α-HCH, γ-HCH, p,p′-DDE, p,p′-DDD, and p,p′-DDT were found to be 9.3 × 10?5, 4.6 × 10?3, 4.3 × 10?2, 2.2 × 10?2, and 4.2 × 10?2, respectively. The risks from DDTs were higher than those from HCHs, the risk from α-HCH being the smallest. The MOS10 values of α-HCH, γ-HCH, p,p′-DDE, p,p′-DDD, and p,p′-DDT were 2.6 × 103, 97, 5.9, 15, and 8.6, respectively, i.e. greater than 1.0, indicating limited overlaps between the distributions of exposure concentrations and of toxicity data, and thus minimal ecological risk. Health risk calculations based on incremental lifetime risks for HCHs and DDTs were conducted to evaluate human cancer risk and non-carcinogenic hazard. The total cancer risks from organochlorine pesticides (OCPs) in the studied area were in the range of 10?8–10?7, lower than the baseline value of acceptable risk (10?6). Non-carcinogenic hazard indices of OCPs ranging from 10?6 to 10?5 were much lower than the threshold values (1.0). These results suggest that the water from the upper reaches of the Huaihe River does not pose any health risk for local residents using river water as a source for drinking water. 相似文献
Some species have disproportionate influence on assemblage structure, given their numbers or biomass. Most examples of such "strong interactors" come from small-scale experiments or from observations of the effects of invasive species. There is evidence that entire avian assemblages in open woodlands can be influenced strongly by individual species over very large areas in eastern Australia, with small-bodied species (< 50 g) being adversely affected. We used data from repeated surveys in 371 sites in seven districts across a region from Victoria to Queensland (> 2000 km). A series of linked Bayesian models was used to identify large-bodied (> or = 50 g) bird species that were associated with changes in occurrence and abundance of small-bodied species. One native species, the Noisy Miner (Manorina melanocephala; family Meliphagidae), was objectively identified as the sole large-bodied species having similar detrimental effects in all districts, depressing occurrence of 57 of 71 small-bodied species. Adverse effects on abundances of small-bodied species were profound when the Noisy Miner occurred with mean site abundances > or = 1.6 birds/2 ha. The Noisy Miner may be the first species to have been shown to influence whole-of-avifauna assemblage structure through despotic aggressiveness over subcontinental scales. These substantial shifts in occurrence rates and abundances of small-bodied species flow on to alter species abundance distributions of entire assemblages over much of eastern Australia. 相似文献
Mitochondrial (mt) DNA control region sequences were analyzed for 249 Atlantic and Mediterranean loggerhead turtles (Carettacaretta Linnaeus, 1758) to elucidate nesting population structure and phylogeographic patterns. Ten haplotypes were resolved among
individuals sampled between 1987 and 1993, from ten major loggerhead nesting areas in the region. Two distinct phylogenetic
lineages were distinguished, separated by an average of 5.1% sequence divergence. Haplotype frequency comparisons between
pairs of populations showed significant differentiation between most regional nesting aggregates and revealed six demographically
independent groups, corresponding to nesting beaches from: (1) North Carolina, South Carolina, Georgia and northeast Florida,
USA; (2) southern Florida, USA; (3) northwest Florida, USA; (4) Quintana Roo, Mexico; (5) Bahia, Brazil; and (6) Peloponnesus
Island, Greece. The distribution of mtDNA haplotypes is consistent with a natal homing scenario, in which nesting colonies
separated by a few hundred kilometers represent isolated reproductive aggregates. However, a strong exception to this pattern
was observed in the first group defined by mtDNA data (North Carolina to northeast Florida), which included samples from four
nesting locations spread across thousands of kilometers of coastline. These locations were characterized by a single haplotype
in 104 out of 105 samples, providing inadequate resolution of population divisions. In view of the subdivisions observed elsewhere,
we attribute the lack of differentiation between North Carolina and northeast Florida to recent colonization of these warm
temperate coastlines (after the Wisconsin glaciation) not to ongoing gene flow among spatially distinct nesting locations.
The relationships among observed haplotypes suggest a biogeographic scenario defined by climate, natal homing, and rare dispersal
events. The redefined relationships among nesting aggregations in the western Atlantic region (southeastern USA and adjacent
Mexico) prompt a reconsideration of management strategies for nesting populations and corresponding habitats in this region.
Received: 28 October 1996 / Accepted: 24 October 1997 相似文献
Large areas of public lands administered by the Bureau of Land Management and located in arid regions of the southwestern United States are being considered for the development of utility-scale solar energy facilities. Land-disturbing activities in these desert, alluvium-filled valleys have the potential to adversely affect the hydrologic and ecologic functions of ephemeral streams. Regulation and management of ephemeral streams typically falls under a spectrum of federal, state, and local programs, but scientifically based guidelines for protecting ephemeral streams with respect to land-development activities are largely nonexistent. This study developed an assessment approach for quantifying the sensitivity to land disturbance of ephemeral stream reaches located in proposed solar energy zones (SEZs). The ephemeral stream assessment approach used publicly-available geospatial data on hydrology, topography, surficial geology, and soil characteristics, as well as high-resolution aerial imagery. These datasets were used to inform a professional judgment-based score index of potential land disturbance impacts on selected critical functions of ephemeral streams, including flow and sediment conveyance, ecological habitat value, and groundwater recharge. The total sensitivity scores (sum of scores for the critical stream functions of flow and sediment conveyance, ecological habitats, and groundwater recharge) were used to identify highly sensitive stream reaches to inform decisions on developable areas in SEZs. Total sensitivity scores typically reflected the scores of the individual stream functions; some exceptions pertain to groundwater recharge and ecological habitats. The primary limitations of this assessment approach were the lack of high-resolution identification of ephemeral stream channels in the existing National Hydrography Dataset, and the lack of mechanistic processes describing potential impacts on ephemeral stream functions at the watershed scale. The primary strength of this assessment approach is that it allows watershed-scale planning for low-impact development in arid ecosystems; the qualitative scoring of potential impacts can also be adjusted to accommodate new geospatial data, and to allow for expert and stakeholder input into decisions regarding the identification and potential avoidance of highly sensitive stream reaches. 相似文献
This article presents a review of major empirical research on environmental justice. Forty-two empirical research studies
spanning three decades were evaluated and categorized on the basis of how well they meet reasonable scientific standards.
Twelve of those studies are described and critiqued in detail, and an overview of trends in the literature is presented. The
author concludes that the empirical foundations of environmental justice are so underdeveloped that little can be said with
scientific authority regarding the existence of geographical patterns of disproportionate distributions and their health effects
on minority, low-income, and other disadvantaged communities. If environmental managers and policy-makers do not recognize
the high levels of empirical uncertainty surrounding the issue, they are apt to attribute an empirically unwarranted level
of concreteness to the empirical research findings, thus leading to poorly conceptualized and therefore potentially harmful
policy and management decisions. 相似文献
Molecular genetic surveys of marine fishes have revealed that some widely distributed species are actually a composite of multiple evolutionary lineages. This is apparent in the round herrings (genus Etrumeus), wherein a globally distributed taxon (Etrumeus sadina Mitchill 1814) has proven to contain at least seven valid taxa, with more likely awaiting discovery. Here, we survey evolutionary lineages of the nominal E. sadina (formerly E. teres, a junior synonym) across the southern temperate zone of Australia, a marine region divided into three biogeographic provinces based primarily on the distribution of intertidal faunas. Results from morphological and mitochondrial DNA data reveal two evolutionary lineages corresponding to eastern and southwestern provinces (d = 0.007 for cytochrome c oxidase subunit I and d = 0.017 for cytochrome b), possibly initiated by the Bassian Isthmus between Australia and Tasmania during low sea-level stands. The Australian round herring is also genetically distinct from the nearest congeneric forms in the Indian and Pacific Oceans, with a corresponding modal difference in gill-raker counts in most cases. Based on these data, we resurrect the title Etrumeus jacksoniensis for the Australian round herring. While the Bassian Isthmus may have initiated the partition of evolutionary lineages within Australia, additional oceanographic and ecological factors must reinforce this separation in order to maintain diagnostic genetic differences along a continuous temperate coastline. 相似文献
Current taxonomy indicates a single global species of the Great Barracuda (Sphyraena barracuda) despite differences in color and behavior between Atlantic and Pacific forms. To investigate these differences and qualify
the dispersal characteristics of this unique coastal–pelagic teleost (bony fish), we conducted a global phylogeographic survey
of 246 specimens from thirteen sampling locations using a 629-base pair fragment of mtDNA cytochrome b. Data indicate high overall gene flow in the Indo-Pacific over large distances (>16,500 km) bridging several biogeographic
barriers. The West Atlantic population contains an mtDNA lineage that is divergent from the Indo-Pacific (d = 1.9%), while the East Atlantic (N = 23) has two mutations (d = 0.6%) apart from the Indo-Pacific. While we cannot rule out distinct evolutionary partitions among ocean basins based on
behavior, coloration, and near-monophyly between Atlantic and Indo-Pacific subpopulations, more investigation is required
before taxonomic status is revised. Overall, the pattern of high global dispersal and connectivity in S. barracuda more closely resembles those reported for large oceanic predators than reef-associated teleosts. 相似文献
Selective withdrawal is commonly implemented in nonlinearly stratified ambient, which typically has stratified ambient conditions, for purposes of controlling quality. A floating intake is applied as an effective facility of selective withdrawal. However, the outflow dynamics of a floating intake in a nonlinearly stratified ambient have been disregarded, which has a significant effect on the outflow water quality of a reservoir. Experiments were conducted to investigate the effect of thermal stratification on the flow characteristics using particle image velocimetry at three temperature distributions (no stratification, weak stratification and strong stratification). The flow fields upstream of the floating intake showed that the withdrawal layer was formed inhibited by the thermal stratification. And strong stratification produced the thinner withdrawal layer thickness, leading to a larger nonuniform coefficient of the velocity profile. To quantitatively describe the velocity profiles, formulas of dimensionless velocity profiles were proposed. The flow developments were analysed, and the virtual control points located 0.56d above the floating intake (where d is the straight pipe diameter of the floating intake) were obtained. The positions of virtual control points mainly depended on the withdrawal discharge. The decay rate of the velocity along the horizontal line passing through the virtual control point was inversely proportional to the stratification intensity.