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771.
772.
The practice of contaminant transport and remediation has shown significant progress in recent years. However, despite the
significant progress made, remediation efforts are often delayed by extremely long breakthrough curve tails that render efforts
to bring the level of contaminants below the regulatory standards inefficient. One hypothesis is that these long tails are
due to the reservoir-like slow diffusive processes in soil micropore zones. This study compares the effects of micropores
at macroscopic and microscopic levels and establishes a link between these approaches for validation and calibration purposes.
The link between macroscopic and microscopic levels is established through comparisons and testing of the two models while
incorporating appropriate scale and boundary effects. Despite the differences in conceptual approaches and simulation time,
the two approaches rendered meaningful results. The link helps forecast the effects of micropore zone transport processes
in the subsurface efficiently and thus allows development of numerical tools that could contribute towards more efficient
remediation design. 相似文献
773.
An air quality monitoring network (AQMN) usually performs the basic function of assessment of regional air quality and demonstration of compliance with ambient air quality standards in an urban area. Different pollutants, however, may present different characteristic variabilities due to their specific emission patterns, rates of diffusion, and transport and transformation behaviors. But the costs of siting in a pollutant-specific monitoring network would be higher than that for a common network with respect to several pollutants monitored simultaneously. This paper presents a survey of multi-pollutant design principles and optimal searches for siting patterns of an AQMN using both simulation and optimization models as a combined tool. While conservative, quasi-stable, and reactive pollutants are considered in the design principles, cost, coverage effectiveness, and spatial correlation characteristics are included in the multi-criteria decision making process. For illustrative purpose, a series of technical settings and two types of objectives were examined in the case study for the city of Kaohsiung in Taiwan. 相似文献
774.
C. A. Bishop N. A. Mahony J. Struger P. Ng K. E. Pettit 《Environmental monitoring and assessment》1999,57(1):21-43
Significantly lower anuran species diversity and density was recorded in a vegetable growing area relative to upstream and downstream sites in the Holland River watershed, Ontario, Canada. Egg hatching success and tadpole deformity rates of American toads (Bufo americanus americanus), green frogs (Rana clamitans melanota) and northern leopard frogs (Rana pipiens) eggs in water from field sites and control water were assessed. Compared to the control and the upstream site, the total abnormality rate (unhatched eggs plus deformed tadpoles) was higher for American toads in water from the agricultural and downstream sites. Total abnormality was higher in green frog eggs in water from the agricultural site and a downstream site. Trace concentrations of organophosphorus pesticides were detected most often in agricultural zone water and sediments than in upstream and downstream sites. Organochlorine pesticide residues, especially in agricultural zone samples, exceeded the no effect level guidelines for the protection of aquatic life. Ammonia, phosphorus, particulates, BOD and TKN were highest in the agricultural zone. Significant correlations between these parameters and anuran development suggest nutrient run-off as a causal or contributing factor in lower anuran diversity, density and reproductive success of American toads and green frogs in the site dominated by agriculture. 相似文献
775.
Steven C. Schimmel Sandra J. Benyi Charles J. Strobel 《Environmental monitoring and assessment》1999,56(1):27-49
Data from the Environmental Protection Agency's (EPA) Environmental Monitoring and Assessment Program (EMAP) from 1990 to 1993 were used to assess the condition of the Long Island Sound (LIS) estuary. Ambient water, sediment and biota were collected during the summer months from 53 LIS stations using an unbiased sampling design. The design consists of two LIS subunits, LIS proper, and small estuaries (<2.6 km2) at the margins of the Sound. Selected indicators of condition included: benthic species composition, abundance and biomass; fish species composition and gross external pathology; sediment physical and chemical characterization and sediment toxicity; and water clarity and quality. Results of the four-year sampling indicated that 28(±11)% of the areal extent of LIS proper had a benthic index < zero (impacted) and 51(±12)% of the area of small estuaries was impacted. Analysis of the results of other indicators also shows that small estuaries were particularly affected. For example, 42(±10)% of the areal extent of small estuaries exhibited sediment toxicity, and significant chemical contamination was evident in 22% of the area of small estuaries. Low dissolved oxygen (D.O.) concentrations (<5 ppm), however, appeared to affect only the deeper open waters of western LIS. Approximately 48(±12)% of the areal extent of LIS proper documented exposure to at least moderate D.O. stress (<5 ppm). The overall results of this monitoring study indicate that significant anthropogenic impacts have occurred in LIS and that if remediation was to take place, specific localized sediment problems would need attention. Point source and non-point source nutrient inputs to the Sound, which are believed to be the primary causative factor for the observed hypoxic conditions, would also need attention. 相似文献
776.
Jacobus C. Biesmeijer Mark G. L. van Nieuwstadt Saskia Lukács Marinus J. Sommeijer 《Behavioral ecology and sociobiology》1998,42(2):107-116
Social insect foragers have to make foraging decisions based on information that may come from two different sources: information
learned and memorised through their own experience (“internal” information) and information communicated by nest mates or
directly obtained from their environment (“external” information). The role of these sources of information in decision-making
by foragers was studied observationally and experimentally in stingless bees of the genus Melipona. Once a Melipona forager had started its food-collecting career, its decisions to initiate, continue or stop its daily collecting activity
were mainly based upon previous experience (activity on previous days, the time at which foraging was initiated the day(s)
before, and, during the day, the success of the last foraging flights) and mediated through direct interaction with the food
source (load size harvested and time to collect a load). External information provided by returning foragers advanced the
start of foraging of experienced bees. Most inexperienced bees initiated their foraging day after successful foragers had
returned to the hive. The start of foraging by other inexperienced bees was stimulated by high waste-removal activity of nest
mates. By experimentally controlling the entries of foragers (hence external information input) it was shown that very low
levels of external information input had large effect on the departure of experienced foragers. After the return of a single
successful forager, or five foragers together, the rate of forager exits increased dramatically for 15 min. Only the first
and second entry events had large effect; later entries influenced forager exit patterns only slightly. The results show that
Melipona foragers make decisions based upon their own experience and that communication stimulates these foragers if it concerns the
previously visited source. We discuss the organisation of individual foraging in Melipona and Apis mellifera and are led to the conclusion that these species behave very similarly and that an information-integration model (derived
from Fig. 1) could be a starting point for future research on social insect foraging.
Received: 16 April 1997 / Accepted after revision: 30 August 1997 相似文献
777.
Bushcricket song structure and predation by the acoustically orienting parasitoid fly Therobia leonidei (Diptera: Tachinidae: Ormiini) 总被引:2,自引:0,他引:2
Gerlind U. C. Lehmann Klaus-Gerhard Heller 《Behavioral ecology and sociobiology》1998,43(4-5):239-245
Males of most bushcricket species produce acoustic advertisement signals to attract females for mating. These signals can
also increase conspicuousness to predators. In the genus Poecilimon (Orthoptera: Phaneropterinae) males are attacked by the parasitoid fly Therobia leonidei (Diptera: Tachinidae: Ormiini) which locates males by their calls. In Greece T.leonidei parasitizes several Poecilimon species with different song structures: we examined whether host choice is related to song structure by comparing parasitism
rates in two closely related Poecilimon species. One of these species produces monosyllabic songs, the songs of the other species being polysyllabic. The tachinid
fly parasitized the polysyllabic species to a greater extent. We demonstrate in a field-experiment that this preference for
the polysyllabic species does not depend on local adaptations of the fly. The most probable explanation for the preference
of the fly for the polysyllabic singing species seems to be better detection of longer songs. This result is discussed in
the context of male song evolution.
Received: 4 November 1997 / Accepted after revision: 22 March 1998 相似文献
778.
779.