Why do most tropical animals reproduce seasonally? Testing hypotheses on an Australian snake

Most species reproduce seasonally, even in the tropics where activity occurs year-round. Squamate reptiles provide ideal model organisms to clarify the ultimate (adaptive) reasons for the restriction of reproduction to specific times of year. Females of almost all temperate-zone reptile species produce their eggs or offspring in the warmest time of the year, thereby synchronizing embryogenesis with high ambient temperatures. However, although tropical reptiles are freed from this thermal constraint, most do not reproduce year-round. Seasonal reproduction in tropical reptiles might be driven by biotic factors (e.g., peak periods of predation on eggs or hatchlings, or food for hatchlings) or abiotic factors (e.g., seasonal availability of suitably moist incubation conditions). Keelback snakes (Tropidonophis mairii, Colubridae) in tropical Australia reproduce from April to November, but with a major peak in May-June. Our field studies falsify hypotheses that invoke biotic factors as explanations for this pattern: the timing of nesting does not minimize predation on eggs, nor maximize food availability or survival rates for hatchlings. Instead, our data implicate abiotic factors: female keelbacks nest most intensely soon after the cessation of monsoonal rains when soils are moist enough to sustain optimal embryogenesis (wetter nests produce larger hatchlings, that are more likely to survive) but are unlikely to become waterlogged (which is lethal to eggs). Thus, abiotic factors may favor seasonal reproduction in tropical as well as temperate-zone animals.     

Dark, bitter-tasting nectar functions as a filter of flower visitors in a bird-pollinated plant

Floral nectar is offered by plants to animals as a reward for pollination. While nectar is typically a clear liquid containing sugar and trace amounts of amino acids, colored nectar has evolved in several plant families. Here we explore the functional significance of the phenolic compounds that impart a dark brown color to the nectar of the South African succulent shrub Aloe vryheidensis. Flowers of this aloe are visited for their nectar by a suite of short-billed birds that are occasional nectarivores, including bulbuls, white-eyes, rock thrushes, and chats. Dark-capped Bulbuls were more likely to probe model flowers containing dark nectar than those containing clear nectar, suggesting a potential signaling function for dark nectar. However, the main effect of the phenolics appears to be to repel "unwanted" nectarivores that find their bitter taste unpalatable. Nectar-feeding honey bees and sunbirds are morphologically mismatched for pollinating A. vryheidensis flowers and strongly reject its nectar. However, the frugivorous and insectivorous birds that effectively pollinate this aloe are seemingly unaffected by the nectar's bitter taste. Thus the dark phenolic component of the nectar appears to function as a floral filter by attracting some animals visually and deterring others by its taste.     

Processes influencing secondary aerosol formation in the San Joaquin Valley during winter

Air quality data collected in the California Regional PM10/ PM(2.5) Air Quality Study (CRPAQS) are analyzed to qualitatively assess the processes affecting secondary aerosol formation in the San Joaquin Valley (SJV). This region experiences some of the highest fine particulate matter (PM(2.5)) mass concentrations in California (< or = 188 microg/m3 24-hr average), and secondary aerosol components (as a group) frequently constitute over half of the fine aerosol mass in winter. The analyses are based on 15 days of high-frequency filter and canister measurements and several months of wintertime continuous gas and aerosol measurements. The phase-partitioning of nitrogen oxide (NO(x))-related nitrogen species and carbonaceous species shows that concentrations of gaseous precursor species are far more abundant than measured secondary aerosol nitrate or estimated secondary organic aerosols. Comparisons of ammonia and nitric acid concentrations indicate that ammonium nitrate formation is limited by the availability of nitric acid rather than ammonia. Time-resolved aerosol nitrate data collected at the surface and on a 90-m tower suggest that both the daytime and nighttime nitric acid formation pathways are active, and entrainment of aerosol nitrate formed aloft at night may explain the spatial homogeneity of nitrate in the SJV. NO(x) and volatile organic compound (VOC) emissions plus background O3 levels are expected to determine NO(x) oxidation and nitric acid production rates, which currently control the ammonium nitrate levels in the SJV. Secondary organic aerosol formation is significant in winter, especially in the Fresno urban area. Formation of secondary organic aerosol is more likely limited by the rate of VOC oxidation than the availability of VOC precursors in winter.     

Wintertime vertical variations in particulate matter (PM) and precursor concentrations in the San Joaquin Valley during the California Regional Coarse PM/Fine PM Air Quality Study

Air quality monitoring was conducted at a rural site with a tower in the middle of California's San Joaquin Valley (SJV) and at elevated sites in the foothills and mountains surrounding the SJV for the California Regional PM10/ PM2.5 Air Quality Study. Measurements at the surface and n a tower at 90 m were collected in Angiola, CA, from December 2000 through February 2001 and included hourly black carbon (BC), particle counts from optical particle counters, nitric oxide, ozone, temperature, relative humidity, wind speed, and direction. Boundary site measurements were made primarily using 24-hr integrated particulate matter (PM) samples. These measurements were used to understand the vertical variations of PM and PM precursors, the effect of stratification in the winter on concentrations and chemistry aloft and at the surface, and the impact of aloft-versus-surface transport on PM concentrations. Vertical variations of concentrations differed among individual species. The stratification may be important to atmospheric chemistry processes, particularly nighttime nitrate formation aloft, because NO2 appeared to be oxidized by ozone in the stratified aloft layer. Additionally, increases in accumulation-mode particle concentrations in the aloft layer during a fine PM (PM2.5) episode corresponded with increases in aloft nitrate, demonstrating the likelihood of an aloft nighttime nitrate formation mechanism. Evidence of local transport at the surface and regional transport aloft was found; transport processes also varied among the species. The distribution of BC appeared to be regional, and BC was often uniformly mixed vertically. Overall, the combination of time-resolved tower and surface measurements provided important insight into PM stratification, formation, and transport.     

Probabilistic biokinetic modelling of radiocaesium uptake in Arctic seal species: verification of modelled data with empirical observations

The necessity to provide information about radionuclide concentrations in Arctic marine species has been heightened in recent years due to a number of accidents in Arctic regions involving nuclear vessels and the presence of a large number of potential radioactive contamination sources. The provision for such information is largely dependent on the use of radionuclide uptake and transfer models. The uptake of radionuclides in Arctic seal species in this study has been modelled using a probabilistic biokinetic approach. In this paper, model results are compared with empirical data from relevant samples taken within the Arctic region. Results indicate that the model performs well when estimating concentrations of (137)Cs in two seal species for both median values and reproduction of the distribution of data values, but not as well for a third seal species. Likely factors affecting the results are the probability density functions used for the input parameters.     

Comparison of the particle size distribution of heavy-duty diesel exhaust using a dilution tailpipe sampler and an in-plume sampler during on-road operation

Originally constructed to develop gaseous emission factors for heavy-duty diesel trucks, the U.S. Environmental Protection Agency's (EPA) On-Road Diesel Emissions Characterization Facility has been modified to incorporate particle measurement instrumentation. An electrical low-pressure impactor designed to continuously measure and record size distribution data was used to monitor the particle size distribution of heavy-duty diesel truck exhaust. For this study, which involved a high-mileage (900,000 mi) truck running at full load, samples were collected by two different methods. One sample was obtained directly from the exhaust stack using an adaptation of the University of Minnesota's air-ejector-based mini-dilution sampler. The second sample was pulled from the plume just above the enclosed trailer, at a point approximately 11 m from the exhaust discharge. Typical dilution ratios of about 300:1 were obtained for both the dilution and plume sampling systems. Hundreds of particle size distributions were obtained at each sampling location. These were compared both selectively and cumulatively to evaluate the performance of the dilution system in simulating real-world exhaust plumes. The data show that, in its current residence-time configuration, the dilution system imposes a statistically significant bias toward smaller particles, with substantially more nanoparticles being collected than from the plume sample.     

Planning,Designing, Operating,and Regulating a Geologic Sequestration Repository as an Underground Landfill—A Review

ABSTRACT

Geologic sequestration appears to be a technically feasible method of storing carbon dioxide in underground aquifers in order to lower greenhouse gas emissions into the atmosphere. The overall feasibility of geologic sequestration is still in question and as such, has been the focus of intense research over the past decade. Researchers have looked to the oil/gas industry and water well industry for lessons learned and technical knowledge, however, a better industry to emulate may well be the waste industry. Viewing geologic sequestration repositories as underground landfills has a great many benefits. First, there is a plethora of existing research and investigations that are directly analogous to geologic sequestration projects. Second, the regulatory framework is rather mature and can be easily adapted to serve geologic sequestration. This paper conducts an extensive literature search of the environmental, waste, and geologic sequestration literature to ascertain planning, design, and operational methodologies, lessons learned, and concepts that are directly useful for geologic sequestration to improve the technical and regulatory framework. Lastly, the paper uses a hypothetical underground landfill geologic sequestration site (ULGSS) in Florida, USA to discuss some of the findings and implications from the literature. It is concluded that there are a number of literature findings from the waste and environmental arena that should be adapted for geologic sequestration.

IMPLICATIONS Geologic sequestration is a promising solution for greenhouse gas control. This work supports that notion but suggests further improvements to the technical and regulatory framework based upon an extensive review of the waste management and environmental literature. The improvements include suggestions in the areas of permitting, site selection, operations, cost accounting, and special waste handling. Some of these improvements are discussed using a hypothetical project site in Florida, USA.     

Quality assurance and quality control data validation procedures used for the Love Canal and Dallas lead soil monitoring programs

Public awareness of soils contamination has increased in recent years due in part to the notoriety associated with the indiscriminate release, packaging, transporting and disposal of hazardous materials. In 1980, and again in 1982, the U.S. Environmental Protection Agency (EPA) was responsible for designing, implementing and conducting environmental monitoring programs at Love Canal in Niagara Falls, New York, and in Dallas, Texas, that dealt with suspected contaminated soils. Both of these monitoring programs were conducted over a relatively short time with the collection and analysis of over 4000 soil samples. The methods employed by the Environmental Protection Agency for providing soil data that was scientifically valid and of defensible quality for each of these monitoring programs are presented. Also, methods for identifying data bias, its precision and its uncertainty are identified.     

Redesigning the FDMT Food Chain Transfer Model: Now Probabilistically Enabled and Fully Flexible

Environmental Modeling & Assessment - In Europe, the two main nuclear accident response decision support systems in use are ARGOS and JRODOS, both of which make use of the FDMT (Food Chain and...