Reduction of sampling and analytical errors for electron microscopic analysis of atmospheric aerosols

Electron microscopy-energy dispersive spectroscopy (EM/EDS) can be used to determine the elemental composition of individual particles. However, the accuracy with which atmospheric particle compositions can be quantitatively determined is not well understood. In this work we explore sources of sampling and analytical bias and methods of reducing bias. Sulfuric acid [H₂SO₄] and ammonium sulfate [(NH₄)₂SO₄] particles were collected on beryllium, silicon, and carbon substrates with similar deposition densities. While [(NH₄)₂SO₄] particles were observed on all substrates, [H₂SO₄] and ammonia-treated [H₂SO₄] particles could not be found on beryllium substrates. Interactions between the substrate and sulfuric acid particles are implicated. When measured with EM/EDS, [H₂SO₄] particles exposed to ammonia overnight were found having lower beam damage rates (0.000 ± 0.002 fraction s⁻¹) than those without any treatment (0.023 ± 0.006 fraction s⁻¹) For laboratory-generated [C₁₀H₆(SO₃Na)₂] particles, the composition determined using the experimental k-factors evaluated from independent particle standards of similar composition and size shows an error less than 20% for all constituents, while greater than 78% errors were found when k-factors were calculated from the theory. This study suggests (1) that sulfate beam damage can be reduced by exposure of atmospheric particle samples to ammonia before analysis, (2) that beryllium is not a suitable substrate for atmospheric particle analysis, and (3) calibration (k-factor determination) using particle standards of similar size and composition to particles present in the atmosphere shows promise as a way of improving the accuracy of quantitative EM analysis.     

Adjustment formulae for maternal serum alpha-fetoprotein,human chorionic gonadotropin,and unconjugated oestriol to maternal weight and smoking

Serum levels of alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), and un-conjugated oestriol (uE3) were measured in serum samples of 4131 non-smoking and 1018 smoking women during the second trimester of pregnancy. The levels of all three analytes decreased with increasing body weight. The AFP median was significantly increased in smokers in a dose-response association; hCG decreased by 21 per cent and uE3 decreased by 3 per cent in smokers in a non-dose-related fashion. Regression functions for adjustment of serum levels for weight and smoking should be considered in risk estimation for Down syndrome in order to give a woman's individual risk more precisely.     

Cystic hygroma and congenital diaphragmatic hernia: Early prenatal sonographic evaluation of Fryns' syndrome

We report a case of cystic hygroma and diffuse lymphangiectasia detected by sonogram at 12 weeks' gestation. Fetal karyotype was normal. At 20 weeks' gestation, herniation of the bowel into the chest was noted. At delivery, the infant was diagnosed as having Fryns' syndrome. This is the first reported case of Fryns' syndrome presenting with cystic hygroma.     

Performance of conventional remedial technology for treatment of MTBE and benzene at UST sites in Kansas

Groundwater at most underground storage tank (UST) spills sites in Kansas contains both methyl tertiary butyl ethylene (MTBE) and benzene, and both contaminants must be effectively treated to close the sites. Soil vacuum extraction, air sparging, and excavation are the most common treatment technologies in Kansas. To compare the relative performance of these conventional remedial technologies for treating MTBE as compared to benzene, 66 sites in the Kansas UST Trust Fund were identified that had initial concentrations of both MTBE and benzene above the reporting limit of 1 μg/L, and that had at least two rounds of analytical data. Sites were excluded from the comparison if the monitoring wells had free product. Of the 66 sites, 15 had met the clean‐up goal for benzene, and 50 had met the goal for MTBE. The extent of treatment for MTBE and benzene was calculated as the ratio of the highest concentration in any well at the site in the most recent round of sampling to the maximum concentration in any well at the site in the previous rounds of sampling. The extent of treatment was greater for MTBE (statistically significant at p = 0.032). The geometric mean of the extent of treatment in the 66 sites was 0.057 for MTBE, compared to 0.14 for benzene. In Kansas, conventional technologies removed MTBE from the source areas of groundwater plumes at least as effectively as they removed benzene. © 2003 Wiley Periodicals, Inc.     

Important meteorological data for use in risk assessment

This paper presents a methodology for the calculation of atmospheric stability classes in correlation with wind velocities for six sites of the Greek territory, namely Ellinikon (Athens), Elefsis, Megara, Heraklion, Chania and Patras, based on real data obtained from meteorological observations in these sites and on computations related with their geographic position. In addition to that, a comparison is presented of the atmospheric stability classes produced with online measurements for the Ellinikon (Athens) site with significant coincidence in the results.

These calculated values of the meteorological parameters (particularly of atmospheric stability) are most appropriate for uncertainty calculations in quantified risk assessments (QRAs) of hazardous installations sited in the above-mentioned areas, especially when risk and safety-related decisions need to be taken. Consequent results obtained with these parameters are more realistic compared to the “classical” assumption of D5/F2, which leads to significant diversification in the estimation of risk.     

Probabilistic modeling of young children's overall lead exposure in France: integrated approach for various exposure media

OBJECTIVES: Emissions of lead into the environment (and thus its environmental concentrations) have decreased in recent years. We sought to estimate the overall lead exposure of children aged 6 months to 6 years (the population group most exposed and most sensitive to lead) in France through the various media (air, food, water, soils, and dust) and the respective contributions of each medium to the total dose. We have focused on the general population, leaving aside specific risk factors such as deteriorated lead paints. METHODS: We used the most recent French intake data for food and water, and a daily ingested quantity selected from the literature for soils and dust. Contamination data came from the first total diet study of contaminant levels in France (2000-2001), from regulatory testing of tap water (2004), a literature review of lead in urban soils, and a pilot study (2005) of lead in dust. Air quality monitoring measurements showed that the contribution of air could now be safely ignored. Weekly exposure doses were estimated with Monte Carlo simulations. RESULTS: Median weekly exposure dose was 7.5 microg/kg bw.week for children aged 6 months to 3 years and 4.7 for those aged from 3-6 years. 95th percentiles were 13.5 and 8.7 microg/kg bw.week. Exposure came mainly from food. The principal uncertainties are associated with quantification limits in food and water, representativeness and traceability of tap water samples, and absence of recent data about urban soil contamination. CONCLUSIONS: These results differ quite notably from earlier estimates and highlight the need, especially for policy-making purposes, to update exposure measurements for this metal.     

PARAMETER UNCERTAINTY IN RAINFALL-RUNOFF MODELING FOR POLDER SYSTEM DESIGN1

ABSTRACT: An approach is developed for incorporating the uncertainty of parameters for estimating runoff in the design of polder systems in ungaged watersheds. Monte Carlo Simulation is used to derive a set of realizations of streamflow hydrographs for a given design rainstorm using the U. S. Soil Conservation Service (SCS) unit hydrograph model. The inverse of the SCS curve number, which is a function of the antecedent runoff condition in the SCS model, is the random input in the Monte Carlo Simulation. Monte Carlo realizations of streamfiow hydrographs are used to simulate the performance of a polder flood protection system. From this simulation the probability of occurrence of flood levels for a particular hydraulic design may be used to evaluate its effectiveness. This approach is demonstrated for the Pluit Polder flood protection system for the City of Jakarta, Indonesia. While the results of the application indicate that uncertainty in the antecedent runoff condition is important, the effects of uncertainty in rainfall data, in additional runoff parameters, such as time to peak, in the hydraulic design, and in the rainfall-runoff model selected should also be considered. Although, the SCS model is limited to agricultural conditions, the approach presented herein may be applied to other flood control systems if appropriate storm runoff models are selected.     

Revisiting the classics: considering nonconsumptive effects in textbook examples of predator-prey interactions

Predator effects on prey dynamics are conventionally studied by measuring changes in prey abundance attributed to consumption by predators. We revisit four classic examples of predator-prey systems often cited in textbooks and incorporate subsequent studies of nonconsumptive effects of predators (NCE), defined as changes in prey traits (e.g., behavior, growth, development) measured on an ecological time scale. Our review revealed that NCE were integral to explaining lynx-hare population dynamics in boreal forests, cascading effects of top predators in Wisconsin lakes, and cascading effects of killer whales and sea otters on kelp forests in nearshore marine habitats. The relative roles of consumption and NCE of wolves on moose and consequent indirect effects on plant communities of Isle Royale depended on climate oscillations. Nonconsumptive effects have not been explicitly tested to explain the link between planktonic alewives and the size structure of the zooplankton, nor have they been invoked to attribute keystone predator status in intertidal communities or elsewhere. We argue that both consumption and intimidation contribute to the total effects of keystone predators, and that characteristics of keystone consumers may differ from those of predators having predominantly NCE. Nonconsumptive effects are often considered as an afterthought to explain observations inconsistent with consumption-based theory. Consequently, NCE with the same sign as consumptive effects may be overlooked, even though they can affect the magnitude, rate, or scale of a prey response to predation and can have important management or conservation implications. Nonconsumptive effects may underlie other classic paradigms in ecology, such as delayed density dependence and predator-mediated prey coexistence. Revisiting classic studies enriches our understanding of predator-prey dynamics and provides compelling rationale for ramping up efforts to consider how NCE affect traditional predator-prey models based on consumption, and to compare the relative magnitude of consumptive and NCE of predators.     

Conflict-involvement of male guinea pigs (<Emphasis Type="Italic">Cavia aperea</Emphasis> f. <Emphasis Type="Italic">porcellus</Emphasis>) as a criterion for partner preference

Polygynous mating systems can inflict considerable costs on males, often causing the emergence of alternative mating strategies to ensure reproductive success. These strategies can lead to different morphs of color, size, or behavior. The present work was done on guinea pigs, a polygynous rodent species. Some males can show a reduced readiness for conflict, perhaps employing an alternative mating strategy. To test this hypothesis, a two-stage experiment was set up, with males (N = 16) and females (N = 16) initially living in isosexual groups. Visual and olfactory contact was possible through a wire mesh. Male agonistic behavior was observed for 15 days, confirming the existence of less-conflict-involved (LCI, N = 7) and more-conflict-involved males (MCI, N = 9). Significant differences were found for a conditional parameter, body mass, and a morphometric one, testis width: LCI consistently surpassed MCI. Hormonally, cortisol was comparable, while testosterone was distinctly higher in MCI. Next, males and females were joined and observed for further 24 days. Males initially lost weight but reached original mass towards the end of the experiment. Testis width patterns were similar. Again, LCI had higher body mass. Cortisol was comparable, but testosterone release 3 days after merging was significantly higher in LCI. Behaviorally, LCI exhibited significantly less male–male aggression and more socio-sexual behavior than MCI. The former were more successful, with 57% capable of accessing females, in contrast to 11% of MCI. The existence of two distinct behavioral phenotypes in guinea pig males suggests that different reproductive strategies may exist in this species.