Heavy metals in an urban watershed in southeastern Michigan

The occurrence of heavy metals in the soil was measured over a period of several years to determine background concentrations in a heavily urbanized watershed in southeastern Michigan. A spatially dispersed sample was collected to capture the inherent variability of the soils and historic land use. The analysis focused on 14 metals (antimony, arsenic, barium, beryllium, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, thallium, and zinc) that are part of the USEPA's list of the 129 most common pollutants. Metal concentrations were measured at three depths: near-surface (<0.5 m), shallow subsurface (0.5-10 m), and depths greater than 10 m across six soil units in glacial terrain. Additional analyses assessed the metal concentrations in each depth profile across three general land use categories: residential, commercial, and industrial. Metal concentrations were the highest in the near-surface with Pb present at concentrations averaging 15.5 times that of background in industrial areas and approximately 16 times background in residential areas. Cadmium, Hg, and Zn were also present in surface soils at levels of several times that of background. The highest concentrations of each of these metals were present in the clay-rich soils located in the eastern, more urbanized and industrialized part of the watershed. Metals detected at elevated concentrations decreased in concentration with increasing depth and distance from the urbanized and industrialized center of the watershed. Statistically significant differences in the concentrations of heavy metals were also noted between the land use categories, with Cd, Cr, Cu, Pb, Ni, and Zn observed within industrial areas at mean concentrations several times greater than background levels.     

The United Nations' humanitarian pillar: refocusing the UN's disaster and emergency roles and responsibilities

Changes in the nature of humanitarian crises and in the ways that the international community responds to such crises demand a radically overhauled role for the United Nations system. At a time when the UN and its member states are pursuing reform of some of that institution's most fundamental peace and security functions, this paper suggests that reform, too, is required to meet humanitarian crises of the future. This paper proposes a new type of operational role for the UN, while at the same time arguing that the UN has to place itself in the vanguard of humanitarian assistance as "the standard-bearer". The article draws many of its conclusions and recommendations from a recently completed study, requested by the Inter-Agency Standing Committee, concerning the effect for the UN system of changes in humanitarian financing.     

The field performance of frontal air bags: a review of the literature

This article presents a broad review of the literature on frontal air bag field performance, starting with the initial government and industry projections of effectiveness and concluding with the most recent assessments of depowered systems. This review includes as many relevant metrics as practicable, interprets the findings, and provides references so the interested reader can further evaluate the limitations, confounders, and utility of each metric. The evaluations presented here range from the very specific (individual case studies) to the general (statistical analyses of large databases). The metrics used to evaluate air bag performance include fatality reduction or increase; serious, moderate, and minor injury reduction or increase; harm reduction or increase; and cost analyses, including insurance costs and the cost of life years saved for various air bag systems and design philosophies. The review begins with the benefits of air bags. Fatality and injury reductions attributable to the air bag are presented. Next, the negative consequences of air bag deployment are described. Injuries to adults and children and the current trends in air bag injury rates are discussed, as are the few documented instances of inadvertent deployments or non-deployment in severe crashes. In the third section, an attempt is made to quantify the influence of the many confounding factors that affect air bag performance. The negative and positive characteristics of air bags are then put into perspective within the context of societal costs and benefits. Finally, some special topics, including risk homeostasis and the performance of face bags, are discussed.     

Water transport in polylactic acid (PLA), PLA/ polycaprolactone copolymers, and PLA/polyethylene glycol blends

Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester, and water vapor permeability may have a significant influence on the rate of degradation. A method is devised to use bags prepared from PLA films and filled with molecular sieves to determine the water vapor permeability in the polymer, its copolymers with caprolactone, and blends with polyethylene glycol. The “solution-diffusion” model is used to determine the permeability parameters. These include the solubility coefficient,S, a measure of the equilibrium water concentration available for hydrolysis and the diffusion coefficient,D, which characterizes the rate of water vapor diffusion into the film under specific conditions. Values ofS andD at 50‡C and 90% relative humidity ranged from 400 × 10^-6 to 1000 × 10^-6 cm³ (STP)/(cm³ Pa) and 0.20 × 10^-6 to 1.0 × 10^-6 cm²/s, respectively. TheS andD coefficients were also measured at 20 and 40‡C and compared to those of other polymers. The degree of crystallinity was found to have little influence on the measured permeability parameters. The heat of sorption, δH_S, and the activation energy of diffusion, E_D, were used to show that the permeability process is best described by the “water cluster” model for hydrophobic polymers. Finally, the diffusion coefficient is used to compare the rate of water diffusion to the rate of water consumption by ester hydrolysis. Results indicate that hydrolytic degradation of PLA is reaction-controlled.     

TARGETING NONPOINT SOURCE POLLUTION CONTROL: PHOSPHORUS IN THE MINNESOTA RIVER BASIN1

ABSTRACT: The state of Minnesota seeks to reduce phosphorus loading to the Minnesota River by 40 percent from current levels. Looking at one major watershed in the river basin, we examined the cost effectiveness of targeting versus not targeting specific practices or regions within a watershed for controlling nonpoint phosphorus pollution from agriculture. Integrating biophysical simulation results from current and alternative farming systems with production cost and return estimates enabled us to analyze this policy. Our results indicated it is more cost effective to reduce nonpoint pollution by targeting particular regions or practices in a watershed compared to not targeting. Specifically, producers farming on cropland susceptible to erosion in close proximity to water will appreciably reduce phosphorus nonpoint pollution loading potential by switching from conventional tillage to conservation tillage and by reducing phosphorus fertilization levels to those recommended by the state extension service. Efforts to target those producers in the Minnesota River Basin could reduce potential transaction costs and compensation from “takings” by approximately $50 million (74 percent) over not targeting.     

Surface and subsurface geologic risk factors to ground water affecting brownfield redevelopment potential

A model is created for assessing the redevelopment potential of brownfields. The model is derived from a space and time conceptual framework that identifies and measures the surface and subsurface risk factors present at brownfield sites. The model then combines these factors with a contamination extent multiplier at each site to create an index of redevelopment potential. Results from the application of the model within an urbanized watershed demonstrate clear differences between the redevelopment potential present within five different near-surface geologic units, with those units containing clay being less vulnerable to subsurface contamination. With and without the extent multiplier, the total risk present at the brownfield sites within all the geologic units is also strongly correlated to the actual costs of remediation. Thus, computing the total surface and subsurface risk within a watershed can help guide the remediation efforts at broad geographic scales, and prioritize the locations for redevelopment.     

Hunting and the Likelihood of Extinction of Amazonian Mammals

Species inhabiting tropical forests are thought to be on the verge of mass extinction. Much work has focused on extinction rates caused by deforestation; however, many of the recorded extinctions that have occurred since 1600 were a result of overhunting. We collected data on the relative abundance of large-bodied mammals in the northeastern Peruvian Amazon in areas with persistent hunting pressure and in areas with infrequent hunting pressure. We quantified the effects of hunting by calculating the change in abundance of species between the infrequently and persistently hunted sites. We report that in Amazonian mammals weighing more than 1 kg the degree of population declines caused by hunting is correlated with the species' intrinsic rate of natural increase (r_max  ), longevity, and generation time. Our results show that species with long-lived individuals, low rates of increase, and long generation times are more vulnerable to extinction than species with short-lived individuals, high rates of increase, and shorter generations.     

Peak Runoff Model Comparison on Central Illinois Watersheds1

ABSTRACT: Four peak runoff rate models were tested with 183 gage years of record to determine the model most applicable to small watersheds of mild topography in east-central Illinois. The Cypress Creek, Rational, Chow, and SCS peak runoff models were evaluated for their performance. Statistical analyses indicated the Soil Conservation Service model was most appropriate for the watersheds tested.     

Birth sex ratios in sheep over nine lambing seasons: years 7–9 and the effects of ageing

The birth sex ratio of a commercial flock of Suffolk cross sheep, Ovis aries, was studied over nine consecutive lambing seasons. In all data from 2704 lambs were recorded and analysed. The overall (1985–1993) birth sex ratio was 49.96% male lambs. Ewes with single lambs produced significantly more males (53.04%) than ewes with triplets (45.54% male). A significant positive correlation was found between the flock age and the birth sex ratio (1985–1992). As the flock aged the birth sex ratio changed from female biased to male biased, remained male biased for a number of years, and then became female biased again. This pattern is evident first in single, then in twin and later in triplet births. Among like sex twins (males and females) (1985–1993) more males (53.88%) were born in the first half and more females (45.57% males) in the second half of the lambing season. The difference between the two halves is significant.