Reproducibility of the HI-VOL Sampling Method Under Field Conditions

Pairs of standard NASN Hi-Vol suspended particulate samplers were operated biweekly at 25 stations (22 urban, 3 nonurban) from August to December 1969 to determine the comparability of paired samples collected under field conditions. The average of each pair of concentration values is taken as the best estimate of the true value; half the difference between each pair of sample values represents the deviation of the pair from that true value. A cumulative distribution of the individual percent deviations from the corresponding true values shows that half the measurements differ from their true value by less than ±4.5%. 90% of the measurements differ from the true value by less than ± 14%.     

Improved Ventilation of Open Top Greenhouses

Plant injury caused by air pollutants is a well recognized effect causing economic losses totalling millions of dollars. Farm crops, forest species, and ornamentals are all affected depending upon kind of plant and degree of exposure. Benedict¹ estimated the minimum annual agricultural losses in the U. S. to be $132 million in 1969-1971. Millecan² estimated California crop losses caused by air pollutants to be at least $25 million in 1972. Recent studies by Brewer³ in which conventional greenhouses were placed in the field over cotton gave results showing yields were reduced by 10-30% in the San Joaquin valley where significant levels of photochemical smog occur. However, these estimates of losses represent little more than educated guesses because the procedures available for obtaining the information are so imprecise.     

Modification of an Ambient Air Quality Model for Assessment of U. S. Naval Aviation Emittants

Previous studies have indicated that the EPA-HIWAY model significantly overestimates the pollutant concentrations for stable atmospheric conditions, especially under parallel wind-road orientation angles with low wind speed. This overestimation is due to the fact that the model's dispersion parameters do not properly account for the traffic-induced turbulence near roadways. In this paper, the Pasquill- Gifford dispersion curves used by the model are modified based on the recent studies that have quantified the nature of the trafficinduced turbulence and its influence on the pollutant dispersion in the near-field. The results show that the model performance is significantly improved when these new dispersion curves in conjunction with an aerodynamic drag factor, which in a rough way accounts for the change in the mean wind field due to the moving vehicles, are used in the HIWAY model.     

The Oxidation of Hydrocarbons on Simple Oxide Catalysts

A simple practical scheme for prediction and control of short duration air pollution maxima from a single source is demonstrated for a particular source-site geometry. The method makes use of a number of traditional semi-empirical atmospheric turbulence and diffusion relations in a different application. The concepts stressed in the current example are: (1) the incorporation of interactions of high frequency turbulence and low frequency meandering of the wind into a concentration forecast and (2) the use of source-site geometry to simplify the practical problem as much as possible.     

What Happens to Environmental Philosophy in a Wicked World?

What is the significance of the wicked problems framework for environmental philosophy? In response to wicked problems, environmental scientists are starting to welcome the participation of social scientists, humanists, and the creative arts. We argue that the need for interdisciplinary approaches to wicked problems opens up a number of tasks that environmental philosophers have every right to undertake. The first task is for philosophers to explore new and promising ways of initiating philosophical research through conducting collaborative learning processes on environmental issues. The second task is for philosophers to recognize the value of philosophical skills in their engagements with members of other disciplines and walks of life in addressing wicked problems. The wicked problems framework should be seen as an important guide for facilitating philosophical research that is of relevance to problems like climate change and sustainable agriculture.     

Potential environmental influence of amino acids on the behavior of ZnO nanoparticles

The fate of nanomaterials when they enter the environment is an issue of increasing concern and thus it is important to know how they interact with natural organic molecules since this may have a significant impact on the particles' behavior. Because of our poor knowledge in this regard, the interaction of ZnO nanoparticles with amino acids of contrasting surface charge, including Histidine (HIS), Glycine (GLY), Aspartic acid (ASP) and Glutamic acid (GLU) which occur commonly in natural habitats, such as the plant root zone, was investigated over a range of pH conditions and concentrations. The addition of the individual amino acid led to significant changes in nanoparticle colloidal zeta potential stability, particle size distribution and the extent of agglomeration. Variations in pH resulted in considerable changes in nanoparticle surface charge and hydrodynamic size. In general, the particle size distribution decreased as the amino acid concentration increased, with more acidic conditions exacerbating this effect. In addition, increased concentrations of amino acids resulted in more stable nanoparticles in aqueous suspensions. Histidine had the greatest effect on colloidal stability, followed by Glycine, Aspartic acid and finally Glutamic acid. This study illustrates how nanoparticle behavior may change in the presence of naturally occurring amino acids, an important consideration when assessing the fate of nanoparticles in the environment. Additionally, utilization of amino acids in industrial processes could reduce particle agglomeration and it could lead to a way of employing more sustainable reagents.     

Regulating overabundant ungulate populations: an example for elk in Rocky Mountain National Park, Colorado

In many areas of the world, populations of native ungulates have become so abundant that they are believed to be harming vegetation and disrupting ecosystem function. Methods for controlling overabundance populations include culling animals from the population and controlling fertility using contraceptives. However, understanding the feasibility these alternatives requires insight into their long-term effects on populations. We constructed a simulation model to evaluate options for regulating elk populations in and around Rocky Mountain National Park and used the model to compare different treatment options. Methods were evaulated with respect to the time required to reduce the population to a target level, the number of animals treated and/or culled and the risk of extinction. We contrasted culling with lifetime-effect contraceptives and yearlong contraceptives. Lifetime contraceptives required treating the fewest animals to maintain the population at desired targets. However, this approach also causes the greatest population variability and potential risk of extinction. Yearlong contraceptives required treatment of dramatically more animals but had essentially no extinction risk whereas culling produced intermediate levels of both extinction risk and number of animals treated. These results characterize the risks and benefits of alternative control strategies for overabundant wildlife. They emerge from a modeling approach that can be broadly useful in helping managers in choose between alternatives for regulating overabundant wildlife.     

Watershed protection: Capturing the benefits of nature's water supply services

Healthy watersheds provide valuable services to society, including the supply and purification of fresh water. Because these natural ecosystem services lie outside the traditional domain of commercial markets, they are undervalued and underprotected. With population and development pressures leading to the rapid modification of watershed lands, valuable hydrological services are being lost, which poses risks to the quality and cost of drinking water and the reliability of water supplies. Increasing the scale and scope of programmes to protect hydrological services requires policies that harmonize land uses in watersheds with the provision of these important natural services. This article summarizes key attributes of hydrological services and their economic benefits; presents a spectrum of institutional mechanisms for safeguarding those services; discusses programmes in Quito (Ecuador), Costa Rica and New York City; and offers some lessons learned and recommendations for achieving higher levels of watershed protection.     

Direct observations of feeding structures and mechanisms in bivalve molluscs using endoscopic examination and video image analysis

A new technique is described for observing the structures and mechanisms of suspension feeding in bivalves using endoscopic examination and video image analysis. This method permits direct in vivo observations of whole, intact structures of relatively undisturbed specimens. No surgical alterations of shell or tissue are required for most species. Pallial organ activity can be recorded for future observations and analysis. Using this technique we examined three bivalve species, each with different degrees of mantle fusion:Mya arenaria L.Mytilus edulis L., andPlacopecten magellanicus (Gmelin). The specimens were collected between April and September 1990 at various locations in Trinity Bay, Newfoundland, Canada. Particle retention by the gill and transport of material to the palps was observed, and velocity of particles moving on the gill was determined. We demonstrate that the endoscope-video-analysis system is an efficient and affordable technique suitable for studies of pallial organ function and mechanisms of feeding.