Modeling leaf dispersal in mixed hardwood forests using a ballistic approach

In mixed-species stands, modeling leaf litter dispersal is important to predict the physical and chemical characteristics of the forest floor, which plays a major role in nutrient cycling and in plant population dynamics. In this study, a spatially explicit model of leaf litterfall was developed and compared with two other models. These three models were calibrated for a mixed forest of oak and beech using litterfall data from mapped forest plots. All models assumed that an allometric equation described individual leaf litter production, but they strongly differed in the modeling of the probability density of leaf shedding with distance from source trees. Two models used a negative exponential function to account for leaf dispersal with distance, and this function was allowed to vary according to wind direction in one of them. In contrast, our approach was based on a simple ballistic equation considering release height, wind speed, wind direction, and leaf fall velocity; the distributions of wind speeds and wind directions were modeled according to a Weibull and a Von Mises distribution, respectively. Using an independent validation data set, all three models provided predictions well correlated to measurements (r > 0.83); however, the two models with a direction-dependent component were slightly more accurate. In addition, parameter estimates of the ballistic model were in close agreement with a foliar litter production equation derived from the literature for beech and with wind characteristics measured during leaf litterfall for both species. Because of its mechanistic background, such a spatially explicit model might be incorporated as a litterfall module in larger models (nutrient cycling, plant population dynamics) or used to determine the manner in which patch size in mixed-species stands influences litter mixture.     

Vapor intrusion mitigation challenges posed by a classic urban setting

AECOM's Environmental Remediation Services Group, under a Pennsylvania Department of Environmental Protection (PADEP) remediation contract, was tasked with assessing potential vapor intrusion risks and mitigating identified risks at an active commercial property affected by a former adjacent laundry and dry cleaning operation. The former dry cleaning operation was positioned in the center of row‐buildings containing various commercial businesses. The neighboring active commercial property is an antiquated building that operates as a coffee shop. The coffee shop building contains a service area, a kitchen, and a rear conference room on the first floor, a storage area on the second floor, and a partial basement. The basement has been observed to periodically flood. Adjacent to the coffee shop building is an operating hair and nail salon that formerly functioned as one of the dry cleaning operations buildings with known soil, groundwater, and soil gas impacts. Due to the disposition of the coffee shop building, a methodical approach was implemented to characterize the potential vapor intrusion risk and included a diagnostic building inspection that identified required management of basement apertures and abatement of periodic flooding prior to vapor intrusion mitigation system design and installation.     

A three-dimensional experimental investigation of the structure of the spanwise vortex generated by a shallow vortex dipole

The three-dimensional dynamics of shallow vortex dipoles is investigated by means of an innovative three-dimensional, three-component (3D-3C) scanning PIV technique. In particular, the three-dimensional structure of a frontal spanwise vortex is characterized. The technique allows the computation of the three-dimensional pressure field and the planar (x, y) distribution of the wall shear stress, which are not available using standard 2D PIV measurements. The influence of such a complex vortex structure on mass transport is discussed in the context of the available pressure and wall shear stress fields.     

EXPERIMENTS IN IMPROVING RURAL WATER SUPPLIES1

ABSTRACT: A series of studies and experiments were conducted to identify rural water supply quality problems and to develop and demonstrate solutions. We found that rural people had severe and widespread problems, while state agencies held potential answers. Communications between experts and town officials were weak or absent. To bridge this gap, an information system was devised and tested. A computer program was developed to provide a printout map of the state, showing town boundaries and the quality of water supplies for each public water system monitored by the State Health Department. The map and data were published in local newspapers with an explanation of the map and its symbols. Town health officers were interviewed to determine the results of the public disclosure. We found that the news releases led to increased awareness, interest, and understanding of water quality and demands for ameliorative action. This program was supplemented by two publications: “A Layman's Guide to Eutrophication” and “A Handbook for Rural Water Uses.” The handbook explains the nature of drinking water standards, the reasons for these standards, the dangers and results of not meeting the standards, and cost-effective alternatives for improving water quality.     

The Energy Efficiency 2000 Project and energy-efficiency demonstration zones in Eastern and Central Europe

Energy economy and efficiency are the two most common energy priorities of EC member states. Increasing energy efficiency is also a way of making EC technical assistance to Central and Eastern Europe more effective. The Energy Efficiency 2000 project, and in particular the establishment of energy-efficiency demonstration zones, are key features in this process.     

PLANNING UNDEVELOPED LAKESHORE1

ABSTRACT: Private lakeshore development usually precedes establishment of public lake access. As a result, the best access areas are often occupied before public access is provided. The public then has a problem to provide access for nonriparian citizens. This problem can be anticipated and prevented by classifying undeveloped lakeshore areas according to suitability for both private and public uses, and incorporating appropriate recommendations into the municipal, comprehensive land use plan. To accomplish this, a site evaluation system has been developed which numerically rates the lakeshore for each of four public uses: public beaches, picnic areas, boat access areas, and public marinas; and two private uses: private marinas and vacation homes. Ratings are developed for: slope, soil suitability, shoreland type, water quality, site location, scenery, and road access. These ratings are combined with a statement of public goals developed from attitude surveys to produce a lakeshore land use plan. The plan recommends that lakeshore areas best suited for private development are so used, and areas best suited for public use are reserved for that purpose. This site evaluation system is demonstrated by a case study on Lake Champlain in Ferrisburg, Vermont.     

Microbial bioavailability of pyrene in three laboratory-contaminated soils under aerobic and anaerobic conditions

Changes in bioavailability of pyrene in three uncontaminated soils were examined under aerobic and anaerobic conditions. Three soils were aerobically aged with pyrene and [(14)C]pyrene for 63 days, then incubated with water, nitrate, or sulfate under aerobic or anaerobic conditions for one year. Under aerobic conditions, microorganisms in two soils mineralized 58-82% of the added [(14)C]pyrene. The two soils amended with nitrate were seen to have enhanced aerobic mineralization rates. In one of these soils, non-extractable pyrene was seen to decrease over the course of the study due to desorption and mineralization, nitrate amendment enhanced this effect. Under anaerobic conditions, generated with a N(2):CO(2)(g) headspace, two soils with nitrate or sulfate amendment showed an increase in extractable [(14)C]pyrene at 365 days relative to inhibited controls, presumably due to microbially mediated oxidation-reduction potential and pH alteration of the soil environment. These observations in different soils incubated under aerobic and anaerobic conditions have important implications relative to the impact of microbial electron acceptors on bioavailability and transport of non-polar organic compounds in the environment suggesting that, given enough time, under the appropriate environmental conditions, non-extractable material becomes bioavailable. This information should be considered when assessing site specific exposure risks at PAH contaminated locations.