URBAN SERVICE PRICING AND LAND USE: SOME PRELIMINARY RESULTS1

ABSTRACT The use of public policy variables to control urban land use has been suggested or implied by a number of authors. This paper presents a conceptual foundation for doing so and the results of some empirical analyses based on this conceptual foundation. The method developed appears to constitute an alternative to more expensive approaches to the analysis of the relation between policy variables and land use. The empirical results tend to support earlier suggestions advanced by other researchers.     

Experimental test of the pupation window model for development of detritivorous insects

Cohort size and food availability to larval detritivores are linked to pupal mass, and hence to adult fitness, by the pupation window model. Previous tests of this model have employed artificial food. This paper derives a version of the model that incorporates the dynamics of natural detritus. Tests of the model using cohorts of Aedes triseriatus Say led to successful predictions of numbers of pupae, female pupal mass, and female development time. However, it is recommended that model parameters be estimated separately for different types of leaf litter.     

Fabric filters versus electrostatic precipitators

Control of particulate emissions from pulverized coal fired steam generators is becoming a significant factor in the siting and public acceptability of large coal burning power plants. The particulate emission limit established by the EPA for new coal fired boilers is 0.03 lb/10⁶ Btu (13 ng/J) Possibly more restrictive than this is the state of New Mexico's particulate regulation which calls for no more than 0.05 lb/10⁶ Btu (22 ng/J) total, and no more than 0.02 lb/10⁶ Btu (9 ng/J) less than 2 microns in diameter. This paper will evaluate the effect of these stringent limitations on the technical feasibility and economics of dry particulate removal. Electrostatic precipitators have been the dominant particulate collection device in the electric utility industry for many years because of their low capital and operating cost. However, increasingly stringent emission standards have led to substantially higher costs for precipitators. These costs have increased sufficiently for fabric filtration to become a competitive alternative in achieving cost effective control. This paper will compare the economics and performance of fabric filtration with respect to conventional electrostatic precipitators. The paper will also address the preliminary evaluation procedures that should be followed in order to select the appropriate device for new or existing coal-fired boilers.     

N-nitrosodimethylamine in drinking water using a rapid,solid-phase extraction method

A simple, rapid method for the extraction of N-nitrosodimethylamine (NDMA) from drinking and surface waters was developed using Ambersorb 572. Development of an alternative method to classical liquid-liquid extraction techniques was necessary to handle the workload presented by implementation of a provincial guideline of 9 ppt for drinking water and a regulatory level of 200 ppt for effluents. A granular adsorbent, Ambersorb 572, was used to extract the NDMA from the water in the sample bottle. The NDMA was extracted from the Ambersorb 572 with dichloromethane in the autosampler vial. Method characteristics include a precision of 4 % for replicate analyses, an accuracy of 6 % at 10 ppt and a detection limit of 1.0 ppt NDMA in water. Comparative data between the Ambersorb 572 method and liquid-liquid extraction showed excellent agreement (average difference of 12 %). With the Ambersorb 572 method, dichloromethane use has been reduced by a factor of 1,000 and productivity has been increased by a factor of 3–4. Monitoring of a drinking water supply showed rapidly changing concentrations of NDMA from day to day.     

Teaching Approaches in Geography and Students’ Environmental Attitudes

In a study which examines the pattern of geography teaching at the Advanced Level in Hong Kong and assesses the relative effectiveness of didactic and enquiry teaching approaches that are used by the teachers concerned for the development of positive values towards the environment, the question was asked as to whether or not enquiry is more effective than didactic approaches for the development of environmental values, in both the short and long terms, for students as a whole and for students from different ability ranges. Questionnaire surveys and interviews were conducted to obtain data from students after they were taught a topic on people and the environment in the curriculum, with the approach chosen by their teachers. Results show that the enquiry approach was effective with the lower to medium ability classes in the short term but students who were taught didactically performed better in more areas in the longer term. The possible causes for this pattern are discussed and suggestions for improving the effectiveness of enquiry approaches in a high-pressure, examination-oriented classroom environment are offered.     

TREE‐RING BASED RECONSTRUCTIONS OF INTERANNUAL TO DECADAL SCALE PRECIPITATION VARIABILITY FOR NORTHEASTERN UTAH SINCE 1226 A.D.1

ABSTRACT: Samples from 107 piñon pines (Pinns edulis) at four sites were used to develop a proxy record of annual (June to June) precipitation spanning the 1226 to 2001 AD interval for the Uinta Basin Watershed of northeastern Utah. The reconstruction reveals significant precipitation variability at interannual to decadal scales. Single‐year dry events before the instrumental period tended to be more severe than those after 1900. In general, decadal scale dry events were longer and more severe prior to 1900. In particular, dry events in the late 13th, 16th, and 18th Centuries surpass the magnitude and duration of droughts seen in the Uinta Basin after 1900. The last four decades of the 20th Century also represent one of the wettest periods in the reconstruction. The proxy record indicates that the instrumental record (approximately 1900 to the Present) underestimates the potential frequency and severity of severe, sustained droughts in this area, while over representing the prominence of wet episodes. In the longer record, the empirical probability of any decadal scale drought exceeding the duration of the 1954 through 1964 drought is 94 percent, while the probability for any wet event exceeding the duration of the 1965 through 1999 wet spell is only 1 percent. Hence, estimates of future water availability in the Uinta Basin and forecasts for exports to the Colorado River, based on the 1961 to 1990 and 1971 to 2000 “normal” periods, may be overly optimistic.     

Unit costs for decontamination and dismantlement of structures

A series of relationships have been developed for estimating unit costs for decontamination and dismantlement (D&D) of a number of structure types. These relationships may be applied in the absence of other data to obtain rough order-of-magnitude cost estimates for D&D activities. The relationships were developed using D&D costs estimated for various types of buildings at the U.S. Department of Energy Fernald site. These unit costs take into account the level of radiological contamination as well as the building size and type.