Acquisition of spatial knowledge for routes

An important issue in the study of spatial knowledge has been the distinction between configurational and route knowledge. Route knowledge is characterized by the knowledge of sequential locations without the knowledge of general interrelationships. In contrast, configurational knowledge is characterized by the ability to generalize beyond learned routes and locate objects within a general frame of reference. These two types of knowledge are contrasted in a learning experiment, in which subjects acquire spatial information either from a map or a slide presentation. Furthermore, the structure of their spatial knowledge is derived from free-recall data using the ordered tree clustering algorithm. The results show, first, that subjects in the map condition acquired more accurate configurational knowledge. Second, we found that route knowledge can be acquired either through route presentation or map presentation. Third, there are individual differences within the slide group, such that some subjects were able to acquire configurational knowledge. And fourth, ordered trees are able to account for some of these differences, and thus identify the degree of configurational knowledge acquired by the slide subjects.     

ALTERNATIVES FOR GROUND WATER LAW CHANGE IN ARIZONA1

ABSTRACT: Western state water resources are drawing increasing attention because of prolonged drought, pound-water overdraft and an ever-increasing awareness of insufficient Colorado River water to supply a growing population and meet industrial demand. Arizona is no exception, and the alarming decline in ground-water levels has prompted the Arizona State Legislature to adopt legislation establishing the Ground-Water Management Study Commission to recommend legislative action by 1979. This paper summarizes Arizona's ground water legislative history and discusses possible alternatives for change. The authors address specific issues facing the State and offer a set of possible Commission recommendations.     

Spatial differences in outdoor PM10 mass and aerosol composition in Mexico City

Twenty-five MiniVol samplers were operated throughout the Mexico City metropolitan region from February 22 through March 22, 1997, to evaluate the variability of PM10 concentrations and composition. The highest PM10 concentrations were found in neighborhoods with unpaved or dirty roads, and elements related to crustal material were the main cause of differences from nearby (<200 m) monitors that were not adjacent to the roadbed. SO4(2-) concentrations were homogeneous across the city. SO4(2-) measured at the city boundaries was about two-thirds of the concentrations measured within the urbanized area, indicating that most SO4(2-) is of regional origin. Elemental carbon (EC) and organic carbon (OC) concentrations were highly variable, with higher concentrations in areas that had high diesel traffic and older vehicles. Spatial correlations among PM10 concentrations were high, even though absolute concentrations were variable, indicating a common effect of meteorology on the concentration or dispersion of local emissions.     

The impact of ozone on a salt marsh cordgrass (Spartina alterniflora)

Spartina alterniflora plants were collected from salt marshes within New Jersey, South Carolina, and Georgia USA and shipped to The Pennsylvania State University. New plants were grown from rhizomes in six open-top field chambers. Three chambers received charcoal-filtered air, and three received charcoal-filtered air plus 80 ppb ozone, 8 h/day for 65 days. Flower, leaf, and shoot number per plant were recorded weekly. Photosynthetic rates were measured in week 5, and foliar injury was assessed during week 9. Final dry weight of roots, shoots, and rhizomes were determined. While ozone-treated plants from all states expressed symptoms of ozone injury, plants from South Carolina exhibited no effect of ozone on any other measured variable. Plants from the Georgia site showed ozone-induced reductions in all measured variables except leaf dry weight. Ozone-treated plants from New Jersey showed reductions in photosynthetic rate, leaf and shoot number, and root dry weights. Only plants from New Jersey produced flowers, with ozone treatment causing delay in flowering and reduction in the number of flower spikes produced.     

Environmental risk: Management strategies in the developing world

This paper describes a heuristic model which helps to relate a developing nation's environmental risk to the level of sophistication appropriate in adjusting management strategy to dealing with environmental hazards. The model takes into account three factors: the degree of risk, the stage of economic growth, and the sophistication of adjustment. The interrelationship of these factors is examined, and the role of international cooperation in establishing strategies is outlined.     

Trends in Water Chemistry in a Maple Forest on a Steep Slope

Year-to-year variation in SO₄ ^2-,NO₃ ^-, Ca²⁺, K⁺, and Mg²⁺concentrations in forest floor and mineral soil percolatefrom a forested, podzolic soil at the Turkey Lakes Watershedon the Precambrian Shield was assessed for monotonic trendsbetween 1986 and 1995. Our objective was to examine howrapidly ion concentrations in soil percolate equilibratedafter stabilization of SO₄ ^2- concentrations inprecipitation. Significant negative trends were detected inmonthly Ca²⁺, and Mg²⁺ concentrations in forestfloor and SO₄ ^2-, Ca²⁺, and Mg²⁺ inmineral soil percolate during the 10-year-period. Thedecline in Ca²⁺ and Mg²⁺ was greater than annualdecreases in SO₄ ^2- and NO₃ ^- in forestfloor percolate and proportional to the reduction inSO₄ ^2- in mineral soil percolate. Response ofmineral soil percolate to a 15 mol_c L^-1SO₄ ^2- decrease in wet-only precipitation between1985 and 1986 was a gradual decline in SO₄ ^2-concentration through 1995. The five-year meanSO₄ ^2- concentration in bulk precipitation, forestfloor percolate, and mineral soil percolate decreased 8, 9and 18 mol_c L^-1 from 1986–90 to 1991–95.Microbial (mineralization of organic S) and sorption(release from and/or retention in the pool of insolubleSO₄ ^2-) processes in the soil were logicalexplanations for the observed changes in SO₄ ^2- inmineral soil percolate.     

SYSTEMS FOR RAINFALL AND RUNOFF USE,TUCSON, ARIZONA1

Rainfall and runoff in the Tucson, Arizona, urban area can be used to augment residential and municipal water supplies. Residential rainfall-harvesting systems include a catchment surface, collection and concentration components, separation and treatment units, storage capacity and distribution capability. A system to control runoff can divert water from urban washes for use in parks or other landscaped areas or can be used to enhance recharge to groundwater reservoirs. A reduction in flood hazards or peaks is a concurrent benefit of controlling and diverting runoff.