Seasonal and Long‐Term Variations in Hydraulic Head in a Karstic Aquifer: Roswell Artesian Basin,New Mexico1

Abstract: Water levels in the karstic San Andres limestone aquifer of the Roswell Artesian Basin, New Mexico, display significant variations on a variety of time scales. Large seasonal fluctuations in hydraulic head are directly related to the irrigation cycle in the Artesian Basin, lower in summer months and higher in winter when less irrigation occurs. Longer‐term variations are the result of both human and climatic factors. Since the inception of irrigated farming more than a century ago, over‐appropriation of water resources has caused water levels in the artesian aquifer to fall by as much as 70 m. The general decline in hydraulic head began to reverse in the mid‐1980s due to a variety of conservation measures, combined with a period of elevated rainfall toward the end of the 20th Century.     

Determination and implementation of optimal air quality standards

This paper utilizes two least-cost emission control strategies and develops rules for structuring and implementing optimal air quality standards. A strategy typical of those currently enforced, based on the State Implementation Plans (SIP's ), is compared to two least-cost strategies: (i) ambient least cost (ALC ), which achieves required air quality at least cost; and (ii) emissions least cost (ELC ), which achieves required emissions reduction at least cost. A demonstration is given of the theoretically derived result that the ALC strategy should be utilized in cost-benefit analyses to determine air quality standards and to generate emissions taxes. Preliminary analysis of the St. Louis area indicated tentative justification for a particulate ambient standard at least as strict as the current Federal primary standard. The efficiency, equity, and administrative costs for implementation of strategies based on the least-cost concept are also examined.     

Parental supervision of teenage drivers in a graduated licensing system

OBJECTIVES: Most states now have lengthy learner periods for young, beginning drivers as part of their graduated driver licensing (GDL) systems. Although parents play a vital role during the learner stage of GDL by supervising driving practice, virtually nothing is known about the nature and quality of parental supervision. The objectives of this study were to investigate parents' supervisory behavior and parent-teen relationships during the learner stage of graduated licensing and to evaluate two approaches for assisting parents in supervising their teenager's early driving experience. METHODS: Families of teenagers applying for a learner permit received either a booklet describing highly structured practice sessions for beginning drivers, a series of "tip sheets" offering more generalized guidance, or no special materials. Questionnaires were sent separately to parents and teenagers three to six months after teenagers obtained their permit. RESULTS: Of 1,190 participating families, 653 parents (55%) and 609 teenagers (51%) responded. Both parents and teenagers perceived parents as supportive and helpful during driving sessions. Parents often demonstrated positive behaviors, such as complimenting their teenager and pointing out possible hazards; they also exhibited less desirable behaviors, such as raising their voice, but these were less frequent. A majority of parents (71%) and teenagers (52%) reported that they enjoyed spending this time together. About four months after obtaining a permit, most parents believed their teenager did not yet have enough experience and was not ready to drive unsupervised. Although the reported behaviors are encouraging, within-family agreement was low on most items. Finally, efforts to assist parents proved unsuccessful. Although parents thought the booklet and tip sheets were helpful, most used these materials only in a general way. CONCLUSIONS: The extended learning experience required by GDL programs is a positive experience for many families. However, finding a method for helping parents achieve maximum benefits during this process will be challenging. The results also suggest that current requirements in the learner phase of most state GDL systems (six months; 30-50 hours) may be inadequate to ensure that teenagers obtain a sufficient amount of experience to begin driving safely on their own.     

A novel method for reducing acid mine drainage using green liquor dregs

When exposed to the weather, sulfidic minerals release sulfuric acid, metals and metalloids. This leachate can devastate nearby ecosystems for centuries. This article reports a novel barrier system based on green liquor dregs that reduces acid generation, is inexpensive, and is practical for implementation at operational mines. Two waste rock piles were constructed. One pile was left open to the atmosphere, and the other was sealed with green liquor dregs and partially capped with a polyethylene liner. This test was designed in collaboration with personnel from Boliden Mineral AB, a Swedish mining company in order to ensure that the results would be practical to implement at an operational mine. Leachate flow and chemistry were monitored in both piles over a period of 12 months. Effluent volume was 40 % lower in the test pile, while thirteen of the twenty elements assessed showed average concentrations that were 50 % lower in the test pile than in the control pile. For the most environmentally toxic elements As, Cd, Pb and Hg, reductions were even more significant, ranging between 67 and 87 %. These positive results are hypothesized to be primarily due to the chemical and physical characteristics of the green liquor dregs. The novelty of this result is that it is the first barrier system that fulfills the multiple needs of the Swedish mining industry: It is effective in reducing acid mine drainage while remaining both economical and practical. No other barrier system meets these requirements.     

Denitrification in suburban lawn soils

There is great uncertainty about the fate of nitrogen (N) added to urban and suburban lawns. We used direct flux and in situ chamber methods to measure N and NO fluxes from lawns instrumented with soil O sensors. We hypothesized that soil O, moisture, and available NO were the most important controls on denitrification and that N and NO fluxes would be high following fertilizer addition and precipitation events. While our results support these hypotheses, the thresholds of soil O, moisture, and NO availability required to see significant N fluxes were greater than expected. Denitrification rates were high in saturated, fertilized soils, but low under all other conditions. Annual denitrification was calculated to be 14.0 ± 3.6 kg N ha yr, with 5% of the growing season accounting for >80% of the annual activity. Denitrification is thus an important means of removing reactive N in residential landscapes, but varies markedly in space, time, and with factors that affect soil saturation (texture, structure, compaction) and NO availability (fertilization). Rates of in situ NO flux were low; however, when recently fertilized soils saturated with water were incubated in the laboratory, we saw extraordinarily high rates of NO production for the first few hours of incubation, followed by rapid NO consumption later in the experiment. These findings indicate a lag time between accelerated NO production and counterbalancing increases in NO consumption; thus, we cannot yet conclude that lawns are an insignificant source of NO in our study area.     

Responsible Care© Programs for Hazardous Chemicals

This article describes the development, use, and learnings of a comprehensive Responsible Care^® program as applied to the management of hazardous substances at various stages during the life cycle of the product. The article offers specific examples for stewardship programs in the biocide industry, and discusses the role of the medical community. © 2001 John Wiley & Sons, Inc.     

A Kinetic Study of Aerobic Propane Uptake and Cometabolic Degradation of Chloroform, cis-Dichloroethylene and Trichloroetylene in Microcosms with Groundwater/Aquifer Solids

The focus of this study was to compare the behavior of different consortiums of aerobic propane-utilizing microorganisms, with respect to both the lag time for growth after exposure to propane, and their ability to transform three chlorinated aliphatic hydrocarbons (CAHs): chloroform (CF), cis-dichloroethylene (c-DCE) and trichloroethylene (TCE). Thirty-three slurry microcosms, representing seven combinations of aquifer solids and groundwater were constructed for this study. The lag time required for establishing propane-utilizing consortiums ranged between 24 and 29 days in 6 of the 7 combinations. Kinetic tests were performed with respect to propane utilization and CAH transformation. After CAH exposure, the ability of the microorganisms to metabolize propane was significantly reduced. CF and TCE were transformed more slowly than c-DCE, the average values of the initial transformation rates being equal to 0.10 ± 0.04, 0.09 ± 0.05 and 0.98 ± 0.18 mol/(L h),respectively. CF caused the greatest reduction in propane uptake rates, whereas c-DCE exhibited an apparently reversible negative effect on propane uptake rates. The estimates of the Monod half-saturation constants relative to CF, TCE and c-DCE resulted in the 2–3 mol/L range, but were characterized by a high degree of uncertainty.     

Effect of cigarette smoking on residential NO2 levels

Two studies evaluating the levels and sources of nitrogen dioxide in approximately 90 employee homes in the Richmond area with continuous sampling during the weeks of August 5, 1980, and February 9, 1981, were performed using samplers in the living room, bedroom, kitchen, and outdoors. Additional data were collected concerning appliance usage, heating/cooling plant, ventilation and cigarette smoking. Results were analyzed using BMDP routines. The largest contributor to NO₂ concentration was found to be gas-fired kitchen appliances. The mean kitchen level for homes with gas appliances during the winter study was 188 μg/m³. Excluding participants with gas kitchens, incremental influence due to cigarette smoking was detected. The 7-day, 3-room average level of NO₂ in the homes of nonsmokers and smokers without gas-fired appliances was 12 and 15 μg/m³, respectively, in the summer. The corresponding winter values were 19 and 22 μg/m³. Furthermore, the individual levels of NO₂ in the homes of smokers were generally below both the adjacent outdoor level and the National Ambient Air Quality Standard limit for annual exposure.