Mutagenic and carcinogenic potency of extracts of diesel and related environmental emissions: In vitro mutagenesis and oncogenic transformation

Extracts from emissions of four diesel engines, a gasoline engine and three related environmental samples were tested in four in vitro assay systems designed to detect carcinogenic or mutagenic activity of chemicals. Samples from three of four diesel extracts, the gasoline engine, and all three related samples were positive in an enhancement of viral transformation assay. Two diesel samples, the gasoline engine extract and extract from coke oven emissions were positive for mutation induction in Chinese hamster ovary cells. Only the gasoline engine extract and the coke oven sample were positive in a DNA fragmentation assay using alkaline sucrose gradients. Experiments using chemical transformation of Syrian hamster embryo cells as an assay method have not been completed.     

STATE WATER CONSERVATION STRATEGIES AND ACTIVITIES1

States have the potential to play a major role in moving water conservation from conferences and reports that identify its advantages to actual practice. The research identifies four generic “strategies” that categorize the states' approaches toward conservation and reports on the states' current conservation activities. The four strategies are: reliance on agricultural advisors, leverage incentives, performance standards, and mandatory actions. Four levels of state conservation activity exist. California and Florida maintain the most extensive programs; Arizona, Massachusetts, New Jersey, North Carolina, and Oklahoma also have numerous programs but significantly lower staff commitments; eight additional states maintain more modest conservation effotts. Elsewhere, state directed conservation actions remain minimal and limited to those provided as agricultural advice. The study found support for water conservation the norm among water supply planners.     

Transit bus operator performance and attitudes toward a collision warning system: results of a simulator experiment

OBJECTIVE: This article discusses the results of a simulator experiment to examine the efficacy of a collision warning system for transit bus operators. METHODS: Bus operators from a major metropolitan transit agency were assigned to one of three conditions: a collision warning system with a visual-only driver-vehicle interface, a collision warning system with a visual and auditory driver-vehicle interface, or no collision warning system (baseline). Operators were exposed to a critical event at the end of the simulation, in which a vehicle suddenly stopped in front of the bus while the operator was distracted by an in-vehicle task. Upon completing the experiment, operators who used the collision warning system were asked about their experience using the system, as well as whether or not they would like such a system in real life. RESULTS: Experimental results revealed new information about transit bus operator performance, but indicated no statistically significant differences among the three conditions. Subjective data indicated that operators had a positive attitude toward collision warning system usage. Operators generally liked the collision warning system and felt that a system such as the one used in the experiment would help them in avoiding crashes in the real world. CONCLUSIONS: These findings suggest that a collision warning system for transit bus operators is feasible from the perspective of user acceptance. However, several technical areas still need to be resolved.     

中国大陆土壤中239+240Pu的来源与背景值研究

利用现有大量实测的¹³⁷Cs背景值数据,根据北半球大气沉降¹³⁷Cs/^239+240Pu活度比值32.5（¹³⁷Cs活度校正到2005年）,将中国大陆土壤中¹³⁷Cs转换成对应的^239+240Pu,类比中国大陆¹³⁷Cs-RI模型（¹³⁷Cs-RI MCM）,利用克里金插值方法模拟中国大陆土壤中Pu-RI的空间分布.目前中国大陆土壤中实测^239+240Pu的沉积通量范围在7.3~546 Bq/m²之间,模拟Pu-RI的范围在3~812 Bq/m²之间,并且最大值出现的地点与模拟最大Pu-RI可能出现的区域基本一致,¹³⁷Cs-RI MCM模型对中国大陆土壤中Pu-RI的模拟具有可行性.由于¹³⁷Cs与^239+240Pu沉降的不均匀性,根据中国土壤实测¹³⁷Cs/^239+240Pu的活度比可知,局部区域Pu-RI模拟值可能有偏差.为了更好的说明¹³⁷Cs-RI MCM模型的可行性,本研究利用30~40°N之间中国62个城市位点的^239+240Pu湿沉降通量（I_湿沉降）与相应Pu-RI的值（I_总沉降）进行了比较,发现I_湿沉降和I_总沉降的理论计算均是合理的.     

Comparison of mercury and methylmercury in northern pike and Arctic grayling from western Alaska rivers

In western Alaska, mercury (Hg) could be a potential health risk to people whose diet is primarily fish-based. In 2000, total Hg (THg) and methylmercury (MeHg) were examined in northern pike (Esox lucius) and Arctic grayling (Thymallus arcticus) from two watersheds in western Alaska, the Yukon and Kuskokwim rivers. Whitefish (Coregonus sp.) were also examined from the Kuskokwim River. Pike from the Yukon and Kuskokwim rivers had mean concentrations of THg in muscle of 1.506 and 0.628 mg/kg wet wt, respectively. The mean concentrations of THg in grayling muscle from these rivers were 0.264 and 0.078 mg/kg, respectfully. Whitefish had a mean THg concentration in muscle of 0.032 mg/kg. MeHg, in pike and grayling constituted nearly 100% of the THg concentrations; the proportion was less in whitefish. A significant positive correlation between Hg levels and fish length was also found. Generally, there were no changes in Hg concentrations in pike or grayling over the last several years. Only pike from theYukon River had THg concentrations that exceeded the USFDA action level for human consumption of edible fish (1 mg/kg). Human hazard index for pike was > or = 1 for both adults and children, indicating a potential for toxic concern, especially among children. Further studies are needed to determine the environmental and human health impacts associated with these Hg concentrations in western Alaska, especially in the context of potentially increased consumption of resident fishes when anadromous salmon catches are reduced.     

Phylogeographic Subspecies Recognition in Leopards (Panthera pardus): Molecular Genetic Variation

The incorporation of precise definitions for taxonomic units into wildlife legislation has necessitated the reevaluation of the taxonomy of endangered and threatened species. We used the subspecies recognition criteria proposed by Avise and Ball (1990) and O'Brien and Mayr (1991) to examine the infraspecific taxonomy of the leopard, Panthera pardus , a geographically widespread species with 27 currently recognized trinomial designations. Samples from named subspecies revealed appreciable genetic diversity using three molecular methods: allozymes, mitochondrial DNA restriction sites, and feline-specific minisatellites. Continental populations and subspecies from Africa and Asia possessed the highest amount of molecular genetic variation, whereas relatively lower amounts of diversity were present in island populations. Molecular data were analyzed using three phylogenetic methods (distance-matrix, maximum parsimony, and maximum likelihood) to resolve genetic differentiation below the species level The combined results revealed phylogenetic distinction of six geographically isolated groups of leopards: (1) African, (2) central Asian, (3) Indian, (4) Sri Lankan, (5) Javan, and (6) east Asian. Based on the combined molecular analyses and supporting morphological data (Miththapala 1992), u,e recommend that subspecific leopard taxonomy be revised to comprise eight subspecies: (1) P. p. pardus , Africa; (2) P. p. saxicolor , central Asia; (3) P. p. fusca , Indian subcontinent; (4) P. p. kotiya , Sri Lanka; (5) P. p. melas , Java; (6) P. p. orientalis , Amur; (7) P. p. japonensis , northern China; and (8) P. p. delacouri , southern China. In most cases, designated subspecies conform to historic geological barriers that would have facilitated allopatric genetic divergence.     

Policy-relevant nonconvexities in the production of multiple forest benefits

This paper challenges common assumptions about convexity in forest rotation models which optimize timber plus nontimber benefits. If a local optimum occurs earlier than the globally optimal age, policy based on marginal incentives may achieve suboptimal results. Policy-relevant nonconvexities are more likely if (i) nontimber benefits dominate for young stands while the optimal age depends primarily on timber benefits, or (ii) nontimber benefits dominate for mature stands and also determine the optimal age. Nonconvexities may create either temporary or persistent difficulties. Policymakers may improve efficiency by exploiting the relationship between the timber-only optimum and the global optimum.     

Sperm swimming speed and energetics vary with sperm competition risk in bluegill (<Emphasis Type="Italic">Lepomis macrochirus</Emphasis>)

Under sperm competition, a males fertilization success depends largely on the ejaculate characteristics of competing males. Theoretical models predict that, in external fertilizers, increased risk of sperm competition should result in selection for increased sperm swimming speed. To test this prediction, we studied the behavior of sperm from parental and sneaker male bluegill (Lepomis macrochirus), a fish species characterized by high levels of cuckoldry due to alternative reproductive tactics of males (parentals and cuckolders). Because cuckolders (sneakers and satellites) always spawn in the presence of a parental male, but the reverse is not true, cuckolders experience the greater risk of sperm competition. We show here that the spermatozoa of sneakers have faster initial swimming speeds but shorter periods of motility than the sperm of parental males. Moreover, we show that sperm swimming speeds shortly after activation (when most fertilization occurs) are correlated with starting ATP levels in spermatozoa, suggesting that sperm competition has selected for higher energetic capacity in the sperm of sneakers. Thus, the higher energetic capacity and initial swimming speed of sneaker sperm may explain why, despite having fewer sperm per ejaculate than parentals, sneakers fertilize more eggs than parental males when they compete to fertilize a clutch of eggs.Communicated by L.W. Simmons     

Modeling joint production of wildlife and timber

Production of marketed commodities and protection of natural systems often conflict. A focus on only one goal can result in large losses in other goals and may result in inefficient and unsustainable outcomes. In this paper, we develop a method that combines economic and ecological models in a dynamic and spatial analysis to evaluate land use decisions and find cost-effective alternatives for which it is not possible to do better on one objective without harming another objective. The method is demonstrated using timber production and species conservation on a forested landscape over a 100-year planning horizon. Current land use strategies are simulated and compared with cost-effective alternatives. The approach is compared to a static reserve approach, similar to previous studies, and found to produce substantially more efficient management strategies for the case study landscape.     

Copper, Lead and Zinc Mobility and Bioavailability in a River Sediment Contaminated with Paint Stripping Residue

A river embankment sediment beneath a road bridge in South Australia had been surveyed on a previous occasion to a depth of 10 cm and found to contain high levels of copper, lead and zinc deposited during previous lead and zinc-based primer paint stripping operations prior to repainting the bridge. Since the river embankment is geologically different from the surrounding non-embankment soils, and a sufficient distance from the bridge along the river embankment could not be traversed, the geological background Cu, Pb and Zn fraction was established initially using a solid phase sequential extraction (SPSE) procedure. Assessment of the degree of contamination and extent of vertical mobility was then established. Copper was a minor contaminant and present predominantly as the geological background species. Lead was partitioned evenly between the oxalate soluble fraction and residual fraction to a depth of 30 cm with a decrease in total Pb concentration from 497 to 141 mg Pb kg^–1 while Zn was predominantly in the oxalate soluble fraction to a depth of 15cm with a decrease in concentration from 1013 to 150 mg Zn kg^–1. The reduced rate of nitrification and the lower total concentration of NO₃ ^–-N together with the higher respiratory quotient, combined with the lower microbial quotient, are indicative of microbial stress due to heavy metal toxicity. In the case of Pb and Zn paint stripping residues, these changes in indicators of microbial health are possibly the result of the greater abundance and hence possible bioavailabilty of organo- and chloro-Pb compared to organo- and chloro-Zn complexes.