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11.
Problem
Limited literature suggests that gasoline prices have substantial effects on reducing fatal crashes. However, the literature focuses only on fatal crashes and does not examine the effects on all traffic crashes.Methods
Mississippi traffic crash data from April 2004–December 2008 from the Mississippi Highway Patrol and regular-grade unleaded gasoline price data from the Energy Information Administration of the U.S. Department of Energy were used to investigate the effects of gasoline prices on traffic safety by age, gender, and race.Results
Gasoline prices have both short-term and intermediate-term effects on reducing total traffic crashes and crashes of females, whites, and blacks. The intermediate-term effects are generally stronger than the short-term effects. Gasoline prices also have short-term effects on reducing crashes of younger drivers and intermediate-term effects on older drivers and male drivers.Impact on Industry
Higher gasoline taxes reduce traffic crashes and may result in additional societal benefits. 相似文献12.
Decades of acid deposition have caused acidification of lakes in Sweden. Here we use data for 3000 lakes to run the acidification model MAGIC and estimate historical and future acidification. The results indicate that beginning in about 1920 a progressively larger number of lakes in Sweden fell into the category of “not naturally acidified” (∆pH > 0.4). The peak in acidification was reached about 1985; since then many lakes have recovered in response to lower levels of acid deposition. Further recovery from acidification will occur by the year 2030 given implementation of agreed legislation for emissions of sulphur (S) and nitrogen (N) in Europe. But the number of catchments with soils being depleted in base cations will increase slightly. MAGIC-reconstructed history of acidification of lakes in Sweden agrees well with information on fish populations. Future acidification of Swedish lakes can be influenced by climate change as well as changes in forest harvest practices. 相似文献
13.
Ian?F.?Dennis Thomas?A.?ClairEmail author Bernard?J.?Cosby 《Environmental Modeling and Assessment》2005,10(4):303-314
Accurate predictions of acid precipitation effects on water resources are important in order to allow a better understanding
of various pollution control strategy outcomes. Dynamic geochemical models have been developed to address this need, but have
to be tested under a variety of environmental conditions to provide confidence in their predictions. The most commonly used
aquatic acidification model in North America and Europe is the model of acidification of groundwater in catchments (MAGIC).
Though extensively used, MAGIC has never been tested in catchments with extremely low ionic strength water and high in natural
organic acids (NOAs) from wetlands, two conditions which are common in large parts of Canada. We calibrated the model for
two catchments located in Nova Scotia, Canada, which had some of the most dilute freshwaters reported in the literature and
very high NOA. We also evaluated the variability inherent in calibration data sets by using five separate data sets collected
over a 15-year period at the same sites. We show good model simulations for the main cations and anions in catchment waters.
However, modeling pH is more difficult in the highly organic waters and requires modification to the acid dissociation constants.
Calculated acid neutralization capacity can also be more difficult to model due to the low ion content making small errors
more important. In theory, multiple calibrations of a model at a same site should produce identical hindcasts and predictions.
In reality, the multiple calibrations produced a series of similar, but not identical outcomes which give a probable range
of past values and future outcomes. We feel that this practical approach to validation is a useful addition to the arsenal
of model testing tools. 相似文献
14.
Filip Moldan Veronika Kronnäs Anders Wilander Erik Karltun Bernard J. Cosby 《Water, Air, & Soil Pollution: Focus》2004,4(2-3):139-160
The MAGIC model was calibrated to 143 lakes in Sweden, all of which are monitored in Swedish national monitoring programmes conducted by the University of Agricultural Sciences (SLU). Soil characteristics of the lake catchments were obtained from the National Survey of Forest Soils and Vegetation also carried out by SLU. Deposition data were provided by the Swedish Meteorological and Hydrological Institute (SMHI). The model successfully simulated the observed lake and soil chemistry at 133 lakes and their catchments. The fact that 85% of the lakes calibrated successfully without being treated in an individual way suggests that data gathered by the national monitoring programmes are suitable for modelling of soil and surface water recovery from acidification. The lake and soil chemistry data were then projected into the future under the deposition scenario based on emission reductions agreed in the Gothenburg protocol. Deposition of sulphur (sea salt corrected) was estimated to decrease from 1990 to 2010 by 65–73%; deposition of nitrogen was estimated to decrease by 53%. The model simulated relatively rapid improvements in lake water chemistry in response to the decline in deposition from 1990 to 2010, but the improvements levelled off once deposition stabilised at the lower value. There was a major improvement of simulated lake water charge balance acid neutralising capacity (ANC) from 1990 to 2010 in all lakes. The modelled lakes were divided into acidification sensitive and non-sensitive. The modelled sensitive lakes are representative of 20% of the most sensitive lakes in Sweden. By 2010, the ANC in the sensitive lakes was 10 to 50 μeq L-1 below estimated pre-industrial levels and did not increase much further from 2010 to 2040. Soils at the majority of the modelled catchments continued to lose base cations even after the simulated decline in acid deposition was complete, i.e. after the year 2010. Based on this model prediction, the acidification of the Swedish soils will in general not be reversed by the deposition reduction experienced over the last 10 years and expected to occur by the year 2010. 相似文献
15.
Sullivan TJ Cosby BJ Webb JR Dennis RL Bulger AJ Deviney FA 《Environmental monitoring and assessment》2008,137(1-3):85-99
A modeling study was conducted to evaluate the acid-base chemistry of streams within Shenandoah National Park, Virginia and
to project future responses to sulfur (S) and nitrogen (N) atmospheric emissions controls. Many of the major stream systems
in the park have acid neutralizing capacity (ANC) less than 20 μeq/L, levels at which chronic and/or episodic adverse impacts
on native brook trout are possible. Model hindcasts suggested that none of these streams had ANC less than 50 μeq/L in 1900.
Model projections, based on atmospheric emissions controls representative of laws already enacted as of 2003, suggested that
the ANC of those streams simulated to have experienced the largest historical decreases in ANC will increase in the future.
The levels of S deposition that were simulated to cause streamwater ANC to increase or decrease to three specified critical
levels (0, 20, and 50 μeq/L) ranged from less than zero (ANC level not attainable) to several hundred kg/ha/year, depending
on the selected site and its inherent acid-sensitivity, selected ANC endpoint criterion, and evaluation year for which the
critical load was calculated. Several of the modeled streams situated on siliciclastic geology exhibited critical loads <0 kg/ha/year
to achieve ANC >50 μeq/L in the year 2040, probably due at least in part to base cation losses from watershed soil. The median
modeled siliciclastic stream had a calculated critical load to achieve ANC >50 μeq/L in 2100 that was about 3 kg/ha/year,
or 77% lower than deposition in 1990, representing the time of model calibration. 相似文献