Source-Receptor Relationships for Acid Deposition: Pure and Simple

The Critical Review entitled Source-Receptor Relationships for Acid Deposition: Pure and Simple? was presented by George M. Hidy at the 77th APCA Annual Meeting and Exhibition in San Francisco, California. Dr. Hidy spoke on his paper which had been published in the May 1984 issue of JAPCA. Prepared discussions presented at the Critical Review Session in San Francisco are reproduced here. In addition, discussion initiated from the floor and comments received through the mail have been formalized and are published along with closing remarks by Dr. Hidy. Dr. Paul J. Lioy, Critical Review Committee chairman, served as moderator for the 1984 Critical Review Session.     

Sub-cooled and flashing liquid jets and droplet dispersion I. Overview and model implementation/validation

Many accidents involve two-phase releases of hazardous chemicals into the atmosphere. This paper describes the results of a third phase of a Joint Industry Project (JIP) on liquid jets and two-phase droplet dispersion. The aim of the project is to increase the understanding of the behaviour of sub-cooled non-flashing and superheated flashing liquid jets, and to improve the prediction of initial droplet size, droplet dispersion and rainout.Phase III of the JIP first included scaled experiments for materials with a range of volatilities (water, cyclohexane, butane, propane and gasoline). These experiments were carried out by Cardiff University including measurements of flow rate and initial droplet size across the full relevant range of superheats. See the companion paper II for further details of these experiments and the derivation of new refined correlations for droplet size distribution and Sauter Mean Diameter. Furthermore large-scale butane experiments were carried out by INERIS (France) to ensure that for more realistic scenarios the derived droplet size correlations are accurate.Model validation and model improvements were carried out by DNV Software, including validation of release rate and initial droplet size against the above scaled and large-scale experiments. New correlations for droplet size distribution and Sauter Mean Diameter (SMD) were implemented into the Phast discharge model. These were compared against a range of other droplet size and rainout correlations published in the literature, in conjunction with validation against an extensive set of experiments. It was shown that the new droplet size correlation agrees better against experimental data than the existing Phast correlation. To further improve the rainout prediction, the Phast dispersion model (UDM) was also extended to allow simultaneous modelling of a range of droplet sizes and distributed rainout (rather than rainout at one point).     

A risk assessment tool for contaminated sites in low-permeability fractured media

A risk assessment tool for contaminated sites in low-permeability fractured media is developed, based on simple transient and steady-state analytical solutions. The discrete fracture (DF) tool, which explicitly accounts for the transport along fractures, covers different source geometries and history (including secondary sources) and can be applied to a wide range of compounds. The tool successfully simulates published data from short duration column and field experiments. The use for risk assessment is illustrated by three typical risk assessment case studies, involving pesticides, chlorinated solvents, benzene and MTBE. The model is compared with field data and with results from a simpler approach based on an Equivalent Porous Media (EPM). Risk assessment conclusions of the DF and EPM approaches are very different due to the early breakthrough, long term tailing, and lower attenuation due to degradation associated with fractured media. While the DF tool simulates the field data, it is difficult to conclude that the DF model is superior to an EPM model because of a lack of long term monitoring data. However, better agreement with existing field data by the DF model using observed physical fracture parameters favors the use of this model over the EPM model for risk assessments.     

Inferences About Radionuclide Mobility in Soils Based on the Solid/Liquid Partition Coefficients and Soil Properties

To assist transport modeling in assessments of the radiological impact of a geological repository for radioactive wastes, the mobility of various elements was studied in arable and wetland soils in the Forsmark region, Sweden. Pore water and total element contents were determined for five types of unconsolidated deposits (regolith), spanning a wide range of soil properties with respect to pH and organic matter content. Two soil depths were sampled to capture element mobility in regolith layers affected and unaffected by soil-forming processes. The solid/liquid partition coefficients (K _d values) for most elements varied significantly among regolith types. For most elements, the observed variations in K _d values could be explained by variations in soil properties. For many elements, mobility increased with decreasing soil pH. The results provide a significant addition of data on radionuclide retention in soils, taking account of soil properties and processes.     

History of atmospheric environment

There have been great transitions in the science of air pollution and science publishing since the journal began as the International Journal of Air Pollution in 1958. Atmospheric Environment witnessed the increased understanding of smog photochemistry in the late 1950s and the emerging fears of ozone depletion in the 1970s. The journal has grown, but not without the need to change and occasionally fragment only to reintegrate at a later date. At 9000 pages a year it represents an enormous editorial task that has had to be undertaken by more professional offices. This transition has been helped through the development of electronic tools, but the editorial offices strive to retain their personal relationship with authors and reviewers. An enhanced international perspective recognises the widening contributions made by scientists beyond Europe and North America.     

可持续的移动性:东南非运输业的前景

研究了旨在东非和南非能够发生改善的许多举措.能够在这些国家明显地改善能源效率、减少温室气体的排放.从本地区缺乏资金来源的角度看,给需要的措施提供资金帮助仍然是个问题.     

Modeling the Impacts of Two Bark Beetle Species Under a Warming Climate in the Southwestern USA: Ecological and Economic Consequences

Predicted climate warming is expected to have profound effects on bark beetle population dynamics in the southwestern United States. Temperature-mediated effects may include increases in developmental rates, generations per year, and changes in habitat suitability. As a result, the impacts of Dendroctonus frontalis and Dendroctonus mexicanus on forest resources are likely subject to amplification. To assess the implications of such change, we evaluated the generations per year of these species under three climate scenarios using a degree-day development model. We also assessed economic impacts of increased beetle outbreaks in terms of the costs of application of preventative silvicultural treatments and potential economic revenues forgone. Across the southwestern USA, the potential number of beetle generations per year ranged from 1–3+ under historical climate, an increase of 2–4+ under the minimal warming scenario and 3–5+ under the greatest warming scenario. Economic benefits of applying basal area reduction treatments to reduce forest susceptibility to beetle outbreaks ranged from 7.75/ha (NM) to7.75/ha (NM) to 95.69/ha (AZ) under historical conditions, and 47.96/ha (NM) to47.96/ha (NM) to 174.58/ha (AZ) under simulated severe drought conditions. Basal area reduction treatments that reduce forest susceptibility to beetle outbreak result in higher net present values than no action scenarios. Coupled with other deleterious consequences associated with beetle outbreaks, such as increased wildfires, the results suggest that forest thinning treatments play a useful role in a period of climate warming.     

Defining the Photochemical Contribution to Particulate Matter in Urban Areas Using Time-Series Analysis

Abstract

The objective of this project is to demonstrate how the ambient air measurement record can be used to define the relationship between O₃ (as a surrogate for photochemistry) and secondary particulate matter (PM) in urban air. The approach used is to develop a time-series transfer-function model describing the daily PM₁₀ (PM with less than 10 μm aerodynamic diameter) concentration as a function of lagged PM and current and lagged O₃, NO or NO₂, CO, and SO₂. Approximately 3 years of daily average PM₁₀, daily maximum 8-hr average O₃ and CO, daily 24-hr average SO₂ and NO₂, and daily 6:00 a.m.-9:00 a.m. average NO from the Aerometric Information Retrieval System (AIRS) air quality subsystem are used for this analysis. Urban areas modeled are Chicago, IL; Los Angeles, CA; Phoenix, AZ; Philadelphia, PA; Sacramento, CA; and Detroit, MI. Time-series analysis identified significant autocorrelation in the O₃, PM₁₀, NO, NO₂,CO, and SO₂ series. Cross correlations between PM₁₀ (dependent variable) and gaseous pollutants (independent variables) show that all of the gases are significantly correlated with PM₁₀ and that O₃ is also significantly correlated lagged up to two previous days. Once a transfer-function model of current PM₁₀ is defined for an urban location, the effect of an O₃-control strategy on PM concentrations is estimated by calculating daily PM₁₀ concentrations with reduced O₃ concentrations. Forecasted summertime PM₁₀ reductions resulting from a 5 percent decrease in ambient O₃ range from 1.2 μg/m³ (3.03%) in Chicago to 3.9 μg/m³ (7.65%) in Phoenix.