Analysis of coupled model uncertainties in source-to-dose modeling of human exposures to ambient air pollution: A PM2.5 case study

Quantitative assessment of human exposures and health effects due to air pollution involve detailed characterization of impacts of air quality on exposure and dose. A key challenge is to integrate these three components on a consistent spatial and temporal basis taking into account linkages and feedbacks. The current state-of-practice for such assessments is to exercise emission, meteorology, air quality, exposure, and dose models separately, and to link them together by using the output of one model as input to the subsequent downstream model. Quantification of variability and uncertainty has been an important topic in the exposure assessment community for a number of years. Variability refers to differences in the value of a quantity (e.g., exposure) over time, space, or among individuals. Uncertainty refers to lack of knowledge regarding the true value of a quantity. An emerging challenge is how to quantify variability and uncertainty in integrated assessments over the source-to-dose continuum by considering contributions from individual as well as linked components. For a case study of fine particulate matter (PM_2.5) in North Carolina during July 2002, we characterize variability and uncertainty associated with each of the individual concentration, exposure and dose models that are linked, and use a conceptual framework to quantify and evaluate the implications of coupled model uncertainties. We find that the resulting overall uncertainties due to combined effects of both variability and uncertainty are smaller (usually by a factor of 3–4) than the crudely multiplied model-specific overall uncertainty ratios. Future research will need to examine the impact of potential dependencies among the model components by conducting a truly coupled modeling analysis.     

Application of response surface methodology to the removal of the antibiotic tetracycline by electrochemical process using carbon-felt cathode and DSA (Ti/RuO2-IrO2) anode

The removal of antibiotic tetracycline (TC) from water by electrochemical advanced oxidation process (EAOP) was performed using a carbon-felt cathode and a DSA (Ti/RuO(2)-IrO(2)) anode. The influence of applied current, initial pH and initial TC concentration on TC removal efficiency was investigated. Response surface methodology (RSM) based on Box-Behnken statistical experiment design (BBD) was applied to analyze the experimental variables. The positive and negative effects of variables and the interaction between variables on TC removal efficiency were determined. The applied current showed positive effect, while the initial pH value and initial tetracycline concentration gave negative effect on TC removal. The interaction between applied current and initial pH value was significant, while the interactions of initial TC concentration with applied current or initial pH were not pronounced. The results of adequacy check confirmed that the proposed models were accurate and reliable to analyze the variables of EAOP. The reaction intermediates were identified by high-performance liquid chromatography-mass spectrometry (LC-MS) technique and a plausible degradation pathway for tetracycline degradation was proposed. The acute toxicity experiments illustrated that the Daphnia magna immobilization rate reached the maximum after 240 min of electrolysis and then decreased with the progress of the reaction.     

Interrelationships among foreign direct investments,renewable energy,and CO2 emissions for different European country groups: a panel ARDL approach

Environmental Science and Pollution Research - This study estimated unbalanced panel data analysis to investigate the relationship among CO2 emissions, GDP, renewable and non-renewable energy...     

On the Determination of Odor Thresholds in Air Pollution Control—An Experimental Field Study on Flue Gases from Sulfate Cellulose Plants

From the hygienic point of view, not only the health hazards caused by air pollutants but also the odor from emitted flue gases should be reduced to a minimum. An effective control of the risk of odor at ground level presupposes knowledge of the source concentration of the odoriferous gas as well as its odor threshold. This threshold has to be estimated empirically, as the flue gases often contain a complex mixture of different odoriferous substances, the odor thresholds of which are in most cases unknown. For this purpose a method has been developed for estimating the odor thresholds of flue gases emitted, from different industrial processes. The method, afield method, is based on an exposure procedure, a number of subjects compare different concentrations of the flue gas with samples of fresh air and decide at what concentration the flue gas is no longer noticeable. The gas samples used are neither compressed, nor absorbed or heated before the exposure test. The method has been used in two studies on gases from Swedish sulfate cellulose plants. In order to estimate the effect on the odor threshold of different deodorizing measures, gas samples were taken not only from the stack but also from different phases in the production process. The results and a brief discussion on the practical applications of the method are given.     

Airshed Model Evaluation of Reactivity Adjustment Factors Calculated with the Maximum Incremental Reactivity Scale for Transitional-Low Emission Vehicles

Abstract

The California Air Resources Board recently adopted regulations for light- and medium-duty vehicles that require reductions in the ozone-forming potential or “reactivity,” rather than the mass, of nonmethane organic gas (NMOG) emissions. The regulations allow sale of all alternatively fueled vehicles (AFVs) that meet NMOG exhaust emission standards equivalent in reactivity to those set for vehicles fueled with conventional gasoline. Reactivity adjustment factors (RAFs), the ratio of the reactivity (per gram) of the AFV exhaust to that of the conventionally fueled vehicle (CFV), are used to correct the stringent exhaust emission standards. Complete chemical speciation of the exhaust and conversion of each NMOG species to an appropriate mass of ozone using the maximum incremental reactivity (MIR) scale of Carter determines the RAF. The MIR approach defines reactivity where NMOG control is the most effective strategy in reducing ozone concentrations, and assumes it is not important to define reactivity at other conditions, i.e., where NO_x is the limiting precursor.

This study used the Carnegie/California Institute of Technology airshed model to evaluate whether the RAF-adjusted AFV emissions result in ozone impacts equivalent to those of CFV emissions. A matrix of two ozone episodes in the South Coast Air Basin (SoCAB) of California, two base emission inventories, and exhaust emissions from three alternative fuels that meet the first level of the low emission vehicle standards bounds the expected range of conditions. Although very good agreement was found previously for individual NMOG species,² this study noted deviations of up to ±15 percent from the equal ozone impacts for any vehicle/fuel combination required by the California regulations. These deviations appear to be attributable to differences in spatial and temporal patterns of emissions between vehicle fleets, rather than a problem with the MIR approach. The first formally adopted RAF, a value of 0.41 for 85 percent methanol/15 percent gasoline-fueled vehicles, includes a 10 percent increase based on the airshed modeling. The correction to the RAF is different for other fuels and may be different for air basins other than the SoCAB.     

Exergy for better environment and sustainability

In this paper, some key aspects and definitions of exergy are presented, and practical examples are given in order to highlight its usefulness in design, analysis and performance improvement for various types of energy processes for better environment and sustainable development. The relations between exergy, sustainability and environmental impact are illustrated to show how improving the performance of the process through exergy efficiency affects the environmental impact and sustainable development. Both exergy and energy efficiencies for various systems/processes are also studied for comparison purposes.     

Depollution of indigo dye by anodic oxidation and electro-Fenton using B-doped diamond anode

Hazardous wastes are generated in the synthesis of dyes and pigments applied in industries. Efficient methods are thus needed to clean wastewaters. Here, we use anodic oxidation and electro-Fenton with B-doped diamond anode to degrade the synthetic dye indigo in aqueous sodium dithionite. Results show the near-complete mineralization of the dye within 80 min at 500 mA. Mineralization was faster by electro-Fenton than anodic oxidation. The second-order rate constant (k) for the reaction of indigo with ^·OH was measured as 4.03 × 10⁹ M^?1 s^?1 at pH 3.0 and was compared with the rate constants of reactions between dyes and ^·OH. The results clearly demonstrate that both electro-Fenton and anodic oxidation can be used to depollute dyes in textile effluent with high efficiency and low cost. The main oxidant, ^·OH, being a non-selective reagent, the method could be applied to degrade other organic pollutants.     

An improved user-based beach climate index

In many coastal resort areas of the world, it is likely that optimal climatic conditions for beach use might occur outside the peak of the tourist season. Investigation of this issue together with associated publicity might help to spread the tourism load and hence reduce undesirable social and environmental effects of extreme seasonality in tourist demand. For this to take place, better knowledge of beach user preferences in terms of climate and bathing water temperature is required. Questionnaire surveys were carried out in Wales, Malta and Turkey to establish the preferences of north European beach users for thermal sensation and bathing water temperature, plus priority levels for other climatic attributes. A user-based beach climate index based on these preferences and priorities was formulated. Linkage was made between the user-generated ratings for various climatic conditions and published climate data to evaluate most major Euro-Mediterranean/Black Sea and a range of other beach tourism areas on a month-by-month basis. Results showed excessively hot thermal sensation in many southern and eastern Mediterranean coastal destinations during July and August, the present peak of the beach tourism season. Highest preference was given to water temperatures rather lower than those found in these areas during late summer. Many long haul coastal destinations popular with north European visitors had similar unpleasant thermal sensations over several months. Uncertainties and deficiencies still exist with the system, but from the point of view of north European beach users the final scores generated in this study may be regarded as good approximations of the quality of resort area climates for sedentary beach use.