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.     

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.     

Toxaphen in der Umwelt

Residue analysis of toxaphene has been difficult because of the complexity of the technical mixture consisting of a high number of compounds with very similar structure and differing chlorine content. Furthermore, the composition of toxaphene in environmental samples varies widely and is normally not related to that of the technical mixture. Therefore, quantification of single components in environmental samples was impossible. After the isolation and identification of a great number of components during the last decade, enough standards are available for the reliable quantification of toxaphene in all environmental compartments. Recently, most research has been performed on the separation of chiral components of toxaphene with a view to identifying the degradation mechanisms and distribution pathways.     

Accumulation of weathered polycyclic aromatic hydrocarbons (PAHs) by plant and earthworm species

Experiments were conducted to assess the bioavailability of polyclycic aromatic hydrocarbons (PAHs) in soil from a Manufactured Gas Plant site. Three plant species were cultivated for four consecutive growing cycles (28 days each) in soil contaminated with 36.3 microg/g total PAH. During the first growth period, Cucurbita pepo ssp. pepo (zucchini) tissues contained significantly greater quantities of PAHs than did Cucumis sativus (cucumber) and Cucurbita pepo ssp. ovifera (squash). During the first growth cycle, zucchini plants accumulated up to 5.47 times more total PAH than did the other plants, including up to three orders of magnitude greater levels of the six ring PAHs. Over growth cycles 2-4, PAH accumulation by zucchini decreased by 85%, whereas the uptake of the contaminants by cucumber and squash remained relatively constant. Over all four growth cycles, the removal of PAHs by zucchini was still twice that of the other species. Two earthworm species accumulated significantly different amounts of PAH from the soil; Eisenia foetida and Lumbricus terrestris contained 0.204 and 0.084 microg/g total PAH, respectively, but neither species accumulated measurable quantities 5 or 6 ring PAHs. Lastly, in abiotic desorption experiments with an aqueous phase of synthetically prepared organic acid solutions, the release of 3 and 4 ring PAHs from soil was unaffected by the treatments but the desorption of 5-6 ring constituents was increased by up to two orders of magnitude. The data show that not only is the accumulation of weathered PAHs species-specific but also that the bioavailability of individual PAH constituents is highly variable.     

Organochlorine levels in edible fish from the Marmara Sea, Turkey

Samples of 12 edible fish species from the Marmara Sea were analyzed for organochlorines (PCBs, DDTs, HCB, HCHs, toxaphene, etc.). The results showed that the total concentrations ranged from 329.41 ng/g fat to 1453.87 ng/g fat. DDT group components made up almost half or more of organochlorine contamination. Levels in red mullet were compared with those from neighbor seas. The sum of DDTs as well as HCHs concentrations were markedly lower than in the Black Sea but higher in the Aegean Sea and Mediterranean. Thus, inflow from the Black Sea might be considered as a contamination source for DDT and HCH contamination. On the other hand, total PCB concentration (sum of congeners 28, 52, 101, 118, 138, 153 and 180) detected in this study was comparable or lower than those from the Aegean Sea and Mediterranean. Toxaphene was a minor contaminant. Measured values were below maximum residue levels for human consumption.     

Property rights regimes and the management of resources

The property rights regime is an important link between the yield of a natural resource and the appropriation and maintenance incentives of its users. This paper discusses the theoretical background for this link and provides insights as to the function of the property rights regime, drawing from recent developments in the economics literature on optimal ownership patterns and the theory of repeated games. The performances of different resource ownership patterns are evaluated using the criterion of economic efficiency. The economic theory of property rights is based on the idea that, because contractual arrangements are bound to be incomplete, there is scope for opportunistic behaviour and therefore the resulting resource management is likely to be inefficient. Optimal resource ownership patterns are viewed as solutions to the problem of structuring private users' incentives in accordance with the socially desirable management of resources.     

Production of Fe2O3 from FeSO4·xH2O formed in galvanizing works

FeSO₄·xH₂O is generated in large amounts in galvanizing workshops. It can be reutilized by conversion to Fe₂O₃. In this study, the recovery of Fe₂O₃ from FeSO₄·xH₂O formed in the galvanizing process has been examined. The experimental work was carried out at various temperatures and times in the oxidizing medium. The reaction temperatures and times were selected as 450, 500, 550, 600, 650, 700, 800 and 900°C, and 15, 30, 45, 60, 90 and 120 minutes, respectively. In order to determine the amount of Fe₂O₃, a titrimetric method was applied. The reaction products were characterized by means of IR and XRD techniques.The extent of conversion is low at temperatures below 650°C. Almost all of the iron (II) sulfate in the original sample was converted to iron(III) oxide at 650°C (120 min), 700°C (90 min), 800°C (60 min) and 900°C (45 min).