A Sensitivity Analysis of Ozone Formation to Ambient Air Composition by Means of Photochemical Models

The prediction of the atmospheric concentration of ozoneand of other photochemical pollutants represents one of themajor scientific challenges in the study of urban airquality. To this aim, photochemical models are widelyapplied as support tools for regulatory purposes, but theirresults are known to be affected by several uncertainties,in boundary conditions, geographical and meteorologicaldata and the chemical composition of emission and ambientair as well. Also the mechanism selected to describe theurban chemistry may lead to large differences in the modelresults. In this work, the influence of ambient air composition onthe results of photochemical model has been studied using a simple Lagrangian trajectory model coupled with different chemical sub-models (CB-IV and a simplified version of EMEP). To this aim a parametric sensitivity study of ozone with respect to its precursors' concentration was performed withreference to the same meteorological conditions and by simulatingdifferent scenarios characterized by specific emitted pollutantsconcentration. Rather than analyzing sensitivity by changing initial composition, an analytical local sensitivity concept has been applied; this allowed evaluation the influence of initial concentration on the predicted ozone concentration andto discriminate between VOC-sensitive and NOx-sensitive kineticregimes. Finally, these results have been successfully comparedwith those obtained applying the concept of photochemical indicators (i.e. O₃/NOy and H₂O₂/HNO₃ ratios).     

Complex co‐substrate addition increases initial petroleum degradation rates during land treatment by altering bacterial community physiology

A pilot‐scale land treatment unit (LTU) was constructed at the former Guadalupe oil production field with the purpose of investigating the effect of co‐substrate addition on the bacterial community and the resulting rate and extent of total petroleum hydrocarbon (TPH) degradation. The TPH was a weathered mid‐cut distillate (C10‐C32) excavated from the subsurface and stockpiled before treatment. A control cell (Cell 1) in the LTU was amended with nitrogen and phosphorus while the experimental cell (Cell 2) was amended with additional complex co‐substrate—corn steep liquor. During the pilot LTU operation, measurements were taken of TPH, nutrients, moisture, aerobic heterotrophic bacteria (AHB), and diesel oxidizing bacteria (DOB). The bacterial community was also assayed using community‐level physiology profiles (CLPP) and 16S rDNA terminal restriction fragment (TRF) analysis. TPH degradation in both cells was characterized by a rapid phase of degradation that lasted for the first three weeks, followed by a slower degradation phase that continued through the remainder of the project. The initial rate of TPH‐degradation in Cell 1 (?0.021 day^?1) was slower than in Cell 2 (?0.035 day^?1). During the slower phase, degradation rates in both cells were similar (?0.0026 and ?0.0024 respectively). AHB and DOB counts were similar in both cells during the fast degradation phase. A second addition of co‐substrate to Cell 2 at the beginning of the slow degradation phase resulted in an increased AHB population that lasted for the remainder of the project but did not affect TPH degradation rates. CLPP data showed that co‐substrate addition altered the functional capacity of the bacterial community during both phases of the project. However, TRF data indicated that the phylogenetic composition of the community was not different in the two cells during the fast degradation phase. The bacterial phylogenetic structure in Cell 2 differed from Cell 1 after the second application of co‐substrate, during the slow degradation phase. Thus, co‐substrate addition appeared to enhance the functional capacity of the bacterial community during the fast degradation phase when the majority of TPH was bioavailable, resulting in increased degradation rates, but did not affect rates during the slow degradation phase when the remaining TPH may not have been bioavailable. These data show that co‐substrate addition might prove most useful for applications such as land farming where TPH is regularly applied to the same soil and initial degradation rates are more important to the project goals. © 2003 Wiley Periodicals, Inc.     

Reporting chlorinated dibenzo-p-dioxin and dibenzofuran data in scientific publications

A literature review of recent work involving the determination of chlorinated dibenzo-p-dioxins (CDD) and dibenzofurans (CDF) in fish and incinerator samples has shown many irregularities and omissions in the reported data. Although some of these result from non-standardized nomenclature and reporting practices and do not affect the overall conclusions reached, in some cases omissions in reporting experimental procedures raise important concerns regarding the validity of data and make comparison of data from different investigations difficult. It is not always necessary or even desirable to report every experimental detail of work performed, however, the ultra-trace determination of CDDs and CDFs in complex environmental samples is still at a stage where omission of key experimental details can affect the interpretation of results.     

Alteration of brain electrical activity by electromagnetic field

To better understand the affect of different levels of EMF on one’s brain activity, the Hodgkin–Huxley model has been used to describe the generation of an active potential in the nerve cell membrane. The theoretical calculations have shown that by the simultaneous affect of both passing an electrical potential and external very low frequency AC, one’s excitation pulses may be suppressed beginning with a certain level of external current. The level of this current depends on the frequency. It is postulated that to eliminate this suppression, the brain increases its normal level relatively to the lower limit. It is also postulated that the brain “tunes up” in the presence of external AC, by increasing the amplitude of its own excitation signals so that suppression does not occur. It is possible that this “tuning” process lasts some time after removing the external EMF as the brain adapts. This has been observed experimentally.     

Simulation of a waste incineration process with flue-gas cleaning and heat recovery sections using Aspen Plus

In the present paper, the modeling of a dual-purpose plant for the production of electrical and thermal energy from the heat treatment of solid wastes is presented. Particularly, the process has been modeled by using the Aspen Plus Shell, with the aim of performing a study about the applicability of this software in the simulation of a solid waste incineration process, which involves complex gas-solid reactions where the solids are referred to as "non-conventional". The model is developed to analyze and quantify the expected benefits associated with refuse derived fuel (RDF) thermal utilization; thus attention is focused on the performance of the energy recovery section.     

IMPACT OF SEWAGE TREATMENT MODIFICATIONS ON WATER QUALITY OF A RESERVOIR1

ABSTRACT. As a result of several investigations conducted in the Department of Civil Engineering through the Water Resources Research Center at The University of Tennessee, dating from 1966 to the present, a rather comprehensive surveillance of water quality conditions has been maintained in Forth Loudoun Reservoir on the Tennessee River near Knowville, Tennessee. During the period covered by these investigations, the Knoxville Third Creek Sewage Treatment Plant was upgraded from a primary plant to a secondary (activated sludge) treatment plant. Comparison of the collected data is being undertaken herein to elucidate the impact of these modifications upon water quality conditions in the reservoir. Consideration is given to the improvements of water quality as related to the expenditure for modification of the treatment facilities. In addition, comment is directed toward the public health significance of the water quality conditions determined.     

A mild photochemical approach to the degradation of phenols from olive oil mill wastewater

Photooxidation of cathecol (1) is carried out in aqueous solution at lambda > 300 nm using different sensitizers: rose bengal (RB), 9,10-dicyanoanthracene (DCA), 2,4,6-triphenylpyrylium tetrafluoroborate (Pyryl). The highest degradation is observed in the UV/RB-sensitized reaction (66% after 15 h of irradiation), mineralization and formation of dimers are the final events. This procedure has been extended to tyrosol (2), caffeic acid (3), vanillic acid (4), 4-hydroxycinnamic acid (5) and 4-hydroxybenzoic acid (6) as well as to a mixture of all phenols. A reduced toxicity of the UV/RB-irradiated solutions of cathecol and tyrosol towards alga Ankistrodesmus braunii is also verified.     

Microscale variation in<Emphasis Type="Italic"> Aat</Emphasis> (aspartate aminotransferase) is supported by activity differences between upper and lower shore allozymes of<Emphasis Type="Italic"> Littorina saxatilis</Emphasis>

The role of natural selection in maintaining inherited variation in morphological characters is indisputable. In contrast, genetic variation in allozyme loci is mostly assumed neutral or under weak selection, although enzyme functions are critical to central metabolic processes. A locus coding for aspartate aminotransferase (AAT) is polymorphic with two alleles in the rocky shore gastropod Littorina saxatilis. One allele (Aat ¹²⁰ ) is most frequent (0.8–0.9) in upper shore subpopulations, while the other (Aat ¹⁰⁰ ) dominates (0.7–0.8) lower shore subpopulations only meters below. Earlier studies show this variation to be maintained by divergent selection, but the mechanism is unknown. We measured enzyme activities in AAT extracts from individuals of known Aat genotype in populations from two islands and at three different temperatures. In all treatments lower shore homozygotes (Aat ^100/100 ) had higher enzyme activity than upper shore homozygotes (Aat ^120/120 ), with heterozygotes having intermediate levels of activity. AAT has a central role in anaerobic energy production in marine mollusks during low-tide periods of emergence, and it might appear surprising that upper shore snails, which are most likely to be emerged, have lower enzyme activity. However, upper shore snails are forced to survive long periods of desiccation, and a low metabolic rate will help to conserve limited resources of energy and nutrients and reduce accumulation of waste products.Communicated by L. Hagerman, Helsingør