Modeling of vapor intrusion from hydrocarbon-contaminated sources accounting for aerobic and anaerobic biodegradation

A one-dimensional steady state vapor intrusion model including both anaerobic and oxygen-limited aerobic biodegradation was developed. The aerobic and anaerobic layer thickness are calculated by stoichiometrically coupling the reactive transport of vapors with oxygen transport and consumption. The model accounts for the different oxygen demand in the subsurface required to sustain the aerobic biodegradation of the compound(s) of concern and for the baseline soil oxygen respiration. In the case of anaerobic reaction under methanogenic conditions, the model accounts for the generation of methane which leads to a further oxygen demand, due to methane oxidation, in the aerobic zone. The model was solved analytically and applied, using representative parameter ranges and values, to identify under which site conditions the attenuation of hydrocarbons migrating into indoor environments is likely to be significant. Simulations were performed assuming a soil contaminated by toluene only, by a BTEX mixture, by Fresh Gasoline and by Weathered Gasoline. The obtained results have shown that for several site conditions oxygen concentration below the building is sufficient to sustain aerobic biodegradation. For these scenarios the aerobic biodegradation is the primary mechanism of attenuation, i.e. anaerobic contribution is negligible and a model accounting just for aerobic biodegradation can be used. On the contrary, in all cases where oxygen is not sufficient to sustain aerobic biodegradation alone (e.g. highly contaminated sources), anaerobic biodegradation can significantly contribute to the overall attenuation depending on the site specific conditions.     

Body shape and burial behavior of the sand crab Emerita analoga (Stimpson 1857) in a reflective to intermediate morphodynamic range of sandy beaches

Sand crabs belonging to the genus Emerita are the dominant species on sandy beaches of the Pacific and Atlantic coasts of America. The success of this genus has been attributed to the great phenotypic plasticity of life history traits that enables them to cope with swash climate variability from beach to beach. The burrowing rate and variation in carapace shape of Emerita analoga from south-central Chile were studied on a series of five sandy beaches with contrasting reflective-intermediate swash conditions (harsher swash to benign swash). Environmental sampling was carried out monthly from September 2009 to November 2010, while biological experiments were conducted in September and October 2010. A combination of field experiments, geometric morphometric tools and multivariate analysis was used to assess the relationship between burrowing behavior and carapace shape with variables of swash climate. Our results showed that (1) body shape of E. analoga is directly affected by the frequency of effluent line crossing, (2) burrowing rate of E. analoga is affected directly by shape variability, (3) burrowing rate is affected directly and indirectly by the swash climate variables: frequency of effluent line crossing and mean grain size of sediment. Thus, the physical conditions in the intertidal zone may be the main environmental constraints determining cephalothorax shape, with a wider cephalothorax on beaches with finer sand and more benign physical dynamics, and a narrower shape on beaches with coarser sand and harsher physical dynamics. The latter phenotype (narrower shape) probably allows compensating the high difficulty of burying in coarser sediments.     

DDT polluted meltwater affects reproduction in the mussel Dreissena polymorpha

The zebra mussel Dreissena polymorpha was used to follow the recently reported DDT pollution of Lake Iseo (N. Italy). Histopathological analyses were performed on mussels sampled from March 2005 to April 2006, when high DDT levels were found, and results were compared to those from mussels sampled in 2001/2002, before the pollution event. During the 2005/2006 reproductive season, the first male gamete release happened one month later than the onset of spawning in females who showed a high number of specimens with degenerating oocytes, despite a regular pattern of gametogenesis. These results indicated a disrupting action of DDT on the mechanisms involved in sperm release, and a disturbance in the gametogenic phases of the ovary. Pathological pictures in the digestive gland of many mussels from both 2001/2002 and 2005/2006 have also been observed, but DDT pollution is unable to explain the presence of pathological fields in mussels during 2001/2002, for which a previously reported contamination seems to be the main cause. A possible role of DDT in skewing the sex ratio towards a predominance of females was also discussed, considering the high number of females sampled in 2005/2006.     

Biomonitoring of oral epithelial cells in petrol station attendants: Comparison between buccal mucosa and lateral border of the tongue

Owing to the influence of geno- and cytotoxicity on chemical carcinogenesis, studies have demonstrated that petroleum derivatives are able to induce genetic damage and cellular death with conflicting results so far. The aim of the present study was to comparatively evaluate DNA damage (micronucleus) and cellular death (pyknosis, karyolysis and karyorrhexis) in exfoliated oral mucosa cells from gas petrol attendants using two different anatomic buccal sites: cheek mucosa and lateral border of the tongue. A total of 23 gas petrol attendants and 23 health controls (non-exposed individuals) were included in this setting. Individuals had epithelial cells from cheek and lateral border of the tongue mechanically exfoliated, placed in fixative and dropped in clean slides which were checked for the above nuclear phenotypes. The results pointed out significant statistical differences (p < 0.05) of micronucleated oral mucosa cells from gas petrol attendants for both oral sites evaluated. In the same way, petroleum derivate exposure was able to increase other nuclear alterations closely related to cytotoxicity such as karyorrhexis, pyknosis and karyolysis, being the most pronunciated effects as those found in the lateral border of the tongue. No interaction was observed between smoking and petroleum exposure. In summary, these data indicate that gas petrol attendants comprise a high risk group for DNA damage and cellular death. It seems that the lateral border of the tongue is a more sensitive site to geno- and cytotoxic insult induced by petroleum derivates.     

Continuous monitoring of odours from a composting plant using electronic noses

The odour impact of a composting plant situated in an urbanized area was evaluated by continuously monitoring the ambient air close to the plant during a period of about 4 days using two electronic noses. One electronic nose was installed in a nearby house, and the other one inside the perimeter of the composting plant in order to compare the response of both instruments. The results of the monitoring are represented by tables that report the olfactory class and the odour concentration value attributed to the analyzed air for each of the 370 measurements carried out during the monitoring period. The electronic nose installed at the house detected the presence of odours coming from the composting plant for about 7.8% of the monitoring total duration. Of the odour detections, 86% (25 of 29 measurements) were classified as belonging to the olfactory class corresponding to the open air storage of the waste screening overflows heaps, which was therefore identified to be the major odour source of the monitored composting plant. In correspondence of the measurements during which the electronic nose inside the house detected the presence of odours from the composting plant, the olfactory classes recognized by both instruments coincide. Moreover, the electronic nose at the house detected the presence of odours from the composting plant at issue in correspondence of each odour perception of the house occupants. The results of the study show the possibility of using an electronic nose for environmental odours monitoring, which enables the classification of the quality of the air and to quantify the olfactory nuisance from an industrial source in terms of duration and odour concentration.     

Current status and perspectives of accelerated carbonation processes on municipal waste combustion residues

The increasing volumes of municipal solid waste produced worldwide are encouraging the development of processes to reduce the environmental impact of this waste stream. Combustion technology can facilitate volume reduction of up to 90%, with the inorganic contaminants being captured in furnace bottom ash, and fly ash/APC residues. The disposal or reuse of these residues is however governed by the potential release of constituent contaminants into the environment. Accelerated carbonation has been shown to have a potential for improving the chemical stability and leaching behaviour of both bottom ash and fly ash/APC residues. However, the efficacy of carbonation depends on whether the method of gas application is direct or indirect. Also important are the mineralogy, chemistry and physical properties of the fresh ash, the carbonation reaction conditions such as temperature, contact time, CO₂ partial pressure and relative humidity. This paper reviews the main issues pertaining to the application of accelerated carbonation to municipal waste combustion residues to elucidate the potential benefits on the stabilization of such residues and for reducing CO₂ emissions. In particular, the modification of ash properties that occur upon carbonation and the CO₂ sequestration potential possible under different conditions are discussed. Although accelerated carbonation is a developing technology, it could be introduced in new incinerator facilities as a “finishing step” for both ash treatment and reduction of CO₂ emissions.     

Water quality of the Ribeirão Preto Stream, a watercourse under anthropogenic influence in the southeast of Brazil

It is known that Brazil still has a privileged position of water quantity and quality, but water use has not proceeded in a responsible manner and often results in impairment of quality. This study aims to evaluate limnological parameters, parasites and bacteria, and concentrations of heavy metals (Cd, Pb, Cu, Cr, Mn, Hg, and Zn) in surface water of Ribeirão Preto Stream. The Ribeirão Preto Stream is located in urban areas under anthropogenic influence. The results showed that the levels of dissolved oxygen values were lower than those established by the National Environmental Council (CONAMA Resolution No 357/2005). The reading of electrical conductivity showed values typical of impacted environments. The parasitological analysis revealed the presence of nematode larvae. The bacteriological analysis showed higher values for total coliform and Escherichia coli than those set by the Brazilian National Environment Council (CONAMA). The heavy metals Cd, Pb, Cu, Cr, Mn, Hg, and Zn showed concentrations in accordance with the guidelines established by CONAMA. The results provide data on the quality of these waters and showed the necessity to protect the watercourse from point sources of contamination, recommending their continued monitoring.