This article describes various statistical analyses of plume‐length data to evaluate the hypothesis that the presence of ethanol in gasoline may hinder the natural attenuation of hydrocarbon releases. Plume dimensions were determined for gasoline‐contaminated sites to evaluate the effect of ethanol on benzene and toluene plume lengths. Data from 217 sites in Iowa (without ethanol; set 1) were compared to data from 29 sites in Kansas that were contaminated by ethanol‐amended gasoline (10% ethanol by volume; set 2). The data were log‐normally distributed, with mean benzene plume lengths (± standard deviation) of 193 ± 135 feet for set 1 and 263 ± 103 feet for set 2 (36% longer). The median lengths were 156 feet and 263 feet (69% longer), respectively. Mean toluene plume lengths were 185± 131 feet for set 1 and 211 ±99 feet for set 2 (14% longer), and the median lengths were 158 feet and 219 feet (39% longer), respectively. Thus, ethanol‐containing BTEX plumes were significantly longer for benzene (p < 0.05), but not for toluene. A Wilcoxon signed rank test showed that toluene plumes were generally shorter than benzene plumes, which suggests that toluene was attenuated to a greater extent than benzene. This trend was more pronounced for set 2 (with ethanol), which may reflect that benzene attenuation is more sensitive to the depletion of electron acceptors caused by ethanol degradation. These results support the hypothesis that the presence of ethanol in gasoline can lead to longer benzene plumes. The importance of this effect, however, is probably site‐specific, largely depending on the release scenario and the available electron acceptor pool.

No abstract

Flow-through aquifer columns were used to investigate the feasibility of adding sulfate, EDTA-Fe(III) or nitrate to enhance the biodegradation of BTEX and ethanol mixtures. The rapid biodegradation of ethanol near the inlet depleted the influent dissolved oxygen (8 mg l(-1)), stimulated methanogenesis, and decreased BTEX biodegradation efficiencies from > 99% in the absence of ethanol to an average of 32% for benzene, 49% for toluene, 77% for ethylbenzene, and about 30% for xylenes. The addition of sulfate, EDTA-Fe(III) or nitrate suppressed methanogenesis and significantly increased BTEX biodegradation efficiencies. Nevertheless, occasional clogging was experienced by the column augmented with EDTA-Fe(III) due to iron precipitation. Enhanced benzene biodegradation (> 70% in all biostimulated columns) is noteworthy because benzene is often recalcitrant under anaerobic conditions. Influent dissolved oxygen apparently played a critical role because no significant benzene biotransformation was observed after oxygen was purged out of the influent media. The addition of anaerobic electron acceptors could enhance BTEX biodegradation not only by facilitating their anaerobic biodegradation but also by accelerating the mineralization of ethanol or other substrates that are labile under anaerobic conditions. This would alleviate the biochemical oxygen demand (BOD) and increase the likelihood that entraining oxygen would be used for the biotransformation of residual BTEX.

Dyeing with cochineal extract has been carried out in Mexico since pre‐Hispanic times as a handcraft process. However, this has limited its application on fabrics other than wool. An experiment was designed to study the influence of mordant concentration on colour behaviour in cotton fabric dyed with cochineal extract at the laboratory. At the same time, colour fastness was determined by applying six fastness tests to define the quality of the dyed fabric. It was concluded that, when there was a larger concentration of metallic ions in the mordant, colour fixation in the fabric was better, as there was less lightness in the red hue of the fabric. In addition, the more hydrogen ions present because of acids, the more intense the red hue. A decreasing trend in the colour fastness tests was observed: dry rubbing > artificial light > acids > alkalis > domestic washing > hot water.

No abstract