Subsoil TPH contamination in two oil pipeline pumping stations and one pipeline right-of-way in north Mexico

This investigation deals with the characterization carried out in zones around two pipeline pumping stations and one pipeline right-of-way in the north of Mexico. In particular those areas where contamination was evaluated: (a) south area of the separation ditch in the Avalos station, (b) the area between the separation ditch at the Avalos station, (c) km 194 + 420 of the Moctuzma station, and (d) km 286 + 900 in the Candelaria station. Results of this investigation showed that only four samples showed TPH values higher than the Mexican limit for 2004: AVA 1B, with 21,191 mg kg^?1; AVA 1C, with 9348 mg kg^?1; AVA 2B, with 13,970 mg kg^?1; and MOC 2A, with 4108 mg kg^?1.None of the sampled points showed the presence of PAHs at values higher than those found in the Mexican or American legislations. PAH were detected in the range of 0.0004 and 13.05 mg kg^?1.It is suggested to implement surfactant soil washing as a remediation technique for the approximately 600 m³ that need to be treated.     

In Situ flushing of contaminated soils from a refinery: Organic compounds and metal removals

This article demonstrates the applicability of in situ flushing for the remediation of soil contaminated with petroleum hydrocarbons at a Mexican refinery. The initial average total petroleum hydrocarbon (TPH) concentration for the demonstration field test was 55,156 g/kg. After six weeks of in situ flushing with alternate periods of water and water/surfactant, an average concentration of 1,407 mg/kg was reached, achieving a total removal efficiency of 98 percent. At the end of the process, no hydrocarbons such as diesel; gasoline; benzene, toluene, ethyl benzene, and xylene (BTEX); or petroleum aromatic hydrocarbons (PAHs) were found. Iron washing achieved a removal efficiency of 70 percent, and for vanadium, the removal efficiency was 94.4 percent. The volume of soil treated was 41.6 m³ (38 m²), equivalent to 69.5 tons of soil. A rough calculation of the process costs estimated a total cost of $104.20/m³ ($114.00/m²). Our research indicates that there are a few studies demonstrating in situ flushing experiences under field conditions where both organic (TPH, diesel, gasoline, PAHs, BTEX) and metal (iron and vanadium) removals are reported. © 2004 Wiley Periodicals, Inc.     

In utero therapy for lower urinary tract obstruction

Lower urinary tract obstruction has a significant impact on neonatal and child health. Pulmonary hyperplasia and renal impairment could be direct or indirect consequences of this condition leading to significant morbidity and mortality. Evaluation of fetuses with suspected lower urinary tract obstruction is performed not only to confirm the diagnosis but also to assess renal prognosis. Ultrasound examination and urinary analysis aid in the evaluation of these fetuses. The decision to perform fetal intervention in these cases is a difficult one. Vesico‒amniotic fetal shunting, open fetal surgery and more recently endoscopic fetal surgery for this condition are available as possible modalities of fetal intervention. Case selection for fetal intervention is extremely important in order to both avoid unnecessary intervention in those unlikely to survive, and also to avoid procedure related complications in fetuses likely to do well without intervention. Vesico‒amniotic shunting has the advantage of bypassing the obstruction, however it is often associated with complications. Open fetal surgery is not usually recommended because of the complications and high fetal loss rate. Endoscopic surgery to visualise and treat the cause of lower urinary tract obstruction has been tried. Fetal endoscopic surgery is in its infancy and endoscopic procedures are limited to a few groups. This current review addresses evaluation, case selection and therapeutic options for lower urinary tract obstruction in utero. It also discusses the limited data against which the efficacy of the various options can be assessed. The current state of fetal intervention is detailed in the present review. Copyright © 2001 John Wiley & Sons, Ltd.     

Maternal investment in Antarctic fur seals: evidence for equality in the sexes?

Studies of the otariids (fur seals and sea lions), a highly sexually dimorphic group, have provided conflicting evidence of differential maternal expenditure in male and female offspring and, thus, suggestions that they conform to predictions of investment theory are equivocal. Since the mid-1970s, a diversity of research on Antarctic fur seals (Arctocephalus gazella) including studies of their reproductive ecology, lactation energetics, and foraging behaviour have been conducted at Bird Island, South Georgia that have resulted in one of the more complete and diverse data sets for any species of otariid. These long-term data were reviewed to determine whether there was any evidence to support that differential maternal expenditure occurred in Antarctic fur seals. Most of the data examined were collected during five consecutive austral summers from 1988 through 1992 and included years in which local food resources were abundant and scarce. We were unable to detect differences in the sex ratios of pups at birth or sex-biased differences in growth rates estimated from serial data, the number of foraging trips made, the duration of attendance ashore, diving behaviour, suckling behaviour, or milk consumption in any year and in the duration of foraging trips or age at weaning in 2 of 3 years. In addition, we found no evidence of greater reproductive costs between mothers with sons or daughters relative to their reproductive performance the following year. In contrast, sex-biased differences were only found in the duration of foraging trips in 1990, the age at weaning in 1988, and consistently in growth rates estimated from cross-sectional data. We suggest that differential maternal expenditure does not occur in Antarctic fur seals because male pups probably do not gain greater benefit from additional maternal expenditure than female pups. After weaning, males experience a period of rapid juvenile growth over 3–4 years during which time body mass nearly trebles. This growth will almost certainly be dependent upon available food resources then rather than on any maternal expenditure received over the first 4 months of life and, thus, the assumptions of the Trivers and Willard hypothesis are probably invalid for Antarctic fur seals. Received: 10 July 1996 / Accepted after revision: 3 March 1997     

Linking a one-dimensional pesticide fate model to a three-dimensional groundwater model to simulate pollution risks of shallow and deep groundwater underlying fractured till

The one-dimensional pesticide fate model MACRO was loose-linked to the three-dimensional discrete fracture/matrix diffusion model FRAC3DVS to describe transport of the pesticide mecoprop in a fractured moraine till and local sand aquifer (5-5.5 m depth) overlying a regional limestone aquifer (16 m depth) at Havdrup, Denmark. Alternative approaches to describe the upper boundary in the groundwater model were examined. Field-scale simulations were run to compare a uniform upper boundary condition with a spatially variable upper boundary derived from Monte-Carlo simulations with MACRO. Plot-scale simulations were run to investigate the influence of the temporal resolution of the upper boundary conditions for fluxes in the groundwater model and the effects of different assumptions concerning the macropore/fracture connectivity between the two models. The influence of within-field variability of leaching on simulated mecoprop concentrations in the local aquifer was relatively small. A fully transient simulation with FRAC3DVS gave 20 times larger leaching to the regional aquifer compared to the case with steady-state water flow, assuming full connectivity with respect to macropores/fractures across the boundary between the two models. For fully transient simulations 'disconnecting' the macropores/fractures at the interface between the two models reduced leaching by a factor 24. A fully connected, transient simulation with FRAC3DVS, with spatially uniform upper boundary fluxes derived from a MACRO simulation with 'effective' parameters is therefore recommended for assessing leaching risks to the regional aquifer, at this, and similar sites.     

Genotypic variability in age polyethism and task specialization in the honey bee,Apis mellifera (Hymenoptera: Apidae)

Summary The currently accepted model for division of labor in honey bees, Apis mellifera, explains variation in the frequency at which workers perform specific tasks as the result of differences in age and environment. Although well documented, the model is incomplete because it fails to take genotypic variability among workers into account. We show that workers from two genetically distinct strains of honey bees differed in the age at which they began foraging and in the relative frequency at which they foraged for pollen. Workers from the two strains also exhibited significant spatial heterogeneity within the nest, suggesting that they differed in the frequency at which they performed within-nest tasks as well. A heuristic model of division of labor that incorporates genotypic effects is presented.