Spanish LLW and MLW disposal: durability of cemented materials in (Na, K)Cl simulated radioactive liquid waste

The microstructural stability or durability of a specific backfilling pozzolanic-cement mortar, which is employed in Spain, in concrete containers for the storage of low level liquid wastes (LLW) and medium level liquid wastes (MLW), has been studied by means of the Koch-Steinegger test at the temperatures of 20 and 40 degrees C during a period of 365 days. Mortar samples were immersed in salt solutions of 3.46 M NaCl and 3.46 M KCl to simulate the salinity of some radioactive liquid waste matrices. The resistance of the mortar to the saline solution attack is evaluated by the development of the relative flexural strength. The changes of the microstructure were followed by mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Pore solution was extracted and analyzed at different periods of time to know the possible diffusion of sodium, chloride and potassium inside the microstructure.     

Effect of irrigation on the survival of total coliforms in three semiarid soils after amendment with sewage sludge

Sewage sludges are increasingly used in soil amendment programmes, although not without risk since they contain, among other potential hazards, high concentrations of total coliform bacteria. In this paper we have studied the effect of irrigation on the survival of total coliforms in three semiarid degraded soils with different agricultural practices. Fresh sewage sludge was added at 50 g kg(-1) soil, and incubated in both the presence and absence of irrigation. The absence of irrigation led to a sharp decrease in the number of total coliforms in all soils, with the bacteria disappearing in 40 days. Irrigation produced a substantial initial increase in the number of coliforms in the three soils, although after 80 days there was none growing in any of the soils. The results showed that there were significant differences in the survival of coliform bacteria due to the presence or absence of irrigation.     

Characterization of spring phytoplankton communities in the Río de La Plata maritime front using pigment signatures and cell microscopy

The surface abundance and species composition of phytoplankton communities were studied in a section across the continental shelf between the Río de La Plata and the oceanic waters of the Subtropical Convergence, during late spring (November 1999). Algal communities were examined using light microscopy and HPLC-derived (high-performance liquid chromatography) pigment concentrations. The CHEMTAX program was used to estimate the chlorophyll a (chl a) biomass of different algal classes. The inclusion of the most abundant members of the chl c pigment family (chl c₁, chl c₂, chl c₃ and chl c₂ monogalactosyldiacylglyceride esters) in the pigment matrix improved the CHEMTAX interpretation of field data. Using this novel approach four haptophyte populations were distinguished across the studied section, even though they had qualitatively similar pigment signatures, although one subtype lacked 19-hexanoyloxyfucoxanthin (Hex-Fuco). Five different phytoplankton assemblages, spatially segregated by the prevailing environmental conditions, were distinguished during the studied period. All of them showed a complex community structure, formed by a background of small-sized cells such as cyanobacteria, cryptophytes, haptophytes and prasinophyceans, on which diatom, cryptophyte or some haptophyte blooms were overlapped. In the estuarine assemblage, where maximum chl a concentrations where found, diatoms were always the dominant group (30–60% of total chl a), but cryptophytes (10–40%), prasinophyceans (2–20%) and dinoflagellates (2–12%) were also relevant. In the coastal assemblage diatoms were also the dominant group (35–45%), but haptophytes lacking Hex-Fuco were subdominant (20–35%). The continental shelf assemblage showed an almost exclusive dominance (90%) of haptophytes resembling the coccolithophorid E. huxleyi. Another haptophyte (Phaeocystis sp.) was dominant (75–85%) in the Malvinas Current assemblage. The Brazil Current assemblage was characterized by the codominance of cyanobacteria (45%) and haptophytes (35%). These results are discussed in relationship to the complex hydrographic features of the area.Communicated by O. Kinne, Oldendorf/Luhe     

Disability among adults injured in motor-vehicle crashes in the United States

INTRODUCTION: Little population-based information exists about the long-term effects of motor-vehicle crash-related injuries. METHOD: We analyzed data from the 1995 National Health Interview Survey Disability (NHIS-D) Supplement to estimate the prevalence of crash-related disability among noninstitutionalized U.S. adults aged 18 years and older. RESULTS: More than 1.2 million adults were living in their homes with the disabling effects of motor-vehicle crash-related injuries in 1995. The prevalence of crash-related disability was highest for persons in their mid-life years, ages 35-64. Half of the respondents had sustained the injuries more than 5 years before the interview. Forty-one percent of working-aged individuals reported being unable to work because of their disability. CONCLUSIONS: Because crash-related disability is most prevalent during the mid-life years, quality of life and productivity may be affected for decades. These findings highlight the personal and societal burden associated with motor-vehicle crash-related disability in the United States.     

A temporary social parasite of tropical plant-ants improves the fitness of a myrmecophyte

Myrmecophytes offer plant-ants a nesting place in exchange for protection from their enemies, particularly defoliators. These obligate ant–plant mutualisms are common model systems for studying factors that allow horizontally transmitted mutualisms to persist since parasites of ant–myrmecophyte mutualisms exploit the rewards provided by host plants whilst providing no protection in return. In pioneer formations in French Guiana, Azteca alfari and Azteca ovaticeps are known to be mutualists of myrmecophytic Cecropia (Cecropia ants). Here, we show that Azteca andreae, whose colonies build carton nests on myrmecophytic Cecropia, is not a parasite of Azteca–Cecropia mutualisms nor is it a temporary social parasite of A. alfari; it is, however, a temporary social parasite of A. ovaticeps. Contrarily to the two mutualistic Azteca species that are only occasional predators feeding mostly on hemipteran honeydew and food bodies provided by the host trees, A. andreae workers, which also attend hemipterans, do not exploit the food bodies. Rather, they employ an effective hunting technique where the leaf margins are fringed with ambushing workers, waiting for insects to alight. As a result, the host trees’ fitness is not affected as A. andreae colonies protect their foliage better than do mutualistic Azteca species resulting in greater fruit production. Yet, contrarily to mutualistic Azteca, when host tree development does not keep pace with colony growth, A. andreae workers forage on surrounding plants; the colonies can even move to a non-Cecropia tree.     

Formation of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) from a refinery process for zinc oxide used in feed additives: a source of dioxin contamination in Chilean pork

The Republic of Korea found dioxin at concentrations exceeding the Korean maximum residue limit (MRL) in pork (2 pg TEQ g⁻¹ fat) imported from Chile in June 2008. Korea and Chile collaborated and investigated to find out the sources of contamination. An isotope dilution method and high resolution gas chromatography/mass spectrometry (HR-GC/MS) were used for the analysis of PCDD/Fs. PCDD/Fs were found from 2.17 to 36.7 pg TEQ g⁻¹ fat from Chilean pork. 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, 1,2,3,6,7,8-HxCDF, and 2,3,4,6,7,8-HxCDF were found as the major congeners in pork samples. 2,3,4,7,8-PeCDF showed the highest concentration and contributed about 30% among the congeners in most of the samples. 2,3,7,8-TCDD, 1,2,3,7,8,9-HxCDD, OCDD, 2,3,7,8-TCDF, 1,2,3,7,8-PeCDF, 1,2,3,7,8,9-HxCDF, and OCDF were not detected or exist at background levels in the less contaminated samples. Remarkably high concentrations of PCDD/Fs were found in samples of zinc oxide (17 147 pg TEQ g⁻¹), zinc oxide based premix (6673 pg TEQ g⁻¹), and the residue crust (800 pg TEQ g⁻¹) in a mixing chamber in the feed mill. From the results of various investigations, this case concluded that zinc oxide in the feed was the major source of the dioxin contamination in pork. The dioxins were formed from a metal refinery process to collect zinc oxide.     

El Niño Caused Collapse of the Sábalo Fishery (Prochilodus lineatus, Pisces: Prochilodontidae) in a South American River

El Niño is well known to affect marine fishery. The Southern Oscillation, however, may also have a strong effect on riverine fish production in floodplains via its effect on river discharge. In years with high river discharges larger parts of the floodplain are inundated, increasing the surface area of suitable nursery grounds for young fish stock. In this way high river discharges are thought to have a positive effect on fish production, while low discharges are thought to have a negative effect. The collapse of the sábalo fishery in the Pilcomayo River in Bolivia, for instance, can be attributed to the 1990–1995 El Niño event and subsequent overexploitation of the fish stocks.     

Effects of previous sublethal pulse to ammonium nitrate on mortality and total length on Epidalea calamita larvae

Ammonium nitrate is one of the most widespread contaminants related with the viability of natural amphibian populations. In this study we have evaluated in terms of mortality and total length the effects that a previous sublethal pulse to ammonium nitrate generates in Epidalea calamita. Experiments were divided in two phases. In the first one, tadpoles were exposed to two different treatments, with and without a low ammonium nitrate concentration (22 mg NH₄NO₃ L⁻¹). The second phase consisted in static toxicity experiments from both origin treatments with five different nominal concentrations (0, 22, 45, 90 and 180 mg NH₄NO₃ L⁻¹). Results showed that tadpoles that had experienced a previous sublethal exposure showed a negative effect on survival (57% of reduction in the LC₅₀ value) and total length, throughout an increase in their sensitivity. These results could help us to understand the situation of amphibian populations inhabiting aquatic ecosystems exposed to discontinuous and variable pulses of pollutants.