Marine risk assessment: linear alkylbenzenesulponates (LAS) in the North Sea

The fate of linear alkylbenzenesulponates (LAS) in estuaries and coastal areas of the North Sea has been characterized with simple environmental models. The predicted concentration range in the estuaries around the North Sea (0.9-9 microg LAS l(-1)) was validated by monitoring data (1-9 microg LAS l(-1)). In offshore sites of the North Sea, it is estimated--and experimentally verified for a few sites--that the LAS concentration is below analytical detection limit (i.e., 0.5 microg LAS l(-1)). The effects of LAS on marine organisms have been reviewed. For short-term acute tests, there was no significant difference (p = 0.83) between the mean LC50 values of freshwater and marine organisms (mainly pelagic species tested, 4.1 and 4.3 mg LAS l(-1), respectively). For longer-term chronic tests, it appeared that the sensitivity (mean no-observed effect concentration (NOEC) value) of marine and freshwater organisms (0.3 and 2.3 mg LAS l(-1), respectively) was significantly different pt-test = 0.007). The predicted no-effect-concentrations (PNEC) were 360 and 31 microg LAS l(-1), for freshwater and marine pelagic communities, respectively. Given that the maximum expected estuarine and marine concentrations are 3 to > 30 times lower than the PNEC, the risk of LAS to pelagic organisms in these environments is judged to be low.     

Invasions in Marine Communities: Contrasting Species Richness and Community Composition Across Habitats and Salinity

While many studies of non-native species have examined either soft-bottom or hard-bottom marine communities, including artificial structures at docks and marinas, formal comparisons across these habitat types are rare. The number of non-indigenous species (NIS) may differ among habitats, due to differences in species delivery (trade history) and susceptibility to invasions. In this study, we quantitatively compared NIS to native species richness and distribution and examined community similarity across hard-bottom and soft-sediment habitats in San Francisco Bay, California (USA). Benthic invertebrates were sampled using settlement panels (hard-bottom habitats) and sediment grabs (soft-bottom habitats) in 13 paired sites, including eight in higher salinity areas and five in lower salinity areas during 2 years. Mean NIS richness was greatest in hard-bottom habitat at high salinity, being significantly higher than each (a) native species at high salinity and (b) NIS richness at low salinity. In contrast, mean NIS richness in soft-bottom communities was not significantly different from native species richness in either high- or low-salinity waters, nor was there a difference in NIS richness between salinities. For hard-bottom communities, NIS represented an average of 79% of total species richness per sample at high salinity and 78% at low salinity, whereas the comparable values for soft bottom were 46 and 60%, respectively. On average, NIS occurred at a significantly higher frequency (percent of samples) than native species for hard-bottom habitats at both salinities, but this was not the case for soft-bottom habitats. Finally, NIS contributed significantly to the existing community structure (dissimilarity) across habitat types and salinities. Our results show that NIS richness and occurrence frequency is highest in hard-bottom and high-salinity habitat for this Bay but also that NIS contribute strongly to species richness and community structure across each habitat evaluated.     

Biosorption of Rare-Earth Elements and Yttrium by Heterotrophic Bacteria in an Aqueous Environment

This paper reports the results of the experimental determination of the coefficient of sorption of rare-earth elements and yttrium (REY) under conditions of acidic pH using several strains of heterotrophic bacteria (Microbacterium sp., Curtobacterium sp., Bacillus subtilis, Pseudomonas putida, and Bacillus pumilis) that are widespread in natural and technogenic waters of the Far East (Russia). Insignificant fractionation between heavy and light rare-earth elements, negative cerium and dysprosium anomalies, and a positive europium anomaly were revealed. The selectivity of REY biosorption by gram-positive and gram-negative bacteria, as well as inertia of the biosorption process under more acidic conditions of the medium, were shown.     

Natural aggregates in the performance and durability of concrete: chemical characteristics

This article continues from the earlier feature in Geology Today (2011, v.27, n.4) and looks at the influence of chemical reactivity within concrete due to the presence of unsound aggregates or deleterious material incorporated in the aggregate used in the concrete mix. Some of the more disruptive problems from chemical unsoundness come from the presence of chlorides, which cause rusting in reinforced concrete or, sulphate attack from ground waters. Both of these reactions are relatively common in Britain. Alkali–silica reactions with aggregates and cement is not too prevalent in Britain but can be very prevalent and disruptive elsewhere in the world.     

Dispersion characteristics of low-latitude whistlers

The effect of ions on whistler dispersion characteristics has been studied. It is shown that the significant changes in the dispersion characteristics of low-latitude whistlers are brought about by the presence of ions. The dispersions for Nainital (geomagnetic lat. 19°1'N) and Gulmarg (geomagnetic lat. 24°10'N) are found to peak around 800 Hz. The short whistler sonograms recorded at Nainital and Gulmarg have been analysed, using the complete dispersion equation and the effect of ions has been shown. At higher frequencies the dispersion is found to decrease steadily and becomes independent of ions. Some examples of short whistlers have been found whose characteristics do not conform to the general trend of low-latitude whistlers, and, on the other hand, these whistlers show a constant dispersion unaffected by ions up to a fairly low frequency and thereafter decrease sharply at lower frequencies.