The crayfish as a “biological indicator” of aquatic contamination by heavy metals

Cu, Cd. Mg, Mn and Ni concentrations in whole Cambarus bartoni, trapped from Nepahwin Lake, Joe Lake and Wizard Lake, lying at distances of 10, 30 and 150 km, respectively, from the Sudbury smelters in Northeastern Ontario, showed an inverse relationship with the distance of the habitat from the emission site. Highest concentrations of Cu were observed in the hepatopancreas, Cd in the hepatopancreas and the gut, Fe and Mn in the gut, and Mg in the exoskeleton. Tissue concentrations of Ni and Zn were highly variable. Differences between males and females at each sampling site were not significant at the 5% level. The general relationship between crayfish tissue metal concentrations at the three sites was Cu > Mg > Mn > Zn > Ni > Cd. This observed relationship, except for Mg and Mn, agreed with the concentration relationship of these metals in the water and the sediments (top 10–20 cm) in the three lakes. In laboratory studies, Cu concentrations in the hepatopancreas, gills, exoskeleton and the viscera increased significantly over the control during the 4-weeks exposure to 125,250 and 500 μg Cu 1⁻¹. Hepatopancreas, in general, had the highest Cu concentration, and the exoskeleton, the lowest. Relationship between Ni exposure and the tissue Ni concentrations in the four treatments was 800 μg Ni l⁻¹ > 400 μg Ni l⁻¹ = 200 μg Ni l⁻¹ > control, while between the exposure periods and the tissue Ni concentrations was week 4 > week 1 > week 3 = week 2. Highest Ni concentrations at the end of the 4-week exposure to Ni were observed in the gut, gills and the hepatopancreas, and the lowest in the viscera. The present study suggests that Cambarus bartoni is a reliable indicator of the presence of class B and borderline elements with specific gravity > 5 in the aquatic environment. However, their value as biomonitors of variations in Cu and Ni concentrations in freshwater ecosystems is debatable.     

Das Verhältnis von Bautechnik und Festigkeitslehre in Gerstners “Handbuch der Mechanik” – Zum 250. Geburtstag von Franz Joseph Ritter von Gerstner

On the relationship between construction engineering and strength of materials in Gerstner's “Handbook of Mechanics”. Commemorating Franz Joseph Ritter von Gerstner's 250^th birthday. Like nobody else before him Gerstner based the theory of material strength in his “Handbook of Mechanics” on experiments. To this end he discussed the classic experimental stress analyses undertaken by Musschenbroek, Rondelet, Eytelwein, Rennie, Telford, Brown, Brunel, Barlow, Tredgold, Navier and Dufour. He also carried out extensive test series himself, for which he designed his own devices for determining tensile and bending strength. Gerstner's experiments on the tensile strength of wrought iron and steel, for example, set standards in terms of precision, methodology and application. As part of the design work for a chain suspension bridge in Prague he developed a polynomial formula for the stress‐strain diagram of steel and wrought iron, the parameters for which he determined himself through experiments. Gerstner clearly differentiated between a linear region (“perfect elasticity”) and a nonlinear region (“imperfect elasticity”) and warned against exceedance of the proportionality limit, particularly for chain suspension bridges. He also dealt extensively with the bending strength of timber and iron structures. With his empirically accentuated theory of material strength Gerstner established the basic principles of a physically substantiated theory of proportions for structural and machine engineers, which formed the historical‐logical transition to structural theory and classic dimensioning theory.     

“Response of pile embedded in stochastic ground media” by Suzuki M, Takada T. Structural Safety 1997; 19(1): 105–120

The discusser presents a few comments on the analytical model for an elastic foundation and the autocorrelation function for stochastic ground media which are applied in the paper. He suggests the scale of fluctuation which governs the spatial variability of the stochastic ground media and also discusses on the correlation free upper bounds of pile responses.     

Characterization of Linoleum. Part 1: Measurement of Volatile Organic Compounds by use of the Field and Laboratory Emission Cell, “FLEC”⋆

The volatile organic compounds (VOCs) emitted from 12 linoleum samples were measured by use of the “Field and Laboratory Emission Cell” (FLEC) with sampling on Tenax TA followed by thermal desorbtion and GC/FID or GC/MS analysis. Major VOCs were alkanals, alkenals and fatty acids. The emissions were measured after 24 h in FLEC and again after one month's storage in a well ventilated room. The emission profiles of hexanal, nonanal and propanoic acid were modeled for four linoleum samples using a new exponential diffusion model. The time required to reach 50% of the odor threshold concentrations in a standard room was from 113 to 2296 hours. The applicability of the diffusion model for modeling long-term emission needs to be further evaluated considering possible continuous oxidative emission.