In vivo distribution and fractionation of indium in rats after subcutaneous and oral administration of [(114m)In]InAs

Two in vivo experiments were carried out in this study. In the first experiment five rats were given two subcutaneous injections of [(114m)In]InAs. Major sites of accumulation were spleen, liver and kidney. The intracellular distribution of indium was examined by differential centrifugation. The cytoplasmic fraction contained most of the indium activity followed by the mitochondrial fraction. Both outcomes are in close agreement with the results obtained in previous studies. Chromatographic separations on a preparative size exclusion column were carried out. It was shown that indium was mostly bound to high molecular mass compounds in serum and in the cytoplasmic fraction of spleen, liver and kidney. In a second experiment five rats were given four oral doses of [(114m)In]InAs over a short period. Prior to this experiment the in vitro solubility of cold InAs in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was determined using graphite furnace atomic absorption spectroscopy. In the case of the SGF only 1.3% of an InAs suspension dissolved after 48 hours incubation at 37 degrees C. InAs was not soluble in SIF. Uptake of InAs after oral administration was minimal (<1%). Due to incomplete removal of traces of [(114m)In]InAs from the gastrointestinal tract, it was impossible to calculate accurately the in vivo distribution over the different organs. As the uptake and consequently the activity in the organs were very low, no further chromatographic separations could be carried out. Considering this very low uptake, it can be concluded that InAs will not accumulate in the body after oral exposure.     

Simulation of transport and composition changes during a blocking episode over the East Atlantic and North Europe

Transport of atmospheric trace gases during a blocking event in the troposphere and lower stratosphere (UTLS) in August 1997 is studied. Considering the frequency of such events it is obvious that they play a significant role for climate and air chemistry and thus the atmospheric environment. The event has been selected because a unique set of composition observations carried out by the CRISTA (Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere) instrument in the UTLS was available for the period of blocking. The regional European Atmospheric Dispersion (EURAD) model system was used for a detailed analysis focusing on ozone and CFC 11 (CFCl₃, Freon) distributions and their temporal and spatial variability. The combination of the CRISTA data and a regional transport chemistry model enabled a unique analysis of transport behaviour of a blocking. This developed an Ω-structure with a deep cut-off low at the western flank of the blocking high and a trough with highly perturbed trace gas fields on the eastern side. Tropopause heights varied intensively and were bended down to rather low levels in the cut-off low and folds appearing in the eastern trough. Results of artificial tracer experiments are presented which show that polluted air from lower tropospheric levels and – in this case – lower latitudes as well as the North American continent may be lifted up to the UTLS in the anticyclonic part of the Ω-block and transported from there over large distances in streamers. Quasi-periodic variations of CFC 11 flux divergence indicate dynamical coupling of the different domains of the block.     

Functional and community-level soil microbial responses to zinc addition may depend on test system biocomplexity

The effect of zinc on soil nitrification and composition of the microbial community in soil was investigated using a full factorial experiment with five zinc concentrations and four levels of biological complexity (microbes only, microbes and earthworms (Eisenia fetida), microbes and Italian ryegrass (Lolium multiflorum var. Macho), and microbes, ryegrass and earthworms). After 6 weeks of exposure, the activity of soil nitrifying bacteria was measured and the microbial community structure was characterized by phospholipid fatty acid (PLFA) analysis. Soil nitrification and several PLFA markers were significantly influenced by either zinc addition and/or the presence of earthworms or ryegrass, and one of the most pronounced changes was the increase of fungi and decrease of bacteria with increasing concentrations of zinc. Of particular interest, however, was the potential interaction between the presence of plants and/or earthworms and the effect of zinc, which the factorial study design allowed us to explore. Such an effect was observed in two cases: Earthworms reduced the positive effect of zinc on the fungal biomass (ANOVA, p=0.03), and the effect of earthworms on the soil nitrification activity depended on zinc concentration (ANOVA, p<0.05). The effect of earthworm presence was not very large, but it does show that multispecies tests might give information about metal toxicity or bioavailability that cannot be predicted from single-species tests.     

Use of Pb blast furnace slag as a partial substitute for fine aggregate in cement mortar

The technical properties of cement mortars containing natural fine aggregate that is replaced by lead blast furnace slag at 25 and 35% level were assessed at fixed water-to-cement (W/C) ratio and at fixed flow table value. The leachabilities of some toxic elements from the cement mortars were also assessed to test the environmental suitability of the slag for use in preparation of cement mortar. At fixed W/C ratio, the strength of the mortar decreased with increase of the slag content. On the other hand, at fixed consistency, strength increased with increasing slag content in the mortar composition. The concentrations of some toxic elements in the leachates collected from the mortars containing slag were slightly higher than for the control mortar, but the concentrations in the leachates remained within the regulatory limits for recycling in construction applications. For most elements, leaching from a mortar containing 35% of slag was similar to that from a mortar containing 25% of slag. Therefore, 35% of natural sand can be beneficially replaced with Pb slag to produce cement mortar without affecting the mechanical and leaching properties studied in this work.     

Unraveling the causes of the toxicity of extremely acid waters of volcanic origin

A river ecosystem in East Java, Indonesia, fed by a volcanic lake with high concentrations of dissolved metals and a low pH, was found to support only few macroinvertebrates. To unravel the causes of toxicity and to determine the level of dilution necessary to obtain non-toxic water, a bioassay was conducted with the fairy shrimp Thamnocephalus platyurus. A partial toxicity identification evaluation (TIE) approach was used with EDTA as a chelating agent to relate toxicity to pH and metal concentrations. Three water samples were tested, with pHs ranging from 0.72 to 4.5, and diluted with water from a neutral river to different degrees. The dilution factor necessary to achieve no more than 50% mortality in the Thamnotox test (Ldf(50)) varied from >300 at the most acidic site, to 7 for water of pH 2.6 and 1.5 for water of pH 4.5. Toxicity was best explained from both low pH and high concentrations of metals, especially Al and Fe. The key role of Al and Fe in the toxicity was confirmed by relating concentrations of the different compounds in the river water to toxicity data from the literature. EDTA addition did not significantly influence Ldf(50) or the lethal pH 50% (LpH(50)), suggesting a large effect, besides cationic components and pH, of anions (F, SO(4) and Cl).     

Influence of temperature and soil type on the toxicity of three pesticides to Eisenia andrei

Expansion of agriculture in the tropics has increased the use of pesticides that may affect the soil ecosystems. Few studies so far determined the effects of pesticides in the tropics and tropical risk assessment therefore often relies on data from temperate conditions. Hence we compared the toxicity of chlorpyrifos, carbofuran and carbendazim to the earthworm Eisenia andrei at two different temperatures reflecting temperate and tropical conditions. The toxicity of the three pesticides in both conditions decreased in the order carbendazim > carbofuran > chlorpyrifos. For chlorpyrifos and carbofuran, but not for carbendazim, survival was more sensitive at the higher temperature, probably due to increased earthworm activity. Sub-lethal effects (reproduction and growth) however, varied inconsistently with temperature and soil types. We conclude that toxicity of pesticides in tropics may not be predicted from data generated under temperate conditions, even within the same species.     

Assessing the impact of organic and inorganic amendments on the toxicity and bioavailability of a metal-contaminated soil to the earthworm Eisenia andrei

Metal-contaminated soil, from the El Arteal mining district (SE Spain), was remediated with organic (6 % compost) and inorganic amendments (8 % marble sludge) to reduce the mobility of metals and to modify its potential environmental impact. Different measures of metal bioavailability (chemical analysis; survival, growth, reproduction and bioaccumulation in the earthworm Eisenia andrei), were tested in order to evaluate the efficacy of organic and inorganic amendments as immobilizing agents in reducing metal (bio)availability in the contaminated soil. The inorganic amendment reduced water and CaCl₂-extractable concentrations of Cd, Pb, and Zn, while the organic amendment increased these concentrations compared to the untreated soil. The inorganic treatment did not significantly reduce toxicity for the earthworm E. andrei after 28 days exposure. The organic amendment however, made the metal-contaminated soil more toxic to the earthworms, with all earthworms dying in undiluted soil and completely inhibiting reproduction at concentrations higher than 25 %. This may be due to increased available metal concentrations and higher electrical conductivity in the compost-amended soil. No effects of organic and inorganic treatments on metal bioaccumulation in the earthworms were found and metal concentrations in the earthworms increased with increasing total soil concentrations.