In situ and laboratory bioassays using Poecilia reticulata Peters, 1859 in the biomonitoring of an acidic lake at Camaçari, BA, Brazil

The suitability and viability of acute in situ bioassays were investigated in the biomonitoring program of an acidic lake contaminated with sulphur residues. Responses of organisms observed in laboratory and in situ bioassays were also assessed to determine whether or not they were similar and comparable, regarding accuracy and precision. Newborn Poecilia reticulata were employed as test organisms and exposed to the same water samples under in situ and laboratory conditions. Mortality/immobility was the endpoint assessed and dead/immobile organisms were counted at various time intervals during exposure. The mean calculated LT50 values and 95% confidence intervals were 1.61 (1.36-1.87) h in the laboratory bioassays and 0.72 (0.55-0.89) h in the in situ bioassays. Statistical comparison of these values revealed a significant difference (p<0.05). In situ bioassays were more accurate than those carried out in the laboratory, demonstrating higher sensitivity and better reproduction of what occurs in nature, while laboratory bioassays were more precise.     

Does lipophilicity of toxic compounds determine effects on drought tolerance of the soil collembolan Folsomia candida?

The ability of Collembola to survive drought stress is crucial for their distribution in the terrestrial environment. Previous studies have suggested that several toxic compounds affect the drought tolerance of Folsomia candida in a synergistic manner and that these compounds have the feature in common that they elicit their toxicity by causing membrane damage. We hypothesised that the detrimental effect of toxic chemicals on drought tolerance in F. candida depends on the lipophilicity (log K(ow)) of the compound because a higher log K(ow) would mean a closer interaction with membranes. In this study the three chemicals 4-nonylphenol, pyrene and p,p'-DDE were tested. Surprisingly, 4-nonylphenol, with the lowest log K(ow), was the most potent with respect to reducing drought tolerance followed by pyrene, suggesting that interactions between drought tolerance and chemical stress do not depend on lipophilicity alone.     

Phytostabilization of a metal contaminated sandy soil. I: Influence of compost and/or inorganic metal immobilizing soil amendments on phytotoxicity and plant availability of metals

In a lysimeter set-up, compost addition to an industrial contaminated soil slightly reduced phytotoxicity to bean seedlings. The "Phytotoxicity Index" (on a scale from 1 to 4) decreased from 3.5 to 2.8. The same treatment also reduced metal accumulation in grasses: mean Zn, Cd and Pb concentrations decreased respectively from 623 to 135, from 6.2 to 1.3 and from 10.7 to <6 mg kg-1 dry weight. When combined with inorganic metal immobilizing amendments, compost had a beneficial effect on plant responses additional to the inorganic amendments alone. Best results were obtained when using compost (C)+cyclonic ashes (CA)+steel shots (SS). The "Phytotoxicity Index" decreased to 1.7, highest diversity of spontaneously colonizing plants occurred, and metal accumulation in grasses reduced to values for uncontaminated soils. Based on the first year evaluation, C+CA+SS showed to be an efficient treatment for amendment assisted phytostabilization of the contaminated Overpelt soil.     

Influences of macroalga-derived dissolved organic carbon on the aquatic toxicity of copper and cadmium

In this study, the effect of dissolved organic carbon (DOC) derived from macroalga (Sargassum) on the acute toxicity of copper (Cu) and cadmium (Cd) to a freshwater cladoceran (Daphnia magna) was investigated. Potassium-loaded macroalga was incubated with ultrapure water to extract macroalgal DOC, which was then spiked with the constituents of the Elendt M7 hard water media. The 48 h median lethal concentration of Cu increased linearly with DOC levels but that of Cd was relatively independent of DOC levels (0-44 mg l(-1)). The independence of Cd toxicity on DOC level might be due to the competitive effect of high calcium concentrations in the media with Cd for the binding sites of DOC. The decreased Cu toxicity was a result of reduced Cu uptake as evidenced in a separate accumulation test. Also, the capability of the macroalgal DOC on reducing Cu toxicity was found to be comparable to DOC tested in other studies. Therefore, the present study suggested that the biosorption treatment process using macroalgae should consider the effect of DOC release from the biomass as a step of modifying the metal toxicity as well as influencing metal biosorption capacity.     

Effect of farmyard manure application on boron adsorption-desorption characteristics of some soils

Boron (B) availability to crop plants depends on soil properties as well as management practices like liming, fertilization and use of organic manures. To assess the effect of farmyard manure (FYM) application on availability of added B, adsorption-desorption of B was investigated in five different soils receiving varying doses of FYM (0, 5 and 10 g FYM kg(-1) soil). Two surfaces Freundlich model was found best to account for B adsorption-desorption data of all soils. Application of FYM increased B adsorption capacities pertaining to low (K1) and high (K2) concentration ranges in all soils, except Soil C (Alfisol) having a pH of 9.8, in which the higher rate of FYM decreased the value of K2. Application of FYM did not change B desorption capacities of soils corresponding to low B concentration range (K(1)(1)) significantly, however, it increased B desorption capacity pertaining to high B concentration (K(1)(2)) in all soils, except Soils C (Alfisol) and E (Entisol) having pH of 9.8 and 5.1, respectively. Application of FYM increased the desorption slope factor applicable to low concentration range (1/n(1)(1)) in Soil A (Inceptisol), but decreased it in Soil E (Entisol). The 1/n(1)(2) (desorption slope factor applicable to high concentration range) decreased with FYM application in all soils except Soil E (Entisol), where it was increased. Boron desorption index (slope(ads)/slope(des)) decreased with FYM application in low B concentration range, but increased in high concentration range for all soils except soil E (Entisol, pH 5.1), in which a reverse trend was observed. Application of FYM increased the retention of added B in soils and may help reducing the leaching losses.     

Prediction of particulate loading in exhaust from fabric filter baghouses with one or more failed bags

Loss of filtration efficiency in a fabric filter baghouse is typically caused by bag failure, in one form or another. The degree of such failure can be as minor as a pinhole leak or as major as a fully involved baghouse fire. In some cases, local air pollution regulations or federal hazardous waste laws may require estimation of the total quantity of particulate matter released to the environment as a result of such failures. In this paper, a technique is presented for computing the dust loading in the baghouse exhaust when one or more bags have failed. The algorithm developed is shown to be an improvement over a previously published result, which requires empirical knowledge of the variation in baghouse pressure differential with bag failures. An example calculation is presented for a baghouse equipped with 200 bags. The prediction shows that a small percentage of failed bags can cause a relatively large proportion of the gas flow to bypass the active bags, which, in turn, leads to high outlet dust loading and low overall collection efficiency from the baghouse.     

What determines the current presence or absence of permafrost in the Torneträsk region, a sub-arctic landscape in northern Sweden?

In a warming climate, permafrost is likely to be significantly reduced and eventually disappear from the sub-Arctic region. This will affect people at a range of scales, from locally by slumping of buildings and roads, to globally as melting of permafrost will most likely increase the emissions of the powerful greenhouse gas methane, which will further enhance global warming. In order to predict future changes in permafrost, it is crucial to understand what determines the presence or absence of permafrost under current climate conditions, to assess where permafrost is particularly vulnerable to climate change, and to identify where changes are already occurring. The Tornetr?sk region of northern sub-Arctic Sweden is one area where changes in permafrost have been recorded and where permafrost could be particularly vulnerable to any future climate changes. This paper therefore reviews the various physical, biological, and anthropogenic parameters that determine the presence or absence of permafrost in the Tornetr?sk region under current climate conditions, so that we can gain an understanding of its current vulnerability and potential future responses to climate change. A patchy permafrost distribution as found in the Tornetr?sk region is not random, but a consequence of site-specific factors that control the microclimate and hence the surface and subsurface temperature. It is also a product of past as well as current processes. In sub-Arctic areas such as northern Sweden, it is mainly the physical parameters, e.g., topography, soil type, and climate (in particular snow depth), that determine permafrost distribution. Even though humans have been present in the study area for centuries, their impacts on permafrost distribution can more or less be neglected at the catchment level. Because ongoing climate warming is projected to continue and lead to an increased snow cover, the permafrost in the region will most likely disappear within decades, at least at lower elevations.     

Bagasse-assisted bioremediation of ammonia from shrimp farm wastewater.

Development of new economically feasible ecofriendly products from agricultural wastes or byproducts for shrimp farm wastewater treatment is the objective of our continued research. Ammonia is a nitrogenous toxicant, which is commonly found in wastewater from shrimp farms. In the present study, we explored the possibility of the use of simply and inexpensively prepared bagasse products so that this abundant crop byproduct could be used to remove ammonia from shrimp farm wastewater. Bagasse, a natural highly fibrous lignocellulosic byproduct of sugarcane, was converted into five different products. Experimental results have shown that ammonia is efficiently removed from wastewater by four bagasse products with a dose of 1 to 6 g/L within 24 hours. The effect of bagasse products on other water quality parameters and growth kinetics of biofilm bacteria onto bagasse fiber have also been studied. Efficacies of products were compared by using statistical analysis. Products developed from bagasse are useful and economical.     

Modelling the extra and intracellular uptake and discharge of heavy metals in Fontinalis antipyretica transplanted along a heavy metal and pH contamination gradient

Samples of the aquatic bryophyte Fontinalis antipyretica Hedw. were transplanted to different sites with the aim of characterizing the kinetics of the uptake and discharge of heavy metals in the extra and intracellular compartments. The accumulation of metals in extracellular compartments, characterized by an initial rapid accumulation, then a gradual slowing down over time, fitted perfectly to a Michaelis-Menten model. The discharge of metals from the same compartment followed an inverse linear model or an inverse Michaelis-Menten model, depending on the metal. In intracellular sites both uptake and discharge occurred more slowly and progressively, following a linear model. We also observed that the acidity of the environment greatly affected metal accumulation in extracellular sites, even when the metals were present at relatively high concentrations, whereas the uptake of metals within cells was much less affected by pH.