The proton binding properties of biosorbents

Environmental Chemistry Letters - A broad variety of materials of biological origin have been successfully used in recent decades for the removal of pollutants from waters. These biosorbents...     

Risk level of chemical cues determines retention of recognition of new predators in Iberian green frog tadpoles

In aquatic environments, many prey rely on chemosensory information from injured (alarm cues) or stressed conspecifics (disturbance cues) to assess predation risk. Alarm cues are considered as a sign of higher risk than disturbance cues. These cues could be used by prey to learn potential new predators. In this study, we tested whether Iberian green frog tadpoles (Pelophylax perezi) exhibited antipredator responses to alarm and disturbance cues of conspecifics and whether tadpoles could associate new predators with alarm or disturbance cues. Tadpoles reduced their activity in the presence of disturbance cues, but only weakly when compared with their response to alarm cues. Also, tadpoles learned to recognize new predators from association with alarm or disturbance cues. However, the period of retention of the learned association was shorter for disturbance than alarm cues. Our results indicate that tadpoles are able to modify their antipredatory behavior according to (1) the degree of risk implied by the experimental cues (2) their previous experience of chemical cues of the predator.     

Effect of organic carbon and metal accumulation on the bacterial communities in sulphidogenic sediments

A unique geochemical setting in Lake Cadagno, Switzerland, has led to the accumulation of insoluble metal sulphides in the sedimentary record as the result of past airborne pollution. This offers an exceptional opportunity to study the effect of these metals on the bacterial communities in sediments, and in particular to investigate further the link between metal contamination and an increase in the populations of endospore-forming bacteria observed previously in other metal-contaminated sediments. A decrease in organic carbon and total bacterial counts was correlated with an increase in the numbers of endospores in the oldest sediment samples, showing the first environmental evidence of a decrease in nutrient availability as a trigger of sporulation. Proteobacteria and Firmicutes were the two dominant bacterial phyla throughout the sediment, the former in an area with high sulphidogenic activity, and the latter in the oldest samples. Even though the dominant Firmicutes taxa were stable along the sediment core and did not vary with changes in metal contamination, the prevalence of some molecular species like Clostridium sp. was positively correlated with metal sulphide concentration. However, this cannot be generalized to all endospore-forming species. Overall, the community composition supports the hypothesis of sporulation as the main mechanism explaining the dominance of endospore formers in the deepest part of the sediment core, while metal contamination in the form of insoluble metal sulphide deposits appears not to be linked with sporulation as a mechanism of metal tolerance in this sulphidogenic ecosystem.     

Fog as a Fresh-Water Resource: Overview and Perspectives

The collection of fog water is a simple and sustainable technology to obtain fresh water for afforestation, gardening, and as a drinking water source for human and animal consumption. In regions where fresh water is sparse and fog frequently occurs, it is feasible to set up a passive mesh system for fog water collection. The mesh is directly exposed to the atmosphere, and the foggy air is pushed through the mesh by the wind. Fog droplets are deposited on the mesh, combine to form larger droplets, and run down passing into a storage tank. Fog water collection rates vary dramatically from site to site but yearly averages from 3 to 10 l m⁻² of mesh per day are typical of operational projects. The scope of this article is to review fog collection projects worldwide, to analyze factors of success, and to evaluate the prospects of this technology.     

Oxidative stress, cytoxicity, and cell mortality induced by nano-sized lead in aqueous suspensions

This paper reports on the effect of aqueous and nano-particulated Pb on oxidative stress (lipid peroxidation), cytoxicity, and cell mortality. As determined by the Thiobarbituric Acid Reactive Substances (TBARS) method, only 6 h after incubation aqueous suspensions bearing nano-sized PbO₂, soluble Pb(II), and brain-homogenate only suspensions, were determined to contain as much as ca. 7, 5, and 1 nmol TBARS mg protein⁻¹, respectively. Exposure of human cells (central nervous system, prostate, leukemia, colon, breast, lung cells) to nano-PbO₂ led to cell-growth inhibition values (%) ca. ≤18.7%. Finally, as estimated by the Artemia salina test, cell mortality values were found to show high-survival larvae rates. Microscopic observations revealed that Pb particles were swallowed, but caused no mortality, however.     

Reduction of the movement and persistence of pesticides in soil through common agronomic practices

Laboratory and field studies were conducted in order to determine the leaching potential of eight pesticides commonly used during pepper cultivation by use of disturbed soil columns and field lysimeters, respectively. Two soils with different organic matter content (soils A and B) were used. Additionally, soil B was amended with compost (sheep manure). The tested compounds were cypermethrin, chlorpyrifos-methyl, bifenthrin, chlorpyrifos, cyfluthrin, endosulfan, malathion and tolclofos-methyl. In soil B (lower organic matter content), only endosulfan sulphate, malathion and tolclofos-methyl were found in leachates. For the soil A (higher organic matter content) and amended soil B, pesticide residues were not found in the leachates. In addition, this paper reports on the use of common agronomic practices (solarization and biosolarization) to enhance degradation of these pesticides from polluted soil A. The results showed that both solarization and biosolarization enhanced the degradation rates of endosulfan, bifenthrin and tolclofos-methyl compared with the control. Most of the studied pesticides showed similar behavior under solarization and biosolarization conditions. However, chlorpyrifos was degraded to a greater extent in the solarization than in biosolarization treatment. The results obtained point to the interest in the use of organic amendment in reducing the pollution of groundwater by pesticide drainage and in the use of solarization and biosolarization in reducing the persistence of pesticides in soil.     

Polychlorinated biphenyls in farmed and wild <Emphasis Type="Italic">Onchorhynchus kisutch</Emphasis> and <Emphasis Type="Italic">Onchorhynchus mykiss</Emphasis> from the Chilean Patagonia

Purpose  

This paper analyses the presence of polychlorinated biphenyls (PCBs) in escaped: farmed and wild salmons in southern Chile, analysing their concentrations and congener profiles in two species (Oncorhynchus kisutch and Oncorhynchus mykiss).     

Night-time atmospheric chemistry of methacrylates

Background, aim, and scope  

Methacrylates are α, β-unsaturated esters that are widely used in the polymer plastics and resins production. Kinetic information of NO₃ radical reactions is especially scarce and a good understanding of all the atmospheric oxidation processes of these compounds is necessary in order to determine lifetimes in the atmosphere and to evaluate the impact of these reactions on the formation of ozone and other photooxidants.     

Study of fractionation and potential mobility of metal in sludge from pyrite mining and affected river sediments: changes in mobility over time and use of artificial ageing as a tool in environmental impact assessment

Sludge from mining exploitation can be a source of land and water contamination in the adjacent zone. Accidents such as the break of waste mining pools in the Aznalcollar Mine (Seville, Spain) in 1998 produce important ecological disasters. In this work is presented a study of the evolution of aqua regia leachable concentration and mobility of metals in sediment samples of Guadiamar River basin from the accident date up to 2001. The application of BCR standard extraction procedures provides valuable information about the mobility and toxicity of the spill and the metal mobility in Guadiamar River polluted sediments. As a rule, themobility of several metals in the initial sludge (sulphides) is low, except for copper. Otherwise, the results of aqua regia leachable concentration and mobility of metal obtained for sediments samples indicate that the cleaning and inertisation works carried out in the zone have been adequate but insufficient, being the metal levels observed in the zone are higher than natural levels. To establish the initial impact of the spill and the mobility changes with time, mineralogical composition of the pyritic sludge and its evolution after the natural weathering and after the induction, of accelerated ageing processes by light and temperature was studied in the laboratory. Oxidation of initial sulphides to sulphates was observed. Both environmental and laboratory oxidation of the metallic sulphides increase the mobility of all metals, especially of copper, zinc and lead. The proposed laboratory procedure allows to predict the changes in mobility and therefore in toxicity that can occur at short or long term after exposure of sludge at environ-mental conditions. The mobility results in sludge and sediment samples are interpreted in terms of the mineral composition of the samples.