Phytotoxicity,cytotoxicity, and in vivo antifungal efficacy of chitosan nanobiocomposites on prokaryotic and eukaryotic cells

Environmental Science and Pollution Research - Chitosan (CS) nanosystems have potential applications for the control of microorganisms in the medical, environmental, and agrifood fields. In vivo...     

Density dependence and habitat quality modulate the intensity of display territory defence in an exploded lekking species

We evaluated the effect of conspecific abundance and habitat quality of leks on the territorial behaviour of males in an exploded lekking species, the Little Bustard (Tetrax tetrax). The hypothesis that males more intensely defend territories with higher conspecific abundance and better habitat quality was evaluated experimentally analysing the agonistic response of experimental males to male decoys placed on their displaying areas. Decoy experiments showed that the intensity of display territory defence by little bustard males is density dependent. The time experimental males took to return to their display sites after decoy placement decreased with abundance of both males and females. The strength of their final response was positively associated to local male and female abundance in the vicinity of their display sites. Habitat quality also influenced males’ display territory defence since the intensity of male response increased with the degree of natural vegetation cover. Habitat quality was particularly relevant in explaining variation of experimental males’ snort call rate, which decreased with the degree in plough cover and increased with the number of fields in the lekking area. Snort call rate decreased with the level of male aggregation and was lowest in males exhibiting the strongest aggressive response to decoys. These results add new evidence for the density dependence of species’ breeding territorial behaviour, supporting density-dependent models of lek formation and reinforcing the role of resources defence in exploded lek mating systems.     

Influence of organic solvents on the sensitivity of a bioluminescence toxicity test with Vibrio harveyi

The possibility of using organic solvents (OSs) to increase the susceptibility of bioluminescent microorganisms in a bioassay for assessing the toxicity of chemicals dissolved in water was investigated. To conduct the tests acetonitrile, dimethyl sulfoxide, ethanol, methanol, and isopropanol were used as OSs and Cd, Hg, and Zn as reference toxicants. The addition of OSs modified the toxicity of the three metals to Vibrio harveyi, according on the bioluminescence assay used. The sensitivity of the luminescence bioassay for Hg increased in the presence of the five OSs, thus indicating a greater toxic effect. However, the sensitivity of the assay for the other two metals, Cd and Zn, increased or decreased (lesser toxic effect) depending on the concentration at which the OSs were used. No correlation was observed between the concentration of the five OSs and the toxicity of the three reference toxicants. From this it can be deduced that none of these OSs could be recommended for increasing generically the sensitivity of toxicity biotests using V. harveyi.     

Inhibition of sulfide generation in a reclaimed wastewater pipe by nitrate dosage and denitrification kinetics.

Sulfide generation should be avoided during wastewater transportation. The efficiency of nitrate dosing for the inhibition of sulfide generation was evaluated during reclaimed wastewater transport with two nitrate doses, 2.5 and 5 mg/L nitrate-nitrogen (NO3-N). A calcium nitrate [Ca(NO3)2] solution was injected at the beginning of the 61-km-long gravity pipe, which is part of the Reclaimed Wastewater Reuse System of South Tenerife (Spain). During transportation, after dissolved oxygen depletion, a denitrification process took place. With the 5 mg/L NO3-N dose, nitrate was not completely removed at the end of the pipe, whereas with 2.5 mg/L NO3-N, a complete denitrification was achieved. Sulfide generation was completely inhibited with the 5 mg/L dose. However, with 2.5 mg/L, sulfide generation was not completely inhibited but delayed and minimized to a great extent. Denitrification was stoichiometrically limited by the availability in biodegradable matter. An empirical equation enables one to predict the nitrate concentration.     

The small-scale water provider in Paraguay: bringing private sector efficiency to water resource use and the provision of drinking water to the poor

This article provides a case study of small-scale private sector provision of water supply in Paraguay, where the Government has sought sector policy reforms that would encourage private investment in drinking water supply. Ironically, while the Government has focused almost entirely on garnering the interest of large private international water companies, much smaller local firms have already made significant investments in drinking water services for the poor, all without any participation or encouragement from the Government. Outside Paraguay's two major cities, Asunción and Ciudad del Este, large numbers of aguateros currently provide piped potable water to lower-income people. Though the aguateros have little legal footing — they are in many respects informal and unregulated —they have constructed as much as one third of all the new drinking water connections in these two cities over the past 20 years. The small-scale water systems in Paraguay offer a model of financial, economic, and water-use efficiency. This article asserts that an abundance of groundwater resources, cheap access to electricity for pumping, and a spirit of informal investment, among other variables, has spawned widespread use of this approach. This article documents and analyzes the features of these independent small-scale water providers in Paraguay and the efficiency they bring to the use of water resources in meeting drinking water demands among the poor. It also cautions against policies that may trample on such entrepreneurial spirit in the name of State-managed privatization.     

Indirect assessment of economic damages from the Prestige oil spill: consequences for liability and risk prevention

The social losses arising from the Prestige oil spill exceed the compensation granted under the IOPC (International Oil Pollution Compensation) system, with losses estimated at 15 times more than the applicable limit of compensations. This is far above the level of costs for which those responsible for hydrocarbons spills are liable. The highest market losses correspond to sectors of extraction, elaboration and commercialisation of seafood. However, damages to non-commercial natural resources could constitute an outstanding group of losses for which further primary data are needed: these losses would only be compensable under the current system by means of a refund for cleaning and restoration costs. Results show that, in Europe, the responsibility for oil spills in maritime transport is limited and unclear. The consequence of this is net social losses from recurrent oil spills and internationally accepted incentives for risky strategies in the marine transport of hydrocarbons.     

Mercury removal using ground and calcined mussel shell

We determined mercury retention on calcined and ground mussel shell, in presence and absence of phosphate, using batch and stirred flow chamber experiments. In batch experiments the calcined shell exhibited higher Hg adsorption, with good fitting to Freundlich equation （R^2： 0.925-0.978）; the presence of phosphate increased Hg adsorption; mercury desorption was 13% or lower, diminishing up to 2% under the presence of phosphates. In stirred flow chamber experiments calcined shell retained more Hg than ground shells （6300 vs. 4000-5200 μmol/kg）; Hg retention increased an additional 40% on calcined shell and up to an additional 70% on ground shells when phosphates were present; mercury desorption was quite similar in all shell types （20%-34%）, increasing up to 49%-60% in ground shells when phosphates were present. The higher Hg adsorption on calcined shell would be related to its calcite and dolomite concentrations; mercury-phosphate interactions would cause the increase in Hg retention when phosphates are present. Data on Hg desorption suggest that Hg retention was not easily reversible after batch experiments, increasing in the stirred flow chamber due to convective flow. Calcined and ground mussel shells could be recycled removing Hg from water, with the presence of phosphates in solution improving efficacy.     

Photodegradation of Diquat and Paraquat in aqueous solutions by titanium dioxide: evolution of degradation reactions and characterisation of intermediates

The titanium dioxide assisted photodegradation of Diquat and Paraquat herbicides solutions has been the subject of the present investigation, considering its direct application in the treatment of contaminated waters and soils. To have a better understanding of the photodegradation process, different types of TiO2, commercial and 'home prepared' Ti(1-x)FexO2 (x = 0% and 4%), were used as catalysts, using an UV light as radiation source. The degradation reactions were followed by UV spectroscopy and the intermediates and reaction products were characterised by electrospray ionisation mass spectrometry (ESIMS) combined with collision-induced dissociation (CID) and tandem mass spectrometry (MS/MS). The present study shows that, for photocatalytic degradation of Diquat and Paraquat solutions, a basic pH can be determinant, as well as the type of catalyst. The type of catalyst can also strongly influence the degradation pattern of the herbicide. Regarding complete degradation, we were able to show that Diquat is more persistent than Paraquat. During the photocatalytic processes, several intermediate and reaction products are sequentially formed, to which structures are proposed.