Modelling of the life cycle of Chironomus species using an energy-based model

Little is known about the differences between the species of the genus Chironomus relatively to their life cycle strategies. This knowledge is however crucial to fully understand the response of the Chironomus community to field perturbations. Here, we proposed to study four Chironomus species by using an energy-based model to describe growth, emergence and reproduction. We used data from the literature for two species (Chironomus plumosus and Chironomus tentans) and data from our experiments for two other species (Chironomus prasinus and Chironomus riparius). We showed that our model is able to accurately describe the life-history attributes for all the species tested, which suggests that Chironomus species have the same fundamental characteristics (low maintenance energetic costs, isomorphism), which makes possible the building of a common modelling framework to assess effects of toxicants at individual and population level. The species showed a few differences relatively to the parameters of the models with possible consequences when assessing effects of chemicals on Chironomus community. For instance, due to differences in growth parameters, C. riparius population dynamics should be more sensitive to effects on individual growth than C. prasinus or C. plumosus ones.     

A case study of molinate application in a Portuguese rice field: herbicide dissipation and proposal of a clean-up methodology

This study was designed to monitor molinate losses in surface and underground waters during Ordram application in a rice field situated in central Portugal. Water samples were collected from different sites, before, during and about one month and a half after Ordram application. Molinate quantification was based on a solid-phase microextraction (SPME) method followed by gas chromatography with flame photometric detector (GC-FPD) analysis, and led to the conclusion that the herbicide was dissipated in the environment, reaching levels as high as 3.9 microgl(-1) in underground water and 15.8 microgl(-1) in the river receiving tail waters. The feasibility of the application of treatment methodologies based on adsorption or biodegradation as processes to remove molinate from real-world waters was assessed. These methods seem suitable to reduce molinate concentrations to values in the range of the legally recommended limits (<0.5 microgl(-1)).     

Inclusion complexes of alpha- and gamma-cyclodextrins and the herbicide norflurazon: I. Preparation and characterisation. II. Enhanced solubilisation and removal from soils

The interaction of norflurazon with alpha- and gamma-cyclodextrins (CDs) yielded the formation of inclusion complexes at a 1:1 stoichiometric ratio in solution and in the solid state. Apparent stability constants of 50.7+/-1.6 and 37+/-1.7 M(-1) and an increase in herbicide solubility by up to five and fourfold for alpha- and gamma-CD, respectively, were determined from the phase solubility diagrams at 25 degrees C in water. Three processing methods (kneading, spray-drying and vacuum evaporation) were used to prepare norflurazon-CD solid inclusion complexes, which were characterised by infrared spectroscopy, differential scanning calorimetry and scanning electron microscopy. A high increase in the norflurazon dissolution rate was obtained with all the solid complexes with gamma-CD, but when alpha-CD was used, only the solid system obtained after the vacuum evaporation process showed a higher dissolution rate. This finding is a first step in the development of new, environmentally sound formulations of norflurazon (NFL), due to the capacity for increasing its dissolution rate and hydrosolubility, and thus diminishing the use of organic solvents. On the other hand, the effect of alpha- and gamma-cyclodextrin on the solubility of norflurazon in solution was also considered as a way of modifying its behaviour in the soil environment. Desorption studies of NFL from soils in the presence of alpha- and gamma-cyclodextrin were carried out using a batch equilibration method. The results obtained showed that alpha- and gamma-cyclodextrin greatly increased the removal of norflurazon previously adsorbed, proving the potential use of these CDs for in situ remediation of pesticide-contaminated soils.     

Efficient use of Fe metal as an electron transfer agent in a heterogeneous Fenton system based on Fe0/Fe3O4 composites

In this work a novel heterogeneous Fenton system based on Fe(0)/Fe3O4 composites is described. The composites with several Fe(0)/Fe3O4 ratios were prepared by two different methods, i.e. mechanical alloying of Fe(0) and Fe3O4 powders and controlled reduction of Fe3O4 with H2. Reaction studies and detailed Conversion Electron M?ssbauer surface characterization of the composites Fe(0)/Fe3O4, Fe(0), Fe3O4, alpha-Fe2O3 and gamma-Fe2O3 suggested that Fe2+surf species are essential to produce an active Fenton system. Kinetic studies for the oxidation of the dye methylene blue, used as an organic model molecule, and for the peroxide decomposition suggest that the reactions proceed via HO* radicals generated from Fe2+surf species and H2O2 in a Fenton like mechanism. The increase in activity caused by the addition of Fe(0) is discussed in terms of a creation of Fe2+surf species during the preparation of the composite and by an electron transfer mechanism from Fe(0) to Fe3+surf during the Fenton reaction to regenerate the Fe2+surf active species.     

Use of the aquatic lichen Dermatocarpon luridum as bioindicator of copper pollution: accumulation and cellular distribution tests

Laboratory experiments were conducted to investigate the potential use of the aquatic lichen Dermatocarpon luridum as bioindicator of copper pollution. Lichen thalli were exposed to 0.00, 0.25, 0.50, 0.75 and 1.00 mM copper in synthetic freshwater to solve the problems of metal bioavailability. The mineral composition of this media was prepared so that it corresponded to the ion composition of natural waters in D. luridum ecosystems. Sequential elution procedures using NiCl2 or Na2-EDTA (20 mM) were used to determine the distribution of metals at different cellular sites. The copper concentration extracted from thalli was correlated with pollution intensity, the greater correlation being with the Na2-EDTA extractant. The malondialdehyde concentration in thalli can be used as indicator of copper pollution; however, similar membrane degradation was observed for 0.25 and 0.50 mM copper and for 0.75 and 1.00 mM copper.     

Modeling the Entrepe?as Reservoir.

The Entrepe?as Reservoir is a monomictic reservoir located in River Tagus (Spain). The aim of this work is to establish a feasible model to predict the depth of the thermocline that is developed in the reservoir during the period of natural thermal stratification. Entrainment, eddy diffusion, inflow of external energy, and other factors are considered to calibrate the parameters of the model. The methodology involves the measure of actual temperature and electrical conductivity profiles, use of meteorological data and reservoir parameters, and selection and application of several models from the literature. The calculations and predictions are integrated to a software packet that is able to predict thermocline depth and water temperature profile during a 1-year period on a day-by-day basis. In the thermocline depth, the prediction error, on the basis of real data, is less than 6% and, in the water temperature, it is 2 degrees C.     

Antifungal and anti-aflatoxigenic activity of Heliopsis longipes roots and affinin/spilanthol against Aspergillus parasiticus by downregulating the expression of alfD and aflR genes of the aflatoxins biosynthetic pathway

Abstract

In the present study, ethanolic extract from Heliopsis longipes roots and affinin/spilanthol against Aspergillus parasiticus growth and aflatoxins production were studied in relation to the expression of aflD and aflR, two key genes of aflatoxins biosynthetic pathway. Phytochemical analysis of the ethanolic extract by GC-EIMS identified affinin/spilanthol (7.84?±?0.27?mg g^?1) as the most abundant compounds in H. longipes roots. The antifungal and anti-aflatoxigenic assays showed that affinin/spilanthol at 300?µg mL^?1 produced the higher inhibition of radial growth (95%), as well as, the higher aflatoxins production inhibition (61%) in comparison to H. longipes roots (87% and 48%, respectively). qRT-PCR revealed that the expression of aflD and aflR genes showed a higher downregulation in affinin/spilanthol at 300?µg mL^?1. The expression ratio of alfD was suppressed by affinin/spilanthol in 79% and aflR in 84%, while, a lower expression ratio suppressed by H. longipes was obtained, alfD (55%) and aflR (59%). Affinin/spilanthol possesses higher antifungal and anti-aflatoxigenic activity against A. parasiticus rather than H. longipes roots, and this anti-aflaxotigenic activity occurring via downregulation of the aflD and aflR genes. Thus, H. longipes roots and affinin/spilanthol can be considered potent antifungal agents against aflatoxigenic fungus, especially, affinin/spilanthol.     

The economic benefits of fulfilling the World Health Organization’s limits for particulates: A case study in Algeciras Bay (Spain)

Algeciras Bay is an important industrial and port zone in the south of Spain whose pollution by particulate matter surpasses the threshold levels recommended by the World Health Organization (WHO) in its 2005 Guide on Air Quality. This study analyses the mortality avoided and the economic benefit which would be derived from a reduction of the pollution of PM2.5 and PM10 to the levels recommended by the WHO in Algeciras Bay in the period 2005-2015. The analysis carried out shows that the industrial zones, such as Los Barrios and San Roque, are those which have greater levels of pollution and in which the relative risk is greater. The calculations for Algeciras Bay between 2000 and 2015 show 182 deaths which would be avoided if the particulate matter pollution were reduced to the levels recommended by the WHO. Likewise, the economic valuation which this impact has on health is carried out through two concepts: the cost of illness and the Value of Statistical Life (VSL). The result shows that the economic benefit that would come out with the cost of illness valuation is 5,329,110€ and from the VSL is 414,787,113€.

Implications: PM_2.5 has a greater concentration in industrial localities and is linked to the industrial activity. When the particulate matter pollution is reduced to the levels recommended by the WHO in an industrialised area such as Algeciras (Spain), 182 deaths which would be avoided. The result shows that the economic benefit that would come out with the cost of illness valuation is 5,329,110€ and from the value of statistical life is 414,787,113€.     

Plasma ALP activity and blood PCV value changes in chick fetuses due to exposure of the egg to different xenobiotics

The effects of two polycyclic aromatic hydrocarbon (PAH) compounds (benz(k)fluoranthene and fluoranthene) and two heavy metals (cadmium and lead) were studied on the alkaline phosphatase (ALP) enzyme activity and hematocrit (PCV) values in chick fetuses. Eggs were exposed to one of the four compounds before incubation, by applying two exposure methods: injection (into the air cell) or immersion. Fluoranthene, cadmium and lead injection significantly decreased ALP activity compared to the control, while none of the compounds caused significant reduction in ALP activity in the immersion groups; however, a decreasing tendency was seen in these groups as well. Hematocrit values were increased after benz(k)fluoranthene immersion, fluoranthene immersion and cadmium injection. However, the doses in this study are relatively low (compared to other ecotoxicological studies in birds), the alteration in ALP enzyme activity and PCV values was apparent in each treatment group and is indicative of the high sensitivity of chick fetuses.     

Chemical and bacterial changes during laboratory conditioning of formulated and natural sediments

Within the framework of toxicity testing using formulated sediment, a conditioning treatment prior to toxic contamination has been examined. This preliminary step enables the bacterial colonisation of the sediment, the initiation of organic matter degradation, and the establishment of stable biological and physico-chemical conditions. The treatment involved in keeping the formulated sediment under water in conditions similar to that chosen for toxicity tests. The behaviour of a formulated sediment was compared with a natural sediment. The monitoring of physico-chemical and biological parameters of sediment and water column was carried out over a 30-day incubation in two laboratories. The parameters of pH and redox, dissolved organic carbon (DOC), NH4 and NO2, total organic carbon (TOC) were measured. The bacterial community was characterised by the determination of bacterial density, in total bacteria number or colony forming units (CFU), several exoenzymatic activities (P-glucosidase, xylosidase, leucine-amino-peptidase phosphatase and sulfatase activities), and three gas productions (CO2, N2O and CH4). The same experiment was carried out with a natural sediment. A 10- to 15-day conditioning allowed a physico-chemical stabilisation and corresponded to kinetic changes in hydrolysis activities. As compared to data of the natural sediment, the biological activity of the formulated sediment showed a different dynamic with lower activity levels. For both sediments, an important decrease of activities levels was observed after 15 days because of a substrate limitation. The work showed that a preliminary conditioning treatment of a formulated sediment provides the stabilisation of parameters that can affect toxicant bioavailability. Additional research is needed to determine the real influence of conditioning on the bioavailability of contaminants. The possible advisability of organic matter input, to maintain the sediment bacterial activity, has to be studied.