Moroccan actinobacteria with promising activity against toxic cyanobacteria Microcystis aeruginosa

Environmental Science and Pollution Research - In recent decades, harmful cyanobacterial blooms (HCBs) have become a severe hazard for human health mainly in drinking water resources and are...     

Fishing sustainability via inclusion of man in predator-prey models: A case study in Lago Preto, Manacapuru, Amazonas

We modeled a fishery's system with two types of fishermen, commercial and subsistence fishermen, who exploit the fish stock at the Amazonian floodplain lakes. In the first model, we combined the Lotka-Volterra equations with Verhulst's Logistic model, by inserting hydrological cycle oscillations. The second model was based on the equations proposed by Berryman, which reflect the predator's functional response in relation to the prey's population behavior, taking into account the hydrological cycle. In both models, commercial fishermen and local direct consumers (called riverside dwellers - riverines - in the model), were considered the only predators acting upon fishing stocks. Primary data were collected in 48 riverside homes throughout 2006. The total number of interviewees corresponds to 69.6% of the universe of homes in the community defined as study area. The riverines were the predators that showed capacity to eliminate the opponent predators (commercial fishermen). The best scenery obtained regarding the number of prey, was the one that showed only commercial fishermen in the region. On the other hand, the simulations show that the coexistence is possible among predators, and between predators and their prey. The seasonal model with functional response provides a better response in relation to the system's current situation and to the established modeling conditions than the Lotka-Volterra seasonal model. The seasonal model with functional response also showed a better response pattern in all scenarios, with oscillations taking place more gradually, both for variations associated with the flooding pulse and for relations between predators and prey.     

Separation of packaging plastics by froth flotation in a continuous pilot plant

The objective of the research was to apply froth flotation to separate post-consumer PET (Polyethylene Terephthalate) from other packaging plastics with similar density, in a continuously operated pilot plant. A representative sample composed of 85% PET, 2.5% PVC (Polyvinyl Chloride) and 11.9% PS (Polystyrene) was subjected to a combination of alkaline treatment and surfactant adsorption followed by froth flotation. A mineral processing pilot plant, owned by a Portuguese mining company, was adapted for this purpose. The experimentation showed that it is possible to produce an almost pure concentrate of PET, containing 83% of the PET in feed, in a single bank of mechanical flotation cells. The concentrate grade attained was 97.2% PET, 1.1% PVC and 1.1% PS. By simulation it was shown that the Portuguese recycling industry specifications can be attained if one cleaning and one scavenger stages are added to the circuit.     

Effects of widely used pharmaceuticals and a detergent on oxidative stress biomarkers of the crustacean Artemia parthenogenetica

Pharmaceuticals are continuously dispersed into the environment as a result of human and veterinary use, posing relevant environmental concerns. The present paper reports the acute toxic effects of three therapeutic agents (diazepam, clofibrate and clofibric acid) and a detergent, sodium dodecylsulphate (SDS), to the hypersaline crustacean Artemia parthenogenetica. This study specially focused on oxidative stress parameters, namely (1) total and selenium-dependent glutathione-peroxidase (GPx), (2) glutathione reductase (GRed), (3) total superoxide dismutase (SOD), and (4) glutathione-S-transferases (GSTs). The effects of tested substances on lipid peroxidation (thiobarbituric acid reactive substances, TBARS), and soluble cholinesterases (ChE) were also investigated. Diazepam caused a significant inhibition of ChE (LOEC = 7.04 mg/l) and total GPx activities. SDS was responsible for a decrease in the activity of both ChE (LOEC = 8.46 mg/l) and GRed (LOEC = 4.08 mg/l). Both fibrates (clofibrate and clofibric acid) were responsible for significant decreases in Se-dependent GPx, with LOEC values of 176.34 and 3.09 mg/l, respectively. Clofibrate also caused a slight increase of TBARS content of A. parthenogenetica homogenates. These results indicate that the exposure to all the tested compounds induced alterations on the cellular redox status in A. parthenogenetica. In addition, diazepam was shown to have the capability of interfering with A. parthenogenetica neurotransmission, through the inhibition of ChE.     

Model development and application for surfactant biodegradation in an acclimatising activated sludge system

A model for the biodegradation of non-ionic surfactants in an activated sludge system during acclimatisation was developed, based on respirometric and titrimetric experimental data. The data were obtained in a sequencing batch reactor (SBR) using a non-ionic surfactant as sole carbon source and sludge previously acclimatised to a different surfactant. The model was successfully applied to successive SBR-cycles of sludge acclimatisation processes subjected to two ethoxylated surfactants. The model was validated using the corresponding total organic carbon data. The evolution of the model parameters along the acclimatisation process was examined. An acclimatisation model was developed using the evolution of two of these parameters (affinity constant and inhibition constant), supported by two independently calculated acclimatisation indicators. This acclimatisation model was then applied to determine an optimal surfactant concentration sequence to feed non-acclimatised sludge during a period of 41 days, in order to induce pre-acclimatisation to this surfactant before it replaces another one in the wastewater. The model was also useful in the economical assessment of this and alternative procedures to cope with frequent changes in activated sludge feed composition.     

(210)Pb content in natural gas pipeline residues ("black-powder") and its correlation with the chemical composition

The present work was carried out to assess the (210)Pb content in "black-powder" found in pigging operations on gas pipelines in Brazil, in particular, on the Campos Basin gas pipeline. Additionally, the chemical composition of such deposits was determined and an eventual correlation with (210)Pb concentration evaluated. Typical "black-powder" generated in the natural gas pipeline from Campos Basin oilfield contains mainly iron oxide ( approximately 81%) and residual organic matter ( approximately 9%). The (210)Pb content ranges from 4.9 to 0.04k Bqkg(-1) and seems to be inversely correlated with the distance to the platforms. On the other hand, (226)Ra concentration is higher on the pipeline branch between the platform and the onshore installations. (228)Ra was only observed in few samples, in particular, in the samples with the highest (226)Ra content.     

Temporal stability of genetic population structure in the New Zealand snapper, <Emphasis Type="Italic">Pagrus auratus</Emphasis>, and relationship to coastal currents

Genetic diversity and population structure of snapper (Pagrus auratus, Bloch and Schneider), a coastal demersal sparid fish, were determined using six nuclear microsatellite loci and SSCP (single strand conformational polymorphism) analysis of themitochondrial (mt) DNA D-loop in samples collected across the range of the species in New Zealand. Microsatellite data showed similar results to allozyme data collected in the late 1970s that found differentiation between the north-east and southern populations. In addition, an isolated population of snapper in Tasman Bay was identified. The two data sets provide evidence for the temporal stability of the genetic population structure of snapper over 22 years, with differentiation over relatively small spatial scales separated by oceanographic boundaries rather than isolation by distance. In contrast to nuclear markers, mtDNA did not reveal any significant genetic heterogeneity among samples.     

210Po concentration in Perna perna mussels: looking for radiation effects

Twenty ropes with 400 Perna perna mussels seeds (3 cm shell size) were set-up on floating structures at Cabo Frio Island, Arraial do Cabo, approximately 100 km northeast of Rio de Janeiro city. A rope was taken out on a monthly basis, and the shell sizes of 100 seeds were measured. The haemolymph of 10 male and 10 female individuals was taken, and the same individuals were separated for 210Po/210Pb determination. After one year of monthly sampling, no clear correlation was observed between the 210Po concentration, mussel's age and weight. A mean 210Po concentration of 155 Bq kg(-1) wet weight basis, was obtained, which is comparable with data reported in the literature. The radiation dose did not have any observable effect on the micronuclei frequency and DNA breaks in the mussels. This was probably due to the low dose rate, 0.02 mGy d(-1), in comparison with the suggested potential dose limit of 10 mGy d(-1).     

Toxaphene residues from cotton fields in soils and in the coastal environment of Nicaragua

Toxaphene (camphechlor) was intensively used in the cotton growing fields of Nicaragua for decades with application rates as high as 31 kg ha(-1) in 1985. Although the use of this compound has recently been discontinued in the country, its intensive use in the past and its long persistence in soil allowed for the build up of large reservoirs of toxaphene in agriculture soils and a wide dispersal of residues in the environment. Measurements of toxaphene in coastal areas on the coast of the Pacific Ocean show that environmental concentrations are particularly high in the district of Chinandega, the traditional cotton growing region. Toxaphene residues measured in soils attained 44 microg g(-1) (dry weight) while concentrations in lagoon sediments attained 6.9 microg g(-1) (dry weight) near the mouth of the rivers flowing across the agricultural region. Measurements in aquatic biota showed concentrations as high as 1.6 microg g(-1) (dry weight) in the soft tissues of clams. The toxaphene reservoir in soils combined with the obvious persistence of this compound in soils and lagoon sediments allows predicting that toxaphene will remain in the coastal ecosystem at relatively high concentrations for many years. Toxic effects in lagoon fauna are likely to be observed especially in benthic species that may recycle this compound from sediments. Consumption of seafood, in particular of clams (Anadara spp.) from the more contaminated areas, may expose the population to unacceptably high intake of toxaphene, 30 microg d(-1) per person, with the diet.