Concentrations,bioaccumulation, and health risk assessments of heavy metals in fishes from Nigeria’s freshwater: a general overview

Environmental Science and Pollution Research - Heavy metals (HMs) have attracted global attention due to their toxicity, persistence, and accumulation in aquatic fish in the polluted water...     

Modelling radionuclide transport for time varying flow in a channel network

Water flowrates and flow directions may change over time in the subsurface for a number of reasons. In fractured rocks flow takes place in channels within fractures. Solutes are carried by the advective flow. In addition, solutes may diffuse in and out of stagnant waters in the rock matrix and other stagnant water regions. Sorbing species may sorb on fracture surfaces and on the micropore surfaces in the rock matrix. We present a method by which solute particles can be traced in flowing water undergoing changes in flowrate and direction in a complex channel network where the solutes can also interact with the rock by diffusion in the rock matrix. The novelty of this paper is handling of diffusion in the rock matrix under transient flow conditions. The diffusive processes are stochastic and it is not possible to follow a particle deterministically. The method therefore utilises the properties of a probability distribution function for a tracer moving in a fracture where matrix diffusion is active. The method is incorporated in a three dimensional channel network model. Particle tracking is used to trace out a multitude of flowpaths, each of which consists of a large number of channels within fractures. Along each channel the aperture and velocity as well as the matrix sorption properties can vary. An efficient method is presented whereby a particle can be followed along the variable property flowpath. For stationary flow conditions and a network of channels with advective flow and matrix diffusion, a simple analytical solution for the residence time distribution along each pathway can be used. Only two parameter groups need to be integrated along each path. For transient flow conditions, a time stepping procedure that incorporates a stochastic Monte-Carlo like method to follow the particles along the paths when flow conditions change is used. The method is fast and an example is used for illustrative purposes. It is exemplified by a case where land rises due to glacial rebound. It is shown that the effects of changing flowrates and directions can be considerable and that the diffusive migration in the matrix can have a dominating effect on the results.     

Assessment of natural attenuation of volatile aromatic hydrocarbons in agricultural soil contaminated with diesel fuel

A diesel fuel spill was simulated on a 12-m(2) plot of agricultural land, at a concentration of 1 Lm(-2) of soil. The natural attenuation of Volatile Aromatic Hydrocarbons (VAHs) was monitored at different soil depths over a period of 50 days. The natural attenuation of VAHs in the surface layer would be attributed to two processes, namely: volatilisation (mainly linked to the boiling point of each VAH, with t(1/2) from 2 to 71 min for benzene and p-isopropyltoluene, respectively); and dissipation (related to the boiling point as well as the analyte-soil matrix interaction, with t(1/2) from 2 to 169 h for benzene and p-isopropyltoluene, respectively). As expected, in the deeper layers, dissipation prevails over volatilisation. 50 days after the spill, only two VAHs were detected in the surface layer, at concentrations of 5-20 ngg(-1), which had disappeared after 80 days of the spill.     

Removal of aldrin, dieldrin, heptachlor, and heptachlor epoxide using activated carbon and/or Pseudomonas fluorescens free cell cultures

Degradation of aldrin (1,2,3,4,10,10-Hexachloro-1,4,4a,5,8,8a-hexahydro-1,4:5-8-dimethanonaphthalene), heptachlor (1H-1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano indene), dieldrin (1aalpha,2beta,2aalpha,3beta,6beta,6aalpha,7beta,7aalpha)-3,4,5,6,9,9-Hexachloro-1a,2,2a,3,6,6a,7,7a-octahydro-2,7:3,6-d-methanonaphtha[2,3-b]oxirene, and heptachlor epoxide (1aalpha, 1bbeta,2alpha,5alpha,5alphabeta,6beta,6aalpha-2,3,4,5,6,7,7-Heptachloro-1a,1b,5,5a,6,6a-hexahydro-2,5-methano-2H-inden[1,2-b]-oxirene) was tested using free cultures of Pseudomonas fluorescens under controlled conditions. Pesticide concentrations were monitored by gas chromatography during 120 h. Percentages of degradation and biodegradation rates (BDR) were calculated. Data showed a trend suggesting a relation between chemical structure and degradability. Degradation kinetics for each pesticide tested showed that the highest degradation rates were found in the first 24 h. Kinetics data were adjusted to an empirical equation in order to predict their behavior, and the correlation coefficients obtained were satisfactory. Gas chromatography/mass spectrometry (GC/MS) analysis of the final extracts allowed the identification of chlordene and monodechlorodieldrin, which have been reported as final metabolite produced in the biodegradation of this kind of compounds. Regarding adsorption of pesticides on activated vegetal carbon, we concluded that removal efficiencies between 95.45 and 97.18% can be reached, depending on the pesticide and the carbon dose applied. The values for K from the Freundlich equation were quite similar for the four pesticides (between 1.0001 and 1.04), whereas the n values were quite different for each pesticide in the following order of affinity: dieldrin > aldrin > heptachlor epoxide > heptachlor. Equilibrium times, very important for scaling up the process, were between 43 min and 1 h, for the heptachlor epoxide and the heptachlor, respectively.     

Advanced oxidation processes in the treatment of trifluraline effluent

The treatment of an effluent from the production of trifluraline was studied using a 1-L, semi-batch, tank-stirred glass reactor for performing three different advanced oxidation processes (photoperoxidation, Fenton, photo-Fenton). A commercial, medium-pressure mercury lamp was used for sample irradiation. The degradation was monitored by measurements of absorptiometric color reduction, UV-visible absorption spectra, and chemical oxygen demand (COD). The obtained results showed that the photo-Fenton process was the most effective treatment for the trifluraline effluent.     

Comparative effect of Al, Se, and Mo toxicity on NO3(-) assimilation in sunflower (Helianthus annuus L.) plants

Here, we study the effect caused by three trace elements--Al, Se, and Mo--applied at the same concentration (100 microM) and in their oxyanionic forms--NaAl(OH)(4), Na(2)SeO(4), and Na(2)MoO(4)--on NO(3)(-) assimilation (NO(3)(-), nitrate reductase (NR), nitrite reductase (NiR), glutamine synthetase (GS), and glutamate synthase (GOGAT) activities, and concentrations of amino acids and proteins) in sunflower (Helianthus annuus L. var. Kasol) plants. The most harmful element for sunflower plants proved to be selenate, followed by aluminate. On the contrary, the application of molybdate had no negative effect on the growth of this plant, suggesting the possibility of using sunflower for the phytoremediation of this metal, mainly in agricultural zones used for grazing where the excess of this element can provoke problems of molybdenosis in ruminants (particularly in cattle). In addition, we found that the alteration of NO(3)(-) assimilation by SeO(4)(2-) and Al(OH)(4)(-) directly influences the growth and development of plants, foliar inhibition of NR activity by SeO(4)(2-) being more harmful than the decrease in foliar availability of NO(3)(-) provoked by Al(OH)(4)(-).     

Two- and three-dimensional ultrasound in malformations of the medullary canal: report of four cases

A comparison between two-dimensional (2D), and three-dimensional (3D) ultrasonography was made in four fetuses diagnosed with neural tube defect (NTD) in the first half of pregnancy. 3D ultrasonography (orthogonal and multiplanar systems) proved to be an excellent complement to 2D, particularly when using orthogonal planes. When using the 3D multiplanar surface imaging system, excellent images of the malformations can be rapidly obtained. Copyright © 2001 John Wiley & Sons, Ltd.     

Accumulation fatty acids of in Chlorella vulgaris under heterotrophic conditions in relation to activity of acetyl-CoA carboxylase,temperature, and co-immobilization with Azospirillum brasilense

The relation between fatty acid accumulation, activity of acetyl-CoA carboxylase (ACC), and consequently lipid accumulation was studied in the microalgae Chlorella vulgaris co-immobilized with the plant growth-promoting bacterium Azospirillum brasilense under dark heterotrophic conditions with Na acetate as a carbon source. In C. vulgaris immobilized alone, cultivation experiments for 6 days showed that ACC activity is directly related to fatty acid accumulation, especially in the last 3 days. In co-immobilization experiments, A. brasilense exerted a significant positive effect over ACC activity, increased the quantity in all nine main fatty acids, increased total lipid accumulation in C. vulgaris, and mitigated negative effects of nonoptimal temperature for growth. No correlation between ACC activity and lipid accumulation in the cells was established for three different temperatures. This study demonstrated that the interaction between A. brasilense and C. vulgaris has a significant effect on fatty acid and lipid accumulation in the microalgae.     

Carnivorans at the Great American Biotic Interchange: new discoveries from the northern neotropics

We report two fossil procyonids, Cyonasua sp. and Chapalmalania sp., from the late Pliocene of Venezuela (Vergel Member, San Gregorio Formation) and Colombia (Ware Formation), respectively. The occurrence of these pre-Holocene procyonids outside Argentina and in the north of South America provides further information about the Great American Biotic Interchange (GABI). The new specimens are recognized in the same monophyletic group as procyonids found in the southern part of the continent, the “Cyonasua group,” formed by species of Cyonasua and Chapalmalania. The phylogenetic analysis that includes the two new findings support the view that procyonids dispersed from North America in two separate events (initially, previous to the first major migration wave—GABI 1—and then within the last major migration wave—GABI 4—). This involved reciprocal lineage migrations from North to South America, and included the evolution of South American endemic forms.