Major inputs and mobility of potentially toxic elements contamination in urban areas

Soil quality in urban areas is affected by anthropogenic activities, posing a risk to human health and ecosystems. Since the pseudo-total concentrations of potentially toxic elements may not reflect their potential risks, the study of element mobility is very important on a risk assessment basis. This study aims at characterising the distribution and major sources of 34 elements in two Portuguese urban areas (Lisbon and Viseu), with different geological characteristics, industrial and urban development processes. Furthermore, the potential availability of As, Co, Cr, Cu, Ni, Pb and Zn was assessed, by measuring the fraction easily mobilised. Lisbon is enriched in elements of geogenic and anthropogenic origin, whereas in the smaller city, the high levels observed are mainly related to a geogenic origin. Background values can be more relevant than the dimension of the city, even when anthropogenic components may be present, and this parameter should be considered when comparing results from different cities. Regarding the potential available fraction, a high variability of results was observed for elements and for sampling sites with an influence of the soil’s general characteristics. Elements showing very high concentrations due to geological reasons presented, in general, a low mobility and it was not dependent on the degree of contamination. For elements with major anthropogenic origin, only Zn was dependent on the pseudo-total content. Yet, the highest available fractions of some elements, both with major geogenic and anthropogenic origin, were observed in specific contaminated samples. Therefore, a site-specific evaluation in urban soils is important due to the high spatial variability and heterogeneity.     

Uptake,translocation, and control of trumpet flower (Tecoma stans) with aminocyclopyrachlor

To gain a better understanding of the physiology of the herbicide aminocyclopyrachlor in young plants of trumpet flower, the uptake and translocation were evaluated after the application of herbicide. This was determined by treating individual leaves with formulated herbicides plus ¹⁴C-aminocyclopyrachlor after the application of the formulated herbicide. This experiment used a randomized experimental design with three replications. In addition, field studies were conducted to assess the effectiveness of foliar applications of aminocyclopyrachlor in association with metsulfuton-methyl. The plant absorbed 20% of the herbicide applied. The translocation percentage did not surpass 5% of the total amount applied. Only 1% of the herbicide applied was translocated to the roots. Rate of 40 + 13 g a.i. 100 L^?1 of aminocyclopyrachlor+metsulfuron-methyl was effective to control T. stans.     

Kinetic Behavior in Melt State and Solid State Polymerization of Lactide Using Magnesium Stearate as Catalyst

Solid state polymerizations (SSP) and the kinetic behavior in melt state of l-lactide polymerizations employing magnesium stearate as catalyst were investigated. The solid state polymerizations were carried out in two steps where pre-polymers were first prepared in melt polymerizations at 180 °C and the subsequent post-polymerizations were performed around the Tc of polylactide (PLA). In order to find the initial SSP conditions, kinetic profiles of melt polymerizations of l-lactide with magnesium stearate were determined. According to the kinetics data the melt polymerizations were found to be first order with respect to lactide as evident from a linear relationship of logarithmic variations of l-lactide concentration versus time using catalyst/monomer ratios of 1:500 and 1:5,000. When the catalyst content is increased to 1:100 the relationship loses its linearity due to fast propagation in the early stages of the reaction. From the GPC data it can be noted that the molecular weight of PLA can be increased by 5–17 times under the conditions established for our SSP experiments. A comparison between the two step solid state polymerizations and already reported melt polymerizations using the same catalyst showed that SSP furnished polymers with much lower amount of polymer degradation.     

How the redox state of tobacco 'Bel-W3' is modified in response to ozone and other environmental factors in a sub-tropical area?

This study intended to determine whether the redox state in plants of Nicotiana tabacum ‘Bel-W3’ fluctuates in response to the environmental factors in a sub-tropical area contaminated by ozone (São Paulo, SE - Brazil) and which environmental factors are related to this fluctuation, discussing their biomonitoring efficiency. We comparatively evaluated the indicators of redox state (ascorbic acid, glutathione, superoxide dismutase, ascorbate peroxidase, and glutathione reductase) and leaf injury in 17 field experiments performed in 2008. The redox state was explained by the combined effects of chronic levels of O₃ and meteorological variables 4-6 days prior to the plant sampling. Moderate leaf injury was observed in most cases. The redox state of tobacco decreases few days after their placement in the sub-tropical environment, causing them to become susceptible to oxidative stress imposed by chronic doses of O₃. Its bioindicator efficiency would not be diminished in such levels of atmospheric contamination.     

Exposure of Chironomus riparius larvae to uranium: effects on survival, development time, growth, and mouthpart deformities

Among non-biologically essential metals, data concerning uranium effects on freshwater benthic macroinvertebrates are scarce. The effects of uranium on survival, development time, growth and mouthpart deformities of midge Chironomus riparius were investigated. A 10-day static laboratory bioassay was performed exposing first instar larvae to artificial sediment spiked with four concentrations of uranium (2.97; 6.07; 11.44; 23.84 microg U g(-1) dry wt). As uranium was released from the sediment to the overlying water during this bioassay, both the sediment and the water column act as contamination pathways in giving rise to the observed effects. Significant negative effects on survival, development time, and growth were detected at 6.07, 6.07 and 2.97 microg U g(-1) dry wt, respectively. An LC20 of 2.49 microg U g(-1) dry wt (95% CI=1.48-4.27), and an LC50 of 5.30 microg U g(-1) dry wt (95% CI=3.94-7.25) were estimated. With respect to effects of uranium on larvae mouthpart deformities, we found that the lower the concentrations, the higher the deformity rates. These results highlight the potential impact of uranium at population level in environmentally realistic concentrations.     

The role of halophytic nanoparticles towards the remediation of degraded and saline agricultural lands

Environmental Science and Pollution Research - Salinity is one of the major causes of abiotic stress that leads to a reduction in crop yield. One strategy to alleviate and improve crop yield is to...     

Low genetic differentiation between isolated populations of the colonial ascidian Symplegma rubra Monniot, C. 1972

Pelagic larvae are highly important for maintaining the gene flow among populations of sessile marine invertebrates. Colonial ascidians consist, exclusively, of brooding species, with lecithotrophic larvae that have a limited dispersal. As a result, there is a marked differentiation among populations. In this work, we used allozyme electrophoresis to access the genetic variation in four populations of Symplegma rubra, a colonial ascidian frequently found in the intertidal zone of Southeastern Brazilian coast. High variability was found at three of the four sites sampled, the exception being Praia Grande in the State of Rio de Janeiro. At this site, there was a great preponderance of clones, which possibly reflected the enclosed nature of the location and its low water circulation that reduce the dispersal capabilities of these animals. S. rubra did not conform to expectations for random mating (Hardy–Weinberg equilibrium): there was a deficit of heterozygotes that was more related to the small population size than to inbreeding processes, since F _is analysis per locus revealed a deficiency of heterozygotes at only one locus—MDH*. The greatest variation in allele frequency was found for GPI-2*. Analyses of genetic variability revealed moderate differentiation among the populations (F _ST=0.051), which was unexpected for a species with a low dispersal capability. Rafting, a frequently underestimated means of dispersal, may be the main mode of gene flow in this species over large areas, since colonies of S. rubra are frequently seen growing on drift material and there is no evidence that the larva survive for a long time in the plankton.     

Uncommon formation of two antiparallel sperm bundles per cyst in tenebrionid beetles (Coleoptera)

Several species of Tenebrionidae are stored-grain pests. Since they belong to a specious family, the systematics of these beetles is still in doubt. In insects, spermatogenesis and the spermatozoa exhibit great diversity, and are therefore commonly used in phylogenetic and taxonomic analyses. During the spermatogenetic process in these organisms, the cells originating from a single spermatogonium develop synchronically in groups referred to as cysts. At the end of this process, there is usually only one sperm bundle per cyst, with all the cells in the same orientation. This paper details the spermiogenesis of the tenebrionid beetles Tenebrio molitor, Zophobas confusa, Tribolium castaneum and Palembus dermestoides using whole mount and histological sections of the cysts. In these species, spermatogenesis is similar to that which occurs in most insects. However, during spermiogenesis, the nuclei of the spermatids migrate to two opposite regions at the periphery of the cyst, leading to the uncommon formation of two bundles of spermatozoa per cyst. This feature is possibly an apomorphy for Tenebrionidae.     

Attraction of entomopathogenic nematodes to sugarcane root volatiles under herbivory by a sap-sucking insect

Few systems have been described in which herbivore-induced root volatiles mediate attraction of entomopathogenic nematodes (EPNs), and they only concern root damage inflicted by chewing insects. EPNs, especially Heterorhabditis indica and Steinernema carpocapsae, are potential biological control agents of sugarcane spittlebug (Mahanarva fimbriolata) populations. Here, we investigated the response of these two species of EPNs to sugarcane root volatiles damaged by M. fimbriolata nymphs in a belowground six-arm olfactometer. We also examined changes on root volatile profile in response to herbivory of sugarcane spittlebug nymphs. Results showed that both EPN species did not discriminate between odors of undamaged sugarcane and moistened sand (blank). However, when EPNs were exposed to odors of spittlebug-damaged and undamaged sugarcane roots, both species significantly preferred odors of spittlebug-damaged roots. Headspace collection followed by GC–MS analyses showed no qualitative difference (total of 11 compounds) between volatile profiles of spittlebug-damaged and undamaged sugarcane roots. In contrast to the previous studies involving feeding by root chewing insects, our root volatile analysis did not reveal any up-regulation resulting from sugarcane spittlebug damage, but the down-regulation of the terpenes dihydromyrcenol and β-isomethyl ionone when compared with the profile of undamaged sugarcane roots. Here, we propose alternative explanations for the EPN attraction to spittlebug-damaged roots as it is unlikely that reduced concentrations of the volatiles play a role in this interaction. Further studies are necessary to determine the key compounds of the root volatile emission to enhance biological control efficacy with EPNs against M. fimbriolata in sugarcane.