Impact of carbon nanomaterials on the behaviour of 14C-phenanthrene and 14C-benzo-[a] pyrene in soil

The impact of fullerene soot (FS), single-walled (SWCNTs) and multi-walled (MWCNTs) carbon nanotubes on the behaviour of two ¹⁴C-PAHs in sterile soil was investigated. Different concentrations of carbon nanomaterials (0, 0.05, 0.1 and 0.5%) were added to soil, and ¹⁴C-phenanthrene and ¹⁴C-benzo[a]pyrene extractability assessed over 80 d through dichloromethane (DCM) and hydroxypropyl-β-cyclodextrin (HPCD) shake extractions. Total ¹⁴C-PAH activity in soils was determined by combustion, and mineralisation of ¹⁴C-phenanthrene was monitored over 14 d, using a catabolically active pseudomonad inoculum. No significant loss of ¹⁴C-PAH-associated activity from CNM-amended soils was observed over the ‘aging’ period. CNMs had a significant impact on HPCD-extractability of ¹⁴C-PAHS; extractability decreased with increasing CNM concentration. Additionally, ¹⁴C-phenanthrene mineralisation was inhibited by the presence of CNMs at concentrations of ≥0.05%. Differences in overall extents of ¹⁴C-mineralisation were also apparent between CNM types. It is suggested the addition of CNMs to soil can reduce PAH extractability and bioaccessibility, with PAH sorption to CNMs influenced by CNM type and concentration.     

Arsenic distribution in soils and plants of an arsenic impacted former mining area

A mining area affected by the abandoned exploitation of an arsenical tungsten deposit was studied in order to assess its arsenic pollution level and the feasibility of native plants for being used in phytoremediation approaches. Soil and plant samples were collected at different distances from the polluting sources and analysed for their As content and distribution. Critical soil total concentrations of As were found, with values in the range 70-5330 mg kg⁻¹ in the uppermost layer. The plant community develops As tolerance by exclusion strategies. Of the plant species growing in the most polluted site, the shrubs Salix atrocinerea Brot. and Genista scorpius (L.) DC. exhibit the lowest bioaccumulation factor (BF) values for their aerial parts, suggesting their suitability to be used with revegetation purposes. The species Scirpus holoschoenus L. highlights for its important potential to stabilise As at root level, accumulating As contents up to 3164 mg kg⁻¹.     

Biomarker responsiveness in different tissues of caged Ruditapes philippinarum and its use within an integrated sediment quality assessment

Biomarkers comprising activities of biotransformation enzymes (ethoxyresorufin-O-deethylase -EROD-, dibenzylfluorescein dealkylase -DBF-, glutathione S-transferase -GST), antioxidant enzymes (glutathione reductase -GR- and glutathione peroxidase -GPX), lipid peroxidation -LPO- and DNA strand breaks were analyzed in the clam Ruditapes philippinarum caged at Cádiz Bay, Santander Bay and Las Palmas de Gran Canaria (LPGC) Port (Spain). Sediments were characterized. Digestive gland was the most sensitive tissue to sediment contamination. In Cádiz Bay, changes in LPO regarding day 0 were related with metals. In LPGC Port, DBF, EROD, and GST activity responses suggested the presence of undetermined contaminants which might have led to DNA damage. In Santander Bay, PAHs were related with EROD activity, organic and metal contamination was found to be associated with GR and GST activities and DNA damage presented significant (p < 0.05) induction. R. philippinarum was sensitive to sediment contamination at biochemical level. Biomarkers allowed chemical exposure and sediment quality assessment.     

Concentration of trace elements in feathers of three Antarctic penguins: Geographical and interspecific differences

Antarctica is often considered as one of the last pristine regions, but it could be affected by pollution at global and local scale. Concentrations of Al, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Cd and Pb were determinated by ICP-MS in feathers (n = 207 individuals) of gentoo, chinstrap and Adélie penguin collected in 8 locations throughout the Antarctic Peninsula (2006-2007). The highest levels of several elements were found in samples from King George Island (8.08, 20.29 and 1.76 μg g⁻¹ dw for Cr, Cu and Pb, respectively) and Deception Island (203.13, 3.26 and 164.26 μg g⁻¹ dw for Al, Mn and Fe, respectively), where probably human activities and large-scale transport of pollutants contribute to increase metal levels. Concentrations of Cr, Mn, Cu, Se or Pb, which are similar to others found in different regions of the world, show that some areas in Antarctica are not utterly pristine.     

Antiradical activity of natural honeys and antifungal effect against Penicillium genera

The purpose of the study was to examine the antiradical activity of 11 natural honeys and to evaluate the antifungal properties of honey. Honey samples (10) were collected from different locations of Slovak Republic. Honeys were native to different plant species of Robinia pseudoacaccia, Brassica napus subs. napus, Castanea sativa Mill. Thymus serpyllum vulgaris and the other samples had multifloral origin. The low antiradical activitity in honey samples was determined. The best results were found in thyme honey from Rhodos (11.84 %) and Castanea honey from Nitra (10.61 %). The lowest antiradical activity was found in Acacia honey and determined to be 7.62 %. Statistically significant differences (P< 0.001) were found among thyme/Rhodos and Castanea/Nitra. The antifungal activities of honey samples were tested by 10 %, 25 % and 50 % (by mass per volume) concentration against fungi Penicillium crustosum, P. expansum, P. griseofulvum, P. raistrickii and P. verrucosum and by the agar well diffusion method. The solutions containing 10 % (by mass per volume) of honey did not have any effect on the growth of fungi. The strongest antifungal effect was shown by 50 % honey concentration against P. raistrickii.     

Accumulation,biotransformation, and biochemical responses after exposure to arsenite and arsenate in the estuarine polychaete <Emphasis Type="BoldItalic">Laeonereis acuta</Emphasis> (Nereididae)

Introduction  

This study aimed to analyze antioxidant responses and oxidative damage induced by two inorganic forms of arsenic (As; As^III and As^V) in an estuarine polychaete species, Laeonereis acuta (Nereididae). The capacity of arsenic biotransformation was also evaluated through the methylation process considering the activity of a key enzyme involved in the metabolization process.     

Analysis and fit of surface CO2 concentrations at a rural site

Purpose

The impact of CO₂ urban plume in a rural area was investigated by concentrations recorded near surface.

Methods

CO₂ dry concentrations at three levels near surface were recorded for about 8 months at a rural site. Daily cycles were obtained and directional analysis was made with percentiles. Several functions were used to fit background and plume concentrations and the goodness of fit was evaluated with different statistics, which were also compared.

Results

Daily cycle showed a difference of around 2 ppm during the night between the lowest (1.8 m) and the highest (8.3 m) levels. Weighting functions of the directional analysis revealed the influence of the Valladolid urban plume. Two regions were established, with local factors prevailing below 3 m?s^?1 and transport dominating above 6 m?s^?1. The best fit was achieved with a quadratic function for the background and a cubic function for the plume due to the lack of symmetry observed. Gamma and Weibull distributions were also successfully used. Some statistics, such as the root mean square error (RMSE), stood out when evaluating the goodness of fit, whilst others were discarded due to their extremely low values and the lack of sensitivity against the functions used. Finally, a comprehensive metric merging several statistics was also tested with slight differences against RMSE.     

Molecular cloning and expression of novel metallothionein (MT) gene in the polychaete Perinereis nuntia exposed to metals

To report a novel metallothionein (MT) gene and evaluate its potency as a biomarker, we clone this MT gene and measured the expression levels in the metal-exposed polychaete Perinereis nuntia. Accumulated metal contents and metallothionein-like proteins (MTLPs), which have been recognized as potential biomarkers, were compared with the relative mRNA expressions of the MT gene of P. nuntia (Pn-MT). In addition, the metal-binding affinity was estimated by recombinant Pn-MT protein. Pn-MT having high cysteine residues with three metal response elements in the promoter region closely clusters with those of other invertebrates. The accumulation patterns of metals were dependent on the exposure times in lead (Pb), cadmium (Cd), and copper (Cu) exposure. Particularly, both MTLP levels and relative mRNA expressions of MT were increased with accumulated metal contents and exposure time in P. nuntia exposed to Pb and Cd. There was no significant modulation of the Pn-MT gene in polychaetes exposed to Zn and As. However, the metal-binding ability of the recombinant Pn-MT protein provides a clear evidence for a high affinity of MT to several metal elements. These results suggest that Pn-MT would play an important role in the detoxification and/or sequestration of specific metals (e.g., Pb and Cd) in P. nuntia and have potential as a molecular biomarker in the monitoring of the marine environment using a polychaete.     

Nitrous oxide and methane emission from a flooded rice field as influenced by separate and combined application of herbicides bensulfuron methyl and pretilachlor

Combination of divergent active principles to achieve broad-spectrum control is gaining popularity to manage the weed menace in intensive agriculture. However, such application could have non-target impacts on the soil processes affecting soil ecology and environmental interactions. A field experiment was conducted to investigate the impact of separate and combined applications of herbicides bensulfuron methyl and pretilachlor on the emission of N₂O and CH₄, and related soil and microbial parameters in a flooded alluvial field planted to rice cv Lalat. Single application of the herbicide bensulfuron methyl or pretilachlor resulted in a significant reduction of N₂O and CH₄ emissions while the combination of these two herbicides distinctly increased N₂O and CH₄ emissions. Cumulative N₂O emissions (kg N₂O-N) followed the order of bensulfuron methyl (0.35 kg ha⁻¹) < pretilachlor (0.36 kg ha⁻¹) < control (0.45 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% single dose (0.49 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% double dose (0.54 kg ha⁻¹). Cumulative CH₄ emissions (kg CH₄), on the other hand, followed the order of bensulfuron methyl (47.89 kg ha⁻¹) < pretilachlor (73.17 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% single dose (93.50 kg ha⁻¹) < control (106.54 kg ha⁻¹) < bensulfuron methyl 0.6% + pretilachlor 6.0% double dose (124.67 kg ha⁻¹). The inhibitory effect of separate application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% on N₂O emission was linked to lower mineral N, lower denitrifying and nitrifying activity and low denitrifier and nitrifier populations. Inhibitory effect on CH₄ emission, on the contrary, was linked to prevention in the drop of redox potential, lower readily mineralizable carbon (RMC) and microbial biomass carbon (MBC) contents as well as lower methanogenic and higher methanotrophic bacterial population. Admittedly, stimulatory effect of combined application of herbicides bensulfuron methyl 0.6% and pretilachlor 6.0% at double dose on N₂O and CH₄ emission was related to reversal of the identified indicators of inhibition. Results indicate that while individual application of herbicides bensulfuron methyl 0.6% or pretilachlor 6.0% can reduce N₂O and CH₄ emission from flooded soil planted to rice, their combined application at normal dose can keep the emission at a comparatively lower level with significantly higher grain yield as compared to the herbicides applied alone.