Copper oxide nanoparticles can induce toxicity to the freshwater shredder Allogamus ligonifer

Increased commercialisation of nanometal-based products augments the possibility of their deposition into aquatic ecosystems; this, in turn, may pose risks to aquatic biota and associated ecological functions. Freshwater invertebrate shredders mostly use microbially-colonized plant litter as food resource and play an important role in aquatic detritus food webs. We assessed lethal effects of nanoCuO on the shredder Allogamus ligonifer (Trichoptera, Limnephilidae) by determining the concentration that induced 50% of death (LC₅₀), and sublethal effects of nanoCuO on the feeding behaviour and growth of the shredder by exposing the animals to: (i) stream water supplemented with nanoCuO and microbially-colonized leaves, and (ii) stream water (without nanoCuO) and microbially-colonized leaves pre-exposed to nanoCuO. Results from acute lethal tests showed that the 96 h LC₅₀ of nanoCuO was very high (569 mg L⁻¹). In the absence of nanoparticles, leaf consumption rate was 0.27 mg leaf DM mg⁻¹ animal DM d⁻¹ and the shredder growth rate was 56 μg animal DM mg⁻¹ animal DM d⁻¹. A significant inhibition in leaf consumption rate (up to 47%) and invertebrate growth rate (up to 46%) was observed when shredders were exposed to the higher tested sublethal concentration of nanoCuO (75 mg L⁻¹) through either contaminated stream water or pre-contaminated food. The exposure to increased nanoCuO concentration via water or pre-contaminated food led to higher accumulation of copper in the larval body. Leached water-soluble ionic copper from the nanoCuO adsorbed or accumulated in the shredder (up to 10.2% of total Cu) seemed to influence the feeding behaviour and growth of the shredder.     

Planetary Stewardship in an Urbanizing World: Beyond City Limits

Cities are rapidly increasing in importance as a major factor shaping the Earth system, and therefore, must take corresponding responsibility. With currently over half the world’s population, cities are supported by resources originating from primarily rural regions often located around the world far distant from the urban loci of use. The sustainability of a city can no longer be considered in isolation from the sustainability of human and natural resources it uses from proximal or distant regions, or the combined resource use and impacts of cities globally. The world’s multiple and complex environmental and social challenges require interconnected solutions and coordinated governance approaches to planetary stewardship. We suggest that a key component of planetary stewardship is a global system of cities that develop sustainable processes and policies in concert with its non-urban areas. The potential for cities to cooperate as a system and with rural connectivity could increase their capacity to effect change and foster stewardship at the planetary scale and also increase their resource security.     

The efficiency of tobacco Bel-W3 and native species for ozone biomonitoring in subtropical climate, as revealed by histo-cytochemical techniques

We aimed to verify whether hydrogen peroxide (H₂O₂) accumulation and cell death are detected early in three bioindicators of ozone (O₃), Nicotiana tabacum ‘Bel-W3’, Ipomoea nil ‘Scarlet O’Hara’ and Psidium guajava ‘Paluma’, and whether environmental factors also affect those microscopic markers. The three species were exposed to chronic levels of O₃ in a subtropical area and a histo-cytochemical technique that combines 3,3′-diaminobenzidine (DAB) with Evans blue staining was used in the assessments. The three species accumulated H₂O₂, but a positive correlation with O₃ concentration was only observed in N. tabacum. A positive correlation between O₃ and cellular death was also observed in N. tabacum. In I. nil and P. guajava, environmental factors were responsible for symptoms at the microscopic level, especially in P. guajava. We conclude that the most appropriate and least appropriate bioindicator plant for O₃ monitoring in the subtropics are N. tabacum ‘Bel-W3’ and P. guajava ‘Paluma’, respectively.     

Host-guest complexes of phenoxy alkyl acid herbicides and cyclodextrins. MCPA and β-cyclodextrin

The chlorophenoxy herbicide MCPA (4-chloro-2-methylphenoxyacetic acid), widely used for the control of broad-leaf weeds primarily in cereal and grass seed crops, still remains one of the most often used herbicides in Portugal. As the formation of inclusion complexes with cyclodextrins can improve its solubility properties, the interaction between the herbicide MCPA and β-cyclodextrin was investigated. The stability constants describing the extent of formation of the complexes have been determined by phase-solubility studies. Different analytical techniques [ultraviolet-visible spectroscopy (UV-Vis), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR)] were employed for a thorough investigation of the structural characteristics of the obtained complexes, which exhibited distinct features and properties from both “guest” and “host” molecules. FTIR and ¹H NMR data obtained for the MCPA/β-CD complexes gave information about the interaction between MCPA and the nonpolar cyclodextrin cavity. The dramatic change observed in band frequency and proton displacements of OCH₂ group and H6 aromatic proton confirmed the inclusion of MCPA in β-CD.

The formation of an inclusion complex between MCPA and β-CD increased the aqueous solubility of this herbicide which could be a particularly advantageous property for some specific applications, namely to improve commercial formulation and for environmental protection.     

Degradation of atrazine using solar driven fenton-like advanced oxidation processes

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) was degraded using cobalt-peroximonosulfate (Co/PMS) advanced oxidation process (AOP). Three Co concentrations (0.00, 0.25 and 0.50 mM) and five peroximonosulfate (PMS) concentrations (0, 5, 8, 16 and 32 mM) were tested. Maximum degradation reached was 88% using dark Co/PMS in 126 minutes when 0.25 mM of cobalt and 32 mM of PMS were used. Complete atrazine degradation was achieved when the samples were irradiated by the sun under the same experimental conditions described. Tests for identification of intermediate products allowed identification and quantification of deethylatrazine in both dark and radiated conditions. Kinetic data for both processes was calculated fitting a pseudo-first order reaction rate approach to the experimental data. Having kinetic parameters enabled comparison between both conditions. It was found that the kinetic approach describes data behavior appropriately (R² ≥ 0.95). Pseudo-kinetic constants determined for both Co/PMS processes, show k value of 10^?4 for Co/PMS and a k value of 10^?3 for Co/PMS/ultraviolet (UV). This means, that, with the same Co/PMS concentrations, UV light increases the reaction rate by around one order of magnitude than performing the reaction under dark conditions.     

Cytotoxic and genotoxic effects of silver nanoparticle/carboxymethyl cellulose on <Emphasis Type="Italic">Allium cepa</Emphasis>

Several mutagenic agents may be present in substances released in the environment, which may cause serious environmental impacts. Among these substances, there is a special concern regarding the widespread use of silver nanoparticles (AgNP) in several products due to their widely known bactericidal properties, including in the medical field and the food industry (e.g., active packaging). The assessment of the effects of AgNP released in the environment, having different concentrations, sizes, and being associated or not to other types of materials, including polymers, is therefore essential. In this research, the objective was to evaluate the genotoxic and cytotoxic effects of AgNP (size range between 2 and 8 nm) on root meristematic cells of Allium cepa (A. cepa). Tests were carried out in the presence of colloidal solution of AgNP and AgNP mixed with carboxymethylcellulose (CMC), using distinct concentrations of AgNP. As a result, when compared to control samples, AgNP induced a mitotic index decrease and an increase of chromosomal aberration number for two studied concentrations. When AgNP was in the presence of CMC, no cytotoxic potential was verified, but only the genotoxic potential for AgNP dispersion having concentration of 12.4 ppm.     

Factors affecting RPSI in imposex monitoring studies using Nucella lapillus (L.) as bioindicator

Nucella lapillus (L.) is a marine gastropod mollusc widely used as a bioindicator of TBT pollution in the North Atlantic coastlines. The species reproductive cycle and the male penis length seasonal/spatial variation were studied at a single site at Aveiro seashore (NW Portugal) between December 2005 and June 2007. The main objective of this work is to assess if the "Relative Penis Size Index" (RPSI)--an important imposex assessment index--varies seasonally and spatially in the same sampling site and how this can affect results obtained in imposex monitoring programmes. Animals able to reproduce were found every month but a seasonal pattern in N. lapillus reproductive cycle was evident. Female gametogenic maturation varied seasonally and a decrease in capsule gland volume and condition factor occurred in late summer/early autumn. The gametogenesis in males did not show a significant seasonal variation as in females but the condition factor, penis length, amount of sperm and prostate volume also diminished in late summer/early autumn. On the other hand, males that were close to egg capsules clusters had larger penises than those far away from clusters. The temporal and spatial male penis length variation introduces a bias on imposex assessment results when using RPSI and the magnitude of the error involved is evaluated for different TBT pollution levels scenarios. We consider that RPSI provides interesting and complementary information that should not be excluded from monitoring programmes, but temporal or spatial comparisons of imposex should be based on other more reliable imposex indices like the VDSI.     

Integrating pattern-based modelling and political ecology in land-use change research: the case of Mexican dry tropics

ABSTRACT

Agricultural and extractive frontiers experiment rapid landscape transformation. Land-Use Sciences and Political Ecology are complementary approaches for analysing how landscape transformations are related to biophysical conditions, and socioeconomic, cultural and political processes developed at global, national and local scales. This study examines such relationships in a long-standing agrarian and resource frontier in southern Mexico for the 1986–2015 period. We combine insights from: (1) a quantitative land use/land cover change pattern-based model, involving a weights of evidence and cellular automata simulations, and (2) a qualitative content analysis of literature and of local actors’ perspectives. Two grand frontier processes have developed in this region: NAFTA-related agrarian transition toward intensification and the establishment of wind farms. Both were triggered by global forces and new forms of land and resources use, but mediated by national-to-local ecological, socioeconomic and political processes, producing particular landscape transformations.     

Monitoring trace metals in urban aerosols from Buenos Aires city. Determination by plasma-based techniques

A study was undertaken, within the framework of a 3 years national project, to assess the content of 13 elements in airborne particulate matter collected in representative zones of the metropolitan area of Buenos Aires. The sampling strategy followed consisted in collecting simultaneously 67 samples of PM10 particulate matter in 9 sampling sites covering an area of about 30 km2 during one week. The collection was performed on ash-free fibre-glass filters using high volume samplers. A combination of aqua regia and perchloric acid was used for leaching metals from filters. Key elements, namely Al, Ca, Cu, Fe, Mn, Mo, Ni, Pb, S, Sb, Sn, Zn and Zr, were determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS) at micro g g(-1) and ng g(-1) levels. Analyte concentration varied from 130 ng g(-1)(Mo) to over 30%(Ca). Multivariate statistical analysis was performed on the data set including the measured elemental compositions for the monitored period. The atmospheric concentration found for Pb confirms the decreasing levels of this element since the introduction of unleaded gasoline in 1995: 88 ng m(-3)(2001) < 220 ng m(-3)(1997) < 3900 ng m(-3)(1994). The average S concentration above 3 microg m(-3) is somehow unexpectedly high for Buenos Aires since the relatively low S content of liquid fuels and the massive usage of natural gas imply low emissions of this element from combustion activities. To the best of our knowledge, S concentrations are reported for the first time for this city.