Photochemical Behavior of Parathion in the Presence of Humic Acids from Different Origins

This paper reports the effect of ultraviolet radiation on the degradation of pesticide ethyl parathion in the presence of humic acids. Ethyl parathion was completely degraded in 300 min using an artificial lamp of 7.41 × 10^{? 10} einstein/s. Humic acid from peat did not influence the photochemical rate (k = 8.92 × 10^?3 min). However, in the presence of aquatic humic acid, the photochemical rate was higher (11.5 × 10^?3 min). The analytical determinations show the presence of p-nitrophenol and aminophenol in the reaction medium during the photochemical experiments. The kinetic of degradation in all experiments obeyed a first-order reaction pattern.     

Influence of Care of Domestic Carnivores on Their Predation on Vertebrates

Abstract: Domestic dogs (Canis familiaris) and cats (Felis catus) are the most abundant mammalian carnivores worldwide. Given that domestic carnivores rely on human‐provided food, their densities are usually independent of prey densities. Nevertheless, underfed pets may need to hunt to meet their energetic and nutritional requirements. We explored the effects of different levels of care (provision of food) of dogs and cats on their predation rates on wild vertebrates in 2 areas of southern Chile. We interviewed cat and dog owners and analyzed prey remains in scats of pets to examine how domestic dogs and cats were managed and to gather information on the wild vertebrates killed and harassed by pets. We used logistic regression to examine the association between pet care and the frequency of wild vertebrate remains in scats. The probability of a dog preying on vertebrates was higher for poorly fed than for adequately fed dogs (odds ratio = 3.7) and for poorly fed than for adequately fed cats (odds ratio = 4.7). Domestic dogs and cats preyed on most endemic and threatened mammals present in the study sites. Our results provide support for the hypothesis that the less care domestic animals receive from owners the higher the probability those animals will prey on wild vertebrates.     

Fencerows, Edges, and Implications of Changing Connectivity Illustrated by Two Contiguous Ohio Landscapes

We evaluated the amounts and implications of changes in habitat connectivity on rural landscapes by modeling the colonization success and subsequent habitat colonization of a model edge organism within real landscapes. We first inventoried the changes in the fencerow and forest-edge network of two contiguous Ohio (U.S.A.) landscapes, an agriculturally dominated till plain and a more diverse and dynamic moraine landscape, from 1940 to 1988. On the moraine the number of fencerows changed little from 1940 to 1971. The number increased by 86 during 1971–1988 as marginal farms were subdivided. The total length of fencerows on the moraine increased 2.5-fold over 48 years. On the till plain the number and total length of fencerows remained relatively constant through the study period. The sum of fencerows and forest edges was used as a measure of total ecotonal edge. On the moraine total edge increased through the study period, whereas on the till plain it decreased. We selected two levels of landscape connectivity, low and high, to model animal habitat colonization success. As connectivity increased the earliest successful colonists preempted an increasingly large proportion of the total suitable habitat, and the probability of successful colonization by later-arriving individuals decreased. The changes in connectivity that resulted from changes in both the fencerow network and the proportion of forested land have resulted in contiguous landscapes that present very different colonization potentials to organisms with long-distance dispersal capability. Given the current uncertainty of the effects of corridors on species-preservation efforts, we suggest that further modeling of this type prior to field testing will add useful insights, especially if conducted using specific species and landscape types.     

COPPER PRICE STABILIZATION: WELFARE CONSEQUENCES AND BUFFER STOCK COSTS

International debate and economic literature on export earnings from trade in raw materials have focused on two main subjects: the ability to increase incomes arising from the exports and the possibility of stabilizing these incomes. One alternative that has been suggested and discussed with regard to the second issue is a buffer stock that would decrease the fluctuations in raw material prices. Two objections that have been made to this proposal are that, with stabilization, producers could lose their welfare benefits; and that financial costs are too great. In this article, market conditions required so that copper producers may be benefited by price stability are discussed, and the profitability of a copper buffer stock is measured. Depending on the characteristics of demand and supply curves in the copper market, the article concludes that producers may obtain welfare and income benefits from price stabilization and that for certain degrees of stability the management of the copper buffer stock can yield a positive internal rate of return close to that of alternative investments. Des discussions au niveau international et des ouvrages économiques en matière de recettes d'exportation provenant du commerce des matiêres premières ont mis l'accent sur deux sujets principaux: la capacité d'accroître les revenue de ces exportations et la possibilité de stabiliser ces revenue. Une option, suggérée et débattue au sujet du second point, consiste en l'établissement d'un stock régulateur qui tendrait à diminuer les fluctuations des prix des matiêres premières. Cependant, deux objections ont été soulevées, à savoir: la stabilisation pourrait avoir des repercussions néfastes sur les bénéfices des producteurs et les coûts financiers pourraient être trap élevés. L'article considère les conditions de marché requises pour permettre aux producteurs de cuivre de bénéficier de la stabilité des prix ainsi que la rentabilité d'un stock régulateur en matière de cuivre. En se basant sur les caractéristiques des courbes de l'offre et de la demande dans le marché du cuivre, l'article conclut que les producteurs peuvent bénéficier de la stabilisation des prix et que, à certains degrés de stabilité, la gestion d'un stock régulateur de cuivre peut engendrer un taux de rendement interne positif avoisinant ceux d'autres investissements. Los debates internacionales y la literature sobre los ingresos de exportatión de materias primas han enfocado dos temas principals: la habilidad de aumentar el ingreso resultante de estas exportaciones y la posibilidad de estabilizar dichos ingresos. La creación de una reserva de compensación para contrarrestar las fluctuaciones de los precios de materias primas ha sido propuesto y discutido. Las objeciones hechas a esta propuesta argumentan que los beneficios para los productores disminuiría con la estabilización y que los costos financieros serian demasiado grandes. En este artículo se discuten las condiciones de mercado que permitirían a los productores de cobre beneficiarse de la estabilidad de precios y se mide también la rentabilidad de la reserva de compensación para el cobre. Basándose en las características de las curvas de demanda y oferta en el mercado del cobre, el artículo concluye que los productores pueden salir gananciosos con la estabilización de precios y que para ciertos grados de estabilidad, la administración de la reserva de compensación del cobre puede producir una tasa interna de retorno positive, comparable a otras inversiones alternatives.     

A multi-integrated approach on toxicity effects of engineered TiO2 nanoparticles

The new properties of engineered nanoparticles drive the need for new knowledge on the safety, fate, behavior and biologic effects of these particles on organisms and ecosystems. Titanium dioxide nanoparticles have been used extensively for a wide range of applications, e.g, self-cleaning surface coatings, solar cells, water treatment agents, topical sunscreens. Within this scenario increased environmental exposure can be expected but data on the ecotoxicological evaluation of nanoparticles are still scarce. The main purpose of this work was the evaluation of effects of TiO₂ nanoparticles in several organisms, covering different trophic levels, using a battery of aquatic assays. Using fish as a vertebrate model organism tissue histological and ultrastructural observations and the stress enzyme activity were also studied. TiO₂ nanoparticles (Aeroxide® P25), two phase composition of anatase (65%) and rutile (35%) with an average particle size value of 27.6±11 nm were used. Results on the EC₅₀ for the tested aquatic organisms showed toxicity for the bacteria, the algae and the crustacean, being the algae the most sensitive tested organism. The aquatic plant Lemna minor showed no effect on growth. The fish Carassius auratus showed no effect on a 21 day survival test, though at a biochemical level the cytosolic Glutathione-S-Transferase total activity, in intestines, showed a general significant decrease (p<0.05) after 14 days of exposure for all tested concentrations. The presence of TiO₂ nanoparticles aggregates were observed in the intestine lumen but their internalization by intestine cells could not be confirmed.