Impact of biofumigation with solarization on degradation of pesticides and heavy metal accumulation

A greenhouse study was conducted to evaluate the effect of biofumigation (with sheep and chicken manure) combined with solarization on the dissipation of pesticides (pyrifenox, DDT and dieldrin), and on soil metals accumulation. The treatments consisted of a control, and soil disinfestations by biofumigation combined with solarization (B+S) for two, four, five, six consecutive years. B+S enhanced the dissipation of pyrifenox with regard to control treatment. Significant differences were not detected among plots disinfected with B+S for consecutive years. On the other hand, B+S had no effect on the dissipation of DDT and dieldrin, probably due to the resistance of these pesticides to microbial degradation and/or high temperatures. Biofumigation is considered to be an environmentally safe practice, since no accumulation of heavy metals such as Cd, Co, Cu, Cr, Pb, Ni, or Zn was observed after the subsequent application of organic matter through the treatments.     

A Comparison of Bayesian Methods for Uncertainty Analysis in Hydraulic and Hydrodynamic Modeling

We evaluate and compare the performance of Bayesian Monte Carlo (BMC), Markov chain Monte Carlo (MCMC), and the Generalized Likelihood Uncertainty Estimation (GLUE) for uncertainty analysis in hydraulic and hydrodynamic modeling (HHM) studies. The methods are evaluated in a synthetic 1D wave routing exercise based on the diffusion wave model, and in a multidimensional hydrodynamic study based on the Environmental Fluid Dynamics Code to simulate estuarine circulation processes in Weeks Bay, Alabama. Results show that BMC and MCMC provide similar estimates of uncertainty. The posterior parameter densities computed by both methods are highly consistent, as well as the calibrated parameter estimates and uncertainty bounds. Although some studies suggest that MCMC is more efficient than BMC, our results did not show a clear difference between the performance of the two methods. This seems to be due to the low number of model parameters typically involved in HHM studies, and the use of the same likelihood function. In fact, for these studies, the implementation of BMC results simpler and provides similar results to MCMC. The results of GLUE are, on the other hand, less consistent to the results of BMC and MCMC in both applications. The posterior probability densities tend to be flat and similar to the uniform priors, which can result in calibrated parameter estimates centered in the parametric space.     

Assessment of Water Quality in a Border Region Between the Atlantic Forest and an Urbanised Area in Rio de Janeiro,Brazil

The preservation of water resources is one of the goals of the designation of parks that act as natural reservoirs. In order to assess the impact of the presence of humans in an environmental preservation area bordering urban areas, the presence of four pathogenic enteric viruses [group A rotavirus (RV-A), norovirus (NoV), human adenoviruses (HAdV), and hepatitis A virus (HAV)], as well as the physico-chemical parameters, and Escherichia coli levels were assessed in riverine water samples. From June 2008 to May 2009, monthly monitoring was performed along the Engenho Novo River. RV-A, NoV, and HAdV were observed in 29 % (31/108) of the water samples, with concentrations of up to 10³ genome copies/liter. The natural occurrence of infectious HAdV was demonstrated by Integrated Cell Culture-PCR (ICC-PCR). This study confirms the suitability of using the detection of fecal-oral transmitted viruses as a marker of human fecal contamination in water matrices and indicates the spread of pathogenic viruses occurring in an alleged area of environmental protection.     

First nonavian dinosaur from Lebanon: a brachiosaurid sauropod from the Lower Cretaceous of the Jezzine District

Two sauropod teeth from an Early Cretaceous (Neocomian) fluviodeltaic sandstone near Jezzine (Southern Lebanon) are the first nonavian dinosaur remains to be reported from Lebanon. Their distinctive character places them within Brachiosauridae. The sauropod teeth from Lebanon are a significant addition to the very scanty dinosaur record from the Levant, which hitherto consisted mainly of very poorly preserved and not easily identifiable specimens. The Basal Cretaceous Sandstone of Lebanon, thus, appears to be a potentially important source of fossil vertebrate material.     

Dye-sensitized photodegradation of the fungicide carbendazim and related benzimidazoles

The present work studies the visible-light-promoted photodegradation of the colorless fungicide carbendazim (methyl 2-benzimidazolecarbamate) and several 2-substituted benzimidazoles (SBZ's), in water or water-methanol solution, in the presence of air and, as a photosensitizer, the synthetic xanthene dye Rose Bengal (RB) or the natural pigment riboflavin (Rf). The results indicate that the degradation of each particular SBZ depends on its chemical structure and on the sensitizer employed. In the presence of RB, the degradation always operates via a singlet molecular oxygen (O(2)((1)Delta(g)))-mediated mechanism, through a highly efficient process, as deduced from the comparison of the rate constants for physical and chemical quenching of O(2)((1)Delta(g)). In the presence of Rf, the visible-light irradiation of any of the studied SBZ's produces a series of competitive processes that depend on the relative concentrations of Rf and SBZ. These processes include the quenching of excited singlet and triplet Rf states by the SBZ and the generation of both O(2)((1)Delta(g)) and superoxide radical anion (O(2)(-)), the latter generated by electron transfer from excited Rf species to the dissolved oxygen. The overall result is the photodegradation of the SBZ and the photoprotection of the sensitizer.     

Trace metals in arcid clam Scapharca inaequivalvis: effects of molluscan extracts on bioluminescent bacteria

The relationship between a supposed effect of molluscan extracts on bioluminescent bacteria and metal concentrations in the extracts was investigated. For this purpose a biotoxicological assay based on bioluminescent bacteria (BLB) and extracts from metal exposed molluscs, Scapharca inaequivalvis, was optimized to monitor Cd and Cu marine pollution. Cu and Cd concentrations increased in tissues of experimentally exposed molluscs. Molluscan extracts inhibited the bacterial luminescence, the inhibition decreasing as the time of mollusc exposure to metals increased, suggesting a reduction of the "bioactive" metals. In regard to the use of BLB test in environmental monitoring, the analysis of Cu, Cd, and metallothionein (MT) was first performed in tissues from molluscs collected in three different areas of Northern Adriatic Sea. Metal concentrations reached maximum values in the gills, while Cd was mostly bound to MT in the kidney. Significant differences in metals and MT concentrations were found depending on the sampling sites. The biotoxicological assay resulted slightly correlated with the biochemical parameters.     

Geochemistry of leachates from the El Fraile sulfide tailings piles in Taxco, Guerrero, southern Mexico

Leachates from the El Fraile tailings impoundment (Taxco, Mexico) were monitored every 2 months from October 2001 to August 2002 to assess the geochemical characteristics. These leachates are of interest because they are sometimes used as alternative sources of domestic water. Alternatively, they drain into the Cacalotenango creek and may represent a major source of metal contamination of surface water and sediments. Most El Fraile leachates show characteristics of Ca–SO₄, (Ca+Mg)–SO₄, Mg–SO₄ and Ca–(SO₄+HCO₃) water types and are near-neutral (pH=6.3–7.7). Some acid leachates are generated by the interaction of meteoric water with tailings during rainfall events (pH=2.4–2.5). These contain variable levels of SO₄ ²⁻ (280–29,500 mg l⁻¹) and As (<0.01–12.0 mg l⁻¹) as well as Fe (0.025–2352 mg l⁻¹), Mn (0.1–732 mg l⁻¹), Zn (<0.025–1465 mg l⁻¹) and Pb (<0.01–0.351 mg l⁻¹). Most samples show the highest metal enrichment during the dry seasons. Leachates used as domestic water typically exceed the Mexican Drinking Water Guidelines for sulfate, hardness, Fe, Mn, Pb and As, while acidic leachates exceed the Mexican Guidelines for Industrial Discharge Waters for pH, Cu, Cd and As. Speciation shows that in near-neutral solutions, metals exist mainly as free ions, sulfates and bicarbonates, while in acidic leachates they are present as sulfates and free ions. Arsenic appears as As^(V) in all samples. Thermodynamic and mineralogical evidence indicates that precipitation of Fe oxides and oxyhydroxides, clay minerals and jarosite as well as sorption by these minerals are the main processes controlling leachate chemistry. These processes occur mainly after neutralization by interaction with bedrock and equilibration with atmospheric oxygen.     

Carbon budgets for catchments across a managed landscape mosaic in southeast Sweden: contributing to the safety assessment of a nuclear waste repository

Ecosystem budgets of matter contribute to the assessment of transport and accumulation of bioavailable contaminants in a landscape, since flows of matter and energy ultimately determine the rates at which contaminants will be partitioned in the environment. This study compares ecosystem properties, such as net primary production (NPP), sequestration of matter and fluxes to food sources for humans, which are of potential interest to describe fluxes and accumulation of bioavailable radionuclides in 14 catchments within a larger catchment area in southeast Sweden. The carbon budgets, used as a proxy for organic matter, are mainly based on local estimates of pools and fluxes, which have been distributed across a landscape mosaic of different vegetation types and management regimes using a geographical information system (GIS). NPP varied by a factor close to two (432 - 709 g x Cx m(-2)x y(-1)), while net ecosystem production ranged between -124 and 159 gx C x m(-2) x y (-1) for the different catchments. Carbon sequestration mainly occurred in the vegetation while the soil organic carbon pool was mainly a source of carbon. Large herbivores consumed on average 4.5 % of the above-ground green tissue production. When arable land was present in the catchment, the flux of carbon to humans was highest from crops and, in decreasing order, milk and beef, followed by the flux from hunting and berry/fungus picking. The results can be used to estimate the potential assimilation of radionuclides in vegetation and the potential exposure to humans of bioavailable radionuclides.     

Transient effect of the herbicide flazasulfuron on carbohydrate physiology in Vitis vinifera L

In the Champagne vineyard, most of the areas treated in early 2000 with the newly approved herbicide flazasulfuron had vines with altered growth and yellow leaves throughout the growing season. In order to clarify the physiological perturbations caused on the non-target grapevine and their potential consequences, C nutrition of grape plants grown in vineyards treated or not with flazasulfuron in 2000 was characterized during the following season. Vines from treated areas exhibited yellow leaves and an alteration of photosynthetic activity, characterized by declines in leaf gas exchanges (by 85%) and photosynthetic pigment concentrations (by 88%), and a marked disorganization of the leaf plastids. The herbicide also caused a decrease in leaf starch and soluble carbohydrate levels (-74% and -90%, respectively). Surprisingly, some vines re-greened after bloom, then exhibiting similar carbohydrate physiology to those grown in a non-treated area. Thus, recovery of CO(2) fixation rates, plastid ultra-structure, pigment concentrations and carbohydrate levels was found in re-greening leaves. Unlike the informations available in the literature, our results showed that flazasulfuron may be phytotoxic for grapevine. However, this toxicity was overcome the following year, indicating that vines have the potential to recover from this herbicide stress after one season.