Assessment of aliphatic-aromatic copolyester biodegradable mulch films. Part II: laboratory simulated conditions

In a previous paper, we demonstrated that the main mechanism of degradation of poly(butylene adipate-co-terephthalate) (PBAT) biodegradable mulch films when exposed to field conditions was crosslinking due to the photodegradation from solar radiation. The aim of this work was to determine the effect of crosslinking on the biodegradability of PBAT samples. PBAT films were subjected to UV photodegradation in laboratory simulated conditions to investigate the effects of crosslinking and other major changes in the structure and mechanical properties of the films. Crosslinking caused the films to become more brittle and produced a reduction of the tensile strength and percent elongation. Besides the crosslinking degradation mechanism, chain scission also occurred in the samples. After 45d of biodegradation test, the non-crosslinked PBAT sample reached 60% of mineralization. However, the percent mineralization was reduced when samples were crosslinked. The percent mineralization of samples with 10%, 30%, 50%, and 70% gel content was 36%, 43%, 21%, and 24%, respectively. Our results indicate that crosslinking is a key process underlying the degradation of the PBAT film and did affect the biodegradability of the films, since the samples with greater amount of gel content generally showed less percent mineralization in the biodegradation tests.     

Impact of Fungal Extracts on the Physical and Antioxidant Properties of Bioactive Films Based on Enzymatically Hydrolyzed Yeast Cell Wall

Journal of Polymers and the Environment - Bioactive packaging is gaining interest in food preservation as an alternative to the incorporation of additives to food formulations. Yeast cell wall is a...     

Global mismatches in aboveground and belowground biodiversity

Human activities are accelerating global biodiversity change and have resulted in severely threatened ecosystem services. A large proportion of terrestrial biodiversity is harbored by soil, but soil biodiversity has been omitted from many global biodiversity assessments and conservation actions, and understanding of global patterns of soil biodiversity remains limited. In particular, the extent to which hotspots and coldspots of aboveground and soil biodiversity overlap is not clear. We examined global patterns of these overlaps by mapping indices of aboveground (mammals, birds, amphibians, vascular plants) and soil (bacteria, fungi, macrofauna) biodiversity that we created using previously published data on species richness. Areas of mismatch between aboveground and soil biodiversity covered 27% of Earth's terrestrial surface. The temperate broadleaf and mixed forests biome had the highest proportion of grid cells with high aboveground biodiversity but low soil biodiversity, whereas the boreal and tundra biomes had intermediate soil biodiversity but low aboveground biodiversity. While more data on soil biodiversity are needed, both to cover geographic gaps and to include additional taxa, our results suggest that protecting aboveground biodiversity may not sufficiently reduce threats to soil biodiversity. Given the functional importance of soil biodiversity and the role of soils in human well-being, soil biodiversity should be considered further in policy agendas and conservation actions by adapting management practices to sustain soil biodiversity and considering soil biodiversity when designing protected areas.     

Solid-phase fluorescence spectroscopy to characterize organic wastes

The production of solid organic waste (SOW) such as sewage sludge (SS) or municipal solid waste (MSW) has been continuously increasing in Europe since the beginning of the 1990'. Today, the European Union encourages the stabilization of these wastes using biologic processes such as anaerobic digestion and/or composting to produce bio-energy and organic fertilizers. However, the design and management of such biologic processes require knowledge about the quantity and quality of the organic matter (OM) contained in the SOW. The current methods to characterize SOW are tedious, time-consuming and often insufficiently informative. In this paper, we assess the potential of solid-phase fluorescence (SPF) spectroscopy to quickly provide a relevant characterization of SOW. First, we tested well known model compounds (tryptophan, bovine serum albumin, lignin and humic acid) and biologic matrix (Escherichia coli) in three dimensional solid-phase fluorescence (3D-SPF) spectroscopy. We recorded fluorescence spectra from proteinaceous samples but we could not record the fluorescence emitted by lignin and humic acid powders. For SOW samples, fluorescence spectra were successfully recorded for MSW and most of its sub-components (foods, cardboard) but impossible for SS, sludge compost (SC) and ligno-cellulosic wastes. Based on visual observations and additional assays, we concluded that the presence of highly light-absorptive chemical structures in such dark-colored samples was responsible for this limitation. For such samples, i.e. lignin, humic acid, SS, SC and ligno-cellulosic wastes, we show that laser induced fluorescence (LIF) spectroscopy enables the acquisition of 2D fluorescence spectra.     

Alkylphenolic compounds and bisphenol A contamination within a heavily urbanized area: case study of Paris

This study evaluates the influence of a heavily urbanized area (Paris Metropolitan area), on receiving water contamination by both bisphenol A (BPA) and alkylphenol ethoxylate (APE) biodegradation product. The study began by investigating concentrations within urban sources. In addition to the more commonly studied wastewater treatment plant effluent, wet weather urban sources (including combined sewer overflows, urban runoff, and total atmospheric fallout) were considered. The initial results highlight a significant contamination of all urban sources (from a few nanograms per liter in atmospheric fallout to several micrograms per liter in the other sources) with clearly distinguishable distribution patterns. Secondly, concentration changes along the Seine River from upstream of the Paris Metropolitan area to downstream were investigated. While the concentrations of BPA and nonylphenoxy acetic acid (NP₁EC) increase substantially due to urban sources, the 4-nonylphenol concentrations remain homogeneous along the Seine. These results suggest a broad dissemination of 4-nonylphenol at the scale of the Seine River basin. Moreover, the relationship between pollutant concentrations and Seine River flow was assessed both upstream and downstream of the Paris conurbation. Consequently, a sharp decrease in dissolved NP₁EC concentrations relative to Seine River flow underscores the influence of single-point urban pollution on Seine River contamination. Conversely, dissolved 4-nonylphenol concentrations serve to reinforce the hypothesis of its widespread presence at the Seine River basin scale.     

Evaluation of the reaction artifacts in an annular denuder-based sampler resulting from the heterogeneous ozonolysis of naphthalene

The heterogeneous ozonolysis of naphthalene adsorbed on XAD-4 resin was studied using an annular denuder technique. The experiments involved depositing a known quantity of naphthalene on the XAD-4 resin and then measuring the quantity of the solid naphthalene that reacted away under a constant flow of gaseous ozone (0.064 to 4.9 ppm) for a defined amount of time. All experiments were performed at room temperature (26 to 30 °C) and atmospheric pressure. The kinetic rate coefficient for the ozonolysis reaction of naphthalene adsorbed on XAD-4 resin is reported to be (10.1?±?0.4)?×?10^?19 cm³ molecule^?1 s^?1 (error is 2σ, precision only). This value is five times greater than the currently recommended literature value for the homogeneous gas phase reaction of naphthalene with ozone. The obtained rate coefficient is used to evaluate reaction artifacts from field concentration measurements of naphthalene, acenaphthene, and phenanthrene. The observed uncertainties associated with field concentration measurements of naphthalene, acenaphthene, and phenanthrene are reported to be much higher than the uncertainties associated with the artifact reactions. Consequently, ozone reaction artifact appears to be negligible compared to the observed field measurement uncertainty results.     

The length of growing season and adult sex ratio affect sexual size dimorphism in moose

While factors affecting body growth have been extensively studied, very little is known about the factors likely to affect the sexual size dimorphism (SSD) in polygynous mammals. Based on the carcass mass of 24420 male and female moose recorded in 14 Norwegian populations, we examine three hypotheses to explain geographical variation in SSD. First, SSD is expected to decrease when the relative density of animals (for a given habitat quality) increases, because resource limitation at high population densities is assumed to affect body growth of males more than females. Second, because males are selected to invest in growth more than females, environmental seasonality and related improvement of the forage quality during the short and intense growing season are expected to increase SSD. Third, by decreasing the proportion of adult males in the population, resulting in start of rutting earlier in life, hunting may decrease the SSD by increasing the reproductive cost of young males. We found that males grew faster and for a longer time of their life than did females and thus were heavier (-24%) when they reached adulthood. Sexual size dimorphism was independent of density but was higher in areas with short growing seasons. The low SSD in populations with largely adult female-biased sex ratios (males per female) shows that male body growth decreases with a decreasing proportion of adult males in the population. Our results indicate that geographical variation in moose SSD is influenced by divergent responses in the sexes to ecological factors affecting body growth.     

Sampling and analytical methodology development for the determination of primary and secondary low molecular weight amines in ambient air

In this project, a sampling device and an analytical method have been developed to simultaneously analyse the most frequently found low molecular weight amines, including aliphatic, aromatic and alcohol amines. These amines are diethanolamine, ethanolamine, methylamine, isopropylamine, morpholine, dimethylamine, and aniline. A sampling device was developed using a 37 mm cassette with glass fibre filters impregnated with sulfuric acid. Immediately after sampling, the filter was transferred to vials containing a solution of dansyl chloride. Dansyl chloride was used for derivatisation because it forms aromatic sulfonamides that are fluorescent and easy to protonate for MS detection. The effect of using an internal standard made with the dansylated derivative of 1-(2-methoxyphenyl)piperazine (MOPIP) on the uncertainty and efficiency of the method was also evaluated. This internal standard was spiked directly onto filters. The coupling of HPLC/ESI-MS was used for the simultaneous analysis of all the derivatives. This method showed detection limits of about 0.03 microg mL(-1) to 0.3 microg mL(-1) of amine with an average expanded uncertainty of 3% to 6% depending on the amine. The methodology recoveries are close to 100% for all the amines, and the overall estimated expanded uncertainties vary between 10% and 13% depending on the amine. This new strategy will be useful in evaluating workplace air since a unique sampling system will be used, independent of the amine to be quantified.     

Scaling the quality of teammates' mental models: equifinality and normative comparisons

We tested the impact of teammates' team and task mental model sharedness on team processes and performance using 70 undergraduate teams that completed a series of missions on a PC‐based flight simulator. Moreover, we considered how the quality of mental models might moderate such relationships. Team processes were found to partially mediate the relationship between task mental model sharedness and team performance. Although team mental model sharedness failed to exhibit a significant linear relationship with team processes or performance, it did evidence a multiplicative relationship as moderated by the quality of those models. Team processes and performance were better among teams sharing higher‐quality team mental models than among teams evidencing less sharedness or who had lower‐quality models. Again, team processes partially mediated these relationships. Results are discussed in terms of the equifinality of mental model quality and applications to various team environments. Copyright © 2005 John Wiley & Sons, Ltd.     

Assessment of aliphatic-aromatic copolyester biodegradable mulch films. Part I: field study

The objective of this work was to study the use of new biodegradable films in agriculture under open field conditions. Three biodegradable mulch films made from modified biodegradable polyester of different thicknesses and colors (black and white) and a conventional low density polyethylene (LDPE) mulch film were used to cover the beds of tomato plants. Changes in physical appearance of the films were recorded as well as changes in their mechanical, optical, and physical properties. Once tomato harvest was completed, the conventional LDPE mulch film was removed and all the tomato plants were cut using a mower. The biodegradable mulch films were plowed into the soil. The change in the appearance of the film was recorded and samples of each film after plowing were characterized according to the properties mentioned above. After the biodegradable films photodegraded, cross-link formation occurred within the films which promoted brittleness. Titanium dioxide, an additive used to produce white color in the films, catalyzed the photodegradation, while carbon black used for black color stabilized the photodegradation. The white films started to degrade after two weeks while it took about eight weeks for the black films to significantly degrade. The black biodegradable film seems to be a more promising alternative as a mulch film because of the comparable yields and weed suppression ability to conventional mulch film.