Contribution of Pendant Ester Group Hydrolysis to the Erosion of Acrylic Polymers in Binders Aimed at Organotin-Free Antifouling Paints

Specific polymeric material applications as bioactive molecules delivery systems involve a strictly controlled degradation of polymer matrixes. One possibility to obtain a zero-order kinetic for small molecules release consists in a simple hydrolysis of ester groups contained in the macromolecular structure. The chemical degradation can lead to the continuous surface erosion of the formulated resins without loss of their mechanical properties and to a permanent activity of the delivery systems. Hydrolysis is a very well-known reaction in the case of organic molecules containing ester groups. The mechanism seems to be more complicated when ester groups are located in macromolecular structures. With the aim of antifouling applications, acrylic acid polymers bearing lateral ester groups of different chemical structures (hydrophilic, hydrophobic, hydrolyzable) have been prepared, characterized, and immersed in water, at pH 8, and their hydrolysis has been studied. Experimental data display two parameters, at least, which must be taken into account: the reactivity of the ester groups toward hydrolysis and the hydrophilic/hydrophobic balance of the polymer. The susceptibility of the acrylic polymers to hydrolysis has been compared to the erosion characteristics of the corresponding films. The results confirm that hydrolysis is necessary to obtain a regular degradation of the films without loss of mechanical properties. A relationship has been observed between the characteristics of hydrolysis and erosion for each studied polymer.     

Tissue distribution and bioconcentration factors of PCDD/Fs in the liver and adipose tissue following chronic ingestion of contaminated milk in rats

The aim of this study was to determine the tissue distribution of 17 PCDD/Fs following the chronic ingestion of contaminated milk in rats and to assess the "target tissue/milk" BioConcentration Factors (BCFs) of these molecules. Contaminated milk, collected in a polluted area, has been incorporated into the diet of male rats at a low dose (31 pg I-TEQ/day/rat). For this exposure, the accumulation of PCDD/Fs in target tissues (liver and adipose tissue) was limited, the tissue concentrations stabilising between 90 and 120 days of daily intake to levels close to 3 pg/g of tissue (all tissues and molecules combined). The tissue distribution seemed to be governed by the congeners properties and by the tissue characteristics. An increase in the chlorination degree of dioxins caused a decrease in their incorporation in the adipose tissue, and consequently of the BCF values. Moreover, the distribution of dioxins between hepatocytes and adipocytes differed: unlike the liver, the quantities of dioxins in the adipose tissue were significantly (P<0.05) correlated to the quantity of tissue fat. Only in the liver, the incorporation of PCDDs seemed to be facilitated when the chlorination degree of these congeners increased, the reverse phenomenon having been observed for PCDFs. However, for the same level of chlorination, the BCFs of PCDFs were 2.4 times higher than those of PCDDs in this tissue. The absence of correlation between the quantity of dioxins and that of fat and the BCFs differences of theses congeners suggested that dioxins fixation process in the liver was selective.     

Comparison of different physiological parameter responses in Lemna minor and Scenedesmus obliquus exposed to herbicide flumioxazin

The sensitivity of different physiological parameters in Scenedesmus obliquus and Lemna minor exposed to herbicide (flumioxazin) was investigated to indicate the most convenient and sensitive parameter. To assess toxicity of flumioxazin, we used a panel of biomarkers: pigment contents, chlorophyll fluorescence parameters and antioxidative enzyme activities. Algae and duckweed were exposed to 48-h IC50 for growth rate. In L. minor, the sensitivity of the parameters was as follows: QN > Oxygen emmision > phiS(PSII) > QP > phi(PSII) > CAT, GR > Pigment> APO > Growth. For S. obliquus, this ranking was as follows: CAT > Oxygen emission > QP > APO > GR > Pigment > phiS(PSII) > Growth > phi(PSII) > QN (from the greatest to the least sensitive). The results demonstrated that the observed toxicity is related not only to interspecific variations but also to the selected parameter.     

Biosensors for detection of mercury in contaminated soils

Biosensors based on whole bacterial cells and on bacterial heavy metal binding protein were used to determine the mercury concentration in soil. The soil samples were collected in a vegetable garden accidentally contaminated with elemental mercury 25 years earlier. Bioavailable mercury was measured using different sensors: a protein-based biosensor, a whole bacterial cell based biosensor, and a plant sensor, i.e. morphological and biochemical responses in primary leaves and roots of bean seedlings grown in the mercury-contaminated soil. For comparison the total mercury concentration of the soil samples was determined by AAS. Whole bacterial cell and protein-based biosensors gave accurate responses proportional to the total amount of mercury in the soil samples. On the contrary, plant sensors were found to be less useful indicators of soil mercury contamination, as determined by plant biomass, mercury content of primary leaves and enzyme activities.     

Reduction of silver solubility by humic acid and thiol ligands during acanthite (beta-Ag2S) dissolution

Precipitation of highly insoluble metal sulfide minerals like acanthite (beta-Ag2S) or red cinnabar (HgS) is in principle an effective means to reduce metal availability and toxicity in contaminated soils. Unfortunately, experiments have shown that red cinnabar may be solubilized in the presence of dissolved organic matter or thiol ligands. To determine whether the same applies to acanthite, a laboratory synthesized beta-Ag2S mineral was incubated for up to 3 weeks in the presence of KNO3, dissolved humic acids, cysteine, methionine and thiosulfate. XPS analysis identified Ag2O (52%), Ag2SO4 (8%) and Ag2S (40%) on the particle surfaces. Ag was released into solution in the presence of KNO3 and methionine, presumably from mixed-oxidation surface layers. Contrary to earlier results with cinnabar, however, humic acids reduced Ag concentrations in solution by about 75%, and cysteine and thiosulfate, each containing a free -SH functional group, almost completely suppressed Ag release into solution.     

Use of the aquatic lichen Dermatocarpon luridum as bioindicator of copper pollution: accumulation and cellular distribution tests

Laboratory experiments were conducted to investigate the potential use of the aquatic lichen Dermatocarpon luridum as bioindicator of copper pollution. Lichen thalli were exposed to 0.00, 0.25, 0.50, 0.75 and 1.00 mM copper in synthetic freshwater to solve the problems of metal bioavailability. The mineral composition of this media was prepared so that it corresponded to the ion composition of natural waters in D. luridum ecosystems. Sequential elution procedures using NiCl2 or Na2-EDTA (20 mM) were used to determine the distribution of metals at different cellular sites. The copper concentration extracted from thalli was correlated with pollution intensity, the greater correlation being with the Na2-EDTA extractant. The malondialdehyde concentration in thalli can be used as indicator of copper pollution; however, similar membrane degradation was observed for 0.25 and 0.50 mM copper and for 0.75 and 1.00 mM copper.     

Temperature dependence of Henry's law constants of metolachlor and diazinon

A dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube has been used to determine experimentally the Henry's law constants (HLC) of two pesticides: metolachlor and diazinon. The measurements were conducted over the temperature range 283-301 K. At 293 K, HLCs values are (42.6+/-2.8) x 10(3) (in units of M atm(-1)) for metolachlor and (3.0+/-0.3)x10(3) for diazinon. The obtained data were used to derive the following Arrhenius expressions: HLC=(3.0+/-0.4) x 10(-11) exp((10,200+/-1,000)/T) for metolachlor and (7.2+/-0.5) x 10(-15) exp((11,900+/-700)/T) for diazinon. At a cumulus cloud temperature of 283 K, the fractions of metolachlor and diazinon in the atmospheric aqueous phase are about 57% and 11% respectively. In order to evaluate the impact of a cloud on the atmospheric chemistry of both studied pesticides, we compare also their atmospheric lifetimes under clear sky (tau(gas)), and cloudy conditions (tau(multiphase)). The calculated multiphase lifetimes (in units of hours) are significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): metolachlor, 0.4 (2.9); diazinon, 1.9 (5.0).     

Trade-offs and performances of a range of alternative global climate architectures for post-2012

Quantitative assessments help to highlight the main features of climate policies by better identifying their strengths and weaknesses. In this study, we develop a grading system for assessing thirteen proposals for post-2012 climate policy. We believe that these proposals contain appropriate policy instruments which will be considered for discussions about how to design the post-2012 climate agreement. Our grades are based on four criteria: environmental effectiveness, cost effectiveness, distributional considerations and institutional feasibility. We analyze the grades with two complementary methods: principal component and cluster analysis. Our results entail three policy implications. Firstly, the higher the number of policy instruments a proposal comprises, the more difficult might be its implementation. Secondly, proposals which include a meaningful effort by the U.S. tend to fail in environmental effectiveness and institutional feasibility. Thirdly, we identify that the “first best” and the “second best” approaches belong to a stable policy group, and both may be considered as suitable candidates for post-2012 climate policy.     

Gaseous emissions from weaned pigs raised on different floor systems

Gaseous emissions from agriculture contribute to a number of environmental effects. Carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) are greenhouse gases taking part to the global problem of climate change. Ammonia (NH₃) emissions are responsible of soil acidification and eutrophication and contribute also to indirect emissions of N₂O. This work evaluated the influence of the type of floor on the emissions of these gases in the raising of weaned pigs. Two trials were carried out. In the first trial, the animals were kept either on fully slatted floor or on straw-based deep litter and, in the second one, either on fully slatted floor or on sawdust-based deep litter. For each trial and on each type of floor, 2 successive batches of weaned pigs were raised without changing the litter or emptying the slurry pit between the 2 batches. The rooms were automatically ventilated to maintain a constant ambient temperature.The performance of the animals was not significantly different according to the floor type. In trial 1, the nitrogen contents of the straw deep litter (including the substrate) and slurry were respectively 276 and 389 g pig⁻¹. In trial 2, the sawdust deep litter and slurry nitrogen contents were respectively 122 and 318 g pig⁻¹.Raising pigs on straw deep litter produced proportionately around 100% more NH₃ than raising pigs on slatted floor (0.61 g NH₃-N d⁻¹ pig⁻¹ vs. 0.31 g NH₃-N d⁻¹ pig⁻¹; P < 0.05). Differences in CO₂, H₂O and CH₄ emissions were not significant between systems. Raising pigs on sawdust deep litter produced also proportionately more NH₃ (+52%; 0.55 g NH₃-N d⁻¹ pig⁻¹ vs. 0.36 g NH₃-N d⁻¹ pig⁻¹; P < 0.01) but also more CO₂ (+25%; 427 g d⁻¹ pig⁻¹ vs. 341 g d⁻¹ pig⁻¹; P < 0.001) and H₂O (+65%; 981 g d⁻¹ pig⁻¹ vs. 593 g d⁻¹ pig⁻¹; P < 0.001) and less CH₄ (−40%; 0.52 g d⁻¹ pig⁻¹ vs. 0.86 g d⁻¹ pig⁻¹; P < 0.001) than raising pigs on slatted floor. Practically no N₂O emission was observed from rooms with slatted floor while the N₂O emissions were 0.03 and 0.32 g N₂O-N d⁻¹ pig⁻¹ for the straw and sawdust deep litter respectively. The warming potential of the greenhouse gases (N₂O + CH₄), were about 22, 34 and 168 g CO₂ equivalents per day and per pig on fully slatted floor, straw or sawdust deep litter respectively.In conclusion, pollutant gas emissions from rearing of weaned pig seem lower with fully slatted plastic floor system than with deep litter systems.     

Detection and Phylogenetic Analysis of the Hepatitis E Virus in a Canadian Swine Production Network

Viral contamination along the production chain is a significant concern in both food safety and livestock health. Pigs have been reported to act as a reservoir for zoonotic viruses, sometimes emerging ones, and epidemiological studies have shown direct links between the consumption of uncooked pork offal and cases of hepatitis caused by the hepatitis E virus (HEV) genotype 3 in humans. The presence of HEV in swine herds has been reported, but its dissemination in pork production environments is still unknown. To investigate viral contamination sources in the swine industry, 452 environment and fecal samples, including samples from livestock transportation vehicles, were collected over a period of 11 months from ten farms and one slaughterhouse that together represent a single production network. Hepatitis E virus RNA was detected by nested RT-PCR in 32 samples from both inside and outside farm buildings, on trucks, and, mostly, from fomites collected in the slaughterhouse yard, such as on a utility vehicle. Phylogenetic analysis showed a wide diversity of HEV genotype 3 strains, similar to human and swine strains previously found. According to the results of this study, the movements of trucks and utility vehicles might play an important role in HEV dissemination on a slaughterhouse site and throughout an entire network.