Soil organic horizons as a major source for radiocesium biorecycling in forest ecosystems

Here we review some of the main processes and key parameters affecting the mobility of radiocesium in soils of semi-natural areas. We further illustrate them in a collection of soil surface horizons which largely differ in their organic matter contents. In soils, specific retention of radiocesium occurs in a very small number of sorbing sites, which are the frayed edge sites (FES) born out of weathered micaceous minerals. The FES abundance directly governs the mobility of trace Cs in the rhizosphere and thus its transfer from soil to plant. Here, we show that the accumulation of organic matter in topsoils can exert a dilution of FES-bearing minerals in the thick humus of some forest soils. Consequently, such accumulation significantly contributes to increasing 137Cs soil-to-plant transfer. Potassium depletion and extensive exploration of the organic horizons by plant roots can further enhance the contamination hazard. As humus thickness depends on both ecological conditions and forest management. our observations support the following ideas: (1) forest ecosystems can be classified according to their sensitivity to radiocesium bio-recycling, (2) specific forest management could be searched to decrease such bio-recycling.     

Evaluation of the Effect of Chemical or Enzymatic Synthesis Methods on Biodegradability of Polyesters

This work compares the biodegradability of polyesters produced by an esterification reaction between glycerol and oleic di-acid (D 18:1) issued from green chemical pathways, via either classical thermo-chemical methods, or an enzymatic method using the immobilized lipase of Candida antartica B (Novozym 435). An elastomeric polymer synthesized by enzymatic catalysis is more biodegradable than an elastomeric thermo-chemical polyester synthesized by a standard chemical procedure. This difference lies in percentage of the dendritic motifs, in values of the degree of substitution, and certainly in cross-links inducing an hyper-branched structure less accessible to the lipolytic enzymes in a waste treatment plant. However, when the elastomeric polymer synthesized by enzymatic catalysis is processed at high temperature as required for certain industrial applications, it presents an identical rate of biodegradation than the chemical polyester. The advantages of the thermo-chemical methods are greater speed and lower cost. Enzymatic synthesis appears be suited to producing polyesters, devoid of metallic catalysts, which must be used without processing at high temperature to keep a high biodegradability.     

Prevalence and Molecular Characterization of the Hepatitis E Virus in Retail Pork Products Marketed in Canada

Infection with the hepatitis E virus (HEV) is very common worldwide. HEV causes acute viral hepatitis with approximately 20 million cases per year. While HEV genotypes 1 and 2 cause large waterborne and foodborne outbreaks with a significant mortality in developing countries, genotypes 3 and 4 are more prevalent in developed countries with transmission being mostly zoonotic. In North America and Europe, HEV has been increasingly detected in swine, and exposure to pigs and pork products is considered to be the primary source of infection. Therefore we set out to investigate the prevalence of HEV in retail pork products available in Canada, by screening meal-size portions of pork pâtés, raw pork sausages, and raw pork livers. The presence of the HEV genomes was determined by RT-PCR and viral RNA was quantified by digital droplet PCR. Overall, HEV was detected in 47% of the sampled pork pâtés and 10.5% of the sampled raw pork livers, but not in the sampled pork sausages, and sequencing confirmed that all HEV strains belonged to genotype 3. Further phylogenetic analysis revealed that except for one isolate that clusters with subtype 3d, all isolates belong to subtype 3a. Amino acid variations between the isolates were also observed in the sequenced capsid region. In conclusion, the prevalence of HEV in pâtés and raw pork livers observed in this study is in agreement with the current HEV distribution in pork products reported in other developed countries.