Soils have been sampled in the vicinity of the Tomsk-Seversk facility (Siberia, Russia) that allows us to measure radioactive contaminations due to atmospheric and aquatic releases. Indeed soils exhibit large inventories of man-made fission products including 137Cs (ranging from 33,000 to 68,500 Bq m(-2)) and actinides such as plutonium (i.e. 239+240Pu from 420 to 5900 Bq m(-2)) or 241Am (160-1220 Bq m(-2)). Among all sampling sites, the bank of the Romashka channel exhibits the highest radioisotope concentrations. At this site, some short half-life gamma emitters were detected as well indicating recent aquatic discharge in the channel. In comparison, soils that underwent atmospheric depositions like peat and forest soils exhibit lower activities of actinides and 137Cs. Soil activities are too high to be related solely to global fallout and thus the source of plutonium must be discharges from the Siberian Chemical Combine (SCC) plant. This is confirmed by plutonium isotopic ratios measured by ICP-MS; the low 241Pu/239Pu and 240Pu/239Pu atomic ratios with respect to global fallout ratio or civil nuclear fuel are consistent with weapons grade signatures. Up to now, the influence of Tomsk-Seversk plutonium discharges was speculated in the Ob River and its estuary. Isotopic data from the present study show that plutonium measured in SCC probably constitutes a significant source of plutonium in the aquatic environment, together with plutonium from global fallout and other contaminated sites including Tomsk, Mayak (Russia) and Semipalatinsk (Republic of Kazakhstan). It is estimated that the proportion of plutonium from SCC source can reach 45% for 239Pu and 60% for 241Pu in the sediments. 相似文献
Human noroviruses are a major cause for gastroenteritis outbreaks. Filter-feeding bivalve molluscs, which accumulate noroviruses in their digestive tissues, are a typical vector for human infection. RT-qPCR, the established method for human norovirus detection in food, does not allow discrimination between infectious and non-infectious viruses and can overestimate potentially infectious viral loads. To develop a more accurate method of infectious norovirus load estimation, we combined intercalating agent propidium monoazide (PMAxx™)-pre-treatment with RT-qPCR assay using in vitro-cultivable murine norovirus. Three primer sets targeting different genome regions and diverse amplicon sizes were used to compare one-step amplification of a short genome fragment to three two-step long-range RT-qPCRs (7 kbp, 3.6 kbp and 2.3 kbp amplicons). Following initial assays performed on untreated infectious, heat-, or ultraviolet-inactivated murine noroviruses in PBS suspension, PMAxx™ RT-qPCRs were implemented to detect murine noroviruses subsequent to their extraction from mussel digestive tissues; virus extraction via anionic polymer-coated magnetic beads was compared with the proteinase K-dependent ISO norm. The long-range RT-qPCR process detecting fragments of more than 2.3 kbp allowed accurate estimation of the infectivity of UV-damaged murine noroviruses. While proteinase K extraction limited later estimation of PMAxx™ pre-treatment effects and was found to be unsuited to the assay, magnetic bead-captured murine noroviruses retained their infectivity. Genome copies of heat-inactivated murine noroviruses differed by 2.3 log10 between RT-qPCR and PMAxx™-RT-qPCR analysis in bivalve molluscs, the PMAxx™ pre-treatment allowing a closer approximation of infectious titres. The combination of bead-based virus extraction and PMAxx™ RT-qPCR thus provides a more accurate model for the estimation of noroviral bivalve mollusc contamination than the conjunction of proteinase K extraction and RT-qPCR and has the potential (once validated utilising infectious human norovirus) to provide an added measure of security to food safety authorities in the hazard assessment of potential bivalve mollusc contamination.
• The promoting effects for VFA generation follow the order of APG>SDBS>HTAB.• Surfactants improve the WAS solubilization/hydrolysis and acidification processes.• The VFA promotion is associated with surfactants’ distinctive characteristics.• Surfactants induce the enrichment of functional bacteria for VFA biosynthesis.• The vital genes for substrates delivery, metabolism, and VFA yields are upregulated. Surfactants were expected to exhibit positive effects on the waste activated sludge (WAS) disposal. However, the systematic comparison of different categories of surfactants on the WAS fermentation and the functional mechanisms, especially microbial metabolic traits, have not yet been precisely explored. This study revealed the positive effects of different surfactants on the volatile fatty acid (VFA) production, which followed the order of alkyl polysaccharides (APG)>sodium dodecylbenzene sulfonate (SDBS)>hexadecyl trimethyl ammonium bromide (HTAB). Mechanistic exploration found that the presence of different surfactants improved solubilization and hydrolysis steps, and then contributed to the subsequent acidification with different efficiencies. The functional microorganisms associated with VFA generation were enriched in surfactant-conditioned reactors. Metagenomic analysis further indicated that the key genes involved in the particular process of VFA generation were over-expressed. The simultaneous bioavailable substrate improvement, functional bacterial enrichment, and metabolic activity upregulation induced by different surfactants jointly contributed to VFA promotion during WAS fermentation. This study could provide a comprehensive realization of surfactants’ impacts on the WAS fermentation process, and more importantly, it reminded the public to discern the distinct interplaying effects induced by different chemicals in regulating the WAS disposal and resource recovery. 相似文献
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