Sensitized photolysis of polychlorobiphenyls in alkaline 2-propanol: dechlorination of Aroclor 1254 in soil samples by solar radiation

Photodechlorination of Aroclor 1254 (1000 mg/L) in an alkaline 2-propanol solution at \lambda = 254 nm proceeded with a high quantum yield (\phi = 35.0) as determined by C1- release. The Aroclor was completely dechlorinated in 30 min and gave predominantly biphenyl (BP). After 20 h of solar irradiation, only partial dechlorination (25%) was observed, and no BP was formed. In the presence of phenothiazine (PT) sensitizer (5 mM) the Aroclor was completely dechlorinated to BP in 1 h at 350 nm (\phi = 2.33) and in 4 h by exposure to sunlight. Under the same conditions, Aroclor 1254 extracts of contaminated soil (730 mg/L) were dechlorinated in 2 h at 350 nm (\phi = 0.28) and in 20 h on exposure to sunlight. The photoreaction was completely quenched by oxygen and nitrobenzene (0.1 M). Moreover the Aroclor was thermally (ca. 80 "C) dechlorinated to BP using di-tert-butyl peroxide. A free-radical chain reaction was suggested in which the aryl radical anion, Ar(*-)-Cl, was a key intermediate in the dechlorination process

Acute toxicity of bismuth to the earthworm Eisenia andrei

ABSTRACT: Bismuth (Bi) is increasingly used in several industrial applications including the production of alloys, drugs, cosmetics and munitions formulations. However, little information is available on the environmental fate and ecotoxicological effects of Bi. The present study describes 14 days acute toxicity of Bi, added as Bi citrate to a natural sandy soil, to the adult earthworm Eisenia andrei. Total measured Bi concentrations were 298.0, 399.5, 431.0, and 469.5 mg Bi/kg dry soil. Data indicates that Bi was toxic to Eisenia andrei, as determined by LC50 and LOEC, i.e., 416.0 and 399.5 mg Bi/kg dry soil, respectively. At 14 days in the presence of Eisenia andrei the bioaccessible fraction of Bi in soil, as determined in KNO3 aqueous soil extracts, increased by a factor ranging from 1.6 to 30.0 compared to those measured at the beginning of experiment. Moreover, this study shows that an increase in pH caused by the presence of earthworm in soil was accompanied by increase in Bi bioaccessibility and consequently toxicity. For example, when Bi bioaccessibility increased from 0.262 to 7.516 mg Bi/kg dry soil, the mortality rate increased from 0 to 79%. Assuming that there were at least two routes by which Eisania andrei enhanced Bi bioaccessibility; one route was guided by the mobility, the biochemical (mucus) and the biological (bacteria) interactions of Eisenia andrei with soil constituents, and the other route was marked by the death of earthworms and the release of the accumulated Bi from the carcass

Dissolution of a new explosive formulation containing TNT and HMX : Comparison with octol

GIM (Greener Insensitive Material) is a new explosive formulation made of HMX(51.5%), TNT (40.7%), and a binder, ETPE (7.8%), which is currently investigated by the Canadian Department of National Defense for a wider use by the Army. In the present study, dissolution of GIM in water was measured and compared to the dissolution of octol (HMX/TNT: 70/30). Although the presence of ETPE did not prevent completely TNT and HMX from dissolving, GIM appeared to dissolve more slowly than octol. The ETPE was shown to prevent the formulation particles from collapsing and to retard the dissolution of both TNT and HMX by limiting their exposure to water. In both octol and GIM, the dissolution rate of the particles was governed by the compound(s) that are slower to dissolve, i.e. HMX in octol, and HMX and ETPE in GIM. A model based on Fick\u2019s diffusion law allowed fitting well the dissolution data of octol but was less appropriate to fit the data of GIM likely due to a physical rearrangement of the solid upon dissolution. The present findings demonstrate that ETPE in GIM decreases the risks of explosives leakage from particles of the new formulation and should facilitate the collecting of non-exploded GIM particles in training sites.Peer reviewed: YesNRC publication: Ye

Impacts of Continuous Inflow of Low Concentrations of Silver Nanoparticles on Biological Performance and Microbial Communities of Aerobic Heterotrophic Wastewater Biofilm

Attached-growth wastewater processes are currently used in water resource recovery facilities (WRRFs) for required upgrades due to an increase in influent loading or to reach more stringent discharge criteria. Yet, the distribution and long-term inhibitory effects of silver nanoparticles (AgNPs) in attached-growth biological wastewater processes and their impact on involved microbial communities are poorly understood at relevant, low concentrations. Retention, distribution, and long-term inhibitory effect of polyvinylpyrrolidone (PVP)-coated AgNPs were evaluated in bench-scale moving bed biofilm reactors (MBBRs), achieving soluble organic matter removal, over a 64 day exposure to nominal concentrations of 10 and 100 μg/L. Distributions of continuously added AgNPs were characterized in the influent, bioreactor, and effluent of MBBRs using single particle inductively coupled plasma mass spectroscopy (spICP-MS). Aerobic heterotrophic biofilms in MBBRs demonstrated limited retention capacity for AgNPs over long-term exposure, with release of AgNPs, and Ag-rich biofilm sloughed from the carriers. Continuous exposure to both influent AgNP concentrations significantly decreased soluble chemical oxygen demand (SCOD) removal efficiency (11% to 31%) and reduced biofilm viability (8% to 30%). Specific activities of both intracellular dehydrogenase (DHA) and extracellular α-glucosidase (α-Glu) and protease (PRO) enzymes were significantly inhibited (8% to 39%) with an observed NP dose-dependent intracellular reactive oxygen species (ROS) production and shift in biofilm microbial community composition by day 64. Our results indicated that long-term exposure to AgNPs in biofilm processes at environmentally relevant concentrations can impact the treatment process stability and the quality of the discharged effluent

Effect of ozonation on anaerobic digestion sludge activity and viability

The effect of ozonation of anaerobic digested sludge on methane production was studied as a means of increasing the capacity of municipal anaerobic digesters. Ozone doses ranging from 0 to 192 mg O3/g sludge COD were evaluated in batch tests with a bench scale ozonation unit. Ozonation initially, and temporarily, reduced biomass viability and acetoclastic methanogenic activity, resulting in an initial lag phase ranging from 0.8 to 10 days. Following this lag phase, ozonation enhanced methane production with an optimal methane yield attained at 86 mg O3/g COD. Under these conditions, the yield of methane and the rate of its formation were 52% and 95% higher, respectively, than those factors measured without ozonation. A required optimal ozone dose could be feasible to improve the anaerobic digestion performance by increasing the methane production potential with a minimum impact on microbial activity; thus, an optimal ozone dose would enable an increase in the capacity of anaerobic digesters

Fate of CL-20 in sandy soils : Degradation products as potential markers of natural attenuation

Hexanitrohexaazaisowurtzitane (CL-20) is an emerging explosive that may replace the currently used explosives such as RDX and HMX, but little is known about its fate in soil. The present study was conducted to determine degradation products of CL-20 in two sandy soils under abiotic and biotic anaerobic conditions. Biotic degradation was prevalent in the slightly acidic VT soil, which contained a greater organic C content, while the slightly alkaline SAC soil favored hydrolysis. CL-20 degradation was accompanied by the formation of formate, glyoxal, nitrite, ammonium, and nitrous oxide. Biotic degradation of CL-20 occurred through the formation of its denitrohydrogenated derivative (m/z 393 Da) while hydrolysis occurred through the formation of a ring cleavage product (m/z 156 Da) that was tentatively identified as CH2 N\u2013C( N\u2013NO2)\u2013CH N\u2013CHO or its isomer N(NO2) CH\u2013CH N\u2013CO\u2013CH NH. Due to their chemical specificity, these two intermediates may be considered as markers of in situ attenuation of CL-20 in soil.NRC publication: Ye

Transformation of RDX and other energetic compounds by xenobiotic reductases XenA and XenB

The transformation of explosives, including hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), by xenobiotic reductases XenA and XenB (and the bacterial strains harboring these enzymes) under both aerobic and anaerobic conditions was assessed. Under anaerobic conditions, Pseudomonas fluorescens I-C (XenB) degraded RDX faster than Pseudomonas putida II-B (XenA), and transformation occurred when the cells were supplied with sources of both carbon (succinate) and nitrogen (NH\u2084\u207a), but not when only carbon was supplied. Transformation was always faster under anaerobic conditions compared to aerobic conditions, with both enzymes exhibiting a O\u2082 concentration-dependent inhibition of RDX transformation. The primary degradation pathway for RDX was conversion to methylenedinitramine and then to formaldehyde, but a minor pathway that produced 4-nitro-2,4-diazabutanal (NDAB) also appeared to be active during transformation by whole cells of P. putida II-B and purified XenA. Both XenA and XenB also degraded the related nitramine explosives octahydro- 1,3,5,7-tetranitro-1,3,5,7-tetrazocine and 2,4,6,8,10,12- hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane. Purified XenB was found to have a broader substrate range than XenA, degrading more of the explosive compounds examined in this study. The results show that these two xenobiotic reductases (and their respective bacterial strains) have the capacity to transform RDX as well as a wide variety of explosive compounds, especially under low oxygen concentrations.NRC publication: Ye

Antigen-presenting cells transfected with Hsp65 messenger RNA fail to treat experimental tuberculosis

In the last several years, the use of dendritic cells has been studied as a therapeutic strategy against tumors. Dendritic cells can be pulsed with peptides or full-length protein, or they can be transfected with DNA or RNA. However, comparative studies suggest that transfecting dendritic cells with messenger RNA (mRNA) is superior to other antigen-loading techniques in generating immunocompetent dendritic cells. In the present study, we evaluated a new therapeutic strategy to fight tuberculosis using dendritic cells and macrophages transfected with Hsp65 mRNA. First, we demonstrated that antigen-presenting cells transfected with Hsp65 mRNA exhibit a higher level of expression of co-stimulatory molecules, suggesting that Hsp65 mRNA has immunostimulatory properties. We also demonstrated that spleen cells obtained from animals immunized with mock and Hsp65 mRNA-transfected dendritic cells were able to generate a mixed Th1/Th2 response with production not only of IFN-γ but also of IL-5 and IL-10. In contrast, cells recovered from mice immunized with Hsp65 mRNA-transfected macrophages were able to produce only IL-5. When mice were infected with Mycobacterium tuberculosis and treated with antigen-presenting cells transfected with Hsp65 mRNA (therapeutic immunization), we did not detect any decrease in the lung bacterial load or any preservation of the lung parenchyma, indicating the inability of transfected cells to confer curative effects against tuberculosis. In spite of the lack of therapeutic efficacy, this study reports for the first time the use of antigen-presenting cells transfected with mRNA in experimental tuberculosis