Study of metabolites from the degradation of polycyclic aromatic hydrocarbons (PAHs) by bacterial consortium enriched from mangrove sediments

The PAH metabolites produced during degradation of fluorene, phenanthrene and pyrene by a bacterial consortium enriched from mangrove sediments were analyzed using the on-fiber silylation solid-phase microextraction (SPME) combining with gas chromatography–mass spectrometry (GC–MS) method. Seventeen metabolites at trace levels were identified in different PAH degradation cultures based on the full scan mass spectra. In fluorene degradation cultures, 1-, 2-, 3- and 9-hydroxyfluorene, fluorenone, and phthalic acid were detected. In phenanthrene and pyrene degradation cultures, various common metabolites such as phenanthrene and pyrene dihydrodiols, mono-hydroxy phenanthrene, dihydroxy pyrene, lactone and 4-hydroxyphenanthrene, methyl ester, and phthalic acid were found. The detection of various common and novel metabolites demonstrates that SPME combining with GC–MS is a quick and convenient method for identification as well as monitoring the real time changes of metabolite concentrations throughout the degradation processes. The knowledge of PAH metabolic pathways and kinetics within indigenous bacterial consortium enriched from mangrove sediments contributes to enhance the bioremediation efficiency of PAH in real environment.     

Influence of hydrology on heavy metal speciation and mobility in a Pb-Zn mine tailing

Among the inorganic toxicants of greatest concern in mine tailings, Pb, Zn, Cu, Cd and As figure prominently due to their abundance and potential toxicity. Here we report on their biolability and solid-phase speciation in two sediment cores subject to variable hydrological regimes at an abandoned pyritic mine tailing. The oxic conditions of well-drained sediments induced pyrite oxidation and the subsequent liberation of H+, SO4(2-) and considerable quantities of Fe(III), which precipitated as goethite. Solubility of Pb, Zn, Cu and Cd was closely coupled to pH and goethite presence. Metal lability was particularly low in zones of neutralization, formed by the accumulation of calcite, first carried then deposited by percolating waters in both saturated and unsaturated cores. We conclude that differential hydrology induces variable heavy metal speciation and biolability in Pb-Zn mine tailings, and suggest that site-specific risk assessments must account for past and present hydrological regimes.     

Effects of bacterial inoculum and moisture adjustment on composting of pig manure

Spent litter (a mixture of partially composted pig manure and sawdust) was taken from pig pens employing the pig-on-litter system with and without the addition of a commercial bacterial product (Odor control (OC)-organic fertilizers (OF)). A duplicate series of windrows was set up with spent litter which contained the bacterial product and a further duplicate series was set up with spent litter which did not contain the bacterial product. All four sets had their initial moisture content adjusted to 60% but one of each duplicate pair had its moisture content adjusted to 60% during the entire period of further composting in windrows. The rate of further (windrow) composting was significantly different in the litter which contained no bacterial product and which only had its moisture content adjusted at the beginning of the experiment. Decomposition was incomplete in this set even after day 91. In the three other sets, the rate of decomposition was faster and the spent litter became stabilised by day 56. This result suggests that if the bacterial product has been added during the initial pig-on-litter composting process, moisture adjustment during further (windrow) composting is not important. Conversely, if moisture was adjusted during further composting, the addition of bacterial product during initial pig-on-litter composting would be of no value. Such a finding is of remarkable significance in the further composting of spent litter since this indicates that the process could be run on a much more economical basis.     

Negative effects of humic acid addition on phytoremediation of pyrene-contaminated sediments by mangrove seedlings

Vegetated (with Kandelia candel seedlings) and non-vegetated mangrove microcosms were employed to remove pyrene from contaminated sediments, and the effects of adding 6.7% humic acid (HA) on such removal were investigated. At the end of 6-month treatment, residual pyrene concentrations in surface sediments (0-2 cm) of the contaminated microcosms reduced from an initial 5.82 to 0.63 microg g(-1) dw, and the reduction was less in HA amended microcosms with the residual pyrene concentration remained at 3.12 microg g(-1) dw. The pyrene removal percentages in microcosms with HA amendment were 29% for surface aerobic sediments and 41% for bottom (anaerobic) sediments, while the respective removal percentages in microcosms without HA amendment were 89% (surface sediments) and 53% (bottom sediments). Microcosms planted with K. candel seedlings had a significantly higher pyrene removal when compared to the non-vegetated ones, and the average removal percentages were 70.9% and 61.4%, respectively. However, when humic acid was added, no significant difference was found between vegetated and non-vegetated microcosms in pyrene removal, both had less than 40% removal, probably because plant growth in humic acid amended contaminated microcosms, in terms of total biomass, was reduced by 50%. Roots of K. candel could accumulate pyrene from contaminated microcosms, and pyrene concentrations in roots harvested from microcosms with and without humic acid addition were 6.01 and 3.46 microg g(-1) dw, respectively. These results suggest that the addition of HA to contaminated sediments decreased the mangrove microcosm's ability to remove pyrene as pyrene was more tightly bound to the organic matter and plant growth was reduced.     

Effects of composting on phytotoxicity of spent pig-manure sawdust litter

The phytotoxicity of spent pig-manure sawdust litter (spent litter) was evaluated during further composting. Aqueous extracts of the spent litter were prepared by shaking the sample with water (1:10 w/v), and the toxicity of these extracts was determined on relative seed germination, relative root elongation and germination index (GI, a factor of relative seed germination and relative root elongation). The sensitivity of six plant species, namely Brassica parachinensis (Chinese cabbage), Brassica albogalera (Chinese kale), Allium sativum (onion), Cucumis sativus (cucumber), Amaranthus espinosus (Chinese spinach), and Lycopersicon esculentum (tomato) were compared. The effect of different moisture levels during composting on the phytotoxicity of the spent litter was also examined. Phytotoxicity of the spent litter was only evident during the earlier stage of composting (first 14 days) and, that seed germination and root elongation reached 100% (same as the control) towards the end of the composting. The concentrations of the major inhibitors, water-extractable Cu and Zn, and NH4(+)-N of the spent litter, declined during composting, indicating that these inhibitors were gradually eliminated as composting proceeded. Multiple regression analysis showed that the NH4(+)-N content of the spent litter was the most important chemical factor affecting phytotoxicity of the plant species selected for this study. Relative root elongation and GI were more sensitive indicators of phytotoxicity than seed germination. In the present study, the GI's of all plant species were >80% at day 60, indicating that the spent litter had reached its maturation by day 60. The responses of different plant species to the water-extracts of the spent litter were different. Among the six species, Chinese cabbage and Chinese spinach were the most sensitive species, and tomato and cucumber were the least sensitive species to indicate phytotoxicity of the spent litter. Moisture adjustment during the composting process did not affect the results of the phytotoxicity test.     

Radon concentration measurements in mofettes from Harghita and Covasna counties, Romania

In the Harghita volcanic range (Romania) there are many occurrences of dry CO(2) emanations, called mofettes. The emanating gas with high carbon dioxide content has a proved curative effect. The gas also contains important quantities of radon. Since the mofettes are used in curative purposes in several illnesses, in most of the cases without medical supervising, has been proposed to determine the radon activity concentration in some of the most frequented mofettes from Romania. The seasonal variations have also been monitored and were calculated the effective doses received by the patients during a cure. The radon activity concentrations' levels above the mofettes indoor air range between 548 and 10 717Bq/m(3) while within the gas pools' values between 3210 and 32 781Bq/m(3) have been measured. The effective dose received by the patients during a cure is between 0.0086 and 0.16mSv. No major seasonal variations of the radon activity concentrations levels have been pointed out so far in the studied mofettes.     

Numerical simulation of propane detonation in medium and large scale geometries

A modelling strategy has been developed for consequence analysis of medium and large scale gaseous detonation. The model is based on the solution of Euler equations with one-step chemistry. The Van Leer flux limited method which is a total variation diminishing scheme is used for shock capturing. Preliminary calculations were firstly conducted for small domains with fine grids which resolve the wave, relatively coarse grids which have less than 10 grids across the wave and coarse grids in which the minimum grid size is larger than the wave thickness to ensure that the reaction scheme has been properly tuned to capture the correct detonation pressure, temperature and velocity in the resolutions used in the different cases. The model was firstly tested against a medium scale detonation test in a shock tube with U-bends. Reasonably good agreement is achieved on detonation pressure and mean shock wave velocities at different measuring segments of the tube. Following the validation, the detonation of a hypothetical planar propane-air cloud is simulated. The predictions uncovered some interesting features of such large scale detonation phenomena which are of significance in the safety context, especially for accidental investigations. The findings from the present analysis are in line with the forensic evidence on damages in some historic accidents and challenges previous analysis of a major accident in which forensic evidence suggested localised detonation but was considered as the consequence of fire storms by the investigation team.     

Fetal hydrops caused by a novel pathogenic MECOM variant

We report a fetus with hydrops, congenital heart disease and bilateral radioulnar synostosis caused by a novel pathogenic MECOM variant. The female fetus was referred for post-mortem examination after fetal hydrops and intrauterine death was diagnosed at 20 weeks gestation. Post-mortem examination confirmed fetal hydrops, pallor, truncus arteriosus and bilateral radioulnar synostosis. Trio whole genome sequencing analysis detected a novel de novo heterozygous pathogenic loss-of-function variant in MECOM (NM_004991), associated with a diagnosis of Radioulnar Synostosis with Amegakaryocytic Thrombocytopenia 2 (RUSAT-2). RUSAT-2 is a variable condition associated postnatally with bone marrow failure, radioulnar synostosis and congenital anomalies. RUSAT-2 is not currently associated with a prenatal phenotype or fetal demise, and was not present on diagnostic NHS prenatal gene panels at time of diagnosis. This case highlights the diagnostic value of detailed phenotyping with post-mortem examination, and of using a broad sequencing approach.