Detection of Class I and II integrons for the assessment of antibiotic and multidrug resistance among Escherichia coli isolates from agricultural irrigation waters in Bulacan,Philippines

Contaminated irrigation water may greatly affect not only the quality of produce but also the people exposed to it. In this study, agricultural irrigation waters in Bulacan, Philippines were assessed and found to be contaminated with Escherichia coli (E. coli) ranging from 0.58 to 4.51 log₁₀ CFU/mL. A total of 79 isolates of E. coli were confirmed through polymerase chain reaction (PCR) amplifying the uidA gene and were tested for phenotypic resistance using 10 antimicrobials through the Kirby–Bauer disc diffusion method. Forty-six isolates (58.22%) were noted to be multidrug resistant (MDR) with high resistance rate to cephalothin, tetracycline, streptomycin, ampicillin, trimethoprim, nalidixic acid, and chloramphenicol. Moreover, this study also examined the prevalence of Class I and II integrons accounting to 67.39% and 17.39%, respectively, of the MDR E. coli strains using multiplex PCR. The results imply that the agricultural water used in Bulacan is contaminated with the fecal material of man or other animals present in the area, and the presence of MDR bacteria, which pose a potential threat to individuals in these areas, is alarming. In addition, detection of integrons could be a good marker for the identification of MDR isolates. Lastly, this study could develop strategies for the proper management of farming sites leading to the detection of food-borne pathogens and prevention of infectious diseases.     

Evaluation of ecological disturbance and intrinsic bioremediation potential of pulp mill-contaminated lake sediment using key enzymes as probes

A rapid protocol was developed to measure 10 different enzymic activities from a large number of 1-cm-sliced freshly collected lake sediments. Layers heavily polluted by organic halogens (4900 mg Cl kg(-1)) revealed severe depression of phosphatase, sulfatase, leucine-aminopeptidase, chitinase, acetate esterase and butyrate esterase activities as compared to layers above and below the most polluted zone. alpha-Glucosidase, beta-glucosidase, beta-xylosidase and palmitate esterase were less affected. Methane oxidation potential was dramatically depressed in the polluted strata whereas tetrachloromethane dehalogenating activity was observed in the polluted sediment only. The sediment layers formed after the chlorine discharges into the lake had diminished to 1/10, and showed restoration of the activities close to those observed in non-recipient sediment, in spite of the persisting presence of >1000 mg of organic chlorine (kg dry wt)(-1). We conclude that certain enzymic activities involved in breakdown or oxidation of organic matter in the sediments are useful probes for assessing the degree of ecological damage and its potential for restoration in recipient lakes of industrial discharges.     

Catalytic and electrocatalytic hydrogenolysis of brominated diphenyl ethers

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their use as additive flame-retardants. Conventional catalytic hydrogenolysis in methanol solution and electrocatalytic hydrogenolysis in aqueous methanol were examined as methods for debrominating mono- and di-bromodiphenyl ethers, as well as a commercial penta-PBDE mixture, in each case using palladium on alumina as the catalyst. Electrocatalytic hydrogenolysis employed a divided flow-through batch cell, with reticulated vitreous carbon cathodes and IrO2/Ti dimensionally stable anodes. Both methods gave efficient sequential debromination, with essentially complete removal of bromine from the PBDEs, but the electrocatalytic method was limited by the poor solubility of PBDEs in aqueous methanol.     

Aquatic fate assessment of the polycyclic musk fragrance HHCB. Scenario and variability analysis in accordance with the EU risk assessment guidelines

By means of the environmental fate and distribution models laid down in the Technical Guidance Documents (TGD) and implemented in the European Union System for the Evaluation of Substances (EUSES) environmental concentrations of the polycyclic musk fragrance HHCB (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclopenta-[g]-2- benzopyrane; trade name: e.g. Galaxolide) were calculated for the aquatic environment under consideration of various scenarios. The results were then compared to monitoring data from the region of North Rhine-Westphalia (River Ruhr). An uncertainty analysis was carried out to determine sensitive parameters, to integrate environmental variability and to confirm the model's calculations. The standard scenario of EUSES overestimates the measured concentrations, which confirms the conservative nature of the calculations. The regional-specific scenarios lead to lower deviations from the measured values than the standard scenario. Deviations range from one to two orders of magnitude in the effluent of sewage treatment plants; they amount to one order of magnitude for surface water concentrations on a local scale and conform to monitoring data on a regional scale. The use of measured bioconcentration factors for fish instead of estimated ones reduces deviations remarkably. The investigation reveals that unrealistic worst-case calculations of HHCB can at best be ameliorated by the application of more realistic emission rates and measured bioconcentration factors. The use of regional-specific parameters also diminishes the deviations of the calculations from the measured concentrations.     

Clonal variation in heavy metal accumulation and biomass production in a poplar coppice culture. II. Vertical distribution and phytoextraction potential

Short rotation coppice cultures (SRC) are intensively managed, high-density plantations of multi-shoot trees. In April 1996, an SRC field trial with 17 different poplar clones was established in Boom (Belgium) on a former waste disposal site. In December 1996 and January 2001, all shoots were cut back to a height of 5 cm to create a coppice culture. For six clones, wood and bark were sampled at the bottom, middle and top of a shoot in August and November 2002. No significant height effect of metal concentration was found, but for wood, metal concentrations generally increased toward the top of the shoot in August, and decreased toward the top of the shoot in November. Phytoextraction potential of a clone was primarily determined by metal concentration and by biomass production. Shoot size and number of shoots per stool were less important, as a high biomass production could be achieved by producing a few large shoots or many smaller shoots. Clone Fritzi Pauley accumulated 1.4 kg ha(-1) of Al over two years; Wolterson and Balsam Spire showed a relatively high accumulation of Cd and Zn, i.e. averaging, respectively 47 and 57 g ha(-1) for Cd and 2.4 and 2.0 kg ha(-1) for Zn over two years.     

Reactions of compost-derived humic substances with lead, copper, cadmium, and zinc

Thermodynamic stability constants of the formation of complexes from the reactions of humic substances with various metals are usually used as parameters to judge the reactivities of both humic substances and metals. However, in calculating the thermodynamic stability constants, complicated processes for the acquisition of activities of components in reactions are absolutely inevitable. In this study, we investigated the average conditional concentration quotients of the complexes formed from the reaction of metals with humic substances and the relations of these quotients to thermodynamic stability constants. The characterized humic substances including HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) extracted from a swine compost were prepared to react with Pb, Cu, Cd, and Zn at 25 degrees C and at pH 4.00 and 6.50. Reactions of HA (MW>1,000), FA (MW>1,000), and FA (MW<1,000) with the four metals were carried out at 1:0.1, 1:0.5, 1:1, 1:5, and 1:10 ligand:metal stoichiometry. The concentrations of the free ions of Pb, Cu, Cd, and Zn in the reaction systems of metal-HA suspensions and metal-FA solutions were measured by anodic stripping voltammetry (ASV). The sequence of the average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals was FA(MW<1,000)>FA(MW>1,000)>HA(MW>1,000), showing the relative reactivities of the fractions of swine compost-derived humic substances. The sequence of reacting metals with humic substances was Pb>Cu>Cd>Zn, which is in good agreement with the sequence reported by judging the thermodynamic stability constants. The average conditional concentration quotients of the formed complexes from the reaction of humic substances with metals were thus useful parameters that can be directly related to thermodynamic stability constants and other parameters.     

Bioassay for determining sensitivity to sulfosulfuron on seven plant species

This study presents a bioassay procedure, based on the root and shoot growth parameters, for the determination of the herbicide sulfosulfuron (1-(4,6 dimethoxypyrimidin-2-yl)-3-(2-ethylsulfonylimidazo[1,2-a]pyridin-3-ylsulfonil)urea) sensitivity on seven vegetal species. Plant response to sulfosulfuron was calculated with the equations fitted to the root growth data as a function of the logarithm of the herbicide concentration by non-linear regression and was used to calculate the doses for 10, 30 and 50% inhibition of root growth (EC10, EC30 and EC50). The results indicate that the phytotoxic effect of sulfosulfuron in all the species assayed followed the order: flax > maize > onion > vetch > lepidium sativum > tomato > barley. These species showed phytotoxicity at low levels of sulfosulfuron and flax appeared to be the most susceptible species to sulfosulfuron (0.001 mg/L).     

Interactions between copper and cadmium modify metal organ distribution in mature tilapia, Oreochromis mossambicus

Sexually mature female tilapia were exposed to sublethal concentrations of waterborne Cu and/or Cd over 6 days, and subsequent body concentrations of these metals were determined in several organs. The results show that the distribution of Cu and Cd was metal and organ specific. This is demonstrated, for example, by the observation that in tilapia, Cu exposure did not result in Cu accumulation in the liver, whereas in the intestinal wall, notably high concentrations of Cu and Cd were measured in metal exposed fish. In addition to single metal exposed fish, we also determined Cu and Cd body distribution in Cu?Cd co-exposed fish. The observed interactions in metal accumulation were most pronounced in the organs of fish exposed to low, environmentally realistic, metal concentrations.     

Afriwaste The fixation and stabilisation of hazardous waste

The disposal of hazardous and toxic wastes is an area where utmost care and responsibility needs to be exercised. A certain (and mostly acceptable) level of care and responsibility has been legislated and is in place in most developed economies (UK, USA, Canada, Europe, etc.). This is, however, generally not the case in under-developed or developing economies, South Africa being no exception. This paper reflects on various disposal methods and describes a potentially economic alternative to existing methods of the disposal of toxic and hazardous wastes. These existing methods are: Disposal in Class I landfill sites and destruction via incineration.     

Lead levels of feral pigeons (Columba livia) from Madrid (Spain)

Tissue lead data are presented for populations of feral pigeons (Columba livia) from three locations in Madrid (Spain). The lead present in the lungs and digestive tract of pigeons increased progressively with traffic density and in parallel with atmospheric and ground lead values. The contribution of the respiratory route of Pb intake to the pigeons was about three times greater than the digestive route. The highest Pb values were found in bones. It is suggested that the pigeons gave a greatly magnified picture of lead pollution in cities than indicated by atmospheric lead concentrations.