RESUMEN
Quality of soils of the arid zones with low organic matter can be improved through the application of natural amendments especially biochar from various available feedstocks. The objective of this study was to evaluate the impacts of corn residue and poultry manure and their biochars on soil organic carbon (SOC), hot-water soluble carbohydrates (HWSC), basal soil respiration (BSR),and structural stability determined by HEMC (high-energy moisture characteristic). A sandy loam soil in pots were thoroughly mixed with 1, 2 and 4% w/w of corn residues (CR) and poultry manure (PM) feedstock and their biochars prepared at 350 and 650 °C of slow pyrolysis. Maize seeds were planted in pots and grown until physiological maturity when soil characteristics were measured. Treatments considerably altered the means of studied soil quality indicators, and increased SOC (1.5-10 times) and HWSC (1-7 times), and HEMC indices: volume of drainable pores ratio (VDPR, 1.5- 3.5 times), and stability ratio (SR, 1-3 times). Increasing pyrolysis temperature, regardless of the type and rate of feedstock, significantly decreased the SOC, BSR and percent of water-stable aggregates, and consequently structural stability indices. Contribution of both PM feedstock and its biochars was less effective than the CR ones (particularly the biochar produced at higher pyrolysis temperature), due to elevated sodium adsorption ratio (SAR) associated with higher slaking, physico-chemical dispersion and lower aggregate and structural stability.
Asunto(s)
Carbono , Suelo , Animales , Carbón Orgánico , Pirólisis , TemperaturaRESUMEN
Knowledge of the transport and fate of pathogenic Escherichia coli, especially in the areas contaminated with crude oil, is required to assess contamination of shallow groundwater resources. The present study aims to investigate the effect of crude oil-mediated water repellency on the movement of nalidixic acid-resistant Escherichia coli strain (E. coli NAR) and bromide (Br) as an inert tracer in two soil types. The soils were contaminated at three levels of 0, 0.5 and 1% w/w of total petroleum hydrocarbons (TPHs) using crude oil. Steady-state saturated flow in the soil columns was controlled using a tension infiltrometer. Leaching experiments were conducted through the columns of repacked (un-weathered) and physically-weathered clay loam (CL) and sandy loam (SL) soils. The columns leachate was sampled at specific times for 4 pore volumes. The shape of breakthrough curves for the E. coli NAR and Br depended on soil texture and structure and the TPHs level. Preferential flow in the crude oil-mediated water-repellent soils facilitated the transport of contaminants especially E. coli NAR. Filtration coefficient and relative adsorption index of bacteria were greatest in the repacked CL soils and were lowest in the weathered SL soils. Discontinuity of soil pores and lower flow velocity resulted in greater filtration of E. coli NAR in the repacked CL soil than other treatments. Physical weathering induced the formation of aggregates which reduced soil particle surfaces available for retention of water-repellent oil and contaminants. Movement of both bacteria and Br tracer in the weathered SL soil with 1% TPHs was higher than other treatments. This finding was attributed to low specific surface area, continuity of the pores and water repellency-mediated preferential pathways in the weathered SL soil columns. Our findings implied that shallow groundwater resources could be very sensitive to microbial contamination particularly in the oil-mediated water-repellent soils.
Asunto(s)
Bromuros/metabolismo , Escherichia coli/metabolismo , Petróleo/metabolismo , Microbiología del Suelo , Contaminantes del Suelo/metabolismo , Adsorción , Bacterias/metabolismo , Biodegradación Ambiental , Filtración , Agua Subterránea , Hidrocarburos/metabolismo , Suelo/química , Contaminantes del Suelo/análisis , Tiempo (Meteorología)RESUMEN
Spreading of waste organic matter on agricultural lands is considered to enhance soil microbial activities and physical properties and improves soil nutrient status. However, organic wastes have also been shown to be a source of microbial contaminants including pathogens. Related risks are governed by pathogens' survival and transport particularities. We evaluated the significance of high levels of CaCO3, common in arid and semi-arid soils, on survival of Escherichia coli NAR at different temperatures. Amendments of 0, 5, 10, 15 or 25 g CaCO3 were mixed into variable soil amounts to obtain 100 g soil-CaCO3 mixtures. Both sterile and non-sterile soil mixtures were tested. Suspensions of a nalidixic acid-resistant E. coli strain (E. coli NAR) were added to the mixtures at a rate of 10(6) cell g(-1) soil. Mixtures were incubated at 4, 15, or 37 °C at the soil's field capacity for water (i.e. 0.13 g g(-1)). Each treatment was tested in triplicate. Persistence of culturable E. coli NAR was verified throughout the incubation period. The recovery rates of culturable E. coli NAR were significantly correlated to CaCO3 concentrations (P < 0.05). Incubation temperature (T) was the most significant factor (P < 0.01). In non-sterile mixtures the largest decline in survival rates of E. coli NAR was measured for treatments with larger CaCO3 content (i.e. 15 and 25%). Interaction of temperature and CaCO3 was significant for E. coli NAR die-off. Sterilization of soil caused non-uniform fluctuations in the effect of treatments. The maximum calculated decay rate for E. coli NAR was 0.83 d(-1) for the 15 g CaCO3 non-sterile mixture incubated at 37 °C while the minimum was 0.09 d(-1) for the control unamended sterile soil incubated at 15 °C. A combination of high temperature, large CaCO3 concentrations and a non-sterile, biologically active soil created the least favorable conditions for E. coli survival.
Asunto(s)
Carbonato de Calcio/metabolismo , Escherichia coli/fisiología , Microbiología del Suelo , Suelo/química , Recuento de Colonia Microbiana , Clima Desértico , Escherichia coli/crecimiento & desarrollo , Irán , Dinámica Poblacional , TemperaturaRESUMEN
This study was carried out to investigate the transport of Escherichia coli NAR and bromide (Br) through repacked (R) and weathered (W) soil columns. A suspension containing E. coli NAR and Br were leached and the effluent from the weathered soil columns had greater contaminant concentrations than that from the repacked soil columns. The time to the concentration peak of (C(max)) E. coli NAR and Br increased in the order CL-W < SL-W < SL-R < CL-R. The breakthrough sequence suggests the formation of a heterogeneous soil pore network induced by weathering and the importance of accelerated flow in the weathered columns. The dual-permeability model in HYDRUS-1D software was used to simulate the E. coli NAR and Br transport parameters by inverse modeling. Parameters of the attachment-detachment model were calculated using the dual-permeability model parameters fitted to the BTCs of E. coli NAR. A greater attachment coefficient associated with soil repacking and the finer textured clayey soil demonstrated the importance of adsorbent site and smaller pore spacing in these treatments. Smaller attachment and adsorption isotherm coefficients in weathered soil columns suggest the need for further research to validate this as a predictive model for the risks for vadose zone contaminant transport.
Asunto(s)
Bromuros/química , Escherichia coli , Contaminantes del Suelo/química , Suelo/química , Microbiología del SueloRESUMEN
Organic wastes are considered to be a source for the potentially pathogenic microorganisms found in surface and sub-surface water resources. Following their release from the organic waste matrix, bacteria often infiltrate into soil and may be transported to significant depths contaminating aquifers. We investigated the influence of soil texture and structure and most importantly the organic waste properties on the transport and filtration coefficients of Escherichia coli and total bacteria in undisturbed soil columns. Intact soil columns (diameter 16 cm and height 25 cm) were collected from two soils: sandy clay loam (SCL) and loamy sand (LS) in Hamadan, western Iran. The cores were amended with cow manure, poultry manure and sewage sludge at a rate of 10 Mg ha(-1) (dry basis). The amended soil cores were leached at a steady-state flux of 4.8 cm h(-1) (i.e. 0.12 of saturated hydraulic conductivity of the SCL) to a total volume of up to 4 times the pore volume of the columns. The influent (C(0)) and effluent (C) were sampled at similar time intervals during the experiments and bacterial concentrations were measured by the plate count method. Cumulative numbers of the leached bacteria, filtration coefficient (lambda(f)), and relative adsorption index (S(R)) were calculated. The preferential pathways and stable structure of the SCL facilitated the rapid transport and early appearance of the bacteria in the effluent. The LS filtered more bacteria when compared with the SCL. The effluent contamination of poultry manure-treated columns was greater than the cow manure- and sewage sludge-treated ones. The difference between cow manure and sewage sludge was negligible. The lambda(f) and S(R) values for E. coli and total bacteria were greater in the LS than in the SCL. This indicates a predominant role for the physical pore-obstruction filtration mechanisms as present in the poorly structured LS vs. the retention at adsorptive sites (chemical filtration) more likely in the better structured SCL. While the results confirmed the significant role of soil structure and preferential (macroporous) pathways, manure type was proven to have a major role in determining the maximum penetration risk of bacteria by governing filtration of bacteria. Thus while the numbers of bacteria in waste may be of significance for shallow aquifers, the type of waste may determine the risk for microbial contamination of deep aquifers.
Asunto(s)
Bacterias/metabolismo , Filtración/métodos , Compuestos Orgánicos/aislamiento & purificación , Microbiología del Suelo , Contaminantes del Suelo/aislamiento & purificación , Adsorción , Escherichia coli/metabolismo , Heces/microbiologíaRESUMEN
To determine the effects of kappa-opioid receptor agonists on phosphoinositide metabolism in rat renal cortex, tissue slices labelled with [3H]inositol were stimulated with norepinephrine or carbachol alone or in combination with the kappa-opioid receptor agonists, ethylketocyclazocine, trans-3,4-dichloro-N-methyl-N-[2-(pyrrolindinyl)-cyclohexyl)- benzeneacetamide (U50,488) and nalorphine. Both norepinephrine and carbachol stimulated phosphoinositide hydrolysis (measured in a LiCl buffer) concentration- and time-dependently. The EC50 and maximal stimulation of phosphoinositide hydrolysis for norepinephrine and carbachol were approximately 3 microM and 0.15 dpm released/dpm incorporated, respectively. Concentrations up to 1 mM of ethylketocyclazocine, U50,488 or nalorphine alone did not affect phosphoinositide hydrolysis. However, ethylketocyclazocine and U50,488 decreased 10 microM norepinephrine-stimulated phosphonositide hydrolysis concentration-dependently, each with an approximate IC50 of 30 microM. In contrast, nalorphine had no effect on norepinephrine-stimulated phosphoinositide hydrolysis. In addition, concentrations of up to 1 mM ethylketocyclazocine or U50,488 did not alter carbachol-stimulated phosphoinositide hydrolysis. The inhibitory effect of U50,488 and ethylketocyclazocine on norepinephrine-stimulated phosphoinositide hydrolysis was blocked by the selective kappa-opioid receptor antagonist, nor-binaltorphimine. These results indicate that kappa 1-opioid receptor stimulation may affect phosphoinositide metabolism in rat renal cortex by modulating the subcellular effects of renal alpha 1-adrenoceptor activation.
Asunto(s)
Corteza Renal/metabolismo , Fosfatidilinositoles/metabolismo , Receptores Opioides kappa/agonistas , Animales , Carbacol/farmacología , Etilcetociclazocina/farmacología , Hidrólisis , Técnicas In Vitro , Corteza Renal/efectos de los fármacos , Masculino , Naltrexona/análogos & derivados , Naltrexona/farmacología , Norepinefrina/farmacología , Ratas , Receptores Opioides delta/agonistas , Receptores Opioides mu/agonistas , Estimulación QuímicaRESUMEN
This study examines the effects of chronic brief restraint on in vivo benzodiazepine (BZD) receptor binding in mouse brain. Three groups of mice were used. Mice in group 1 were neither restrained nor injected (ACUTE control). Mice in group 2 were restrained for 5-6 s by grabbing the back skin and holding the subject upside-down at a 45 degrees angle as if to be injected (CHRONIC SHAM control) for 7 d. Mice in group 3 (CHRONIC SALINE) received daily single intraperitoneal (ip) injections of saline (5 mL/kg) for 7 d. On d 8 BZD receptors were labeled in vivo by administration of 3 microCi [3H]flumazenil (ip). The levels of ligand bound in vivo to cerebral cortex (CX), cerebellum (CB), brain stem (BS), striatum (ST), hippocampus (HP), and hypothalamus (HY) were determined. Results indicated that the level of binding was significantly (p < 0.01) lower by 30-50% (depending on the brain region) in saline-injected or sham control groups compared to acute control animals. Furthermore, the values for sham control were similar to the saline-treated group. Our data suggest that exposure to chronic mild restraint produces a decrease in in vivo binding of [3H]flumazenil in mouse brain and supports the hypothesis that chronic mild stress produces a decrease in BZD receptor binding sites.
Asunto(s)
Química Encefálica/fisiología , Receptores de GABA-A/metabolismo , Estrés Psicológico/metabolismo , Animales , Química Encefálica/efectos de los fármacos , Flumazenil/farmacología , Masculino , Ratones , Receptores de GABA-A/efectos de los fármacos , Restricción FísicaRESUMEN
Mice received i.p. injections of either saline or drug before i.p. administration of [3H]Ro 15-1788 (flumazenil), a selective benzodiazepine (BZD) receptor antagonist. Subjects were decapitated and six brain regions (cortex, cerebellum, striatum, hippocampus, hypothalamus and brain stem) were analyzed for the levels of tritium present in each tissue. Benzyl, ethyl and methyl alcohol enhanced in vivo binding of [3H]Ro 15-1788 in a dose-dependent manner in all brain regions studied with mean ED50 values of 2.4, 34.8 and 38.4% volume/kg body weight, respectively. Lorazepam (18 mg/kg) completely blocked effects of benzyl, ethyl and methyl alcohol to increase [3H]Ro 15-1788 binding. These data indicate that the alcohol-induced increases in [3H]Ro 15-1788 binding occurred at the level of the BZD receptor. In addition, these alcohols did not alter the in vivo binding of [3H]diprenorphine, an opioid receptor ligand, further indicating the selective effect of alcohol on BZD receptors. Administration of lorazepam or alprazolam produced a dose-dependent decrease in the binding of [3H]Ro 15-1788 to brain tissue after administration of either saline or 30% volume/kg ethanol. However, low doses of alprazolam increased binding of [3H]Ro 15-1788 in the absence of ethanol. Together, these results suggest that ethanol produces an increase in the number of BZD binding sites in vivo. These alcohol-induced alterations in BZD receptor binding may mediate, in part, the anxiolytic or sedative properties of ethanol.
Asunto(s)
Química Encefálica , Etanol/farmacología , Flumazenil/metabolismo , Proteínas de la Membrana/efectos de los fármacos , Receptores de GABA-A/efectos de los fármacos , Alprazolam/farmacología , Animales , Alcohol Bencilo , Alcoholes Bencílicos/farmacología , Canales de Cloruro , Diprenorfina/metabolismo , Masculino , Proteínas de la Membrana/metabolismo , Metanol/farmacología , Ratones , Receptores de GABA-A/metabolismo , TritioRESUMEN
The effects of the monoamine uptake inhibitors cocaine, nisoxetine, and desipramine (DMI) on norepinephrine (NE) stimulated phosphatidylinositol (PI) hydrolysis were investigated. Rat cortical tissue slices were labeled with [3H]inositol. Slices were then stimulated, in vitro, with NE in LiCl containing buffer in the presence and absence of monoamine uptake inhibitors. Cocaine and nisoxetine, but not DMI, potentiated NE-stimulated PI hydrolysis with a significant decrease in the EC50. Nisoxetine appeared to be more potent than cocaine with respect to the potentiation of NE-stimulated PI hydrolysis. The potentiating effect of cocaine was biphasic and dependent upon the concentrations of cocaine and NE. The NE concentration-effect curve was shifted to the right 100-fold in the presence of 0.1 microM prazosin. Cocaine at 10 microM did not potentiate NE-stimulated PI hydrolysis in the presence of 0.1 microM prazosin. Cocaine at 10 microM did not affect significantly the binding of [3H]prazosin or the NE-[3H]prazosin competition binding to cortical membranes. The results suggest that NE-uptake inhibition by cocaine and nisoxetine is the mechanism for the enhancement of NE-stimulated PI hydrolysis.