Refine search
Results 131-140 of 61,991
Dissipation of butachlor by a new strain of Pseudomonas sp. isolated from paddy soils
2020
Pourbabaei, A. A. | Khoshhal Nakhjiri, E. | Torabi, E. | Farahbakhsh, M.
Butachlor (BUT) is a chloroacetanilide herbicide widely applied to rice paddies to control annual grass and broad-leaf weeds. A BUT-degrading bacterial strain (PK) was isolated from paddy soils. Biochemical and 16S rRNA sequencing characteristics confirmed the strain as Pseudomonas aeruginosa (99% resemblance). The isolate dissipated BUT (100 μg/mL) in an M9 liquid medium with a rate of 0.5 ± 0.03 day-1 and DT50 and DT90 of 1.38 ± 0.10 days and 4.58 ± 0.32 days, respectively. Soil dissipation of BUT was investigated under flooded conditions. In sterile soils, the isolate increased the dissipation of BUT (200 μg/g) (DT50 = 12.38 ± 1.83 days, DT90 = 41.12 ± 6.09 days, k = 0.06 ± 0.01 day-1) compared to sterile non-inoculated samples (DT50 = 26.87 ± 2.82 days, DT90 = 89.25 ± 9.36 days, k = 0.03 ± 0.00 day-1). In non-inoculated non-sterile soil experiments, the dissipation of BUT was faster (DT50 = 15.17 ± 2.11 days, DT90 = 50.38 ± 7.02 days, k = 0.05 ± 0.00 day-1) compared to non-inoculated sterile ones, and inoculating the isolate accelerated the removal of BUT in non-sterile soils significantly (DT50 = 8.03 ± 1.20 days, DT90 = 26.68 ± 3.97 days, k = 0.09 ± 0.01 day-1). BUT inhibited soil respiration (SR) initially for 5 days, followed by an increase until day 20. The increase in SR was more pronounced in the co-presence of BUT and the isolate. The results of this research suggest P. aeruginosa PK as a suitable candidate for BUT bioremediation.
Show more [+] Less [-]A Regression-Based Analysis to Assess the Impact of Fluoride Reach River Water on the Groundwater Aquifer Adjacent to the River: A Case Study in Bharalu River Basin of Guwahati, India
2020
Das, M. | Bhattacharjya, R. K.
Fluoride is one of the parameters which is non-degradable and naturally occurring inorganic anion found in many natural streams, lakes, and groundwater. Serious problems are faced in several parts of India due to the high consumption of fluoride through drinking water. These may cause dental and skeletal fluorosis to humans. This study aims to examine the level of fluoride in both Bharalu river water and groundwater within Guwahati city, Assam, India, and also to analyze the impact of fluoride reach river water on the groundwater aquifer adjacent to the river. From the investigation, it has been observed that the concentration of fluoride varies from 0.02 to 3.73 mg/l in river water and 0.04 to 4.7 mg/l in the case of groundwater. The statistical analysis shows that there is a strong correlation between the fluoride concentration of river water and groundwater. This indicates that the groundwater might have contaminated by the polluted river water.
Show more [+] Less [-]Road Traffic and PM10, PM2.5 Emission at an Urban Area in Algeria: Identification and Statistical Analysis
2020
Belarbi, N. | Belamri, M. | Dahmani, B. | Benamar, M. A.
Air quality in greater Algiers, in Algeria was assessed analyzing aerosol particulate matter (PM10 and PM2.5) at a site influenced by heavy road traffic. Particulate matters were collected using a Gent sampler to characterize the atmospheric aerosol of Algiers. An Energy dispersive X ray spectrometer (EDXRF) was used to determine the heavy metal concentrations in the PM2.5 and PM10 size fractions. Principal Component analysis and Enrichment factor were used to identify the major sources of air pollutants for PM10 fraction in the studied area. Backward trajectories were calculated in order to identify potential distant sources that contribute to particulate pollution in our site. Significant concentrations of PM 2.5 and PM10 as well as associated heavy metals have been documented. The mean concentrations of heavy metals contained in PM10 and PM2.5 were, in descending order, Fe>Zn>Ni>Pb>Mn>Co>Cr; Pb>Mn>Co>Fe>Zn>Ni>Cr respectively. The contribution of road traffic to the levels of fine (PM2.5), and coarse (PM10) particles were studied.
Show more [+] Less [-]Effect of Composting Process on Some Chemical-Biological Properties and Heavy Metals Behavior of Municipal Sewage Sludge as Affected by Various Bulking Agents
2020
Saffari, M. | Saffari, V. R. | Khabazzadeh, H. | Naghavi, H.
The present study tries to investigate the effect of composting process on some properties and heavy metals status of two municipal sewage sludge (MSS) as affected by three different organic bulking agents (BAs) at three levels (10%, 25%, and 45% V/V). According to the results, the composting process could reduce the fecal coliform to class A, a reduction more obvious in treatments with BAs than produced composts without them. Changes in the chemical properties of the composts vary according to the type of MSS and Bas. Based on the compost quality standard, most of the produced samples are classified in compost-class II. Examination of the total form of three heavy metals (HMs: Zn, Ni, Fe) of both MSS shows that composting process without BAs increases the HMs total concentration, but using of BAs have not been clear trends. In the contrary, BAs application reduced the available form of Fe and Ni, but increased the Zn available form. Examination of chemical forms of each studied HMs also shows that the composting process reduces the Ni and Fe mobility factor, but increases that of Zn. Generally, while, prepared composts can classify into the compost-class II, based on their properties, the high concentration of total Zn above the standard limit makes it extremely restrictive to be used as class II compost. However, according to EPA regulations, the composts with this concentration of Zn can be used as a relatively safe organic material on agricultural land.
Show more [+] Less [-]Performance and emission characteristics of the diesel engine running on neem (Azadirachta indica) biodiesel with effect of exhaust gas recirculation at optimum injection strategies
2020
Singh, Y. | Singla, A. | Sharma, A. | Singh, N. K.
Environmental pollution and strict emission norms are promoting researchers to explore the methods for reducing pollution and provide optimum solution. By considering these situation as the baseline, study was conducted to analyse the effect of exhaust gas recirculation (EGR) on performance and emission of the DI diesel engine. The effects of Injection Timings (IT), split injection and Exhaust Gas Recirculation on performance, emission characteristics of diesel engine fuelled neem biodiesel blends are investigated. Initially experiments are conducted with diesel, NB5, NB10 with original injection timing of 23° bTDC with direct injection and are considered as base reading. The fuel injection is optimized (at 19° bTDC and 16% split injection) and the effect of EGR rate at this optimized condition is analysed. Significant reduction of about 65.3%, 67% and 57% in the amount of NOx was obtained at full load as compared to base readings. Smoke emissions reduced by 2.8-3.4% and CO emissions reduced by around 52% for diesel and biodiesel blends at full load.
Show more [+] Less [-]Algal Indices as a Biomonitoring Tool to Assess Eutrophication in the Urban Ponds: a Case Study
2020
Vishal, R. | Meeta, B.
Eutrophication of the urban water bodies is one the biggest challenge causing severe ecological and economic loss. Urban ponds are more prone to eutrophication due to their small size and polluted catchment areas. Biomonitoring using phytoplankton provides cost-effective estimation of the level of eutrophication. Ten urban ponds in different areas of the Mumbai city were chosen to investigate the phytoplankton community structure, and level of eutrophication. We assessed the 3 algal indices viz. Shannon-Wiener indices, Palmer and Nygard's (Myxophycean and diatom) indices. Linear relationship of these indices was tested against Carlson trophic state indices in order to assess the effectiveness of these indices to measure the degree of eutrophication in urban lakes. All ten lakes were found to be eutrophic, of which two were very low eutrophic (TSI – 53.74-53.95), four were low-mid eutrophic (TSI – 55.18 – 57.5), and four lakes were mid eutrophic (TSI 61.4 – 62.2). Shannon-Wiener indices (r= -0.73) and Myxophycean indices (r= 0.77) showed strong correlation with TSI whereas Diatom indices (r= -0.12) and Palmer’s Algal Pollution Indices (r= - 0.47) showed weak correlation with TSI. Thus study found that Shannon-Wiener indices and Myxophycean indices are reliable and cost effective means to assess the eutrophication of urban ponds in Mumbai.
Show more [+] Less [-]Phytoremediation of soil Contaminated by Heavy Metals within a Technical Landfill Center Vicinity: Algerian Case Study
2020
Boukaka, Kh. | Mayache, B.
The contamination of environment with heavy metals has become a serious problem which can affect the human health. Three heavy metals (Zn, Cd and Pb) were determined in soil and plants for below and aboveground parts along landfill Demina center, located in the wilaya of Jijel, Algeria to evaluate their behavior and uptake by Ditrichia viscosa, Juncus effusus and Solanum nigrum. In our research we tried to study the capacity of these spontaneous plants to accumulate and to translocate heavy metals from soil to their tissues during three years. The heavy metals examined in the soils of the study area showed variations in concentrations, the study area may be practically unpolluted with Zn and Pb (CF; 0.45 and 0.98 successively) and very contaminated with Cd (CF; 8.53). According to the results obtained, the soil is uncontaminated with lead (Igeo=-0.60) and zinc (Igeo= -1.42) but it is heavily contaminated with cadmium (Igeo=2.5) along the study area. Overall the BCFS (bioconcentration factors) are superior to 1, for the all heavy metals and species. However, BCFs follow the following order; BCFZn>BCFPb>BCFCd for Ditrichia viscosa, the following order BCFPb>BCFZn>BCFCd for Juncus effuses and follow the following order; BCFZn>BCFCd>BCFPb for Solanum nigrum. The TFs (translocation factor) of the present study showed that Solanum nigrum can translocate the three of the metals into their aboveground parts.
Show more [+] Less [-]Synthesis and characterization of activated carbon from biowaste-walnut shell and application to removal of uranium from waste
2020
Yaman, M. | Demirel, M. H.
The aim of this study is to synthesize and characterize an economical and environmentally-friendly adsorbent with high adsorption capacity. For this purpose, the walnut shells (Juglans regia L.) were chemically modified using sulfuric and citric acids, separately. After pyrolysis and synthesis of activated carbon (AC), the optimization of conditions at the preconcentration/removal step was performed using parameters such as pH and contact time for uranium in the model solutions. The measurements were carried out by inductively coupled plasma-mass spectrometry (ICP-MS). From the shapes of the BET isotherms, it may be stated that activated carbon exhibit type I. It was found that the surface area and total pore volume of the activated carbon were 696.6 m2/g and 0.35 mL/g, respectively. The adsorption capacity was found to be 220 mg/g. It was found that the optimum pH is 6.0 for preconcentration/removal using AC obtained by sulfuric acid as chemically-modifier. The optimized method was applied to determination of U at ng/mL levels in the model solutions.
Show more [+] Less [-]Microbeads in Sediment, Dreissenid Mussels, and Anurans in the Littoral Zone of the Upper St. Lawrence River, New York.
2019
Schessl, M. | Johns, C. | Ashpole, S. L.
Global plastic production has exceeded 300 million tons per year (Plastics Europe, 2015). In the marine and freshwater environments, larger plastics abrade and photo-degrade resulting in persistent environmental microplastics that are not effectively removed by existing wastewater treatment plants (WWTPs). The ecological effects of microplastics on the marine environment are poorly understood, with even less attention to freshwater systems. To assess whether microplastics have infiltrated food webs of shallow nearshore ecosystems of the St. Lawrence River, we sampled four sites along the international section of the St. Lawrence River, from Alexandria Bay to Waddington, NY. Twelve sediment samples along with one hundred and forty-nine Dreissenid mussels (Dreissena polymorpha and D. bugensis) were collected from the littoral zone, and forty one road-killed anuran amphibian specimens were collected adjacent to the river. Sediment subsamples at two of four sediment sampling sites contained plastic micro-particles. No microbeads were detected within any of the Dreissenid mussels or anuran digestive tract samples. The Dreissenids were likely too small to ingest microbeads greater than 35 microns. Microplastics congregating in the littoral zone may pose a threat within the food web through potential ingestion, requiring further methodological development.
Show more [+] Less [-]Three-dimensional analytical models for time-dependent coefficients through uniform and varying plane input source in semi-infinite adsorbing porous media.
2019
Yadav, R. R. | Yadav, V.
In the present study, analytical solutions are developed for three-dimensional advection-dispersion equation (ADE) in semi-infinite adsorbing saturated homogeneous porous medium with time dependent dispersion coefficient. It means porosity of the medium is filled with single fluid(water). Dispersion coefficient is considered proportional to seepage velocity while adsorption coefficient inversely proportional to dispersion coefficient. Solutions are derived for both uniform and varying plane input source. The source geometry, including shape and orientation, broadly act major role for the concentration profile through the entire transport procedure. Initially the porous domain is not solute free. It means domain is throughout uniformly polluted. With help of certain transformation advection-dispersion equation is reduced into constant coefficient. The governing advection-dispersion equation, initial and boundary condition is solved by applying Laplace Transform Technique (LTT). The desired closed-form solution for the line source in two-dimensions and point source in one-dimension of uniform and varying nature are also evaluated as particular cases. Effects of parameters and value on the solute transport are demonstrated graphically.
Show more [+] Less [-]