Journal of Global Ecology and Environment
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ENVIRONMENTAL APPLICATION OF NATURAL BENTONITE AS ADSORPENT OF MERCURY ION FROM AQUEOUS SOLUTION
No full textThe adsorption of mercury (Hg (II)) ions onto Natural bentonite was investigated. The effects of pH, initial adsorbent dosage, contact time and temperature were studied in batch experiments. The highest removal ratio (90%) obtained at reaction time of 50 min and pH 5 with the appropriate dosage of adsorbent was 1.5 g/100 mL. In addition to that, pseudo- first and second order kinetic model and Weber–Morris model were applied to describe the adsorption kinetics. The values of correlation coefficient (R2) were 0.83, 0.96 and 0.95, respectively. Which means that the adsorption of Hg (II) ion from aqueous solution onto Natural bentonite was followed the pseudo 2nd order kinetic, and the adsorption process was spontaneous. Langmuir and Freundlich models described the sorption isotherms. The results indicated The Langmuir model gave a better fit (R2= 0.99) than the Freundlich model (R2= 0.95) which mean that the Freundlich and Langmuir model were able to describe properly the isotherm of a mercury ion on bentonite. The thermodynamic parameters indicated spontaneous and endothermic nature of the adsorption process. The results demonstrate that the natural bentonite is effective in the removal of heavy metals from aqueous solutions and can be used as alternative of high cost commercial adsorbents
DISTRIBUTION AND ABUNDANCE OF HORNBILLS IN FOREST LANDSCAPES IN SOUTHERN GHANA
No full textWe investigated the distribution and abundance of hornbills in different forest landscapes in southern Ghana. 639 individuals of five species of hornbill were recorded. The highest abundance of hornbills were recorded in a mining concession and the least in a sacred grove. The African pied hornbills (Tockus fasciatus) were found in all forest landscapes irrespective of the type of anthropogenic matrices associated with them, indicating their resilience to anthropogenic habitat changes. The larger species, Black-casqued hornbill (Ceratogymna atrata), was found in a national park only. The results of this study call for a review in the protection protocols in the national parks of Ghana to save the Black-casqued hornbill, and a review of Ghana’s mining policies to secure habitats for the hornbills
SPATIOTEMPORAL EVOLUTION OF PLANT DIVERSITY AND EDAPHIC CHARACTERISTICS IN THE STEPPES OF ALFA (Stipa tenacissima) OF THE REGION OF SAIDA (WESTERN ALGERIA)
No full textOur work is to follow the spatial and temporal variations of the floristic and soil parameters during three years of monitoring (2013- 2014 -2015), held in three sampling stations in the steppes of Alfa (Stipa tenacissima) in the municipality of Maâmora (region of Saida, western Algeria). For this, 21 phytosociological statements were conducted annually on the three sampling stations. Station 1 an exclosure where alfa is well developed, Station2 where alfa is moderately degraded and station 3 where alfa is degraded. The floristic survey has shown variability in the number of species annually following the annual rainfall variability. Indeed, a maximum rate of 29 species were found on the three stations in 2013 is the year when rainfall was significant (517 mm) and that, contrary to 2014 when drought was pronounced (295, 9 mm), resulting in a fall in the number of species to 22 species. Overall, the biological spectrum of these species is marked by the predominance of therophyts which are mainly dominated by Poaceae, Asteraceae and the Caryophylaceae during the observation period. The soil analysis shows that the soil of the three stations is silty-sandy texture, shallow poor in organic matter, low humidity, salt-free, alkaline pH with a rate appreciably total limestone. Changes in these edaphic parameters are very visible to the spatial and temporal scale considered in this work. The process of data obtained by the factorial analysis of correspondences (AFC) emphasize in the existence of two groups of stations. Group 1 is correlated to Station 1 (recovery rate of Stipa tenacissima (TR) = - 0,493), hemicryptophyts (He) = -0,424, geophyts (Geo) = -0,114, a soil surface horizon with improved thickness (PR) = -0,316, better moisture (HUM) = -0,102, organic metter (MO) = -0,278). Group 2 is correlated to stations 2 and 3 (therophyts (TH) = -0,103, chamaephyts (CHA) = 0,516, sand (SB) = 0,106. clays (AR) = 0,092, total limestone (CaT) = 0,197) reflecting the degree of middle of opening that is related to a gradient of aridity evolving on a substrate represented mainly by sand and silt, reflecting the degree of middle of opening that is related to a gradient of aridity
ANALYSIS OF LARGE COMMERCIAL GREENHOUSES IN WARM CLIMATES USING CFD AND BAYESIAN NETWORKS
No full textIn warm countries, the major problem to greenhouses is the design since its dimensions could cause negative effects to crops. Smaller greenhouses have less stable conditions, but they are easier to control than large commercial greenhouses. However, it is more profitable to have large greenhouses, for reasons of management. The main problem that a large commercial greenhouse has is that ventilation is inadequate, leading to the use of forced ventilation, increasing production costs. Airflow speed near the floor is insignificant to reduce the negative effects of solar radiation. We analyzed the environmental conditions within a large commercial greenhouse in order to obtain improvements in its design using Computational Fluid Dynamics approximation. The results of the numerical approximation were analyzed with Bayesian classifications to improve the relationships among variables for defining the environment conditions. Large greenhouse geometry defines environmental conditions: height of cover determines the radiation incident inside. Thus, higher greenhouses are more convenient as they are less warm. The results of this study are useful for future designs in countries with warm climate
PRODUCTION AND CHARACTERIZATION OF ACTIVATED CARBON ORIGINATED FROM Lantana camara Stem
No full textThe application of agricultural waste for the production of activated carbon for the adsorption of pollutants from wastewater has become attractive in recent time. Activated carbon was produced from Lantana camara stem in this study. The Lantana camara stem were cut into smaller sizes, washed and sundried for 6 days. Thereafter, it was carbonized at 300°C for 2 hr and then grinded to granules before being steam activated. The activated LCS was oven-dried at 105°C for 24 hr and grinded to 2 mm mesh sizes. The Fourier Transform Infrared (FTIR) analysis indicate that steam-activated LCS is characterized by stretching vibration (3500 – 2500 cm-1), and stretching vibration (2196 cm-1) as well as stretching vibration (1682 cm-1). Similarly, the Scanning Electron Microscopy (SEM) analysis shows that the average pore size on the activated LCS is 20 µm. This Indicates that the steam-activated carbon produced from LCS may be a potential adsorbent for the adsorption of pollutants found in wastewater
STUDY OF THE ACCUMULATION OF ZINC BY THE RAY GRASS PLANTED IN CONTAMINATED SOIL
No full textMost sites contamined with heavy metals, the phytoextraction is based on the use of plants for the remediation of contamined sites. This technique is not very aggressive to the environment and relatively inexpensive.
In this study, we have interested in the phytoextraction in the Ray grass of a soil contaminated artificially by zinc and the influence of this metal presence on the ray grass growth. The results showed that the ray grass of Italy Lolium multiflorum Lam is tolerant in the zinc; it presents no sign of stress after 4 weeks of culture in soil contaminated by these metals. The accumulated zinc arrests at the level of roots and it is not transferred towards the air parts
GEOTHERMS AND FOREST FORMATION IN INSULAR VOLCANIC LANDSCAPE
No full textConducting channels of magma-based geothermal system causing abnormal increases in soil temperature have been found in the region of the degassing Mendeleev volcano (Kunashir Island, South Kuril ridge). This process was favorable for transgression of more southern species and entire communities to this boreal-forest ecoregion over a long period of time. The "climatically unjustified" but sufficiently stable subboreal forest ecosystems were formed, as well as the early stages of buffer forest communities. Geothermal energy induces rearrangement of the plant cover towards the increase in its floro- and phytocoenotic diversity to the detriment of biomass formation rate. The largest possible (under the given climatic conditions) diversity of floristic and phytocoenological structures creating terrestrial vegetation at the transitional zone from continent to ocean originates just from island volcanic landscapes
SCREENING OF HEAVY METALS AND AROMATIC HYDROCARBON-RESISTANT BACTERIA ISOLATED FROM MARCHICA LAGOON ECOSYSTEM IN MOROCCO
No full textThe lagoon of Marchica, which is classified as a sensitive biological area has been, in the past, a major destination for metal and hydrocarbons pollutants. Consequently, all fish resources have become unusable. The pollution of this marine environment has been the subject of major concern, although the site is no longer subjected to active pollution discharges. The aim of the present study was to evaluate metal contamination over fifteen different sampling sites and to isolate heavy metals, antibiotics and hydrocarbon-tolerant bacteria. The isolated strains showed multiple metal resistances to copper, lead, cadmium and mercury at concentrations of, 8, 6.8, 4 and 2 mmol/l, respectively for Exiguobacterium marinum. Furthermore, the bacterial community was able to grow in the presence of significant concentrations of sodium chloride (80 g/l), polycyclic aromatics hydrocarbons (PAHs: at 7.3 g/l), and antibiotics (especially penicillin and tetracyclin, as shown in Table 6). The growth kinetics in the presence of mercury (1 and 2 mmol/l), showed that the isolates had a noticeable ability to multiply in the presence of inhibitors. Taking into consideration the halophilic properties and the substantial resistance in the presence of heavy metals and hydrocarbons, the isolated strains have demonstrated potentially significant contributions as wastewater treatment bacteria, and in the potential implementation of a decontamination protocol through the use of bioremediation strategies to reduce lagoon pollution
NATURAL REGENERATION OF Juniperus excelsa IN RELATION TO STAND CHARACTERISTICS IN NORTHWEST OF IRAN
No full textThe Juniper excelsa stands are distributed in large areas of Iran and have ecological importance. Restricted natural regeneration of J. excelsa is one of the problems in these stands. In this research natural regeneration of J. excelsa in relation to stand characteristics (tree density, canopy cover and tree species diversity) were investigated in the northwest of Iran. A total of 28 woody species belonging to 14 families were recorded from the study area. The total density of trees was 74.8 stem ha-1. The density of J. excelsa was 32.7 stem ha-1, which comprise 43.7% of the total tree density. The J. excelsa had the highest value of basal area (0.37 m2ha-1, 33%) and species importance value (85.1). The total regeneration density was 60.5 stem ha-1, and the J. excelsa had 11.3 stem ha-1 (18.7%). Species diversity of stand trees (Shannon – Wiener index) were divided into three classes: low (H\u27 < 0.5), medium (0.5 < H\u27 < 1) and high (H\u27 > 1). The means of juniper regeneration densities in the low, medium and high tree species diversity classes were obtained 3.7, 8.1 and 20.4 stem ha-1, respectively. The results indicated that regeneration density of J. excelsa was increased by increasing stand trees density, stand canopy cover and stand trees species diversity (P = 0.01). The forest management objectives should be to increase density and species diversity of trees in these stands
PERFORMANCES OF REVERSE OSMOSIS AND NANOFILTRATION IN DESALINATION OF RIVER BRACKISH WATER
No full textAs many countries in the world, Morocco is facing problems in the supply of water due to an increasing demand and decrease of conventional resources. To face the problems, Morocco proceeded since a long time to use other non conventional water resources such as wastewater reuse or desalinating water. The desalination option which was limited to south and coasts extends more and more towards the central regions.
Mrirt is among the north cities where a construction of desalination plant is expected soon. The city is far from the coast and the water to be treated is slightly brackish. The city already has a standard treatment plant of drinking water. The National Office of Electricity and Drinking Water and Ibn Tofail University decided to conduct this study to compare the performances of Reverse Osmosis and Nano filtration technologies.
The experiments are conducted using pilot plants and various commercial membranes such as BW30LE4040, NF90 and NF270. Several parameters were examined in order to optimize the system performance, including operating pressure, flux, system recovery, salt rejection and specific energy consumption (SEC).
The obtained results showed that the experiment results appear to be compatible with those obtained by the software prediction.
The experiment results at 10 bars of feed pressure, for BW30 the values of recovery rate is 28% and 0.95 kwh/m3of energy consumption. For NF90, the recovery rate is 30% and 0.75 kwh/m3 of energy. But in the predict results, and under the same of the operating conditions pilot plant, the values of energy consumption are 0.91 of BW30 and 0.70 of NF90.
Thus, the prediction software results shows that the maximum recovery rate can be achieved to 85% at 20 l/h/m2 of average flux, andthe operating pressure needed to run the RO membrane is significantly higher (14, 6 bar as compared to 9, 90 bar) than the NF membrane