Simplified optimisation procedure for fixed bed adsorption systems

The adsorption of phenol, p-chlorophenol and mercuric ions onto activated carbon in fixed beds has been studied. The effects of process variables such as bed height and residence have been studied. The results have been used to predict optimum conditions for the systems based on the C exhaustion rate and the empty bed residence time (EBRT).     

The effect of subsoiling on soil resistance and cotton yield

Soil compaction occurs due to heavy wheeling or repetitive tillage in the field. Soil compaction changes the soil physical parameters and water infiltration that cause reduction in the crop yield. Proper subsoiling alleviates the negative effect of soil compaction. The objectives of the research was to examine the effects of subsoiling on the resistance of the soil and to find out deep tillage effects on the cotton yield and the convenient time for applying subsoil treatment for reducing the soil compaction. One-pass (B) and two-passes (C) subsoil treatments were applied in the fields where wheat, silage maize (Zea mays L.) and cotton (Gossypium hirsutum L.) crops were grown by 2 years rotation. The experiment was started in 1998 and carried out for 4 years. Soil penetrations were measured during the experiments years at thaw conditions of silty-clay soil (43% clay, 50% silt, 7% sand) before seedbed preparation in autumn seasons. According to the results, the subsoiling treatments created statistically significant effects on the soil resistance (P<0.05) comparing the control plots (A). The initial disruption in subsoiled plots has almost disappeared after 2 and 4 years in B and C plots, respectively. The soil resistance in C plots was lower than in B plot. The percentage of decrease in the soil resistance from A to B and A to C plots was calculated as 13.3 and 26.2%, respectively, in the first year. In the effective subsoiling area from 0.20 to 0.50 m depth, the ratio of penetration decrease in both plots was about 7–8% per year. The difference of penetration decrease between B and C plots was found to be about 15.8% level. Cotton yields at each subsoiled plots increased slightly comparing with control plots (A) where subsoiling was not applied. However, these increments were found to be statistically insignificant. It may be concluded that the subsoiling treatments does not affect the crop yield in intensive and fully irrigated field conditions.     

Mineralogy of soil kaolinites from Cameroon

Different particle-size fractions of soil clays from the semi arid north and the humid tropical south of Cameroon have been characterized with reference to their chemical composition, clay mineralogy and kaolinite crystallinity (Hinckley indices). Selected samples were also examined by Mössbauer spectroscopy. Hinckley indices of kaolinites, which were a major component of the coarse clays, varied considerably (< 0.1 - 0.69) and differed significantly as a function of the geographic and landscape positions of the soil profiles. The Hinckley indices averaged 0.31 in soils from southern Cameroon and 0.30 and 0.07 in soils from high and low landscape positions in northern Cameroon, respectively. Kaolinite crystallinity is therefore considered to vary as a function of transport and/or depositional environment of the kaolinite-containing material. Mössbauer spectra showed that kaolinite-dominated Vertisol coarse clays contained higher relative amounts of Fe²⁺ than the corresponding fine clay, which is dominated by smectite. It is conceivable that the Fe²⁺ content of the kaolinite reflects the redox environment of the samples.     

Physiochemical Processes Affecting the Geochemistry of Carbonate Aquifer of Southeastern Al-Ain Area, United Arab Emirates (UAE)

Detailed hydrogeochemical analyses were carried out in order to delineate the physiochemical processes and paleohydrogeological regime of groundwater flow of southeastern Al-Ain area and its surrounding desert fringes. Groundwater composition and salinization could be a result of integrated cycles of successive physiochemical processes of mixing of seawater, salt dissolution, and flushing by recharge water from the infiltration of rainfall in the interdune areas and gravel plains and also from Jabal Hafit lying to the southeast, and sewage effluent water from the residence areas to the northwest. In addition to that, ion exchange upon flushing, salt sieving from deep aquifers, and evaporation and accumulation along the wetland zones are factors affecting the groundwater of the area. Human and anthropogenic activities might have negative impact on the quality of groundwater in the region. Both Zn and Fe are the most detectable heavy metals in the analyzed samples, and they reach as maximum as 2,277 ??g/l and 2,902.6 ??g/l for Zn and Fe, respectively, along the north western localities. The source of these metals is most probably due to contamination threats by the sewage effluent or industrial wastes in these localities. Reducing environment releases the toxic and heavy metals in soluble compounds in case of high organic matters. A strong relationship appears between Fe and Zn ion concentrations in groundwater and the type of well construction materials (casings and screens). Also, a positive correlation is observed between the concentrations of Zn in water wells and in plants surrounding the wells. The increase of chromium concentrations is observed in the north of the study area, and this increase might be ascribed to the weathering of olivine and pyroxence of Oman Mountain in the northeast and might be possibly due to using the manure or animal wastes for agriculture activities.     

Toxicity of spiromesifen to the developmental stages of Bemisia tabaci biotype B

BACKGROUND: Spiromesifen is a novel insecticidal/acaricidal compound derived from spirocyclic tetronic acids that acts effectively against whiteflies and mites via inhibition of acetyl‐CoA‐carboxylase, a lipid metabolism enzyme. The effects of spiromesifen on the developmental stages of the whitefly Bemisia tabaci (Gennadius) were studied under laboratory conditions to generate baseline action thresholds for field evaluations of the compound. RESULTS: Adult B. tabaci mortality rate after spiromesifen treatment (5 mg L^?1) was 40%. Treatment with 0.5 mg L^?1 reduced fecundity per female by more than 80%, and fertility was almost nil. LC₅₀ for eggs was 2.6 mg L^?1, and for first instar 0.5 mg L^?1. Scanning electron microscopy revealed that eggs laid by treated adult females had an abnormally perforated chorion, and females were unable to complete oviposition. Light and fluorescent microscopy showed significantly smaller eggs following treatment, and smaller, abnormally formed and improperly localized bacteriomes in eggs and nymphs. The number of ovarioles counted in females treated with 5 mg L^?1 was significantly reduced. Spiromesifen showed no cross‐resistance with other commonly used insecticides from different chemical groups, and resistance monitoring in Israel showed no development of field resistance to this insecticide after 1 year of use. CONCLUSION: The strong effect on juvenile stages of B. tabaci with a unique mode of action and the absence of cross‐resistance with major commonly used insecticides from different chemical groups suggest the use of spiromesifen in pest and resistance management programmes. Copyright © 2008 Society of Chemical Industry     

Effect of Biochar on Immobilization of Cadmium and Soil Chemical Properties

A pot experiment was conducted at Institute of Biotechnology and Genetic Engineering (IBGE), University of Agriculture Peshawar, Pakistan. To conduct the experiment, eight kilograms of air-dried soil were taken in each pot and the amendment biochar was added and mixed properly at different levels like 0%, 1%, 2% and 4% (w/w), respectively. All pots were spiked with Cd solution at the concentration of 10?mg kg^?1. The treatments were arranged in completely randomized design (CRD). Fourteen days old nursery plants of rice Oryza sativa L. were transplanted into pots. Five rice plants were grown in each pot. After transplantation of rice plant, the nitrogenous and phosphatic fertilizers (Urea and DAP) were incorporated at the standard rate. Standing water condition was kept for rice grown in pots. Rice plants were harvested after 70 days germination. Soil samples were collected from each pot after plant harvesting. After soil analysis, the given data elaborated that the concentration of Cd in soil was stabilized by the amendment from 8.7?mg kg^?1 (0%) to 4.2?mg kg^?1 (4%). Among the other soil parameters the minimum soil pH (7.31), EC (0.151?dSm^?1), soil organic matter (0.63%), N (0.13%), P (4.72?mg kg^?1) and K (55.6?mg kg^?1) were noted at 0% biochar application, while maximum pH (8.23), EC (0.231?dSm^?1), soil organic matter (1.67%), N (0.25%), P (8.96?mg kg^?1) and K (93?mg kg^?1) were found in the pot treated with 4% biochar. Hence, it was concluded that Cd was significantly immobilized with 4% biochar application.

     

Mössbauer spectra of nontronites: Structural implications and characterization of associated iron oxides

Mössbauer spectra of three nontronite samples (Garfield H33a and SWa-1 from Washington State, U.S.A., and a sample from Hundsangen, Germany), taken between room temperature and 4.2 K in the velocity range ± 10.5 mm/s, showed between 2.9 and 13% of the total iron to be bound in goethite and not in the nontronite structure. This extraneous iron limits the utility of room temperature spectra for the assignment of structural iron sites in these samples. An adequately good distinction of the contributions of goethite and nontronite was possible in Mössbauer spectra taken at 77 K. The spectral components arising from iron in the nontronite octahedral sheets could be fitted with distributions of quadrupole-split doublets. These distributions indicate the existence of quasi-continuous octahedral site variations rather than two discrete (cis and trans) sites, and thus favour a structural model in which all octahedral iron is in cis coordination.