Sorption of atrazine on conventional and surface modified activated carbons.

The sorption of atrazine from water has been studied using a conventional activated carbon, F400, an annealed carbon sample, F400AN, and an aminated carbon sample, F400NH(2). Characterisation of the carbon samples showed that sample F400NH(2) had the highest proportion of micropores, but had the lowest values of point of zero charge (PZC) and iso-electric point (IEP). This was attributed to the existence of a high proportion of oxygen containing functional groups. Sorption data showed that sample F400AN was superior in the sorption of atrazine to samples F400 and F400NH(2). It was noted that pore size distribution alone was not the only contributing factor for the uptake of atrazine onto the activated carbons. The sorption data were fitted well using the Freundlich isotherm. The free energy change showed that sorption of atrazine on activated carbons is a spontaneous process. A pseudo-second order kinetic model was used for analysing the kinetic data, and it was concluded that adsorption of atrazine was controlled by a film diffusion mechanism.

Effect of surface modification of an engineered activated carbon on the sorption of 2,4-dichlorophenoxy acetic acid and benazolin from water.

The performance of a conventional (F400) and a surface modified activated carbon (F400AN) has been investigated for the sorption of benazolin and 2,4-dichlorophenoxy acetic acid (2,4-D) from water. It was observed that the modified carbon, F400AN, which was obtained by annealing the conventional sample had a higher BET surface area (960 m2 g(-1) compared to 790 m2 g(-1)) and it had a higher proportion of micropores. This was attributed to the loss of oxygen containing functional groups during the thermal treatment. Zeta potential and pH titration measurements also showed that acidic functionality had been lost on the F400AN sample. The adsorption data were analysed and were fitted well using the Langmuir isotherm. The modified carbon marginally out-performed the conventional activated carbon for sorption of these two herbicides. Thermodynamic parameters (DeltaG0, DeltaH0, and DeltaS0) were determined and their values indicated that the sorption process was spontaneous and endothermic for both herbicides. A pseudo-second-order kinetic model was employed for analysing the kinetic data. It was concluded that the herbicide sorption process was controlled by a film diffusion mechanism.

Investigation of the efficiency of existing air pollution monitoring sites in the state of Kuwait.

The use of mathematical modelling for investigation of the efficiency of existing monitoring sites for the impact of SO(2) emissions from power stations in the state of Kuwait is described. The Industrial Source Complex Short Term (ISCST3) model is utilised to obtain the spatial and temporal variations of SO(2) over residential areas. Statistical comparison between the 50 highest daily measured and predicted SO(2) concentrations at six monitoring sites shows that the model is capable of generating results with accuracy of 60--94%. An important conclusion of this work is that the existing locations of the Kuwait-EPA monitoring stations are not suitable for measuring the actual impact of SO(2). Therefore, there is a need for relocation of these sites to register the highest levels of SO(2) emitted from the current power stations in the state of Kuwait.

Inoculum Densities of Fusarium oxysporum f. sp. vasinfectum and Meloidogyne incognita in Relation to the Development of Fusarium Wilt and the Phenology of Cotton Plants (Gossypium hirsutum).

ABSTRACT Development of Fusarium wilt in upland cotton (Gossypium hirsutum) usually requires infections of plants by both Meloidogyne incognita and Fusarium oxysporum f. sp. vasinfectum. In this study, the soil densities of M. incognita and F. oxysporum f. sp. vasinfectum and the incidence of Fusarium wilt in three field sites were determined in 1982-1984. Multiple regression analysis of percent incidence of Fusarium wilt symptoms on population densities of M. incognita and F. oxysporum f. sp. vasinfectum yielded a significant fit (R (2) = 0.64) only on F. oxysporum f. sp. vasinfectum. Significant t-values for slope were also obtained for the interaction of M. incognita and F. oxysporum f. sp. vasinfectum, but densities of M. incognita and F. oxysporum f. sp. vasinfectum were also related on a log(10) scale. The physiological time of appearance of first foliar symptoms of Fusarium wilt, based on a degree-days threshold of 11.9 degrees C (53.5 degrees F), was used as a basis for determining disease progress curves and the phenology of cotton plant growth and development. Effects of Fusarium wilt on plant height and boll set were determined in three successive years. Increases in both of these plant characteristics decreased or stopped before foliar symptoms were apparent. Seed cotton yields of plant cohorts that developed foliar wilt symptoms early in the season (before 2,000 F degree-days) were variable but not much different in these years. This contrasted with cohorts of plants that first showed foliar symptoms late in the season (after 2,400 F degree-days) and cohorts of plants that showed no foliar symptoms of wilt. Regression analyses for 1982-1984 indicated moderate to weak correlations (r = 0.16-0.74) of the time of appearance of the first foliar symptoms and seed cotton yields.

Effects of Verticillium dahliae Infection of Cotton Plants (Gossypium hirsutum) on Potassium Levels in Leaf Petioles.

Two isolates of Verticillium dahliae, a black microsclerotial isolate and an isolate from potassium deficient cotton plants that forms white colonies on agar media, were examined for their effects on the potassium content of cotton plants. The potassium content of petioles from fully expanded leaves collected at random from branches 6 to 7 nodes below the terminal node were monitored during July and August in 1993 to 1995. Potassium contents of petioles from plants inoculated with V. dahliae did not differ significantly from plants injected with sterile water until the plants were nearing peak boll load. Both isolates caused a gradual development of potassium deficiency symptoms in leaves of inoculated plants and a decrease in petiole potassium, often accompanied by chlorosis and necrosis typical of Verticillium wilt. These results suggest that infection of cotton plants by V. dahliae causes an impairment in the uptake and translocation of potassium that is often associated with the development of potassium deficiency symptoms in leaves of plants with large boll loads.

Stress-related disorders. Recent developments in hospital treatment.

The stress treatment program at Ochsner, New Orleans, provides participants with knowledge of necessary skills and opportunities for rehearsal and practice within the setting. In addition, the modalities chosen reinforce what Lazarus and Opton described as "perceived control," which was found to be as instrumental as actual control in anxiety reduction. Upon return to day-to-day living, participants have the opportunity to use skills acquired and to receive reinforcement for doing so. The staff and patients found that traditional supportive and/or insight-oriented psychotherapy was as important as the vast array of behavioral training measures for inclusion in the patient's daily schedule. Individual therapy was provided to each patient up to 45 minutes daily, and one-hour group psychotherapy sessions were conducted three times a week. The belief that individual attention, social support, and insight into previous learning were critical ingredients to the appeal of individual psychotherapy was borne out in patient follow-up questionnaire data. Patients who were followed at the time of discharge and at six months in the Clark and Stiles study consistently ranked "individual session with their doctor" high within the ranking of some 14 treatment modalities or experiences. Collectively, the average of such rankings demonstrated "individual session" of equal benefit with the "stress management session," a purely behavioral/stress inoculation training experience. Such data therefore supported our initial belief that a marriage of the best of what traditional psychotherapy can offer with the best of behavioral medicine provides the optimal opportunity for growth and symptom improvement.