The current state of the art regarding the use of chelating agents to extract heavy metal contaminants has been addressed. Results are presented for treatability studies conducted as worst-case and representative soils from Aberdeen Proving Ground’s J-Field for extraction of copper (Cu), lead (Pb), and zinc (Zn). The particle size distribution characteristics of the soils determined from hydrometer tests are approximately 60% sand, 30% silt, and 10% clay.Kamagra Achat En Ligne Sequential extractions were performed on the `as-received’ soils (worst case and representative) to determine the speciation of the metal forms. The technique speciates the heavy metal distribution into an easily extractable (exchangeable) form, carbonates, reducible oxides, organically-bound, and residual forms.http://www.pharmaciesans.com The results indicated that most of the metals are in forms that are amenable to soil washing (i.e. exchangeable+carbonate+reducible oxides). The metals Cu, Pb, Zn, and Cr have greater than 70% of their distribution in forms amenable to soil washing techniques, while Cd, Mn, and Fe are somewhat less amenable to soil washing using chelant extraction. However, the concentrations of Cd and Mn are low in the contaminated soil.Kamagra Achat France From the batch chelant extraction studies, ethylenediaminetetraacetic acid (EDTA), citric acid, and nitrilotriacetic acid (NTA) were all effective in removing copper, lead, and zinc from the J-Field soils. Due to NTA being a Class II carcinogen, it is not recommended for use in remediating contaminated soils. EDTA and citric acid appear to offer the greatest potenti.
al as chelating agents to use in soil washing the Aberdeen Proving Ground soils. The other chelating agents studied (gluconate, oxalate, Citranox, ammonium acetate, and phosphoric acid, along with pH-adjusted water) were generally ineffective in mobilizing the heavy metals from the soils. The chelant solution removes the heavy metals (Cd, Cu, Pb, Zn, Fe, Cr, As, and Hg) simultaneously. http://www.pharmaciesans.comUsing a multiple-stage batch extraction, the soil was successfully treated passing both the Toxicity Characteristics Leaching Procedure (TCLP) and EPA Total Extractable Metal Limit.Kamagra Acheter Belgique The final residual Pb concentration was about 300 mg/kg, with a corresponding TCLP of 1.5 mg/l. Removal of the exchangeable and carbonate fractions for Cu and Zn was achieved during the first extraction stage, whereas it required two extraction stages for the same fractions for Pb. Removal of Pb, Cu, and Zn present as exchangeable, carbonates, and reducible oxides occurred between the fourth- and fifth-stage extractions. The overall removal of copper, lead, and zinc from the multiple-stage washing were 98.9%, 98.9%, and 97.2%, respectively. The concentration and operating conditions for the soil washing extractions were not necessarily optimized.Kamagra Acheter Forum If the conditions had been optimized and using a more representative Pb concentration (∼12 000 mg/kg), it is likely that the TCLP and residual heavy metal soil concentrations could be achieved within two to three extractions. The results indicate that the J-Field contaminated soils can be successfully treated using a soil washing technique.
The spectral sensitivity between 448 nm and 655 nm of a dark-adapted bush baby, Galago crassicaudatus agisymbanus, Coquerel, was determined by an automated behavioural method.Kamagra Avis The animal was trained to work continuously, unattended, in a modified Y-maze with a food reward, going to a stimulus light whose intensity was subject to negative feed-back from the animal’s success. Digital counters recorded correct and wrong runs at each intensity level, and a threshold was derived from the frequency-of-seeing curve. http://www.pharmaciesans.com The mean absolute behavioural threshold of the bush baby was 0.13 log units less sensitive than the corresponding human threshold, and the most sensitive results about 0.5 log units more sensitive than the human.The behavioural spectral sensitivity results support the conclusion (Dartnall et al., 1965) drawn from the ERG spectral sensitivity, that fluorescence as well as tapetal reflectance contributes to the visual sensitivity of the bush baby.On détermine par une méthode automatique de comportement la sensibilitéspectrale entre 448 et 655 nm du Galago (Galago crassicaudatus agisymbanus, Coquerel) adaptéàl’obscurité.Kamagra Cialis L’animal est dresséàtravailler continuellement sans surveillance dans un labyrinthe modifiéen Y, avec une récompense de nourriture, se dirigeant vers une lumière dont l’intensitédiminue par feed-back négatif avec le succès de l’animal. Des compteurs numériques enregistrentàchaque niveau les succès etéchecs, et le seuil est déduit de la courbe de fréquence de vision.Le seuil abs.