Open Vials Research Articles

A new method for the determination of radon in soil air by the “open vial” and integral counting with a liquid scintillation counter

A new method is described for the determination of Rn in soil gas. Open vials containing a liquid scintillator solution, suspended in a hole of the ground surface, absorb a fixed proportion of Rn present in soil gas. This allows the total Rn concentration to be determined. The method described is rapid, simple and reproducible. It should have many kinds of field application.

Volatilization of lindance from water in soil-free and flooded soil systems.

Volatilization of 14C-lindane from water in planchets and under flooded soil ecosystem was investigated. Lindane disappeared faster than parathion from planchets. More rapid loss of both insecticides occurred from water than from chloroform. Loss of lindane and parathion was related to measured losses of water by evaporation. During 5-day incubation under flooded soil conditions, disappearance of lindane was faster from open vials than from sealed vials, whereas in nonflooded soil, no volatile loss of the insecticide was evident despite water evaporation. Over 5 day incubation under flooded conditions, greater volatile loss of lindane occurred in sandy soil than in alluvial soil apparanetly due to greater adsorption to the soil colloids decreasing the insecticide concentration in the standing water on the laterite soil. Under identical conditions of water evaporation, lindane loss was directly proportional to its initial concentration in the water. These results suggest that considerable loss of soil applied pesticides can occur by volatilization from the standing water in flooded rice fields, particularly under tropical conditions.

Effectiveness of dichlorvos vapor against Xenopsylla cheopis in containerized cargo.

Nenopsylla cheopis (Rothschild) is a potential source of Plague if present in containerized cargo being returned to the United States from plangue-endemic areas. As a control Measure against these fleas, dichlorvos-impregnated resin strips containing 18.6% toxicant were effective in simulated field tests conducted at Savannah, Georgia, in Conexes (steel containers of 295 feet3 capacity). Fleas placed on white rats were exposed to dichlorvos vapor for 3, 6, 24, or 48 hours in Conexes with and without simulated cargo. A 24-hour exposure to a 5- or 10 × 2.5 × 0.25-inch strip killed all the fleas when the temperature averaged75°F or above. With a 48-hour exposure the treatment was effective even at 60°F. At 48 hours dichlorvos concentrations of 0.02-0.08 µg/liter produced 90 to 100% kills. Shorter exposure periods required higher concentrations to give the same level of effectiveness. Addition of simulated cargo, which decreased the volume of air in the Conexes, did not result in higher mortalities. Greater mortality resulted when fleas were exposed on rats than when exposed in open vials.

Stimulus to exsheathing of Nematodirus battus infective larvae

A study was made of the efficacy of HCl as a stimulus to exsheathing of infective larvae of Nematodirus battus. Some comparative observations were made on Haemonchus contortus. Over 90% of N. battus exsheathed in open vials of 0.6% saline acidified to pH 2.0 with HCl in 3 hours at 39 °C. Saturation of the saline with CO 2 had no effect. The exsheathment of N. battus and H. contortus was compared in a closed system in which 0.2% NaHCO 3 was mixed with varying quantities of HCl. Percentage exsheathment of H. contortus larvae fell from 80% to nil as the pH fell from 6 to 3, whereas for N. battus the pH effect was reversed, results falling from 96% to nil as the pH rose from 2 to 5. A very high proportion of N. battus also exsheathed in an approximately equivalent strength of NaCl (0.16%) acidified to the appropriate pH but in gaseous equilibrium with the atmosphere, whereas H. contortus did not. The results show that CO 2 cannot be considered an important component of the stimulus to exsheathing in N. battus.