John B. Pate

Atmospheric Gases and Particulates in Panama

The concentrations of trace gases in tropical air from samples taken on the Isthmus of Panama are compared with those reported by others. The role of a tropical land mass as a sink or source of atmospheric components is discussed.

The use of impregnated filters to collect traces of gases in the atmosphere : Part ii. collection of sulfur dioxide on membrane filters

Abstract HA and AA Millipore filters impregnated with 5% potassium bicarbonate and dried were found to be suitable for sampling concentrations of sulfur dioxide in air. The impregnation technique and filter loadings are described; flow rates are relatively unaffected by impregnation. The apparatus and procedures used for preparation and sampling known concentrations of sulfur dioxide in air are described. Comparisons of actual and theoretical concentrations in the 0.1 to 10 p.p.m. range showed that the concentrations prepared must be assayed. The collection efficiency of impregnated filters was evaluated for sodium tetrachloromercurate-(II) (less than 10% which is in contrast with the 100% efficiency found with TCM as a scrubbing solution) and potassium bicarbonate (greater than 95%). The capacity of the filters was such that sampling a 10 p.p.m. sample for at least 1 h is possible.

The Use of Hypodermic Needles as Critical Orifices in Air Sampling

Hypodermic needles are useful as convenient low-cost critical orifices to control the flow rate in air sampling. Variations in flow rate were less than five per cent for 41 needle gauge-length combinations. To provide maximum accuracy, a simple calibration procedure is described. Needles may be reused more than six times, if protected. Types of protectors are described. Resistances of protector, collector, and prefilter combinations affect criticality at nine liters/min. Simple sampling devices using needles as orifices are described.

Antarctic Atmospheric Chemistry: Preliminary Exploration

The particulate and trace gas content of polar air is very similar to that of tropical air despite diflerences in climatology and biotic activity. biologic particulates and moisture.

Measurements of atmospheric pollutants in the St. Louis area

Abstract Measurements of the concentrations of trace gases and particles have been made in the plume from metropolitan St. Louis at 80 and 120 km from the urban center. The concentrations of SO2, NO2, NO, NH3, H2S, aldehydes, CO, total hydrocarbons, and CFCl3 were determined. The concentrations of many of these gases were found to be significantly higher in the plume than outside the plume at these distances. Measurements were made near the ground and from an aircraft. The width of the plume was usually between 20° and 30°, which is less than had been expected. By comparing the concentrations measured at 80 km from the city with those measured at 120 km from the city, and using the decrease of conservative trace gases to account for loss through physical process, we have arrived at preliminary estimates of the decay rates for a few trace gases. The evidence is most compelling for sulfur dioxide, and it appears that, at ca. 100 km from the city, the overall half-life of SO2 is between 2 and 8 h.

Dynamic trace-gas dilution system

Abstract Apparatus has been developed for producing low gas concentrations in air samples of controlled characteristics. The gas diluting unit of the system consists of two Wosthoff rotating stopcock units placed in series and modified to eliminate concentration variation in ouput. The device can be used for all but the least stable gases, and will produce concentrations from 100 ppm to 0.1 ppb (1:1010). Lower concentrations could be achieved if it became desirable.

The Use of Impregnated Filters to Collect Traces Of Gases in the Atmosphere I. Suitability of Membrane Filters

Abstract The value, significance and advantages of the use of impregnated membrane filters as collectors for traces of gases in the atmosphere are described. An experimental test set-up for evaluating flow rates was used to show that the Adzumi flow equation describes the flow of gas through a membrane filter. Equations are developed to describe the flow rate as a function of the pressure drop across the filter and to describe the porosity as a function of pore size. Considerations of the theoretical molecular collisions with the wall are shown to indicate practicability of the use of membrane filters as efficient gas collectors.

Chemical (Atmospheric) and Biological Measurements in Panama. Volume 1. General

The report series (Vol. I) presents the chemical measurements made by the Atmospheric Chemistry Group of the National Center for Atmospheric Research (NCAR) for the project, Trace Chemistry of Tropical Atmospheres, supported in part by the Army Research Office (ARO), Durham, N.C. (contract DAHCO4 67-COO24). The study was conducted from February 1965 to January 1970, while the Atmospheric Chemistry Group was part of the NCAR Laboratory of Atmospheric Science. The report series also includes the chemical and biological measurements made by the U.S. Army Tropic Test Center (USATTC) for the project. Volume I of the report series describes the project and the 34 sampling sites used for chemical and biological sampling (most of which are in the Canal Zone).

Rack for Square Cuvettes

For many spectrophotomemc determinations, it is convenient to use a reasonably large number of cuvettes, rather than rinsing after each determination. When the color reaction used is time dependent, or when the samples are such that a dry cuvette is needed, a number of cuvettes are required. In such a case, additional spectrophotometer cuvette holders are usually obtained to hold the samples. Since these are not intended to use as cuvette racks, they tend to be expensive, corrodible, and hkely to spill.