Search Results

You are looking at 1 - 8 of 8 items for

  • Author or Editor: Donald F. Gatz x
  • Refine by Access: All Content x
Clear All Modify Search
Donald F. Gatz

Abstract

This work was undertaken to measure background silver in Illinois precipitation in the absence of any known seeding operations in on near Illinois. The rainfall-weighted mean concentration in samples from several stations was 73 ng l −1. This is somewhat higher than has been found in unseeded precipitation in other parts of North America, but not high enough to preclude wind-blown soil dust as a primary source.

Full access
Donald F. Gatz

Abstract

Speculation concerning effects of pollutants on weather, especially rainfall, has intrigued scientists and laymen alike in recent years. Results from Project METROMEX suggest that rainfall is increased after a moving raincell intersects the urban plume. This paper investigates correlations between rainfall and indices of aerosol pollutant source strength to see whether a causative mechanism might be suggested.

Although the correlations between rainfall in certain areas and the source strength of three groups of urban aerosols are significant enough to warrant further investigation, physical relationships do not support an aerosol involvement in the urban rainfall anomaly.

Full access
Donald F. Gatz

Abstract

Decisions on controlling emissions to reduce atmospheric aerosol concentrations require accurate information on ambient concentrations, composition and sources. This paper shows how filter sampling of ambient aerosols, followed by multi-element analysis of the filters and factor analysis of the data, were used to identify sources in the St. Louis area.

Nearly 400 filters, collected at 12 sites in the St. Louis area from 1973–75 as part of project METROMEX, were analyzed by ion-excited x-ray fluorescence for 10–20 elements. Factor analyses were performed separately for each site, revealing a number of common area-wide sources and several local sources. Widespread sources include soil dust and flyash, secondary sulfates, auto exhaust and metals. Local sources identified include a titanium pigment plant and a secondary lead smelter.

Full access
Donald F. Gatz

Abstract

Concentrations of artificial radioactivity and plant pollens in rain have been found to vary in phase during convective storms. Because pollens are tracers for low-altitude air, this result is most simply explained by low-altitude input of both pollens and radioactivity in the convective updraft.

The low-altitude input hypothesis was tested by mass-budget methods. Comprehensive mesometeorological and radio-chemical data collected from a segment of the severe squall line in central Oklahoma on 10 May 1964 were used in the analysis. The radioactivity inflow rate below 650 mb was estimated kinematically using serial soundings in the storm inflow and the concentration of radioactivity in ground-level air. Total input was computed by multiplying the inflow rate by the time required for the storm to cross a network of 10 ground-level rain samplers.

Comparison of inflow and deposition over the sampler network shows that inflow of airborne radioactivity to the storm at low altitudes can account for artificial radioactivity deposited in the rain.

Full access
A. Nelson Dingle and Donald F. Gatz

Abstract

The rain cleansing patterns observed in five rain situations, all characterized by convective structures, are presented. The data comprise radioactivity and pollen concentrations measured in sequential samples of rain water from each rain. The rain systems are categorized, three being classed as “well-organized,” and the remaining two as “diffuse” convective systems. The temporal patterns of rain water contamination are relatively consistent in the well-organized showers, but much less so in the diffuse ones. Because the scavenging patterns of the pollens are quite parallel with those of the long-lived radioactive debris, it is inferred that both classes of contaminant enter the rain-producing parts of the showers by the same route, namely, in the low-level air that forms the convective updraft. It is therefore proposed that contamination that enters the troposphere from above (the stratospheric nuclear test debris reservoir) is not importantly scavenged until it passes through a low level tropospheric trajectory. The cleansing accomplished by the diffuse showers shows a tendency to be quite spotty, leaving pockets of contaminated air relatively unaffected between showers.

Full access
A. Nelson Dingle, Donald F. Gatz, and John W. Winchester

Abstract

In an effort to determine whether it is feasible to use tracer techniques in the study of circulations and rain scavenging processes in severe convective storms, a pilot experiment using indium as tracer was conducted. A total of 200 gm of indium was released over a period of 21 min into the updraft feeding a relatively small convective system. The tracer was released by means of pyrotechnic flares from an airplane flying at about 3200 ft altitude. The rainfall from the system was sampled at the ground by means of an array of samplers placed and recovered by two mobile units. Analysis of the samples compared against analyses of untagged rain samples and reagent backgrounds of indium distinctly indicates the presence of tracer indium in a reasonable distribution pattern.

Full access
Donald F. Gatz, A. Nelson Dingle, and John W. Winchester

Abstract

In a test of the use of indium as a particulate atmospheric tracer, both tagged and untagged rain showers were sampled at ground level in Oklahoma during May 1967. In 29 samples of untagged rain 6±3 nanograms of In per liter were found, indicating a natural background somewhat above the reagent blank of about 2 ng liter−1. After aircraft injection at cloud base of 200 gm of indium, as finely divided particles from pyrotechnic flares, a maximum of 40 ng liter−1 was found in the rain, and a pattern of localization of the tracer indium was revealed in an array of 14 samplers spaced over 11 km. The procedure for analysis began in the field with 1) addition of HC1 to the polyethylene samplers before rain was collected to ensure solubility of the tracer, 2) filtration to remove suspended solids, 3) addition of lanthanum internal standard, Fe+++, and NH3 to each 1-liter sample to precipitate In and La with Fe(OH)3, and 4) membrane filtration of the Fe(OH)3. At The University of Michigan the procedure continued with 5) reactor neutron activation of the filters, 6) separation of In from La by isopropyl ether extraction from HBr solution, and 7) assay of In and La radioactivities by β and γ, counting, respectively. The sensitivity of the method is determined by the natural background of the indium found.

Full access
Donald F. Gatz, Richard F. Selman, Richard K. Langs, and Richard B. Holtzman

Abstract

A sequential rain sampler has been developed that collects up to 70 samples from 35–70 mm of rain. Each sample has a volume of 500–1000 ml and represents 0.5–1.0 mm of rain. After all bottles are filled, any additional rain is automatically discharged. The area of the collector is 1 square meter. All surfaces touched by the rain water, including the bottles used to contain the samples, are polyethylene or Teflon. After every sample, an event mark is recorded on a strip chart; at the first mark, the chart speed increases from 3.8 cm hr−1 to 3.8 cm min−1. This provides adequate resolution between event marks for the computation of rainfall rate. If a time reference is provided while the chart is on fast speed, the starting and ending times of individual samples are known within 1 sec.

Full access