Movement of carbon disulfide vapor in soils as affected by soil type, moisture content, and compaction

Abstract does not appear. First page follows.

Introduction

The investigation of the movement of carbon disulfide vapor in soils was undertaken by Hagan4. This study is a continuation of Hagan’s work. He devised and reported the method, and presented sample data on Yolo soils. This paper involves soils in six series in both the dry and the moistened conditions. It deals with compaction in a more practical way than did Hagan’s paper. It gives more complete data on the effects of high and low soil moisture on permeability to carbon disulfide vapor. And it compares soils of similar texture in different soil series in both the dry and the moist condition.

Carbon disulfide vapor, being extremely toxic to plant life even at relatively low concentrations, has been used extensively as a herbicide, particularly in controlling such deep-rooted perennial weeds as wild morning-glory (Convolvulus arvensis L.). Although in most instances it has proved effective, the results are sometimes unsatisfactory. The purpose of this study is to throw more light on the factors that influence the behavior of carbon disulfide when injected below the surface of the soil.

Being a gas at ordinary temperatures, carbon disulfide moves throughout the soil. Several factors determine its distribution: differences in partial pressure of the gas from place to place in the soil, soil texture and structure, compaction, moisture content, and soil temperature. In addition, the soil has the capacity to sorb, or take up, carbon disulfide vapor. Obviously, under field conditions these factors must be considered together, because all act interdependently to condition the over-all behavior of the vapor in the soil. Since the numerous factors involved in the open field are beyond control, the study has been conducted under laboratory conditions. Although the natural soil is disturbed by removal from the field, the problem has been somewhat simplified by using laboratory procedures.

Since liquids and solids can sorb some gases and vapors, or can form new compounds with them, two. processes influence the movement of carbon disulfide vapor in the soil: sorption, tending to hold the chemical and restrict movement; and diffusion, tending to move it. Since the method used in these studies measured the net movement of vapor after sorption had come to equilibrium, diffusion alone was involved. A study of sorption as a process distinct from diffusional movement is contemplated at some future date.