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This article in JEQ

  1. Vol. 25 No. 1, p. 192-202
     
    Received: Dec 16, 1994


    * Corresponding author(s): yates@ucracl.ucr.edu
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doi:10.2134/jeq1996.00472425002500010025x

Methyl Bromide Emissions from a Covered Field: II. Volatilization

  1. S. R. Yates *,
  2. F. F. Ernst,
  3. J. Gan,
  4. F. Gao and
  5. M. V. Yates
  1. USDA-ARS, Soil Physics and Pesticide Res. Unit, U.S. Salinity Lab., 450 Big Springs Road, Riverside, CA 92507;
    Dep. Soil and Environ. Sci., Univ. of California, Riverside, CA 92521.

Abstract

Abstract

An experiment to investigate the environmental fate and transport of methyl bromide in agricultural fields is described. The methyl bromide volatilization rate was determined as a function of time for conditions where methyl bromide was applied at a rate of 843 kg in a 3.5-ha (i.e., 240 kg/ha) field covered with plastic at a depth of 25 cm. Three methods were used to estimate the methyl bromide volatilization rate, including: the aerodynamic, theoretical profile shape and integrated horizontal flux methods. The highest methyl bromide volatilization rates were at the beginning of the experiment. Within the first 24 h, approximately 36% of the applied methyl bromide mass was lost. Diurnally, the largest volatilization rates occurred during the day when temperatures were high and the atmosphere was unstable. Cooler temperatures, light winds, and neutral to stable atmospheric conditions were present at night, reducing the flux. The total emission calculated using these methods was found to be approximately 64% (±10%)of the applied mass. A mass balance was calculated using each flux estimation technique and several methods for analyzing the data. The average mass recovery using all the flux methods was 867 kg (±83 kg), which was 102.8% (±9.8%) of the applied mass (i.e., 843 kg). The range in the mass balance percent (i.e., percent of applied mass that is measured) is from 88 to 112%. The averaged mass balance percent for the aerodynamic method, which involved using the measured data directly, was approximately 100.8%. The total emission calculated using the aerodynamic method was found to be approximately 62% (± 11%) of the applied mass.

This study was supported by USDA Coop. State Res. Service Agreement no. 92-34050-8152.

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