Behavior of Dinitroaniline Herbicides in Soils

Abstract

The behavior and dissipation of 26 dinitroaniline herbicides in soils are reviewed. Some of the compounds also are referred to as dinitrotoluidines, -benzen(e)amines, -benzenediamines, -cumidines, -benzenesulfonamides, -acetophenones, and sulfonylsulfilimines. All dinitroanilines are sorbed to soil particles, particularly to organic or humic substances, and are nearly immobile in soils. Soil K values range from 7 to 117 and KOCvalues range from 80 to 471 000. Compounds with vapor pressures greater than 50 × 10-6mm of Hg at ambient temperatures were reported to volatilize and diffuse through, and out of, the soil in significant amounts, depending on temperature and moisture conditions. Greater losses occurred from warm, moist soils than from cool, dry soils. Photodecomposition of dinitroanilines on soil surfaces was low but occurred when the chemicals were present in the vapor state or in aqueous solutions. Bioavailability of the chemicals decreased as organic matter contents of the soils increased. Dinitroaniline herbicides were degraded primarily by soil microorganisms, and fungi were the major organisms involved. Degradation proceeded faster under anaerobic conditions than under aerobic conditions and faster under warm, moist conditions than under cool, dry conditions. Half-life values for dinitroanilines ranged from 7 to 27 days under anaerobic conditions and from 19 to 132 days under aerobic conditions. The chemicals did not affect most soil microflora; and any significant effects reported were of short duration.