Herbicide Transport on Wind‐Eroded Sediment

Although wind erosion is a pervasive soil degradation problem on the semiarid Canadian prairies, few studies have been conducted on wind‐eroded sediment as an environmental pathway for herbicide transport. An experiment was conducted on a clay loam soil at Lethbridge, AB, in 1993 to 1994, to examine wind‐eroded sediment as a transport mechanism for two soil‐incorporated [trifluralin (2,6‐dinitro‐ N,N ‐dipropyl‐4‐trifluoromethylaniline) and triallate ( S ‐2,3,3‐trichloroallyl diisopropylthiocarbamate)] and four surface‐applied herbicides [diclofop {(±)‐2‐[4‐(2,4‐dichlorophenoxy)phenoxy]propanoic acid), bromoxynil (3,5‐dibromo‐4‐hydroxybenzonitrile), mecoprop {(±)‐2‐(4‐chloro‐2‐methylphenoxy)propanoic acid}, and 2,4‐D (2,4‐dichlorophenoxyacetic acid)]. The concentrations of diclofop and bromoxynil in sediments decreased with increasing capture height, with the 100‐cm height having significantly lower concentrations (diclofop, 627 µg kg −1 ; bromoxynil, 70 µg kg −1 ) than the 10‐cm height (diclofop, 1132 µg kg −1 ; bromoxynil, 231 µg kg −1 ). This implies that these herbicides were primarily associated with larger soil particles captured closer to the soil surface. For the soil‐incorporated herbicides, concentrations were significantly higher in the surface soil (0–2.5 cm) than in the wind‐eroded sediment, whereas concentrations of surface‐applied herbicides were generally higher in wind‐eroded sediment than in surface soil. Overall wind erosion losses (expressed as a percent of amount applied) of the two soil‐incorporated herbicides (1.5%) were about three times lower than those of the four surface‐applied herbicides (average loss, 4.5%). The results demonstrate the potential hazard of environmental transport of herbicides on wind‐eroded sediment and its associated implications for off‐site air and water quality.