Faculty of Agricultural and Food Sciences

Permanent URI for this community

http://hdl.handle.net/1993/36338

Browse

Browsing Faculty of Agricultural and Food Sciences by Subject "Atrazine"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Open Access
    Near-infrared spectroscopy as a tool for generating sorption input parameters for pesticide fate modeling
    (2016-06-24) Singh, Baljeet; Farenhorst, Annemieke; McQueen, Ross; Malley, Dianne
    Sorption parameters (such as Kd values) are among the most sensitive input parameters in pesticide fate models. This study demonstrates that near-infrared spectroscopy (NIRS), in combination with batch equilibrium techniques, can be used to estimate Kd values, thereby increasing throughput of the many samples required to characterize spatial variability of pesticide sorption within fields. The Pesticide Root Zone Model (v. 3.12.2) was used to compare scenarios that used NIRS spectral data, pedotransfer functions and batch equilibrium methods as inputs for the calculation of 2,4-D and atrazine leaching in 591 soil horizons. Based on the 3,564 simulation runs conducted, we concluded that the added benefit of NIRS is most useful when the pesticides under study have small sorption potentials and short half-lives in soil. 2,4-D and atrazine sorption by soil was highly correlated to soil organic carbon content (SOC) in the fields under study. The feasibility of using NIRS to predict pesticide Kd values largely relies on the sorption of the pesticide being significantly correlated to SOC. In addition, successful regional approaches to predicting Kd values from NIRS spectral data can also be developed when the calibration model is derived by combining a set of fields where each has a similar statistical population characteristic in Kd values.
  • Thumbnail Image
    Item
    Open Access
    Sorption of pesticides by microplastics, charcoal, ash, and river sediments
    (Springer, 2022-04-27) Fatema, Marufa; Farenhorst, Annemieke
    In addition to sediments, pesticides can be sorbed to other constituents present in rivers including ash, charcoal, and microplastics. Pesticide sorption by microplastics has been studied for hydrophobic compounds such as the legacy insecticide DDT (dichlorodiphenyltrichloroethane) but not for current-use herbicides. The purpose of this study was to investigate to what extent 2,4-dichlorophenoxyacetic acid (2,4-D) (weak acid), atrazine (weak base), and glyphosate (zwitterion) are sorbed by microplastics (i.e., fiber, polyethylene beads, polyvinyl chloride (PVC), and tire fragments) and other river constituents (i.e., ash, charcoal, suspended and bottom sediments). DDT was included in the study to provide reference data that could be compared to known literature values. Batch equilibrium experiments were conducted following Guidelines 106 of the Organisation for Economic Co-operation and Development. Experiments utilized either a 1:100 solid/solution ratio with 0.1 g of a river constituent as the sorbent or a 1:5 solid/solution ratio with the sorbents consisted of 1.9 g bottom sediments mixed with 0.1 g of a river constituent. Background solutions included 0.01 M CaCl 2 or 0.01 M KCl, deionized water, and river water. Individual microplastics always sorbed >50% of DDT. Current-use herbicides had a weak affinity for microplastics (< 6%) except that a substantial amount of glyphosate was sorbed by PVC (32–36%) in 0.01M KCl and DI water. When river water was used as a background solution, rather than 0.01M KCl or deionized water, there was much less glyphosate sorption by PVC, ash, charcoal, and both sediments. This suggested that ions present in river water competed for sorption sites with glyphosate molecules. Across background solutions, sorption by sediments decreased in the order of DDT (91–95%) > glyphosate (36–88%) >atrazine (5–13%) >2,4-D (2–5%). Sorption of 2,4-D, atrazine, and DDT by ash and charcoal was always > 90% but < 35% for glyphosate. Relative to bottom sediments alone, the presence of ash or charcoal (5% by weight) with sediments significantly increased the sorption of 2,4-D, atrazine, and DDT. Microplastic additions (5% by weight) had no impact on all four pesticides’ sorption by sediments. Microplastics are not a strong sorbent for current-use herbicides, although there are exceptions such as glyphosate by PVC. Ions present in river water competed with glyphosate for sorption sites of river constituents. Hence, the types and concentrations of ions present in rivers might have some influence on the partitioning of glyphosate between the water column and solid phase, including glyphosate fate processes in rivers.