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Table 2 Panel A: Half-lives (DT50) and DT90 values of 2,4-D, 2,4-DCP, and 2,4-DCA. Panel B: Half-lives (DT50) and formation fractions of metabolites resulting from sequential fitting, not considering the reversibility of the reaction 2,4-DCP to 2,4-DCA

From: Degradation and sorption of the herbicides 2,4-D and quizalofop-P-ethyl and their metabolites in soils from railway tracks

Panel A
  pH Corg T [°C]/ DT50/DT90 [days], best fita
(CaCl2) [%] M [%] 2,4-D 2,4-DCP 2,4-DCA
Soils from railway tracks
 EB 7.7 0.15 20/35 35/115 SFO 27/129 DFOP 82/271 SFO
 MBS 7.6 0.31 20/60 39/131 SFOc 1.0/7.0 FOMC 9.2/31 SFO
 MR 7.6 ≈ 0.04 20/72 > 1000/> 1000 SFOc 4.1/18 DFOP 0.3/2.1 DFOP
 CS 7.5 < 0.06 20/65 203/675 SFOc 66/519 FOMC 101/335 SFO
    DT50 [days], modeling endpointsb
 Geom. mean, 20 °C, pF 2 ≈ 0.1   115 12 14
Agricultural soils [13]
 Min–max 6.2–7.8d 0.9–3.7 20/50 1.6–95 3.2–6.2 11–16
 Geom. mean, 20 °C, pF 2 1.5/1.8/1.8e   4.4 7.0 10
Panel B
  Sequence of fitting DT50 [days]
2,4-Df
Formation fraction [%]g DT50 [days]
2,4-DCPf
Formation fraction [%]g DT50 [days]
2,4-DCAf
EB 2,4-D → 2,4-DCP → 2,4-DCA → sink 35 SFO 34 35 SFO 32 33 SFO
  2,4-DCP → 2,4-DCA → sink    28 DFOP 12 103 SFO
MBS 2,4-D → 2,4-DCP → sink 40 SFOc 16 2.6 SFOc   
  2,4-DCP → 2,4-DCA → sink    1.0 FOMC 6.4 16 SFO
MR 2,4-DCP → 2,4-DCA → sink    4.1 DFOP 2.2 11 SFO
2,4-DCA → 2,4-DCP → sink    4.8 SFO 79h 0.3 DFOP
CS 2,4-DCP → 2,4-DCA → sink    66 FOMC 2.5 101 SFO
  1. T: temperature, M: moisture in % of water holding capacity
  2. aSFO: single first-order kinetics, DFOP: double first-order in parallel model, FOMC: first-order multi-compartment model. χ2 values < 10%
  3. bCalculated according to [26], for details see Additional file 1: Table S4 and Additional file 2: Kinetic fits
  4. cOnly the slow initial phase was considered
  5. dMeasured in H2O
  6. eIn degradation studies with 2,4-D/2,4-DCP/2,4-DCA
  7. fBest fit. χ2 values < 12%, except for 2,4-DCA in CS (20%)
  8. gVolatilization may have contributed to overall dissipation (i.e., actual formation may have been higher)
  9. hBack reaction from 2,4-DCA to 2,4-DCP