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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