Layer 
Soil texture (Gr/Sa/Si/Cl)†

Organic matter 
Cation exchange capacity 
Bulk density 
pH‡

Water content at tensions (cm) 
0§

100 
15,000 
cm 
% 
cmol_{c} kg^{−1}

g cm^{−3}

 m^{3} m^{−3}

Clay

0–30 
1.3/6.0/46.2/46.5 
4.4 
28.4 
1.24 
7.2 
0.524 
0.359 
0.193 
30–60 
0.6/2.7/40.6/56.1 
0 
33.6 
1.43 
7.4 
0.477 
– 
0.249 
60–90 
0.2/1.8/37.4/60.6 
0 
– 
1.46 
7.4 
0.468 
– 
0.297 
Sand

0–30 
0/87.8/4.5/7.7 
2.0 
4.7 
1.43 
7.4 
0.448 
0.180 
0.034 
30–60 
0/95.4/4.6/0 
1.0 
1.8 
1.47 
6.4 
0.427 
0.165 
0.019 
60–90 
– 
1.0 
1.4 
1.46 
7.0 
0.450 
0.065 
0.016 
^{†}
Gr = gravel, >2 mm; Sa = sand, 0.06–2 mm; Si = silt, 0.002–0.06 mm; Cl = clay, <0.002 mm.
^{‡}
Determined in water.
^{§}
Equivalent to porosity.
Molecule 
Molecular weight 
RT (min) 
Quantification ion (m/z, % relative abundance) 
Qualification ion (m/z, % relative abundance) 
AMPA†

371 
4.49 
126 (100) 
302 (23) 
AMPA‡

375 
4.49 
130 (100) 
306 (22) 
Glyphosate 
511 
5.35 
411 (100) 
384 (50) 
Glyphosate‡

513 
5.35 
413 (100) 
386 (48) 
^{†}
AMPA = aminomethylphosphonic acid.
^{‡}
Internal standard.
View Full Table  Close Full ViewTable 3.Freundlich coefficients (K
_{f}) (± SE, n = 10) for adsorption of glyphosate obtained by nonlinear regression according to Eq. [1]
Soil 
K
_{f}

1/n

R
^{2}

 μg^{1n
} (mL)
^{n}
g^{−1}

– 
– 
Sand topsoil 
40.0 ± 2.9 
0.92 ± 0.04 
0.997 
Sand subsoil 
28.7 ± 1.2 
0.82 ± 0.02 
0.998 
Clay topsoil 
118 ± 4.4 
0.95 ± 0.01 
1.000 
Clay subsoil 
165 ± 10.7 
1.03 ± 0.02 
0.999 
View Full Table  Close Full ViewTable 4.Coefficients (± SE, n = 12) obtained by nonlinear regression for degradation of glyphosate according to firstorder kinetics (Eq. [2]).
Soil 
c
_{G0}
†

k

R
^{2}

t
_{1/2}
‡

DT_{90}
§

 mg kg^{−1}

d^{−1}

– 
d 
d 
Sand topsoil 
11.21 ± 0.33 
0.041 ± 0.003 
0.978 
16.9 
56.2 
Sand subsoil 
12.27 ± 0.19 
0.019 ± 0.001 
0.985 
36.5 
121 
Clay topsoil 
11.99 ± 0.15 
0.0063 ± 0.0005 
0.948 
110 
365 
Clay subsoil 
11.61 ± 0.41 
0.0046 ± 0.0014 
0.562 
151 
501 
^{†}
c
_{G0} = initial concentration of glyphosate; k = firstorder rate coefficient for degradation; t1/2, = halflife; DT_{90} = time for 90% degradation.
^{‡}
Calculated as ln(2)/k.
^{§}
Calculated as ln(10)/k
View Full Table  Close Full ViewTable 5.Coefficients (± SE, n = 12) obtained by nonlinear regression for formation and degradation of aminomethylphosphonic acid (AMPA) according to Eq. [4]
Soil 
k
_{1}
†

k
_{2}

t
_{1/2} ‡

R
^{2}

 d^{−1}

d 
– 
Sand topsoil 
0.0216 ± 0.0011 
0.0115 ± 0.0019 
60.4 
0.965 
Sand subsoil 
0.0092 ± 0.0005 
0.0076 ± 0.0018 
91.3 
0.988 
Clay topsoil 
0.0063§ ± 0.0005 
0.0199 ± 0.0013 
34.9 
0.973 
Clay subsoil 
0.0028 ± 0.0006 
0.0071 ± 0.0087 
97.6 
0.901 
^{†}
k
_{1} = firstorder rate coefficient for degradation of glyphosate to AMPA; k
_{2} = firstorder rate coefficient for degradation of AMPA ; t
_{1/2} = halflife.
^{‡}
Calculated as ln(2)/k
_{2}
^{§}
In the clay topsoil, k
_{1} became 0.0073, i.e., larger than k (firstorder rate coefficient for degradation; Table 4), leading to a formation fraction > 1, and was therefore set equal to k
View Full Table  Close Full ViewTable 6.Derived parameter values on fraction of glyphosate degraded to aminomethylphosphonic acid (AMPA) (k
_{1}/k), rate constant for formation of sarcosine (k
_{3}), incubation time (t
_{Amax}) at which the AMPAconcentration peaks (c
_{Amax}), and c
_{Amax} as fraction of initially added glyphosate.
Soil 
k
_{1}/k
†

k
_{3}
‡

t
_{Amax}
§

c
_{Amax}
¶

c
_{Amax} fraction#

 – 
d^{−1}

d 
mg kg^{−1}

% 
Sand topsoil 
0.53 
0.0190 
43.4 
2.40 
32.4 
Sand subsoil 
0.48 
0.0098 
80.4 
2.12 
26.2 
Clay topsoil 
1 
0 
84.7 
1.47 
18.6 
Clay subsoil 
0.61 
0.0018 
174 
1.34 
17.5 
^{†}
Values of k (firstorder rate coefficient for glyphosate degradation) from Eq. [2] (Table 4) and of k
_{1} (firstorder rate coefficient for degradation of glyphosate to AMPA) from Eq. [4] (Table 5).
^{‡}
k
_{3} = k – k
_{1}
^{§}
Calculated according to Eq. [5]
^{¶}
Obtained by inserting derived values of k, k
_{1}, k
_{2}, c
_{G0}, and t
_{Amax} into Eq. [4]
^{#}
Calculated as (c
_{Amax} × 1.52 × 100)/c
_{G0}, where 1.52 is the stoichiometric factor for conversion of AMPA to glyphosate concentration.
View Full Table  Close Full ViewTable 7.Water inputs to the lysimeters and mean annual amounts of leachate from the lysimeters to which glyphosate was applied (± SD; n = 2 for sand, n = 3 for clay)
Year 
No. of days 
Precipitation + irrigation 
Leachate 
Sand lysimeters 
Clay lysimeters 

 mm 
2006†

104 
232 
169 (± 1.4) 
156 (± 4.7) 
2007 
365 
550 
229 (± 3.2) 
158 (± 9.1) 
2008‡

261 
432§

174 (± 13) 
148 (± 4.0) 
Total 
730 
1214 
572 (± 17) 
461 (± 15) 
^{†}
Measurements made during the period 18 September to 31 December.
^{‡}
Measurements made during the period 1 January to 18 September.
^{§}
Includes 22 mm irrigation.