Chlorsulfuron

64902-72-3

Active ingredient in herbicides.

Solid, crystalline, white (PESREG).

Odourless (PESREG).

357.78

The mobility of chlorsulfuron was studied with six different
soils under field conditions in the natural rainfall.
% C-14activity after 52 weeks in 10 - 20 cm soil depth
    15.0%    loam, C-14-phenyl-labelled
    20.2%    silt loam, C-14-phenyl-labelled
    10.5%    silt loam, C-14-triazine-labelled
    15.6%    silt loam, C-14-phenyl-labelled
    10.6%    silt loam, C-14-phenyl-labelled
    22.7%    sandy loam, C-14-phenyl-labelled
     6.0%    silty clay loam, C-14-phenyl-labelled
(PESREG)

The leaching behaviour of chlorsulfuron was studied in four
different soil (sandy loam, two silt loam and sandy soils)
columns. 
When chlorsulfuron was applied and immediately leached
from 76 to 83% of applied radioactivity percolated through the
columns with 20 inches of water within 20 hours. 
When it was
used aged soil columns (aged 30 days) 20 to 33% of applied
radioactivity leached from these columns (PESREG).

The mobility of chlorsulfuron in soil is very high first of all
in soils with high pH and low organic material. 
Ka: 0.45 - 0.69
(KEMI 1990).

Solubility in organic solvents:
                       wt/wt    wt/vol
hexane                10 ppm
toluene                0.3%     0.3%
methanol               1.8%     1.4%
acetone                7.0%     5.7%
methylene chloride     7.7%    10.2%
N,N-dimethylformamide 27.3%    27.4%
(PESREG)

The photodegradation of chlorsulfuron was studied in two soils
(sandy loam and silt loam) with simulated sunlight at 45°C in
the laboratory. 
The half-life was about two weeks in both soils.

The major product was 2-chlorobenzenesulfonamide (from
C-14-phenyl-labelled) and this compound increased to 30 - 35%
of the residual radioactivity after 4 weeks of photolysis
(PESREG).

Photolysis on surface of soil is not significant (KEMI 1990).

The photodegradation of chlorsulfuron (1 and 10 ppm) in aqueous
solutions was studied in the laboratory using a fluorescent
light source. 10% of the intact compound remained after 4 weeks'
exposure. 
The major decomposition products were
2-chlorobenzenesulfonamide and
2-amino-4-methoxy-6-methyl-1,3,5-triazine (PESREG).

The hydrolysis of chlorsulfuron was studied at pH 7 and pH 9.

Chlorsulfuron was stable for at least 4 weeks (PESREG).

Hyrdolysis of chlorsulfuron is strongly dependent on pH and
varies between temperatures, too. 
The half-life at pH 4 is 1
week at 20°C and 10 - 14 days at 10°C. 
In neutral and basic
coditions hydrolysis is more slowly (KEMI 1990).

At hydrolysis chlorsulfuron devides into two spieces;
2-chlorobenzenesulfonamide and
2-amino-4-methoxy-6-methyl-1,3,5-triazine. 
The last one
degrades very slowly. 
(KEMI 1990)

The half-life of chlorsulfuron (1-10 ppm) were one week (20°C)
and 10 - 14 days (10°C). 
The hydrolysis product
(C-14-phenyl-labelled) was 2-chlorobenzenesulfonamide. 
The
hydrolysis product (C-14-triazine-labelled) was first
2-amino-4-methoxy-6-methyl-1,3,5-triazine and then it by
stepwise loss of the methoxy and amino groups and
2,4-dihydroxy-6-methyl-1,3,5-triazine formed (PESREG).

The half-life of chlorsulfuron (C-14-phenyl labelled) under
aerobic conditions in a greenhouse was about 2 month (in sandy
loam and silt loam). 
The major degradation product in both soils
was 2-chlorobenzenesulfonamide increasing to 30 - 35% of the
residual radioactivity after 3 months and then slowly declining
to 12 - 13% after 9 months (PESREG).

The half-life of chlorsulfuron was 7 to 8 weeks in anaerobic
flooded soil (soil and distilled deionized water) system. 
The
degradationproducts were 2-chlorobenzenesulfonamide and
2-chlorophenylsulfonylurea (from C-14-phenyl-labelled) 
(PESREG).

The half-life of chlorsulfuron in soil (three sandy loams and
three silt loams) under field conditions was about 1 month (in
the acidic soils). 
In the alkaline soil the half-life was 2 - 3
months. 
The major degradation product was
2-chlorobenzenesulfonamide (from C-14-phenyl-labelled) and
2-amino-4-methoxy-6-methyl-1,3,5-triazine (from
C-14-triazine-labelled) (PESREG).

The biodegradation of chlorsulfuron was studied in sterile and
nonsterile silt loam soils.
                        14CO2 amount (%) after 7 weeks
                   C-14-phenyl-labelled  C-14-triazine-labelled
sterile soil              0.5                       2.5
nonsterile soil             5                        23
degradation product: 2-chlorobenzene-    2-amino-4-methoxy-
                     sulfonamide         6-methyl-1,3,5-triazine
The half-life was between one and two weeks (PESREG).

C-14-phenyl-labelled:
2-chlorobenzenesulfonamide

C-14-triazine-labelled:
2-amino-4-methoxy-6-methyl-1,3,5-triazine
2,4-dihydroxy-6-methyl-1,3,5-triazine

The hydrolysisproducts of chlorsulfuron is degraded by
microorganisms. 
Degradation is very slow. 
The half-life in the
field may be many months. 
In the laboratory the half-life is
obviously shorter, about 1 - 2 weeks at 25°C (KEMI 1990).

LD50, (24hr), >20 ug/bee, Glean *, KEMI 1990

There was no effect with chlorsulfuron (0.1 and 1.0 ppm, 35°C,
10 weeks) tratment on the soil nitrification (silt loam soil and
sandy loam soil) (PESREG).

Chlorsulfuron has no effect to the nitrification process in
soil (KEMI 1990).

NOEC: 0.00004 mg/l Lemna minor.

EC50 (14d): 0.00011 mg/l Lemna minor (KEMI 1990).