cis-4-[3-(p-tert-butylphenyl)-2-methylpropyl]-2,6-dimethylmorpholine

Phototransformation in air

Link to relevant study record(s)

Reference

Endpoint:

phototransformation in air

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Study period:

March 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Qualifier:

according to guideline

Guideline:

other: BBA IV 6-1

Principles of method if other than guideline:

calculated according to Atkinson's method (Atkinson 1987)

Details on test conditions:

The rate constant for reactions of BAS 421 with OH radicals in the atmosphere was calculated according to Atkinson's method (Atkinson 1987).

Key result

DT50:

2.9 h

Test condition:

calculated according to Atkinson's method (1987)

At first, the rate constant k_OH of the active substance was estimated based on the chemical structure. The resulting value was

                   k_OH  = 132  x 10 ^–12 cm³ / s

Because of a constant average OH radical concentration in the troposphere, the degradation of the active substance follows pseudo-first order kinetics with the rate constant k’ = k_OH ^. (OH radicals):

                   -d(fenpropimorph) = k´(fenpropimorph)

The half life of this process was calculated by the following equation:

                   t_1/2 = ln2/k' = ln2/k_OH ^. (OH radicals).

The diurnally and seasonally averaged tropospheric OH radical concentration ((OH radicals)) for the northern hemisphere is 5 ^. 10⁵ cm^-3 (Crutzen, P.J. (1982) The Global Distribution of Hydroxyl, in Goldberg, E.D. (editor), Atmospheric Chemistry, Springer Verlag Berlin).

The half life of fenpropimorph was calculated to be 2.9 h.

Conclusions:

The half life of fenpropimorph was calculated to be 2.9 h.

Description of key information

Fenpropimorph has a high volatilisation potential. If reaching the troposphere, fenpropimorph is degraded very fast by photochemical processes with a half-life of 2.9 h.

Key value for chemical safety assessment

Half-life in air:

2.9 h

Degradation rate constant with OH radicals:

0 cm³ molecule-1 s-1

Additional information

The potential for short-range transport via air, i.e. volatilisation from the area of application and subsequent deposition on adjacent non-target areas was investigated for fenpropimorph in a wind tunnel system (BASF DocID 2004/1015210, 2004/1015214, 2004/1022511). Fenpropimorph containing formulation BAS 421 12 F (Corbel, 750 g/l) was applied together with formulated reference standard lindane to winter wheat (post emergence).

The trial was conducted on May 19, 2004 under controlled conditions in a wind tunnel at the Dienstleistungszentrum Ländlicher Raum (DLR) - Rheinpfalz, Breitenweg 71, D-67435 Neustadt, Germany. The wind tunnel has a length of approximately 55 m, a width of 6.5 m and a height of 3.1 m. At one end of the tunnel a wind engine with 26 synchron working fans was established. Between the wind engine and the target area there was a 5 m distance. The target area was 4 m wide and 25 m long (100 m²) with 1.25 m distance to the boundary at each side. The wind speed was set to 2 m/sec.

The flat target plot was cultivated with winter wheat ("Ritmo", 350 seeds/m², BBCH 51), the surrounding area was grown with grass. Spraying was carried out in the morning (8:26 a.m. Central European Time) using a portable 4 m carbon boom sprayer with eight drift reducing nozzles (six Lechler ID 120-03 and one Lechler IS 80-03 at each end) at a pressure of 2.9 bar and a speed of about 2.25 km/h.

A theoretical tank mixture consisting of nominal 1 l/ha BAS 421 12 F (750 g/l fenpropimorph) and 550 ml/ha BAS 004 AA I (150 g/l lindan) in a water volume of 400 l/ha was adapted to the target area of 100 m², i.e. the actual volume of the application solution was 3935 ml, the actual application time was 40 seconds while walking 25 m with the spraying device. The amount of fenpropimorph and lindane in the application solution was determined to be 1.61 g/l and 0.16 g/l corresponding to 633 g/ha and 64 g/ha, respectively.

Water containing stainless steel container were placed at different distances downwind of the application area. Samples for analyses were taken at 8 h (10 and 20 m distance) and at 24 h following application and the concentration values for fenpropimorph and lindane were determined (BASF DocID 2004/1015214).

Two samples with about 1 l volume were collected from every pan at each sampling. 200 ml aliquots of the water samples were automatically sucked through C₁₈ columns and the analytes eluted with dichloromethane/methanol 9 + 1 (v/v) using a ZYMARK Autotrace. After concentration using a rotary evaporator the final analysis was performed by GC-MS according to analytical method CP 364 (BASF DocID 2000/1014823).

The results for the reference standard lindane clearly demonstrated that the experimental and climatic parameters of the wind tunnel were feasible to determine the deposition of volatile compounds over a study period of 24 hours. At a distance of 1 m beside the treated field 2.4 % of the applied lindane occurred in the pans. Between 3 m and 20 m distance 0.5-0.7 % of the applied amount was detected after 24 hours, i.e. the concentration of lindane significantly declined with increasing distance.

Fenpropimorph was detected in minor amounts of 0.01-0.06 % of the applied material. Neither sampling time (8 hours resp. 24 hours) nor the distance from the treated field lead to significant differences in the concentration of fenpropimorph. Even at a distance of 1 m beside the treated field no significant deposition occurred (0.04 % of applied after 24 hours). Therefore, transport via deposition after volatilisation plays only a minor role.