Jh. Smelt et al., TRANSFORMATION OF ALDICARB SULFOXIDE AND ALDICARB SULFONE IN 4 WATER-SATURATED SANDY SUBSOILS, Pesticide science, 44(4), 1995, pp. 323-334
The transformation of aldicarb sulfoxide and aldicarb sulfone was stud
ied in incubations with water-saturated subsoils under simulated field
conditions at 10 degrees C. The subsoils were collected at four locat
ions from beneath the water table at a depth of 2.5 to 3.5 m. In three
of the subsoils, the half-life of sulfoxide, incubated at concentrati
ons of 0.14-0.17 mg litre(-1), ranged from 0.7 to 2.8 years. At higher
concentrations (8-13 mg litre(-1)), its half-life ranged from 3.4 to
6.4 years. At the lower concentration, a large fraction of sulfoxide w
as transformed into sulfone. The rates of transformation of the sulfon
e at the lower concentration in the three subsoils corresponded to hal
f-lives of 3.3 to 8.1 years, but in only one subsoil was a significant
transformation rate (half-life 6.7 years) measured at the higher conc
entration during the 2.3-year incubation period. The half-lives at the
lower concentrations were more like those in field studies, and perha
ps would still underestimate transformation rates under field conditio
ns. After a year, 2.5-15% of the higher sulfoxide and sulfone doses ha
d been trapped as [C-14] carbon dioxide. In the fourth subsoil, with m
ore anaerobic conditions, the half-life of sulfoxide at both concentra
tions was less than 0.02 year and that of sulfone was about 0.04 year.
Four or five radio-labelled transformation products could be traced i
n this subsoil and about half of the dose of both compounds was trappe
d as [C-14] carbon dioxide.