TY - JOUR
T1 - Sorption and degradation of phorate as influenced by soil depth
AU - Bolan, N. S.
AU - Baskaran, S.
PY - 1997
Y1 - 1997
N2 - The sorption and degradation of a non-ionic insecticide (phorate) were examined using 14 soil samples collected at different depths from 2 soil types (Tokomaru and Egmont) which differed in their organic matter and clay mineralogy. Organic carbon and biological activity, as measured by substrate-induced respiration (SIR), decreased with soil depth. Sorption of phorate, as measured by the distribution coefficients (K(d)), was greater for the Egmont than for the Tokomaru soil and decreased with depth for both soils. The difference in K(d) values between the soils and soil depths was related mainly to the difference in the amount of organic carbon. The rate of degradation, as measured by the half-life (t( 1/4 )), decreased with soil depth except for the last 2 depths. The initial decrease in the rate of degradation was attributed to the decrease in the biological activity with depth. In the last 2 depths, since the sorption was low, most of the phorate tended to remain in soil solution, resulting in a slight increase in the rate of degradation. These results suggest that the changes in soil organic carbon with depth may be a reasonable indicator of microbial activity and subsequent changes in the rate of pesticide degradation as a function of soil depth.
AB - The sorption and degradation of a non-ionic insecticide (phorate) were examined using 14 soil samples collected at different depths from 2 soil types (Tokomaru and Egmont) which differed in their organic matter and clay mineralogy. Organic carbon and biological activity, as measured by substrate-induced respiration (SIR), decreased with soil depth. Sorption of phorate, as measured by the distribution coefficients (K(d)), was greater for the Egmont than for the Tokomaru soil and decreased with depth for both soils. The difference in K(d) values between the soils and soil depths was related mainly to the difference in the amount of organic carbon. The rate of degradation, as measured by the half-life (t( 1/4 )), decreased with soil depth except for the last 2 depths. The initial decrease in the rate of degradation was attributed to the decrease in the biological activity with depth. In the last 2 depths, since the sorption was low, most of the phorate tended to remain in soil solution, resulting in a slight increase in the rate of degradation. These results suggest that the changes in soil organic carbon with depth may be a reasonable indicator of microbial activity and subsequent changes in the rate of pesticide degradation as a function of soil depth.
KW - Biodegradation
KW - Distribution coefficient
KW - Half-life
KW - Phorate
KW - Sorption
KW - Substrate-induced respiration
UR - http://www.scopus.com/inward/record.url?scp=0030756281&partnerID=8YFLogxK
U2 - 10.1071/S96097
DO - 10.1071/S96097
M3 - Article
AN - SCOPUS:0030756281
SN - 0004-9573
VL - 35
SP - 763
EP - 775
JO - Australian Journal of Soil Research
JF - Australian Journal of Soil Research
IS - 4
ER -