poster - International Conference of Agricultural Engineering

The soil used for the determination of desorption, extractable and bound residues was
acquired by a test of alachlor leaching, in accordance with the treatments. Figure 1 shows
the steps carried out in the leaching test.
Steps
5th
4th
3rd
Stages
Passage of 12 V p ultra pure water
Contact period
Application of alachlor on top of columns: 5 times the concentration of 3360 g of active
ingredient per hectare (NORTOX, 2011).
2nd Control 1 V p of MOT-B 1 V p of MOD-B 1 V p of MOT-E 1 V p of MOD-B
1st
Saturation with CaCl 2 (0.01 M)
FIGURE 1: Scheme of the stages performed during the leaching test.
After the leaching test, column soil was air dried, pounded to break up clods and sifted
in 2 mm mesh, and this material was stored in glass vials for subsequent extraction and
quantification of desorption, extractable and bound residues.
Adapting the methodology described by Lavorenti et al. (1998), in triplicate, 10 grams
of each column soil were weighed, and placed in 50mL polyethylene centrifuge tubes.
Moisture content was determined for the soil of each treatment to make the correction in the
soil mass to be used in the extraction. To these tubes, 20 mL CaCl 2 solution (0.01 M) was
added, and stirring was carried out on horizontal shaker at 200 rpm for 24 hours. After this
period, samples were centrifuged for 56 minutes at 6000 rpm (4757 g). Alachlor
concentration present in the supernatant of centrifuged samples was analyzed and
characterized as desorption residue. The same extraction procedures were carried out in
triplicate for a control sample contaminated with 50 mg L -1 of alachlor, to determine the
percentage of recuperation of method.
After this desorption, soil samples received organic solvents, chosen according to
polarity grade, with solvent / sample ratio of 2:1 (volume / weight). Four extractions were
performed: the first with a mixture of acetonitrile / water (1:1), the second and the third with
acetonitrile, and the fourth with ethyl acetate. At each addition of organic solvent to the
sample, horizontally mechanical stirring for 1 hour at 200 rpm was performed. Subsequently,
the sample was centrifuged for 56 minutes at 6000 rpm (4757 g) at 20 ° C. After each
centrifugation, the supernatant was reserved in glass vials properly identified according to
treatment and solvent used for extraction. In this material, which represents the fraction of
extracted residues, concentration of alachlor was determined and results were expressed in
mg in the soil column, based on the relationship between the concentration in the
supernatant and the volume of extracted solution, and the relationship between soil mass
used in the extraction and soil mass used in the column. According Lavorenti et al. (1997),
the molecules remaining in the soil after these procedures are considered to be bound
residues.
3. Results and discussion
It was observed in the balance of alachlor in the soil column (Table 2) that the leaching
was stronger MOD than in MOT, representing 88.50% and 90.98% of the total applied in