Study 1. Laboratory investigation of the effect of Maxand on leaching of pesticides
Maxand was mixed at 20% by volume in quartz sand and placed 100 mm deep over a 40-cm layer of coarse quartz gravel suspended in a glass column 55 mm in diameter over glass wool and a rubber stopper with a single glass tube in the center for drainage. A second column containing unamended sand also was established in the same manner. A solution containing Diazinon and Phorate was added in equal amounts to the top of each column. The columns were leached with 1 liter of water.
The concentration of pesticide in the leachate water from each column was determined by EPA method #FL01040. The two pesticides were lower in the leachate from the column containing the Maxand (Table 1). Diazinon and Phorate in the leachate from the column containing the Maxand were below the detection limit of 1 microgram /L.
Table 1. Effect of Maxand on pesticide leaching from columns in the laboratory
|Pesticides in leachate (micrograms/L)|
|Quartz sand + Maxand||<1||<1|
Study 2. Effect of Maxand on retention of pesticides in soil in a golf green
After field plots were fully covered with grass,the pesticides Dursban and Fenamiphos were sprayed on the plots at labeled rates. Soil samples (0-10 cm deep) were analyzed for the pesticides retained by the soil mixes. The mix containing the Maxand contained more Dursban, Fenamiphos, and fenamiphos sulfone (a toxic metabolite of Fenamiphos) than the unamended soil (Table 2),demonstrating the pesticide retention properties of the Maxand.
Table 2. Effect of Maxand on pesticide retention in the soil twenty days after pesticide application
|Pesticide in soil(m g/m 2)|
|Sand/peat + Maxand||13.4||307.4||255.9|
Study 3. Effect of Maxand on leaching of pesticides in a golf green
Devices (lysimeters)for collecting percolate water were installed in the plots prior to the time the soil mixes were added. After the plots were fully covered with grass,the pesticides Dursban,and Fenamiphos were sprayed on the plots at labeled rates. Percolate water collected in the lysimeters was analyzed for the pesticides. Total pesticide leaching was determined. Leaching of Dursban,and the sulfone metabolite of Fenamiphos was reduced 100%, and 95%, respectively,by the inclusion of the Maxand into the soil mix (Table 3). No leaching of fenamiphos was observed in either treatment.The sulfone metabolite of Fenamiphos is known to be quite mobile,and toxic.
Table 3. Effect of Maxand on pesticide leaching over 51 days
|Pesticides (m icrogram s/m 2)|
|Sand/peat + Maxand||0||0||2,680|