|Mulrooney, Joseph - Joe|
Submitted to: ASAE Annual International Meeting
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Spray drift is an ever present problem. A key element in solving problems of spray drift is the ability to accurately sample spray droplets moving through the air. Six different air-sampling devices were evaluated for their drift collection efficiency. Results showed that 47 percent of the spray from a ground sprayer reached the soil from a 3.9 foot height, while 0.7% and 0.09% were collected at 18 and 24 meters downwind respectively. Little difference in residue collection between high volume air samplers, rotating rod samplers, or vertical string samplers was observed. A rotary disk impactor failed to collect any of the droplets from the drifting spray cloud. These results will aid researchers in selecting effective devices for spray drift assessment.
Technical Abstract: Collection of airborne spray drift of malathion released from a ground sprayer was investigated using six types of samplers: 1) alpha cellulose fallout sheets, 2) high-volume air samplers, 3) rotary disk impactor and two bubblers (RDI), 4) rotating rods, 5) string samplers, and 6) poly- urethane foam plugs (PUF). Spray deposit was determined with malathion residue collection on alpha cellulose sheets spaced at 3-m intervals in th spray swath and at 6-m intercals along a line perpendicular and downwind from the spray swath. Spray drift residues were collected at four stations along a 90-m sampler line located 30-m downwind and parallel to the spray swath. Gas chromatographic analysis was used to quantify the concentration of malathion. Results indicated that fallout deposits 1) in the spray swath, 2) at 6, 12, 18, or 24 m, and 3) at 30-m downwind from the spray swath, edge were approximately 1) 47, 2) 0.7, and 3)0.09 percent of the total spray application rate, respectively. No differences were observed in residue collections from high-volume air samplers (P>0.4), rotationg rod samplers (P>0.3), or vertical strings (P>0.7) at the four sampling stations. The collection from a high volume-PUF air sampler was 1108 ng/cu. m, with 728 ng/cu. m from the filter and 380 ng/cu. m from the PUF. Malathion residues were not detected in the RDI under the selected test conditions. A low airflow rate of 1.2 L/min combined with the short duration of exposure to the moving spray cloud provided little opportunity for the RDI to collect a detectable level of malathion.