Drag sled

The other popular technique in use today is the drag-sled technique, which consists of attaching a cloth dosimeter onto the bottom of a square block of some material (such as aluminum) of a predetermined size which has a weight added to the top side. The weighted sled is then pulled one time over a prescribed area of treated turf. The cloth dosimeter is taken off the sled, extracted, and analyzed for residues. 

The drag sled snrface sampler (Fignre 3.5) is a simple device constructed of a 7.6-cm X 7.6-cm x 1.9-cm thick block of wood or other material, which is used to hold down a 10-cm x 10-cm piece of denim cloth sampling medium as it is dragged across the floor. The bottom of the block is covered with solveut-riused aluminum foil and the denim patch is placed over the foil. Staples or push-pins are typically used to secure the sampling medium to the block. A 3.6kg weight is centered on top of the block to provide a downward pressure of 4500 Pa. The... 

Increasing the contact pressure exerted by the drag sled on a treated nylon plush carpet had relatively little effect on the transfer of chlorpyrifos residues to the cloth sampling medium (36 13 p.g at 2100 Pa, to 56 28 p.g at 4500 Pa, and to 43 10p.g at 15 600 Pa). Increasing the traverse speed of the drag sled reduced the amount of chlorpyrifos transferred from 56 28 Rg at 7 cm/s to 31 21p.g at 20 cm/s. The amount of transfer increased relatively uniformly with traverse distances up to 10 m. Static (3 s) transfer of chlorpyrifos to the sled averaged 0.6 p,g, or about half of that transferred to the PUF roller. The mean amounts transferred to the drag sled cloth increased from 4.2 p.g over the first 17 cm traversed, to 8.6 p,g over 92 cm, 124 p,g over 3 m, and 302 p.g over 10 m. 

Property California roller Drag sled PUF roller Human hand press... 

Table 3.2 Comparison of transfer of fresh dried formulated pesticide residues from floor covering by drag sled, PUF roller and human hand presses...

Mean and standard deviation of transfer rates for single passes over floor covering surface using dry sampling media (contact areas of 930 cm for drag sled and 760 cm for PUF roller). 

Information relating to ease of nse, simplicity, time requirements and other criteria for each of the test methods was also obtained during the round-robin test by means of written subjective evaluations and critique by each volunteer. The drag sled and PUF roller methods were rated high in overall ease of use, while the California roller was rated low. 

Of the three techniques, the PUF roller most closely approximates the human hand press in the quantities of pesticide residues collected per unit area of surface sampled, although it collects several times as much as the dry palm of the hand. The pliable foam sampling material, especially when wetted, more closely resembles human skin than the cotton fabrics used by the drag sled and California roller. However, since the transfer rates for the latter two devices are much higher than that of the PUF roller, they are less prone to yield non-detectable results in the field. 

In the first test, conducted in July under hot and relatively dry conditions, the grass was cut to 5 cm and raked prior to application of the chlorpyrifos/ chlorothalonil mixture. Deposition rates were determined by strategic placement of 10-cm X 10-cm cotton gauze coupons backed with aluminum foil. The test plot was allowed to dry for 4 h before sampling. The mean transfer efficiencies for chlorpyrifos were 2.37 ng/m (0.087%) for the PUF roller and 1.05 ng/m (0.039%) for the drag sled. The transfer efficiencies were much higher for... 

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