The overall goal of these protocols is to quantify transferable pesticide residues from tree to turfgrass vegetation. These approaches can help answer key questions regarding public safety from pesticides as well as regulatory decisions and in-user practices in the agro-chemical field. The protocols have unique attributes that make them variably appropriate across turfgrass systems.
And researchers should understand this prior to experimentation to most accurately predict human pesticide exposure. Transferable pesticide residue protocol selection should encompass the exposure route and turfgrass systems of interest to best quantify potential human exposure. By doing so, informed decisions based on sound research can be made on pesticide use in turfgrass systems.
For these protocols, field plots should include half meter to one meter alleys along their plot border to allow for foot traffic and sample collection. To collect residue samples from plants using hand wipes, first standardize the area being wiped using a test surface. Prepare a 10%green food coloring solution, and a 1%non-ionic surfactant solution.
Then spray the solution onto a non-porous surface. Now, with cotton gloves, press fingers on the non-porous surface. Then take a digital photograph and use an imaging program to calculate the area contacted based on the absence of green food coloring in that area.
Based on the area of hand-to-surface contact, calculate the amount of pressure needed to wipe the same area using two kilopascals. Then calibrate the wiping pressure using a digital scale. Secure turfgrass to the scale, and press with the required force, which is typically between 150 and 300 grams.
Next, calibrate the wiping speed. Measure out 30 centimeters of turf, and adjust the wiping speed until it takes about one second to wipe the distance. Thus, the wiping technique is standardized.
Before collecting a sample, define the sampling area by marking its perimeter with turf paint. Now wipe the sampling area with a cotton glove worn over a nitrile glove. Wipe for 30 seconds, using back and forth motions, changing directions perpendicularly.
Now repeat the process over the same area with a second cotton glove. After completing the wipes, freeze the sampling glove within three hours. Then store the cotton gloves in a glass jar on ice or dry ice.
Two sampling gloves were deemed necessary from preliminary efforts to sample a 420 square centimeter area. If a larger area is to be sampled, additional gloves may be needed. This procedure requires three people.
A roller is 10 centimeters in diameter, 61 meters long, and weighs 14.5 kilograms. 1.2 centimeter thick polyurethane foam surrounds the roller. Before use, wrap the foam in plastic.
The roller is rolled with a frame measuring 62 centimeters wide and 91 centimeters long. Onto the frame, use clamps to secure a cotton sheet that is 70 by 99 centimeters and has a thread count of at least 200 threads per inch. Now, the cotton sheet is in contact with the turf sampling area.
The frame is then secured to the ground via metal nails. Then gently roll the roller over the cloth back and forth five times. Use a roll speed of 1.6 kilometers per hour.
After one person finishes rolling, two others remove the frame from the ground. While the sheet is secured to the frame, a third person should delicately remove any debris from the cotton. Then remove the sheet from the frame, and fold it up inwardly so the sample contact area touches itself.
Store the sheet on ice. This must be frozen within three hours. After collecting the sample, remove the plastic from the roller.
Then clean the sampling equipment with 50%ammonia in water, followed by rinsing with water. Let the tools dry before reusing them. This procedure can be performed solo, and requires a soccer ball roller frame, which is made from a PVC pipe.
To make the ball roller, inflate the soccer ball to 24 kilopascals, which is relatively flat. Then mount the ball to the roller by securing it with lag bolts on opposite sides. The ball should spin symmetrically, and not get dislodged by light pressure.
Once it is determined to be secure, wrap the ball with a five centimeter wide, 130 centimeter long sorbent strip. The wrapped area should be aligned with the roller handle. Secure the strip to the ball with pieces of adhesive tape that are about two and a half square centimeters.
To collect the sample, roll the ball over 3.7 meters of grass at a constant speed, being careful not to step on any unsampled sampling region. Depending on plot dimensions, multiple side-by-side rolls may be necessary. Preliminary research should determine an appropriate ball-roll distance to avoid exceeding the absorptive capacity of the strip.
After rolling the ball, remove the sorbent strip, and fold it inwards, so the sample side contacts itself. Then transfer it to a glass jar on ice and freeze it within three hours of collection. Harvest a turfgrass core for sampling quality control.
First define the area to core using a golf course cup cutter, and dig five to seven and a half centimeters into the soil. Then angle a long knife into the soil and remove the core from the ground. Try to prevent contact with sampled vegetation, even from the knife used to collect it.
Now carefully remove the bottom soil from the core sample using scissors. Then gently place the plug in the sample container, such that the blades of the grass are not making contact with the container. Canopy moisture droplets may contain pesticide residue that transports from vegetation into the soil if the core is jostled, especially in the morning.
And for this reason, researchers should take special precaution during sample collection and subsequent handling. turfgrass plots were treated with the broad leaf herbicide 2, 4-D at one kilogram of active ingredient per hectare. Three turfgrass species were treated, and from each species, the three described sampling methods were used.
Sampling was done at four time points after herbicide application, and compared with the applied herbicide mass. The first sampling time points were immediately after application and one hour after application. Sampling was then performed one day after the herbicide application, and finally, three days after the herbicide application.
It was found that the hand wiping dislodged the greatest proportion of the applied 2, 4-D. Conversely, sampling with the ball roll generally dislodged the least herbicide. Because canopy dynamics vary, the turfgrasses transferred different amounts of herbicide.
Specifically, with roller-based sampling methods, both of the coarser grass species dislodged less herbicide. This may be due in part to reduced sorbent material to grass contact, because of the grass blades laying over. After watching this video, you should have a good understanding of how to conduct various protocols for quantified transferrable pesticide residues in turfgrass systems.
