Quantifying Airborne Spray Drift Using String Collectors

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript examines the efficiency of passive spray drift samplers, specifically string collectors. The study uses cleverly designed parallel lab- and field-based studies to fill a key gap in the published literature on spray drift measurement. This study is very well written and provides important contributions to the field. Please see specific questions below.

Title: Excellent.

Abstract: Excellent.

Background: Excellent.

Methods: Great.

The criteria for passive samplers could be elaborated upon. What makes a good passive sampler? It would be helpful to see more details about what the authors considered with respect to cost and handiness methods.

Did the authors measure airborne droplet size in the field experiment? If not, why not? I would expect to find that certain combinations of temperature and humidity could greatly influence droplet size in field conditions. Perhaps I missed it, but were the environmental conditions (e.g., temperature and humidity) similar for both the lab and field experiments?

Results: Great. 

The authors state: "Based on our data, the largest drift droplet size is estimated to lie between 130 and 200 μm, contingent on the prevailing wind speeds." This is an interesting finding. Do the authors expect these estimates to be the same in the lab vs. field?

The finding that collection efficiency increases with wind speed is important. Can the authors provide more depth on this correlation? At what wind speed do the benefits plateau?

Discussion: Great.

The collection efficiency results for the various sampling matrices are intriguing and consistent with other published studies. While the authors provide a nice comparison of why this might be true, a more detailed discussion about the aerosol physics operating in these scenarios would be helpful. For instance, how did interception and/or inertial impaction fractions play a role in the performance of each sampling matrix? Was there a role for diffusion? Did the deposition fraction play a negligible role in capturing airborne spray drift?

It would be great to see some discussion about how the tested sampling matrices compare to biological surfaces as receptors. For example, how similar or different are they compared to plant and human surfaces? This could inform extrapolations in future studies related to the potential health impacts of pesticide drift.

Author Response

Thank you for reviewing our manuscript and providing constructive comments and questions. We have revised the paper in response to your feedback. Please see the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Please see the atachments.

Comments for author File: Comments.pdf

Author Response

Thank you for reviewing our manuscript and providing constructive comments and questions. We have revised the paper in response to your feedback. Please see the attached file.

Author Response File: Author Response.pdf