Field evaluation of spray drift and environmental impact using an agricultural unmanned aerial vehicle (UAV) sprayer

Guobin Wang; Yuxing Han; Xuan Li; John Andaloro; Pengchao Chen; W Clint Hoffmann; Xiaoqiang Han; Shengde Chen; Yubin Lan

doi:10.1016/j.scitotenv.2020.139793

Field evaluation of spray drift and environmental impact using an agricultural unmanned aerial vehicle (UAV) sprayer

Sci Total Environ. 2020 Oct 1:737:139793. doi: 10.1016/j.scitotenv.2020.139793. Epub 2020 May 29.

Authors

Guobin Wang¹, Yuxing Han², Xuan Li³, John Andaloro³, Pengchao Chen⁴, W Clint Hoffmann⁵, Xiaoqiang Han⁶, Shengde Chen⁴, Yubin Lan⁷

Affiliations

¹ Shandong Provincial Engineering Technology Research Center for Agricultural Aviation Intelligent Equipment, College of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo 255022, China.
² National Center for International Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology (NPAAC), College of Electronic Engineering, South China Agricultural University, Guangzhou 510642, China. Electronic address: yuxinghan@scau.edu.cn.
³ FMC Corporation, Stine Research Center, 1090 Elkton Road, Newark, DE 19711, USA.
⁴ National Center for International Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology (NPAAC), College of Electronic Engineering, South China Agricultural University, Guangzhou 510642, China.
⁵ Shandong Provincial Engineering Technology Research Center for Agricultural Aviation Intelligent Equipment, College of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo 255022, China; Prology Consulting, 3600 Eagle Nest, College Station, TX 77845, USA.
⁶ College of Agricultural, Shihezi University, Xinjiang, Shihezi 832000, China.
⁷ Shandong Provincial Engineering Technology Research Center for Agricultural Aviation Intelligent Equipment, College of Agricultural Engineering and Food Science, Shandong University of Technology, Zibo 255022, China; National Center for International Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology (NPAAC), College of Electronic Engineering, South China Agricultural University, Guangzhou 510642, China; Department of Biological and Agricultural Engineering, Texas A&M University, College Station, TX 77845, USA. Electronic address: ylan@sdut.edu.cn.

PMID: 32526578
DOI: 10.1016/j.scitotenv.2020.139793

Abstract

Unmanned Aerial Vehicle (UAV) applications at low-volume using fine and very fine size droplets have been adopted in several commercial spray scenarios allowing water-saving and high-efficiency operation in delivery of pesticides. However, spray drift associated with UAV applications, especially for fine droplets generated from spinning disk nozzles, has not been fully understood, raising environmental and regulatory concerns. The objectives of this study were to compare the drift potential of three different volume median diameter (VMD, or Dv_0.5) of 100, 150 and 200 μm from a commercial quadcopter equipped with centrifugal nozzles exposed to different wind speeds under field conditions. Prior to field test, the droplet size of the centrifugal nozzle was measured by a laser-diffraction particle-size analyzer. The results showed that the relationship between rotation speed and Dv_0.5 agrees with the negative power function. Field tests found that the deposition at 12 m downwind direction decreased by an order of magnitude compared with the average deposition within the in-swath zone. The deposition of almost all the treatments at 50 m downwind is lower than the detection limits of 0.0002 μL/cm². Based on the results from this study, the drift distance of this specific very popular UAV model is much less than that of manned aerial applicators. Based on the predicted equation (R² = 0.83), the detected drift amount increased with increasing wind speed and decreasing Dv_0.5. This work provides basic information to quantify the effect of wind speeds and droplet sizes on UAV spray drift potential which supports on-going regulatory guideline development for spray buffer zone and drift risk assessment protocols.

Keywords: Centrifugal nozzle; Droplet size; Environmental impact; Spray drift; Unmanned aerial vehicle; Wind speed.