Spray drifts have been studied by mathematical models and computer simulations as an essential complement to lab and field tests, among which are fluid dynamic approaches that help to understand the transport of spray droplets in a turbulent atmosphere and their potential impacts to the environment. From earlier fluid mechanical models to highly computational models, scientific advancement has led to a more realistic prediction of spray drift, but the current literature lacks reviews showing the trends and limitations of the existing approaches. This paper is to review the literature on fluid-mechanical-based modelling of spray drift resulting from ground spray applications. Consequently, it provides comprehensive understanding of the transition and development of fluid dynamic approaches and the future directions in this research field.

Efficient collection of airborne spray is crucial to reduce environmental contamination and ensure effective pesticide application in agriculture. This study explored the efficacy of passive spray drift samplers, focusing on string collectors for capturing airborne spray droplets. String collectors were assessed in laboratory experiments using a spray drift tunnel. A notable average recovery rate of 82% was observed when string collectors were examined immediately after pesticide capture. Collection efficiency was found to increase with wind speed. Of all the string collectors, string #5, a yarn type, demonstrated consistent collection efficiency, meeting the criteria for passive samplers. This includes effective droplet capture at low wind speeds, a high recovery rate of 93.31%, and suitability for field experiments. Field evaluations further underlined the efficiency of string #5, showcasing its ability to capture spray drift across a wider area and varied heights with less effort and manpower compared to traditional nylon screens.

This study attempt to evaluate  aerodynamic property and collection efficiency of spray drift according to the leaf area index (LAI) of crop for  preventing undesirable pesticide contamination by the spray-drift tunnel experiment. The collection efficiency of the  plant with ‘Low’ LAI was measured at 16.13% at a wind speed of 1 m/s. As the wind speed increased to 2 m/s, the  collection efficiency of plant with the same LAI level increased 1.80 times higher to 29.06%. For the ‘Medium’ level  LAI, the collection efficiency was 24.42% and 43.06% at wind speed of 1 m/s and 2 m/s, respectively. For the  ‘High’ level LAI, it also increased 1.24 times higher as the wind speed increased. The measured results indicated that  the collection of spray droplets by leaves were increased with LAI and wind speed. This also implied that dense leaves  would have more advantages for preventing the drift of airborne spray droplets. Aerodynamic properties also tended  to increase as the LAI increased, and the regression analysis of quadric equation and power law equation showed high  explanatory of 0.96－0.99.