Airborne spray drift measurement using passive collectors and lidar systems

Minimization of the risk associated with spray applications requires a proper understanding of the spray drift phenomenon. This fact has led to the development of several techniques to measure the deposition on horizontal surfaces as well as the airborne spray profiles. Assessment of airborne spray drift is particularly difficult because this phenomenon is subject to variable micrometeorological conditions. However the monitoring of airborne drift has a great importance since it can be carried over long distances. This paper reviews main sampling techniques currently used to asses the airborne spray drift, based on passive collectors and tracers. Theoretical principles that determine the efficiency of passive samplers are studied as well as the performance of different types of tracers. On the other hand, this paper shows new airborne spray drift assessment techniques based on lidar technology, reviewing its principle of operation as well as its practical application in several spray drift trials. It is concluded that the lidar technique has significant advantages over conventional methods, especially in terms of time consumption and monitoring capabilities. However, the future adoption of lidar technology for airborne spray drift studies will be subjected to the development of lidar instruments really adapted to this application.The authors wish to acknowledge the MICINN (Spanish Ministry of Science and Innovation) and FEDER funds under the projects AGL2010-22304-C04-03 and TEC2009-0910