Bias in grain size distribution of deposited atmospheric dust due to the collection of particles in sediment catchers

This study investigates how dust deposition samplers affect the grain size characteristics of the sediment they catch. Sediment samplers act as obstacles in the flow and their collection efficiency varies with the grain size and other factors. Some particle fractions are collected more efficiently than others, resulting in a modification of the original grain size distribution of the sediment. This paper presents wind tunnel results for five dust deposition samplers and five wind velocities ranging from 1 to 5 m s− 1. The catcher's effect on the grain size was apparent in all experiments. Dust accumulated in a catcher is finer than undisturbed dust. For the dust used in the tests the difference (in median grain diameter) was of the order of 10–20%, but differences up to 40% and more were observed. In general, the error is higher when the catcher is less aerodynamically shaped. The study concludes that grain size data on sediment collected by a catcher should be interpreted with care, as they do not necessarily reflect the characteristics of the original sediment.