Dry deposition and interception of 4–22 μm diameter particles to a lettuce crop

A programme of field experiments on dry deposition has been undertaken which involved the release of particulate material of four narrow well-defined size distributions (mean ± standard deviation diameters: 4 ± 1, 10 ± 2, 18 ± 3 and 22 ± 3 μm). Dry deposition to lettuce plants and interstitial soil has been evaluated and the fraction of material intercepted by the lettuce plants has been determined. Deposition velocity (flux/atomspheric concentration) was found to increase with increasing particle diameter and the measured values were consistent with predictions for dry deposition to a rough surface. The fraction of material intercepted by the crop was typically between 0.8 and 0.9, although this appeared to be independent of particle size. It was found that the fraction of material intercepted by a leafy vegetable, such as lettuce, may be estimated from the fraction of the area that the plants occupy multiplied by a coefficient of interception which, for the current study, was around 1.2.