ABSTRACT
Institute of Environmental and Biological Sciences, Lancaster University, Lancaster, LA1 4YQ, U.K.
Atmospheric deposition can be a significant source of heavy metal input to soils and plants in agroecosystems of industrialized countries. This is mostly due to anthropogenic combustion activities, which have substantially, enhanced natural emissions of selected heavy metals to the atmosphere. Once emitted, the atmospheric transport of the metal depends upon its chemical properties. Volatile “metalloids” can be transported in a gaseous form or enriched on particles (e.g., Se, Hg, As, and Sb), whereas other metals are transported only in the particle phase (Cd, Pb, and Zn) and may travel long distances before deposition to land. It is argued that atmospheric deposition has resulted in the accumulation of some elements in the surface layers of agricultural soils. There is also evidence that elements adhere to surfaces of crops and, if in the gaseous form, may be absorbed via the foliage into the plant. For Pb, for example, it is shown that about 90% of the total plant uptake is due to deposition from the atmosphere rather than transport from the soil, implying that atmospheric deposition poses a significant source of metal inputs to the foodchain, particu larly where background soil levels are relatively low.
