The significance of the retention of atmospherically deposited cadmium on plant surfaces to the cadmium content of herbage

Samples of mixed herbage were collected in 1993 and 1994 from the Park Grass Experiment at Rothamsted Experimental Station in the UK. The samples were separated into grasses and other species and the material in each group was then halved; one half was washed and the other was left unwashed. Analysis of Cd was by Zeeman correction GFAAS following a nitric acid digestion. The results showed that washing the samples prior to analysis made no difference to their Cd concentrations and that there was almost the same concentration of Cd in grasses and in other species. This implies that Cd remaining on leaf surfaces and changes in sward composition have not made a significant contribution to the previously reported underlying changes in herbage Cd over the last 130 years. Herbage Cd content has changed in response to either an underlying increase in soil Cd, increases in absorbed atmospherically derived Cd and/or changes in soil chemistry.