A greenhouse experiment was conducted in Agrinion, Greece, using a randomized block design, including two variables i.e. treated municipal wastewater (TMWW), and well irrigation water (control), in six replications. The vegetable Brassica oleracea var. gemmifera (Brussels sprout) was used as a test plant The aim of the experiment was to assess quantitatively the elemental interactions' contribution in essential elements and heavy metals, to roots, leaves, sprouts, and whole plant, by studying the interactions between the macro-, micro-elements and heavy metals, depending on their synergism or antagonism. The mean net percent elemental contribution depended on: (i) the number of interactions between the essential elements and heavy metals, (ii) the extent of synergism or antagonism of each interaction, (iii) the relation between synergistic and antagonistic interactions. (iv) the size of the contribution of each interaction. (v) the plant part and kind of plant, and (vi) the external source of the supply of nutrients and heavy metals. The quantification procedure applied proved to be relatively easy and effective and can be used in assessing the extent of nutrients and especially of heavy metal accumulation in the various plant parts and especially in the edible ones (sprouts). (C) 2010 Elsevier B.V. All rights reserved.