( ( Coal-fired ( electric ( generating plants ) ) ) ( ( are ( ( the ( greatest sources ) ) ( of ( atmospheric mercury ) ) ) ) ; ) )
(ROOT (S (NP (JJ Coal-fired) (JJ electric) (NN generating) (NNS plants)) (VP (VBP are) (NP (NP (DT the) (JJS greatest) (NNS sources)) (PP (IN of) (NP (JJ atmospheric) (NN mercury))))) (: ;)))
Coal-fired electric generating plants are the greatest sources of atmospheric mercury;
(ROOT (S (NP (NNP Coal)) (VP (VBZ is) (NP (NP (DT the) (NN source)) (PP (IN of) (NP (JJS most) (NN electricity))))) (. .)))