( ( ( Pollutant ( Primary Sources ) ) ( in ( the ( Air 1 ) ) ) ) . )
(ROOT (S (VP (VB Pollutant) (NP (JJ Primary) (NNS Sources)) (PP (IN in) (NP (DT the) (NNP Air) (CD 1)))) (. .)))
Pollutant Primary Sources in the Air 1.
(ROOT (S (NP (JJ Primary) (NNS pollutants)) (VP (VBP enter) (NP (DT the) (NN air)) (ADVP (RB directly))) (. .)))