( ( ( The source ) ( of ( ( natural acid ) ( for ( rock weathering ) ) ) ) ) ( ( is ( dissolved ( ( carbon dioxide ) ( in water ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN source)) (PP (IN of) (NP (NP (JJ natural) (NN acid)) (PP (IN for) (NP (NN rock) (NN weathering)))))) (VP (VBZ is) (VP (VBN dissolved) (NP (NP (NN carbon) (NN dioxide)) (PP (IN in) (NP (NN water)))))) (. .)))
The source of natural acid for rock weathering is dissolved carbon dioxide in water.
(ROOT (S (NP (NNP Carbon) (NN dioxide)) (ADVP (RB chemically)) (VP (VBP weather) (NP (NNS rocks)) (PP (IN by) (S (VP (VBG creating) (NP (NNS acids)))))) (. .)))