<http://webisa.webdatacommons.org/prov/253412582>	<http://www.w3.org/ns/prov#wasDerivedFrom>	<http://webisa.webdatacommons.org/339785650> .
<http://webisa.webdatacommons.org/339785650>	<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>	<http://www.w3.org/ns/prov#Entity> .
<http://webisa.webdatacommons.org/339785650>	<http://www.w3.org/ns/prov#wasQuotedFrom>	<usgs.gov> .
<http://webisa.webdatacommons.org/339785650>	<http://www.w3.org/ns/prov#value>	"Apparently, physico-chemical and other factors are separating herbicides and volatile organic compounds in the shallow unsaturated zone.The occurrence of herbicide active and inactive ingredients (chiefly volatile organic compounds) at four selected sites in Iowa representing drain tiles, observation wells, or lysimeters, was investigated." .