Herbicides from Cropped Watersheds in Stream and Estuarine Sediments in Hawaii
1977
Green, R. E. | Goswami, K. P. | Mukhtar, M. | Young, H. Y.
Analysis of sediments and soils associated with two estuaries on Oahu was conducted to determine if herbicides used in plantation crops reach coastal waters. Analytical procedures were developed for simultaneous extraction of atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine), ametryn (2-(ethylamino)-4-(isopropylamino)-6-(methylthio)-s-triazine), diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), and DCA (3,4-dichloroaniline). Field soil and runoff samples from two small monitored watersheds provided additional information on the dissipation of diuron in sugarcane (Saccharum officinarum) and pineapple (Ananas comosus) fields, and on diuron removal in runoff waters. Atrazine and ametryn dissipated rapidly in field soils, and neither was found normally in stream and estuarine sediments. Diuron, on the other hand, was sufficiently persistent in soils and sediments to be found in nearly all sediment samples obtained at 6-month intervals at several sites for each estuary and its associated streams. Diuron in sediments was generally < 500 ppb (oven-dry basis), but occasionally much higher concentrations were encountered at sites which were subject to localized contamination from spray equipment loading areas. Diuron appears to be transported in runoff waters principally in the solution phase rather than adsorbed on suspended solids. Estuarine waters (West Loch) contained 0.1 to 1 ppb diuron, while concentrations in runoff waters were several times higher. It is not known if these chronic low levels adversely affect the ecological balance of the estuary.
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