Pesticides in sediments from Queensland irrigation channels and drains

Pesticide concentration in sediment from irrigation areas can provide infor mation required to assess exposure and fate of these chemicals in freshwate r ecosystems and their Likely impacts to the marine environment. In this st udy, 103 sediment samples collected from irrigation channels and drains in 11 agricultural areas of Queensland were analysed for a series of past and presently used pesticides including various organochlorines, synthetic pyre throids, benzoyl ureas, triazines and organophosphates. The most often dete cted compounds were endosulphans (alpha, beta and/or endosulphan sulphate) which were detectable in 78 of the 103 samples and levels ranged from below the limit of quantification (0.1 ng g(-1) dw) up to 840 ng g(-1) dw. DDT a nd its metabolites were the second most often detected pesticide investigat ed (74 of the 103 samples) with concentrations up to 240 ng g(-1) dw of Sig ma DDTs. Mean Sigma endosulphan and Sigma DDT concentrations mere 1-2 order s of magnitude higher in sediments from the irrigation areas which are domi nated by cotton cultivation compared to those which are dominated by sugarc ane cultivation. In contrast to these insecticides, the herbicides diuron, atrazine and ametryn were the compounds which were most often detected in s ediments from irrigation drains in sugarcane areas with maximum concentrati ons in areas of 120, 70 and 130 ng g(-1) dw, respectively. In particular du ring flood events, when light is limiting, transport of these photosynthesi s inhibiting herbicides from the sugarcane cultivation areas to the marine environment may result in additional stress of marine plants. (C) 2000 Else vier Science Ltd, All rights reserved.