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Atrazine, ametryn, bromacil, simazine and norflurazon were the most frequently detected pesticides in surface water samples and DDE, DDD and ametryn were the most frequently detected pesticides in sediment samples collected over the period November 1991 to June 1995 in a monitoring network that includes 27 stations in south Florida canals. The 744 pesticide detections during this time period represent about 2% of the total number of analytical determinations. Many of the most frequently detected compounds were used in large amounts in the monitoring area based on pesticide usage estimates included in this study. Spatial trends in pesticide detections followed use patterns. The maximum atrazine detections occurred in winter to late spring and were associated with usage on turfgrass and agricultural products. Endosulfan residues above the Florida water quality criterion were occasionally observed in surface water in the Homestead area and most of the exceedences occurred in confined waters. Methods with lower MDLs have recently been developed and should increase the number of detections in future sampling. Pesticides which bind strongly to soil, pesticides that are highly persistent and those used in large amounts were some of the more frequently found pesticides in sediments.

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Extraction of the herbicide glyphosate [N-(phosphonomethyl)glycine] from clay minerals and two soils was studied by a batch equilibrium technique. Experiments showed that, for most of the sorbent/solvent systems studied, the amount of herbicide extracted increased as pH increased, suggesting that sorption occurs through ion exchange and hydrogen bonding. Alkaline solutions of kaolinite, iron oxide, and two Calvin silt loam soil samples showed resorption of glyphosate after an initial desorption step. Determination of glyphosate residues in soils was performed by derivatization of soil extracts with 9-fluorenylmethyl chloroformate and analysis by HPLC with fluorometric detection. Glyphosate was successfully recovered from sandy soils at 0.5 ppm by triplicate extraction with 0.