Seasonal Variations of Selected Herbicides and Related Metabolites in Water, Sediment, Seaweed and Clams in the Sacca di Goro Coastal Lagoon (Northern Adriatic)

Abstract

This study assesses the status of Sacca di Goro coastal lagoon (Northern Adriatic, Italy) with respect to watershed pollution. Because 80% of its watershed is devoted to agriculture applying plant protection products, selected herbicides and their metabolites were found in the water column, sediments (the upper 0-15 cm horizon), and clams (Tapes philippinarum) and macroalgae (Ulva rigida). Five seasonal sampling campaigns were performed from May 2004 to April 2005 and concentrations measured in five stations in the lagoon and six in the watershed. Relatively high concentrations of the s-triazine - terbuthylazine -, urea herbicides - diuron - and alachlor were detected through the year mainly at stations directly influenced by the Po di Volano inflow. The concentrations of products in use follow a clear seasonal pattern with spring peaks. This pattern is also visible in the sediments as well as in biota. Among metabolites, hydroxylated compounds prevailed, often with concentrations greater than those of the parent compounds. For the most part of the year, the concentrations in biota are close to method-based detection limits, with low potential risk for both natural biota and humans.