Spatial, seasonal and vertical distributions of currently-used pesticides in the marine boundary layer of the North Sea

•23 pesticides were analysed in the marine boundary layer of the North Sea.•Simultaneously, these pesticides were quantified in the surface seawater.•Concentrations were seasonally highly variable.•Deposition of contaminated air from land contributes to seawater contamination.•Deposition was most significant for the distribution of pendimethalin and trifluralin.

Pesticides are transported beyond source regions and reach coastal waters and shelf seas. 23 representatives of six chemical classes of currently-used pesticides (CUPs) were simultaneously quantified in the marine boundary layer and the surface seawater of the German Bight and the central North Sea in 2009 and 2010.Terbuthylazine, metolachlor, metazachlor, pendimethalin and trifluralin exhibited the highest concentrations, seasonally highly variable. Advection of contaminated air from land and subsequent atmospheric deposition was shown to contribute to surface seawater contamination significantly, in particular in regions beyond riverine input and during the main seasons of application in agriculture. Deposition was most significant for the seasonal and spatial distributions of pendimethalin and trifluralin. Atrazine and simazine levels in the air are lower than 1-2 decades ago.