Identification of selected organic contaminants in streams associated with agricultural activities and comparison between autosampling and silicone rubber passive sampling.

This study evaluates the potential of silicone rubber passive sampling devices (SR-PSDs) as a suitable alternative to automatic water samplers (autosamplers) for the preliminary identification of a wide range of organic contaminants in freshwater systems. The field performance of SR-PSDs deployed at three sites on two streams of an agricultural catchment area in North East (NE) Scotland, United Kingdom (UK) was assessed concurrently with composite water samples collected from two of the sites using autosamplers. The analytical suite consisted of selected plant protection products (PPPs; commonly referred to collectively as 'pesticides'), including 47 pesticides and a separate sub-category of 22 acid/urea herbicides. Of these, a total of 54 substances, comprising 46 pesticides and 8 urea herbicides were detected in at least one of the SR samplers. All but 6 of these SR-PSD detected substances were quantifiable. By comparison, a total of 25 substances comprising 3 pesticides and 22 acid/urea herbicides were detected in the composite water samples, of which only 8 acid/urea herbicides were quantifiable. The larger number and chemical classes of compounds detected and quantified via passive sampling reflect the lower limits of detection achieved by this device when compared to autosamplers. The determination of dissolved concentrations of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) added to the information on contaminant pressures at each site, allowing assessment of the reliability of SR-PSDs in freshwater systems and the identification of possible contaminant sources. The study demonstrated the utility of SR-PSDs for detecting and semi-quantifying low concentrations of analytes, including those which hitherto have not been measured in the catchment area and also some pesticides that are no longer approved for agricultural use in the UK and EU. The SR-PSD approach can thus provide a better understanding and clearer picture of the use and presence of organic contaminants within catchments.