Passive sampling of herbicides combined with effect analysis in algae using a novel high-throughput phytotoxicity assay (Maxi-Imaging-PAM)

We propose to combine a passive sampler for polar organic compounds ( POS) with a specific bioassay for phytotoxicity to assess the hazard of herbicidal compounds in surface waters. The POS consisted of an Empore (TM) disk coated with styrenedivinylbenzene deployed in a Teflon housing, which has relatively high sampling rates ( e. g., approximately 1 L d (-1) for diuron). POS were deployed for 5 days in a small- scale field study in South East Queensland, Australia, in a relatively pristine environment and an urban environment to explore sensitivity towards herbicides and potential influences of non- herbicidal pollutants. Besides chemical analysis of 8 herbicides, a novel bioassay ( Maxi- Imaging- PAM, IPAM) was employed to assess the phytotoxic effects of water samples and POS extracts. The IPAM allows rapid assessment of photosynthetic quantum yields of a large number of samples via chlorophyll-fluorescence imaging and the saturation pulse method. Sampling rates for several herbicides from laboratory calibrations were found to be applicable under field conditions. Toxic equivalent concentrations ( with reference to the herbicide diuron) were computed from the concentrations determined by chemical analysis and the relative potency ( also termed toxic equivalence factor) of the detected herbicides. There was good agreement between diuron equivalent concentrations from chemical analysis and diuron equivalent concentrations determined with the IPAM.