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

Abstract

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™ 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.