title: Monitoring Herbicide Concentrations and Loads during a Flood Event: A Comparison of Grab Sampling with Passive Sampling.
abstract: The suitability of passive samplers (Chemcatcher) as an alternative to grab sampling in estimating time-weighted average (TWA) concentrations and total loads of herbicides was assessed. Grab sampling complemented deployments of passive samplers in a tropical waterway in Queensland, Australia, before, during and after a flood event. Good agreement was observed between the two sampling modes in estimating TWA concentrations that was independent of herbicide concentrations ranging over 2 orders of magnitude. In a flood-specific deployment, passive sampler TWA concentrations underestimated mean grab sampler (n = 258) derived concentrations of atrazine, diuron, ametryn, and metolachlor by an average factor of 1.29. No clear trends were evident in the ratios of load estimates from passive samplers relative to grab samples that ranged between 0.3 and 1.8 for these analytes because of the limitations of using TWA concentrations to derive flow-weighted loads. Stratification of deployments by flow however generally resulted in noticeable improvements in passive sampler load estimates. By considering the magnitude of the uncertainty (interquartile range and the root-mean-squared error) of load estimates a modeling exercise showed that passive samplers were a viable alternative to grab sampling since between 3 and 17 grab samples were needed before grab sampling results had less uncertainty.
authors.affiliation: Queensland Alliance for Environmental Health Sciences, The University of Queensland , 39 Kessels Road, Coopers Plains, Queensland 4108, Australia.
authors.forename: Andrew Joseph
authors.identifier: 0000-0001-5835-4483
authors.initials: AJ
authors.lastname: Novic
authors.affiliation: Catchment to Reef Research Group, TropWATER, ATSIP, DB145, James Cook University , Townsville, Queensland 4811, Australia.
authors.forename: Dominique S
authors.initials: DS
authors.lastname: O'Brien
authors.affiliation: Queensland Alliance for Environmental Health Sciences, The University of Queensland , 39 Kessels Road, Coopers Plains, Queensland 4108, Australia.
authors.forename: Sarit L
authors.initials: SL
authors.lastname: Kaserzon
authors.affiliation: Griffith School of Environment, Griffith University , 170 Kessels Road, Nathan, Queensland 4111, Australia.
authors.forename: Darryl W
authors.initials: DW
authors.lastname: Hawker
authors.affiliation: Catchment to Reef Research Group, TropWATER, ATSIP, DB145, James Cook University , Townsville, Queensland 4811, Australia.
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Lewis
authors.affiliation: Queensland Alliance for Environmental Health Sciences, The University of Queensland , 39 Kessels Road, Coopers Plains, Queensland 4108, Australia.
authors.forename: Jochen F
authors.initials: JF
authors.lastname: Mueller
mesh_terms: D004237:Diuron; D004784:Environmental Monitoring; D055868:Floods; D006540:Herbicides; D014874:Water Pollutants, Chemical
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D004237:Diuron