Publication
Current-use pesticides in New Zealand streams: Comparing results from grab samples and three types of passive samplers
Publisher:
Elsevier BV
Date:
11-2019
DOI:
10.1016/J.ENVPOL.2019.112973
Abstract: New Zealand uses more than a ton of pesticides each year many of these are mobile, relatively persistent, and can make their way into waterways. While considerable effort goes into monitoring nutrients in agricultural streams and programs exist to monitor pesticides in groundwater, very little is known about pesticide detection frequencies, concentrations, or their potential impacts in New Zealand streams. We used the 'Polar Organic Chemical Integrative S ler' (POCIS) approach and grab water s ling to survey pesticide concentrations in 36 agricultural streams in Waikato, Canterbury, Otago and Southland during a period of stable stream flows in Austral summer 2017/18. We employed a new approach for calculating site-specific POCIS s ling rates. We also tested two novel passive s lers designed to reduce the effects of hydrodynamic conditions on s ling rates: the 'Organic-Diffusive Gradients in Thin Films' (o-DGT) aquatic passive s ler and microporous polyethylene tubes (MPTs) filled with Strata-X sorbent. Multiple pesticides were found at most sites two or more were detected at 78% of sites, three or more at 69% of sites, and four or more at 39% of sites. Chlorpyrifos concentrations were the highest, with a maximum concentration of 180 ng/L. Concentrations of the other pesticides were generally below 20 ng/L. Mean concentrations of in idual pesticides were not correlated with in-stream nutrient concentrations. The majority of pesticides were detected most frequently in POCIS, presumably due to its higher s ling rate and the relatively low concentrations of these pesticides. In contrast, chlorpyrifos was most frequently detected in grab s les. Chlorpyrifos concentrations at two sites were above the 21-day chronic 'No Observable Effect Concentration' (NOEC) values for fish and another two sites had concentrations greater than 50% of the NOEC. Otherwise, concentrations were well-below NOEC values, but close to the New Zealand Environmental Exposure Limits in several cases.