• Morton, Phoebe
• Doody, Donnacha G.
• Mcroberts, W. Colin
• Farrow, Luke G.
• Cassidy, Rachel
• Floyd, Stewart
• Jordan, Philip

Abstract

<p>Passive samplers (PS) have been proposed as an enhanced water quality monitoring solution in rivers, but their performance against high-frequency data over the longer term has not been widely explored. This study compared the performance of Chemcatcher® passive sampling (PS) devices with high-frequency sampling (HFS: 7-hourly to daily) in two dynamic rivers over 16 months. The evaluation was based on the acid herbicides MCPA (2-methyl-4-chlorophenoxyacetic acid), mecoprop-P, fluroxypyr and triclopyr. The impact of river discharge parameters on Chemcatcher® device performance was also explored. Mixed effects modelling showed that time-weighted mean concentration (TWMC) and flow-weighted mean concentration (FWMC) values obtained by the HFS approach were both significantly higher (p &lt; 0.001) than TWMC values determined from PS regardless of river or pesticide. Modelling also showed that TWMC_PS values were more similar to TWMC_HFS than FWMC_HFS values. However, further testing revealed that MCPA TWMC values from HFS and PS were not significantly different (p &gt; 0.05). There was little indication that river flow parameters altered PS performance—some minor effects were not significant or consistent. Despite this, the PS recovery of very low concentrations indicated that Chemcatcher® devices may be used to evaluate the presence/absence and magnitude of acid herbicides in hydrologically dynamic rivers in synoptic type surveys where space and time coverage is required. However, a period of calibration of the devices in each river would be necessary if they were intended to provide a quantitative review of pesticide concentration as compared with HFS approaches.</p>

Topics

• impedance spectroscopy