The Impact of Time-Integrating Active or Passive Sampling Methods on Bioanalytical Water Quality Risk Assessment

Abstract

Since traditional chemical analytical methods only consider a minor fraction of substances present in the water cycle, biological effect monitoring (BEM) is required for a more reliable assessment of the chemical status. BEM integrates the effects of all micropollutants that may trigger adverse outcome pathways. For reliable risk assessment it is important that substances are efficiently recovered from the water matrix by the environmental sampling and extraction methods. The present study compares the performance of five time-integrated sampling and extraction methods for large effluent volumes at three wastewater treatment plants (WWTPs). Both chemical and bioassay data are evaluated to select the best suited method for bioanalytical monitoring. Large volumes of WWTP effluents, collected for three weeks by flow-proportional active sampling, were extracted with XAD resins and large-volume solid-phase extraction (SPE). Simultaneously, three types of passive samplers (silicon rubber, POCIS and Speedisk) were deployed in the effluent channels. Clear differences were observed between both chemical and bioanalytical profiles for the five time-integrated sampling/extraction methods. Higher levels of extracted chemicals did not always lead to higher responses in the bioassays. If the total amount of extracted substances reflects the overall bioactivity, this may be since both agonistic and antagonistic compounds are extracted more efficiently. The best of the investigated active sampling methods seems to be SPE, that concentrated more compounds and at higher concentrations than XAD. The results obtained with passive samplers are highly dependent on estimations of average extracted water volumes, which are difficult to predict for complex environmental mixtures. POCIS seems to be the most efficient passive sampler for concentration of polar organic micropollutants. The preference between SPE and POCIS depends on the application. Since differences in sampling and extraction will affect the assessments of environmental risks, effect-based trigger values need to be adjusted for each method.