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Whole-cell biosensors for determination of bioavailable pollutants in soils and sediments: Theory and practice

Research output: Contribution to journalArticlepeer-review

Xiaokai Zhang, Boling Li, Daniel N. Schillereff, Richard C. Chiverrell, Boris Tefsen, Mona Wells

Original languageEnglish
Article number152178
JournalScience of the Total Environment
Published10 Mar 2022

Bibliographical note

Funding Information: We thank the National Natural Science Foundation of China for support of this project via a competitive award (Grant No. 42107245 ). We are very grateful to Shimshon Belkin and Sharon Yagur-Kroll of the Hebrew University of Jerusalem for provision of and technical assistance with the bioreporter strain and to Malcolm Horsburgh from the University of Liverpool for hosting and supporting some of the experimental work in his laboratory. Publisher Copyright: © 2021 Elsevier B.V.

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The bioavailability of pollutants is a key factor affecting environmental risk. Whole-cell bioreporters are a demonstratedly effective tool for the investigation of pollutant bioavailability in water and soil/sediment. Unlike aqueous samples, transmittance of bioreporter optical signal is reduced in direct-contact assays with soil/sediment, which affects the accuracy of bioreporter-detected pollutant bioavailability. No studies have measured the magnitude and variability of soil/sediment effects on signal in direct-contact assays or how associated uncertainties influence results. In this study, we investigate the optical effects of soil/sediment particles in suspensions on bioreporter signal transmittance and quantify how variable these optical effects are from sample-to-sample. We find that neglecting bioreporter signal diminution by soil/sediment, as many studies do, can lead to order-of-magnitude errors in results, underestimating risk. Correction based on methods in ad hoc use (e.g. comparison to signal from non-inducible reporter or use of reference soil/sediment) are also problematic for some types of experiment, and could lead to errors in excess of 30%. Our findings have a sound basis in theory, and we provide recommendations concerning the most suitable type of approach to use for different experimental settings. Generally, if best accuracy is not needed to quantify bioavailability, for samples that have been ground, sieved, and are of reasonably uniform color, it may be possible to use a single or average correction factor, particularly for experiments performed at a single slurry concentration. For investigations studying bioavailability under varying solid-phase:water ratios (e.g., sorption/desorption), detailed compensation measurements are needed for independent variables, including each specific soil/sediment sample, slurry concentration, and in some cases bioreporter signal intensity. Our measurements and calculations indicate that best results are obtained when working in the region of ballistic photon transmittance. Findings herein will be useful in areas that require information on bioavailability, such as ecotoxicology and environmental risk assessment.

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