Several publications have attempted to analyze the factors influencing the results of column experiments or to assess the uncertainty of the determined parameters (Banzhaf and Hebig, 2016; Hebig et al., 2014; Kurwadkar et al., 2014; Ritschel and Totsche, 2016; Vitale et al., 2018). However, the sources and shares of uncertainty arising at various stages of column experiments have not yet been clearly identified, and their impact on the obtained values of the transport parameters is not recognized.
One of the most effective methods of estimating the uncertainty of experiments, allowing to increase the credibility of the results obtained during them, is to identify the main sources of uncertainty for individual stages of the research and to estimate their share in the total uncertainty budget (da Silva and Williams, 2015; Ellison and Williams, 2007; Magnusson et al., 2017).
Before starting the planning of column experiments, the main factors influencing the uncertainty of the obtained results were identified (Table 2) to take them into account in the experiments and minimize their influence on the results of the research.
Table 1. The main factors influencing the uncertainty of the results of column experiments
| Influencing factors to the uncertainty of the result | How the factor is included in the experiment |
| Preparation of the test stand | |
| Material from which individual elements of the station are made | Reactivity assessment — experiments with deionized water and deionized water with the addition of the test substance |
| Preparation of soil samples | Ensuring homogeneity — uniform procedure for the preparation of test samples, comparative homogeneity tests |
| Laboratory experiments | |
| Analytical methods | Estimate method uncertainty in the laboratory using standard procedures |
| Injection solution | Ensuring the homogeneity and stability of the chemical composition — a uniform methodology for the preparation of solutions, stability tests |
| Tracer injection method | Pulse and continuous injection |
| Repeatability and reproducibility of experiments | Repeated/parallel experiments |
| Storage and transport of samples for the laboratory | Short storage time of samples in the refrigerator, analysis of samples as soon as possible from the experiment |
There are more of these factors in practice, but estimating the impact of each of them on the results of experiments would require a significant extension of the scope of research, and thus, financial outlays and time to conduct experiments. Hence, it was decided to include in the planning of experiments those most important in the opinion of the authors.
Referencers
Banzhaf, S., Hebig, K.H., 2016. Use of column experiments to investigate the fate of organic micropollutants – A review. Hydrology and Earth System Sciences 20, 3719–3737. https://doi.org/10.5194/hess-20-3719-2016
da Silva, R.B., Williams, A., 2015. Eurachem/CITAC guide: Setting and using target uncertainty in chemical measurement.
Ellison, S.L.R., Williams, A., 2007. EURACHEM/CITAC Guide: Use of uncertainty information in compliance assessment. \.
Hebig, K.H., Nödler, K., Licha, T., Scheytt, T.J., 2014. Impact of materials used in lab and field experiments on the recovery of organic micropollutants. Science of the Total Environment 473, 125–131. https://doi.org/10.1016/j.scitotenv.2013.12.004
Kurwadkar, S., Wheat, R., McGahan, D.G., Mitchell, F., 2014. Evaluation of leaching potential of three systemic neonicotinoid insecticides in vineyard soil. Journal of Contaminant Hydrology 170, 86–94. https://doi.org/10.1016/j.jconhyd.2014.09.009
Magnusson, B., Näykki, T., Hovind, H., Krysell, M., Sahlin, E., 2017. Handbook for calculation of measurement uncertainty in environmental laboratories (NT TR 537 edition 4).
Ritschel, T., Totsche, K.U., 2016. Closed-flow column experiments—Insights into solute transport provided by a damped oscillating breakthrough behavior. Water Resources Research 52, 2206–2221. https://doi.org/10.1111/j.1752-1688.1969.tb04897.x
Vitale, C.M., Terzaghi, E., Zati, D., Di Guardo, A., 2018. How good are the predictions of mobility of aged polychlorinated biphenyls (PCBs) in soil? Insights from a soil column experiment. Science of the Total Environment 645, 865–875. https://doi.org/10.1016/j.scitotenv.2018.07.216