Journal Article

Advantages of Synthetic Noise and Machine Learning for Analyzing Radioecological Data Sets

Shuryak, Igor

2017

Overview

The ecological effects of accidental or malicious radioactive contamination are insufficiently understood because of the hazards and difficulties associated with conducting studies in radioactively-polluted areas. Data sets from severely contaminated locations can therefore be small. Moreover, many potentially important factors, such as soil concentrations of toxic chemicals, pH, and temperature, can be correlated with radiation levels and with each other. In such situations, commonly-used statistical techniques like generalized linear models (GLMs) may not be able to provide useful information about how radiation and/or these other variables affect the outcome (e.g. abundance of the studied organisms). Ensemble machine learning methods such as random forests offer powerful alternatives. We propose that analysis of small radioecological data sets by GLMs and/or machine learning can be made more informative by using the following techniques: (1) adding synthetic noise variables to provide benchmarks for distinguishing the performances of valuable predictors from irrelevant ones; (2) adding noise directly to the predictors and/or to the outcome to test the robustness of analysis results against random data fluctuations; (3) adding artificial effects to selected predictors to test the sensitivity of the analysis methods in detecting predictor effects; (4) running a selected machine learning method multiple times (with different random-number seeds) to test the robustness of the detected \"signal\"; (5) using several machine learning methods to test the \"signal's\" sensitivity to differences in analysis techniques. Here, we applied these approaches to simulated data, and to two published examples of small radioecological data sets: (I) counts of fungal taxa in samples of soil contaminated by the Chernobyl nuclear power plan accident (Ukraine), and (II) bacterial abundance in soil samples under a ruptured nuclear waste storage tank (USA). We show that the proposed techniques were advantageous compared with the methodology used in the original publications where the data sets were presented. Specifically, our approach identified a negative effect of radioactive contamination in data set I, and suggested that in data set II stable chromium could have been a stronger limiting factor for bacterial abundance than the radionuclides 137Cs and 99Tc. This new information, which was extracted from these data sets using the proposed techniques, can potentially enhance the design of radioactive waste bioremediation.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Abundance / Algorithms / Artificial intelligence / Bacteria / Bacteria - classification / Bacteria - radiation effects / Benchmarks / Biology and Life Sciences / Bioremediation / Cesium isotopes / Cesium radioisotopes / Chromium / Computer and Information Sciences / Computer simulation / Contamination / Data processing / Datasets / Ecological effects / Ecological monitoring / Ecology and Environmental Sciences / Engineering and Technology / Environmental aspects / Estimates / Fungi - classification / Fungi - radiation effects / Hazards / Learning algorithms / Machine Learning / Medicine and Health Sciences / Models, Theoretical / Noise / Nuclear accidents & safety / Nuclear energy / Nuclear power / Nuclear power plants / pH effects / Physical Sciences / Pollution / Radiation / Radiation measurement / Radiation Monitoring / Radioactive contamination / Radioactive Pollutants / Radioactive pollution / Radioactive waste storage / Radioactive wastes / Radioisotopes / Research and Analysis Methods / Researchers / Robustness / Sediment pollution / Seeds / Sensitivity / Sensitivity analysis / Soil chemistry / Soil contamination / Soil Microbiology / Soil microorganisms / Soil Pollutants, Radioactive / Soil pollution / Soil temperature / Soils / Statistical analysis / Statistical methods / Statistical models / Studies / Teaching methods / Ukraine / Variables / Waste storage