A Real-Time, Non-Invasive Technique for Visualizing the Effects of Acid Mine Drainage (AMD) on Soybean

Acid mine drainage is a serious environmental problem faced by the mining industry globally, causing the contamination of numerous agricultural lands and crops. Against this background, this study aims to investigate the effects of AMD on soybean, one of the major crops. To monitor the effects of AMD on soybean quickly and non-destructively, we have proposed a technique called biospeckle optical coherence tomography (bOCT). Soaked soybean seeds were monitored by bOCT, once after 6 h and again after germination, i.e., 48 h, and the results were compared with conventional parameters such as enzyme activity, iron uptake, and seedling length. It was found that bOCT could detect the effects due to the AMD after just 6 h with a decrease in a parameter called bisopeckle contrast that reflects the internal activity of the seeds. On the other hand, the conventional parameters required a week for the effects to appear, and the results from bOCT after six hours were consistent with those obtained by conventional measures. Because of the non-invasive nature of bOCT, requiring only tens of seconds of measurement with an intact, it has not only the potential to screen but could also constantly monitor long-term changes, thus possibly contributing to the study of the effects of AMD on crops.