Biospeckle Optical Coherence Tomography (bOCT) in the Speedy Assessment of the Responses of the Seeds of Raphanus sativus L. (Kaiware Daikon) to Acid Mine Drainage (AMD)

Danyang Li,Y Sanath K De Silva,Uma Maheswari Rajagopalan,Hirofumi Kadono,Fenwu Liu

doi:10.3390/app12010355

Abstract

The extraction of mineral resources from mines plays a vital role in global socio-economic development. However, acid mine drainage (AMD) has been one of the major pollutants, and a vast area of the agricultural fields has been polluted. Therefore, techniques for monitoring the response of plants to AMD that arise during mineral extraction are necessary. In addition, such a technique becomes especially valuable to understand how the plants could play a role in the phytoremediation of AMD. We propose the use of biospeckle Optical Coherence Tomography (bOCT) to investigate the response of Kaiware daikon seeds under the exposure to simulated AMD at two different concentrations of 40 mL/L and 80 mL/L. OCT images of the Kaiware daikon seed were obtained at a speed of 10 frames per second (1 frame: 512 × 2048 pixels) for a few tens of seconds. For each pixel of the OCT structural images, the contrast across the temporal axis was calculated to give biospeckle contrast OCT images (bOCT images). It was found that bOCT images clearly distinguished the changes due to 40 mL/L and 80 mL/L of AMD treatments from the control within a short time of around an hour, compared to the conventional OCT images that failed to show any changes. This variation was found to be statistically significant and could reflect the internal activity of the seeds. The proposed bOCT method could be a rapid, non-invasive technique for screening suitable plants in AMD phytoremediation applications.

Highlights

Mineral resources are an indispensable primary raw material for social and economic development
The Optical coherence tomography (OCT) images of the Kaiware daikon seeds exposed under different acid mine drainage (AMD) concentrations of the control, 40 mL/L, and 80 mL/L AMD after an exposure of 1 h to AMD are shown in Figure 2a–c with logarithmic intensity scale
Bright regions correspond to stronger OCT reflectivity signal, while dark regions correspond to reduced reflectivity

Summary

Introduction

Mineral resources are an indispensable primary raw material for social and economic development. When mining mineral resources such as coal and metals, a large amount of mine wastewater is generated due to the oxidation of sulfide minerals contained in the minerals [2]. Such mine wastewater has the characteristics of low pH (2–3), high level of Fe ions, and high SO42−, it is called acid mine drainage (AMD) [3]. AMD discharged into rivers will cause the pH of the water body to decrease rapidly, leading to the death of aquatic organisms and weakening the self-purification ability of the water body [4,5]. Due to the large output, the long-time span of formation, and the scattered production sources, the AMD problem has attracted widespread attention from mine environmental remediators worldwide

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