Application of Laser-Induced Breakdown Spectroscopy in Detection of Cadmium Content in Rice Stems.

Wei Wang,Tingting Shen,Fei Liu,Wenjing Zhu,Wenwen Kong,Yong He,Zun Man,Yufei Liu

doi:10.3389/fpls.2020.599616

Abstract

The presence of cadmium in rice stems is a limiting factor that restricts its function as biomass. In order to prevent potential risks of heavy metals in rice straws, this study introduced a fast detection method of cadmium in rice stems based on laser induced breakdown spectroscopy (LIBS) and chemometrics. The wavelet transform (WT), area normalization and median absolute deviation (MAD) were used to preprocess raw spectra to improve spectral stability. Principal component analysis (PCA) was used for cluster analysis. The classification models were established to distinguish cadmium stress degree of stems, of which extreme learning machine (ELM) had the best effect, with 91.11% of calibration accuracy and 93.33% of prediction accuracy. In addition, multivariate models were established for quantitative detection of cadmium. It can be found that ELM model had the best prediction effects with prediction correlation coefficient of 0.995. The results show that LIBS provides an effective method for detection of cadmium in rice stems. The combination of LIBS technology and chemometrics can quickly detect the presence of cadmium in rice stems, and accurately realize qualitative and quantitative analysis of cadmium, which could be of great significance to promote the development of new energy industry.

Highlights

Rice straw is an important secondary product of rice (Sepaskhah and Yousofi-Falakdehi, 2009; Zaima et al, 2010)
The representative laser induced breakdown spectroscopy (LIBS) spectra of rice stems under different cadmium stress are illustrated in Figure 4, where (A) is the average raw spectra and (B) is the average spectra after different spectral line characteristics, it is not a straightforward process to complete accurate and rapid sample classification based on the spectral peak position or peak intensity of the elements
In the spectral range of 210.01∼231.00 nm, three cadmium emission lines can be clearly observed with reference to the atomic spectra database of National Institute of Standards and Technology (NIST), namely ionic spectral lines Cd II 214.44 and Cd II 226.50 nm, and atomic spectral lines Cd I 228.80 nm

Summary

Introduction

Rice straw is an important secondary product of rice (Sepaskhah and Yousofi-Falakdehi, 2009; Zaima et al, 2010). Straw has the advantages of abundant raw materials, low price, high combustion calorific value (about 50% of standard coal) (Jenkins et al, 1998; Lim et al, 2012; Yin et al, 2013). It is rich in nutrients such as mineral elements (N, P, K, Ca, Mg, and Si), plant fiber (cellulose, hemicellulose, and lignin) and protein, which can be used as fuel, feed, fertilizer, base material and industrial raw materials (Buzarovska et al, 2008; Abraham et al, 2016; Ostos-Garrido et al, 2019; Logeswaran et al, 2020). Most of the cadmium absorbed by rice roots is concentrated in the stem, which is an important factor causing heavy metal pollution of straw biomass resources. Rapid detection of cadmium in rice straw is of great significance to promote the development of straw industry and new energy industry

Objectives

Methods

Results

Conclusion