Optical parameters extraction of soil and its microplastics contamination using terahertz spectroscopy

Area of Science:

• Environmental Science
• Analytical Chemistry
• Spectroscopy

Background:

• Microplastic contamination poses a significant environmental challenge.
• Current detection methods can be time-consuming and destructive.
• Need for rapid, non-destructive analytical techniques for microplastics in complex matrices like soil.

Purpose of the Study:

• To investigate the potential of continuous-wave terahertz frequency-domain spectroscopy (CW-THz-FDS) for detecting microplastic contamination in soil.
• To evaluate the sensitivity and non-destructive nature of THz-FDS for microplastic analysis.
• To determine the feasibility of using THz-FDS for environmental monitoring of microplastics.

Main Methods:

• Prepared soil mixtures with varying concentrations of low-density polyethylene (LDPE) microplastics (1-15% by weight).
• Utilized a CW-THz-FDS system (0.1-0.7 THz) to measure optical properties (transmission, attenuation, refractive index) of soil-LDPE mixtures.
• Analyzed the concentration-dependent variations in optical properties and identified polylactic acid (PLA) as a suitable sample holder material.

Main Results:

• Observed distinct, concentration-dependent variations in the optical properties of soil-LDPE mixtures.
• Refractive index at 15% LDPE ranged from 2.2 to 2.3.
• Attenuation coefficient varied between 10 and 14 cm⁻¹, showing sensitivity to microplastic content.

Conclusions:

• CW-THz-FDS is a promising non-destructive technique for detecting microplastic contamination in soil.
• The method offers a rapid and sensitive approach for environmental monitoring.
• THz spectroscopy provides a viable alternative to conventional microplastic analysis techniques.