Online, Continuous, and Interference-Free Monitoring of Trace Heavy Metals in Water Using Plasma Spectroscopy Driven by Actively Modulated Pulsed Power.

This work presents the development of an online continuous heavy metals monitoring system using optical emission spectroscopy of plasma in water. The plasmas were driven by actively modulated pulsed power (AMPP) to control the plasma and its emission behavior in solutions with a wide range of conductivity. The AMPP quantified in situ the solutions' conductivity and modulated in real time the pulse width based on the conductivity. We demonstrated the online monitoring of the metallic elements. The results show that multiple metallic elements, namely Pb and Zn, can be independently and simultaneously detected with less than a 10% variation in the corresponding optical emission lines in solutions with a wide range of conductivity. An alert system was integrated to demonstrate the capability of an instant warning via e-mail once metallic elements were detected. Finally, we demonstrated that this system was robust even with the existence of several interferences and able to perform online continuous monitoring for days. We believe the system using plasma spectroscopy with AMPP for online monitoring of metals in water will have a significant impact on the fields of environmental monitoring and protection.