| Terahertz time domain spectroscopy was used to collect time domain data of solutions. After denoising and time domain analysis, linear models were established for mercury, cadmium and copper ion solutions at frequencies of 1.7 THz, 0.7 THz and 1.2 THz respectively, and the determination coefficients with the best fitting effect were 0.969, 0.896 and 0.932, respectively. The method detection limit were from 0001mg/L to 0.002 mg/L, the RSD of 6 measurements of spiked blank samples was 2.0%, and the recoveries were from 940% to 102%. Applying this method in monitoring practical water samples from two inlets of a sewage treatment plant， mercury ion was not detected. |
