Exploring Electromagnetic Behavior Of Harmful Algae By Dielectric Spectroscopy

As human industrial activities become more frequent,resulting in the frequency of blooms,the scale and impact of blooms is becoming more and more serious.There are many reasons for harmful algae blooms that including the effects of water eutrophication,hydrology and meteorological factors.Algae can also produce harmful substances such as toxins and thus cause harm to human health and the marine ecological environment.The monitoring of algae in the water environment is a great significance for protecting human health and the ecological environment.At present,the traditional algae monitoring technology has high accuracy,but the sample preparation of most methods is cumbersome and complicated.Some require professional laboratory personnel to handle it.Some measurement methods are not capable of real-time monitoring,which is also the limitation of traditional methods.Dielectric spectroscopy can quickly and accurately obtain the internal information of the substance by measuring the dielectric properties of the sample,so as to achieve non-destructive and rapid measurement of the sample.Therefore,this method is also increasingly favored by researchers.In this paper,an open-ended coaxial probe based on dielectric spectroscopy is designed.Dielectric spectroscopy was used to analyze the change of dielectric constant during the growth of algae.The testing theory of the probe is based on the quasi-static model,through which the S-parameter obtained from the Vector Network Analysis is more accurately related to the dielectric constant of the material.The calibration principle of the probe is based on two parts:instrument calibration and numerical value calibration.Through calibration,the probe can get more accurate dielectric spectrum information of the substance.In the experiment,the probe was used to measure the dielectric constant of algae under different nutrition,temperature and solvent.The measured dielectric constant and temperature of algae show a trend of decreasing the imaginary part of dielectric constant and increasing the real part of dielectric constant with the increase of temperature.The relationship between the measured dielectric constant of algae and the solubility of algae,the results show that r~2 in the imaginary part of the dielectric constant of freshwater algae can reach 0.9999,0.9994,0.9997,and r~2in the imaginary part of the dielectric constant of seawater algae can reach 0.9979,0.9978,0.9969.Under the condition of N:P=27:1,r~2of the imaginary part of the dielectric constant of algae can reach 0.9682,0.9847,0.9690and 0.9699.The change of the real part of the dielectric constant of the sea algae S8with the temperature can reach 0.9834,0.9820,0.9793,0.9821,and the imaginary part of dielectric constant can reach 0.8051,0.7782,0.7526,0.7245.At the same time,we conclude that it is more accurate to get the dielectric spectrum information of the substance when the algae is dissolved in the solution with lower polarity.The dielectric spectrum information of marine algae measured by this probe is better than that of freshwater algae.This paper provides a reference for exploring the change of dielectric constant of algae by means of dielectric spectroscopy.