Rapid Monitoring Of Meta-cresol Contamination In Beach Sand Using Microwave Based Dielectric Spectroscopy

Contaminants derive from the offshore chemicals and oil leakage accident may cause great harm to the marine creatures and human body.Sea beach is vulnerable to the oil and chemical spilled contaminants including PAHs,phenols,halogenated compounds etcetera.M-cresol is one of the most common contaminants which have a high carcinogenicity,teratogenicity and genotoxicity,even at low levels accumulation through direct or indirect skin contact can cause severe damage to human body especially to children.The content of chemical and oil pollutants is one of the major parameters to evaluate the marine aqueous and beach environment quality.Investigation and evaluation of beach contamination is the basis of the environmental contamination prevention and management work,also have a great significance to the grasp of beach environmental quality,pollution control of chemical/oil spill and the protection of human health.Proper monitoring methods can promote the spill remediation by providing early detection of sand contamination as well as to measure the contamination levels and their impact on marine ecosystem.Current detection methods can provide accurate analysis results but most of them have complex sample preparations,costly transportation labor,analysis procedures are complicated and they are generally time consuming.Measurement of the dielectric permittivity of a material is one technique that can be used in this application.The measurement material has an intrinsic dielectric property as its own material composition and structural characteristics.A microwave measurement based dielectric spectroscopy can fulfil the rapid monitoring request by characterizing the dielectric property of the sea beach sand sample.A microwave based,in-vitro,spectroscopic technique has been developed,which is rapid and non-destructive,to investigate the beach sand sample contamination.Dielectric spectroscopy was applied to analyze the polarization mechanisms under a specific frequency range to better understand the electromagnetic characteristics of beach sand samples.Beach sand samples with meta-cresol and water content concentrations of 0-20% were tested in a set of in-vitro experiments.The experiments were performed using a prototype probe with 16 mm in length,sample holder.The measuring frequency range was from 10 MHz to 1GHz.In the characterization method establishment process,two low loss materials(air and Teflon),and two typical frequency dependent polar material(ethanol and water)were selected to measure their relative complex permittivity.The real and imaginary part of relative complex permittivity values of these reference materials are almost close to the theoretical value and well fitted with the Debye model.The dielectric technique showed a linear relationship between their real part of relative complex permittivity and the m-cresol/water content at a frequency range from 10MHz-1.0GHz.The dependency of real part of relative complex permittivity on the pollutant concentration at a given frequency range,can be potentially exploited for measuring pollutants concentrations in beach sand samples.The detection limit of the technique is 10.0 mg/g(S/N = 3)weight/weight basis,the sensitivity is 14.6 mg/g for water and 80 mg/g for meta-cresol.The imaginary part of the relative complex permittivity of the contaminants under the interfacial polarization frequency range could be a potential indicator to identify the particular targeted pollutant in the beach sand sample.