Determination Of Cadmium And Nitrogen Nutrient In Water By Absorption Spectrometry Based On Dielectric Barrier Discharge Micro-Excitation Light Source

In natural water pollution,heavy metal ions and nitrogen nutrients are two common types of pollutants.Cadmium is a typical heavy metal,and its exposure can cause diseases such as respiratory cancer,skin disease,and anemia.Excessive nitrogen nutrients can cause eutrophication of water bodies and methemoglobinemia in the body.Therefore,real-time detection of cadmium and nitrogen nutrients in water bodies is of great significance for protecting the ecological environment and human health.Dielectric barrier discharge(DBD)is a typical non-equilibrium high-voltage AC gas discharge,giving rise to stable and uniform microplasma by controlling the discharge voltage.It has the advantages of simple production,low cost,small size and low energy consumption,serving as an ideal energy supply source.Many researchers have applied dielectric barrier discharge to the miniaturization of spectroscopic instruments.In this thesis,DBD was used as the excitation light source of atomic absorption spectrometry(AAS),and the fluctuation of the light source was corrected by the dual-beam mode,achieving the detection of trace cadmium in environmental water samples.In the constructed DBD-AAS system,cadmium ions are reduced to cadmium vapor by potassium borohydride,and subsequently introduced into the AAS system by means of carrier gas.The DBD excitation light source emits a characteristic line of cadmium at 228.8 nm,which is absorbed by the sample vapor.Two charge coupled devices(CCD)are used to record the change in spectral intensity,and then the absorbance of cadmium is obtained.In the experiment,the spectral characteristics and structure of the DBD excitation light source,and the conditions for hydride generation were explored.The power of the DBD excitation light source is only 0.9 W.Under the optimal experimental conditions,the relative standard deviation of the present system for the determination of cadmium is 3.8%,the detection limit is 0.3 μg L-1,and the linear range is 1～20 μg L-1.The system was used for the determination of simulated natural water samples GBW08608,standard samples GBW(E)080039 and GNM-M05072,and satisfactory results were obtained.The constructed DBD-AAS system has the characteristics of low energy consumption,small size,and convenient production.It is expected to achive real-time detection of heavy metals in the field.At the same time,DBD can also be used as an excitation light source for molecular absorption,and the dual-beam mode is used to correct the fluctuation of the light source,achieving the detection of nitrogen nutrients in environmental water samples.The nitrate in the nitrogen nutrient is reduced to volatile NO online by titanium trichloride.The gas sample is introduced into the absorption cell by argon,and the characteristic emission line generated from DBD is absorbed by NO gas.In the experiment,the spectral characteristics and structure of the DBD excitation light source,and the conditions for vapor generation were investigated.Under the optimal experimental conditions,the detection limit of the present system for the determination of nitrate is 0.15 mg L-1,and the relative standard deviation is 4%.