An Investigation Into The Distribution And Chemical Species Of Heavy Metals In Fish And Vegetables

More and more attention has been paid to the heavy metal pollution of food in recent years. However, the researches have been mostly restricted in the determination of the total quantities of heavy metals in food samples. There has been little research about the important chemical species of the heavy metals in food samples. Therefore, in the present study, the absorption and accumulation of heavy metals in fish and vegetables exposed to heavy metals respectively are measured by inductively coupled plasma mass spectrometry (ICP-MS).In addition, the multimetal-binding fractions in the samples are investigated with the hyphenated technique of size-exclusion chromatography (SEC) and ICP-MS. The results may be useful for the further studies about reacting mechanisms of heavy metals of the aquatic products and plants in contaminative environment.The full thesis consists of three chapters: 1. review of heavy metal contamination and food safety; 2. investigation into metal distribution, accumulation and metal-binding metallothioneins in carp exposed in waterborne heavy metals; 3. investigation of cadmium distribution and Cd-binding fractions in mustard cultured in cadmium solution.In the first chapter, the danger and the present situation of heavy metal contamination in foods were reviewed. The discussion mainly focused on the analytical methods of atomic spectrometry generally used in the present for trace heavy metals in foods, and the hyphenated techniques of high performance liquid chromatogram (HPLC) and inductively coupled plasma mass spectrometry (ICP-MS) used for the speciation analysis of heavy metals.In the second chapter, the bioaccumulation of metals and induction of metallothioneins in carp co-exposed to cadmium, mercury and lead were investigated. The results indicated that the accumulation order of three heavy metals was as follows: gills>kidneys> livers>muscle; the amount of MTs induced in fish tissues increased with the longer exposure time. Gill would significantly assimilate heavy metals and the assimilated metals in the gill caused higher MTs concentrations in this organ, therefore, MTs in gill could be used as a marker to reflect the toxic metal pollutionIn the third chapter, the absorption and accumulation of cadmium in mustard stressed with different species and different concentrations of cadmium were investigated. Meanwhile, the cadmium-binding fractions in mustard were analyzed with the hyphenated technique mentioned above. The results indicated that the accumulation order of Cd was ranged as roots>leaves>stems. The main (Cd,Zn)-binding fractions included high molecular mass (HMM), MT-like and phytochelatins (PCs). Comparing with the content of PCs and MT-like, the amount of HMM induced in roots of mustard increased significantly with the higher stressed Cd concentrations.