| At present, the hygiene quality of tea which is payed close attention to by the circle of tea has become a focus. It concerns directly consumer's food security and market of tea. The problem of heavy metal pollution on tea has been cared. By means of field investigation, sampling and analysis in the lab, the heavy metals including Cr, Cd, Cu, Pb, As, Hg and Ni in tea and soil are researched. The main results are as follows.1. Three different sample digestion methods such as wet process, dry process and microwave digestion were investigated, and the last one was the best. Factors including inceptive power, digesting temperature and digesting time were studied. The optimum conditions were as follows. The inceptive power was 800,1000, 1000,700 W; and the digesting temperature was 180,200,220℃for tea and soil, 200℃. The digesting time was 5,6,7,5 min for tea and 10,8,9,5 min for soil. The digestion mixture was 5:3 ratio of HNO3-H2O2 for tea and 5:2:1 ratio of HNO3-HF-H2O2 for soil.2. The simultaneous determination of chrome, cadmium, copper and lead in samples was carried out by ICP-AES with microwave digestion. The experimental conditions including pH value and instrumental operation parameters were studied. Under the optimum condition, the detection limits of chrome, cadmium, copper and lead were 1.93 ng/mL,0.96 ng/mL,0.85 ng/mL and 16.2 ng/mL; the relative standard deviations were 0.79%,1.1%,1.2% and 0.92%; the recovery was 98%, 104%,99% and 102%, respectively.3. A method was established for the determination of arsenic and mercury in samples by hydride generation atomic fluorescence spectrometer with microwave digestion. The experimental conditions and instrumental operation parameters such as KBH4 concentration, photoelectric cell negative voltage, carrie gas flow and shield gas flow, currents of lamp and height of atomic oven which affected the determination were optimized respectively. Under the optimum condition, the linear range was 2 ng/mL～40 ng/mL for As and 0.1 ng/mL～10 ng/mL for Hg; the correlation coefficient was 0.9997 for As and 0.9992 for Hg; the detection limit was 0.049 ng/mL for As and 0.012 ng/mL for Hg; the relative standard deviation was for 2.0% As and 3.2% for Hg; the recovery was 101% for As and 95% for Hg.4. A new method for the determination of nickel in samples was carried out by flame atomic absorption spectrometry with microwave digestion. The effect of experimental conditions such as pH value, dosage of Silica gel, dosage of APDC which could point enrichment and determination sensitivity was discussed and optimized. Under the optimum condition, the detection limit of nickel was 3.9 ng/mL; the relative standard deviation was 1.3%; the recovery was 97%.5. Combining with the health quality standards of tea and the requirement for non-risk tea or organic tea garden, the food safety in tea production and soil environment was evaluated. The relation of the heavy metal content in tea with that in soil was discussed by F-test. The results showed that the amounts of seven heavy metals including Cr, Cd, Cu, Pb, As, Hg and Ni in tea samples were in standard, but the amount of Cd in ZhuZhou tea gardens near kailyards and the amount of Pb in Ningxiang tea bought from peasants were over standard. All these soils were suitable to planting non-risk tea. Based on standard of heavy metal content in soil of organic tea garden, all except Cd in ZhuZhou tea garden near kailyard were in standard. The amounts of five heavy metals including Cd, Pb, As, Hg and Ni had significant positive relations with those in relevant soils (P <0.05). And the amounts of Cr and Cu had not significant positive relations with those in relevant soils (P>0.05).
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