土壤-苦丁茶树系统中铅的GF-AAS测定及其分布特性

采集不同苦丁茶树的根、茎、叶及对应的土壤样品,经过清洗、烘干、研磨等预处理后,采用高压密封罐加热消解,加入磷酸氢二铵作为基体改进剂,通过氘灯扣除背景,以石墨炉原子吸收光谱法(GF-AAS)测定样品中的铅,铅浓度在0.000—60.000ng.ml-1时与吸光度呈现良好的线性关系,相关系数r=0.9999,检出限为0.200ng.ml-1,方法精密度RSD5%,回收率93%—107%.用上述方法研究土壤-苦丁茶树系统中铅的分布表明,各种苦丁茶树及土壤中铅的分布具有类似规律,即土壤中铅含量远高于茶树中,茶树的地下部分含量分布为:吸收根主根,地上部分为:枯叶茎老叶嫩叶,其中嫩叶中铅含量远低于限量指标(Pb≤5.0μg.g-1),对茶叶服用的安全性有利.

THE DETERMINATION AND DISTRIBUTION CHARACTERISTIC OF LEAD IN THE SOIL-KUDINGCHA SYSTEM BY GF-AAS

The root, stem, leaf and soil samples of different Kudingcha trees were collected, and preheated by cleaning, baking, grinding, and high-pressure sealed digestioa To measure Pb by graphite furnace atomic absorption spectrometry (GF-AAS), ammonium phosphate was added to reduce matrix interferences, and deuterium lamp was used for background subtraction.The linear range of the standard curve was between 0.000 ng · g~(-1)-60.000 ng · g~(-1), linear correlation coefficient 0.99989, detection limit 0.200ng · ml~(-1), RSD < 5%, recovery rate 93%-107%.The results of kudingcha samples showed that the distribution of lead was similar in different Kudingcha trees in that the lead content in soil was far more than in Kudingcha trees.The distribution of lead in underground parts of Kudingcha trees was; absorbing roots > main roots, the distribution of lead in above-ground parts was: dead leaves > stem > old leaves > young leaves.The content of lead in young leaves was far less than the limit (Pb≤5.0μg·g~(-1)) , which was favorable for the safety of drinking-tea.