Investigation On The Content And Correlations Of Rare Earth Elements And Heavy Metals In Tieguanyin Tea Leave

Fujian,located in South of China,has a long history of tea culture due to its humid climate.Because there are over 500 kinds of phytochemicals in tea leaves,tea beverage is regarded as the natural resource of micro nutrition for human being.However,excessive heavy metal content in tea leaves has become one of the major problems that influencing tea product quality in recent years.Additionally,the rare earth elements,which are considered as "growth regulator" for animals and industrial "vitamin",have also been found high risks of metabolic disorders for human health when people having long-term intake.In this study,the content of rare earth elements and heavy metals in the leaves of Tieguanyin tea plants during different growing stages in AnXi county,Fujian province were investigated.The purpose of this study is to understand the change of rare earth element and heavy metal contents in the leaves with the development of Tieguanyin tea plants,and to provide the basic theory for the safety practice of Tieguanyin tea product.The results were shown in the following.1.Tieguanyin tea plants in Anxi county were used as material,fresh tea leaves were sampled in the same interval from January 2014 to December 2016 to investigate changes of heavy metal content in leaves during the different plant growing stages.The results showed that the content of heavy metals,including lead,copper,arsenic and cadmium,was all under the safety control value.The cadmium content in tea leaves changed uniformly with the development of Tieguanyin tea plants,which was always lower than the control value,0.5mg/kg.Whilst,the copper content in tea leaves increased with the development of Tieguanyin tea plants,fluctuating at 5.0±1.0mg/kg but all under the safety control value,30 mg/Kg.The lead and arsenic content showed slow increment as growing stage increasing.2.The rare earth content in tea leaves were also detected at the same time.The results showed that the content of rare earth element in most samples was higher than the standard.the content of Scandium(Sc),Pr(Pr),Samarium(Sm),Europium(Eu),Gadolinium(Gd),Terbium(Tb),Dysprosium(Dy),Yag(Ho),Erbium(Er),Thulium(Tm),Yttrium(Yb)and Lutetium(Lu)was lower than the standard value,respectively.With the development of tea plants,the content of Scandium(Sc),gadolinium(Gd),dysprosium(Dy)and Ytterbium(Yb)were slowly decreased,while the content of erbium(Er)showed slowly increased.However,the content of Yttrium(Y),Lanthanum(La)and cerium(Ce)and neodymium(Nd)was significantly higher than the national standard value,inducing the total content of rare earth element in tea leaves over the standard value.3.Based on the investigation of heavy metals and rare earth content in tea leaves from January 2014 to December 2016,correlation analysis on the content of heavy metals and rare earth content in tea leaves was further conducted.The results showed that that there was weak relationship between total heavy metal content and total rare earth element content in tea leaves.The content of lead,arsenic and cadmium in tea leaves presented positive relationship with the total rare earth content,while the copper and total heavy metal content was all negatively related to the total rare earth element content.Meanwhile,the content of each rare earth element showed weak relationship with total heavy metal content in tea leaves,which was all lower than 0.03.The content of La,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,and Lu in tea leaves displayed weak negative relationship with the total heavy metal content,while the Sc,Y,and Ce content showed positively related to total heavy metal content.In summary,the results in this paper provide a new clue on the content change of heavy metal and rare earth element content in tea leaves with the development of Tieguanyin tea plants.