Environmentally Geochemical Characteristics And Geographical Origin Authentication Of Tea From Major Tea Producing Areas In Guizhou Province,China

The largest country for the cultivation area of tea in the world is China.The cultivation area of tea plant in Guizhou province,China has been increased to 4.78×10⁵ hm²,ranking the first in China for four consecutive years by the end of December 2018.However,the environmentally geochemical factors that affect the cultivation and growth of tea in Guizhou were not still understood in details.The geographical original authentication of tea in Guizhou has not been carried out systematically.Therefore,seven major tea producing areas in Guizhou were selected and investigated,including Pu'an?PA?,Anshun?AS?,Duyun?DY?,Leishan?LS?,Liping?LP?,Meitan and Fenggang?MTFG?,and Shiqian?SQ?.After identifying the stratigraphic distribution and lithologic properties,bedrocks,subsoils,cultivated soils,young tea leaves,and old tea leaves were collected from these seven tea-producing areas.Geochemical multi-elemental concentrations in all samples were analyzed using inductively coupled plasma mass spectrometry?ICP-MS?.The soil p H was also measured using the p H meter.In addition,the strontium?Sr?isotopic ratio(⁸⁷Sr/⁸⁶Sr)in28 young tea leaves samples?four samples per region?was analyzed using thermal ionization mass spectrometry?TIMS?.The geochemical characteristics of bedrocks from seven tea producing areas were studied,and the causes forming the geochemical characteristics differences of bedrocks from different geological backgrounds were also elucidated.Moreover,the distribution characteristics of mineral elements in cultivated topsoils and subsoils from seven tea-producing areas were investigated.The influence from strata and lithology on elemental distribution of cultivated topsoils and subsoils were investigated in view of the geological background.Simultaneously,the quality and security of soil and tea were evaluated in Guizhou systematically.The migration and enrichment of mineral elements in soil-tea system were studied,and the effects of soil elemental contents and p H values on the elemental contents in tea leaves were also investigated.Furthermore,the geographical origin identification of tea was studied using the multi-elemental concentrations.The role of soil geochemical elements in discriminating geographical origin of tea leaves was analyzed.The rare earth elements?REE?fingerprints in tea leaves were used to trace the geographical origin of tea leaves and identify the cultivars of tea leaves.Finally,⁸⁷Sr/⁸⁶Sr in tea leaves were used to identify the geographical origin of tea leaves combined with mineral elemental concentrations in tea.The main conclusions gained in this study were as follows:1)Many strata were outcropped in the seven tea-producing areas.The strata including the Fanzhao Formation of Qingbaikou System to the Quaternary Pleistocene were outcropped except for the Jurassic,Cretaceous,and Neogene.There were mainly two types of rock i.e.,carbonate rock and clastic rock.The mineral multi-elemental concentrations in clastic rocks were significantly greater than those in carbonate rocks.The Cd concentrations in limestones from the Carboniferous Maping Group and Permian Maokou Formation in AS and LP ranged from 0.457 to 3.57 mg/kg with a mean of 2.01 mg/kg?n=4?.Concentrations of some mineral elements in quartz sandstones from the Devonian Bangzhai and Dushan Formations in tea plantations from Guiding,Duyun were low.The concentrations of harmful elements?e.g.,Tl,Pb,As,Sb,Cd,and Hg?in the Cambrian dolomite in SQ was significantly higher than those in the dolomite of same Formation in MTFG.This was related to the influence of regional mineralization in the Cambrian Qingxudong Formation in SQ.The concentrations of toxic elements?As,Cd,Cr,Pb,Hg,Sb,Tl,Sn,etc.?in the bedrocks from the main tea-producing regions was low in comparison with the elemental abundance in the crust.2)The topsoils from the main tea-producing regions were extremely acidic?p H=4.02?,and the subsoils were strongly acidic?p H=4.5?.Soil acidification of tea plantation was severe,which can be related to the specific physiological properties of tea plant and fertilization.Concentrations of mineral and harmful elements in subsoil from the carbonate rock were higher than those from the clastic rock.However,the K content in subsoils showed an opposite trend.The Mg concentration in soils from MTFG and SQ was high,which can be attributed to the control of the dolomite distribution.Potassium concentrations in some topsoils were relatively high owing to the distribution of clastic rocks.Concentrations of As,Hg,Sb,Cr,and Ni in some topsoils in AS were greater than those in other regions,which can be ascribed to the mineralization of local strata and the enrichments of Cr and Ni in the soil derived from the weathering of carbonate rock.The Cd,Pb,and Tl contents in some topsoils from SQ was relatively high.High Cd concentration was mainly restricted by the distribution of the limestone of the Permian Wujiaping and Changxing Formations.Moreover,the weakly mineralized dolomites of the Cambrian Qingxudong and Gaotai Formations caused the high contents of Pb and Tl in topsoils from SQ.The contents of multi-metals in the topsoils from DY and LS was lower than those from other regions,and this can be closely related to the geological background of clastic rocks.The key environmental geochemical factors that affected the growth of tea plants were high concentrations of K and Al and low concentrations of Ca,Mg,As,Hg,Cd,Sb,Cr,and Ni in soils from the clastic rock area.The average concentrations of Cu,Cd,As,Cr,Ni,Pb,Zn,and Hg in the topsoils did not exceed the screening values of agricultural land soil pollution risk.However,some sites exceeded the corresponding standard,and the exceeding rate were 24.6%for Cu,23.59%for Cd,10.62%for As,6.67%for Cr,4.62%for Ni,3.08%for Pb,2.62%for Zn,and 1.03%for Hg,respectively,owing to the local mineralization and anomalously geochemical background values.3)The concentrations of Ca,Fe,Mn,Se,and Sr in old leaves were higher than those in young leaves,whereas the concentrations of Mg,P,S,K,Na,Cu,Zn,Ni,Co,and Rb in leaves of tea exhibited the inverse tendency.The concentrations of Mn,Ni,Co,Mo,Se,Cr,Al,and Tl in old leaves of tea in DY and LS were the lowest,which may be closely related to the geological background of clastic rocks.The concentrations of Cu,As,Cd,Pb,Hg,and Cr in young leaves of teas?n=199?did not exceed the Chinese,World Health Organization?WHO?,and European Union?EU?tea standards limits,whereas some old leaves of tea had excessive levels.The concentrations of Al,As,Cd,Cr,Pb,Hg,Sb,and Tl in old leaves of tea were higher than those in young leaves.Avoiding the mixing of old leaves of tea is beneficial to improve the quality and security of tea in Guizhou.4)Leaves of tea showed the strong enrichments of Ca,Mn,K,P,and S?BCF>1?,moderate enrichments of Cu,Zn,Ni,Se,Sr,and Cd?0.1<BCF<1?,weak enrichments of Na,Co,Mo,Pb,and Sb?BCF<0.1?.The enrichment abilities of Mg,K,Na,P,S,Cu,Zn,Co,and Ni in young leaves of tea were stronger than those in old leaves,while the enrichment capacities of Al,Fe,Ca,Mn,Se,Mo,Sr,As,Hg,Pb,Cd,Cr,Sb,and Tl in young leaves of tea showed the inverse trend,which could be related to the long-term accumulation and weak remobilization ability of non-nutritional elements in old leaves of tea.The concentrations of Ca,Mg,As,Cd,Tl,Mn,Cu,Co,Ni,and Sr in leaves of tea were significantly positively correlated with the corresponding elements in cultivated soil?p<0.05?.Moreover,the concentrations of Fe,K,Pb,Hg,Cr,Sb,Tl,Mn,Cu,Zn,Ni,Co,and Rb in leaves of tea had a negative correlation with soil p H to a certain extent.Soil acidification in tea garden promoted the accumulation of heavy metals in leaves of tea;thus,it was particularly important to avoid further soil acidification in tea garden.5)The 28 mineral elements?As,Ba,Bi,Ca,Cd,Ce,Co,Cr,Cs,Dy,Er,Ho,K,La,Li,Na,Nb,Nd,Ni,P,Pb,Pr,S,Sb,Th,U,W,and Y?in 87 tea leaves samples from AS,MTFG,and LS significantly differed among these three regions?p<0.05?.Leaves of tea from each region have their own unique characteristics of elemental geochemical fingerprints.The correct discrimination rates of the linear discriminant analysis?LDA?and orthogonal partial least squares discriminant analysis?OPLS-DA?models were 98.9%and 100%,respectively.The significantly correlated elements between soils and tea leaves were used to authenticate the geographical origin of tea,indicating the excellent performance.The accurate identification results were rarely affected by the cultivars of tea plant.The REE fingerprints in leaves of tea were used to trace the geographical origins of tea and identify four cultivars of tea plant?i.e.,Longjing 43,Fengqing big leaf,Fuding small leaf,and Qianmei 601?.Their correct discrimination rates for the LDA model were 86.3%and 95.5%,respectively,indicating the excellent performances.6)The ⁸⁷Sr/⁸⁶Sr values in young leaves of tea from Guizhou varied widely,ranging from0.707879±0.000012 to 0.724356±0.000016?n=28?.The ⁸⁷Sr/⁸⁶Sr ratios in leaves of tea were obviously affected by the bedrocks in different strata.The bi-dimensional scatter plot consisted of ⁸⁷Sr/⁸⁶Sr in leaves of tea and respective concentrations of U,Pb,Al,Fe,Li,Na,Bi,Ba,Zn,and Ge in leaves can effectively discriminate leaves of tea from PA,DY,and LP,showing a promising performance.In terms of leaves of tea from AS,LS,and MTFG,the⁸⁷Sr/⁸⁶Sr composition in tea leaves and respective concentrations of certain mineral elements in leaves of tea can only identify the individual production area?AS or LS?.