The Comparative Study On Mineral Element Characteristics And Tea Quality In Tea Gardens Of Jiuan And Leishan In Guizhou Province

Tea is one of the third most important cash crops in Guizhou Province and an important source of income in rural areas.In recent years,the planting area of tea in Guizhou has increased rapidly,ranking first in the country.Famous Guizhou tea brands such as Maojian,Green buds,Emerald,Red tea,Leishan Qingming Tea and Pu an Red have been formed and are favored by tea customers.Tea has made great contributions to the development of Guizhou's agricultural economy.Therefore,from the perspective of ecological geochemistry,it is of great practical significance for the large-scale cultivation of high-quality tea in Guizhou and the improvement of quality and yield to explore the geochemical characteristics of tea garden elements in the distribution areas of Jiuan clastic rock and Leishan metamorphic rock in Guizhou,find out the differences in tea quality and analyze the main factors controlling tea quality.In this study,tea leaves from Jiuan clastic rock and Leishan metamorphic rock areas in Guizhou Province are taken as the research area.Stratigraphic rocks,soil(cultivated soil layer and green soil layer)and tea leaves in the research area are taken as the main research objects.Field investigation and sampling are carried out in the planting area.The contents of majorelements,Trace elements,heavy metal elements and biochemical components(tea polyphenols and caffeine)of rocks,soil(cultivated soil layer and green soil layer)and tea leaves are analyzed and tested.The element geochemical characteristics of rock,soil(cultivated soil layer and raw soil layer)are analyzed.The correlation analysis method is used to analyze the correlation between various indexes of soil(mineral elements,soil organic matter,soil p H)and various indexes of tea(mineral elements,biochemical components)in the study area.The soil and tea in the study area are evaluated by soil pollution evaluation method and tea drinking health risk evaluation method.Combined with the geological environment data of the study area,the main geological environment control factors for comprehensively controlling the quality of high-quality tea are comprehensively controlled,and the lithologic distribution area suitable for planting high-quality tea is evaluated from the perspective of ecological geochemistry.The main conclusions are as follows:1.Jiuan district tea in Guizhou is mainly planted on the upper Permian and lower Triassic strata.The lithology is mainly shale,carbonaceous rock in the upper part of coal measure strata and sand shale.However,Leishan tea area in southeast Guizhou is mainly planted on the first member of Fanzhao formation(Ptbn_bf~1)and the second member of Qingshuijiang formation(Ptbn_bq~2).The lithology is mainly massive metasandstone and metatuff.Compared with the abundance of elements in the earth's crust,As,Li,Y,Pb,Mo,Sn,Se,Ce and Bi in the stratum rock of Jiuancha district show enrichment characteristics,while Al,As,Li,Pb,Sb,Se,Ce,Sb and Bi in the stratum rock of Leishan tea district show enrichment characteristics.According to the analysis of the rock content characteristics of the two tea areas,the strata rocks in Jiuancha area are rich in elements Ca,Fe,P,Cr,As,Cu,Y,Mo,Sn,Se,Ce,Ge and Hg,while the strata rocks in Leishan tea area are rich in elements Al,K,Mg,Na,Mn,Li,Pb,Zn,Ni,Co,Sb,Bi and Cd.Rocks rich in Al,K,Na,Zn,Sb and Bi provide sufficient mineral element background for the growth and development of tea trees and the cultivation of high-quality tea leaves.2.The Trace elements Al,Fe,Cu,Se and harmful elements As in the raw soil layer of Jiuancha district in Guizhou province,which are Trace to the growth of tea,are enriched compared with the background values of soil layer C in Guizhou province.However,Al,K and Se in the raw soil layer of Leishan tea area,which are Trace to the growth of tea,are enriched compared with the background values of soil layer C in Guizhou.Compared with the background value of soil layer A in Guizhou,Trace elements Al,Fe,Cu,Mo,Sn,Se and heavy metal elements As,Cr and Hg in cultivated soil layer of Jiuancha district are enriched.Al,Sb,Se and Hg in Trace elements,which are favorable to the growth of tea in the cultivated soil layer of Leishan tea area,are enriched.The difference of soil element content characteristics between the two tea areas was analyzed.The average contents of Ca,Fe,Mg,P,Mn,Zn,Cu,Y,Mo,Sn,Se,Ge and heavy metals As,Cr,Ni,Co and Cd in cultivated soil layer in Jiuancha area were higher than those in Leishan tea area,while the average contents of Al,K,Na,Ce,Li,Sb,Bi and heavy metals Pb and Hg in cultivated soil layer in Leishan tea area were higher than those in Jiuancha area.Compared with"soil environmental quality standard"(GB 15618-2018),the heavy metals in the soil of Jiuan and Leishan tea areas did not exceed the standard,and the overall soil quality was better.3.Jiuan tea leaves in Guizhou inherited the characteristics of most elements in rocks and soils,and the contents of K,Ca,Mg,Ce,Fe,Li,Mo,Sn,Y,Se and heavy metals As,Cr,Ni,Pb,Co,Hg and Cd in Trace elements were higher than those in Leishan leaves.However,Leishan tea inherits the characteristics of most elements in rocks and soil,and the contents of Na,P,Zn,Cu,Sb and Ge in Trace elements are higher than those in Jiuan tea.Among them,the Zn content of Leishan tea has met the national Zn-rich tea Zn content standard(40 mg/kg),which has important economic value as the development of rich-Zn tea.Compared with the food safety standard(NY659-2003)(GB 2762-2017),the content of heavy metals in Jiuan and Leishan tea leaves did not exceed the standard.4.The old tender leaves of tea tree showed strong enrichment to K,Ca,P,Mn(BCF>1),Moderate enrichment to Zn,Cu,Mg,Ni,Hg,Cd(BCF<1),and low enrichment to Al,Na,Se,Ge,Bi,mo,Fe,Sb,Sn,Li,Y,Ce,As,Cr,Pb,Co(BCF<0.1).In addition,the young leaves of tea tree have stronger enrichment ability to K,Mg,Na,P,Zn,Cu,Mo,Ge,Ni and Co than the old leaves.However,the enrichment ability of the old leaves in tea to Ca,Al,Mn,Se,Bi,Fe,Sb,Sn,Li,Y,Ce,As,Cr,Pb,Hg,Cd is stronger than that of the young leaves.Among them,the young leaves of ancient tea trees are more capable of enriching Al,Ca,Mg,Na,Se,Zn,Sn and Y than the young leaves of common tea trees,and the ancient tea trees are rich in Al,Ca,Na,Mg,Zn,Cu and Se,which has important economic significance as zinc-rich selenium tea.5.Ce,Sn,Sb,Cr,Na,Mn,Y,Ni,Pb in tea were significantly positively correlated with corresponding elements in soil(P<0.05).However,the absorption and enrichment of Al,Ca,Mn and Sn by tea leaves will increase with the decrease of soil p H.6.The tea polyphenol is positively correlated with Y in tea(P<0.05),negatively correlated with Cu and Fe in tea(P<0.05),caffeine is significantly correlated with Zn in tea(P<0.01),and significantly negatively correlated with K in tea(P<0.05).It shows that Y,Fe,Zn and K in tea affect the quality of tea by affecting the synthesis of polyphenols and caffeine in tea.However,there is a significant negative correlation between tea polyphenols and soil Mn(P<0.05),As in caffeine is negatively correlated with soil(P<0.05),which indicates that the synthesis of tea polyphenols and caffeine will be inhibited when the regional Mn and As,geological background values are high.7.Based on the analysis of the distribution,rock geochemistry,soil geochemistry and tea quality in different of distribution areas,the results show that the Banxi Group of Qingbaikou is rich in Al,K,Na,Zn,Sb,Bi and other elements in rocks,the content of heavy metals in soil and tea is low.The weathered soil has high organic matter content,the quality of tea is good.It is a high-quality tea planting area in Guizhou Province and can be used for large-scale tea planting.The distribution area of Permian Longtan Formation is rich in Ca,Fe,P,Se,As,Cu,Cr and Hg in rocks,soil and tea.The weathered soil has moderate organic matter content and tea is well.8.According to the correlation of strata,soil geochemistry and tea quality,it is considered that the distribution areas of the first section and the second section of Banxi Group in Qingbaikou System are high-quality tea planting areas in Guizhou Province,which can be used for large-scale tea planting.However,the distribution area of Permian Longtan Formation is a favorable planting area for tea.