Study On The Bioavailability Of Heavy Metals In Soil Of Wuyi Rock Tea And Its Influencing Factors

Wuyi rock tea is a Chinese traditional famous tea,and oolong tea in China is the best.It is one of the top ten famous tea in China.With the development of economy and tourism activities,the negative influence of human factors on the environment is becoming more and more prominent.More and more attention is paid to the quality and safety of tea.The problem of heavy metal pollution is one of the focuses.In this paper,the heavy metal contents in Wuyi rock tea soil and fresh tea leaves were tested and analyzed.The chemical morphological characteristics and its pollution evaluation:and influencing factors of heavy metal elements such as Pb,Cu,Zn,Ni,Cr,Cd,As in the soil of Wuyi rock tea were analyzed were studied by continuous BCR extraction method.It is of great significance to objectively assess the risk of heavy metal pollution in tea garden soil and to ensure the safety of tea.Through research,the main conclusions obtained are as follows:?1?The total amount of heavy metals in soil and its pollution assessmentThe contents of heavy metals Cd,Cu,As,Cr,Zn,Pb,and Ni in Wuyi rock tea range from 0.3 to 0.15 mg/kg,29.87 to 150 mg/kg,1.94 to 14.12 mg/kg,15.74 to 84.5mg/kg,34.54¹54.4mg/kg,36.52¹06.06mg/kg,and 5.47⁶1.96mg/kg,Among them,some of the Zn,Cd,Cu,and Ni elements in plots exceeded the soil environmental quality class II standard,and the over-standard rate was 3.45%.The average contents of Cd,Cu,Zn,Pb,As,and Ni in the soil exceeded those of Fujian Province.The content of Cd is more than 3 times the background value.The probability of Cd,Cr,Cu,Zn,Pb,As,Ni elements exceeding the background value is respectively100%,41.39%,100%,89.66%,100%,34.48%,79.31%.The over-standard rate order is Cd=Cu=Pb>Zn>Ni>Cr>As.Assessment of Environmental Quality of Soil Heavy Metals in the Study Area Using Land Accumulation Index and Potential Ecological Risk Index Method.The results show that the results obtained by the two assessment methods are basically the same.Most soils are at the lowest level of pollution.?2?Distribution characteristics of chemical forms of heavy metals in soilFrom the experimental results,it can be seen that Cd elements are mainly in the weak acid-soluble state,accounting for 48.35%of the total amount.Other elements are mainly in the residue state.The non-residual state of Pb accounts for 49.81%of the total amount.It is easy to release in large quantities under reducing conditions,thus inhibiting the growth of tea plants.From the coefficient of variation,the chemical forms of all metal elements are moderately variable.It shows that the chemical forms of heavy metals in soil are affected by different degrees of external disturbances.?3?Heavy metal content and pollution assessment of teaThe contents of heavy metals Cd,Cr,Cu,Zn,Pb,As,Ni,and Hg in tea leaves ranged from respectively 0.0079 to 0.081 mg/kg,0.336 to 1.27 mg/kg,5.03 to 15.2mg/kg,11.2 to 44.83 mg/kg,0.192 to 0.525 mg/kg,0.032 to 0.09 mg/kg,2.29 to 9.14mg/kg,and 0.0016 to 0.0066 mg/kg,Both are lower than the NY659-2003 green food tea,NY/T288-2012 tea chrome,mercury,arsenic and fluoride limit standards.From the single pollution index and the Nemero comprehensive pollution index,we can be seen that the single factor pollution index P_i of Cd,As,Pb,Hg,Cr and Cu in tea plantations is less than 1.The comprehensive pollution index P_N is less than 0.7,and the grade of soil pollution in tea gardens is grade I,which is within the safety range.?4?Analysis of bioavailability of heavy metals in Wuyi rock tea soilThe average order of bioavailability of soil heavy metals was Cd?59.41%?>Pb?26.96%?>Cu?23.93%?>Ni?21.85%?>Zn?14.26%?>As?12.83%?>Cr?3.11%?.The order of the TF_totalotal is the order of Zn>Cd>Ni>Cu>Cr>As>Pb.The order of the average mobility coefficient(TF_avail)of the bioavailable state of heavy metals in soil was:Zn>Ni>Cu>Cr>Cd>As>Pb.From this,it can be seen that the order of the migration coefficients of each heavy metal in both TF_availvail and TF_totalotal is inconsistent.TF_availvail is higher than TF_total,This may be due to the difference in the content of bioavailable states of various elements.?5?Influencing factors of heavy metal content in soil and teaThe results of the correlation analysis between the total amount of heavy metals in soil and tea and the main physical and chemical indicators of the soil showed:The physical and chemical properties of the soil?pH and organic matter?have different effects on the presence of heavy metals in the soil.Soil pH also has different effects on the heavy metal content of tea.The correlation between organic matter content and the total amount of heavy metals in tea leaves was not significant.It shows that the heavy metal content of tea is less affected by organic matter.Correlation analysis,factor analysis and cluster analysis of heavy metals in soil and tea.The results show that the correlation analysis,factor analysis and cluster analysis have the same conclusions.The sources of Cr,Pb,and Ni in the earth tea garden soil are related to the parent material,and they are also affected by agricultural activities.As,Zn in the soil of tea plantations mainly comes from the atmospheric deposition of transportation and waste combustion.The main sources of Cd in tea garden soils are pesticides,fertilizers,and other agricultural activities.Cu,Ni and Cr in tea are mainly sources of agricultural activities such as pesticides and fertilizers.Pb and As in tea mainly come from traffic sources.Cd and Zn in tea are mainly derived from agricultural activities and transportation.