| With the understanding of the role and effectiveness of the tea beverage, theaccession of Chinese’ agricultural products to the WTO as well as the improved quality oflife, demands on the quality of the tea become higher. Reports of the overweight of heavymetals in tea were appeared in recent years. Environmental quality of tea ground soilarousing concern, due to heavy metal in tea mainly comes from soils. Researchesrevealed that tea ground soil and tea leaves were polluted by heavy metal in differentdegrees, resulted from the use of chemical fertilizers, herbicides, pesticides and otherchemical substances and the development of surrounding industry, tourism andtransportation, so long-term consumption of tea that heavy metals overweight will easilycause the accumulation of chronic poisoning. The distribution of heavy metal content andform in tea ground soil under different ecological conditions were investigated bysampling tea ground in Wannan (southern Anhui province), to reveal the heavy metalbioaccessibility in tea tree that affected by soil heavy metal, on one hand, have scientificsignificance in knowing the environmental behavior, chemical form and bioaccessibilityof heavy metals in tea ground soil and promoting the development of environmentalgeochemistry subject of heavy metals, on the other hand, the investigation of soil heavymetal and its bioaccessibility provided theoretical basis for maintaining the ecologicalenvironment of tea ground soil and improving the tea yield and quality,producedinstructive significance for safety tea production.The soil and fresh tea leaves were collected from Wannan tea garden. The content ofZn,Cu,Pb,Ni,Cr in soils and tea leaves, the chemical speciation (the exchangeable,carbonates, Fe-Mn oxides, organic bounds and residuals) of soil heavy metal, thephysicochemical properties (organic matter, pH, available phosphorus,alkali-hydrolysable nitrogen,water content,etc.) of soil were measured,this paper alsoanalyzed the distribution characteristics of soil heavy metal chemical speciation, andbased on its to obtain the bioaccessibility of heavy metal in Wannan and the factors thatinfluence heavy metal speciation and bioaccessibility. The main conclusions are asfollows:(1) The concentration of Zn,Cu,Pb,Ni,Cr in Wannan tea garden soils were29.51～194.96mg/kg、15.10～150.74mg/kg,14.15～94.44mg/kg,2.79～68.10mg/kg,12.64~121.11mg/kg respectively, the mean concentrations of Zn,Cu,Pb,Ni,Cr were90.77mg/kg,47.29mg/kg,40.41mg/kg,21.87mg/kg,46.63mg/kg respectively, they wereexceed the soil background values, the excessive rates were1.41%,305.92%,70.87%,102.69%,15.68%respectively, the highest Cu was4times the soil background values. soil heavy metal spatial variability was obvious in Wannan tea garden, the coefficient ofvariation was more than30%, the order of the coefficient of variation wasCr(69%)>Cu(63%)>Ni(56%)>Zn(40%)>Pb(37%).Correlation analysis showed that: theconcentrations of heavy metal were mainly influenced by soil pH, organic matter,available phosphorus, alkali-hydrolysable nitrogen and other soil physicochemicalproperties.(2) The concentration of Zn,Cu,Pb,Ni,Cr in tea leaves of Wannan tea garden were83.80~150.80mg/kg,10.80~36.00mg/kg,0.05~1.60mg/kg,3.65~19.15mg/kg,1.40~13.95mg/kg, the order of mean concentration was Zn(109.76mg/kg)>Cu(15.51mg/kg)>Ni(9.50mg/kg)> Cr(3.02mg/kg)> Pb(0.59mg/kg).(3) The overall speciation distribution of Zn: residuals> Fe-Mn oxides> organicbounds> exchangeable> carbonates, Cu: residuals> Fe-Mn oxides> organic bounds>carbonates> exchangeable, Pb: Fe-Mn oxides> residuals> organic bounds> carbonates> exchangeable, Ni: residuals> Fe-Mn oxides> organic bounds> exchangeable>carbonates, Cr: residuals> organic bounds> Fe-Mn oxides> carbonates> exchangeable,in the five heavy metals speciation, residual fraction and non-residual fraction content inthe soil are quite different, the distribution of the chemical speciation of heavy metals inthe soil of tea garden that in different tea plantation ecological environment were alsohave differences.(4) The distribution law of different soil heavy metals chemical speciation in Wannantea garden was influenced by different factors, which including total heavy metal, soilphysicochemical properties as well as the ecological environment of tea garden (such aselevation, slope, planting years). Correlation analysis showed that: chemical speciation oftea Garden soil heavy metals (Zn, Cu, Pb, Ni, Cr) was influenced by total heavy metal,organic matter, pH, available phosphorus, alkali-hydrolysable nitrogen, water content,altitude, planting years, slope, etc.(5) Heavy metals bioaccessibility of Wannan tea garden mainly reflected bybioavailability factors, migration factors and conversion factors, the order of the averagevalues of five heavy metal bioavailability factor was: Zn(5.83%)>Pb(5.40%)>Cr(5.12%)>Cu(0.87%)>Ni(0.17%),of migration factor was: Zn(3.77%)>Cr(2.54%)>Pb(1.26%)>Cu(0.39%)>Ni(0.10%); the ranges of five heavy metal (Zn、Cu、Pb、Ni、Cr) conversionfactor were0.61～3.44,0.19～1.09,0.001～0.044,0.20～1.57,0.013～0.654respectively,and the order of its mean values was: Zn(1.50)>Ni(0.54)> Cu(0.44)>Cr(0.10)>Pb(0.02).The biological activity, migration and conversion ability of heavy metals in differentecological conditions were also different. |
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