Assessment And Prediction On Heavy Metals Status For Soils And Fresh Tea Leaves In Jiangxi Major Tea Regions Based On GIS And Data Mining Technology

After sampling in natural tea plantation and chemical analysis indoors, with the support of GIS (Geographic Information System) technology especially like geostatistical Kriging interpolation, several data mining technologies, such as classical statistics and fuzzy mathematics were chosen to research the main sources of pollution, spatial variability characters and their predition and temporal prediction for six types of heavy metals(Cu, Pb, Cd, As, Hg and Cr) in soils and fresh tea leaves in major tea regions of Jiangxi provice. Firstly, more tightening limited values for fresh tea leaves were suggested and discussed in this study other than present national limited values for branded tea. Fresh tea leaves were the first-hand raw materials for branded tea, so we could get the basic risk assessment data we were facing while tea were drinked or eaten by evaluating the pollution stadus and predicting for them. It was more significative to keep watch risk than survey afterwords for monitoring safty of tea. It's the first time to sample outdoors in Jiangxi major tea regions with soils and fresh tea leaves followed by examing, estimating and predicting.The main results obtained in this dissertation were summarized as follows:1. Descriptive statistics, Nemerow integrated pollution index (NIPI) and multivariate analysis (cluster analysis, discriminant analysis and correspondence analysis) were used to get assessment results for soils and fresh tea leaves in Jiangxi major tea regions with respect to initial concentrations, pollution index and integrated characteristics of multivariance. In conclusion, there was a slight difference among heavy metals in soils and fresh leaves from the five tea producing districts divided artificially in Jiangxi but without clear natural separatrix. However, there were different tea gardens at different pollution level in each district, which indicated their various management levels and the importance for better running. Considering mean and medium value, whole concentrations or avalible concentrations of heavy metals and fertility level value in upper soils (0-20cm) were higher than it in sublayers (20～40cm) but without significant differences except the whole nitrogen, avalible phosphorus, avalible Pb and avalible Cd mainly with middle level of spatial variability. It indicated that soils pollution was just slightly affected by human activities without serious change. Respectively, there were 47.7%,77.3% and 100% of tea gardens which could be suitable for planting organic tea, green tea or nuisanceless tea conformed to its related environmental standard when considering NIPI in upper soil. The pollution level in sublayer was slighter. The pollution level in various districts was close with different main heavy metal. The highest NIPI was for As, then the Cr. The higher polution of Cr in northern district in Jiangxi was assumed to be related to fertilizer, while the higher polution of As in southern district in Jiangxi was assumed to be mainly related to soil parent material combined with humanity.2. More tightening limit values for fresh tea leaves other than branded tea are more reliable when used to assess metal contamination in fresh tea leaves. Based on it, NIPI of new tea leaves was caculated to be 0.99 indicating high precautious level while old leaves reach to slightly polluted level which reminded us to be carefull to use it as leaf food or powder additives. It's good and uniform or similar in natural producing condition in Jiangxi and there are no great differences between the mountain group and the road one. The results revealed that concentrations of Cu, Pb, Hg and Cr showed highly significant differences within new leaves and old leaves which indicated obvious accumulation accompanying with years. Respectively, Cu and Cr of new leaves in 11.4% and 6.8% tea garden came to slightly polluted level (2≥NIPI>1). Appraisal results of Jiangxi province were slightly polluted for Cu and Cr, precautious for Pb (0.6<NIPI≤1), while safe for Cd, As and Hg (NIPI≤0.6).3. A fuzzy mathematics method was adopted to estimate the stadus of soils fertility level in Jiangxi major tea regions. The results reveal that integrated fertility index (IFI) of upper soil sampled was 0.64 for mean while 0.63 for medium which indicated to be better than average expect region of number A in north-western Jiangxi where was worse than average. Among these regions, it's the region of number B which showed the most diversity of IF I related to the most difference on fertilizer management. For mean and medium value of soils, pH was on the little low side with higher for organic matter, whole potassium and alkali-hydrolyzable nitrogen, a little rich for whole nitrogen, and a little low side for avalible potassium and whole phosphorous, while worst for avalible phosphorous. So it was suggested that fertilizer with potassium and phosphorous should be applied more than organic fertilizer in Jiangxi tea regions combined with better or more regular management to prevent the deterioration of pH especially in extensive planting tea gardens. Lime or plant ash was a good choice for neutralization to get proper soil pH for tea plant. Based on IFI, ordinary Kriging interpolation was used to predeterminating the spatial variability of upper soil. It showed that IFIs were higher in middle and east regions with a high value center of Wuyuan county than north-west parts in Jiangxi.4. Pearson correlation analysis and factor analysis were executed to analysis the major resources of heavy metals pollution in Jiangxi main tea regions consulting records as sampling. The results indicated that As and Cr were the major pollution matters brought from soil parent material combined with humanity, such as polluted water, sewage, exhaust gas and floating dust arised from industry in northern Jiangxi, rebundant fertilizer in agriculture and rich mineral reserves in southern Jiangxi. It was the old leaves that were mainly polluted for fresh leaves as to show a little significant correlation with soil heavy metals, while new ones were weakly correlated with soil. However, new leaves were significant to old ones considering heavy metals which indicated the possibility of heavy metals thansfer during the leaves of two types. Thus, major resources of heavy metals pollution for soils also were the major resources for new tea leaves.5. Correlation analysis revealed that pH of soils could effect accumulation of heavy metals in fresh leaves through influence metabolization of plant. Not only for improving the level of avalible phosphrous, but also for controling the concentrations of Pb,Cd,Hg in old leaves, it was important to prevent deterioration of pH. There were significant correlations for the same heavy metal concentrations whole or avalible between two layers of soils, the same as the fertility level. It indicated a possibility of thansport in heavy metals within them. Furthermore, factor analysis showed the same metal in two layers was caculated into the same factor representing the same pollution resources. However, there were no same resources for Cu and apart from the other five metals of fresh leaves.6. With the support of GIS geostatistical ordinary Kriging interpolation, spatial variability characters and their predition were caculated. For prediction error, it was almost satisfied with ME and MSDE almost zero and RMSDE near to one, while RMSE and ASDE was a little higher than zero. Prediction precision could be better after additional sampling in middle region in Jiangxi like Taihe county or Xinyu city to shorten the sampling distance. Threshold value of NIP] of two was used to make a indicator Kriging interpolation for integrated pollution level of soils. The results revealed that probability of 65.6% exsited in south-western Jiangxi when NIPI exceeding the value of two which referred to moderate pollution and not suitable to plant green tea. Other regions were better for producing green tea and the sublayer was better than the upper one, which indicated just upper pollution presented that shoule be modified earlier. Threshold value of NIPI of 0.6 was used to make a indicator Kriging interpolation for integrated pollution level of leaves. The results showed that regions with higher probability of NIPI exceeding 0.6 spreaded around the provincial capital of Nanchang city, which also indicated the effect of industy and humanity activities on leaves pollution.7. Temporal prediction divided into optimistic scene and unmutation scene were used to predict the heavy metals concentration of studied area in 2025 as to the Kriging interpolation maps. The results showed that the concentration will just decrease a little in optimistic scene with 2.4%～4.5%, and medium value of new leaves nearly decreased; Furthermore, it will be getting worse in unmutation scene. Cr, Hg, As and Cd in upper soil and Cu, Cd, As, Cr in new leaves will exceed the top threshold value with percentage of 2.3%,6.8%,22.7%,2.3%,45.5%,2.3%,4.6% and 68.2%, respectively. It's necessary to pay attention to heavy metals pollution in tea gardens for we can still produce organic or green tea in future. 8. Rapid ultrasound-assisted extraction (UAE) procedures were firstly developed for the determination of Hg and Pb in tea leaves followed by atomic spectrometry. A Plackett-Burman design followed by response surface methodology was used to get the optimized results:for Hg, with 6 min of presonication time,8.1 min of sonication time,70.5℃of ultrasonic bath temperature,4.4 mL of HNO3: H2O2(1:1, V/V) and 300 mg of sample mass; for Pb,200mg sample added HNO3: H2O2 (1:1, V/V) 5mL should be treated with UAE for 8.4min at 78.0℃after soaking 6min at 40 kHz of ultrasound frequency. No significant differences were established between the analytical results of UAE method and national standard method.Exploring for several years, three fields of innovations or new developments in this study were showed as follows:1. It's the first time for us to sample fresh tea leaves in natural tea plantation outdoors of Jiangxi at home and abroad. Other than pot incubation experiment, it's more representative of current situation of heavy metals pollution for it's raw materials for branded tea. Thus the study of fresh tea leaves could be better for assessing the quality of tea in Jiangxi, finding the problem in tea plantation management, drawing up countermeasures and resolving methods in advance to hold back the deterioration of heavy metals pollution in tea. Also, it offered a first-hand practical reference for tea industry development.2. Prediction maps, as the same as probability maps of integrated pollution level, were caculated for the first time for spatial variability of heavy metals in fresh tea leaves and soils in Jiangxi province based on GIS Kriging interpolation. The range and the degree of pollution were defined for offering information to make up policy about recovering and additional sapmling. It's an integrated innovation on study methods. Also, there was an integrated innovation on study ideas for classic statistics, multivariate analysis (cluster analysis, discriminant analysis and correspondence analysis) and fuzzy mathmatics were fistly integrated to get more macroscopical assessment results for soils and fresh tea leaves in Jiangxi major tea regions. 3. A new standard with three degree of limited values was announced and discussed firstly for fresh tea leaves. Processing pollution levels following plucking should be eliminated from the standard values of branded tea to assess the fresh leaves more properly and tightening.