基于Copula函数的茶园土壤铜锌空间协同效应研究

Study on the Spatial Synergistic Effect of Copper and Zinc in Tea Garden Soil Based on Copula Function

揭示茶园土壤Cu、Zn空间协同效应对有效预防和治理土壤Cu、Zn污染,保障茶叶品质具有十分重要的作用。论文以江浙两地典型茶叶种植区为研究区,运用Copula函数对土壤Cu、Zn含量协同关系进行模拟、Kriging/IDW插值法进行空间估计、标准差椭圆模型进行空间效应分析。结果表明:1)研究区茶园土壤Cu、Zn含量二元频率直方图呈"J"型,具有上尾相关、下尾渐近独立的特征,其上尾相关系数λup及Kendall、Spearman秩相关系数分别为0.345 4、0.273 5、0.396 0,表明二者具有显著的正向相关性,建议加强土壤Cu、Zn含量监测,提升预警,避免复合污染;2)土壤Cu、Zn含量整体水平协同程度较高,局部因不同主导因子影响协同程度较低,应强化土壤Cu、Zn污染全域协同治理及局地因情施策的效果;3)Copula函数、Kriging/IDW估计以及标准差椭圆模型测算结果能相互印证,3种方法结合可更全面客观地反映两者的空间协同效应,为土壤Cu、Zn污染防治提供参考依据。

It is very important to reveal the spatial synergistic effects of Cu and Zn in tea garden soil in effectively preventing and controlling soil Cu and Zn pollution and ensuring the quality of tea. Taking the typical tea plantations in Jiangsu and Zhejiang provinces as the study areas,this paper simulated the synergistic relationship between Cu and Zn content in the soil with Copula function, estimated the spatial regionalized variables of Cu and Zn in soil with Kriging/IDW interpolation method, and analyzed the spatial synergistic effects with Standard Deviation Ellipse Model. The results showed that： 1） The frequency histogram of the soil Cu and Zn content in the study area showed a＂J＂type distribution, which indicated that the upper tail is correlated while the lower tail is asymptotically independent; the upper tail correlation coefficient, the Kendall rank correlation coefficient, and the Spearman rank correlation coefficient between the soil Cu and Zn content were 0.345 4, 0.273 5, and 0.396 0, respectively;there is a positive correlation between the Cu and Zn content in soil, so it is recommended to strengthen the soil Cu and Zn content monitoring and improve early warning to avoid combined pollution. 2） As a whole, the correlation between soil Cu and Zn content was higher,but in some local areas it was lower due to the different dominant factors, for example, the soil Cu content in the west of Longjing was mainly affected by the thickness of tillage layer, while the soil Zn content showed a significant negative correlation with soil Se content at the 1%level, and their correlation coefficient was-0.288. Therefore, it could be considered to deal with the pollution of soil Cu and Zn together in the global areas and combine with the actual situation when dealing with the pollution of soil Cu and Zn in the local areas. 3） Copula function, combined with Kriging/IDW estimation and Standard Deviation Ellipse Model, can reflect the synergetic relationship between the content of soil Cu and Zn more truly and effectively and provide reference basis for the determination of Cu and Zn.