摘要
为了深入探讨重金属空间分布,用频率分布、双峰拟合和分离的方法研究了北京市耕作土壤重金属Cu、As、Cd、Pb的统计分布特征。结果表明,4种重金属都呈明显的双峰分布,可以用双高斯密度函数很好地拟合经对数变化的实际测量数据,证明北京市耕作土壤中重金属Cu、As、Cd、Pb都包括2个相对独立的对数正态分布总体。根据拟合频率密度函数求得的重金属Cu、As、Cd、Pb的2个子总体的几何均值分别为:(23.35±6.39)mg/kg和(95.84±38.73)mg/kg、(9.35±2.20)mg/kg和(23.67±6.16)mg/kg、(0.1208±0.0334)mg/kg和(0.3548±0.2344)mg/kg、(20.07±6.07)mg/kg和(82.55±39.33)mg/kg,都表现为明显的低值组和高值组。从统计学的角度,可以解释重金属含量呈双峰分布的原因,但从其空间分布上来看,双峰的成因较为复杂。
In order to thoroughly investigate the spatial distribution of heavy metals, the methods of frequency distribution, bimodal fitting and separation were used to study the characteristics of statistical distribution of heavy metals in Beijing cultivated soil. It was demonstrated that, Cu, As, Cd and Pb were bimodal distribution. Double Gaussion Function could be used to fit the empirical distribution well after log-transformation, suggesting the presence of two independent log-normally distributed populations for Cu, As, Cd, and Pb. The geopmetric means of the two populations were （23.35± 6.39） mg/kg and （95.84± 38.73） mg/kg for Cu, （9.35±2.20） mg/kg and （23.67±6.16） mg/kg for As, （0.1208±0.0334） mg/kg and （0.3548±0.2344） mg/kg for Cd, （20.07±6.07） mg/kg and （82.55±39.33） mg/kg for Pb, respectively. The four heavy metals all could be divided into low value group and high value group. Heavy metals showed obvious bimodal distribution, the reason could be explained from a statistical point and may be complicated based on the spatial distribution of the two groups.
出处
《中国农学通报》
CSCD
2012年第35期233-238,共6页
Chinese Agricultural Science Bulletin
基金
国家自然科学基金重点项目"高集约化农区土地利用系统过程模拟及其环境风险控制"(41130526)
关键词
北京市
耕作土壤
重金属
双峰分布
Beijing
cultivated soil
heavy metals
bimodal distribution
