�ۺϿ�����Ʒ���ʼ����ȵ�Ӱ�죬����������������㱳��ֵ�ķ�����ʵ���о��������о����������治ͬ�����Ʒ�ı���ֵ����һ���IJ��졣��ʵ��ֵ�뱳��ֵ֮����Ϊ�������ӣ����� As�� Cr��Cu ����������²�������; Pb �������в�������; Zn �� Cd ������IJ�ͬλ�õĸ����̶ȱ仯�ϴ����в�������������㼰�ײ��жȸ������봫ͳ������ȣ��÷����ۺϿ��������Ⱥ���Ʒ���ʵ�Ӱ�죬���ҿ��Լ������ͬλ����Ʒ�ı���ֵ��ʹ�������������׼ȷ��

A method to calculate background values by using the clay minerals is proposed��which is taking the effects of sample features and particle sizes into consideration�� The results show that there is certain difference among background values of heavy metals from samples in different depths�� The ratio of measured and calculated value is defined as the enrichment factor��and As��Cr and Cu are found to be enriched weakly in the middle- lower of the section�� Pb is enriched in the middle of the section�� While the enrichment factors of Zn and Cd change great- ly in different depths with significant enrichment in the middle section and moderately enrichment in the surface and bottom�� Compared with traditional method��the influence of granularity and sample characteristics are considered in this method�� And the background values of heavy metals in different depths can be calculated��which makes the e- valuated results more precise��