Analysis of Heavy Metal Sources in Farmland Soil Downstream of Heap Leaching Field Based on APCS-MLR Model and UNMIX Model.

Abstract:

In order to explore the spatial distribution characteristics， pollution status and sources of heavy metals in farmland soil downstream of a heap leaching field， 152 soil samples were collected from 76 sampling points at 0.2 m and 0.5 m depths， and the contents of 8 metal elements such as Cu， Zn and Cr were determined. The pollution level was evaluated by single factor pollution index method and Nemerow pollution index method， and then the pollution sources were analyzed by principal component analysis， absolute principal component-multiple linear regression （APCS-MLR） model and UNMIX model， and verified by geostatistical analysis. The results showed that the average contents of Cr， Pb， As and Hg in the soil exceeded the soil background values in Yunnan Province， and the proportion of As content higher than the background value and the screening value exceeded 90% and 70%， respectively. The results of UNMIX model analysis showed that there were four main sources of heavy metal pollution. Source 1 is the mining development and traffic source， which contributed 65% and 56% to As and Pb， respectively. Source 2 is the source of agricultural activities， and the contribution rate to Cd was 91%. Source 3 is the natural source， and the contribution rates of Cu， Zn， Cr and Ni were 63%， 61%， 62% and 55%， respectively. Source 4 is the coal-fired source， which contributes 94% to Hg. The analytical results of APCS-MLR model were basically consistent with those of UNMIX model， but the natural parent material source was not identified alone. The above results can provide technical support for the precise implementation of farmland ecological environment management， and provide theoretical basis for mine pollution prevention and improvement of mining process.