Study on heavy metals' influence on buried cultural relics in soil of an archaeological site

The protection of cultural relics in a chariot pit in the ancient ruins has become an important issue. In order to study the spatial distribution, speciation of heavy metals in soil at a cemetery where an ancient chariot was buried and the influence heavy metals have had on the cultural relics. Heavy metals in soil samples surrounding the cultural relic were analyzed via atomic absorption spectrometry (AAS) using a wet digestion method combined with a three-step sequential extraction procedure. Results for seven heavy metals (Cu, Pb, Zn, Cr, Fe, Mn and Sn) and the speciation of six heavy metals (Cu, Pb, Zn, Cr, Fe and Mn) indicated that their contents exceeded local soil background values, indicating that the soil around the site had been contaminated to a certain degree. Analysis of their speciation showed that Mn mainly existed in the form of a reducible fraction in the soil, while the other elements were mainly in the form of a residual fraction. Correlation analysis showed that, except for the HOAc soluble fraction, a significant positive correlation existed between the content of the different forms and their total amounts. Heavy metals present in the soil surrounding the ancient relic predominantly influence the relic due to their related chemical reactions. In particular, copper and iron have a significant influence on corrosion of the cultural relics in this chariot pit.