Assessment of Heavy Metal Pollution and Tracing Sources by Pb & Sr Isotope in the Soil Profile of Woodland in Quanzhou

Abstract

The contents of 8 heavy metal elements (Sr, Ni, Fe, Cr, Cu, Mn, Pb, Zn) and the lead & strontium isotope composition of soil profile of woodland in Quanzhou city were analyzed by AAS and ICP-MS, respectively. A modified BCR four-step sequential extraction procedure was carried out to obtain the speciation fractionation of heavy metals in the soil profile from 4 stations. The results of the heavy metal elements and the speciation fractionation of heavy metals in the soil profile showed that the heavy metal pollution in the woodland in Quanzhou was relatively light, and the main pollution factor was Sr. The non-residue state of Pb was the highest, leading to the highest activity. The result of Nemero comprehensive pollution index showed that Sr in the depth of 0-60 cm was at heavy pollution level. The results of the RSP showed that the activity of Pb was the highest. The results of EF showed that Pb, Sr, Mn and Zn had exogenous sources. Factor analysis showed that the main sources of heavy metals were the compound pollution of agricultural activities, natural resources, and the vehicle exhaust. Composition of Pb isotopic ratios showed that, Pb in soil profile of woodland in Quanzhou was from vehicle exhaust and parent material. The contribution rates of the two sources in the soil profile were calculated by using the two-mixed model. The contribution rates of parent material and vehicle exhaust were 85.14%(62.53%-98.36%) and 14.86%(1.640%-37.47%) on average, respectively. Strontium isotope tracing results showed that the main sources of strontium were also vehicle exhaust and parent material. Coupling both Pb and Sr isotope ratios agreed with the above mentioned results.