Lead isotope to tracing soil heavy metal pollution and bioavailability research in Hanyuan, Sichuan, China

Abstract:

In order to ascertain the pollution status, existing forms and sources of heavy metal lead in Hanyuan soil, Sichuan Province, China. The content of Pb in soil was determined by inductively coupled plasma mass spectrometry (MC-ICP-MS), the existing forms of Pb in soil were determined by BCR, and the lead isotope composition in the samples was determined by MC-ICP-MS.

Soil samples include surface soil and profile soil. Surface soil samples are distributed along the Dadu River basin in Hanyuan County according to the serpentine method.

The results show that the average mass fraction of Pb in surface soils of Hanyuan was 478.09×10^-6, which was 15.94 times the background value of soil in Sichuan Province (30.00*10^-6). The natural end-member bedrock and ore ²⁰⁸Pb/²⁰⁷Pb ratio 2.444, 2.453, ²⁰⁶Pb/²⁰⁷Pb ratio 1.169, 1.160, anthropogenic end-member car exhaust, cement plant fly ash ratios of ²⁰⁸Pb/²⁰⁷Pb are 2.486, 2.501, ²⁰⁶Pb/²⁰⁷Pb are 1.184 and 1.197, while the ratios of ²⁰⁸Pb/²⁰⁷Pb and ²⁰⁶Pb/²⁰⁷Pb in surface soil are 2.448-2.491 and 1.154-1.193.

The content of heavy metal Pb in surface soil of Hanyuan area is 15.94 and 20.56 times higher than that of Sichuan Province and China respectively, indicating that the pollution of Pb in surface soil of Hanyuan area is serious.

The more serious the artificial disturbance in surface soil in Hanyuan area, the higher the proportion of the extractable state of the sample, and the higher the proportion of the residual state of the original and less disturbed soil. Moreover, most of the samples in Hanyuan area are mainly extractable state, which indicates that the source of lead in the study area is mainly man-made and has great potential harm to the environment.

The lead isotope composition of each end-member component in Hanyuan area is quite different. ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb in surface soil are close to anthropogenic automobile exhaust dust and cement plant dust, and the lead content in surface soil is negatively correlated with ²⁰⁶Pb/²⁰⁷Pb, that is, the higher the lead content, the more anthropogenic lead source, indicating that the pollution of heavy metal element Pb in the study area is mainly anthropogenic pollution.