HYDROGEOCHEMICAL CHARACTERISTICS AND HIGH LEAD GROUNDWATER FORMATION IN A VILLAGE OF SOUTHEAST CHINA

An outbreak of high-level lead in children's blood occurred in Zhuangnei Village, Kangmei Town, Nan'an City, Fujian Province, Southeast China, 2012. This study comprehensively uses groundwater hydrochemical characteristics analysis, soil Pb chemical form risk analysis and Pb isotope tracing techniques to systematically study the causes of high-lead groundwater and its influencing factors.

Fourteen groundwater samples were taken to clarify the groundwater chemical types to explain the chemical causes of groundwater by Shukalev Classification and Piper Three-line Diagram. The ionic coefficients were analyzed for the relationship between Pb concentration and major chemical. The weak acid environment and hydrodynamic conditions were analyzed for the influence of Pb migration and ion exchange intensity for Pb enrichment. Five surface and five parent soil samples were taken to analyze seven heavy metals content such as Pb, Cd, As, Cu, Cr, Zn and Ni, and the Cumulative Index method is used to the risk analysis of soil Pb. The form of Pb in soil samples analyzed by Tessier Continuous Extraction method, and the RSP method which based on Pb form is used to the risk analysis of soil Pb. Correlation analysis and Cluster analysis were used to analyze seven heavy metals content in soil and groundwater. According to the "fingerprint" characteristics of Pb isotope, nine samples including surface soil, deep soil, granite, dust fall, branches, leaves, vegetables, surface water and groundwater were taken to study whether the Pb in groundwater is the same as the source of Pb in soil, rocks, plants, and dust.

The results show that, the soil Pb content in the village is abnormal. The occurrence form is mainly composed of iron-manganese oxide bound state and organic binding state, and have strong migration ability. Under the action of acid rain and weakly acidic chemical type groundwater, the easily transporting form of Pb continuously migrates from soil to groundwater. However, the hydrodynamic conditions in the study area are not active. The main dynamic type of groundwater is infiltration-evaporation, which promotes the concentration and enrichment of Pb in groundwater, and finally forms high-lead groundwater.