| Qixiashan lead-zinc deposit in Nanjing is one of the largest lead-zinc deposits in East China, which has been explored more than 50 years. With the deepening of its mining activities, there was a strong impact on the environment. Therefore, in order to reveal the characteristics of heavy metal contamination and provide a scientific basis to remediation, the farmland soils surrounding the Qixashan Pb-Zn mine have been studied. Applying speciation, isotope and micro-analysis techniques, combined with soil mineralogical analysis, the characteristics of heavy metals in soils, the pollution sources, and the migration and transformation of pollutants have been studied on the basis of pollution evaluation in the area.Due to the flat terrain of study area, top soils (0-20cm) of mining area and four farmlands surrounding the mine were sampled using quincunx method, and soil profiles with two meters depth were also sampled stepwise. A total of 354 soil samples were collected. Furthermore, in order to study the pollution sources and migration of pollutants, nine samples of dry deposition about three months were collected using cylinder around the mine, and five dust samples from exhaust pipes of motor vehicles in Qixiashan area and fifteen ores were sampled as well.Those technologies were applied to analyze the pollution characteristics of heavy metals in farmland soil around the mine, such as EDXRF, ICP-MS, lead isotope, separation and identification of heavy minerals from soil, and micro-analysis of minerals. There were several results from analyses. Firstly, the main pollution heavy elements were Pb, As, Cd and Zn in Qixiashan lead-zinc mining area and farmlands around the mine of Nanjing, and multi-factor integrated pollution evaluation showed that the degree of mining area and No.1, 2, and 3 farmlands was heavy while No.4 farmland was polluted moderately. Secondly, soil profile analysis showed that the heavy elements concentration of Pb, As and Cu in the underground soils of 1.15m depth from No.4 farmland was abnormally high, and the environmental conditions of weak oxidation and acid accelerated migration of heavy metals in the No.4 farmland. Thirdly, the concentration of Pb, Zn and Cd reducible fraction and Zn, Cd acid-soluble fraction was very high, which suggested that heavy metals of farmland soil wound affect environment seriously on the acidic-reductive condition, but the actual soil condition (pH = 6.99, Eh = 1.3mV) may reduce the impact. Fourthly, pollution sources of farmlands came from the mine, and atmospheric deposition was an important way to transport pollutants. Furthermore, mine can provide many heavy metals with environment from main and trace element analyses of main ores of mine; some minerals (galena, sphalerite and pyrite) which were main ores in the mine were also detected in farmland soils; phenomenon of oxidation from galena to cerusite was detected as well, as a result, lead ion can disperse into environmental easily. Thus, in th angle of minerlogy, it also revealed that pollution sources of farmlands came from the mine, and oxidation was an important way to help heavy metals disperse into soil from minerals.
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