| In order to identify the main sources and pollution degrees of heavy metals in farmland soil around the Tongshan mining area, 361 surface soil (0-20 cm) samples were collected and measured for the heavy metals Ag, Cu, Pb, Zn, Mo, Sb, Ba, As, and Hg. The source analysis and spatial distribution characteristics of the soil heavy metals in the study area were analyzed using the combination of a PMF model and IDW interpolation. Based on the traditional matter-element extension model, the Hakanson toxicity response coefficient and modified weight coefficient were introduced to evaluate the pollution level of heavy metals, and the evaluation results were compared with those from the Muller index (Igeo) and Nemerow comprehensive index (PN). The results showed that:① the mean values of ω(Ag), ω(Cu), ω(Pb), ω(Zn), ω(Mo), ω(Sb), ω(Ba), ω(As), and ω(Hg)were 0.05, 19.32, 23.34, 62.89, 0.97, 0.87, 542.56, 8.88, and 0.07 mg·kg-1, respectively. Zn and Hg were higher than the soil background value of Henan Province but lower than the soil pollution risk control value of agricultural land. The nine heavy metals in the soil of the study area mainly showed island and sheet distribution in space. ② The evaluation results of the matter-element extension model with a modified weight coefficient showed that only 6.37% of the topsoil in the study area was previously clean soil, 89.75% was still clean, 3.32% was slightly polluted, and 0.277% was heavily polluted, and Hg was the main polluting element. The evaluation results of the matter-element extension model with the modified weight coefficient were roughly the same as those of the Muller index and Nemerow index methods, indicating that the matter-element extension model with the modified weight coefficient could be used for the evaluation of soil heavy metal pollution, and the evaluation results were accurate and objective. ③ The heavy metals in the farmland soil around the Tongshan mining area mainly came from the mixed source of pesticide use and mining development (18.79%), the mixed source of agricultural activities and natural parent material (22.02%), the mixed source of fossil combustion release and agricultural activities (15.57%), the emission source of mining development (11.06%), and the mixed source of transportation, natural parent material, and mining development (32.51%). |
