Soil Dioxin Contamination around Industrial Park

The industrial park is located on the north bank of the Yellow River in Ningxia Province. There are mountains behind the park, and the prevailing wind is from the northwest to the southeast. The industrial park was established in 2003 and covers an area of approximately 40 km². Because of the ready availability of electricity, land resources, and a dry climate suitable for electrolytic manganese production, a large electrolytic manganese production base was built in the industrial park. As mentioned above, an iron and steel smelter, a cement kiln, and a power plant were also built in the industrial park. Because the local area is rich in agricultural straw as a resource, it is used as fuel for power plants in the industrial park. In addition, chemical fertilizer plants, agricultural product processing plants, sulfuric acid plants, and new material manufacturing plants have also been built in the industrial park. To investigate the concentrations of PCBs, PCNs, and PCDD/Fs in the soil around the industrial park, 13 soil samples (P1–P13) were collected in June 2017 (Figure 1). For each sample, surface soil (0–10 cm depth) was collected with a clean stainless steel shovel, placed in a clean opaque bag, and the bag was then sealed. After collection, samples were transferred to the laboratory as soon as possible and stored in a refrigerator at −18 °C.
Sample P4 was collected near the iron and steel smelter, and samples P5, P6, P11, and P12 were collected downwind of the smelter. Samples P7 to P10 were collected downwind from the cement kiln, and close to the iron and steel smelter and biomass power plant. Samples P1, P2, and P3 were collected upwind of the iron and steel smelter, and distant from the biomass power plant and cement kiln. Samples P1, P2, and P8 were collected from the landscaped green area in the industrial park. The land used in the industrial park was mainly obtained by pushing mounds to fill gullies, so the soil of the landscaped green area in the industrial park was derived from the new soil excavated during the construction of the industrial park. All other samples were collected from the surrounding farmland. Corn was the main crop planted in the local area. A background soil sample (P14) was collected from farmland located 25 km away from the industrial park, where corn was also the main crop. Moreover, it was distant from any potential dioxin sources.