Ecotoxicity Of Heavy Metals On Plant Seeds In Soils With Different Land Use And Managements

Soil quality is profoundly influenced by land use and soil management practices. Higher plant is a fundamental component of soil ecosystem, whose growth status can be used as sensitive indications to assess the differences of soil quality. In the present study seeds and indicators that are sensitive to heavy metals are screened through comparing the effects of heavy metals on germination rate, root elongation and stem and leaf elongation inhibition rate of ryegrass. The ecotoxicity were distinguished in different soils according to IC50of heavy metals to elongation inhibition rate of root and stem leaf of ryegrass growing in different soils. The influencing factors of the ecotoxicity of heavy metals are also explored in soil through the soil properties and concentrations of soluble heavy metals. The aim of this study is to offer scientific foundation for land management. The main results are described as follows:(1) The elongation inhibition rate of root and steam and leaf of ryegrass can reflect concentration change of heavy metal in aqueous solution and soils. The length of root and steam leaf of ryegrass is longest, and it has good repeatability, so this study chooses the elongation inhibition rate of root and steam and leaf of ryegrass as the sensitive indicators for the soil experiment.(2) The toxicity of heavy metals to plant in soils is various as the difference of land use and soil management practices. The toxicity of heavy metals in paddy field soil are significantly less than that in other soils of the same region. The toxicity of heavy metals to plant in long-term unattended tea garden soil of Changde is significantly higher than that in other soils of the area, and the root, stem and leaf of Ryegrass cultivated in this soil is the shortest. The toxicity of cadmium to ryegrass in upland soil of Xianning is strongest than that in other soils of the same region. The heavy metal toxicity to plant in dry land soil which is changed from paddy soil is significantly greater than that in paddy soil of Changde.(3) The concentration of soluble speciation of heavy metals is various in different land use and management practices soils. On the same applied dose, the concentration of soluble speciation of heavy metals in two years greenhouse and paddy soil is less than that in other soils. The concentration of soluble speciation of Zn and Cd is less than that of Pb. The elongation inhibition rate of ryegrass root, steam and leaf can reflect concentration change of soluble speciation of heavy metal availably. The IC50of the elongation inhibition rate of soluble speciation of Cd and Zn extracted from a7-day incubation soil is significantly higher than that of solution, and the result of Pb is inverse.(4) The soils physico-chemical properties is various in different land use and management practices soils. The pH value of paddy fields is significantly higher than that of other soils in the same area. The soil pH value, total potassium, total phosphorus content of Changde soils is slightly lower than those of Xianning. The pH of Vegetable land and vegetable greenhouse soil is nearly neutral, and the total phosphorus and K in those soils is significantly higher than that in the rest soils. Soil pH is positive correlation with IC50. The concentrations of Pb, Cd, Zn in the soils in this study are not exceed the standard. The concentrations of Pb, Cd, Zn in the vegetable production base soils is significantly higher than that in other soils.Overall, the soils physico-chemical properties, the toxicity of heavy metals in soils and the concentration of soluble speciation of heavy metals have been affected by land use and management practices on soils. The elongation inhibition rate of ryegrass root, steam and leaf can distinguish different land use and management practiced on soils sensitively, and its IC50is positive correlation with the soil physico-chemical properties.