Field investigations were conducted to measure subsoil trace element content and factors influencing content in an intensive periurban market garden in Chenggong County, Yunnan Province, South-West China. The area was divided into three different geomorphological units： specifically, mountain （M）, transition （T） and lacustrine （L）. Mean trace element content in subsoil were determined for Pb （58.2 mg/kg）, Cd （0.89 mg/kg）, Cu （129.2 mg/kg）, and Zn （97.0 mg/kg）. Strong significant relationships between trace element content in topsoil and subsoil were observed. Both Pb and Zn were accumulated in topsoil （RTS （ratio of mean trace element in topsoil to subsoil） of Pb and Zn ≥1.0） and Cd and Cu in subsoil （RTS of Cd and Cu≤1.0）. Subsoil trace element content was related to relief, stoniness, soil color, clay content, and cation exchange capacity. Except for 7.5 YR （yellow-red） color, trace element content increased with color intensity from brown to reddish brown. Significant positive relationships were observed between Fe content and that of Pb and Cu. Trace element content in mountain unit subsoil was higher than in transition and lacustrine units （M 〉 T 〉 L）, except for Cu （T 〉 M 〉 L）. Mean trace element content in calcareous subsoil was higher than in sandstone and shale. Mean trace element content in clay texture subsoil was higher than in sandy and sandy loam subsoil, and higher Cu and Zn content in subsoil with few mottles. It is possible to model Pb, Cd, Cu, and Zn distribution in subsoil physico-chemical characteristics to help improve agricultural practice.
Yanqun zuLaurent BockChristian SchvartzGilles ColinetYuan Li
This paper studied the relationship between heavy metal concentrations of herbaceous plants and soils at four Pb-Zn mining sites in Yunnan,China.50 herbaceous plant samples of 9 plant species from 4 families and 50 soil samples were collected and then ana1yzed for the tota1 concentrations of Pb,Cd,and Zn.The results showed that the average concentrations of Pb,Cd,and Zn in soil samples were 3772.83,168.81,and 5385.65 mg/kg,respectively.The average concentrations of Pb,Cd,and Zn were 395.68,28.14,and 1664.20 mg/kg in the shoots,and 924.12,57.25,and 1778.75 mg/kg in the roots,respectively.Heterospecific plants at the same site and conspecific plants at various sites had different average levels of Pb,Cd,and Zn,both in the shoots and the roots.Enrichment coefficients of Pb,Cd,and Zn were greater than 1 in 2,3,and 9 herbaceous plant samples,respectively.Translocation factors of Pb,Cd,and Zn were greater than 1 in 10,17,and 25 herbaceous plant samples,respectively.In all 50 samples,the concentrations of Pb,Cd,and Zn between the shoots and the roots,the shoots,and the soils,and the roots and the soils had significant positive relationships.
