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[Objective] The present paper aimed to provide a reference basis for the safe production in tobacco fields with medium risk of Cd pollution and remediation, the uptake of Cd by tobacco and its distribution pattern in the whole plant were studied. [Method] The tobacco planting soil with medium risk of Cd pollution was selected for pot experiments to explore the remediation potential of 5 tobacco varieties for Cd in the contaminated soil and safety production about of tobacco. [Result] The concentrations of Cd（1.510-2.110 mg/kg) in 5 tobacco varieties were far less than the limit value of Cd（5.0 mg/kg) in Guizhou tobacco leaves. The order of Cd concentration of 5 tobacco varieties was as follows: Guiyan 8 > Yunyan 87 > CF225 > Nanjiang 3 > Bi’na 1.The Cd concerntration of Guiyan 8 was significantly higher than others. There were no significant difference between Bi’na 1 and Nanjiang 3, and they were significantly lower than others. All of 5 tobacco varieties had strong enrichment ability for Cd（127.695%-204.549%), and the order of enrichment ability was as follows: Bi’na 1>Yunyan 87>CF228>Guiyan 8>Nanjiang 3. The accumulation of Cd in Bi’na 1 had 583.102 μg/plant and the remediation efficiency of Cd in soil was 4.113%, more than 4 other tobacco varieties（2.269%-3.262%). The Cd of Bi’na 1 was mainly stored in the unusable parts such as roots, stems and leaf veins in the tobacco. The distribution rate of Cd in leaves of Bi’na 1 was the lowest with 41.03% concentration, which was lower than that of other tobaccos（above 50%). Bi’na 1 reduced the adverse factors（Cd concentration and distribution rate) in the tobacco production. [Conclusion] Among 5 tobacco varieties, Bi’na maximum accumulation amount of Cd, which mainly exists in unusable part, including root, stalk, leave vein, etc. Compared with other four tobacco varieties, Bi’na 1 reduces the disadvantages during tobacco production. Hence, Bi’na 1 has the potential for safe utilization and restoration of tobacco field medium-polluted by Cd. [ABSTRACT FROM AUTHOR]

[Objective] In order to understand the content characteristics and ecological risk of heavy metals in agricultural soils in small-scale areas of karst regions, the present paper provides reference for the utilization of land function and the protection of cultivated soil environment. [Method] A total of 27 sites were laid on soil on agricultural land in the southwestern of Guizhou Province, samples of surface soil ( 0 - 20) cm were collected, and 8 heavy metal elements such as pH and Cd, Hg, As, Pb, Cr, Cu, Zn and Ni were analyzed and determined. The 'Soil Environmental Quality-Soil Pollution Risk Control Standard for Agricultural Land' (GB15618 - 2018) was used as the evaluation criteria to analyze its distribution characteristics, ecological risks and sources. [Result] The results showed that the soil pH in the study area was 5. 46 to 8. 07, and the average contents of heavy metals Zn, Cr, Pb, Ni, As, Cu, Cd and Hg were 154. 24, 153. 71, 64. 25, 61. 76, 50. 38, 49. 86, 0. 41 and 64. 25 mg/kg, respectively. The soil pollution index of agricultural land in the study area was 1. 68 and 1. 38, respectively. The hazard index (IR) value of 8 kinds of heavy metals was 69. 00, which was less than the limit of ecological hazard (IR = 150) . Cd and Pb, Hg and As, Cu, Zn, Ni, As and Cu, Zn, Ni, Cr, Cr and Cu, Zn, Ni, Zn and Ni have homology respectively, and there is compound pollution. The results of the main component analysis show that As, Hg, Cr, Cu, Zn, Ni have a higher load in the first main component, the variance contribution rate is 57. 565%, the content is mainly caused by the long-term application of heavy metal fertilizer; Cd and Pb have higher load in the second principal component, and their variance contribution rate is 80. 277%. The higher content is mainly due to the higher content in the parent material. [Conclusion] The soil pH of agricultural land in the study area is 5. 46 - 8. 07 which has been polluted by As and Cd to different degrees. Cr and Ni pollution is still clean range; Hg, Pb, Cu and Zn are in the clean range. The pollution level is slight ecological hazard [ABSTRACT FROM AUTHOR]

[Objective] The present paper aimed to provide the scientific basis for rational land-use planning, soil resources conservation and pollution-free agricultural development in Luodian County, Guizhou. [Method] The effects of five typical land-use patterns (forestland, natural grassland, artificial grassland, cropland and abandoned farmland) on content and environment contamination of Cd, Cr, Pb, Ni, Hg and As in topsoil were evaluated by Nemerow comprehensive index, single-factor contamination index and Hakanson potential ecological hazard methods. [Result] The content of 6 heavy metals in topsoil was Cr > Pb > Ni > As > Cd > Hg and lower than the contamination background value of heavy metals in Guizhou overall. The topsoil Cd content was the highest in abandoned farmland and lowest in forestland. The topsoil Cr content was the highest in abandoned farmland and lowest in natural grassland. The topsoil Pb and Hg content was the highest in cropland and lowest in forestland. The topsoil Ni content was the highest in artificial grassland and lowest in natural grassland. The topsoil As content was the highest in natural grassland and lowest in cropland. The topsoil Cd, C.r, Pb and Hg content was high relatively and greatly influenced by human activity. Topsoil Cr had the same source as Ni, Hg and As. The topsoil As content was closely related to soil pH. The topsoil Cd and Cr content was closely related to soil cation exchange capacity (CEC) . The topsoil Pb, Hg and As content was closely related to soil organic matter (SOM). [Conclusion] Six heavy metals in topsoil do not cause soil contamination. The single-factor contamination index and potential ecological hazard index both are at the clean level. The pollution-free agriculture can be vigorously developed according to local soil nutrient, soil fertility and land-use pattern in Luodian County, Guizhou. [ABSTRACT FROM AUTHOR]