摘要
采用原状土壤水稳性团聚体分离方法提取不同粒径的土壤颗粒 ,测定其有机碳及重金属元素 Pb、Cd的含量 ,研究了退化红壤在植被恢复下表层 (0～ 1 0 cm和 1 0～ 2 0 cm)土壤颗粒中有机碳与重金属分布及其关系。这些土壤颗粒中有机碳和重金属元素 Pb、Cd的含量范围分别介于 7.5～ 1 5 g/ kg,1 1～ 2 0 mg/ kg和 2 0～ 70μg/ kg,且粒组间有显著差异。尽管所测组分的含量以 <0 .0 0 2 mm粒组中最高 ,但 2～ 0 .2 5 mm的粒组占其总量的 5 0 %左右 ,其次约 2 0 %存在于 0 .2 5～0 .0 2 mm粒组中。以土壤粒组中分量而言 ,有机碳和所测的重金属元素间有密切的依存关系。与荒地相比 ,植被恢复措施降低了各土层 2～ 0 .2 5 mm粒组中 Pb的含量和分量 ,但提高了 0～ 1 0 cm土层 Cd的含量和分量。在所研究的几种处理中 ,玉米 -包菜处理显著地促进了有机碳和重金属在各颗粒粒组中的均衡分布。因此 ,退化红壤植被恢复措施改变了土壤颗粒中有机碳和重金属的分布 ,因而可能影响着土壤环境中有机碳和重金属的形态及其活性。
Degradation of farmland Red Earth is one of the severe problems facing agriculture in South China.Since 1990's,agronomical measures such as vegetation recoveries have been taken for its mitigation.In previous studies,role of vegetation recoveries on rapid rebuilding of soil organic carbon(SOC) and micro\|aggregation has been debated.The objectivity of present study is to describe the redistribution of SOC and heavy metals of human risk concerns and partitioning in the soil particle size fractions as affected by the vegetation recovery practices. The samples were collected at the Grass Extension Station of Jiangxi Province,10 km northwest to Nanchang City.Being typical in central Jiangxi,the soil was Typical Udsiallisols (Chinese Soil Taxonomical Classification,1999)derived from old Quaternary deposits on the rolling slopes.The treatment plots were:A,rotation of corn and cabbage(for 4a);B,continuous white clover(for 15a);C,continuous orchard grass(for 15a) and rotation of Chinese Lespedeze\|Sudan grass(for 3a after 15a grass)(Table 1).A mixed sample of 5 undisturbed sub\|samples was collected randomly in each plot and in 0～10cm,10～20cm respectively. The undisturbed soil clods were dispersed in water using the ultrasonic energy at 21 5Hz and 300mA.Soil particles in size of >2mm,2～0 25mm were separated by wet sieving,those in size of 0 25～0.02mm and 0 02～0 002mm by sedimentation and siphon,and those in size of <0 002mm by centrifuging.The contents of organic carbon,Pb and Cd contents in the particle separates were determined by wet combustion and HF\|HNO 3\|HClO 4 digestion.The concentration of the metals were measured by AAS with the internal standard control. Prominent variation was found in the content of SOC and Pb and Cd contents among the soil particle fractions,with highest contents in the fraction<0 002mm(Table 2,Fig.1).The fractions of 2～0 25mm and 0 25～0 02mm generally possessed 50% and 20% of the total amount of the analyzed components respectively.Significantly positive correlation was found between the portion of Pb or Cd and that of SOC in the soil particle fractions(Fig.2).Compared with that in the uncultivated soil,the recovery treatments enhanced accumulation of SOC and decreased of Pb and Cd in the predominant particle fraction of 2～0 25mm,whereas elevated Cd level in the 0~10cm layer(Table 4).Under the corn\|cabbage rotation,no remarkable variation was shown of SOC and heavy metals in the soil particle fractions as compared to that under the other treatments.Therefore,the vegetation recovery measures had not only beneficial effects on SOC sequestration(Li, et al .2001),but also affected the distribution pattern of both SOC and heavy metals in soil particle fractions.However,the effects of these measures on bioavailability of the measured components in the particle fractions remain to be determined.
出处
《生态学报》
CAS
CSCD
北大核心
2001年第11期1769-1774,共6页
Acta Ecologica Sinica
基金
科技部重点科技规划项目 (G1 9990 1 1 80 8-3 )
国家教育部博士点专项研究基金资助项目
