碳酸钙对石灰性土壤颗粒组成测定的影响

采取化学分析和Tessier连续提取法,对西宁市6个功能区城市土壤重金属Cu、Zn、Pb和Cd的含量及形态进行研究。结果表明:西宁市各功能区土壤的Cu、Zn、Pb和Cd的全量分别是全国土壤相应重金属几何平均值的1.9~5.2,1.9~6.9,0.8~4.0,7.4~11.1倍,4种重金属污染比较严重。6个功能区的重金属Cu、Zn、Pb和Cd含量进行差异显著性分析,结果是广场区Cu的含量与风景区的差异不显著(P>0.05),但与其他4个功能区差异显著(P<0.05);风景区与开发区差异显著(P<0.05),但与其他4个功能区差异不显著(P>0.05);开发区Zn的含量与商业区和居民区的差异显著(P<0.05),而其他各功能区间差异均不显著(P>0.05);各功能区Pb和Cd的含量均无显著差异(P>0.05)。研究土壤中重金属的化学形态有较大的差异,Cu以残渣态和有机结合态为主;Zn以残渣态和铁锰氧化物结合态为主;Pb和Cd以残渣态为主。Cu活性相对较高的土壤出现在风景区、矿冶区和居民区,Zn活性相对较高的土壤出现在风景区和广场区,Pb活性相对较高的土壤出现在风景区和居民区,Cd活性相对较高的土壤出现在矿冶区和开发区,研究土壤中4种重金属均具有一定的生物有效性和潜在的生态危害性。

Changes in Soil Particle-Size Distribution by Laser Diffraction Method as Affected by Calcium Carbonate in Calcareous Soils

Decalcification using hydrochloric acid is an important pretreatment in the process of the analysis of soil particle-size distribution from calcareous soil samples.Decalcification procedure is characterized by complex operations,time consuming and low accuracy.To analyze differences and convert relationships for soil particle-size distribution between decalcification and non-decalcification,368 soil samples were determined by the Mastersizer 2000 laser particle-size analyzer.Results showed that there was a difference in soil particle-size distribution between decalcification and non-decalcification.For coarse sand and clay contents,the samples of the ≤ 3% difference value accounted for 97.28% and 98.91%,respectively.For fine sand and silt contents,the samples of the ≤ 3% difference value accounted for 70.65% and 76.63%,respectively.The changes in soil particle-size distribution were mainly influenced by calcium carbonate contents.The correlation of soil particle-size distribution was very significant between decalcification and non-decalcification.The conversion equations of data between the two cases were established so that soil particle-size distribution by the decalcification method could be calculated using the data obtained by the non-decalcification one.