山西临汾-运城盆地土壤中As含量的变化规律

通过对临汾-运城盆地表层和深层土壤中As含量变化规律的研究，发现表层土壤的As含量稍高于全国土壤的背景值，不同相态的含量差异较大。土壤pH、磁化率、有机质、粘粒含量等理化性质对不同形态的As有着不同程度的影响：研究区水溶态的As受土壤pH值的控制，腐殖质结合态的As与有机质呈明显的正相关关系，磁化率、粘粒含量与土壤As的含量都有明显的正相关关系。研究结果表明，As与Fe、Mn、Cu、Zn、Mg、K、F等元素的相关性非常显著，说明研究区表层土壤中的As主要是自然成因的。进一步的回归分析表明，土壤的As含量随着铁氧化物、氢氧化物和硫化物含量的增加而增加。研究区土壤As的纵向分布特点是中层多、上下层少，这可能与研究区As的污染状况、土壤的碱性环境、植物的吸收作用、磷肥的施用等因素有关。

Change of the arsenic content in soils of the Linfen-Yuncheng basin, Shanxi, China

Study of the change in As content in surface and deep-level soils in the Linfen-Yuncheng basin shows that the contents of arsenic and related elements in topsoils are slightly higher than the background values of soils nationwide and that there is appreciable difference in content of As with different phase states: the soluble and exchangeable fractions have low to undetectable arsenic contents (1.5%); Fe/Mn oxyhydroxide-bound As is the second largest fraction (10%) in tested soils; the organic fraction (10%) makes up a significant portion; and the residual fraction (60%) accounts for the largest portion. Some statistics methods, such as the correlation analysis and regression analysis, were used to study the spatial variability of arsenic in soils in relation to their influence factors. Physico-chemical properties, such as pH of soils, magnetic susceptibility, total organic carbon (TOC) and content of the clay size fraction, affect As with different phase states to different degrees: the water soluble fraction of As has a close relationship with pH values; TOC shows a distinct positive correlation with humus-bound As; both the magnetic susceptibility and content of the clay size fraction have a distinct positive correlation with the As content in soils. Results of the study show that As has a very significant correlation with Fe, Mg, Cu, Zn, Mg, K and F, indicating that As in topsoils in the study area is mainly of natural origin. Further regression analysis indicates that the As content in soils increases with increasing contents of iron oxide, hydroxide and sulfide. The As content in soils increases with depth: there are more As in the intermediate layer and less As in the upper and lower layer, which is likely to be related to such factors as the pollution of arsenic, alkaline soil condition, absorbability of plants and use of phosphate fertilizer in the study area.