贵阳市乌当区不同母质发育的土壤理化性质和重金属含量差异研究

Change of Physical-Chemical Properties and Heavy Mental Element in Soil from Different Parent Material/Rock

在贵阳市乌当区采集了9种母质(岩)上发育的土壤样品763个,分别测定了土壤的主要理化性质和主要重金属元素含量,通过对比分析表明不同母质(岩)发育的土壤理化性质和重金属含量都具有很大的差异。土壤理化性质的差异性主要表现为:石灰岩、红色粘土、老风化壳和页岩发育的土壤质地粘重,砂岩发育的土壤质地较轻,钙质紫色砂页岩、白云岩、砂页岩和河流冲积物发育的土壤质地适中;石灰岩、白云岩和钙质紫色砂页岩发育的土壤pH值为中性至微碱性,河流冲积物发育的土壤pH值为中性,其余5种母质(岩)发育的土壤pH值为酸性至强酸性;白云岩、钙质紫色砂页岩和河流冲积物发育的土壤有机质含量较高,而砂岩发育的土壤有机质含量较低,其余5种母质(岩)发育的土壤有机质含量介于二者之间;河流冲积物、石灰岩、白云岩和钙质紫色砂页岩等发育的土壤CEC较高,而砂岩发育的土壤CEC较低,其余4种母质(岩)发育的土壤CEC介于它们之间。土壤重金属含量差异性表现为:钙质紫色砂页岩、石灰岩、河流冲积物等发育的土壤中镉、铬、汞的含量较高,而红色粘土、河流冲积物和石灰岩等发育的土壤中铅和砷含量较高,砂岩发育的土壤中5种重金属元素的含量均为最低,其余母质(岩)发育的土壤中5种重金属元素的含量均介于上述之间。通过相关性分析结果表明:研究区域内土壤重金属镉、铬、汞、铅、砷的含量差异主要是由于成土母质(岩)的差异性所致,土壤理化性质的变化则是影响土壤重金属含量的次要因素。

After the collection of 763 soil samples developed from 9 types of parent material/rock, i.e. dolomite, limestone, calcareous purple sandy shale, shale, sandstone, red clay, old mantlerock, fluvial sediment and sandy shale, from Wudang district of Guiyang city in Guizhou province, where the karstic feature is well developed, physical-chemical propertiec and heavy metal element contents of these soils were analyzed. Huge differences between each of the soils were found through comparing the soils developed from different types of parent material/rock. The differentiae in physical-chemical properties of these soils manifest that. soil textures developed from limestone, red clay, old mantle rock and shale are heavy; soil texture developed from sandstone is light; soil textures developed from the rest 4 types of parent material/rock are between them. The pH of the soils developed from limestone, calcareous purple sandy shale and dolomite is neutral or mild alkaline; the pH of the soils developed from fluvial sediment is neutral; the pH of the soils developed from other types of parent material/rock is acidic. The soils developed from calcareous purple sandy shale, dolomite and the fluvial sediment have more organ- ic matter, however, organic matter content in the soil developed from sandstone is lowe,and organic matter content in the soils developed from the rest 5 types of parent material/rock is between them. CEC in the soils developed from fluvial sediment, limestone, dolomite and calcareous purple sandy shale is higher; CEC in the soils developed from sandstone is lower; CEC in the soils developed from the rest 4 types of parent material/rock are between them. The differentiae in heavy metal elements contents of these soils manifest that. the contents of cadmium, chromium, hydrargyrum is higher in the soils developed from calcareous purple sandy shale, limestone and fluvial sediment;the contents of plumbum and arsenic is higher in the soils developed from red clay, fluvial sediment and limestone; the contents of the 5 types of heavy metal elements are the lowest in the soil developed from sandstone; the contents of the 5 types of heavy metals in the soils developed from the rest parent material/rock is between the above mentioned quantity. The results of correlation analyses indicate： cadmium, chromium, hydrargyrum, plumbum and arsenic contents are caused by the differentiae of soil-forming mother material/rock in the investigating area. The type of parent material/rock is the principal factor that affect the heavy metal contents in the soils,and the changes of physical-chemical properties of soil are the minor factors.