Morphological Analysis of Elements in Soils Using Mechanical Shaking Extraction and Ultrasonic Vibration Extraction

Two methods of mechanical shaking extraction and ultrasonic vibration extraction have been tested for chemical morphological analysis of Cu, Pb, Zn, Co, Ni, Cr, Cd, Mn, As, Sb, Hg and Se in soil samples. Extraction time by ultrasonic vibration extraction has been studied in detail, and the precision and accuracy were compared between mechanical shaking extraction and ultrasonic vibration extraction. The results indicate that ultrasonic extraction technology can greatly reduced extraction time to 3.2 h for elements that characterize ion exchange bond phase (contains a water-soluble state), carbonate bond phase, humic acid bond phase and iron manganese oxides bond. Efficiency of utrasonic vibration extraction was 5 times that of mechanical shaking extraction. The precision and accuracy (relative errors between the sum of elements content in every phase and total contents in samples) of ultrasonic vibration extraction were RSD 3.1%-34.8% (n=12) and 0.34%-11.85%, respectively, which were superior to mechanical shaking extraction. Accuracy and precision meet the requirements of the China multitarget ecosystem geochemical survey "China Geological Survey Bureau Geological Investigation Technology Standard" (DD 2005-03) for chemical morphological analysis technology. Ultrasonic extraction conditions are easier to handle and control, also the method is simple, fast, convenient and suitable for large numbers of samples analysis. Ultrasonic extraction has been used to analyse ecological geochemical surveys for tens of thousands of samples. This method has been included in the geological survey technical standards of China Geological Survey in DD 2005-03, and specified as the standard method for soil samples analysis in multitarget regional geochemical surveys by the China Geological Survey Bureau.