To establish a rapid extraction method of chromium (VI) from soil which can be applied for field investigation, we studied the leaching behavior of chromium (VI) using four types of soil : Andosol, Gray lowland soil, Brown forest soil and Kanumatsuchi soil. After the four types of soil were mixed with K_2Cr_7O_4,chromium (VI) was extracted from the four types of soil with a solution of K_2HPO_4/KH_2PO_4,K_2SO_4,NH_4CH_3COO and deionized water, respectively. After using the batch extraction method, the concentration of chromium (VI) in K_2HPO_4/KH_2PO_4,K_2SO_4 solution reached 85% of the maximum extractioncon centration after 10 min of shaking, and they each reached 90% of maximum after 1h of shaking in each extracting solution and each soil type. The chromium (VI) concentration extracted from Kanumatsuchi soil with K_2HPO_4/KH_2PO_4 and K_2SO_4 solution reached the maximum after 2 to 4 h of shaking, and then the concentration decreased after 6 h of shaking (extraction). On the other hand, no decline in the chromium (VI) concentration was observed even after 16 h of shaking from Andosol, Gray lowland soil and Brown forest soil. Using the batch extraction method, the concentration of chromium (VI) in the extracted solution from any soil used in this study was higher in the K_2HPO_4/KH_2PO_4 and K_2SO_4 solution than that in the NH_4CH_3COO solution and deionized water. By using the column extraction method, the total chromium (VI) quantity extracted in the K_2HPO_4/KH_2PO_4,K_2SO_4 and NH_4CH_3COO solution was equal to that extracted by deionized water. The K_2HPO_4/KH_2PO_4 solution extracts chromium (VI) rapidly. However, K_2HPO_4/KH_2PO_4 solution is not an appropriate measurement of chromium (VI) for spectrophotometry in field investigations, because organic matter is extracted from the soil simultaneously, which colors the extracted solution and interferes with the measurement. Therefore the K_2SO_4 solution was considered to be the most suitable solution for the rapid extraction of chromium (VI). The extracted concentration of chromium (VI) by the K_2SO_4 solution was constant when the pH of 2×10^<-1> mol L^<-1> K_2SO_4 solution was within the range of 6.0 to 8.0 ; the concentration of K_2SO_4 solution in the range of 2×10^<-1>-5×10^<-1> mol L^<-1> did not affect the level of chromium (VI) extraction at pH7.0. In conclusion, K_2SO_4 solution (pH 6.0-8.0,2×10^<-1> mol L^<-1>) is appropriate for rapid extraction of chromium (VI) by the batch extraction method (10 min of shaking) in field investigations.
