石灰性土壤有效硒浸提剂和浸提条件研究

Extractants and Optimum Extracting Conditions of Soil Available Selenium in Calcareous Soil

采用外源硒加入土壤中得到硒污染土壤,6种有效硒的浸提剂NaHCO3、KH2PO4、K2SO4、EDTA、AB-DTPA和DTPA+TEA+CaCl2的最佳浸提时间和土液比进行了筛选,并通过盆栽试验对所选择的土壤有效硒浸提剂进行生物学校验,以找出石灰性土壤有效硒提取适宜的浸提剂及其浸提条件。结果表明,NaHCO3、KH2PO4、K2SO4、EDTA、AB-DTPA和DTPA+TEA+CaCl26种浸提剂有效硒浸提量都随着浸提土液比的减小而增大,且随浸提时间的增长而增大。其中NaHCO3和KH2PO4最佳土液比为1/15,振荡时间90min;K2SO4和AB-DTPA的最佳土液比为1/15,振荡时间60min;EDTA和DTPA+TEA+CaCl2的最佳土液比则为1/20,振荡时间30min。6种浸提剂在各自最佳的提取条件下提取的土壤有效硒量与白菜地上部分硒含量达极显著正相关,但土壤有效硒的提取量以DTPA+TEA+CaCl2及K2SO4最少,只占KH2PO4、AB-DTPA及EDTA提取量的14%～48%,故不适用于作为石灰性土壤有效硒的提取剂。NaHCO3适用于土壤硒含量高于5mg·kg-1的石灰性土壤有效硒提取。KH2PO4、AB-DTPA及EDTA3种浸提剂既可提取土壤中水溶态硒,亦可提取部分的吸附态硒,提取硒数量较多,过程简单,重复性好,都可作为石灰性土壤有效硒提取的浸提剂。

The batch lab experiments were carried out to select optimum extractants and the corresponding extraction conditions for available selenium in calcareous soil. The pot trial was done by adding different amounts and types of selenium（ selenate and selenite ） to calcareous soil, and the correlation of extracted available selenium content in soils and total selenium content in plants were studied to further verify the selection. The results indicated that the extractable selenium amounts which extracted by six extraetants（ NaHCO3, KH2PO4, K2SO4, EDTA, ABDTPA and DTPA＋TEA＋CaCl2） were all increased with the ratio of soil to solution decreased from 1/5 to 1/20, and they also increased with the shaking time elongated from 30 min to 120 min. The optimum ratio of soil to solution and shaking time were 1/15 and 90 min for NaHCO3 and KH2PO4; 1/15 and 60 min for K2SO4 and AB-DTPA; 1/20 and 30 min for EDTA and DTPA＋TEA＋CaCl2, respectively. There was a significant correlation between available selenium contents in soil extracted by the six extractants under selected optimum extraction conditions and selenium absorption of plant. Selenium amounts that extracted by DTPA＋TEA＋CaCl2 and K2SO4 were minimum, which were only 14% to 48% amount of selenium were extracted by KH2PO4, AB-DTPA and EDTA. Among six tested extraetants, DTPA＋ TEA＋CaCl2 and K2SO4 were not suitable for available selenium extracting of calcareous soil, on the contrary, KH2PO4, EDTA and AB-DTPA were all good for available selenium extraction. NaHCO3 could be used as extraetant for available selenium only if selenium amount was above 5 mg·kg^-1 in calcareous soil.