不同提取条件下红壤水稻土溶解有机碳的含量变化

SOLUBLE ORGANIC C CONTENT OF PADDY SOILS IN SUBTROPICAL CHINA IN RELATION TO EXTRACTION CONDITIONS

通过室内实验研究了不同提取条件对红壤水稻土溶解有机C量的影响.结果表明,浸提时样品的水分含量越高,溶解有机C量越大,特别是水分含量超过600g/kg时,变化的趋势更明显.水土比也对溶解有机C量有影响,随水土比增大,溶解有机C量升高,水土比＞2时,增加的趋势更显著.提取时间的长短对溶解有机C量影响不明显.不同的提取剂种类和浓度对溶解有机C量的影响显著,较高浓度的盐溶液对有机C的溶出作用明显,显著增加溶液中的有机C量.有鉴于此,为使研究结果可以比较,提取的方法应当统一,根据试验结果,认为在进行溶解有机C含量变化研究时,所采取的提取方法应该是:①采用鲜土:含水量在200～400 g/kg;②用去离子水作为提取剂;③提取时的水土比应为2:1;④振荡提取时间为30 min;⑤离心20 min(4000 r/min);⑥用0.45μm滤膜过滤;⑦滤液中有机C用TOC分析仪测定.

Laboratory analysis was conducted to investigate soluble organic C content of paddy soils in subtropical China in relation to extraction conditions. Results showed that the concentration of water-soluble organic carbon （WSOC） increased with soil moisture, which was more obvious in soil higher than 600 g/kg in moisture content. WSOC was positively and significantly related to water-soil ratio, especially when the water-ratio was over 2. WSOC was not influenced by duration of the extraction when it was not longer than 5 h. Type and concentration of the extraction reagents influenced significantly the soluble organic carbon contents in soils, indicating a higher concentration of extraction reagent would bring out a higher WSOC. Based on the above findings, it can be concluded that to keep experiment results comparable, it is advisable to adopt a uniform extraction method, that is, Ofresh soil samples, 200 - 400 g/kg in soil moisture content; ①deionized water as extraction reagent; ②water-ratio being 2; ③ shaking and extraction for 30 min;④centrifugation for 20 min （4000 r/min）; ⑤0.45 μm membrane for filtration; and ⑥TOC analyzer to determine organic carbon in filtrate.