摘要
土壤中的有机物对于斥水性的研究具有重要的作用,但是目前关于内蒙古草原土壤的研究主要集中在有机碳上,而对土壤中有机物种类的研究很少。选取内蒙古锡林浩特市南部的牧草土壤样品,使用溶剂超声萃取的方法,对土壤中的有机物进行了分析。结果发现,石油醚的粗提物最少,异丙醇/氨水(7∶3)的粗提物最多。粗提物经紫外、红外和GC-MS测定,结果表明用石油醚、异丙醇和甲醇作为萃取剂,得到的有机物主要为直链或环烃化合物,含量占总提取物的95%以上;氯仿及异丙醇/乙酸(7∶3)和异丙醇/氨水(7∶3)提取物除了含有直链或环烃化合物外,还含有酯、酰胺和甾类化合物,且甾类化合物在异丙醇/氨水提取物中含量相对最高。采用异丙醇/氨水对所有土壤样品进行萃取,发现NM1和NM7提取物中甾类化合物的含量较高,占总提取物的25%左右。异丙醇/氨水的粗取物用石油醚:乙酸乙酯(4∶1)作洗脱剂,经柱层析分离主要得到A、B两部分;经GC-MS测定、质谱图库检索表明A为甾酮类物质,B为不含氧的甾烯类或者甾醇类物质。
【Objective】Inner Mongolia grassland is not only one of the important meat and milk production areas of China,but also an important ecological barrier in North China. In recent decades,in addition to global climate warming and continuous drought,unreasonable use of the land resources has caused severe degradation of the grassland,and reduction of the soil＇s capacity of accommodating rain water. Consequently,the soil is becoming more and more water repellent. In order to find out causes of water repellency and to help to solve the problem,it is necessary to get to know exactly distribution,species and content of the soil organic matter in the grassland,and especially relationship of the organic compounds with soil water repellency,so as to facilitate monitoring and eliminating soil water repellency. The purpose of this paper is to establish a method for separation and purification of soil organic compounds in the grassland,to obtain some certain-structured organic matter,and to lay down some foundations for further studies on relationship of the organic compounds with soil water repellency.【Method】In this paper,soil samples were collected from the surface soil layer（0~5 cm）of a tract of forage grassland in the south of Xilinhot city,Inner Mongolia and petroleum ether,chloroform,isopropanol,methanol,isopropanol/acetic acid（7∶3）,isopropanol/ammonia（7∶3）,different in polarity were used as extraction agent for ultrasonic extraction of the soil samples. Crude extracts were tentatively identified with UV,IR and GC-MS,and then processed with column chromatography to get different species of organic compounds. 【Result】The following findings were obtained. The crude extract,using isopropanol/ammonia,isopropanol/acetic acid as extraction agents was quite large in quantity,while those using petroleum ether,chloroform,isopropanol and methanol as extraction agents was less. The extracts using different solvents differed in appearance,the crude extracts using petroleum ether,chloroform,and isopropanol appeared to be yellow;while those using isopropanol/acetic acid and isopropanol/ammonia,dark brown. The UV-Vis absorption wavelengths of all the crude extracts were concentrated in the range of 200~480 nm. The crude extracts,though using different extractants,were basically quite similar in infrared spectrum,but their chief absorption peak appeared separately at 2 960 cm^-1,2 920 cm^-1,2 850 cm^-1（C-H stretching vibration）,1 732 cm^-1（C‖O） 1 460 cm^-1 and 1 375 cm^-1（C-H,C-C bending vibration）. Besides a relatively weak absorption peak was observed in the vicinity of 1 667 cm^-1,in the IR spectra of the crude extract using methanol and isopropanol/ammonia and isopropanol/acetic acid,reflecting the existence of aromatic skeleton or amide associated with a C=O double bond. Comparison between the GC-MS of the crude extracts and the standard mass spectra reveals that hydrocarbons made up about 95% of the crude extract using petroleum ether,isopropanol or methanol extract,and only about 70% of the total extract using isotropanol/ammonia or isopropanol/acetic acid extracts,and both were dominated with C23 linear hydrocarbon. Steroid（mainly sitosterol）was only detected in the crude extracts using chloroform,isopropanol/ammonia and isopropanol/acetic acid. The crude extract using isopropanol/ammonia was further separated and purified with column chromatography,and then two portions of substances displaying Rf=0.56 and 0.21（A,B）（petroleum ether：ethyl acetate = 4∶1）,respectively,were obtained on the plate. In the GC-MS spectra,the retention time of the compound in Part A varied mainly in the range of 30~34 min,while that in Part B mainly in the range of 25~30 min.【Conclusion】The crude extract using petroleum ether,isopropanol or methanol as extractant was composed mainly of linear or cyclic hydrocarbons;and that using chloroform,isopropanol/acetic acid（7∶3）or isopropanol/ammonia（7∶3）mainly of esters,amides and steroids besides in addition to linear or cyclic hydrocarbons. The crude extract using isopropanol/ammonia（7∶3）was separated into Part A and Part B with column chromatography. Part A was identified as steroidal ketones,and Part B as oxygen-free sterenes or sterols with GC-MS and MS library search.
出处
《土壤学报》
CAS
CSCD
北大核心
2017年第6期1459-1470,共12页
Acta Pedologica Sinica
基金
国家自然科学基金项目(41471198)
国家重点基础研究发展计划(973计划)项目(2014CB138801)资助~~
