基于^(13)C-NMR偶极去相技术的有机肥料中有机组分特征研究

Structures of components in different organic fertilizers analyzed through ^(13)C-NMR dipolar dephasing technology

【目的】在固体13C-NMR的交叉极化魔角旋转全边带抑制(cross polarization/magic angle spinning/total suppression of sidebands,CP/MAS/TOSS)技术得到的谱图中,质子碳与非质子碳的信号重叠。偶极去相(dipolar dephasing,DD)技术利用13C-1H异核耦合作用大小的差异,区分与不同质子结合的13C核基团。本研究基于DD技术探讨有机肥料中碳结构特征。【方法】供试有机肥料样品包括3种秸秆(小麦秸秆、玉米秸秆、水稻秸秆)、3种粪肥(鸡粪、牛粪、猪粪)和3种腐植酸肥(腐植酸铵、腐植酸钠、腐植酸钾)样品,利用13C-NMR谱的CP/MAS/TOSS结合DD技术,测定了不同来源的有机肥料样品图谱,比较其碳分布比例。【结果】秸秆和粪肥样品中烷氧碳组分较多,占鉴定出所有碳组分的比例分别为55%和31%~37%,非质子化的烷氧碳占比不到3%;秸秆、猪粪样品中非质子芳香碳占3%~4%,鸡粪和牛粪样品中非质子芳香碳分别占15%和11%,较秸秆和猪粪样品含有更多的非质子化芳香族化合物。粪肥和秸秆样品中甲氧基碳占比低于烷基氮。腐植酸样品以芳香碳、羧基碳和酰胺基碳为主,羧基碳和酰胺基碳占到12%~16%,总芳香族碳占48%~72%,非质子芳香碳占25%~37%,表明腐植酸芳香骨架上可能存在较多取代。【结论】基于CP/TOSS结合DD技术(偶极相移延时时间设置为40μs)分析结果发现,鸡粪和牛粪中非质子芳香碳占比高于猪粪和秸秆;腐植酸肥芳香族碳比例高于粪肥和秸秆,尤其是非质子芳香碳占比较高,表明腐植酸肥芳香化程度高于粪肥和秸秆。

【Objectives】Solid-state ^(13)C-NMR techniques can be used to qualitatively and quantitatively characterize organic functional groups.Cross polarization/magic angle spinning/total suppression of sidebands(CP/MAS/TOSS)technique provides limited information on carbon functional groups.Dipolar dephasing(DD)is a spectral editing technique of solid ^(13)C-NMR,which is used to distinguish protonated and non-protonated carbon or mobile and rigid components in organic compounds based on ^(13)C-1H heteronuclear dipole coupling with specific dephasing delay time(TD).The objective of this study is to obtain more information on carbon functional groups in organic fertilizer by DD technique.【Methods】The organic fertilizer samples included 3 kinds of straw(wheat straw,corn straw,rice straw),3 kinds of manure(chicken manure,cow manure,pig manure)and 3 kinds of humic acid fertilizer(ammonium humate,sodium humate,potassium humate)samples.The spectra of organic fertilizer samples from different sources were determined by CP/MAS/TOSS conpined with DD technology,and the carbon distribution ratios were compared.【Results】O-alkyl C of cellulose origin are dominant in straw and manure samples,accounting for 55%and 31%-37%of the total organic carbon,respectively,and the proportion of non-protonated O-alkyl carbon did not exceed 3%in either straw or manure.Manure had more non-protonated fatty and aromatic carbon than straws,the proportions of non-protonated aromatic carbon in chicken manure and cow manure were 15%and 11%,respectively,while that in straws and swine manure was as low as 3%-4%.The percentage of methoxycarbon in manures and straws was lower than the percentage of alkyl nitrogen.Aromatic,carboxyl and amide carbon were the highest in humic matter samples,with 48%to 72%of aromatic carbon and no less than 12%of carboxyl or amide carbon,non-protonated aromatic carbons in humic matter samples account for 25%to 37%,indicating that there may be more substitutions of aromatic skeleton in humic matter fertilizers.【Conclusions】The DD combined with CP technique with 40µs delay time(TD)can be used to identify protonated and non-protonated carbon or mobile and rigid components in organic fertilizers and to study the characteristics of carbon functional groups in straw,manure and humic matter fertilizers.It is suggested that the aromaticity of humic acid fertilizers is much higher than that of manures and straws.