Figure 45. Pyrolysis mass spectra of whole soil, soil humic fractions and extracted soil from the A1 horizon of a brown soil on granite (Typic Xerochrept) as described by Saiz-Jimenez et at. (refs. 185, 188). Note the dominance of carbohydrate-type signals in the unextracted soil sample (a). Most of these carbohydrates are removed in the first water-extraction step and form the highly complex polysaccharide fraction (b) which exhibits typical hexose (m/z 102, 126), pentose (m/z 114), deoxyhexose (m/z 128) and hexosamine (m/z 125, 137, 151) signals. The fulvic acid pattern (c) appears to consist of a mixture of furan-type fragments (e.g. m/z 68, 82, 96, 110) and aromacic fragments (e.g. m/z 78, 94, 120, 124, 138, 150), several of which are 1ignin-derived molecular units. Compared with that of fulvic acid, the humic acid pattern (d) shows even more prominent aromatic signals, in addition to pyrrole (m/z 67, 81 , 95) and indole (m/z 117, 131) series'. The pattern of extracted soil (e) shows a high degree of similarity to the humic acid pattern indicating the presence of unextractable humic acid-like materials, known as humins. Also note that characteristic lignin-type fragments at m/z 124, 150 and 164 are abundant in extracted soil. Throughout all spectra, sulphur-containing ion signals are more or less apparent at m/z 34 (H2S), 48 (CH3SH) and 64 (SO2), although these appear to be equally pronounced in the fulvic and humic acid fractions.

Good Carb Diet

Good Carb Diet

WHAT IT IS A three-phase plan that has been likened to the low-carbohydrate Atkins program because during the first two weeks, South Beach eliminates most carbs, including bread, pasta, potatoes, fruit and most dairy products. In PHASE 2, healthy carbs, including most fruits, whole grains and dairy products are gradually reintroduced, but processed carbs such as bagels, cookies, cornflakes, regular pasta and rice cakes remain on the list of foods to avoid or eat rarely.

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