Humic Substances from Interment Sites II. Digest Products of Sequential Degradation Reactions

Humic acids (HAs), isolated from the sodium hydroxide extracts of gravefill and body imprint soil samples from the medieval burial site at Sutton Hoo, were subjected to sequential degradations using sodium amalgam (NaA), sodium in liquid ammonia (NaLA), and alkaline permanganate (AP). Ether soluble products were isolated from the digests, methylated, and identified by GCMS. Considerations of the degradation mechanisms that would apply led to indications of the types of structures in the HAs that could give rise to the volatile methylated products identified. A comparison was made between the digest products of HAs isolated using sodium hydroxide, dimethylsulphoxide and hydrochloric acid, and neutral sodium pyrophosphate solutions from a body ‘imprint’ soil, and the HAs isolated in sodium hydroxide from a sapric histosol. The results indicated differences in the origins of some of the volatile compounds, and in the ratios of these compounds in the gravefill (which had more lignin derived structures) and body ‘imprint’ samples (with more microbially derived components). The compounds identified in the digests of the sapric histosol were more in line with the conventional degradation products of soil HAs than with the HAs from the grave sites.