The global distribution of polycyclic aromatic hydrocarbons in recent sediments

Contrasted distributions of triterpene derivatives in the sediments of Lake Caçó reflect paleoenvironmental changes during the last 20,000 yrs in NE Brazil

“…They are divided into three main groups with regard to their mass spectra, the most significant fragments of which are listed in Table (Laflamme and Hites, 1978;Wakeham et al, 1980;Chaffee et al, 1984;Hazai et al, 1986;Chaffe and Fookes, 1988;Loureiro and Cardoso, 1990;Stout, 1992). The relative intensities of ions m/z 145, 157, 158, 170 and 172 depend on whether additional unsaturations are located on rings B, C, D or E. As demonstrated by several authors (Lohmann, 1988;Loureiro and Cardoso, 7 1990), the double bond position in natural product precursors is often preserved in diagenetic derivatives.…”

“…This leads to the corresponding di-unsaturated counterparts such as ursadiene and oleanadiene (ten Haven et al, 1992). After this primary transformation, various pathways lead to (i) the formation of Δ 2 triterpenes, Δ 2,x triterpadienes or ring A contracted triterpenes (Elgamal et al, 1969;Ekweozor et al, 1979;ten Haven et al, 1992); (ii) the progressive aromatisation of the skeleton from ring A to finally produce fully aromatised pentacyclic moieties (Laflamme and Hites, 1978;Wakeham et al, 1980;Wolff et al, 1989); (iii) the loss of ring A (des-A-compounds), followed by the progressive aromatisation towards ring 15 E (Corbet, 1980;Trendel et al, 1989). The loss of ring A is initiated by its opening leading to the formation of A-seco-intermediates, a phenomenon that readily occurs in plant leaves under photochemical/photomimetic control (Corbet, 1980).…”

Polycyclic aromatic hydrocarbons contamination in subsoil from outskirts of Beijing, People's Republic of China

“…Moreover, at low to moderate temperature, as in the wood stove (Lake et al, 1979), or as from the combustion of coal (Laflamme and Hites, 1978), low molecular weight parent PAH compounds are abundant. At high temperature, such as in the vehicle emissions, the high molecular weight parent PAHs compounds are dominant (Lee et al, 1977).…”

Anthropogenic Influence on the 14C Activity and Other Constituents of Recent Lake Sediments: A Case Study1

“…Aliphatic and aromatic hydrocarbons have been extensively analyzed in various types of aquatic sediments (Blumer & Sass 1972;Youngblood & Blumer 1975;Laflamme & Hites 1978;Giger, Schaffner & Wakeham 1980;Wakeham, Schaffner & Giger 1980a, b). Giger and Schaffner (1978) described in detail the analytical methodology used in this study.…”