Fresh weight (FW), dry weight (DW), carbon and nitrogen content were measured for specimens of Laminaria saccharina (Heterokontophyta: Phaeophyceae) sampled in the eastern English Channel in order to conduct a biometrical study. The aim was to relate carbon and nitrogen masses of the algae to a simple and rapid morphological measurement of the total length of the sporophyte. These relationships were highly significant and appeared very useful to express the standing biomass of L. saccharina in terms of carbon or nitrogen and then to consider dynamic processes such as primary production. Variations in tissue carbon (C) and nitrogen (N) were examined over a complete seasonal cycle. Average carbon and nitrogen content ranged from 23·9 to 31·4% and 2·23 to 3·42% of the total dry weight, respectively. Variations in C/N ratio showed a clear seasonal pattern with an increase in the early spring corresponding to strong photosynthesis and growth.
The gas-phase reaction of oxygenated aromatic compounds m-cresol, o -cresol, and p-cresol with hydroxyl radicals has been studied by GC-MS. Experiments have been performed in a large-volume photoreactor (8000 L) at 294 ± 2 K and atmospheric pressure. The relative kinetic method was used to determine the rate constants for these reactions, with 1,3,5-trimethylbenzene as a reference compound. The rate constants obtained are k OH (mcresol) = (5.88 ± 0.92) × 10 −11 cm 3 molecule −1 s −1 , k O H (o -cresol) = (4.32 ± 0.52) × 10 −11 cm 3 molecule −1 s −1 , and k O H ( p-cresol) = (4.96 ± 0.75) × 10 −11 cm 3 molecule −1 s −1 . The degradation products observed and their respective molar yields were methyl-1,4-benzoquinone 12.4 ± 1.2%, 5-methyl-2-nitrophenol 1.5 ± 0.3%, and 3-methyl-2-nitrophenol 1.4 ± 0.3% from m-cresol, methyl-1,4-benzoquinone 5.6 ± 0.9%, and 6-methyl-2-nitrophenol 4.7 ± 0.8% from o -cresol, and 4-methyl-2-nitrophenol 17.2 ± 2.5% from p-cresol. This kinetic and product data are compared with the literature, and the reaction mechanisms are discussed. Our results are in accordance with the previous studies (Atkinson,
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