Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is a heavily applied herbicide for both agricultural, other than rice paddies, and non-agricultural uses. In this study, we measured the concentration of diuron in river waters in Hiroshima prefecture, Japan, and determined photochemical and biological degradation rates, half-life and its degradation products. From April to October in 2004, water was taken from the Kurose and Ashida rivers. Diuron was extracted by solid phase extraction and then measured by high performance liquid chromatography with UV detection. The concentration range of diuron in the river water analyzed was 0.35〜3.6μg L^-1 (av. 0.69μg L^-1). The photochemical decomposition rate of diuron added into the rivers was determined by irradiation for several hours of the collected water samples using a solar simulator, or by using natural sunlight for 12-25 days. The direct photolysis constant of diuron in water was k_DP=3.38×10^-5s^-1 when the photolysis rate constant was normalized to the solar noon conditions of 34°N in spring. The indirect photolysis constant via oxidation with hydroxyl radical (OH) was determined as k_IP= 9.29×10⁹ M^-1s^-1. In the Kurose river, the half-life of diuron by direct, indirect and total photolysis was estimated as 5.7, 5.8〜43 and 2.9〜5.0h, respectively. The half-life of diuron was 9〜38d when the water samples were irradiated using natural sunlight (October-December, 2006). Biodegradation of diuron was examined by incubating unfiltered river waters containing diuron at 21°C in the dark for three months. The biodegradation half-life of was 602〜814 d. The degradation products of diuron through photo and biodegradation processes were analyzed by liquid chromatography - mass spectrometry and gas chromatography - mass spectrometry. 3-(3-chloro-4-hydroxyphenyl)-dimethylurea, 3-(4-chloro-3-hydroxylphenyl)-dimethylurea and 3,4-dichloroaniline were identified, but other 4 compounds were not. It was estimated that a significant portion of diuron discharged into river water in Hiroshima prefecture was transported into the Seto Inland Sea, without any or with only a little degradation; thus being a potential source of pollution in coastal waters.

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Dietary preferences of archaeological and paleontological animals have been investigated based on stable carbon isotope ratios (δ¹³C) of collagen and non-collagenous proteins in fossil bones. The δ¹³C of individual compound in lipids from fossil bones were recently applied to the reconstruction of palaeodietary of animals. In the present study, we analyze the concentrations, class distributions, and δ¹³C values of fatty acids and steroids in the Pleistocene to Pliocene fossil whale and the Miocene fossil sea cow (Dusisiren sp.) bones, and evaluate their applicability as indicators of palaeodietary and fossil diagenesis. Biosynthetic steroids as cholesterol are detected in the Pleistocene whale bones, while the sterols are very poor in the older Pliocene whale samples, of which major steroids are their diagenetic compounds such as cholestanes and cholestenes. However, a large amount of cholesterol characterizes the Miocene fossil sea cow bone. We also can identify labile unsaturated fatty acids from all fossil whale and sea cow bones. It is suggested that the relative abundances of unsaturated to saturated fatty acids can be useful indicator for estimating diagenetic stage of fossil bones and checking contamination. The δ¹³C values of fatty acids in the fossil whale and sea cow bones range widely from -25.7 to -16‰, and there are differences of 1 to 4‰ between several fatty acid homologues within the same sample. Thus, the δ¹³C analyses of fatty acids in fossil bones may be less applicable for reconstructing palaeodietary. On the other hand, the δ¹³C values of steroidal compounds within the same sample are almost similar, although these values vary ranging between -29.6‰ and -24.4‰ among the different whale samples. Furthermore, the steroidal δ¹³C value in the sea cow sample is -20.5‰, which is concordant with that of food in sea cow. From these results, the δ¹³C value of steroid in fossil bone can be strongly useful tool for reconstructing palaeodietary of paleontological animal.

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It is one of the central problems in organic geochemistry to elucidate chemical structure, origins and geochemical reactions of insoluble organic matter (humic substances or kerogen) in sediments on molecular level. In this paper, studies of insoluble organic matter in recent lake and marine sediments conducted by the present author during the past 40 years are reviewed. Humic acid and kerogen from sediments shows relatively high H/C and N/C ratios. These features are associated with their relatively high contents of aliphatic and proteinaceous components and carbohydrates. Chemical and oxidative degradations of sedimentary kerogens produce a series of aliphatic carboxylic acids with lesser amounts of benzenecarboxylic acids and lignin-derived phenolic acids. These results indicate that insoluble organic matter in sediments is essentially derived from aquatic organisms (i.e. phytoplankton). The author presented a hypothesis that Maillard-type reaction of carbohydrates with protein and lipids is responsible for production of humic substances in aquatic sediments, and a laboratory experiment was performed as a step to prove the hypothesis. A laboratory maturation experiment demonstrated that the chemical reactions associated with generation of petroleum-type alkanes from humic substances closely resembles those from fossil kerogen. An additional heating experiment of young sedimentary lipids indicated that polymethylene chains in fossil kerogen can come from condensation of young lipids.

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