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Seaweed debris is susceptible to being buried in sediments due to natural environmental changes and human activities. So far, the effect of buried seaweeds on the environment and its decomposition mechanism remains unclear. This study simulated the decomposition of seaweed Gracilariopsis lemaneiformis for 180 days with different burial depths (0 cm and 10 cm) and burial weights (10 g and 20 g). Our findings revealed that compared with Gracilariopsis decomposition on the sediment surface, the seaweed buried in sediment slowed down the release of N, P, and dissolved organic carbon (DOC) by enhancing the activity of diverse anaerobic microbes (i.e. Draconibacterium , Desulfuromusa , Sediminispirochaeta), which were associated with organic matter decomposition. The enhanced burial quantity of Gracilariopsis resulted in a 3.28 % increase in sediment OC and enriched the humification degree of DOC in seawater. These results highlight the role of seaweed burial in enhancing OC sequestration in marine environments. [Display omitted] • An indoor simulation of seaweed burial on the OC and nutrients was analyzed. • Seaweed buried in sediment mitigated the release of DOC and nutrients in seawater. • Buried seaweed increased the sediment OC pool and seawater DOM humification degree. • Seawater DOC concentration correlated with the quantity of buried seaweed. • Burial seaweed increased the relative abundance and diversity of anaerobic microbes. [ABSTRACT FROM AUTHOR]

Surface sediments were collected from the main path of Kuroshio Current (KC) off eastern Taiwan (ETW), and laboratory incubation was conducted for the study of the nutrient exchange at the sediment-water interface. Exchange fluxes of NO 3 − -N, NO 2 − -N, NH 4 + -N, PO 4 3 − -P and SiO 3 2 − -Si under simulated site condition were − 0.0866, 0.00146, 0.0634, − 0.00812 and − 0.181 mmol m − 2 d − 1 , respectively. This indicated that sediments in the studied area might act as a source of NO 2 − -N and NH 4 + -N and a sink of NO 3 − -N, PO 4 3 − -P and SiO 3 2 − -Si. Factors affecting nutrient exchange fluxes were studied by changing incubation conditions. Compared with some coastal areas in China, the main path of KC off ETW showed relatively low nutrient exchange fluxes at the sediment-water interface. It could be inferred that the sediment-water exchange of nutrients in the main path of KC off ETW had little influence on the downstream nutrient transportation by KC year-round based on the results of this research. [ABSTRACT FROM AUTHOR]

In order to compare the effects of weathering on two types of mixed oil, simulated weathering experiments were performed. The first sample was a mixture of two fresh oils and the second sample was a mixture of one fresh oil and another oil sample that had undergone a serious weathering process. Comparative studies evaluated decay rates and changes in diagnostic ratios of some fingerprinting biomarkers. Results showed that the mixing process affected the weathering rate of some compounds in the oils and also that certain diagnostic ratios are more suitable for estimating mixing proportions. A Pr/ n -C 17 versus Ph/ n -C 18 plot can be used to identify the end-numbers of mixed oils and the (C 13 + C 14 )/(C 25 + C 26 ) ratio is a useful diagnostic ratio to detect the degree of weathering. Finally, hopane, sterane, and alkylated PAH fingerprints were found to give useful insights about the sources of the mixed oils. [ABSTRACT FROM AUTHOR]

With the increasing demand for and consumption of crude oils, oil spill accidents happen frequently during the transportation of crude oils and oil products, and the environmental hazard they pose has become increasingly serious in China. The exact identification of the source of spilled oil can act as forensic evidence in the investigation and handling of oil spill accidents. In this study, a weathering simulation experiment demonstrates that the mass loss of crude oils caused by short-term weathering mainly occurs within the first 24h after a spill, and is dominated by the depletion of low-molecular weight hydrocarbons (18 n-alkanes). Short-term weathering has no significant effect on δ 13C values of individual n-alkanes (C12–C33), suggesting that a stable carbon isotope profile of n-alkanes can be a useful tool for tracing the source of an oil spill, particularly for weathered oils or those with a relatively low concentration or absence of sterane and terpane biomarkers. [Copyright &y& Elsevier]