Sources and preservation of organic matter in Plum Island salt marsh sediments (MA, USA): long-chain n-alkanes and stable carbon isotope compositions

Elemental (TOC, TN, C/N) and stable carbon isotopic (delta(13)C) compositions and n-alkane (nC(16-38)) concentrations were measured for Spartina alterniflora, a C-4 marsh grass, Typha latifolia, a C-3 marsh grass, and three sediment cores collected from middle and upper estuarine sites from the Plum Island salt marshes. Our results indicated that the organic matter preserved in the sediments was highly affected by the marsh plants that dominated the sampling sites. delta(13)C values of organic matter preserved in the upper fresh water site sediment were more negative (-23.0+/-0.3) as affected by the C-3 plants than the values of organic matter preserved in the sediments of middle (-18.9+/-0.8) and mud flat sites (-19.4+/-0.1) as influenced mainly by the C4 marsh plants. The distribution of n-alkanes measured in all sediments showed similar patterns as those determined in the marsh grasses S. alterniflora and T. latifolia, and nC(21) to nC(33) long-chain n-alkanes were the major compounds determined in all sediment samples. The strong odd-to-even carbon numbered n-alkane predominance was found in all three sediments and nC(29) was the most abundant homologue in all samples measured. Both delta(13)C compositions of organic matter and n-alkane distributions in these sediments indicate that the marsh plants could contribute significant amount of organic matter preserved in Plum Island salt marsh sediments. This suggests that salt marshes play an important role in the cycling of nutrients and organic carbon in the estuary and adjacent coastal waters. (C) 2003 Elsevier Ltd. All rights reserved.

Community structure of macrobenthos in coastal water off Rushan, southern Shandong Peninsula, and the relationships with environmental factors

To understand the present actuality of the marine ecosystem in the southern coastal water region of the Shandong Peninsula and the impact of the global change and the human activities to the marine ecosystem of the region, the macrobenthic community structure was researched based on data from 26 sampling stations carried out on four seasonal cruises from December 2006 to November 2007. The data was analyzed using PRIMER 6.0 and SPSS 15.0 software packages. The results showed that 236 macrobenthic species in total were collected from the research region by the field works. Most of the species belong to Polychaeta (76 species), Mollusca (75) and Crustacea (60). Of which, 33 species were common species by the four cruises. The dominant species were different among the four seasons, however, the polychaete species Nephtys oligobranchia and Sternaspis scutata were always dominant in the four seasons. The abundances and biomasses of the macrobenthos from the research region were variable in tire four seasons. The results of CLUSTER and MDS analysis showed that the similarities of macrobenthic structures among the stations were low, most of the similarities were at about 40% of similarity values, only that of two stations were up to 60%. In accordance with the similarity values of the macrobenthic structures, the 26 stations were clustered as six groups at arbitrary similarity level of 30%. The ABC curve indicated that the marcofauna communities in the research region had riot been disturbed distinctly. The results of BIOENV and BVSTEP (Spearman) analysis implied that the concentrations of organic matter in bottom water and heavy metal copper in sediment, water depth and temperature of bottom were the most significant environmental factors to affect the macrobentic community.

A high coking-resistance catalyst for methane aromatization

Steaming-dealuminated HZSM-5-supported molybdenum catalysts have been found to be high coking-resistance catalysts for methane aromatization reactions; compared with conventional catalysts, they give a much higher selectivity towards aromatics.