Guanabara Bay is an estuarine environment of great socio-economic importance, where around 12 million people live in its drainage basin. We aim to characterize the sedimentary matter of Guanabara Bay, two mangrove systems therein (Suruí and Piedade mangroves), and the rivers, São João do Merití, Iguaçu, Sarapui, Suruí, and Guapimirim, by performing sedimentological, mineralogical, elemental/isotopic organic matter composition (total organic carbon and total nitrogen, ¹³C and ¹⁵ N) and organic matter petrography. Samples from the entrance of the bay present high values of quartz, low values of C/N ratio, and high percentages of diffuse amorphous organic matter indicating marine influence, whereas samples from rivers mouths present high percentages of translucent lignocellulosic, opaque lignocellulosic, gelified organic matter, and high C/N ratio probably due to the influence of terrestrial organic matter that comes from the drainage basin and the mangroves areas. Stations of the central sector of the bay were characterized by high percentages of TOC, intermediated values of δ¹³C, low C/N ratio, and also high diffuse amorphous organic matter indicating a predominant influence of organic matter from algae origin. High values of δ¹⁵N indicate large assimilation of nitrate or a high denitrification process in the highest productivity areas. In the river mouth regions, it is mainly influenced by terrestrial organic matter; however, in the northwestern and western sectors, organic matter is influenced both by terrestrial and domestic sewage influences which promote anaerobic decomposition of organic matter.

瓜纳巴拉湾是一个具有重要社会经济意义的河口环境，约有 1200 万人居住在其流域。我们的目标是通过沉积学、矿物学、元素/同位素有机物分析来表征瓜纳巴拉湾、其中的两个红树林系统（苏鲁伊和皮埃达德红树林）以及圣若昂杜梅里蒂河、伊瓜苏、萨拉普伊、苏瑞和瓜皮米林的沉积物质物质组成（总有机碳和总氮，¹³ C 和¹⁵ N) 和有机质岩相学。来自海湾入口的样品具有高石英值、低 C/N 比值和高百分比的扩散无定形有机物，表明受海洋影响，而来自河口的样品则具有高百分比的半透明木质纤维素、不透明木质纤维素、凝胶化有机物物质和高 C/N 比可能是由于来自流域和红树林地区的陆地有机质的影响。海湾中央部门的站点的特点是 TOC 百分比高、δ ¹³ C为中间值、C/N 比低，以及高扩散无定形有机物质，表明藻类来源的有机物质的主要影响。δ ^{15 的}高值N 表示在最高生产力区域中硝酸盐的大量同化或高反硝化过程。在河口地区，主要受陆地有机质的影响；然而，在西北部和西部地区，有机物受到促进有机物厌氧分解的陆地和生活污水的影响。