Composition of Carbon-13 and Nitrogen-15 in Sediments of the Ha Long Bay

The Ha Long Bay with beautiful landscape and rich ecosystems is being used by human to develop the economy. The Ha Long Bay is currently affected by human activities causing the sedimentary environment to be much changed. The change of the environment in the Bay was studied using the composition of carbon-13, nitrogen-15 (δ¹³C, δ¹⁵N) and the C/N ratio in sediment of seven cores collected within the Ha Long Bay. In the Ha Long Bay, sedimentary environment receives many source sediment supplies. The north-east of Ha Long bay receives sources from sea, it is characterized by δ¹³C in sediment from -8.79 to -18.01‰, value δ¹⁵N in sediment from 4.36 to 4.73 ‰ and ratio of C/N from 13 to 41, the source organic matter in sediment shows that affected by C4 plant. The centre of Ha Long Bay receives organic source from sea, it is characterized by δ¹³C in sediment from -16.72 to -21.58 ‰, value δ¹⁵N in sediment ranges 4.15 - 5.20 ‰, ratio of C/N in sediment from 7 to 23. The north-west of Ha Long Bay is affected by rivers, it is characterized by δ¹³C in sediment range from -13.64 to -25.77 ‰, value δ¹⁵N in sediment from 2.50 to 4.38 ‰, and ratio C/N from 9 to 19. (author)