Abstract

The biodegradability of organic carbon in aquatic ecosystems has been broadly attributed to a variety of interacting physical, chemical and biological factors and processes. The Red River is the second largest river in Vietnam. It also constitutes the main source of water for a large percentage of the population of North Vietnam, however, little has been published on the variation in biodegradability of organic matter in this ecosystem, despite its importance in terms of carbon export to the adjacent coastal ocean. Here, we present the results of an investigation into seasonal and spatial variations of the biodegradability of organic carbon in the Red River basin, North Viet Nam. Biodegradability of DOC (BDOC) and POC (BPOC) seasonally differed at the four stations investigated. BDOC concentrations ranged from 0.2 − 2.84 mgCl⁻¹ and BPOC concentrations fluctuated from 0.02 − 2.6 mgCl⁻¹. In the biphasic degradation, the degradation constant for the labile fraction of DOC (k₁) varied between 0.0036 and 0.6357, with values being significantly higher (p < 0.014) during the rainy season than during the dry season. In contrast, no significant difference (p = 0.352) in the biodegradability of the POC labile fraction was observed. In general, the average observed in our study values of the biodegradable fraction of particulate was lower than BDOC, BPOC ranged from 16% to 39%, with biodegradability of total organic carbon (BTOC) ranging from 33% to 44%. The higher rainy %BDOC (49%) than dry season (29%) in watersheds dominated by wetlands.

摘要

水生生态系统中有机碳的生物降解性广泛归因于各种相互作用的物理、化学和生物因素和过程。红河是越南第二大河。它也是北越大部分人口的主要水源，然而，尽管它在向邻近沿海海洋输出碳方面很重要，但关于该生态系统中有机物质生物降解性变化的报道很少. 在这里，我们展示了对越南北部红河流域有机碳生物降解性的季节性和空间变化的调查结果。在调查的四个站点中，DOC (BDOC) 和 POC (BPOC) 的生物降解性随季节变化。BDOC 浓度范围为 0.2 - 2.84 mgCl^-1和 BPOC 浓度从 0.02 - 2.6 mgCl ^-1波动。在双相降解中，DOC 不稳定部分的降解常数 (k ₁ ) 在 0.0036 和 0.6357 之间变化，雨季的值显着高于 旱季( p < 0.014)。相比之下，没有 观察到 POC 不稳定部分的生物降解性有显着差异 ( p = 0.352)。一般而言，我们研究中观察到的颗粒物可生物降解部分的平均值低于 BDOC，BPOC 介于 16% 至 39% 之间，总有机碳的生物降解性 (BTOC) 介于 33% 至 44% 之间。在以湿地为主的流域中，雨季 %BDOC (49%) 高于旱季 (29%)。