九龙江口枯水期溶解有机物的组成及其生物可利用性

Chemical composition and bioavailability of dissolved organic matter in Jiulong River Estuary during dry season

为了深入了解河口溶解有机物 (DOM) 的生物地球化学循环过程,基于现场调查,结合实验室受控培养,研究了枯水期九龙江口 DOM 的组成及其生物可利用性,探讨了枯水期 DOM 各组分的生物可利用性的空间差异及其影响因素。结果表明,九龙江口溶解有机碳 (DOC)、总糖 (TCHO) 的浓度和 DOM 的紫外吸收系数 (a;) 总体上表现出上游高、下游低的分布特征。生物可利用溶解有机碳 (BDOC) 的含量 (以 DOC 占比表示) 在 6.0%~20.2%之间,其浓度与盐度呈显著负相关,与 DOC 和 TCHO 呈显著正相关,说明河流输入的 DOC 是九龙江口 BDOC 的重要来源,DOM 中的活性组分糖类对 BDOC 有重要的贡献。DOC 浓度与盐度呈显著负相关,在河口混合过程中基本呈现保守行为,与此相反,DOM 的组分却呈不保守混合。TCHO 组分在河口低盐度区存在一定程度的去除,而 a;和 SUVA;在中盐度区存在明显的添加,说明 DOC 的表观保守混合行为是因为同时存在 DOM 活性组分的去除和惰性组分的添加。DOM 组分分析表明微生物降解、颗粒有机物的解吸作用显著改变了九龙江口 DOM 的分子组成。

In order to better understand the biogeochemical cycle of estuarine dissolved organic matter(DOM), spatial distribution and bioavailability of DOM and its major compounds as well as the ultraviolet absorption coefficient (a;) and specific ultraviolet absorbance(SUVA;) were investigated based upon field observation and laboratory controlled incubation.The factors regulating bioavailability of DOM were also studied. The results showed that dissolved organic carbon (DOC), total carbohydrate (TCHO) concentrations, and a;were high in the upstream, while low in the downstream of Jiulong River Estuary. Bioavailable dissolved organic carbon(BDOC) in Jiulong River Estuary ranged from 6.0% to 20.2%. The concentrations of BDOC were negatively correlated with salinity and positively correlated with DOC and TCHO, indicating that DOC input from the river was the important source of BDOC in the Jiulong River Estuary, and TCHO had an important contribution to BDOC. DOC concentrations were negatively correlated with salinity, and showed conservative behavior during estuarine mixing. However, TCHO components were significantly removed in the low salinity area of the estuary, whereas a;and SU-VA;were significantly added in the middle salinity area, indicating that the apparent conservative behavior of bulk DOC in the estuary was due to the existence of simultaneous removal of bioavailable components and addition of refractory components of DOM. DOM component analysis revealed that microbial degradation and desorption of particulate organic matter significantly changed the molecular composition of DOM in Jiulong River Estuary.