贵州百花湖分层期水体有机碳及其稳定碳同位素组成分布特征与控制因素

Stable Isotopic Composition and Distribution Characteristics of Organic Carbon in the Stratified Column of Lake Baihua,Guizhou Province

研究湖水溶解有机碳（Dissolved organic carbon,DOC）和颗粒有机碳（Particle organic carbon,POC）的空间变化特征有助于揭示湖泊有机碳的来源、迁移转化过程与控制因素。本文通过对贵州百花湖分层期水体DOC和POC浓度及其碳稳定同位素组成的对比研究,揭示了百花湖分层期水体有机碳浓度及稳定碳同位素的空间分布特征。研究结果表明,百花湖夏季分层期水体DOC和POC的浓度范围分别为1.97～3.26mg/L（平均值2.58mg/L）和0.60～2.43mg/L（平均值1.14mg/L）,且呈现出＂上层高、下层低＂的特征。水体DOC和POC浓度主要受藻类活动控制。水体δ13 CDOC值随深度增加呈偏正趋势,这可能是由深层水体溶解有机质发生矿化作用和分解作用所致。水体δ13 CPOC值随水体深度增加呈偏负趋势,上下层水体藻类生产力差异和沉积物再悬浮作用可能是导致该现象的主要原因。受光降解作用影响,百花湖水体δ13 CDOC较δ13 CPOC偏正。

Investigations on the dissolved organic carbon （DOC） and particulate organic carbon （POC） in lake water help to re- veal the sources and fate of organic carbon. The concentrations and stable carbon isotopic compositions of dissolved organic car- bon （DOC） and particulate organic carbon （POC） in Lake Baihua, Southwest China, were determined to investigate the spatial distribution of organic carbon in the stratified water column of Lake Baihua. The results indicated that DOC and POC concen- trations are within the ranges of 1.97--3.26 mg/L （with a mean value of 2.58 mg/L） and 0.60--2.43 mg/L （with a mean val- ue of 1.14 mg/L）, respectively. Both DOC and POC concentrations decrease with depth in the lake during stratification. Algal activity dominates the variations of DOC and POC in the water column. The considerable enrichment of 813 CDOC with depth in Lake Baihua during the stratified season is most likely due to mineralization and decomposition processes in the deeper water. The 13 C values of POC were 13 C-depleted progressively with depth during the stratified period because of differences in productivity and sedimentary resuspension between epilimnion and respiration. The consistent 813 C-depletion of POC relative to DOC may have resulted from the fact that the DOC pool was more vulnerable to photodegradation.