百花湖水体有机碳及其稳定碳同位素组成、分布特征与控制因素研究

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	百花湖水体有机碳及其稳定碳同位素组成、分布特征与控制因素研究
	徐丹
导师	陈敬安
	2014
学位授予单位	中国科学院研究生院
学位授予地点	北京
学位名称	硕士
学位专业	环境科学
关键词	百花湖分层期混合期 Poc Doc 稳定碳同位素
摘要	湖泊有机碳是湖泊碳的关键组分，沉积封存的有机碳能够为湖泊提供碳和能源，在湖泊碳循环中扮演着重要角色。研究湖水颗粒有机碳(particle organic carbon, POC)和溶解有机碳(dissolved organic carbon, DOC)的时空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，为精细刻画湖泊碳循环提供坚实科学数据。本文选取贵州百花湖作为研究对象，于2013年8月夏季湖水分层期和2013年11月冬季湖水混合期采集分层水样，通过对POC和DOC浓度， POC、DOC和DIC碳稳定同位素、C/N比值、叶绿素a(Chl-a)浓度和相关环境因子的综合对比研究，揭示了百花湖水体有机碳浓度及稳定碳同位素的时空变化规律与控制因素，探讨了湖泊POC和DOC的来源、迁移转化过程与机制，取得了如下主要结论和认识。 1、百花湖夏季分层期水体POC和DOC的浓度范围分别为0.60~2.43 mg/L(平均值1.14 mg/L)和1.97~3.26 mg/L(平均值2.58 mg/L)，且呈现出“上层高、下层低”的特征。水体POC浓度主要受藻类活动控制，DOC浓度主要受藻类活动及DOC矿化作用影响。 2、百花湖冬季混合期水体POC和DOC的浓度范围分别为0.57~1.44 mg/L(平均值1.02 mg/L)和1.81~3.57 mg/L(平均值2.58 mg/L)，上下层水体DOC的浓度(除湖心点)差异不大。上述水体POC和DOC浓度变化特征主要与冬季藻类生长缓慢及去分层有关。 3、混合期表层水体POC和DOC(除湖心点)的浓度低于分层期，这一特征主要是由冬季生产力降低所致。 4、夏季分层期，水体δ13CPOC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可能是导致该现象的主要原因。水体δ13CDOC值随深度增加呈偏正趋势，这可能是由上下层水体光合作用和呼吸作用的差异及深层水体溶解有机质的矿化作用所致。受光降解作用影响，百花湖水体δ13CDOC较δ13CPOC偏正。 5、冬季混合期，水体δ13CPOC值呈现出上层与热分层下部处垂向均一，水体δ13CDOC值呈现出上下水体差异较小的特征。这可能与冬季光合作用强度减弱及去分层有关。 6、混合期表层水体δ13CPOC值较分层期偏负，混合期水体藻类生产力减弱可能是导致该现象的主要原因。混合期表层水体δ13CDOC值较分层期偏正，这可能是由混合期表层水体光合作用强度减弱所致。 7、百花湖水体POC浓度及δ13CPOC值主要受藻类活动与分层/去分层作用控制，百花湖水体DOC浓度及δ13CDOC值主要受藻类活动、分层/去分层作用及DOC的矿化作用影响，河流输入影响较小。 8、C/N比和碳同位素的联合示踪结果表明，百花湖水体POC主要来源于藻源有机碳。 9、百花湖水体藻类活动和分层/去分层现象是控制湖泊水体POC和DOC迁移转化过程的关键因素。
其他摘要	Organic carbon is a key component of lake carbons and plays an important role in the carbon cycle of lake since organic carbon sequestrated in lake sediment provides carbon and energy for creatures in the lake. Particulate organic carbon (POC) and dissolved organic carbon (DOC) are two major forms of the lake organic carbon. Investigation on POC and DOC in lake water helps to reveal the sources and the fate of organic carbon and to provide solid scientific date for characterizing the lake carbon cycle. This study chose the Baihua Lake as the research object and collected tiered water samples from the Baihua Lake in August 2013 when the lake water was thermally stratified and in November 2013 when the lake water was well mixed. In addition to the C/N ratio and chlorophyll a (Chl-a), the concentrations and stable carbon isotope compositions of POC, DOC and dissolved inorganic carbon (DIC) were systematically studied to reveal the organic carbon concentrations and control factors and temporal-spatial variations of the stable carbon isotope of organic carbons in the Baihua lake, to explore sources of POC and DOC and to elucidate migration and transformation processes and mechanisms of POC and DOC in the lake. The main conclusions of this study were summarized as followings: 1. During the thermal stratification in August, POC and DOC concentration ranges were 0.60~2.43 mg/L (with a mean of 1.14 mg/L) and 1.97~3.26 mg/L (with a mean of 2.58 mg/L) respectively. Both POC and DOC concentrations decreased with water depth in the lake during the stratification period. Algae activity dominates the variations of POC in the water column. Algae activity and mineralization process dominate the variations of DOC in the water column. 2. During the isothermal condition in November, POC and DOC concentration ranges were 0.57~1.44 mg/L (with a mean of 1.02 mg/L) and 1.81~3.57 mg/L (with a mean of 2.58 mg/L) respectively. Except the HX site, DOC concentrations was spatially (by depth and laterally) uniform. The slow algae growth rate and the absence of thermal stratification influenced the variations of POC and DOC during isothermal condition in November. 3. Epilimnetic POC and DOC (except HX) concentrations were higher in August than in November since stratified surface water in August was warmer and the productivity was higher. 4. In summer, the δ13CPOC values indicated that 13C content in POC depleted progressively with depth during the stratified period because of the different productivity along the water column and sedimentary resuspension between the epilimnion and the hypolimnion. The δ13CDOC values indicated that 13C content in DOC enriched remarkably with depth in the Baihua Lake during the stratified season, and it may likely due to the different photosynthesis and respiration in the epilimnion and in the hypolimnion as well as the mineralization processes occurring in the deeper water. Comparing to the δ13CPOC, the δ13CDOC of the Baihua Lake is more positive may result from that the DOC pool is more vulnerable to photodegradation during the summer. 5. In winter, the δ13CPOC values in the all layers of the isothermal water column were similar. The δ13CDOC values coupled tightly to the mixing regime of the lake and did not exhibit notable vertical or lateral variations. The uniformity of δ13CPOC and δ13CDOC values during the winter season may likely due to the weak productivity and the absence of thermal stratification. 6. Epilimnetic δ13CPOC in the isothermal lake more 13C- depleted values as would be expected less autochthonous primary productivity in November. Epilimnetic δ13CDOC values were enriched during the isothermal condition in November than in August as would be expected a weaker photosynthesis in the isothermal surface waters. 7. Algae activity and stratification/the absence of stratification dominate the variations of POC concentration and δ13CPOC in the water column. Algae activity, stratification/the absence of stratificati
学科领域	环境地球化学
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/5913
专题	研究生_研究生_学位论文
推荐引用方式 GB/T 7714	徐丹. 百花湖水体有机碳及其稳定碳同位素组成、分布特征与控制因素研究[D]. 北京. 中国科学院研究生院,2014.

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