大屯海和长桥海表层沉积物粒度和营养盐分布特征

Grain size and nutrient distribution characteristics of surface sediments in Datun Lake and Changqiao Lake,Southwestern China

为揭示大屯海和长桥海表层沉积物粒度及营养盐分布特征,测定蒙自盆地两大浅水湖泊共计65个样品的粒度、总有机碳(TOC)和总氮(TN),分析上述指标的空间分布及其相关性。结果显示,湖泊表层沉积物以粉砂和黏土为主,粉砂是研究区表层沉积物的优势粒度,反映了水动力状况;粒度空间分布特征与入湖河流有关。大屯海表层沉积物TOC和TN质量分数分别为1.91%~8.78%、0.21%~0.81%,而长桥海为0.17%~4.70%、0.01%~0.53%。大屯海表层沉积物TN、TOC与黏土呈负相关,与砂呈正相关。两大湖泊属于浅水型湖泊,水动力强,TN和TOC分布主要受控于表层沉积物中粗颗粒和水动力状况;表层沉积物中TN和TOC主要分布在远岸深水至较深水的湖心静水区,形成类似于同心圆状的分布特征,表层沉积物是湖泊富营养化的潜在内源。

In order to reveal the grain size and nutrient distribution characteristics of surface sediments in the Datun Lake and Changqiao Lake,65 samples from these two shallow lakes in the Mengzi Basin were measured for grain size,total organic carbon(TOC)and total nitrogen(TN).The spatial distribution characteristics and their correlation of these parameters were analyzed.The results showed that the surface sediments of the lakes were mainly composed of silt and clay.The silt component was the dominant grain size of the sediments in the study lakes,reflecting the hydrodynamic forces.The spatial distribution characteristics of grain size were related to the rivers entering the lake.The TOC and TN mass fractions of surface sediments in the Datun Lake were 1.91%-8.78%and 0.21%-0.81%,respectively,while those in the Changqiao Lake were 0.17%-4.70%and 0.01%-0.53%.TN and TOC in the surface sediments of the Datun Lake had a negative correlation with the content of clay component and a positive correlation with the content of sand component.The two major lakes belonged to shallow water lakes with high hydrodynamic forces,and the distribution of TN and TOC was controlled by the coarse particle matter and hydrodynamic conditions.TN and TOC in the sediments were mainly distributed in the remote shore deep water to deeper still water areas in the lake center,forming a distribution characteristic similar to a concentric circle,which was a potential endogenous source of lake eutrophication.