贵州草海颗粒物和沉积物有机碳氮同位素特征及来源研究OA北大核心CSTPCD

Caohai Lake is a typical karst lake on the Guizhou plateau,with a fragile ecological environ-ment.Since 2020,Caohai Lake has transitioned from a grass-type lake to an algae-type lake,and water quality has deteriorated as aquatic vegetation declined.Identifying the sources of organic matter in the water and sediments of lakes is crucial for understanding the nutrient cycle and controlling eutrophica-tion.In this study,we analyzed the total organic carbon(POC,TOC)and total nitrogen(PON,TON)of the particulate matter and sediments in the Caohai Lake and its inflow rivers.For source identification,the ratios of carbon isotopes(δ13C)and nitrogen isotopes(δ15N)and the ratio of carbon to nitrogen(C/N)of particulate matter and sediments were determined.The resulting data was fed into the MixSIAR iso-tope model,allowing the organic carbon and nitrogen sources and their contributions to suspended partic-ulate matter and sediments to be qualitatively and quantitatively determined.In March 2023(dry season),water and sediment samples were collected at 13 sampling sites in Caohai Lake(L1-L9)and its four main tributaries(R1-R4)for analysis.The percentage content of POC and PON were 1.79%-25.72%and 0.26%-2.98%in the particulate matter and the percentage content of TOC and TON were(1.50%-27.58%)and(0.16%-1.82%)in the sediment,respectively.The δ13C and δ15N ranges of the particulate matter were from-27.56‰ to-23.64‰ and from 3.12‰ to 10.93‰,and the δ13C and δ15N of the sediments ranged from-28.18‰to-20.53‰and 1.70‰to 6.58‰,respectively.The δ13C and δ15N values of the par-ticulate matter and sediment both displayed significant differences and there were no clear correlations be-tween Caohai Lake and the four tributaries,indicating that the lake and its tributaries have different sourc-es of organic matter,and that the organic matter in Caohai Lake is not affected by inflow rivers.The pri-mary sources of particulate organic carbon to the lake are atmospheric deposition(21.1%)and aquatic plants(20.7%),and the primary sources of nitrogen is soil organic matter(25.6%)and aquatic plants(25.3%).The organic carbon of the sediments primarily comes from atmospheric deposition(34.4%)and aquatic plants(33%),and the nitrogen primarily from fertilizer(24%).The difference in organic nitrogen sources between particulate matter and sediment shows that the organic nitrogen from soil organic matter and aquatic plants is easily decomposed,while nitrogen from fertilizer is readily deposited.The results provide a reference for controlling the sources of nutrient loading to Caohai Lake.