巢湖水体二氧化碳浓度时空分布特征及其水-气交换通量

Temporal and spatial variation of carbon dioxide concentration and its exchange fluxes in Lake Chaohu

为揭示巢湖水体二氧化碳浓度(c CO2)时空变化特征及其影响因素,2017年2、4、8和11月分别采集巢湖表层水样,测定水样的理化、生物学参数以及c CO2,并以此计算其水-气界面交换通量.结果表明:巢湖表层水体c CO2的变化范围为13.31～55.47μmol/L,年平均值为26.27μmol/L,在空间上呈现出西高东低的分布趋势;在季节上表现为暖季(夏季)低、冷季(春、秋和冬季)高的规律.巢湖表层水体c CO2与溶解性有机碳浓度呈显著正相关,与叶绿素a浓度呈显著负相关,说明有机质分解和光合作用在巢湖CO2生物化学循环过程中占重要作用;同时,南淝河等入湖河流污染严重,输入大量有机和无机碳,对西巢湖水体CO2贡献较大.总体上,巢湖CO2排放量相对较低,巢湖部分区域在冷季(2、11月)表现为CO2的汇.本研究对于明晰富营养化湖泊CO2排放特征以及准确估算全球内陆湖泊碳通量等都具有参考价值.

In order to understand the temporal and spatial variation of carbon dioxide concentration ( cCO2 )and its influencing factors in the surface water of Lake Chaohu, the physicochemical parameters, biological parameters, and c CO 2 of surface (15-30 cm)water samples collected in February, April, August and November in 2017 from Lake Chaohu, representing different seasons, were measured. The surface water-air flux of CO2 was then calculated based on gradient method as well. The results showed that the c CO2 ranged from 13.31-55.47 μmol/L. The average annual cCO2 was 26.27 μmol/L. The cCO2 was higher in the west lake sub-lake zone than that in the central and east sub-lake zones. The surface water of Lake Chaohu had a lower cCO2 in the warm season (summer) than in cool and cold seasons (spring, autumn and winter). c CO2 was positively correlated with dissolved organic carbon (DOC)concentration and negatively correlated with chlorophyll-a concentration, suggesting that photosynthesis and decomposition of organic matter plays an important role in the biochemical cycle of CO2 . Due to the serious pollution of inflowing rivers surrounding Lake Chaohu, DOC input from the watershed supplied substrates for CO2 production. Lake Chaohu was a relatively small source for atmosphere CO2 compared to others studies. Lake Chaohu shifted from a CO2 source to a sink in cold seasons.