1. Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; 2. Key Laboratory of Poyang Lake Environment and Resource Utilization, Ministry of Education, School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang 330031, China; 3. University of Chinese Academy of Sciences, Beijing 100049, China
Abstract：Water samples from Lake Chaohu were collected in January (dry), April (wet-to-dry transition), and July (wet) to explore the variability of CO2 emissions from the shallow lake and the corresponding linkage with the sources and optical composition of CDOM. We coupled diffusion coefficient and mass balance approaches to trace the variability of dissolved CO2 concentration (cCO2) and CO2 efflux (FCO2) from Lake Chaohu, and further explore the potential drivers, especially the potential linkage between CO2 emissions and the optical composition of CDOM. Our results showed that the mean cCO2 of the whole lake area in Chaohu was higher in the wet season ((51.9±71.8)μmol/L) than in the wet-to-dry transition season ((48.9±29.0)μmol/L), and further higher than in the dry season ((35.2±15.6)μmol/L). We observed a slight sink of CO2 in the lake in the dry season ((-98.8±20.1)mg/(m2·d)), and there was no significant difference between the mean FCO2 in the wet season ((219.3±275.5)mg/(m2·d)) and the wet-to-dry transition season ((219.9±157.8)mg/(m2·d)). We found higher mean cCO2 and FCO2 in the western than in the central and further higher than in the eastern area of Lake Chaohu. In the western area of Lake Chaohu, dissolved oxygen (DO) was negatively correlated with cCO2(P<0.05) and FCO2(P<0.001); and we further found that both cCO2 and FCO2 increased with increasing dissolved organic carbon (DOC) (P<0.01) and chlorophyll-a(Chl-a) (P<0.001). Parallel factor analysis coupled with excitation-emission matrices revealed four fluorescent components, and both cCO2 and FCO2 increased with increasing humic-rich components C1 (P<0.01) and C4 (P<0.001). No significant correlation was found between cCO2, FCO2 and tryptophan-like C2, or beteween cCO2, FCO2 and tyrosine-like C3. Our results suggested that elevated trophic level potentially drive the emission of CO2 from Lake Chaohu, and the source and composition of CDOM, especially the input of terrestrial humic-rich substances, potentially favors the emission of CO2 from the lake.
Hyungseok P, Sewoong C, Sungjin K. Effect of buoyant turbulence and water quality factors on the CO2 net atmospheric flux changes in a stratified reservoir [J]. Science of the Total Environment, 2021, 776: 145940.
[2]
Zhang L, Liao Q J H, Gao R, et al. Spatial variations in diffusive methane fluxes and the role of eutrophication in a subtropical shallow lake [J]. Science of the Total Environment, 2020, 759: 143495
[3]
Xiao Q T, Xu X F, Duan H T, et al. Eutrophic Lake Taihu as a significant CO2 source during 2000~2015 [J]. Water Research, 2020, 170: 115331.
[4]
Zagarese H E, Sagrario M, Wolf-Gladrow D, et al. Patterns of CO2 concentration and inorganic carbon limitation of phytoplankton biomass in agriculturally eutrophic lakes [J]. Water Research, 2021, 190(6): 116715.
[5]
Xiao Q T, Duan H T, Qi T C, et al. Environmental investments decreased partial pressure of CO2 in a small eutrophic urban lake: Evidence from long-term measurements [J]. Environmental Pollution, 2020, 263: 114433.
[6]
Zhou Y Q, Zhou L, Zhang Y L, et al. Autochthonous dissolved organic matter potentially fuels methane ebullition from experimental lakes [J]. Water Research, 2019, 166: 115048.
[7]
Singh S, D'sa E J, Swenson E M. Chromophoric dissolved organic matter (CDOM) variability in Barataria Basin using excitation– emission matrix (EEM) fluorescence and parallel factor analysis (PARAFAC) [J]. Science of the Total Environment, 2010, 408(16): 3211-3222.
[8]
Zhang Y L, Zhou L, Zhou Y Q, et al. Chromophoric dissolved organic matter in inland waters: Present knowledge and future challenges [J]. Science of the Total Environment, 2021, 759: 143550.
[9]
Xenopoulos M A, Barnes R T, Boodoo K S, et al. How humans alter dissolved organic matter composition in freshwater: relevance for the Earth's biogeochemistry [J]. Biogeochemistry, 2021, 154: 323-348.
[10]
Clark C D, Bruyn W J D, Brahm B, et al. Optical properties of chromophoric dissolved organic matter (CDOM) and dissolved organic carbon (DOC) levels in constructed water treatment wetland systems in southern California, USA [J]. Chemosphere, 2020, 247: 125906.
[11]
Tao P R, Jin M, Yu X B, et al. Spatiotemporal variations in chromophoric dissolved organic matter (CDOM) in a mixed land-use river: Implications for surface water restoration [J]. Journal of Environmental Management, 2021, 277: 111498.
[12]
Lapierre J F, Guillemette F, Berggren M, et al. Increases in terrestrially derived carbon stimulate organic carbon processing and CO2 emissions in boreal aquatic ecosystems [J]. Nature Communications, 2013, 4(1): 2972-2979.
[13]
Terhi R, T P Y, A D G P. Large-scale patterns in summer diffusive CH4 fluxes across boreal lakes, and contribution to diffusive C emissions [J]. Global Change Biology, 2015, 21(3): 1124-1139.
[14]
Wu Z S, Lai X J, Li K Y. Water quality assessment of rivers in Lake Chaohu Basin (China) using water quality index[J]. Ecological Indicators, 2021, 121: 107021.
[15]
叶琳琳, 吴晓东, 刘波, 等. 巢湖溶解性有机物时空分布规律及其影响因素[J]. 环境科学, 2015, 36(9): 3186-3193. Ye L L, Wu X D, Liu B, et al. Temporal and spatial distribution characteristics of dissolved organic matter and influencing factors in Lake Chaohu [J]. Environmental Science, 2015, 36(9): 3186-3193.
[16]
Striegl R G, Dornblaser M M, Mcdonald C P, et al. Carbon dioxide and methane emissions from the Yukon River system [J]. Global Biogeochemical Cycles, 2012, 26(4): GB00E05.
[17]
John T, Crawford, Robert G, et al. Emissions of carbon dioxide and methane from a headwater stream network of interior Alaska[J]. Journal of Geophysical Research: Biogeosciences, 2013, 118(2): 482-494.
[18]
俞晓琴, 崔扬, 陈慧敏, 等. 城市不同类型水体有色可溶性有机物来源组成特征[J]. 环境科学, 2021, 42(8): 3719-3729. Yu X Q, Cui Y, Chen H M, et al. Sources and optical dynamics of chromophoric dissolved organic matter in different types of urban water. Environmental Science, 2021, 42(8): 3719-3729.
[19]
Cui G N, Wang X, Li C H, et al. Water use efficiency and TN/TP concentrations as indicators for watershed land-use management: A case study in Miyun District, north China [J]. Ecological Indicators, 2018, 92: 239-253.
[20]
Zhou Y Q, Shi K, Zhang Y L, et al. Fluorescence peak integration ratio IC: IT as a new potential indicator tracing the compositional changes in chromophoric dissolved organic matter [J]. Science of the Total Environment, 2017, 574: 1588-1598.
[21]
Zhou Y Q, Liu M, Zhou L, et al. Rainstorm events shift the molecular composition and export of dissolved organic matter in a large drinking water reservoir in China: High frequency buoys and field observations [J]. Water Research, 2020, 187: 116471.
[22]
齐天赐, 肖启涛, 苗雨青, 等. 巢湖水体二氧化碳浓度时空分布特征及其水-气交换通量[J]. 湖泊科学, 2019, 31(3): 766-778. Qi T C, Xiao Q T, Miao Y Q, et al. Temporal and spatial variation of carbon dioxide concentration and its exchange fluxes in Lake Chaohu [J]. Journal of Lake Sciences, 2019, 31(3): 766-778.
[23]
郭燕妮, 李元鹏, 石玉, 等. 大型通江湖泊有色可溶性有机物对不同水文情景的响应[J]. 环境科学, 2020, 41(5): 2198-2209. Guo Y N, Li Y P, Shi Y, et al. Response of Chromophoric dissolved organic matter dynamics to different hydrological scenarios in the two largest freshwater lakes connected to the Yangtze River [J]. Environmental Science, 2020, 41(5): 2198-2209.
[24]
张柳青, 彭凯, 周蕾, 等. 南水北调东线中游枢纽湖泊有色可溶性有机物来源组成特征[J]. 环境科学, 2019, 40(7): 3018-3029. Zhang L Q, Peng K, Zhou L, et al. Characterizing chromophoric dissolved organic matter in key lakes in the Middle Reaches of the East Route of the South-North Water Diversion Project [J]. Environmental Science, 2019, (40)7: 3018-3029.
[25]
石玉, 周永强, 张运林, 等. 太湖有色可溶性有机物组成结构对不同水文情景的响应[J]. 环境科学, 2018, 39(11): 491-524. Shi Y, Zhou Y Q, Zhang Y L, et al. Response of chromophoric dissolved organic matter composition to different hydrological scenarios in large eutrophic Lake Taihu [J]. Environmental Science, 2018, 39(11): 491-524.
[26]
李宇阳, 郭燕妮, 朱俊羽, 等. 不同水文情形下巢湖有色可溶性有机物来源及分布特征[J]. 光谱学与光谱分析, 2021, 41(10): 3286-3293. Li Y Y, Guo Y N, Zhu J Y, et al. Characterizing chromophoric dissolved organic matter (CDOM) in Lake Chaohu in different hydrologic seasons [J]. Spectroscopy and Spectral Analysis, 2021, 41 (10): 3286-3293.
[27]
Amaral J H F, Borges A V, Melack J M, et al. Influence of plankton metabolism and mixing depth on CO2 dynamics in an Amazon floodplain lake [J]. Science of the Total Environment, 2018, 630: 1381-1393.
[28]
Zhang W S, Li H P, Xiao Q T, et al. Urban rivers are hotspots of riverine greenhouse gas (N2O, CH4, CO2) emissions in the mixed-landscape chaohu lake basin [J]. Water Research, 2021, 189: 116624.
[29]
Yang R J, Xu Z, Liu S L, et al. Daily pCO2 and CO2 flux variations in a subtropical mesotrophic shallow lake[J]. Water Research, 2019, 153: 29-38.
[30]
Karim A, Dubois K, Veizer J. Carbon and oxygen dynamics in the Laurentian Great Lakes: Implications for the CO2 flux from terrestrial aquatic systems to the atmosphere [J]. Chemical Geology, 2011, 281: 133-141.
[31]
D'amario S C, Xenopoulos M A. Linking dissolved carbon dioxide to dissolved organic matter quality in streams [J]. Biogeochemistry, 2015, 126(1/2): 99-114.
[32]
Ruchi B, Osburn C L. Chromophoric dissolved organic matter composition and load from a coastal river system under variable flow regimes [J]. Science of the Total Environment, 2021, 760: 141414.
[33]
Grasset C, Sobek S, Scharnweber K, et al. The CO2-equivalent balance of freshwater ecosystems is non‐linearly related to productivity [J]. Global Change Biology, 2020, 26(10): 5705-5715.
[34]
Zhao L Y, Li N, Huang T L, et al. Effects of artificially induced complete mixing on dissolved organic matter in a stratified source water reservoir [J]. Journal of Environmental Sciences, 2022, 111: 130-140.
[35]
Zhou Y Q, Li Y, Yao X L, et al. Response of chromophoric dissolved organic matter dynamics to tidal oscillations and anthropogenic disturbances in a large subtropical estuary [J]. Science of the Total Environment, 2019, 662: 768-778.
[36]
Varol M. CO2 emissions from hydroelectric reservoirs in the Tigris River basin, a semi-arid region of southeastern Turkey [J]. Journal of Hydrology, 2019, 569: 782-794.
[37]
Yi Z, Blough N V. Photoproduction of one-electron reducing intermediates by chromophoric dissolved organic matter (CDOM): Relation to O2- and H2O2 photoproduction and CDOM photooxidation [J]. Environmental Science & Technology, 2016, 50(20): 11008-11015.
