| 摘要: |
| 为全面探索河流溶解性有机碳（DOC）与二氧化碳（CO2）动态及驱动因素的相关关系，该研究以我国三峡库区河流—澎溪河为对象，于雨季和旱季采集表层水体水样，分别通过原位和室内测定，明确了水文参数[水温（T）、pH、碱度（Alk）和流速（w）]、DOC浓度和营养元素[总氮（TN）和总磷（TP）]浓度，并计算了水体CO2分压（pCO2）、水-气界面CO2交换通量（F）和营养元素化学计量比（DOC:TN、DOC:TP和TN:TP）。以河流CO2、DOC和营养状态动态变化为基础，通过对DOC、TN、TP、营养元素化学计量比和荧光峰（B、T、A、M、C、D和N）与河流pCO2的多维分析建立及评估了潜在的耦合关系，从而揭示特定区域河流CO2的来源与驱动因素特征。结果显示，澎溪河水-气界面CO2交换速率（k）在3.75~22.9 m/d范围内，雨季[（9.91 ± 4.93）m/d] > 旱季[（6.69 ± 4.30）m/d，P < 0.05]，pCO2在65.95~20642.41 μatm范围内，F平均值为（629.4 ± 1426.8）mmol/m2/d，河流总体表现为大气CO2源。水体DOC总体在1.42~7.88 mg/L范围内，且旱季[（4.50 ± 0.17）mg/L]>雨季[（2.87 ± 0.18）mg/L，P < 0.05]，TN在0.176~1.917 mg/L范围内，旱季[（1.205 ± 0.353）mg/L]>雨季[（0.665 ± 0.306）mg/L，P < 0.05]，TP在0.0003~0.169 mg/L范围内。在该流域雨季，类酪氨酸、类色氨酸和土壤富里酸占比显著高于旱季（P < 0.001），而类腐殖质、微生物衍生腐殖质和生物生产力占比显著低于旱季（P < 0.001）。旱季水体pCO2与TP显著正相关，与营养元素化学计量比（TN：TP和DOC：TP）显著负相关，而雨季与生物生产力显著负相关，营养状态与pCO2存在季节耦合关系。生物代谢过程是河流CO2饱和的主要原因，而降雨能够促进这一内在联系。 |
| 关键词: 三峡库区 河流二氧化碳 营养元素 主成分分析 荧光峰 |
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| 基金项目:国家自然科学基金项目(4210709)、重庆市自然科学基金面上项目 (NO. CSTB2022NSCQ-MSX1046)、贵州省科技厅科学技术(黔科合基础-ZK [2021]一般226)和贵州省教育厅青年科技人才成长项目 (黔教合KY字 [2021] 114)联合资助。 |
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| Deciphering Riverine CO2 Dynamics and Driving Factors Coupled with DOC and Nutrient Status |
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ZHANG Yi,WANG Han,MA Yong-mei,DU Jia-jie,LONG Jing-xiao,LANG Jia-rui,NI Mao-fei
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: College of Eco-Environmental Engineering,Guizhou Minzu University
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| Abstract: |
| To comprehensively explore the correlation between dissolved organic carbon (DOC) and carbon dioxide (CO2) dynamics and their driving factors in rivers, this study focused on the Pengxi River in the Three Gorges Reservoir Area of China. Surface water samples were collected during the rainy and dry seasons. The parameters such as water temperature (T), pH, alkalinity (Alk), and flow velocity (w), along with DOC concentration and nutrients [total nitrogen (TN) and total phosphorus (TP)] concentrations, were determined both in-situ and in the laboratory. The partial pressure of CO2 in the water body (pCO2), CO2 flux across the water-air interface (F), and the stoichiometric ratios of nutrients (DOC:TN, DOC:TP, and TN:TP) were calculated. Based on the dynamics of CO2, DOC, and nutrient status in the river, a multidimensional analysis was conducted to establish and evaluate potential coupling relationships between DOC, TN, TP, nutrient stoichiometric ratios, and fluorescence peaks (B, T, A, M, C, D, and N) with river pCO2. This approach aimed to reveal the characteristics of CO2 sources and driving factors in specific regional rivers. We show that gas transfer velocity of CO2 (k) ranged from 3.75 to 22.9 m/d, which was higher in the wet season [(9.91 ± 4.93) m/d] than that in the dry season [(6.69 ± 4.30) m/d, P < 0.05]. River pCO2 varied between 65.95-20642.41 μatm, yield an overall CO2 flux of (629.4 ± 1426.8) mmol/m2/d. Aquatic DOC ranged within 1.42-7.88 mg/L, with a higher concentration in the dry season [(4.50 ± 0.17) mg/L] in comparison to the wet season [(2.87 ± 0.18) mg/L, P < 0.05]. Similarly, TN ranged from 0.176 to 1.917 mg/L, with a higher concentration in the dry season [(1.205 ± 0.353) mg/L] compared to the wet season [(0.665 ± 0.306) mg/L, P < 0.05]. The overall TP concentrations were in the range of 0.0003-0.169 mg/L. The proportions of tyrosine-like compounds, tryptophan-like compounds, and fulvic acids were significantly higher in the wet season than the dry season (P < 0.001), while we observed the higher humic acids, microbial-derived humic acids and biological productivity in the dry season compared to wet season (P < 0.001). During the dry season, the partial pressure of CO2 in the water body (pCO2) shows a significant positive correlation with total phosphorus (TP), and a significant negative correlation with the stoichiometric ratios of nutrients (TN:TP and DOC:TP). In contrast, during the rainy season, there is a significant negative correlation with biological productivity. This indicates a seasonal coupling relationship between nutrient status and pCO2. These observations highlight that biological metabolism highly constrained CO2 supersaturation in the river, and seasonal rainfall modulated the causal relationship. |
| Key words: Three Gorges Reservoir area Riverine Carbon Dioxide Nutrient Elements Principal Component Analysis Fluorescence Peaks |
