Aquatic photosynthetic carbon pump driven by periodic temperature variations affects dissolved inorganic carbon and hydrochemical characteristics in a groundwater-fed reservoir.

Under the influence of periodic temperature variations, biogeochemical cycling in water bodies is markedly affected by the periodic thermal stratification processes in subtropical reservoirs or lakes. In current studies, there is insufficient research on the influence and mechanism of dissolved inorganic carbon (DIC) distribution in karst carbon-rich groundwater-fed reservoirs under the coupled effects of thermal structure stratification and the biological carbon pump (BCP) effect. To address this issue, the Dalongdong (DLD) reservoir in the subtropical region of southern China was chosen as the site for long-term monitoring and research on relevant physicochemical parameters of water, DIC, and its stable carbon isotope (δ13CDIC), CO2 emission flux, as well as the reservoir's thermal stratification index. The results show that: (1) the DLD reservoir is a typical warm monomictic reservoir, which exhibits regular variations of mixing period-stratification period-mixing period on a yearly scale due to thermal structure changes; (2) DIC was consumed by aquatic photosynthetic organisms in the epilimnion during the stratification period, leading to a decrease in DIC concentration, partial pressure of CO2 (pCO2) and CO2 emission flux, and an increase in stable carbon isotope (δ13CDIC). During the mixing period, the trend was reversed; (3) During the thermal stratification, aquatic photosynthesis and water temperature were the primary factors controlling DIC variations in both the epilimnion and thermocline. Regarding the hypolimnion, calcite dissolution, organic matter decomposition, and water temperature were the dominant controlling factors. These results indicate that although carbon-rich karst groundwater provides a plentiful supply of DIC in the DLD reservoir, its availability is still influenced by variations in the reservoir's thermal structure and the metabolic processes of aquatic photosynthetic organisms. Therefore, to better estimate the regional carbon budget in a reservoir or lake, future studies should especially consider the combined effects of BCP and thermal structure variations on carbon variations.

High-frequency dynamics of CO2 emission flux and its influencing factors in a subtropical karst groundwater-fed reservoir, south China.

Revealing the magnitude, dynamics, and influencing factors of CO2 emissions across the water-air interface in karst water with high frequency is crucial for accurately assessing the carbon budget in a karst environment. Due to the limitations of observation methods, the current research is still very insufficient. To solve the above problems and clarify the main influencing factors of CO2 emission in karst water, this study selected Dalongdong (DLD) Reservoir, located in the typical karst peak and valley area in southwest China, to carry out a multi-parameter high-frequency monitoring study from January to December 2021, and used the thin boundary model method to estimate the CO2 flux across the water-air interface (CF). The average annual flux of DLD reservoir is 84.48 mmol·(m2·h)-1, which represents a CO2 source overall. However, during the stratification period in August, there is a transient carbon sink due to negative CO2 emission. The alteration of thermal stratification in water is crucial in regulating the seasonal variation of CF. Meanwhile, the diurnal variation is significantly influenced by changes in hydrochemical parameters during the thermal stratification stage. Compared to low wind speeds (<3 m/s), high wind speeds (≥3 m/s) have a greater impact on the CO2 flux. Furthermore, high-frequency continuous data revealed that the reservoir triggered a CO2 pulse emission during the turnover process, primarily at night, leading to unusually high CO2 flux values. It is of great significance to monitor and reveal the process, flux, and control factors of CO2 flux in land water at a high-frequency strategy. They will help improve the accuracy of regional or watershed carbon budgets and clarify the role of global land water in the global carbon budget.

[Extract of Herba Siegesbeckiae on mouse rheumatoid arthritis induced by anthrogen-CIA monoclonal antibody].

OBJECTIVE: To investigate the anti-inflammatory effect of Herba Siegesbeckiae extracts on mouse rheumatoid arthritis induced by arthrogen-CIA monoclonal antibody. METHODS: The rheumatoid arthritis was induced by arthrogen-CIA arthritogenic monoclonal antibody in mice. The sandwich enzyme-linked immunosorbent assay was used to determine the concentration of IL-1ßin mouse serum,and the content of IL-6,IL-17 and MMP-3 in supernatant of tissue homogenate of hind limb below the stifle of mice. One-way ANOVA was used for data analysis. RESULTS: The toe swelling was attenuated in Siegesbeckiae group than that in model group [(0.218 ± 0.0307)cm(3) compared with (0.2545 ± 0.0179)cm(3), P<0.05]. The serum IL-1ß level in Siegesbeckiae group was lower than that in model group [(63.74 ± 21.74)pg/ml compared with (104.96 ± 31.22)pg/ml, P<0.01]. The contents of IL-6, IL-17 and MMP-3 in tissue supernatants of Siegesbeckiae group were all lower than those of model group [(171.10 ± 48.35)pg/ml compared with (249.64 ± 75.08)pg/ml, P<0.05; (115.42 ± 56.52)pg/ml compared with (208.40 ± 88.54)pg/ml, P<0.05;(3660.31 ± 1680.99) pg/ml compared with (5420.79 ± 1201.43)pg/ml, P<0.05, respectively]. CONCLUSION: The extract of Herba Siegesbeckiae has anti-inflammatory effect on mouse rheumatoid arthritis induced by mixed arthrogen monoclonal antibody.