Comparison of Concrete Carbonation Process under Natural Condition and High CO_2 Concentration Environments

To compare the results obtained under both natural and accelerated environments,the pH values of carbonated concrete were measured,the variation of pH values was determined,and the variations of Ca（OH）2 and CaCO3 contents in the carbonated concrete under natural condition and high CO2 concentration accelerated climate environments were determined by microcosmic test methods such as DTA and X-ray diffraction.The experimental results showed that the overall variation trend of pH values and phase component of carbonation layer of concrete under accelerated climate environments with high CO2 concentrations were the same as those under natural conditions.Therefore,the carbonation processes of concrete were considered consistent under both conditions.However there was a difference in the length of semi-carbonation zones.The one measured under high CO2 concentration accelerated climate environments was shorter than that under natural condition.Experimental investigation showed that it was caused by the differences in climate condition（temperature and relative humidity） as well as the properties of the concrete.The concentration of CO2 and the duration of the carbonation process have no effect on the length of semi-carbonation zone.Thus,it is acceptable to simulate the natural condition by applying the high CO2 concentration artificial accelerated carbonation technique for the purpose of the study of carbonation process of concrete.

A recent update on development,synthesis methods,properties and application of natural products derived carbon dots

Natural resources are practically infinitely abundant in nature,which stimulates scientists to create new materials with inventive uses and minimal environmental impact.Due to the various benefits of natural carbon dots(NCDs)from them has received a lot of attention recently.Natural products-derived carbon dots have recently emerged as a highly promising class of nanomaterials,showcasing exceptional properties and eco-friendly nature,which make them appealing for diverse applications in various fields such as biomedical,environmental sensing and monitoring,energy storage and conversion,optoelectronics and photonics,agriculture,quantum computing,nanomedicine and cancer therapy.Characterization techniques such as Photoinduced electron transfer,Aggregation-Induced-Emission(AIE),Absorbance,Fluorescence in UV-Vis and NIR Regions play crucial roles in understanding the structural and optical properties of Carbon dots(CDs).The exceptional photoluminescence properties exhibited by CDs derived from natural products have paved the way for applications in tissue engineering,cancer treatment,bioimaging,sensing,drug delivery,photocatalysis,and promising remarkable advancements in these fields.In this review,we summarized the various synthesis methods,physical and optical properties,applications,challenges,future prospects of natural products-derived carbon dots etc.In this expanding sector,the difficulties and prospects for NCD-based materials research will also be explored.

A Global Ocean Biogeochemistry General Circulation Model and its Simulations

An ocean biogeochemistry model was developed and incorporated into a global ocean general circulation model （LICOM） to form an ocean biogeochemistry general circulation model （OBGCM）. The model was used to study the natural carbon cycle and the uptake and storage of anthropogenic CO2 in the ocean. A global export production of 12.5 Pg C yr-1 was obtained. The model estimated that in the pre-industrial era the global equatorial region within ~15~ of the equator released 0.97 Pg C yr-1 to the atmosphere, which was balanced by the gain of CO2 in other regions. The post-industrial air sea CO2 flux indicated the oceanic uptake of CO2 emitted by human activities. An increase of 20-50 ~mol kg-1 for surface dissolved inorganic carbon （DIC） concentrations in the 1990s relative to pre-industrial times was obtained in the simulation, which was consistent with data-based estimates. The model generated a total anthropogenic carbon inventory of 105 Pg C as of 1994, which was within the range of estimates by other researchers. Various transports of both natural and anthropogenic DIC as well as labile dissolved organic carbon （LDOC） were estimated from the simulation. It was realized that the Southern Ocean and the high-latitude region of the North Pacific are important export regions where accumulative air-sea CO2 fluxes are larger than the DIC inventory, whereas the subtropical regions are acceptance regions. The interhemispheric transport of total natural carbon （DIC＋LDOC） was found to be northward （0.11 Pg C yr-1）, which was just balanced by the gain of carbon from the atmosphere in the Southern Hemisphere.

Soil Organic Carbon Contents and Stocks in Coastal Salt Marshes with Spartina alterniflora Following an Invasion Chronosequence in the Yellow River Delta,China

Plant invasion alters the fundamental structure and function of native ecosystems by affecting the biogeochemical pools and fluxes of materials and energy. Native(Suaeda salsa) and invasive(Spartina alterniflora) salt marshes were selected to study the effects of Spartina alterniflora invasion on soil organic carbon(SOC) contents and stocks in the Yellow River Delta. Results showed that the SOC contents(g/kg) and stocks(kg/m^2) were significantly increased(P < 0.05) after Spartina alterniflora invasion of seven years, especially for the surface soil layer(0–20 cm). The SOC contents exhibited an even distribution along the soil profiles in native salt marshes, while the SOC contents were gradually decreased with depth after Spartina alterniflora invasion of seven years. The natural ln response ratios(Ln RR) were applied to identify the effects of short-term Spartina alterniflora invasion on the SOC stocks. We also found that Spartina alterniflora invasion might cause soil organic carbon losses in a short-term phase(2–4 years in this study) due to the negative Ln RR values, especially for 20–60 cm depth. And the SOCD in surface layer(0–20 cm) do not increase linearly with the invasive age. Spearman correlation analysis revealed that silt + clay content was exponentially related with SOC in surface layer(Adjusted R^2 = 0.43, P < 0.001), suggesting that soil texture could play a key role in SOC sequestration of coastal salt marshes.

Comparison of different combined treatment processes to address the source water with high concentration of natural organic matter during snowmelt period

The source water in one forest region of the Northeast China had very high natural organic matter（NOM） concentration and heavy color during snowmelt period. The efficiency of five combined treatment processes was compared to address the high concentration of NOM and the mechanisms were also analyzed. Conventional treatment can hardly remove dissolved organic carbon（DOC） in the source water. KMn O4pre-oxidization could improve the DOC removal to 22.0%. Post activated carbon adsorption improved the DOC removal of conventional treatment to 28.8%. The non-sufficient NOM removal could be attributed to the dominance of large molecular weight organic matters in raw water, which cannot be adsorbed by the micropore upon activated carbon. O3＋ activated carbon treatment are another available technology for eliminating the color and UV254 in water. However, its performance of DOC removal was only 36.4%, which could not satisfy the requirement for organic matter. The limited ozone dosage is not sufficient to mineralize the high concentration of NOM. Magnetic ion-exchange resin combined with conventional treatment could remove 96.2%of color, 96.0% of UV254 and 87.1% of DOC, enabling effluents to meet the drinking water quality standard. The high removal efficiency could be explained by the negative charge on the surface of NOM which benefits the static adsorption of NOM on the anion exchange resin. The results indicated that magnetic ion-exchange resin combined with conventional treatment is the best available technology to remove high concentration of NOM.

Propagation of surfactant and polymer flow in natural carbonate cores

This paper presents an experimental and analytical study of comprehensive effects of surfactant and polymer in aqueous solutions on the propagation in carbonates.Single-phase flow tests of surfactant,polymer and surfactant-polymer mixture were respectively conducted on natural carbonate core plugs at high temperature and high salinity reservoir conditions.The effect of different factors on chemical propagation was taken into account by use of a convection-dispersion model.The dynamic adsorptions of two amphoteric surfactants at 2000 mg/L concentration onto the carbonate rocks were 0.21 and 0.17 mg/g-rock,respectively.The dynamic adsorptions of a sulfonated polymer at 2000 and 5000 mg/L were 0.11 and 0.17 mg/g-rock,respectively.Surfactant-polymer mixtures in aqueous solutions were coinjected to evaluate their competitive adsorption,showing the surfactant adsorption was reduced by approximately 50%.The dispersion coefficient of the chemicals in the carbonate cores was in the magnitude of 10^(-3) cm^(2)/s.Caused by dispersion and adsorption,chemical concentration reduction occurred obviously during the propagation in carbonate porous media.Chromatographic separation took place in the surfactant-polymer co-injection scheme,which was estimated by modeling as well.

Effects of long-term nitrogen addition on theδ^(15)N andδ^(13)C of Larix gmelinii and soil in a boreal forest

Background:Natural abundance of carbon(C)and nitrogen(N)stable isotope ratios(δ^(13)C andδ^(15)N)has been used to indicate the state and cycle of ecosystem C and N.However,it is still unclear how C and N cycle of boreal forests respond to the N deposition.Results:We conducted an 8-year continuous N addition field experiment in a Larix gmelinii forest in Greater Khingan Mountains,Northeast China.Four N treatments(0,25,50,75 kg N ha^(−1)year^(−1))were built.The effects of N addition on theδ^(13)C andδ^(15)N of needle,branch,bark,and fine root of Larix gmelinii and soil were studied.The result of the balance between the N input and output flux showed that N addition significantly increased theδ^(15)N in each organ of Larix gmelinii,but did not change theδ^(15)N of soil.We also found that the N absorption by needles of Larix gmelinii could increase the needle photosynthesis rate andδ^(13)C by increasing carboxylation,but N addition had no significant effect on theδ^(13)C of soil and other organs.In addition,both the soilδ^(15)N andδ^(13)C increased with the soil depth.Conclusions:Long-term N addition may lead to more open C and N cycles and further affect plant nutrient acquisition strategies in boreal forest ecosystems.