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<p>Carbon dioxide activated biochar-clay mineral composite efficiently removes ciprofloxacin from contaminated water - Reveals an incubation study</p>
No full textCiprofloxacin, a second-generation synthetic fluoroquinolone derivative widely used in human and veterinary medicines, has the potential to pose a serious risk to aquatic organisms and humans. The current research investigated the removal of ciprofloxacin using biochar treated with clay mineral and subsequently activated with carbon dioxide (CO2) produced at two different pyrolysis temperatures (350 and 650 C). Batch adsorption experiments were carried out to assess the removal efficiency of ciprofloxacin by as-synthesized materials. The effects of various factors, such as pH, contact time, adsorbent dose, initial ciprofloxacin concentration, and temperature were studied during the removal process. The physicochemical characterization results verified the successful loading of clay minerals on biochar. Non-linear adsorption models were employed to understand the nature of adsorption processes however, the Pseudo-second-order kinetic and Freudlich and Redlich Peterson isotherm models best fitted with the adsorption data. These findings indicated that the adsorption did not follow an ideal monolayer adsorption suggesting hybrid chemical adsorption process that was spontaneous and endothermic. The maximum adsorption (50.32 mg g(-1)) of ciprofloxacin was achieved by CO2 activated biochar-clay mineral composite prepared at 350 C, and was almost two times higher than the pristine biochar at neutral pH and 40 C. The possible proposed mechanisms involved for the removal of ciprofloxacin were electrostatic attraction, cation exchange, pore-filling effect, and 7C-7C interactions. Our findings demonstrate that application of CO2 activated biochar-clay mineral composite is a promising technique for efficient removal of ciprofloxacin from aqueous solution
Effect of electron structure on the catalytic activity of LaCoO3 perovskite towards toluene oxidation
No full textLaCoO3 perovskites with different spin states of Co3+ were prepared by calcination at 600-1000 degrees C. LaCoO3 with electron filling in the e(g) orbital at 1 exhibited a moderate interaction between the surface oxygen, resulting in the best catalytic activity. This was verified by the O p-band center
Variations in monsoon precipitation over southwest China during the last 1500 years and possible driving forces
No full textUnderstanding hydroclimatic patterns and their possible driving mechanisms during distinct climate periods over the last 1500 years-such as the Medieval Warm Period (MWP), the Little Ice Age (LIA), and the Current Warm Period-is crucial for predicting future changes to monsoon precipitation in southwest China under global warming scenarios. In this study, based on Pb-210 and Cs-137 dating of surface sediments and AMS C-14 dating of terrestrial plant residues, we establish a robust age model that covers the last similar to 1500 years (AD 439-2012) at Lake Yihai in southwest China. We use analyses of multiple geochemical proxy indices, including loss on ignition at 550 degrees C, total organic carbon, total nitrogen, C/N ratios, and stable carbon isotopes of organic matter to reconstruct changes in summer monsoon precipitation at Lake Yihai during the last similar to 1500 years. The results show that, over southwest China, warm and dry climate conditions prevailed during the MWP (AD 1000-1400) and the past 200 years, whereas conditions during the LIA (AD 1400-1800) were cold and wet. This is consistent with evidence from other geological records over southwest China, such as stalagmite and lake sediment data. Similar hydroclimatic patterns have occurred over the last 1500 years in adjacent tropical/subtropical monsoon regions where the climate is similarly dominated by the Indian summer monsoon (e.g., South China, the South China Sea, Southeast Asia, Northeast India). We suggest that the meridional migration of the mean position of the Inter-tropical Convergence Zone, and El Nino/Southern Oscillation conditions which are linked to tropical Pacific sea surface temperature, are responsible for centennial-scale hydroclimatic patterns over southwest China and adjacent areas during the last 1500 years
Extrapolation of anthropogenic disturbances on hazard elements in PM2.5 in a typical heavy industrial city in northwest China
No full textBaoji is a typical heavy industrial city in northwest China. Its air quality is greatly impacted by the emission from the factories. Elements in fine particulate matter (PM2.5) that are greatly emitted from anthropogenic sources could pose diverse health impacts on humans. In this study, an online AMMS-100 atmospheric heavy metal analyzer was used to quantify 30 elements in PM2.5 under the weak and strong anthropogenic disturbance scenarios before the city lockdown period (from January 9(th) to 23(rd)) and the lockdown period (from January 26(th) to February 9(th)) due to the outbreak of COVID-19 in 2020. During the lockdown period, the average total concentration of total quantified elements was 3475.0 ng/m(3), which was 28% and 33% lower than that of the week and strong anthropogenic disturbance scenarios during the pre-lockdown period. The greatest reductions were found for the elements of chromium (Cr), titanium (Ti), manganese (Mn), and Zinc (Zn), consistent with the industrial structure of Baoji. The mass concentrations of most elements showed obvious reductions when the government post-alerted the industries to reduce the operations and production. Dust, traffic sources, combustion, non-ferrous metal processing, and Ti-related industrial processing that are the contributors of the elements in the pre-lockdown period were apportioned by the positive matrix factorization (PMF) model. Substantial changes in the quantified elements' compositions and sources were found in the lockdown period. Health assessment was conducted and characterized by apportioned sources. The highest non-carcinogenic risk (HQ) was seen for Zn, demonstrating the high emissions from the related industrial activities. The concentration level of arsenic (As) exceeded the incremental lifetime carcinogenic risk (ILCR) in the lockdown period. This could be attributed to the traditional firework activities for the celebration of the Chinese New Year within the lockdown period
Potential paleoceanographic application of cold-water bamboo coral in the South China Sea
No full textUncertainty in the projected changes of Sahel summer rainfall under global warming in CMIP5 and CMIP6 multi-model ensembles
No full textThe Sahel summer rainfall is of great significance to the local social, economic, and cultural environment. In the context of a long Sahel megadrought in the last thirty years of the twentieth century, the future change of Sahel summer rainfall under global warming has aroused wide attention. Based on the historical simulations and high emission scenario experiments from 20 Coupled Model Intercomparison Project phase-5 (CMIP5) models and 22 CMIP6 models, this study investigates the future projections of Sahel summer rainfall under global warming. The results show that the multi-model ensemble (MME) mean projects a slight increase (1-2%/celcius) of summer rainfall over the Sahel in the future which seems to be due to the thermodynamic changes and opposed by the dynamic changes, but that the inter-model spread is due to the latter. We find that, in particular, the inter-model spreads in the extratropical northern and tropical Atlantic sea surface temperature (SST) changes are two important sources of the uncertainty in the Sahel summer rainfall projections via two different atmospheric teleconnection processes. On the one hand, a warmer northern Atlantic SST would induce an anomalous large-scale cyclone over North Africa and Europe, and the southern branch would strengthen the western African monsoonal circulation, leading to a wetter Sahel. On the other hand, a warmer tropical Atlantic SST would weaken the regional circulation, resulting in a drier Sahel. Our results suggest that an improved projection of the future Atlantic warming, especially the differential warming between the northern and tropical Atlantic, is a priority for the reliable future projection of Sahel summer rainfall
A critical review on plasma-catalytic removal of VOCs: Catalyst development, process parameters and synergetic reaction mechanism
No full textIt is urgent to control the emission of volatile organic compounds (VOCs) due to their harmful effects on the environment and human health. A hybrid system integrating non-thermal-plasma and catalysis is regarded as one of the most promising technologies for VOCs removal due to their high VOCs removal efficiency, product selectivity and energy efficiency. This review systematically documents the main findings and improvements of VOCs removal using plasma-catalysis technology in recent 10 years. To better understand the fundamental relation between different aspects of this research field, this review mainly addresses the catalyst development, key influential factors, generation of by-products and reaction mechanism of VOCs decomposition in the plasma-catalysis process. Also, a comparison of the performance in various VOCs removal processes is provided. Particular emphasis is given to the importance of the selected catalyst and the synergy of plasma and catalyst in the VOCs removal in the hybrid system, which can be used as a reference point for future studies in this field
Coupling and decoupling of soil carbon, nitrogen and phosphorus stocks following grazing exclusion in temperate grasslands
No full textGrazing exclusion is considered a crucial measure for improving ecosystem structure and function, including elements such as soil carbon and nutrients. However, little is known about the relationships of soil organic C (SOC), total nitrogen (TN), and total phosphorous (TP) stocks during long-term grazing exclusion. This study examined the SOC, TN, and TP stocks after 0-33 years of grazing exclusion in temperate grasslands on the Loess Plateau, China. The results showed that long-term grazing exclusion significantly increased SOC and TN stocks but declined TP stocks compared to those in grazing grasslands. In addition, grazing exclusion was more favorable for SOC and TN accumulations than TP accretion, and SOC and TN stocks were decoupled from TP stock. Overall, changes in SOC stock were determined by plant productivity, and TN stocks were also driven by soil microbial activities (i.e., N-acquiring enzymes). Nevertheless, plant and microbial characteristics had no effects on TP stocks following grazing exclusion. This study emphasizes the positive effect of grazing exclusion on SOC and TN accumulations, further, it is needed to explore soil phosphorus stabilization mechanisms during grassland restoration after grazing exclusion
Hydroclimatic changes in south-central China during the 4.2 ka event and their potential impacts on the development of Neolithic culture
No full textThe 4.2 ka event is widely presumed to be a globally widespread aridity event and has been linked to several episodes of societal changes across the globe. Whether this climate event impacted the cultural development in south-central China remains uncertain due to a lack of regional paleorainfall records. We present here stalagmite stable carbon isotope and trace element-based reconstruction of hydroclimatic conditions from south-central China. Our data reveal a sub-millennial scale (similar to 5.6 to 4.3 ka) drying trend in the region followed by a gradual transition to wetter conditions during the 4.2 ka event (4.3-3.9 ka). Together with the existing archaeological evidence, our data suggest that the drier climate before 4.3 ka may have promoted the Shijiahe culture, while the pluvial conditions during the 4.2 ka event may have adversely affected its settlements in low-lying areas. While military conflicts with the Wangwan III culture may have accelerated the collapse of Shijiahe culture, we suggest that the joint effects of climate and the region's topography also played important causal roles in its demise
Stable carbon isotopic characteristics of fossil fuels in China
No full textGood knowledge on the stable carbon isotopic composition (delta C-13) of fossil fuels is critical for the estimation of atmospheric CO2 sources. Here, we complied a comprehensive delta C-13 database including 336 coal, 580 oil, and 1160 natural gas data based on the extensive literature search, and conducted field measurements in two megacities, to characterize the delta C-13 signatures of Chinese fossil fuels. Results show that coal exhibits a narrow range and the most enriched in delta C-13 signature, oil displays intermediate variations both in the distribution and value of delta C-13. By contrast, natural gas is strongly depleted but became more enriched in delta C-13 signature due to the shift in production from isotopically light oil-type gas to isotopically heavy coal-type gas. We found an obvious overlap between the delta C-13 distributions of oil and natural gas, and the carbon isotopic difference between oil and natural gas is minimized in Ordos Basin. Therefore, we suggested that the geographic origin is a certain factor that must be considered when delta C-13 of fossil fuels is used to estimate CO2 source contributions, and the measurement of delta(CO2)-C-13 signatures of local end members is a better alternative in the absence of detailed information about the geographical origins of fossil fuels. This work is helpful in improving the ability to quantify CO2 sources of fossil fuel emissions in China, and also make a contribute to the global carbon isotope database. (C) 2021 Elsevier B.V. All rights reserved