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11.
电化学法快速测定茶多酚含量的研究 总被引:1,自引:0,他引:1
基于电化学循环伏安法,讨论了3种低成本自制工作电极——银电极、碳糊电极和玻碳电极在茶多酚含量测定应用上的可行性。通过分析茶多酚在电极表面的氧化还原行为,发现所制银电极不适宜检测茶多酚,碳糊电极、玻碳电极的氧化电流峰值与茶多酚含量有良好的线性关系。所制玻碳电极测定绿茶茶样中的茶多酚含量的重复性和准确性较碳糊电极好。与国标方法相比,碳糊电极、玻碳电极检测茶多酚所需时间大大缩短。结果表明,电化学方法可应用于茶多酚含量的快速测定,从而为快速、低价、便捷检测茶多酚提供一条新思路。 相似文献
12.
Salwa Hamdi Nadhira Ben Aïssa Tahar Gallali Martial Bernoux 《Soil biology & biochemistry》2011,43(9):1752-1758
Quantification of microbial activities involved in soil organic carbon (SOC) decomposition is critical for the prediction of the long-term impact of climate change on soil respiration (SR) and SOC stock. Although the temperature sensitivity of SR is especially critical in semi-arid regions, such as North West Tunisia, where the SOC stock is low, little research has been carried out in these environments. More needs to be known about factors, such as SOC availability that influence temperature sensitivity. In this study, soil samples were incubated with and without glucose addition for 28 days after a 28-day pre-incubation period. Pre-incubation and incubation was carried out at 20 °C, 30 °C, 40 °C and 50 °C. Respiration measurements were taken with temperature, glucose addition and incubation time as independent variables. The highest pre-incubation temperature reduced the temperature sensitivity of SR during the subsequent incubation period, both with and without glucose addition. Soil samples pre-incubated at 50 °C had the lowest SR at all subsequent incubation temperatures and the lowest temperature sensitivity of SR, even after glucose addition. However, after glucose addition, the effect of a high pre-incubation temperature on soil respiration lasted only two days. Measuring the water-soluble carbon (WSC) in soil samples suggested that the high pre-incubation temperature may have killed part of the microbial biomass, modified microbial communities or solubilized SOC. For quantifying the possible effect of global warming, in particular heat waves, on soil respiration in the soil studied, the results indicate a moderate response of soil respiration to temperature at high temperatures, as shown by Q10 close to 1.7, even in the range 40-50 °C. 相似文献
13.
Marcos Siqueira-Neto Gustavo Vicentini Popin Marisa C. Piccolo Marc Corbeels Eric Scopel Plínio B. Camargo Martial Bernoux 《European Journal of Soil Science》2021,72(3):1431-1446
The Brazilian Cerrado is a large and expanding agricultural frontier, representing a hotspot of land-use change (LUC) from natural vegetation to farmland. It is known that this type of LUC impacts soil organic matter (SOM) dynamics, particularly labile carbon (C) pools (living and non-living), decreasing soil health and agricultural sustainability, as well as increasing soil greenhouse gas (GHG) emissions, and accelerating global climate change. In this study, we quantified the changes in the quantity and quality of SOM and GHG fluxes due to changes in land use and cropland management in the Brazilian Cerrado. The land uses studied were native vegetation (NV), pasture (PA) and four croplands, including the following management types: conventional tillage with a single soybean crop (CT), and three no-tillage systems with two crops cultivated in the same year (i.e., soybean/sorghum (NTSSo), soybean/millet (NTSMi) and maize/sorghum (NTMSo)). Soil and gases were sampled in the rainy season (November, December and January) and dry season (May, July and September). The highest soil C and nitrogen (N) stocks (6.7 kg C m−2 and 0.5 kg N m−2, 0–0.3-m layer) were found under NV. LUC reduced C stocks by 25% in the CT and by 10% in the PA and NT. Soil N stocks were 30% lower in the PA and NTMSo and 15% lower in the croplands with soybean compared to NV. δ13C values clearly distinguished between the C-origin from NV (−25‰) and that from other land uses (−16‰). Soil (0–0.1 m) under NV also presented higher labile-C (625 g C m−2), microbial-C (70 g C m−2) and microbial-N (5.5 g N m−2), whereas other land uses presented values three times lower. GHG emissions (expressed as C-equivalent) were highest in the NV (1.2 kg m−2 year−1), PA (1.3 kg m−2 year−1) and NTMSo (0.9 kg m−2 year−1) and were positively related to the higher SOM turnover in these systems. Our results suggest that in order to maintain SOM, it is necessary to adopt “best” management practices, that provide large plant residue inputs (above- and belowground). This can be seen as a pathway to achieving high food production with low GHG emissions. 相似文献
14.
Joshua R. van Lier Shaun K. Wilson Martial Depczynski Lucy N. Wenger Christopher J. Fulton 《Landscape Ecology》2018,33(8):1287-1300