Phytolith remains of rice (Oryza sativa L.) recovered from the Shangshan site in the Lower Yangtze of China have previously been recognized as the earliest examples of rice cultivation. However, because of the poor preservation of macroplant fossils, many radiocarbon dates were derived from undifferentiated organic materials in pottery sherds. These materials remain a source of debate because of potential contamination by old carbon. Direct dating of the rice remains might serve to clarify their age. Here, we first validate the reliability of phytolith dating in the study region through a comparison with dates obtained from other material from the same layer or context. Our phytolith data indicate that rice remains retrieved from early stages of the Shangshan and Hehuashan sites have ages of approximately 9,400 and 9,000 calibrated years before the present, respectively. The morphology of rice bulliform phytoliths indicates they are closer to modern domesticated species than to wild species, suggesting that rice domestication may have begun at Shangshan during the beginning of the Holocene.

Phytoliths are noncrystalline minerals that form inside cells and cell walls of different parts of plants. Organic carbon in living cells can be occluded in phytoliths during plant growth. It has been documented that the occluded carbon within phytoliths is an important long-term terrestrial carbon reservoir that has a major role in the global carbon cycle. Common millet and foxtail millet have become typical dry-farming crops in China since the Neolithic Age. The study of carbon conservation within phytoliths in these crops could provide insights into anthropogenic influences on the carbon cycle. In this study, we analyzed the carbon content in phytoliths of common millet and foxtail millet. The results indicated that (1) common millet and foxtail millet contained 0.136% ± 0.070% and 0.129% ± 0.085% phytolith-occluded carbon (PhytOC) on a dry mass basis, respectively; (2) based on the mean annual production of common millet and foxtail millet in the last 10 years, the phytolith occluded carbon accumulation rate of common millet and foxtail millet was approximately 0.023 ± 0.015 and 0.020 ± 0.010 t CO 2 ha 1 a 1 , respectively; (3) assuming a similar phytolith occluded carbon accumulation rate as for common millet (the highest accumulation rate was 0.038 t CO 2 ha 1 a 1 ), this could result in the sequestration of 2.37 × 10 6 t CO 2 per year for the 62.4 × 10 6 ha dry-farming crops in China. Although there was a decline in the annual production rate and planting area of foxtail millet during 1949 to 2008, the total phytolith carbon sequestration rate was 7×10 6 t CO 2 within the 60-year period. However, phytolith occluded carbon has not yet been fully considered as a global carbon sink. Also, this carbon fraction is probably one of the best candidates for the missing carbon sink.phytoliths, carbon sequestration, dry-farming, phytolith occluded carbon, PhytOC Citation: Zuo X X, Lü H Y. Carbon sequestration within millet phytoliths from dry-farming of crops in China.

2,5-furandicarboxylic acid (FDCA) is a valuable non-phthalate biomass-based plastic precursor with the potential to replace terephthalic acid (TPA) in a variety of polymer applications. In this work, the Co/Mn/Br catalyzed semi-continuous oxidation of 5hydroxymethylfurfural (HMF) to FDCA has been carried out at temperatures lower than those of the traditional Mid-Century (MC) process. As HMF is more susceptible to side reactions (e.g. the over-oxidation to CO and CO 2 ), lower temperatures compared to the MC process are typically used to prevent substrate burning. However, lower temperatures afford much decreased FDCA yield compared to that of TPA in p-xylene oxidation. Therefore, optimization of other operating variables such as catalyst composition, water concentration in the acetic acid solvent and pressure are essential to maximize FDCA yield. Using such optimization, we show that the FDCA yield can be enhanced to 90% at 1/0.015/0.5 molar ratio of Co, Mn and Br, 7% (v/v) water, 30 bar (CO 2 /O 2 = 1/1, mol/mol) and 180 o C, the highest value reported for HMF oxidation using Co/Mn/Br catalyst. The use of Zr(IV) as co-catalyst facilitates FDCA formation, but only at lower temperatures (120-160 °C) where the FDCA yield is compromised. These findings broaden the scope of the application of the industrial MC catalytic process for FDCA production. use) by 65%. As a result, FDCA has been identified by DOE as one of the top twelve building blocks for the future green chemicals industry. 12, 13 The oxidation of HMF to FDCA was originally carried out in presence of strong oxidants, such as nitric acid or KMnO 4 . 2,14 Apart from environmental concerns, these systems produced only modest FDCA yield owing to substrate destruction under the harsh oxidizing conditions. Alternatively, oxidation with molecular oxygen, a much milder and cleaner oxidant, has been developed, employing noble metals such as platinum, 15-20 gold 21-27 and Pd 28-33 as active catalysts.During the past five years, these heterogeneous catalytic systems have been extensively studied and shown to provide nearly quantitative FDCA yield at relatively mild reaction temperatures (65-130 °C). However, because of its low solubility in the reaction medium, FDCA tends to precipitate out in the course of reaction, which might not only deactivate the catalysts by blocking the active sites but also causes separation problems. For this reason, sodium hydroxide is added in some cases to convert the diacid product into its sodium salt, which, after removal of the catalysts, must be treated with a strong acid for recovery of FDCA. 18,23,24 More recently, several base-free processes have been reported by using hydrotalcite-supported gold nanoparticles, 25 carbon nanotube-supported gold-palladium alloy nanoparticles 34 , covalent triazine supported ruthenium 35 and magnetic Fe 3 O 4 −CoO x 36 as catalysts. Nevertheless, even in these cases, the substrate (HMF) concentration needs to be maintained very low to avoid FDCA precipitation. The potential for practical appl...

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2,5‐furandicarboxylic acid (FDCA) is a potential non‐phthalate based bio‐renewable substitute for terephthalic acid‐based plastics. Herein, we present an investigation of the oxidation rate of 5‐hydroxymethylfurfural (HMF) to FDCA in acetic acid medium using Co/Mn/Br catalyst. Transient concentration profiles of the reactant (HMF), intermediates [2,5‐diformylfuran (DFF), 5‐formyl‐2‐furancarboxylic acid (FFCA)], and the desired product (FDCA) were obtained for this relatively fast reaction in a stirred semi‐batch reactor using rapid in‐line sampling. Comparison of the effective rate constants for the series oxidation steps with predicted gas–liquid mass transfer coefficients reveals that except for the FFCA → FDCA step, the first two oxidation steps are subject to gas–liquid mass transfer limitations even at high stirrer speeds. Novel reactor configurations, such as a reactor in which the reaction mixture is dispersed as fine droplets into a gas phase containing oxygen, are required to overcome oxygen starvation in the liquid phase and further intensify FDCA production. © 2016 American Institute of Chemical Engineers AIChE J, 63: 162–171, 2017

Bulliform phytoliths play an important role in researching rice origins as they can be used to distinguish between wild and domesticated rice. Rice bulliform phytoliths are characterized by numerous small shallow fish-scale decorations on the lateral side. Previous studies have shown that domesticated rice has a larger number of these decorations than wild rice and that the number of decorations ≥9 is a useful feature for identifying domesticated rice. However, this standard was established based on limited samples of modern rice plants. In this study, we analyzed soil samples from both wild and domesticated rice paddies. Results showed that, in wild rice soil samples, the proportion of bulliform phytoliths with ≥9 decorations was 17.46% ± 8.29%, while in domesticated rice soil samples, the corresponding proportion was 63.70% ± 9.22%. This suggests that the proportion of phytoliths with ≥9 decorations can be adopted as a criterion for discriminating between wild and domesticated rice in prehistoric soil. This indicator will be of significance in improving the application of fish-scale decorations to research into rice origins and the rice domestication process.

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