It is clear that the density and porosity of biochar will impact its mobility in the environment, its interaction with the soil hydrologic cycle, and its suitability as an ecological niche for soil microorganisms. However, the wide range of biochar pore sizes complicates biochar porosity characterization, making it challenging to find methods appropriate to connect the fundamental physical properties of density and porosity to environmental outcomes. Here, we report the use of two fast, simple density measurement techniques to characterize biochar density and porosity. We measured biochar skeletal density by helium pycnometry and envelope density by displacement of a dry granular suspension. We found that biochar skeletal density ranged from 1.34 g cm−3 to 1.96 g cm−3, and increased with pyrolysis temperature. Biochar envelope density ranged from 0.25 g cm−3 to 0.60 g cm−3, and was higher for wood biochars than grass biochars—a difference we attribute to plant cell structures preserved during pyrolysis. We compared the pore volumes measured by pycnometry with those measured by nitrogen gas sorption and mercury porosimetry. We show that biochar pore volumes measured by pycnometry are comparable to the values obtained by mercury porosimetry, the current benchmark method. We also show that the majority of biochar pore volume is in macropores, and thus, is not measured by gas sorption analysis. These fast, simple techniques can now be used to study the relationship between biochar's physical properties and its environmental behaviors. 相似文献
A direct method for the arylation of 1,2‐azolo[1,5‐a]pyridines has been developed. In the process, the fused pyridines react with aryl halides in the presence of the palladium complex Pd(OAc)2(Phen) as a catalyst and copper(I) chloride (CuCl) as a Lewis acid to form arylated derivatives. While pyrazolo[1,5‐a]pyridines and [1,2,4]triazolo[1,5‐a]pyridines are arylated at ortho‐positions of their pyridine rings using this method, in situ ring‐opening of the formed C‐7 arylated [1,5‐a]pyridine takes place to generate the 2,6‐disubstituted pyridine. Also, upon treatment with lithium diisopropylamide (LDA), C‐7 arylated pyrazolo[1,5‐a]pyridine‐3‐carboxylates react to produce diversely substituted 2,6‐disubstituted pyridines. Finally, a sequential C‐3 arylation was accomplished through a two‐step sequence involving hydrolysis of pyrazolo[1,5‐a]pyridine‐3‐carboxylates followed by the bimetallic Pd/Cu‐catalyzed decarboxylative coupling reaction with aryl bromide.
We previously demonstrated that the organogermanium compound 3-(trihydroxygermyl)propanoic acid (THGP) enhances the enzymatic and alkaline isomerization of an aldose to a ketose through cis-diol complex formation by multiple mechanisms. Its higher affinity for the ketose than the aldose protects the ketose complex from alkaline decomposition. Furthermore, it has been reported that the aldose-ketose alkaline isomerization pathway includes 1,2-enediol. Therefore, we speculated that the complex-forming ability of THGP could also be applied to enediol, a transient intermediate of alkaline isomerization. To test this prediction, we analyzed the initial rates of glucose or lactose isomerization in a region where there was no substantial difference in pH with and without THGP addition. The results showed that THGP enhanced the rate of fructose or lactulose formation per unit time by approximately 2-fold compared to the control. This finding indicated that THGP could form a complex with the transition state of aldose-ketose alkaline isomerization. 相似文献