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1. Sensitivity of grassland carbon pools to plant diversity, elevated CO ₂ , and soil nitrogen addition over 19 years

   https://doi.org/10.1073/pnas.2016965118  

   Pastore, Melissa A.; Hobbie, Sarah E.; Reich, Peter B. (April 2021, Proceedings of the National Academy of Sciences)

   Whether the terrestrial biosphere will continue to act as a net carbon (C) sink in the face of multiple global changes is questionable. A key uncertainty is whether increases in plant C fixation under elevated carbon dioxide (CO₂) will translate into decades-long C storage and whether this depends on other concurrently changing factors. We investigated how manipulations of CO₂, soil nitrogen (N) supply, and plant species richness influenced total ecosystem (plant + soil to 60 cm) C storage over 19 y in a free-air CO₂enrichment grassland experiment (BioCON) in Minnesota. On average, after 19 y of treatments, increasing species richness from 1 to 4, 9, or 16 enhanced total ecosystem C storage by 22 to 32%, whereas N addition of 4 g N m⁻²⋅ y⁻¹and elevated CO₂of +180 ppm had only modest effects (increasing C stores by less than 5%). While all treatments increased net primary productivity, only increasing species richness enhanced net primary productivity sufficiently to more than offset enhanced C losses and substantially increase ecosystem C pools. Effects of the three global change treatments were generally additive, and we did not observe any interactions between CO₂and N. Overall, our results call into question whether elevated CO₂will increase the soil C sink in grassland ecosystems, helping to slow climate change, and suggest that losses of biodiversity may influence C storage as much as or more than increasing CO₂or high rates of N deposition in perennial grassland systems. 

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2. HPLC and 32P ‐radiolabeling method for quantification of microbial adenylate concentrations and turnover rates in seawater

   https://doi.org/10.1002/lom3.10499  

   Lanpher, Kaycie B.; Popendorf, Kimberly J. (July 2022, Limnology and Oceanography: Methods)

   Abstract We optimized a high throughput method to quantify turnover rates of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) in marine microbes from simultaneous measures of the respective stocks and phosphorylation rates. We combined a microbial adenylate extraction method using boiling 20 mM Tris buffer with purification and analysis by high pressure liquid chromatography optimized to quantify these intracellular adenylate concentrations in marine microbes. Additionally, we incorporated radiolabeled phosphate (³²P_i) incubations to quantify phosphorus (P) uptake rates and the phosphorylation rates for these adenylate compounds in microbial cells. With this method, we can directly assess the variations in microbial growth rates, metabolic turnover rates, energy charge, and adenylate storage. We applied and validated this method application with environmental samples from Biscayne Bay, Florida, and quantified adenylate turnover times of 12, 15, and 73 min, for ATP, ADP, and AMP, respectively. Future incorporation of this method into experiments and geographic surveys across marine environments will allow for direct assessments of changes in microbial metabolic activity in relation to other ecological variables. 

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3. Proton‐Mediated and Ir‐Catalyzed Iron/Iron‐Oxide Redox Kinetics for Enhanced Rechargeability and Durability of Solid Oxide Iron–Air Battery

   https://doi.org/10.1002/advs.202203768  

   Tang, Qiming; Morey, Chaitali; Zhang, Yongliang; Xu, Nansheng; Sun, Shichen; Huang, Kevin (August 2022, Advanced Science)

   Abstract Long duration energy storage (LDES) is an economically attractive approach to accelerating clean renewable energy deployment. The newly emerged solid oxide iron–air battery (SOIAB) is intrinsically suited for LDES applications due to its excellent low‐rate performance (high‐capacity with high efficiency) and use of low‐cost and sustainable materials. However, rechargeability and durability of SOIAB are critically limited by the slow kinetics in iron/iron‐oxide redox couples. Here the use of combined proton‐conducting BaZr_0.4Ce_0.4Y_0.1Yb_0.1O₃(BZC4YYb) and reduction‐promoting catalyst Ir to address the kinetic issues, is reported. It is shown that, benefiting from the facilitated H⁺diffusion and boosted FeO_x‐reduction kinetics, the battery operated under 550 °C, 50% Fe‐utilization and 0.2 C, exhibits a discharge specific energy density of 601.9 Wh kg^–1‐Fe with a round‐trip efficiency (RTE) of 82.9% for 250 h of a cycle duration of 2.5 h. Under 500 °C, 50% Fe‐utilization and 0.2 C, the same battery exhibits 520 Wh kg^–1‐Fe discharge energy density with an RTE of 61.8% for 500 h. This level of energy storage performance promises that SOIAB is a strong candidate for LDES applications. 

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4. Hydrologic Export of Soil Organic Carbon: Continental Variation and Implications

   https://doi.org/10.1029/2021GB007161  

   Hararuk, O.; Jones, S. E.; Solomon, C. T. (June 2022, Global Biogeochemical Cycles)

   Abstract Soil is the largest terrestrial carbon (C) reservoir and a large potential source or sink of atmospheric CO_₂. Soil C models have usually focused on refining representations of microbe‐mediated C turnover, whereas lateral hydrologic C fluxes have largely been ignored at regional and global scales. Here, we provide large‐scale estimates of hydrologic export of soil organic carbon (SOC) and its effects on bulk soil C turnover rates. Hydrologic export of SOC ranged from nearly 0 to 12 g C m⁻²yr⁻¹amongst catchments across the conterminous United States, and total export across this region was 14 (95% CI 4‐41) Tg C/yr. The proportion of soil C turnover attributed to hydrologic export ranged from <1% to 20%, and averaged 0.97% (weighted by catchment area; 95% CI 0.3%–2.6%), with the lowest values in arid catchments. Ignoring hydrologic export in C cycle models might lead to overestimation of SOC stocks by 0.3–2.6 Pg C for the conterminous United States. High uncertainty in hydrologic C export fluxes and potentially substantial effects on soil C turnover illustrate the need for research aimed at improving our mechanistic understanding of the processes regulating hydrologic C export. 

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5. A High‐Performance Symmetric Supercapacitor from Porous Activated Carbon under Compression

   https://doi.org/10.1002/ente.202100068  

   Sun, Wei; Zhang, Yulin; Yang, Fuqian (April 2021, Energy Technology)

   The realization of biomass‐derived supercapacitors of high performance is of practical importance for the manufacturing of supercapacitors from green and renewable sources. Herein, the feasibility of constructing high‐performance supercapacitors from potato‐derived activated carbon (AC) is demonstrated. The potato‐derived AC is produced from potato mash through hydrothermal treatment and high‐temperature activation with KOH as agent. The supercapacitors with aqueous electrolyte of 6 mKOH and a mass loading of 5 mg per electrode achieve a specific gravimetric capacitance of 333.7 F g⁻¹per electrode and a specific energy of 11.75 W h g⁻¹at a specific power of 197.6 W kg⁻¹at a current density of 0.4 A g⁻¹under a nominal compressive stress of 7.96 MPa. The supercapacitors with a mass loading of 10 mg per electrode achieve the maximum specific gravimetric capacitance of 340.6 F g⁻¹and a specific energy of 11.75 W h g⁻¹at a specific power of 194.2 W kg⁻¹at a current density of 0.4 A g⁻¹under a nominal compressive stress of 7.96 MPa. Increasing the compaction of electrode materials under compressive stress has the potential to increase the electrochemical performance of supercapacitors. 

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