Application of biochar as a soil amendment could be a significant approach for carbon sequestration to possibly control climate change for energy and environmental sustainability. However, more studies are needed in a number of research areas, including the development of clean biochar materials free of any harmful substances, before this approach could be implemented at a global scale. In this study, biochar water-extractable substances were tested for their potential harmful effects on the growth of aquatic photosynthetic microorganisms including both blue−green alga (cyanobacteria Synechococcus) and eukaryotic green alga (Desmodesmus) that represent the primary photosynthetic producers of the aquatic environment. The water extracts from three different biomass-derived biochar materials varied widely in their dissolved organic and inorganic contents, as well as in their characteristics including their pH values. Bioassays with pinewood-derived biochar water extract showed a significant inhibitory effect on aquatic photosynthetic microorganism growth in a dose-dependent manner, while chicken litter and peanut shell-derived biochar water extracts showed no signs of growth inhibition. The pinewood-derived biochar water-extracted substances were further separated into three fractions based on their molecular sizes and electric charges through an electrodialysis separation process using a cellulose− acetate membrane with a 500-delta cutoff pore size. Our analysis showed that the active component of pinewood-derived biochar water-extracted substances that are toxic to both blue−green alga (cyanobacteria Synechococcus) and eukaryotic green alga (Desmodesmus) is likely a 500-delta (or smaller) organic chemical species that carries at least one carboxyl group. This finding is important to engineering a high-tech biochar that can be free of any undesirable substances for its soil applications toward agricultural and environmental sustainability.
Abstract. This paper presents an analysis of observations of methane and its two major isotopologues, CH3D and 13CH4, from the Atmospheric Chemistry Experiment (ACE) satellite between 2004 and 2013. Additionally, atmospheric methane chemistry is modeled using the Whole Atmospheric Community Climate Model (WACCM). ACE retrievals of methane extend from 6 km for all isotopologues to 75 km for 12CH4, 35 km for CH3D, and 50 km for 13CH4. While total methane concentrations retrieved from ACE agree well with the model, values of δD–CH4 and δ13C–CH4 show a bias toward higher δ compared to the model and balloon-based measurements. Errors in spectroscopic constants used during the retrieval process are the primary source of this disagreement. Calibrating δD and δ13C from ACE using WACCM in the troposphere gives improved agreement in δD in the stratosphere with the balloon measurements, but values of δ13C still disagree. A model analysis of methane's atmospheric sinks is also performed.
Infrared absorption cross sections near 3.3 µm have been obtained for ethane, C 2 H 6 . These were acquired at elevated temperatures (up to 773 K) using a Fourier transform infrared spectrometer and tube furnace with a resolution of 0.005 cm −1 . The integrated absorption was calibrated using composite infrared spectra taken from the Pacific Northwest National Laboratory (PNNL). These new measurements are the first high-resolution infrared C 2 H 6 cross sections at elevated temperatures.
The distributions of the four most abundant isotopologues and isotopomers (N2O, 15NNO, N15NO, and NN18O) of nitrous oxide have been measured in the Earth's stratosphere by infrared remote sensing with the Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer. These satellite observations have provided a near‐global picture of N2O isotopic fractionation. The relative abundances of the heavier species increase with altitude and with latitude in the stratosphere as the air becomes older. The heavy isotopologues are enriched by 20–30% in the upper stratosphere and even more over the poles. These observations are in general agreement with model predictions made with the Whole Atmosphere Community Climate Model (WACCM). A detailed 3‐D chemical transport model is needed to account for the global isotopic distributions of N2O and to infer sources and sinks.
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