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Black carbon (BC) is one of the most stable forms of soil organic matter. Its surface functional groups and structure have been well characterized by a range of analytical methods. However, little is known about the mechanisms of interactions between the BC particles and the surrounding mineral matter. In this paper a range of microscopy techniques, such as transmission electron microscopy and scanning transmission electron microscopy, were used to investigate the possible reactions of BC particles within microaggregates (<2 mm) found in Amazonian dark Earth. Attention is given to the interactions that occur at the interfacial regions between the organic and inorganic phases. Examination of Amazonian dark Earth showed that the carbon-rich phase detected within the BC particles has a significant calcium concentration and a high density of micropores was found at the BC-mineral interface. These observations provide evidence to support suggested mechanisms of interaction between these phases.

A wealth of knowledge has been published in the last decade on redox regulations in plants. However, these works remained largely at cellular and organelle levels. Simple indicators of oxidative stress at the plant level are still missing. We developed a method for direct measurement of leaf Eh and pH, which revealed spatial, temporal, and genotypic variations in rice. Eh (redox potential) and Eh@pH7 (redox potential corrected to pH 7) of the last fully expanded leaf decreased after sunrise. Leaf Eh was high in the youngest leaf and in the oldest leaves, and minimum for the last fully expanded leaf. Leaf pH decreased from youngest to oldest leaves. The same gradients in Eh-pH were measured for various varieties, hydric conditions, and cropping seasons. Rice varieties differed in Eh, pH, and/or Eh@pH7. Leaf Eh increases and leaf pH decreases with plant age. These patterns and dynamics in leaf Eh-pH are in accordance with the pattern and dynamics of disease infections. Leaf Eh-pH can bring new insight on redox processes at plant level and is proposed as a novel indicator of plant stress/health. It could be used by agronomists, breeders, and pathologists to accelerate the development of crop cultivation methods leading to agroecological crop protection.

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Methane constitutes 15% of total global anthropogenic greenhouse gas emissions. The mitigation of these emissions could have a significant near-term effect on slowing global warming, and recovering and burning the methane would allow a wasted energy resource to be exploited. The typically low and fluctuating energy content of the emission streams makes combustion difficult; however porous burners-an advanced combustion technology capable of burning low-calorific value fuels below the conventional flammability limit-are one possible mitigation solution. Here we discuss a pilot-scale porous burner designed for this purpose. The burner comprises a cylindrical combustion chamber filled with a porous bed of alumina saddles, combined with an arrangement of heat exchanger tubes for preheating the incoming emission stream. A computational fluid dynamics model was developed to aid in the design process. Results illustrating the burner's stable operating range and behavior are presented: stable ultralean combustion is demonstrated at natural gas concentrations as low as 2.3 vol%, with transient combustion at concentrations down to 1.1 vol%; the system is comparatively stable to perturbations in the operating conditions, and emissions of both carbon monoxide and unburned hydrocarbons are negligible. Based on this pilot-scale demonstration, porous burners show potential as a methane mitigation technology.

The study of the interaction of bacteria with surfaces requires the detection of specific bacterial groups with high spatial resolution. Here, we describe a method to rapidly and efficiently add nanogold particles to oligonucleotide probes, which target bacterial ribosomal RNA. These nanogold-labeled probes are then used in an in situ hybridization procedure that ensures both cellular integrity and high specificity. Electron microscopy subsequently enables the visualization of specific cells with high local precision on complex surface structures. This method will contribute to an increased understanding of how bacteria interact with surface structures on a sub-micron scale.

Biochar is widely used as an adsorbent to remove heavy metals from aqueous solutions. To investigate the contribution of soluble minerals (mainly anions) to Pb 2+ removal in solution, wheat straw biochar was washed with deionized water to remove soluble minerals. Batch adsorption was conducted using washed biochar (WBC) and unwashed biochar (BC) to absorb Pb 2+ . After washing, the pH and ash content of biochar were reduced, while the specific surface area and total pore volume were increased. Adsorption kinetics of Pb 2+ onto BC and WBC were well fitted to the pseudo-second-order model (R 2 > 0.99). Pb sorption on BC and WBC were better fit with the Langmuir model (R 2 = 0.96 to 0.97) than the Freundlich model (R 2 = 0.71 to 0.87). The Langmuir maximum adsorption capacity of Pb on BC was 99.7 mg g -1 , which was 4.5-fold higher than that on WBC when the initial solution pH was 5.0. The concentration of SO4 2-, CO3 2-, SiO3 2-, and PO4 3-in the equilibrium solution was reduced by 69, 89, 97, and 41%, respectively, with the increase of initial Pb 2+ concentration. The difference of Pb 2+ adsorption capacity between BC and WBC proved that the soluble anions in biochar play an important role in Pb 2+ sorption onto biochar.