Data of “Carbon emissions and priming effects derived from crop residues and their responses to nitrogen inputs”

The generality, driving factors, and responses to nitrogen (N) inputs of carbon emissions and priming effects derived from crop residues were investigated in this study.</p

Low-Complexity Detection Algorithms for Spatial Modulation MIMO Systems

In this paper, the authors propose three low-complexity detection schemes for spatial modulation (SM) systems based on the modified beam search (MBS) detection. The MBS detector, which splits the search tree into some subtrees, can reduce the computational complexity by decreasing the nodes retained in each layer. However, the MBS detector does not take into account the effect of subtree search order on computational complexity, and it does not consider the effect of layers search order on the bit-error-rate (BER) performance. The ost-MBS detector starts the search from the subtree where the optimal solution is most likely to be located, which can reduce total searches of nodes in the subsequent subtrees. Thus, it can decrease the computational complexity. When the number of the retained nodes is fixed, which nodes are retained is very important. That is, the different search orders of layers have a direct influence on BER. Based on this, we propose the oy-MBS detector. The ost-oy-MBS detector combines the detection order of ost-MBS and oy-MBS together. The algorithm analysis and experimental results show that the proposed detectors outstrip MBS with respect to the BER performance and the computational complexity

Plant and algal toxicity of persistent free radicals and reactive oxygen species generated by heating anthracene contaminated soils from 100 to 600 °C

International audiencePersistent free radicals (PFRs) are emerging contaminants of increasing concern, yet their formation, fate, toxicity and health risk are poorly known. Thermal treatment, a common remediation technique to clean industrial soils, induces the formation of PFRs, which could paradoxically increase soil toxicity, contrary to the original objective of remediation. Actually, there is little knowledge on the formation and toxicity of PFRs in soils contaminated by polycyclic aromatic hydrocarbons (PAHs). Here we studied the generation of PFRs of soils spiked with anthracene and heated 1 h from 100 to 600 °C, using electron paramagnetic resonance. We also investigated the formation of reactive oxygen species (ROS), e.g. superoxide radical (O2•−), hydrogen peroxide (H2O2) and hydroxyl radical (•OH), in the aqueous phase of thermal-treated soil, and the impact of heating on soil oxidative potential, wheat growth and green algae activity. Results showed that PFRs, ROS, soil oxidative potential, plant toxicity and algal toxicity show a similar trend with an increase from 100 to 300 °C, followed by a decrease to 600 °C. Scavenger trapping tests reveal that algal toxicity is mainly due to the generation of O2•− , •OH and H2O2 induced by anthracene-PFRs and that anthracene and anthracene-PFRs have negligible direct algal toxicity. Overall, our findings reveal the unintended formation of toxic compounds peaking at 300 °C during the thermal remediation of PAHcontaminated soils. These results should help to assess the environmental risk of thermally treated PAH-contaminated soils

Abiotic transformation of polycyclic aromatic hydrocarbons via interaction with soil components: A systematic review

International audienceNatural attenuation is a major ecosystem function allowing to abate soil organic contaminants such as polycyclic aromatic hydrocarbons (PAHs). Biodegradation of PAHs is classically considered as the major driver of natural attenuation, yet the role of abiotic transformation, including photodegradation, chemical oxidation, formation of non-extractable residues, and polymerization, has been overlooked due to the lack of investigations until recently. This paper reviews PAHs dissipation in soils by abiotic processes such as photodegradation and oxidation catalyzed by inorganic minerals and organic matters. The role of soil components on degradation rates, pathways, and mechanisms are discussed. The products of PAHs abiotic transformation and their potential risks are also described. Abiotic transformations are mainly controlled by interactions between PAHs and clay minerals, metal oxides/hydroxides, and soil organic matter. PAH photodegradation proceeds by both direct and indirect photolysis processes, which are enhanced in the presence of natural photosensitizers, for example, organic matter, and photocatalysts, for example, metal oxides/hydroxides. PAHs can also be chemically/catalytically oxidized by metal oxides/hydroxides, for example, MnO2, FexOy, and clay minerals without light irradiation. Overall, PAHs transformation depends on their electron-donating properties, mineral electron-accepting properties, pH, temperature, moisture, and oxygen content. Following the elucidation of the transformative mechanism, knowledge to understand the impact of abiotic transformation on biodegradation are delineated. Future investigations are needed to advance the correlation of laboratory generated rates to the field applications, and the potential applications of natural attenuation based on abiotic processes are proposed

High contribution of hydrocarbon transformation during the removal of polycyclic aromatic hydrocarbons from soils, humin and clay by thermal treatment at 100-200 °C

International audiencePolycyclic aromatic hydrocarbons (PAHs) are major pollutants in air, soils and sediments. PAH-polluted soils can be cleaned rapidly by thermal treatment. PAH volatilization is considered as the main process explaining PAH removal at low temperature , yet other processes may occur. Particularly, we hypothesize that thermal transformation can also explain PAH removal, where transformation refers to both degradation and formation of bound PAHs. We thus studied the removal of spiked benzo[a]pyrene at 0.5 mg/g in bauxite soil, fluvo-aquic soil, chernozem soil, montmorillonite, humin, and quartz sand as control, from 100 to 200 °C. We measured concentrations of benzo[a]pyrene in the volatilized fraction and solid residues by high-performance liquid chromatography. We identified transformation products by gas chromatography-mass spectrometry. Results show that the contribution of thermal transformation to the removal of benzo[a]pyrene increased from 24.7 to 58.4 wt% for bauxite soil, from 4.4 to 38.2 wt% for fluvo-aquic soil, and from 11.5 to 35.9 wt% for chernozem soil, with temperature increasing from 100 to 200 °C. Transformation such as oxidation occurred in all samples except in benzo[a]pyrene-spiked quartz sands. Transformation of benzo[a]pyrene was thus partly explained by the presence of clay minerals, as evidenced for the montmorillonite assay where transformation contributed 74.6 wt% to the total removal of benzo[a]pyrene at 200 °C. Overall, our findings demonstrate a major overlooked contribution of transformation to PAH removal at low temperature

Formation of environmentally persistent free radicals and reactive oxygen species during the thermal treatment of soils contaminated by polycyclic aromatic hydrocarbons

International audienceEnvironmentally persistent free radicals (EPFRs) are emerging contaminants of increasing concern due to their toxicity for life and ecosystems, yet their formation, behavior and fate are poorly known. In particular, there is actually no knowledge on the formation of those radicals during the thermal treatment of soils containing polycyclic aromatic hydrocarbons. Such knowledge is important because thermal treatment is a remediation method used to decontaminate soils by removing and degrading PAHs. Here, we studied the formation of radicals in three types of cultivated soils, bauxite soil, fluvo-aquic soil and chernozem soil, artificially contaminated by benzo[a]pyrene, during thermal treatment from 100 to 200 °C for 1 h, using electron paramagnetic resonance. Results show spins densities of radicals up to of 2.079 × 10 17 spins/g for bauxite soil, 1.481 × 10 17 spins/g for fluvo-aquic soil and 8.592 × 10 16 spins/g for chernozem soil at 175 °C. The formed radicals exhibited multiple decays during their observable time and the shortest 1/e lifetimes of radicals up to 757.58 h. These findings are strengthened by EPFR-induction of reactive oxygen species (ROS), O 2 ·− and · OH, which increased in concentrations from 100 to 200 °C. Overall, our results demonstrates for the first time that thermal treatment of PAHs-contaminated soils induces the formation of EPFRs and suggests that thermal treatment might not be a fully clean remediation method for soils as thermal treatment creates new contaminants

In Situ Raman Probing of Chlorphenol Degradation on Different Facets of K₃B₆O₁₀Br Single Crystal

Semiconductor photocatalysts with specific facets can induce high reactive activities has aroused wide attention. Here, we endeavor to gain quantitative insights into the intrinsic facet-dependent catalytic activities of K₃B₆O₁₀Br (KBB) crystal using in situ Raman technique under room temperature by photocatalysis dechlorination of 2,4-DCP as a model reaction. Using a well-defined sizable KBB single crystal (size: 28 mm × 20 mm × 9 mm) with high (211), (110), and (101) facet exposure, the time-resolved Raman spectra for different facets have been clearly tested, it shows that the Raman spectrum of (211) facet had a remarkable change compared with (110) and (101) facets when the crystal was immersed in the 2,4-DCP solution under light irradiation. Through DFT, we obtain qualitative details on the reaction mechanisms of photocatalyzed and provide a refined understanding of the elementary processes. It was found that the −OH contact mode between the pollutant and the crystal facet was the most effective mode, which can produce more ^•OH radicals than the other two modes. Moreover, the (211) facet offers the largest ratio of K atoms and surface energy, making the (211) facet more active than (110) and (101) facets

The protective layer formed by soil particles on plastics decreases the toxicity of polystyrene microplastics to earthworms (Eisenia fetida)

International audienceThe recent discovery of microplastics contaminants in most ecosystems has raised major health issues, yet knowledge on their impact on soil organisms is limited, especially their toxicity evolution with aging. Here we studied the toxicity of polystyrene microplastics (PS-MP) to earthworm (Eisenia fetida) after microplastic aging in soil. Results showed that the 50% lethal concentration was 25.67 g/kg for microplastics, and 96.47 g/Kg for plastics that have aged 28 days in soil, indicating the toxicity of microplastics decreased with aging. Laser scanning confocal microscope and scanning electron microscope (SEM) reveal that the toxicity of microplastics to earthworm may be due to the ingestion of microplastics by earthworms and physical damage, e.g., epidermis abrasion and setae loss, induced by microplastics. Similarly, the levels of reactive oxygen species, antioxidant enzyme activities and malondialdehyde increased with microplastic concentrations from 0.1 to 1.5 g/kg, but decreased with aging from 7 to 28 days. The integrated biomarker response index also confirmed that the toxicity of microplastics decreased with aging. SEM show that microplastics were progressively covered by soil particles during soil aging, inducing the formation of protective layer and increasing the particle size of microplastics, which prevented direct contact with earthworms and decreased the ingestion of microplastics, and, in turns decreased microplastic toxicity. Overall, our study provides valuable insights for elucidating the effect of aging on the toxicity of microplastics

Formation of persistent free radicals in sludge biochar by hydrothermal carbonization

International audienceThe uses of biochar as soil fertilizer can offset global warming and reduce dependence on limited mineral resources in the future circular economy, yet biochar may contain contaminants that can ultimately enter the food chain. In particular, persistent free radicals are emerging contaminants previously detected in biochar but underlying mechanisms of radical formation are not yet established. Here we studied radical generation during hydrothermal carbonization of waste sludge at 160-220 ºC for 0.5-2 h with solid weight ratios of 10%w-40%w using electron paramagnetic resonance and Fourier transform infrared spectrometry. Results reveal that radical concentration increases with temperature, reaction time, and weight ratio in sludge biochars, reaching a content of 47.2 × 10 15 spins/g for 220 ºC, 2 h heating, and 40%w solid ratio. Moreover, low temperature of about 160 ºC favors the production of oxygen-centered radicals, whereas higher temperature of 220 ºC produces carbon-centered radicals. Our findings imply that biochar ecotoxicity should be assessed prior applications to prevent adverse health effects