171 research outputs found
Major accidents scenarios used for LUP and off-site emergency planning : importance of kinetic description
International audienceThe European States, France in particular, faced with several industrial accidents, like one of the most serious one, the AZF explosion in Toulouse (France) in 2001, which created the trauma of the stakeholders concerned by the chemical risk (industry, authorities and citizen). Learning from this experience, the French Ministry in charge of the Environment, with the help of INERIS, worked on upgrading its chemical risks knowledge and studied to improve new methods on risk assessment. In 2004, INERIS was in charge of developing a new approach to classify accidental scenarios in terms of probability, severity and response time. In this paper, INERIS proposes a prioritisation based on time of occurrence, of development of hazardous phenomena and of effects on targets. Then, INERIS shows a method enabling to integrate, as a second prioritisation criteria, the on-site and off-site response capabilities/abilities as well as the means for population protection in terms of time allowed
Temperature and moisture are minor drivers of regional-scale soil organic carbon dynamics
Storing large amounts of organic carbon, soils are a key but uncertain component of the global carbon cycle, and accordingly, of Earth System Models (ESMs). Soil organic carbon (SOC) dynamics are regulated by a complex interplay of drivers. Climate, generally represented by temperature and moisture, is regarded as one of the fundamental controls. Here, we use 54 forest sites in Switzerland, systematically selected to span near-independent gradients in temperature and moisture, to disentangle the effects of climate, soil properties, and landform on SOC dynamics. We estimated two SOC turnover times, based on bulk soil 14C measurements (Ï14C) and on a 6-month laboratory soil incubation (Ïi). In addition, upon incubation, we measured the 14C signature of the CO2 evolved and quantified the cumulated production of dissolved organic carbon (DOC). Our results demonstrate that Ïi and Ï14C capture the dynamics of contrasting fractions of the SOC continuum. The 14C-based Ï14C primarily reflects the dynamics of an older, stabilised pool, whereas the incubation-based Ïi mainly captures fresh readily available SOC. Mean site temperature did not raise as a critical driver of SOC dynamics, and site moisture was only significant for Ïi. However, soil pH emerged as a key control of both turnover times. The production of DOC was independent of Ïi and not driven by climate, but primarily by the content of clay and, secondarily by the slope of the site. At the regional scale, soil physicochemical properties and landform appear to override the effect of climate on SOC dynamics
Mineralisation of crop residues on the soil surface or incorporated in the soil under controlled conditions
In the present work, we compare the effect of mature crop residues mixed into a ferralitic soil or placed as a single layer on soil surface on the mineralisation of C and N over 55 days. As residues, we used dry stems of rice, soybean, sorghum, brachiaria and wheat. There were no significant effects of residue placement on C mineralisation kinetics. Decomposition of the residues on the soil surface slightly increased net N mineralisation for residues having the smallest C/N ratio
Analysis of physical pore space characteristics of two pyrolytic biochars and potential as microhabitat
Background and Aims
Biochar amendment to soil is a promising practice of enhancing productivity of agricultural systems. The positive effects on crop are often attributed to a promotion of beneficial soil microorganisms while suppressing pathogens e.g. This study aims to determine the influence of biochar feedstock on (i) spontaneous and fungi inoculated microbial colonisation of biochar particles and (ii) physical pore space characteristics of native and fungi colonised biochar particles which impact microbial habitat quality.
Methods
Pyrolytic biochars from mixed woods and Miscanthus were investigated towards spontaneous colonisation by classical microbiological isolation, phylogenetic identification of bacterial and fungal strains, and microbial respiration analysis. Physical pore space characteristics of biochar particles were determined by X-ray Ό-CT. Subsequent 3D image analysis included porosity, surface area, connectivities, and pore size distribution.
Results
Microorganisms isolated from Wood biochar were more abundant and proliferated faster than those from the Miscanthus biochar. All isolated bacteria belonged to gram-positive bacteria and were feedstock specific. Respiration analysis revealed higher microbial activity for Wood biochar after water and substrate amendment while basal respiration was on the same low level for both biochars. Differences in porosity and physical surface area were detected only in interaction with biochar-specific colonisation. Miscanthus biochar was shown to have higher connectivity values in surface, volume and transmission than Wood biochars as well as larger pores as observed by pore size distribution. Differences in physical properties between colonised and non-colonised particles were larger in Miscanthus biochar than in Wood biochar.
Conclusions
Vigorous colonisation was found on Wood biochar compared to Miscanthus biochar. This is contrasted by our findings from physical pore space analysis which suggests better habitat quality in Miscanthus biochar than in Wood biochar. We conclude that (i) the selected feedstocks display large differences in microbial habitat quality as well as physical pore space characteristics and (ii) physical description of biochars alone does not suffice for the reliable prediction of microbial habitat quality and recommend that physical and surface chemical data should be linked for this purpose
Aromaticity and degree of aromatic condensation of char
The aromatic carbon structure is a defining property of chars and is often expressed with the help of two concepts: (i) aromaticity and (ii) degree of aromatic condensation. The varying extent of these two features is assumed to largely determine the relatively high persistence of charred material in the environment and is thus of interest for e.g. biochar characterization or carbon cycle studies. Consequently, a variety of methods has been used to assess the aromatic structure of chars, which has led to interesting insights but has complicated the comparison of data acquired with different methods. We therefore used a suite of seven methods (elemental analysis, MIR spectroscopy, NEXAFS spectroscopy, 13C NMR spectroscopy, BPCA analysis, lipid analysis and helium pycnometry) and compared 13 measurements from them using a diverse sample set of 38 laboratory chars. Our results demonstrate that most of the measurements could be categorized either into those which assess aromaticity or those which assess the degree of aromatic condensation. A variety of measurements, including relatively inexpensive and simple ones, reproducibly captured the two aromatic features in question, and data from different methods could therefore be compared. Moreover, general patterns between the two aromatic features and the pyrolysis conditions were revealed, supporting reconstruction of the highest heat treatment temperature (HTT) of char
Global-scale evidence for the refractory nature of riverine black carbon
Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Nature Geoscience 11 (2018): 584-588, doi:10.1038/s41561-018-0159-8.Wildfires and incomplete combustion of fossil fuel produce large amounts of black carbon. Black carbon production and transport are essential components of the carbon cycle. Constraining estimates of black carbon exported from land to ocean is critical, given ongoing changes in land use and climate, which affect fire occurrence and black carbon dynamics. Here, we present an inventory of the concentration and radiocarbon content (â14C) of particulate black carbon for 18 rivers around the globe. We find that particulate black carbon accounts for about 15.8â±â0.9% of river particulate organic carbon, and that fluxes of particulate black carbon co-vary with river-suspended sediment, indicating that particulate black carbon export is primarily controlled by erosion. River particulate black carbon is not exclusively from modern sources but is also aged in intermediate terrestrial carbon pools in several high-latitude rivers, with ages of up to 17,000 14C years. The flux-weighted 14C average age of particulate black carbon exported to oceans is 3,700 ± 400 14C years. We estimate that the annual global flux of particulate black carbon to the ocean is 0.017 to 0.037âPg, accounting for 4 to 32% of the annually produced black carbon. When buried in marine sediments, particulate black carbon is sequestered to form a long-term sink for CO2.A.C. acknowledges financial support from the University of Zurich Forschungskredit Fellowship and the University of Zurich (grant No. STWF-18-026). M.R., S.A. and M.S. acknowledge support from the University Research Priority Projection Global Change and Biodiversity (URPP-GCB). M.Z. acknowledges support from the National Natural Science Foundation of China (No. 41521064). T.E. acknowledges support from the Swiss National Science Foundation (âCAPS-LOCKâ and âCAPS-LOCK2â #200021_140850). V.G. acknowledges financial support from an Independent Study Award from the Woods Hole Oceanographic Institution
Impact of amendments on the physical properties of soil under tropical long-term no till conditions
Tropical regions have been considered the world's primary agricultural frontier; however, some physico-chemical deficiencies, such as low soil organic matter content, poor soil structure, high erodibility, soil acidity, and aluminum toxicity, have affected their productive capacity. Lime and gypsum are commonly used to improve soil chemical fertility, but no information exists about the long-term effects of these products on the physical attributes and C protection mechanisms of highly weathered Oxisols. A field trial was conducted in a sandy clay loam (kaolinitic, thermic Typic Haplorthox) under a no-tillage system for 12 years. The trial consisted of four treatments: a control with no soil amendment application, the application of 2.1 Mg ha-1 phosphogypsum, the application of 2.0 Mg ha-1 lime, and the application of lime + phosphogypsum (2.0 + 2.1 Mg ha-1, respectively). Since the experiment was established in 2002, the rates have been applied three times (2002, 2004, and 2010). Surface liming effectively increased water-stable aggregates > 2.0 mm at a depth of up to 0.2 m; however, the association with phosphogypsum was considered a good strategy to improve the macroaggregate stability in subsoil layers (0.20 to 0.40 m). Consequently, both soil amendments applied together increased the mean weight diameter (MWD) and geometric mean diameter (GMD) in all soil layers, with increases of up to 118 and 89%, respectively, according to the soil layer. The formation and stabilization of larger aggregates contributed to a higher accumulation of total organic carbon (TOC) on these structures. In addition to TOC, the MWD and aggregate stability index were positively correlated with Ca2+ and Mg2+ levels and base saturation. Consequently, the increase observed in the aggregate size class resulted in a better organization of soil particles, increasing the macroporosity and reducing the soil bulk density and penetration resistance. Therefore, adequate soil chemical management plays a fundamental role in improving the soil's physical attributes in tropical areas under conservative management and highly affected by compaction caused by intensive farming
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Aromaticity and degree of aromatic condensation of char
The aromatic carbon structure is a defining property of chars and is often expressed with the help of two
concepts: (i) aromaticity and (ii) degree of aromatic condensation. The varying extent of these two features
is assumed to largely determine the relatively high persistence of charred material in the environment
and is thus of interest for, e.g., biochar characterization or carbon cycle studies. Consequently, a
variety of methods has been used to assess the aromatic structure of chars, which has led to interesting
insights but has complicated the comparison of data acquired with different methods. We therefore used
a suite of seven methods (elemental analysis, MIR spectroscopy, NEXAFS spectroscopy, ÂčÂłC NMR spectroscopy,
BPCA analysis, lipid analysis and helium pycnometry) and compared 13 measurements from them
using a diverse sample set of 38 laboratory chars. Our results demonstrate that most of the measurements
could be categorized either into those which assess aromaticity or those which assess the degree
of aromatic condensation. A variety of measurements, including relatively inexpensive and simple ones,
reproducibly captured the two aromatic features in question, and data from different methods could
therefore be compared. Moreover, general patterns between the two aromatic features and the pyrolysis
conditions were revealed, supporting reconstruction of the highest heat treatment temperature (HTT) of
char.Keywords: Aromaticity,
Stability,
Aromatic condensation,
Pyrolysis,
Char,
Biochar,
Pyrogenic organic matter,
Heat treatment temperatur
Returning Winter Cover Crop Residue Influences Soil Aggregation and Humic Substances under Double-cropped Rice Fields
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