Can straw-biochar mulching mitigate erosion of wildfire-degraded soils under extreme rainfall?

High severity wildfires cause a drastic alteration of soil carbon cycling - both oxidising and thermally altering soil organic matter (SOM) - and usually are followed by strong runoff and erosion events. To restore wildfire-degraded soils, SOM needs to be rebuilt while soil erosion is prevented. Post-fire straw mulching has been shown to mitigate soil erosion by providing a protective cover against rainsplash. However, SOM takes many decades or centuries to rebuilt naturally. Biochar, co-applied with straw to the soil surface can replace the SOM of the O-horizon, while the stabilised soil - by straw mulching - may gain in SOM naturally and by downward movement of biochar. We conducted a field study to test if straw-only and straw-biochar co-application could restore soils degraded by wildfire in one high burn severity (HBS) and one moderate burn severity (MBS) study area in southern Portugal and Spain, respectively, by monitoring erosion and SOM for the most intense rainfall period of the first post-fire year. Burned sites were characterized for soil and sediment physical properties, TOC content, SOM quality by thermogravimetry (DTG) and nuclear magnetic resonance (NMR 13C) spectroscopy. Straw-biochar mulching significantly reduced soil erosion by 76% and 65% in the HBS and MBS sites, respectively, in both cases similar to the erosion reduction by straw-only mulching. DTG and NMR 13C indicated that a relatively small proportion of the biochar eroded, i.e. 0.7%, indicating that co-application of straw with biochar may help restore the SOC lost in the wildfire in the medium term. The amount of SOM eroded was lower with straw-biochar mulching than in the untreated plots for both study areas. Straw-biochar mulching mitigates erosion of wildfire-degraded soils under extreme rainfall, while a relatively small proportion of the biochar is lost by erosion. Future studies need to monitor medium term effects.

Pyrolysis-gas chromatography-isotope ratio mass spectrometry for monitoring natural additives in polylactic acid active food packages.

Compound-specific isotope analysis (CSIA) usually requires preparative steps (pretreatments, extraction, derivatization) to get amenable chromatographic analytes from bulk geological, biological or synthetic materials. Analytical pyrolysis (Py-GC/MS) can help to overcome such sample manipulation. This communication describe the results obtained by hyphenating analytical pyrolysis (Py-GC) with carbon isotope-ratio mass spectrometry (IRMS) for the analysis of a polylactic acid (PLA) a based bio-plastic extruded with variable quantities of a natural plant extract or oregano essential oil. The chemical structural information of pyrolysates was first determined by conventional analytical pyrolysis and the measure of δ13C in specific compounds was done by coupling a pyrolysis unit to a gas chromatograph connected to a continuous flow IRMS unit (Py-GC-C-IRMS). Using this Py-CSIA device it was possible to trace natural additives with depleted δ13C values produced by C3 photosystem vegetation (cymene: -26.7‰±2.52; terpinene: -27.1‰±0.13 and carvacrol: -27.5‰±1.80 from oregano and two unknown structures: -23.3‰±3.32 and -24.4‰±1.70 and butyl valerate: -24.1‰±3.55 from Allium spp.), within the naturally isotopically enriched bio-plastic backbone derived from corn (C4 vegetation) starch (cyclopentanones: -14.2‰±2.11; lactide enantiomers: -9.2‰±1.56 and larger polymeric units: -17.2‰±1.71). This is the first application of Py-CSIA to characterize a bio-plastic and is shown as a promising tool to study such materials, providing not only a fingerprinting, but also valuable information about the origin of the materials, allowing the traceability of additives and minimizing sample preparation.

Pyrolysis-gas chromatography-isotope ratio mass spectrometry of polyethylene.

Polyethylene is probably the most used plastic material in daily life and its accurate analysis is of importance. In this communication the chemical structure of polyethylenes is studied in detail using conventional analytical pyrolysis (Py-GC/MS), bulk stable isotopic analysis (IRMS) and pyrolysis compound specific stable isotopic analysis (Py-CSIA) to measure stable isotope proportions (δ(13)C, δ(15)N and δD) of polyethylene pyrolysis compounds. Polyethylene pyrolysis yields triplet peaks of n-alkanes, α-alkenes and α,ω-alkanedienes. No differences were found for bulk δ(13)C among different polyethylene types. However, conspicuous differences in δD were evident. It was possible to assign structure δ(13)C and δD values to specific polyethylene pyrolysis products in the range 12-18 carbon chain length. Conspicuous differences were found for the pyrolysis products with unsaturated moieties showing significant higher δD values than saturated chains (alkanes) that were deuterium depleted. In addition, a full isotopic fingerprinting (δ(13)C, δ(15)N and δD) for a dye (o-chloroaniline) contained in a polyethylene is reported. To the best of our knowledge this is the first application Py-CSIA to the study of a synthetic polymer. This hyphenated analytical technique is a promising tool to study synthetic materials, providing not only a fingerprinting, but also allowing the traceability of the polymerization process and the origin of the materials.

Detection of cylindrospermopsin toxin markers in cyanobacterial algal blooms using analytical pyrolysis (Py-GC/MS) and thermally-assisted hydrolysis and methylation (TCh-GC/MS).

The hepatotoxin cylindrospermopsin (CYN) is produced by freshwater cyanobacteria becoming an emerging threat for human health. Methods for the rapid determination of CYN in environmental samples are needed. Conventional analytical pyrolysis (Py-GC/MS) and thermally-assisted hydrolysis and methylation (TCh-GC/MS) were used to study a CYN standard, two Aphanizomenon ovalisporum cultures (CYN+) and one culture of Cylindrospermopsis raciborskii (CYN-). A micro-furnace pyrolyzer was used directly attached to a GC/MS system fitted with a 30 m × 250 µm × 0.25 µm film thickness column (14% cyanopropyl phenyl, 86% dimethyl polysiloxane pahase composition). Oven temperature was held at 50 °C for 1 min and increased to 100 °C at 30 °C min(-1), from 100 °C to 300 °C at 10 °C min(-1), and stabilized at 300 °C for 10 min using helium (1 mL min(-1)) as carrier gas. Pyrolysis at 500 °C yield over 70 compounds with 20 specific for CYN+ samples. Two peaks containing a diagnostic fragment (m/z 194) were found at 25.0 and 28.9 min only in CYN+ samples. Fewer peaks with limited diagnostic value were released after TCh-GC/MS, including breakdown products and TMAH adducts. A compound was detected that may correspond to the CYN molecule (MW 415 Da) thermoevaporation product after the loss of SO3 (MW 80 Da). This TCh-GC/MS peak (m/z 336) together with the fragments obtained by conventional Py-GC/MS (m/z 194) are diagnostic ions with potential use for the direct detection of CYN toxin in environmental samples at last with an estimated 5 ppm detection threshold.

Assessing the efficiency of urban waste biocomposting by analytical pyrolysis (Py-GC/MS).

Analytical pyrolysis (Py-GC/MS) was used to study complex composting processes. The technique was first validated for reproducibility and finally applied to assess the efficiency of a microbial bio-accelerator product (CBB) in composting organic residues with different composition. Fresh lignocellulosic and urban wastes were treated with CBB and the composting kinetics studied to investigate the transformations undergone in the course of biocomposting. Our findings demonstrate that these changes, as well as the efficiency of CBB, can be monitored through the molecular characterization of the released pyrolysis products. The CBB bacterial product effectively seems to favour composting accelerating the process and shorten composting time. Analytical pyrolysis was informative in assessing to which extent compost transformation reached an acceptable stabilization point. The technique could be also developed into a semi-quantitative tool to monitor changes of main organic matter components (polysaccharides, proteins, lignin, lipids, etc.) as composting proceeds.

[Mixed hepatopathy due to parenteral gold salts]. / Hepatopatía mixta por sales de oro vía parenteral.

A case of a patient with rheumatoid arthritis (RA) of long evolution associated to dry syndrome, who developed a dissociated cholestasis after parenteral administration of gold salts, is suppression of gold salts. We comment on the clinical, biochemical, and histological features of intrahepatic cholestasis related to gold salts, as well as the evolution and the necessary criteria in order to make the diagnosis. We highlight the normal level of bilirubin, comparing it to that described in the literature.

[Sweet's syndrome. Its association with chronic inflammatory bowel disease]. / Síndrome de Sweet. Asociado a enfermedad intestinal inflamatoria crónica.

Sweet's syndrome, or febrile neutrophilic dermatosis, is a disease first described by Sweet R.D. in 1964 as a dermatologic disease. Subsequently, it has been associated to several disease. One of those rarely describe is the association to chronic intestinal inflammatory disease. We reviewed the cases studied in our hospital since 1980 and found two cases associated to chronic intestinal inflammatory disease. We recommend the carrying out of gastrointestinal studies in patients afflicted by Sweet's syndrome to detect its association.

[The CREST syndrome associated with the sicca syndrome]. / Síndrome de CREST asociado a síndrome seco.

A case of CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal hypomotility, sclerodactyly, and telangiectasia) that initially showed Raynaud's phenomenon, sclerodactyly and polyarthralgias, 3 years later completing the process, associated to sicca syndrome, is presented. The esophageal affectation showed a loss of peristalsis of the inferior 2/3, as well as hypotonia of the gastroesophageal sphincter. We comment the prognostic relationship between CREST syndrome and the centromeric region antibodies.