CARBONO ORGÂNICO E NITROGÊNIO TOTAL NAS FRAÇÕES GRANULOMÉTRICAS E HÚMICAS EM SOLOS SOB DIFERENTES TEXTURAS

A decomposição e distribuição dos componentes da matéria orgânica são influenciados diretamente pela textura do solo e podem se dar de forma diferenciada ao longo do perfil de solo. Diante disso, desenvolveu-se experimento para avaliar o teor de carbono orgânico (CO) e de nitrogênio total (NT) nas frações granulométricas e húmicas de solos sob diferentes texturas. Foram coletadas amostras em cinco quadrantes, nas profundidades de 0-20, 20-40, 40-60 e 60-100 cm. Essas amostras foram secas e passadas em peneira de 2,0 mm para os fracionamentos físico e químico. O fracionamento físico foi realizado por meio de ultrasom e as frações húmicas através da extração alcalina. O teor de CO foi determinado pela digestão sulfocrômica a quente seguida de titulação com sulfato ferroso amoniacal, enquanto o teor de nitrogênio foi obtido pela digestão seguida de destilação e titulação. Os teores de CO foram maiores na fração > 53 μm e os de NT na fração < 53 µm. A fração ácido húmico (FAH) teve o maior teor de carbono e a fração humina (FHum) teve o menor teor. A relação extrato alcalino (EA/Hum) variou de 22,09 a 24,76 g Kg-1 indicando predomínio da fração húmica na camada superficial.Palavras-chave: fracionamento físico e químico, matéria orgânica, granulometria do solo. ORGANIC CARBON AND TOTAL NITROGEN IN GRANULOMETRIC AND HUMIC FRACTIONS IN SOILS UNDER DIFFERENT TEXTURES ABSTRACT: The decomposition and distribution of the organic matter components are directly influenced by the soil texture and can occur differently along the soil profile. Therefore, an experiment was developed to evaluate the organic carbon (OC) and total nitrogen (TN) content of the granulometric and humic fractions of soils under different textures. Samples were collected on five quadrants, at depths of 0-20, 20-40, 40-60 and 60-100 cm. These samples were dried and passed through a 2.0 mm sieve to be submitted to the physical and chemical fractionations. The physical fractions were obtained by means of ultrasound and the humic fractions through the alkaline extraction. The OC content was determined by hot sulfocromic digestion followed by titration with ammoniacal ferrous sulfate, while the nitrogen content was obtained by digestion followed by distillation in semi-microdistiller and titration. The OC contents were higher in the fraction > 53 μm and TN in the fraction < 53 μm. The humic acid fraction (HAF) had the highest carbon content and the humic fraction (HUMF) had the lowest content. The alkaline extract ratio (AE /HUM) ranged from 22.09 to 24.76 g Kg-1 indicating predominance of the humic fraction in the surface layer.Keywords: physical and chemical fractionation, organic matter, soil granulometry.

Beberapa Sifat Kimia Tanah Akibat Pemberian Ekstrak Krandalit dan Fraksi Bahan Organik pada Humic Hapludults

The aims of this research were to study pH, C-organic, exchangeable Al, P_available (Bray II), and Fe-DTPA, due to applications of crandallite extract and organic matter fraction of peat and chicken dung on Humic Hapludults. This research was conducted at Jatinangor. The laboratory experiment was rranged in a factorial split plot design consisted of two kinds or organic matter (peat and chicken dung) as main plot, three levels organic fractions namely: without organic fraction, humic fraction and fulfic fractions as sub-plot and four levels crandallite extract (0, 50, 100 and 150 kg P2O5 per hectare) as sub-plots. Each treatment unit was replicated three times so it produced 72 experiment units. Results showed that humic fraction application at different level of crandillate extract increased soil pH, Fe-DTPA, dry weight of root and shoot. Crandallite extract application increased P-available (3 mg per kg). HUmic fractions increased organic C in soils (0,63%), dry weight shoot (4,71 g per plant) and decreased exchangeable Al (0,10 cmol per kg).

A novel thermodynamic approach for the complexation study of toxic metal cations by a landfill leachate

The leachate humic fraction is a good sequestering agent towards toxic metal ions, influencing their aqueous solution behaviour and their environmental impact.

Anaerobic Methane Oxidation Driven by Microbial Reduction of Natural Organic Matter in a Tropical Wetland

ABSTRACT Wetlands constitute the main natural source of methane on Earth due to their high content of natural organic matter (NOM), but key drivers, such as electron acceptors, supporting methanotrophic activities in these habitats are poorly understood. We performed anoxic incubations using freshly collected sediment, along with water samples harvested from a tropical wetland, amended with 13C-methane (0.67 atm) to test the capacity of its microbial community to perform anaerobic oxidation of methane (AOM) linked to the reduction of the humic fraction of its NOM. Collected evidence demonstrates that electron-accepting functional groups (e.g., quinones) present in NOM fueled AOM by serving as a terminal electron acceptor. Indeed, while sulfate reduction was the predominant process, accounting for up to 42.5% of the AOM activities, the microbial reduction of NOM concomitantly occurred. Furthermore, enrichment of wetland sediment with external NOM provided a complementary electron-accepting capacity, of which reduction accounted for ∼100 nmol 13CH4 oxidized · cm−3 · day−1. Spectroscopic evidence showed that quinone moieties were heterogeneously distributed in the wetland sediment, and their reduction occurred during the course of AOM. Moreover, an enrichment derived from wetland sediments performing AOM linked to NOM reduction stoichiometrically oxidized methane coupled to the reduction of the humic analogue anthraquinone-2,6-disulfonate. Microbial populations potentially involved in AOM coupled to microbial reduction of NOM were dominated by divergent biota from putative AOM-associated archaea. We estimate that this microbial process potentially contributes to the suppression of up to 114 teragrams (Tg) of CH4 · year−1 in coastal wetlands and more than 1,300 Tg · year−1, considering the global wetland area. IMPORTANCE The identification of key processes governing methane emissions from natural systems is of major importance considering the global warming effects triggered by this greenhouse gas. Anaerobic oxidation of methane (AOM) coupled to the microbial reduction of distinct electron acceptors plays a pivotal role in mitigating methane emissions from ecosystems. Given their high organic content, wetlands constitute the largest natural source of atmospheric methane. Nevertheless, processes controlling methane emissions in these environments are poorly understood. Here, we provide tracer analysis with 13CH4 and spectroscopic evidence revealing that AOM linked to the microbial reduction of redox functional groups in natural organic matter (NOM) prevails in a tropical wetland. We suggest that microbial reduction of NOM may largely contribute to the suppression of methane emissions from tropical wetlands. This is a novel avenue within the carbon cycle in which slowly decaying NOM (e.g., humic fraction) in organotrophic environments fuels AOM by serving as a terminal electron acceptor.

HUMIFIED FRACTION OF ORGANIC MATTER DUE TO PLANT MIXTURE CULTIVATION

ABSTRACT - The aim of this study was to assess the organic matter changes in quantity and quality, particularly of the humic fraction in the surface layer (0-20 cm), of a Typic Plinthustalf soil under different management of plant mixtures used as green manure for mango (Mangifera indica L.) crops. The plant mixtures, which were seeded between rows of mango trees, were formed by two groups of leguminous and non -leguminous plants. Prior to sowing, seeds were combined in different proportions and compositions constituting the following treatments: 100% non-leguminous species (NL); 100% leguminous species (L); 75% L and 25% NL; 50% L and 50% NL; 25% L and 75% NL; and 100% spontaneous vegetation, considered a control. The plant mixtures that grew between rows of mango trees caused changes in the chemical composition of the soil organic matter, especially for the treatments 50% L and 50% NL and 25% L and 75% NL, which increased the content of humic substances in the soil organic matter. However, the treatment 25% L and 75% NL was best at minimising loss of total organic carbon from the soil. The humic acids studied have mostly aliphatic characteristics, showing large amounts of carboxylic and nitrogen groups and indicating that most of the organic carbon was formed by humic substances, with fulvic acid dominating among the alkali soluble fractions.