Matéria orgânica do solo em rotações de culturas sob sistema semeadura direta

Pós-graduação em Agronomia (Agricultura) - FCA

Iron oxides and quality of organic matter in sugarcane harvesting systems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Humic fractions of forest, pasture and maize crop soils resulting from microbial activity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aplicação de cinza de bagaço de cana-de-açúcar nos atributos químicos e biológicos do solo

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Effect of the competition of Cu(II) and Ni(II) on the kinetic and thermodynamic stabilities of Cr(III)-organic ligand complexes using competitive ligand exchange (EDTA)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

CO2 and N2O emissions in a soil chronosequence at a glacier retreat zone in Maritime Antarctica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Greenhouse gas balance associated with sugarcane production in South-Central Brazil, considering the management and expansion

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dissolved organic matter in the Lena River Delta Region, Siberia, Russia

Connectivity between the terrestrial and marine environment in the Artic is changing as a result of climate change, influencing both freshwater budgets and the supply of carbon to the sea. This study characterizes the optical properties of dissolved organic matter (DOM) within the Lena Delta region and evaluates the behavior of DOM across the fresh water-marine gradient. Six fluorescent components (four humic-like; one marine humic-like; one protein-like) were identified by Parallel Factor Analysis (PARAFAC) with a clear dominance of allochthonous humic-like signals. Colored DOM (CDOM) and dissolved organic carbon (DOC) were highly correlated and had their distribution coupled with hydrographical conditions. Higher DOM concentration and degree of humification were associated with the low salinity waters of the Lena River. Values decreased towards the higher salinity Laptev Sea shelf waters. Results demonstrate different responses of DOM mixing in relation to the vertical structure of the water column, as reflecting the hydrographical dynamics in the region. Two mixing curves for DOM were apparent. In surface waters above the pycnocline there was a sharper decrease in DOM concentration in relation to salinity indicating removal. In the bottom water layer the DOM decrease within salinity was less. We propose there is a removal of DOM occurring primarily at the surface layer, which is likely driven by photodegradation and flocculation.

Evaluación de las características físico-químicas y biológicas en dos suelos superficiales cultivados con pera (Pyrus communis L.) cv. Williams bajo manejo convencional

El objetivo del trabajo fue identificar las características físico-químicas y biológicas en dos suelos superficiales fertilizados con nitrógeno y enmienda orgánica en el Alto Valle de Río Negro (huertos H1 y H2). En ambos huertos se aplicó fertilizante nitrogenado durante las temporadas 2008-2009 y 2009-2010 y en H2 se aplicó estiércol de pollo. Se extrajeron muestras de suelos en primavera y otoño y se determinó: carbono orgánico total, conductividad eléctrica, cationes de intercambio, relación de adsorción de sodio y nitratos, respiración microbiana, carbono de la biomasa microbiana, actividad de la deshidrogenasa y el índice de mineralización. La concentración de carbono orgánico total, potasio y nitrógeno fueron adecuadas para la producción de pera. El comportamiento de las variables biológicas fue diferente en los huertos. En H1 fueron mayores en primavera, en ambas temporadas y el índice de mineralización fue ligeramente superior a 1 en otoño, indicando equilibrio entre la mineralización y la humificación del carbono. En H2 las mediciones biológicas fueron similares entre las estaciones como consecuencia de realizar fertilización nitrogenada (N) en primavera y en otoño. La enmienda orgánica no reflejó un aumento de la actividad biológica en primavera. La actividad microbiana y enzimática en H1 y H2 fue sensible a los cambios que ocurrieron en los suelos.

Radiocarbon dates, accumulation rates, d13C and July temperature of profiles obtained from Selwyn and Misaw Lake, subarctic Canada

The rapid warming of arctic regions during recent decades has been recorded by instrumental monitoring, but the natural climate variability in the past is still sparsely reconstructed across many areas. We have reconstructed past climate changes in subarctic west-central Canada. Stable carbon and oxygen isotope ratios (d13C, d18O) were derived from a single Sphagnum fuscum plant component; alpha-cellulose isolated from stems. Periods of warmer and cooler conditions identified in this region, described in terms of a "Mediaeval Climatic Anomaly" and "Little Ice Age" were registered in the temperature reconstruction based on the d13C record. Some conclusions could be drawn about wet/dry shifts during the same time interval from the d18O record, humification indices and the macrofossil analysis. The results were compared with other proxy data from the vicinity of the study area. The amplitude of the temperature change was similar to that in chironomid based reconstructions, showing c. 6.5 ±2.3 °C variability in July temperatures during the past 6.2 ka.

Molecular dissolved organic matter composition in lakes across Sweden as relative intensities of FT-ICR-MS peaks and PARAFAC components and optical indices

Whether intrinsic molecular properties or extrinsic factors such as environmental conditions control the decomposition of natural organic matter across soil, marine and freshwater systems has been subject to debate. Comprehensive evaluations of the controls that molecular structure exerts on organic matter's persistence in the environment have been precluded by organic matter's extreme complexity. Here we examine dissolved organic matter from 109 Swedish lakes using ultrahigh-resolution mass spectrometry and optical spectroscopy to investigate the constraints on its persistence in the environment. We find that degradation processes preferentially remove oxidized, aromatic compounds, whereas reduced, aliphatic and N-containing compounds are either resistant to degradation or tightly cycled and thus persist in aquatic systems. The patterns we observe for individual molecules are consistent with our measurements of emergent bulk characteristics of organic matter at wide geographic and temporal scales, as reflected by optical properties. We conclude that intrinsic molecular properties are an important control of overall organic matter reactivity.

Sterol, n-alcohol and n-alkane composition of living fen plants

In groundwater-fed fen peatlands, the surface biomass decays rapidly and, as a result, highly humified peat is formed. A high degree of humification constrains palaeoecological studies because reliable identification of plant remains is hampered. Organic geochemistry techniques as a means of identifying historical plant communities have been successfully applied tobog peat. The method has also been applied to fen peat, but without reference to the composition of fen plants. We have applied selected organic geochemistry methods to determine the composition of the neutral lipid fractions from 12 living fen plants, to investigate the potential for the distributions to characterize and separate different fen plants and plant groups. Our results show correspondence with previous studies, e.g. C23 and C25n-alkanes dominating Sphagnum spp. and C27 to C31 alkanes dominating vascular plants. However, we also found similarities in n-alkane distributions between Sphagnum spp. and the below ground parts of some vascular plants. We tested the efficiency of different n-alkane ratios to separate species and plant groups. The ratios used for bog studies (e.g. n-C23/n-C25 and n-C23/n-C29) did not work as consistently for fen plants. Some differences in sterol distribution were found between vascular plants and mosses; in general vascular plants had a higher concentration of sterols. When distributions of n-alkanes, n-alkane ratios and sterols were all included as variables, redundancy analysis (RDA) separated different plant groups into their own clusters. Our results imply that the pattern for bog biomarkers cannot directly be applied to fen environments. Nevertheless, they encourage further testing to determine whether or not the identification of plant groups, plants or plant parts from highly humified peat is possible by applying fen species-specific biomarker proxies.

Sea-suface microlayer (SML) and underlying water (ULW) samples focusing on CDOM spectral characteristics during METEOR cruise M91

The coastal upwelling system off the coast of Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. From 3 to 23 December 2012, R/V Meteor (M91) cruise took place in the Peruvian upwelling system between 4.59 and 15.4°S, and 82.0 to 77.5°W. During M91 we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like chromophoric dissolved organic matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. We analyzed SML and underlying water (ULW) samples at 38 stations focusing on CDOM spectral characteristics as indicator of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and excitation-emission matrix fluorescence (EEMs), which allow us to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. Spectral slope S varied between 0.012 to 0.043 1 nm-1 and was quite similar between SML and ULW, with no significant differences between the two compartments. Higher S values were observed in the ULW of the southern stations below 15°S. By EEMs, we identified five fluorescent components (F1-5) of the CDOM pool, of which two had excitation/emission characteristics of amino-acid-like fluorophores (F1, F4) and were highly enriched in the SML, with a median ratio SML : ULW of 1.5 for both fluorophores. In the study region, values for CDOM absorption ranged from 0.07 to 1.47 m-1. CDOM was generally highly concentrated in the SML, with a median enrichment with respect to the ULW of 1.2. CDOM composition and changes in spectral slope properties suggested a local microbial release of DOM directly in the SML as a response to light exposure in this extreme environment. In a conceptual model of the sources and modifications of optically active DOM in the SML and underlying seawater (ULW), we describe processes we think may take place (Fig. 1); the production of CDOM of higher MW by microbial release through growth, exudation and lysis in the euphotic zone, includes the identified fluorophores (F1, F2, F3, F4, F5). Specific amino-acid-like fluorophores (F1, F4) accumulate in the SML with respect to the ULW, as photochemistry may enhance microbial CDOM release by (a) photoprotection mechanisms and (b) cell-lysis processes. Microbial and photochemical degradation are potential sinks of the amino-acid-like fluorophores (F1, F4), and potential sources of reworked and more refractory humic-like components (F2, F3, F5). In the highly productive upwelling region along the Peruvian coast, the interplay of microbial and photochemical processes controls the enrichment of amino-acid-like CDOM in the SML. We discuss potential implications for air-sea gas exchange in this area.