Black carbon affects the cycling of non-black carbon in soil

Black carbon (BC) is an important fraction of many soils worldwide and plays an important role in global C biogeochemistry. However, few studies have examined how it influences the mineralization of added organic matter (AOM) and its incorporation into soil physical fractions and whether BC decomposition is increased by AOM. BC-rich Anthrosols and BC-poor adjacent soils from the Central Amazon (Brazil) were incubated for 532 days either with or without addition of (13)C-isotopically different plant residue. Total C mineralization from the BC-rich Anthrosols with AOM was 25.5% (P < 0.05) lower than with mineralization from the BC-poor adjacent soils. The AOM contributed to a significantly (P < 0.05) higher proportion to the total C mineralized in the BC-rich Anthrosols (91-92%) than the BC-poor adjacent soils (69-80%). The AOM was incorporated more rapidly in BC-rich than BC-poor soils from the separated free light fraction through the intra-aggregate light fraction into the stable organo-mineral fraction and up to 340% more AOM was found in the organo-mineral fraction. This more rapid stabilization was observed despite a significantly (P < 0.05) lower metabolic quotient for BC-rich Anthrosols. The microbial biomass (MB) was up to 125% greater (P < 0.05) in BC-rich Anthrosols than BC-poor adjacent soils. To account for increased MB adsorption onto BC during fumigation extraction, a correction factor was developed via addition of a (13)C-enriched microbial culture. The recovery was found to be 21-41 % lower (P < 0.05) for BC-rich than BC-poor soils due to re-adsorption of MB onto BC. Mineralization of native soil C was enhanced to a significantly greater degree in BC-poor adjacent soils compared to BC-rich Anthrosols as a result of AOM. No positive priming by way of cometabolism due to AOM could be found for aged BC in the soils. (C) 2009 Elsevier Ltd. All rights reserved.

Added sugars: consumption and associated factors among adults and the elderly. São Paulo, Brazil

OBJECTIVE: To investigate added sugar intake, main dietary sources and factors associated with excessive intake of added sugar. METHODS: A population-based household survey was carried out in São Paulo, the largest city in Brazil. Cluster sampling was performed and the study sample comprised 689 adults and 622 elderly individuals. Dietary intake was estimated based on a 24-hour food recall. Usual nutrient intake was estimated by correcting for the within-person variance of intake using the Iowa State University (ISU) method. Linear regression analysis was conducted to identify factors associated with added sugar intake. RESULTS: Average of energy intake (EI) from added sugars was 9.1% (95% CI: 8.9%; 9.4%) among adults and 8.4% (95% CI: 8.2%; 8.7%) among the elderly (p < 0.05). Average added sugar intake (% EI) was higher among women than among men (p < 0.05). Soft drink was the main source of added sugar among adults, while table sugar was the main source of added sugar among the elderly. Added sugar intake increased with age among adults. Moreover, higher socioeconomic level was associated with added sugar intake in the same group. CONCLUSIONS: Added sugar intake is higher among younger adults of higher socioeconomic level. Soft drink and table sugar accounted for more than 50% of the sugar consumed.

Disponibilidade de "açúcares de adição" no Brasil: distribuição, fontes alimentares e tendência temporal

OBJETIVOS: Estimar o consumo de "açúcar de adição" pela população brasileira, nos estratos regionais e socioeconômicos, destacando suas principais fontes alimentares e verificar a tendência do seu consumo nas últimas décadas. MÉTODOS: Contou-se com informações das Pesquisas de Orçamentos Familiares a partir da década de 80 sobre o tipo e a quantidade de alimentos e bebidas adquiridos pelas famílias brasileiras. Os indicadores analisados foram: % das calorias de açúcar no total calórico da dieta e % calórico das frações de açúcar de mesa e de açúcar adicionado aos alimentos pela indústria/kcal açúcar da dieta. RESULTADOS: Em 2002/03, 16,7% das calorias totais eram provenientes de "açúcar de adição" e sua participação mostrou-se elevada em todos os estratos regionais e de renda. A razão açúcar de mesa/açúcar adicionado pela indústria se inverte com o aumento da renda. A participação do açúcar de mesa nos últimos 15 anos foi reduzida, enquanto a contribuição do açúcar adicionado aos alimentos dobrou, especialmente por meio do consumo de refrigerantes e biscoitos. CONCLUSÕES: O consumo de açúcar no Brasil excede largamente a recomendação da OMS e verificou-se importante alteração nas fontes de consumo.