Factors controlling fluxes of volatile sulfur compounds in Sphagnum peatlands

Exchange of DMS and OCS between the surface of Sphagnum peatlands and the atmosphere were measured with dynamic (S-free sweep air) and static enclosures. DMS emission rates determined by both methods were comparable. The dynamic method provided positive OCS flux rates (emission) for measurements performed at sites containing Sphagnum. Conversely, data from the static method indicated that OCS was consumed from the atmosphere. Short and long-term impacts of increased S deposition on fluxes of volatile S compounds (VSCs) from Sphagnum peatlands were investigated in a poor fen (Mire 239) at the Experimental Lakes Area, Ontario, Canada. Additional experiments were conducted in a poor fen (Sallie\u27s Fen) in Barrington, NH, USA. At Mire 239, emissions of VSCs were monitored, before and after acidification, at control and experimental sections within two major physiographic areas of the mire (oligotrophic and minerotrophic). DMS was the predominant VSC released from Mire 239 and varied largely with time and space. Sulfur addition did not affect DMS emissions in a period of hours to a few days. DMS emissions in the experimental oligotrophic area of the mire was $\sim$3-fold greater than in the control oligotrophic area, and $\sim$10-fold greater than in the minerotrophic zones. These differences could be due to a combination of differences in types of vegetation, nutritional status and S input. At Sallie\u27s Fen, DMS fluxes was not significantly affected by sulfate amendments, while DMS and MSH concentrations increased greatly with time in the top 10 cm of the peat column. The major environmental factors controlling fluxes of DMS in a Sphagnum-dominated peatland were investigated in Sallie\u27s Fen, NH. DMS emissions from the surface of the peatland varied greatly over 24 hours and seasonally. Temperature seemed to be the major environmental factor controlling these variabilities. Concentrations of dissolved VSCs varied with time and space throughout the fen. Dissolved DMS, MSH and OCS in the surface of the water table were supersaturated with respect to their concentrations in the atmosphere. Sphagnum mosses did not appear to be a direct source of VSCs, however they increase transport of DMS from the peat surface to the atmosphere

Fluxos de óxido nitroso na interface ar-mar na Baía de Guanabara

In Surface water concentrations of N2O were measured at 37 stations in Guanabara Bay and fluxes estimated across the air-sea interface. Concentrations averaged 8.2 ± 2.2 nmol L-1 and 90% of the stations showed supersaturation averaging 33%. N2O fluxes were estimated using a two-film model which is given by the product of the concentration difference across the film and the gas transfer coefficient (k w). Two parametrizations of k w were used which provided average fluxes of 0.3 and 3.0 µg N m-2 h-1. Flux measurements using floating chambers (not reported here) seem to agree with the upper limit of these estimates

Aporte atmosférico de amônio, nitrato e sulfato em área de floresta ombrófila densa montana na Serra dos Órgãos, RJ

Wet and dry (dust) deposition was measured in the Serra dos Órgãos National Park. VWM pH was 5.3. Non-sea-salt (nss) SO4(2-) comprised 97% of total SO4(2-). The molar ratio [2(nss-SO4(2-)) + NO3-]/[NH4+ + H+] was 1.1, suggesting that pH is predominantly controlled by H2SO4, HNO3, and NH3. Wet deposition of NH4+, NO3-, and nss-SO4(2-) was respectively 0.59, 0.25, and 0.30 kmol ha-1 yr-1. Assuming that dry deposition of N can comprise 30-50% of its total (dry + wet) deposition, the latter is estimated to be 1.2-1.7 kmol ha-1 yr-1 (17-24 kg N ha-1 yr-1)

Avaliação da Contaminação Ambiental por Arsênio e Estudo Epidemiológico da Exposição Humana em Paracatu-MG - Brasil

We present an interdisciplinary study where environmental, social and health conditions are integrated to evaluate the risk of exposure to arsenic in the population of Paracatu, due to the exploitation of the largest open pit gold mine in Brazil. The study had three phases: evaluation of environmental contamination; assessment of human environmental exposure; investigation of factors associated with behavior to reduce the risk of exposure. Water for human consumption in the urban area is not contaminated with arsenic. The levels of arsenic in urine indicate higher exposure in neighborhoods near the mine, in agreement with data on atmospheric particulate matter. The cancer mortality rate was not higher than the controls. Social networks and gender relations are key in the adoption of preventive behaviors. It is recommended the establishment of an Arsenic Exposure Surveillance Program, with the involvement of the Brazilian Universal Health Care System, “SUS”, at the municipal, state and federal levels.Apresentamos um estudo interdisciplinar onde condições ambientais, sociais e de saúde são integradas para avaliar o risco de exposição ao arsênio na população de Paracatu, devido à exploração da maior mina de ouro a céu aberto do Brasil. O estudo possui três fases: avaliação da contaminação ambiental; estudo epidemiológico de exposição ambiental humana; exame dos fatores associados aos comportamentos para reduzir o risco de exposição. As águas de consumo humano na área urbana não estão contaminadas com arsênio. Os teores de arsênio em urina indicam exposição mais alta em bairros próximos à mina, em concordância com os dados sobre material particulado atmosférico. A taxa de mortalidade por câncer não se mostrou superior aos controles. As redes sociais e relações de gênero são chave na adoção de comportamentos preventivos. Recomenda-se o estabelecimento de um Programa de Vigilância da exposição ao arsênio, com envolvimento do SUS, ao nível municipal, estadual e federal

Estimativa do fluxo de amônia na interface ar-mar na Baía de Guanabara: estudo preliminar Estimate of ammonia fluxes at the air-sea interface in the Guanabara Bay: a preliminary study

<abstract language="eng">In the begining of April 2004, concentrations of NHx (NH3 + NH4+) were measured in surface waters of the Guanabara Bay. Concentrations varied from 2 to 143 mmol L-1. Ammonia exchange at the air-sea interface was quantified using a numerical model. No measurement of NH3 concentration in air (c air) was performed. Thus, calculations of NH3 flux were based on the assumptions of c air = 1 and 5 µg m-3. Fluxes were predominantly from the water to the atmosphere and varied from -20 to almost 3500 µg N m-2 h-1

Fluxos de óxido nitroso em solos com cobertura de Floresta Ombrófila Densa Montana na Serra dos Órgãos, Rio de Janeiro

Soil fluxes of N2O were determined over one year in montane tropical rainforest of southeastern Brazil with average annual rainfall of 2.8 m. Annual mean (± standard deviation) and median N2O fluxes were 3.0 ± 1.4 and 2.7 µg N m-2 h-1, respectively, is 5-10 times lower than mean values reported in literature for tropical rainforest soils in the Amazon basin. N2O fluxes varied spatially and seasonally, were about twice as high during summer as in winter, and significantly influenced by both monthly precipitation and soil temperature